To see the other types of publications on this topic, follow the link: Short courses.
Dissertations / Theses on the topic 'Short courses'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Short courses.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Nicholls, Jonathan. "By guess and by God : two short courses on water /." Title page and contents only, 1997. http://web4.library.adelaide.edu.au/theses/09AR/09arn6135.pdf.
Full text
2
Cornwall, Timothy Brooke, and cornwall@inet co th. "Seminar Leader Effectiveness: Teaching Short Courses in the Thai Business Community." RMIT University. Education, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070201.162658.
Full textAbstract:
Research and literature on teaching adults primarily discusses longer courses within the sphere of formal education, that is formal tertiary education and non-formal education (typically work-place or work-related learning). While both these fields provide a rich source of general information, it is difficult to find research texts that specifically deal with teaching adults in a seminar environment, that is, a planned, one-off learning event ranging in length from three hours to two days. While some research has focused on Thai culture in general and the nature of Thai university teaching in particular, very little has been published concerning the teaching of Thai adults, whether in a formal setting such as a university or college, or in a non-formal, work-place or work-related setting. This research reflects an effort to compensate for this pronounced lack of research in teaching adults in a short course environment and the paucity of research on teaching Thai adults. Using a case-study method, fifteen Western or Western-educated Thai trainers in the Thai short-course market were interviewed to determine the characteristics of an effective short-course trainer instructing courses in English. Based on a semi-structured interview format, with questions framed from the literature review, eight key characteristics were determined that reflect the qualities of an effective trainer in the Thai market. Centered on the vital role played by trainers' knowledge of the participants and their culture, the characteristics identified by the research highlight the need to foreground key aspects of participant culture when planning and presenting a short course in the Thai business community. While content expertise and teaching skills remain important, the key to effectiveness lies in acquiring and skillfully applying a knowledge of participants that goes beyond needs analysis to include a generic knowledge of the social norms that identify Thais as a cultural group throughout the training process. The eight characteristics are discussed in detail, and while some aspects of these are consistent with the conventional wisdom discussed in the literature review, most arose from the analyses of comments provided by the interviewees. This discussion leads into a number of recommendations for new trainers in this market and concludes with insights into further areas of study that could prove useful in Thai and other cultures, and for educators involved in short- or long-course events.
3
Schachman, Alan. "An examination of current Navy medical professionals management oriented service short courses /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA268522.
Full text
4
Schachman, Alan Jr. "An examination of current Navy medical professionals management oriented service short courses." Thesis, Monterey, California. Naval Postgraduate School, 1993. http://hdl.handle.net/10945/39840.
Full textAbstract:
Approved for public release; distribution is unlimited.This thesis describes and analyzes the Navy's service short courses available to medical professionals. The description covers course content (subjects being taught), describes contact hours (time a class is taught), and evaluates the depth and breadth of content. The information from each course is compared to the needs of a medical treatment facility (MTF) manager, as determined by the Naval Postgraduate School 'Needs Assessment'. This examination shows that many Navy medical professional service short courses cover parts of the knowledge and skills needed to manage a medical treatment facility. The courses examined focus mainly on leadership and management skills. In order to more accurately describe and analyze these courses, obtaining more detailed information, observing the courses being taught, and interviewing course instructors is recommended.
5
Jones, Kirsten. "Do university work-based learning short courses widen access to higher education and powerful knowledge?" Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/100742/.
Full textAbstract:
With Welsh Government and European Structural Fund (ESF) support, Welsh universities have been incentivised to engage regional employers in ‘upskilling’ working adults and encourage non-traditional routes into higher education. Participating universities have provided short accredited courses through work-based learning projects in subject areas identified as having skills deficits. Such instrumental curricula brought with them the need for tailored pedagogies and assessment strategies to support the achievement of higher education credits for these non-traditional university students. It is here that the link to the thesis’ theoretical framing is established. It draws on sociological curriculum theory that distinguishes and assigns power differentials to curriculum and which cautions against an overemphasis on skills-based knowledge within vocational curriculum. The premise is proposed that the knowledge type inherent to these work-based learning courses is very different to mainstream university curriculum and distances itself from theoretical ‘powerful’ knowledge (Young 2008) to the point it becomes powerless. Questions of curriculum equity within higher education are thus raised and considered in view of these courses as a recognised form of widening access to higher education activity. The empirical component of the thesis is qualitative and relates the experiences of work-based learning university lecturers and course participants to curriculum theory and the epistemic access (Morrow 2009) to which course participants were exposed. Twelve semi-structured interviews with university lecturers from three Welsh universities were undertaken along with six focus groups comprising work-based learning course participants. Findings reveal that characteristics associated with both widening access and powerful knowledge were apparent but inconsistent. For many stakeholders, the raison d'etre of the courses was the tangible ‘upskilling’ offered. Such views problematised the accredited higher education component of the courses. Conclusions offer that the approach taken by individual course participants and the lecturers’ pedagogic practice were key determinants in how courses were delivered, received and the extent to which powerful knowledge could be identified. This individual orientation similarly determined the potential for these courses to be transformative educational experiences.
6
Reitsma, Gerda Marié. "'n Model vir die kortkursus-indiensopleiding van onderwysers vir die leerarea Tegnologie / Gerda Marié Reitsma." Thesis, North-West University, 2006. http://hdl.handle.net/10394/1200.
Full textAbstract:
The term technology indicates the process where knowledge, skills and
resources are applied to identify human problems and needs and to solve it
through analysis, planning, manufacturing, implementation and evaluation.
Technology education of the learner is important because it becomes necessary
for all people to become technological literate to be able to solve problems, to
understand and use technology responsibly and to show appreciation for the
interaction between man, technology and the environment.
Technology is a relative new learning area that was implemented in the
curriculum of the Intermediate and Senior phase. The problem is that educators,
who received training before the implementation of this learning area, are not
specifically trained for this learning area. These educators are specialized in
other subject disciplines than the one needed for the teaching of technology. It is
important for educators to have adequate subject knowledge and skills, as well
as subject specific pedagogical knowledge and skills to teach the subject
effectively. Qualified educators can be retrained in a new subject field by
attending in-service training courses.
In-service training in the South-African school system is currently uncoordinated.
is done in an ad-hoc way and is not regarded as part of the professional
development of educators. It is especially short courses that show shortcomings
with regard to the needs of the educators, time available and form of training.
Educators who do attend in-service courses experienced problems to implement
the new knowledge and skills in the school situation, due to a lack of support.
The need for a comprehensive short course model based on the specific needs
of learning area technology teachers was identified. A situation analyses where
learning area technology subject advisors as well as the learning area technology
teachers were involved, were done, after which a model was presented. The
model is based on four variables, namely context, process, strategy and
structure, and content. These four variables determine the further development
of the model and influence the outcomes, design, implementation, evaluation and
closing. Central to the model is the reflection that is integrated with each phase
of the model. Through critical reflection problems in each phase can be identified
in time after which the necessary adaptations could be made. This will contribute
in making sure that training is still done according to the specific participants
needs and that it is done as effectively as possible.Thesis (Ph.D. (Education))--North-West University, Potchefstroom Campus, 2006.
7
Neto, Ticiane Silveira. "Formação continuada de professores de química: uma análise sobre o entendimento e aceitação das atividades propostas em cursos de curta duração." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/81/81132/tde-27042015-163717/.
Full textAbstract:
Este trabalho é resultado de uma pesquisa realizada com professores de Química do ensino médio de escolas públicas e particulares participantes de dois cursos de formação continuada realizados por uma Universidade de São Paulo, o primeiro curso ocorreu em julho 2011 e o segundo em janeiro de 2012. Sendo assim, nosso campo de pesquisa é a formação continuada de professores de Química, mais especificamente, cursos de curta duração, como, por exemplo, os cursos estudados nessa pesquisa que ocorreram no período de aproximadamente uma semana. O nosso foco principal foi pesquisar como os professores estão entendendo e aceitando as atividades que lhes são propostas nesses cursos com a possibilidade de serem aproveitadas no cotidiano da escola. Foram instrumentos dessa pesquisa entrevistas, gravações de áudio e matérias produzidos pelos professores. O tratamento dos dados se constituiu através da observação, análise e criação de categorias de análise a posteriori. Trabalhamos nesse sentido a fim de construir um instrumento de análise que nos permitisse extrair de maneira mais coesa e estruturada as intenções contidas nos dados coletados tanto sobre professores, como sobre os formadores e o contexto vivido por ambos. Os resultados nos mostram que para que as atividades dos cursos sejam utilizadas em sala de aula é preciso que o professor primeiro as entenda, ou seja, que se sintam seguros quanto ao domínio do conteúdo que as envolve; depois que as aceite, pois o sujeito poderá entende a atividade, mas não aceita-la no sentido de acreditar que seu uso poderá resolver alguns dos seus problemas de ensino e aprendizagem. Os cursos de curta duração parecem não oferecem tempo suficiente para que os processos de entendimento e aceitação se concretizem, mas são importantes à medida que apresentam alternativas, motivam, mostram caminhos de como, porque, onde e quando usar determinada atividade. Caberá a esse professor, caso se interesse pelo assunto, se aprofundar através de estudos individuais ou buscar outros cursos mais longos e específicos.This work is the result of a survey taken with Chemistry teachers of high school participants from two public and private schools continuing education courses conducted by a UNIVERSITY of São Paulo, the first course took place in July 2011 and the second in January 2012. Thus, our research field is the continuing education of Chemistry teachersof chemistry, more specifically, short courses, for example courses studied here occurred in the period of approximately one week. Our main focus was to investigate how teachers are understanding and accepting the activities presented to them in these courses with the possibility of being exploited in the school routine. The instruments of this study were interviews, audio recordings and other materials produced by teachers. Data treatment consisted of observation, analysis, and creation of empirical categories retrospectively. We worked towards this direction in order to build an analytical tool that would allow us to extract in a more cohesive and structured manner the intentions contained in the collected data both on teachers and on those trainers and the context experienced by both. Results show that so the activities of the courses are used in the classroom, it is necessary that the teacher first understand them, or make them feel safe about their domain over the content involved; after accepting them, the subject can understand the activity, but not accept it in the sense of believing that their use might solve some of their teaching and learning problems. Short courses do not seem to offer enough time so that the processes of understanding and acceptance materialize, but are important as they present alternatives, motivate, show ways of how, why, where and when to use some particular activity. It\'s up to this teacher, if they are interested in the subject, delving through individual study or pursue other longer and specific courses.
8
Welch, Alisa Eve. "Short Stories." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/811.
Full textAbstract:
In these six intertwining fictional short stories, one fateful decision ripples through the lives of multiple generations. Annie is an unmarried young mother during World War II when she leaves her young daughter in the care of a childless couple. When Annie fails to return for the child after days and then years, a new and fragile family is formed only to be tested by Annie's eventual return. The other stories in this collection follow the daughters and granddaughters who have to navigate their own lives in the shadow of this abandonment. Spanning multiple decades, Annie's decision remains a pivotal psychological scar imprinted in her descendants and those left to care for the child that she could not.
9
Merriman, Ryan. "We Rode Alone, Of Course: A Collection of Short Stories." Cleveland State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=csu1588689884957891.
Full text
10
Wootten, David F. "Short Term Time Course Skeletal Responses to High Intensity Physical Exercise." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/27880.
Full textAbstract:
The purpose of this randomized controlled trial was to investigate temporal skeletal responses to short-term high intensity physical activity. Twenty-eight normal active females [age: 20.7 +/- 2.1 yr (mean +/- SD)] were randomized into exercise (EX, n = 15) or control (CN, n = 13) groups. The exercise group trained 6 days/wk for 6 wk, which consisted of maximal isokinetic knee flexion/extension 3 days/wk, combined with 3 days/wk running. The purpose was to expose the tibiae to a period of abruptly increased loading forces. Tibial bending stiffness (EIMRTA), and serum concentrations of biochemical markers of bone formation [osteocalcin (OC)], and bone resorption [n-telopeptide of type I collagen (NTx)] were measured at baseline, 2 wks, 4 wks, and 6 wks. Isokinetic concentric knee extension/flexion peak torque, as well as total body and site-specific bone mineral density (BMD) were measured at baseline and 6 wk. After training, the exercise group significantly increased (p < 0.05) isokinetic concentric peak torque for the dominant (13.6%) and non-dominant (5.7%) quadriceps, as well as dominant (7.7%) and non-dominant (9.5%) hamstrings, compared to the controls. No differences for total body or site-specific BMD were noted. A two-way multivariate repeated measures ANOVA revealed no timeâ ¢group interactions for composite tibial bending stiffness [(EIMRTA); p = 0.57] or the biochemical markers of bone turnover [(OC and NTx); p = 0.15] across the four sampling periods. While there were no main effects for group, a trend for time (p = 0.051) for composite EIMRTA was observed. The exercise group demonstrated a 20% increase in EIMRTA from baseline (74.8 +/- 22.3 Nm2) to 6 wk (89.8 +/- 24 Nm2), compared to controls who demonstrated a 4% increase (Baseline 86.5 +/- 23.8 Nm2; 6 wk 90 +/- 23.7 Nm2). Significant group differences (p = 0.05) were noted for OC, but not NTx. Differences (p < 0.05) for OC were observed at baseline [13.2 +/- 2.4 ng/ml (CN), 15.6 +/- 2.7 ng/ml (EX)], and follow-up ANCOVA revealed no differences for subsequent sampling periods. Main effects for time were found for OC and NTx (p < 0.001). Main effects for time in OC were attributable to changes in the exercise group (p < 0.01) and NTx (p < 0.01), but not the control group.Ph. D.
11
Mackenzie, Ian. "An investigation into short course accreditation through the South African Qualification Authority." Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1003482.
Full textAbstract:
This research project offers an analysis of the Adult Basic Education and Training Directorate in the Eastern Cape Province. The Bush Models are described and critiqued and then used as a tool for analysis. Other organisational models are described and used to add depth to the analysis. The choice of analysing the Adult Basic Education and Training Directorate comes both from a professional desire to know and understand this organisation more fully, as well as the importance of stressing that the definition of education organisations does not stop at school, colleges and universities, but includes the government bodies which are a key part of the sector. This assignment therefore explores both the features of a government department as well as the appropriateness of using Bush’s models in this context and draws on other organisational theory--Introduction.
12
Hari, Bahadur Kunwar Boonyong Keiwkarnka. "Factors related patient compliance with "Directly Observed Treatment Short Course" in Pokhara urban Kaski, Nepal /." Abstract, 2005. http://mulinet3.li.mahidol.ac.th/thesis/2548/cd376/4737958.pdf.
Full text
13
Hoa, Nguyen Phuong. "Tuberculosis control in Vietnam : directly observed treatment, short-course (DOTS) - the role of information and education /." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-088-5/.
Full text
14
De, Villiers Adele. "The development, implementation and evaluation of a short course in Objective Structured Clinical Examination (OSCE) skills." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6697.
Full textAbstract:
Thesis (MPhil)--University of Stellenbosch, 2011.Introduction: Objective Structured Clinical Examination (OSCE) examiner training is widely employed to address some of the reliability and validity issues that accompany the use of this assessment tool. An OSCE skills course was developed and implemented at the Stellenbosch Faculty of Health Sciences and the influence thereof on participants (clinicians) was evaluated. Method: Participants attended the OSCE skills course which included theoretical sessions concerning topics such as standard-setting, examiner influence and assessment instruments, as well as two staged OSCEs, one at the beginning and the other at the end of the course. During the latter, each participant examined a student role-player performing a technical skill while being video recorded. Participants‟ behaviour and assessment results from the two OSCEs were evaluated, as well as the feedback from participants regarding the course and group interviews with student role players. Results: There was a significant improvement in inter-rater reliability as well as a slight decrease in inappropriate examiner behaviour, such as teaching and prompting during assessment of students. Furthermore, overall feedback from participants and perceptions of student role-players was positive. Discussion: In this study, examiner conduct and inter-rater reliability was positively influenced by the following interventions: examiner briefing; involvement of examiners in constructing assessment instruments as well as viewing (on DVD) and reflection, by examiners, of their assessment behaviour. Conclusion: This study proposes that the development and implementation of an OSCE skills course is a worthwhile endeavour in improving validity and reliability of the OSCE as an assessment tool.
15
Mwansa, Judith RM. "An evaluation of the effectiveness of a service provider short course to prevent Fetal Alcohol Syndrome." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/9404.
Full textAbstract:
Includes bibliographical references.Background: The Western Cape Province of South Africa has the highest reported rates of Foetal Alcohol Syndrome (FAS) in the world. Reported statistics on FAS in this province show that 40.5 to 46.4 per 1000 children aged 5 to 9 years have FAS compared to developed nations that reported 0.5 to 2 cases per 1000 births. The loss in human potential is immeasurable and various studies have shown that the financial cost is formidable. Each child affected by FAS may require an estimated $1 million to $2 million over the course of their lifetime to support remedial medical, educational and social costs. Primary prevention programmes targeted to women at risk of alcohol-exposed pregnancies could lead to measurable reductions in the incidence of FAS. An alcohol-exposed pregnancy (AEP) is a pregnancy that results when a sexually active woman is not on effective contraception and is involved in risky drinking. Aim: To evaluate the effectiveness of a training intervention to improve screening, identification and management of women at risk of alcohol exposed pregnancies.
16
Hardy, Donald E. (Donald Edward). "Politeness as a Conversational Strategy in Three Hemingway Short Stories." Thesis, North Texas State University, 1985. https://digital.library.unt.edu/ark:/67531/metadc503982/.
Full textAbstract:
Hemingway's dialogue and the texts of politeness and literature -- Brown and Levinson's politeness strategies -- The face of honesty in "The Doctor and the Doctor's Wife -- The face of bravery in "The Short Happy Life of Francis Macomber" -- The face of love in "Hills Like White Elephants" -- Interpretive implications of politeness theory.
17
Hopf, Frances Clementi. "The Impact of a Short-Term Review Treatment Program on Student Success in a College Algebra Course." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3153.
Full textAbstract:
ABSTRACT
The main purpose of this study was to investigate whether conducting a short-term online review of college algebra prerequisite skills at the start of a college algebra course concurrently with the normal course instruction and assignments would have a significant influence on student success. When failure rates in an entry-level college course such as college algebra can range from 20% to 60% or higher, it could present problems for the student and the institution (Burd & Boser, 2009). Research indicates that students who cannot pass entry-level college math courses have decreased chances of obtaining a college degree and it can limit the students' course of study (Adelman, 1999; Thiel, Peterman, & Brown, 2008). While several factors have been found to influence college algebra success, such as instructional practices, students' attitudes toward mathematics, and level of math anxiety, a secondary purpose of this study investigated whether students' gender and number of prior attempts at taking a college algebra course were factors that might interact with student performance.
A quantitative study was conducted in the researcher's college algebra class at the University of South Florida in the fall semester 2010. The design included a treatment group and control group; participants in both were given a pretest and posttest before and after the 4-week treatment period, and all participants took the required departmental final exam. Of the original 187 participants in the study, the final statistical analyses were computed using data from the 165 students who completed the pretest, posttest, and final exam. Participants who were randomly assigned to the treatment group received an online review of college algebra prerequisite skills using the program, MyMathTest (Pearson Education, n.d.b), which included interactive instruction and practice with a minimum requirement of 3 hours per week for the 4-week treatment period; participants who were randomly assigned to the control group received an alternative assignment based upon their college algebra coursework using the online program, MyLabsPlus (Pearson Education, n.d.a) that accompanied the class textbook, with a comparable weekly time requirement. After the four-week treatment period, the remaining 11 weeks consisted of the normal course of study and concluded with a comprehensive departmental final exam not prepared by the course instructor.
No significant differences in achievement on the final exam were found between the two groups. Also, there were no interaction effects and no main effects for gender and performance on the final exam. Number of prior attempts at college algebra similarly had no impact upon final exam. However, student achievement in the researcher's class was observed to be higher than that found in the other college algebra classes in the department (i.e. the researcher's students performed higher on the departmental final exam and had a lower failure rate than the overall departmental failure rate).
The fact the researcher's college algebra students had greater success when compared to the other college algebra students would suggest other possibilities for future regard. For example, studies comparing use of alternative instructional strategies and/or grading practices may reveal factors that influence college algebra performance. Investigations comparing alternative placement procedures and/or advising strategies might also contribute findings helpful to promoting student success in college algebra.
18
Collier, Henrietta Elizabeth. "A study of tuberculosis patients' compliance with short course chemotherapy under routine programme conditions in Sierra Leone." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357428.
Full text
19
Geneve, Michael Louis. "THE SCIENCE AND ART OF A COMMUNITY DEVELOPMENT SHORT COURSE: AN APPROACH TO DESIGN, TEACHING, AND EVALUATION." Lexington, Ky. : [University of Kentucky Libraries], 2008. http://hdl.handle.net/10225/975.
Full textAbstract:
Thesis (M.S.)--University of Kentucky, 2008.Title from document title page (viewed Feb. 3, 2009). Document formatted into pages; contains: viii, 233 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 227-232).
20
Harrison, David B. "Experiential learning modules for developing intercultural competency skills a short-term course for new missionaries from Asia /." Theological Research Exchange Network (TREN), 1996. http://www.tren.com.
Full text
21
Garcia, Hope F. "Exploring Student Learning on a Short-term, Faculty-led Study Abroad Course Through a Student Development Lens." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822773/.
Full textAbstract:
Embarking on a study abroad experience is thought to be a transformational experience for students, and previous researchers have tended to find that the potential benefits of study abroad experiences, including greater conceptual and behavioral intercultural competence, are greater with longer periods abroad. The purpose of this study was to create an intentional learning experience for students who embarked on a short-term study abroad in rural areas of China and to apply faculty intervention of a student development approach to student learning to create a high-impact learning environment for students centered on a service-learning project. This qualitative study gathered primary data from students and instructors during the course through a collection of observation and field notes, student journals, pre- and post-construct tests, and final presentation. Follow-up interviews were conducted 10 months after course completion. Six students participated in this course and study who were from a variety of disciplines and classifications. Five students were female; one was male. Four students were undergraduates; two were graduate students. Student ethnicities included three Caucasians and African American, along with two international students from Mexico and Iran. Key outcomes of this study were that when short-term study abroad faculty members applied creative interventions, students were transformed with regard to their beliefs, perspectives, and behaviors and that when they guided students through a process of reflection and analysis, students exhibited exponential personal development. In addition, the ability to challenge or support students in reaching higher levels of personal development is a privilege that faculty must earn over time and through an authentic demonstration of care for students’ wellbeing. Short-term study abroad faculty members can use the results of this study to maximize the developmental impact of such programs on student participants.
22
Barelli, Elise. "On the security of short McEliece keys from algebraic andalgebraic geometry codes with automorphisms." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX095/document.
Full textAbstract:
En 1978, McEliece introduit un schéma de chiffrement à clé publique issu de la théorie des codes correcteurs d’erreurs. L’idée du schéma de McEliece est d’utiliser un code correcteur dont lastructure est masquée, rendant le décodage de ce code difficile pour toute personne ne connaissant pas cette structure. Le principal défaut de ce schéma est la taille de la clé publique. Dans ce contexte, on se propose d'étudier l'utilisation de codes dont on connaît une représentation compacte, en particulier le cas de codes quais-cyclique ou quasi-dyadique. Les deux familles de codes qui nous intéressent dans cette thèse sont: la famille des codes alternants et celle des sous--codes sur un sous--corps de codes géométriques. En faisant agir un automorphisme $sigma$ sur le support et le multiplier des codes alternants, on saitqu'il est possible de construire des codes alternants quasi-cycliques. On se propose alors d'estimer la sécurité de tels codes à l'aide du textit{code invariant}. Ce sous--code du code public est constitué des mots du code strictement invariant par l'automorphisme $sigma$. On montre ici que la sécurité des codes alternants quasi-cyclique se réduit à la sécurité du code invariant. Cela est aussi valable pour les sous—codes sur un sous--corps de codes géométriques quasi-cycliques. Ce résultat nous permet de proposer une analyse de la sécurité de codes quasi-cycliques construit sur la courbe Hermitienne. En utilisant cette analyse nous proposons des clés compactes pour la schéma de McEliece utilisant des sous-codes sur un sous-corps de codes géométriques construits sur la courbe Hermitienne. Le cas des codes alternants quasi-dyadiques est aussi en partie étudié. En utilisant le code invariant, ainsi que le textit{produit de Schur}et le textit{conducteur} de deux codes, nous avons pu mettre en évidence une attaque sur le schéma de McEliece utilisant des codes alternants quasi-dyadique de degré $2$. Cette attaque s'applique notamment au schéma proposé dans la soumission DAGS, proposé dans le contexte de l'appel du NIST pour la cryptographie post-quantiqueIn 1978, McEliece introduce a new public key encryption scheme coming from errors correcting codes theory. The idea is to use an error correcting code whose structure would be hidden, making it impossible to decode a message for anyone who do not know a specific decoding algorithm for the chosen code. The McEliece scheme has some advantages, encryption and decryption are very fast and it is a good candidate for public-key cryptography in the context of quantum computer. The main constraint is that the public key is too large compared to other actual public-key cryptosystems. In this context, we propose to study the using of some quasi-cyclic or quasi-dyadic codes. In this thesis, the two families of interest are: the family of alternant codes and the family of subfield subcode of algebraic geometry codes. We can construct quasi-cyclic alternant codes using an automorphism which acts on the support and the multiplier of the code. In order to estimate the securtiy of these QC codes we study the em{invariant code}. This invariant code is a smaller code derived from the public key. Actually the invariant code is exactly the subcode of code words fixed by the automorphism $sigma$. We show that it is possible to reduce the key-recovery problem on the original quasi-cyclic code to the same problem on the invariant code. This is also true in the case of QC algebraic geometry codes. This result permits us to propose a security analysis of QC codes coming from the Hermitian curve. Moreover, we propose compact key for the McEliece scheme using subfield subcode of AG codes on the Hermitian curve. The case of quasi-dyadic alternant code is also studied. Using the invariant code, with the em{Schur product} and the em{conductor} of two codes, we show weaknesses on the scheme using QD alternant codes with extension degree 2. In the case of the submission DAGS, proposed in the context of NIST competition, an attack exploiting these weakness permits to recover the secret key in few minutes for some proposed parameters
23
Drame, Abdoulaye. "Synthèse et caractérisation de tensioactifs et polymères hautement fluorés à faible potentiel bioaccumulant." Thesis, Nice, 2014. http://www.theses.fr/2014NICE4068.
Full textAbstract:
A la lumière de la bioaccumulation potentielle relative à la longueur de la chaîne fluorocarbonée, la duplication en chaines courtes constitue une technique intéressante dans la conception de nouveaux matériaux à très faible potentiel de biopersistance. Ainsi, nous avons utilisé cette méthode pour préparer de nouveaux matériaux tensioactifs et polymères conçus avec des chaînes courtes fluorées et évaluer l’influence des paramètres structuraux sur les propriétés physico chimiques de ces composés. L’évaluation des propriétés de surface des tensioactifs ont donné d’intéressantes valeurs aussi bien pour la tension de surface !!!! que pour la concentration micellaire critique (CMC) et la densité moléculaire adsorbée (Amin). La comparaison des propriétés de surface a permis de montrer, que les tensioactifs bicaténaires avec deux chaînes courtes fluorées C4F9 ou C6F13 peuvent égaler, voire dépasser les performances d’un monocaténaire à chaîne longue C8F17 réputé bioaccumulant. Deux populations d’agrégats ont été mises en évidence par la technique de la diffusion de la lumière en mode dynamique (DLS) et par microscopie électronique à transmission (TEM). Des monomères contenant deux segments fluorés ont été synthétisés. Les polymères correspondants ont ensuite été déposés par électropolymérisation et les propriétés de surface des films ont été étudiées. Des films superhydrophobes et oléophobes ont été obtenus avec le polymère PEDOT-2C4,4 à chaînes courtes du fait de nanoparticules uniformément réparties à la surface. Les performances des matériaux conçus avec deux chaînes courtes fluorées ouvrent des perspectives dans la lutte contre la bioaccumulation avérée des longues chaînes perfluoréesIn the light of the potential bioaccumulation relative to the length of the fluorocarbon chain, duplication short chains is an interesting technique in the design of new materials with very low biopersistance. Thus, we used this method to prepare novel surfactants and polymeric materials designed with fluorinated short chains and assess the influence of structural parameters on the physicochemical properties of these compounds. The evaluation of surface properties of surfactants gave interesting values for both surface tension !!!!, critical micelle concentration (CMC) and the molecular density adsorbed (Amin). Comparison of surface properties have shown that double-tailed short chains surfactants with two fluorinated C4F9 or C6F13 can match or exceed the performance of a single-tailed long chain C8F17 deemed bioaccumulant. These surfactants gave two aggregate populations identified by the technique of dynamic light scattering (DLS) and TEM images (transmission electron microscopy). Fluorinated monomers containing two segments were synthesized. The corresponding polymers were then deposited by electropolymerization and the films were studied. Oleophobic and superhydrophobic films were obtained with the PEDOT-2C4,4 polymer short chains because nanoparticles uniformly distributed on its surface. Performance materials designed with two short chain fluorinated open perspectives in the context of the fight against bioaccumulation proven long perfluorinated chains
24
Burgarella, Boris. "Comportement visco-élastique effectif d'un thermoplastique thermostable renforcé par des fibres courtes." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0004.
Full textAbstract:
Le secteur des transports aéronautiques, navals et terrestres fait de plus en plus appel pour les pièces d'habitacles ou de structure à des composites techniques de type thermoplastique thermostable renforcé par des fibres courtes. Ces matériaux alliant légèreté et résistance présentent l’intérêt majeur d’une meilleure recyclabilité d’une facilité de mise en œuvre et de maintenance que les matrices thermodurcissables dans les composites classiques. Toutefois, le développement de modèles de comportement dans le but de dimensionner des structures reste un véritable challenge. L’objectif de cette thèse concerne la modélisation du comportement de ce type de composite soumis à des chargements monotone et cyclique. Une étude expérimental a permis la détermination du comportement de chacun des constituants du composite. Leur comportement a ensuite été utilisé dans un calcul d'homogénéisation en champs complet basé sur une méthode FFT. Le comportement du composite est ensuite modélisé à l'aide d'un modèle visco-élastique spectral. Finalement, l'évolution des paramètres de ce modèle est étudiée en faisant varier la microstructure du composite (taux de fibre, dispersion d'orientation) afin d'établir un méta-modèle permettant de prédire le comportement du composite rapidement, et efficacementTransportation industries uses more and more composite materials each year. These composite materials provide a good alternative to classic materials thanks to their good specific resistances and stiffness. Short fiber composite materials and well suited for automotive applications, thanks to their ability to be used in injection process inducing very short fabrication cycles. But, the modeling of the behavior of these materials remains a challenge to this day. In this PhD work, an experimental characterization of a PEEK / short glass fiber composite has been conducted. A precise study of the PEEK behaior have also been conducted. The PEEK behavior was then used in an full field homogenization method based on FFT to obtain an effective behavior of the composite. A visco-elastic model was then used to model its behavior. Finally, a meta-model is build to accelerate the modeling process by studying the variation of the composite behavior with its microstructure parameters
25
Panupong, Pudthasa Kitti Shiyalap. "Performance of health center personnel on directly observed treatment short, course strategy (DOTS) in controlling tuberculosis, Udonthani province, Thailand /." Abstract, 2003. http://mulinet3.li.mahidol.ac.th/thesis/2546/4537467.pdf.
Full text
26
Peureux, Charles. "Observation et modélisation des propriétés directionnelles des ondes de gravité courtes." Thesis, Brest, 2017. http://www.theses.fr/2017BRES0091/document.
Full textAbstract:
Les vagues courtes sont omniprésentes à la surface des océans, avec des longueurs de quelques dizaines de mètres au mètre typiquement. Connaitre leurs directions de propagation en mer est important à plusieurs titres, notamment pour la compréhension de la dynamique de l'état de mer, des échanges air-mer ou de la dérive de particules en surface. Ces distributions directionnelles sont étudiées ici au regard des progrès récents réalisés en techniques d'instrumentation. L'analyse du bruit sismo-acoustique enregistré en grandes profondeurs permet d'extraire un comportement quasi-universel qui dépend indirectement de cette distribution à travers ladite intégrale de recouvrement. Il est cohérent avec des observations directes du champ de vagues obtenues à partir de reconstructions tridimensionnelles de la surface de l'océan. Alors que la direction de propagation des vagues longues s'aligne avec celle du vent, les vagues courtes s'en détachent d'autant plus à mesure que leurs échelles diminuent (bimodalité).La comparaison de ces observations avec les prédictions d'un modèle numérique de vagues, basé sur l'environnement WAVEWATCH®III, permet de constater que ces modèles sont qualitativement valables mais encore quantitativement incorrects. Une des possibilités explorées pour corriger cet effet est la prise en compte de sources de vagues courtes à ±90° de la direction du vent, qui pourraient être associées au déferlement des vagues longues. Une telle source à elle seule n'explique pas les formes des distributions directionnelles observées. D'autres mécanismes pourraient intervenir que de futures investigations pourront tenter de clarifierShort surface gravity waves are ubiquitous at the ocean surface, with lengths from a few tens of meters to a meter typically.Knowing their propagation directions at sea is important in several respects, especially for the understanding of sea-state dynamics, airsea interactions and particles surface drift.Their directional distributions are here investigated in the light of the recent progress made in instrumentation techniques. The analysis of ocean bottom seismo-acoustic noise records allows for the extraction of a quasi-universal behavior which indirectly depends on this distribution through the socalled overlap integral. It is coherent with direct observations of the wave field obtained from tri-dimensional reconstructions of the ocean surface elevation field. While the propagation direction of long waves aligns with the wind direction, short waves progressively detach from it towards small scales (bimodality).Comparing those measurements with the predictions of a spectral numerical wave model, based on WAVEWATCH®III environment, allows to realize that they provide qualitatively correct but quantitatively incorrect predictions. One of the possibilities here explored to correct for it, is by accounting for the sources of energy at ±90° to the wind direction, which could be associated with the breaking of long waves. This source term on its own does not explain the shapes of the observed directional distributions. Other mechanisms could come into play that future investigations will help clarify
27
Fazzolari-Pleace, Kristin E. "The Impact of Depakote on Agitation and Short-Term Memory in Nursing Home Dementia Residents." ScholarWorks, 2018. https://scholarworks.waldenu.edu/dissertations/4785.
Full textAbstract:
Researchers have linked dementia to common psychiatric symptoms such as agitation and aggression, known as behavioral and psychological symptoms of dementia (BPSD). To treat residents manifesting BPSD, nursing homes (NHs) use psychoactive medications. However, research is limited and inconsistent regarding the impact of Depakote treatment on agitation and short-term memory (STM) in NH residents who have dementia. The purpose of this nonexperimental quantitative study was to evaluate for 1 year the impact of Depakote treatment on agitation and STM in NH residents as measured by each resident's Minimum Data Set (MDS). Moncrieff and Cohen's drug-centered theory served as the theoretical foundation for the study. Archival data from the consulting pharmacist and NH MDS included 16 NH dementia residents. Data were analyzed using a repeated-measures within-subject ANOVA. Results indicated no significant impact of Depakote treatment on agitation and STM scores over a 1-year period. Results may be used to assess the impact and efficacy of a common yet largely unexamined invasive treatment on an underserved, vulnerable population.
28
Nciri, Mariem. "Modélisation du comportement des composites à fibres courtes non-alignées en dynamique." Thesis, Valenciennes, 2017. http://www.theses.fr/2017VALE0016/document.
Full textAbstract:
L’utilisation de composites à matrice thermoplastique renforcée par fibres courtes (TRFC) connait une forte croissance pour une large gamme d’applications industrielles pour des conditions de chargement extrêmes (e.g. pare-chocs d’automobiles). Il est donc indispensable de développer des modèles de comportement des TRFC tenant compte des spécificités du matériau pour une large gamme de vitesse de déformation. Toutefois, le comportement de ces composites est complexe. Cette complexité est due, en premier lieu, au comportement viscoélastique (VE)-viscoplastique (VP) de la matrice avec une sensibilité à la pression. A cela s’ajoute les caractéristiques complexes du renfort en termes de distributions d’orientation des fibres courtes. De plus, le comportement de ces composites est affecté par des phénomènes d’endommagement coexistants (e.g. endommagement de la matrice et décohésion l’interface fibre/matrice). Dans ce travail, un modèle permettant la prise en compte de l’ensemble de ces phénomènes est proposé. Sa formulation est basée sur la décomposition du matériau en un milieu matriciel et plusieurs milieux de fibres, sur la base d’une décomposition additive du potentiel thermodynamique. Cette approche permet une implémentation simplifiée avec une résolution successive (mais non indépendante) du comportement de chaque milieu. Un avantage immédiat est la possibilité de prendre en compte tout type de comportement matriciel et tout type d’orientation. L’interface fibre/matrice, siège de la transmission de l’effort est modélisée par un transfert par cisaillement, avec sur une hypothèse locale d’iso-déformation dans la direction de la fibre. L’endommagement ductile de la matrice est pris en compte par un modèle d’endommagement anisotrope. La dégradation de l’interface fibre/matrice est décrite par un modèle de décohésion initiée en pointe de fibres. Un critère de rupture se basant sur le taux maximal de vide crée par décohésion est enfin introduit. La caractérisation du modèle est basée sur des campagnes d’essais quasi-statiques et dynamiques pour le cas de polypropylène pur et renforcé par fibres courtes de verre, à différents angles de chargement par rapport à la direction d’injection. Ces essais sont complétés par des observations au microtomographe permettant la caractérisation des distributions d’orientation locale des fibres. Des observations au MEB ont enfin permis de constater une éventuelle influence de la vitesse de sollicitation sur les mécanismes d’endommagementShort fibre-reinforced composites are commonly used in a variety of engineering applications, including automotive and aerospace industry. Today, their use is progressively extended to parts possibly subjected to severe loading conditions (e.g. crash...), characterised by high strain rates. Therefore, an efficient modelling that takes into account material’s specificities at a large strain rate range is needed. A constitutive model of viscous behaviour of short-fibre reinforced composites (SFRC) where complex distributions of fibre orientations are taken into account is proposed in this work. The approach considered for the computation of composite macroscopic behavior is based on an additive decomposition of the state potential. The SFRC is assimilated to an assembly of several fibre media embedded in a polymeric matrix medium. One of the main assets of this approach is the possibility to model reinforcement with complex distributions of fibre orientations. Moreover, this decomposition allows the implementation of complex behaviour laws coupled with damage models. The polymeric matrix behaviour is typically strain-rate sensitive, i.e. viscoelastic-viscoplastic. This property has to be taken into account when the modelling of the composite behaviour over a large range of strain rate is intended. Therefore, a viscoelastic constitutive model, based on generalised Maxwell model, and a viscoplastic correction scheme, based on an overstress approach, are implemented for matrix material. The developed constitutive model is then coupled to two damage laws. The first one is introduced in the framework of Continuum Damage Mechanics in order to model the anisotropic ductile damage behaviour of the matrix material. The second one deals with fibre/matrix interfacial degradation through an interfacial debonding law. In order to identify the parameters involved in the present model, experimental tests are performed (case of polypropylene reinforced with short glass fibres). Microcomputed tomography is used for the characterisation of the fibres distribution of orientation. The efficiency of the proposed model is demonstrated by comparisons between numerical and experimental responses in different loading conditions, including dynamic loadings
29
Nepolo, Ester Ndahekelekwa. "Effects of treatment compliance on treatment outcomes for pulmonary tuberculosis patients on Directly Observed Treatment-short Course in Windhoek District, Namibia." University of the Western Cape, 2016. http://hdl.handle.net/11394/4908.
Full textAbstract:
Magister Public Health - MPHTuberculosis (TB) is a major health problem worldwide, with an estimated 9 million new cases accounting for an estimated 1.5 million deaths in 2012. Non-compliance with TB treatment has become a major barrier to achieving global TB control targets. Namibia is one of the worst affected countries in Africa with a high case notification rate (CNR) of all forms of TB and relatively low treatment success rate compared to the WHO targets. The study aimed at investigating TB treatment compliance and measuring its association to patient characteristics and treatment outcomes, in determining the effects of compliance on treatment outcomes in Windhoek District. This information is crucial for TB programme management and development of targeted strategies. A quantitative observational analytic study using a retrospective cohort design was adopted. New adult Pulmonary Tuberculosis (PTB) patients treated under DOTS in Windhoek District between 1st January 2013 and 31st December 2013 were included in the study based on specified criteria. Data was collected from the patients TB treatment cards using an extraction tool. Selection and information bias was eliminated by using clearly defined inclusion and exclusion criteria using a pre-tested standardised tool. Statistical analysis using descriptive and analytic statistics was done using Epi Info 7 to determine compliance, treatment outcomes and to measure the associations. Overall treatment compliance (89%), initial phase compliance (97.2%) and continuation phase compliance (88.1%) were reported in the study. Age (OR=4.3 95% CI (1.72 – 9.90), p-value=<0.01) and type of area (OR=0.02 95% CI (1.00 – 1.13), p-value=0.05) were associated with compliance in the continuation phase. Overall, type of area (OR=0.03 95% CI (0.00 – 0.91), p-value=0.04) remains associated with treatment compliance. Treatment success is reported among 86.1% of patients. Poor treatment outcomes are associated with non-compliance in the initial phase ( =49.98, p-value=<0.01), continuation phase ( =98.81, p-value=<0.01) and overall ( =110.02, p-value=<0.01). Overall treatment compliance (89%) although higher than expected was lower than the WHO recommended 90% compliance. Very high compliance (97.2%) were reported in the initial phase of treatment whilst compliance was also lower than desired (88.1%) in the continuation phase. Non-compliance recorded in the continuation phase is in agreement with the literature. Age and type of area are associated with compliance as reported in the continuation phase and overall in this study is new contribution of knowledge. The findings suggest that treatment compliance is associated with treatment success in both phases of treatment and overall. Low compliance especially in the continuation phase could lead to poor treatment outcomes such as prolonged infections, relapse, high TB mortality and drug resistance leading to increased programme costs. The study concludes that non-compliance results in poor treatment outcomes highlighting the need for interventions that address compliance in all phases but specifically within the continuation phase and amongst those at risk of having reduced compliance such as those in rural areas and young adult patients aged (15 – 34 years). Recommendations to the District Management Team and TB Programme Managers include: identification of measures that promote treatment compliance; support and monitoring of TB patients’ compliance continuously; strengthening CB-DOT by increasing CB-DOT points and enhancing CB-DOT supporters’ capacity as well as strengthening record keeping as a monitoring tool to increase compliance and improve treatment outcomes.
30
Xiang, Hengyang. "Colloidal nanocrystals applied for short-wave infrared photodetectors with fast response." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS423.
Full textAbstract:
L'infrarouge à ondes courtes (SWIR) désigne généralement les photons dans la plage de longueurs d'onde allant de 1 à 3 micromètres. Les applications dans cette fenêtre de longueur d'onde exploitent divers avantages tels qu’une grande longueur de pénétration dans le tissu biologique, la couverture spectrale pour la vision nocturne atmosphérique et l'énergie d'excitation caractéristique de certains modes de vibration moléculaire. Les photodétecteurs SWIR sont donc les composants technologiques essentiels pour la communication optique, la détection de gaz dans l’environnement, le biodiagnostic et la vision nocturne passive. Les technologies SWIR actuelles reposent principalement sur des semi-conducteurs composés à faible bande interdite, tels que InGaAs, InSb, PbS et HgCdTe. Alors que les photodétecteurs SWIR classiques présentent une excellente détectivité, ils sont coûteux (en raison de la croissance requise par l'épitaxie) et / ou présentent un risque environnemental car impliquant des éléments hautement toxiques. Par conséquent, des efforts continus en matière de recherche et de développement concernant des systèmes de matériaux alternatifs et des méthodes de fabrication permettant d'élargir le champ des applications de la photodétection SWIR sont en cours. Ces dernières années, de nombreux nouveaux matériaux ont été proposés, notamment les nanocristaux de phosphore noir, de graphène, de MoS2 et de PbS colloïdal. Ils sont très prometteurs en termes de fonctionnement à des fréquences de modulation élevées et avec une excellente sensibilité. Cependant, certains inconvénients les éloignent toujours du marché: processus de production difficile (faible reproductibilité), non-adaptabilité à la fabrication à grande échelle, préoccupations de sécurité lors de la production en usine (en raison de l’utilisation d’éléments hautement toxiques). Alternativement, les nanoparticules colloïdales traitées en solution, telles que les nanorods d’or colloïdal (Au NR) et les nanoparticules fonctionnant par up-conversion (UCNP), présentent des caractéristiques intéressantes permettant de surmonter ces inconvénients: capacité de synthèse et de production à grande échelle et à faible coût, haute stabilité, faible toxicité biologique et bonne absorption optique des photons SWIR. Cette thèse a pour objectif d'appliquer ces nanoparticules colloïdales à la fabrication de photodétecteurs SWIR et d’étudiere des possibilités d’application dans le domaine de la photodétection. Quelques photodétecteurs SWIR (Au-NRs / Thermistance, photodétecteur Au-NRs / Pt et photodétecteur UCNPs / Polymers) ont été développés dans ce travail, montrant une sensibilité élevées. De plus, la fabrication de ces dispositifs est un procédé peu coûteux et évolutif vers la production de masse au niveau de la fois à la synthèse des matériaux et de la fabrication des composants, et ouvre une nouvelle voie sur le marché de la prochaine génération de photodétecteursShort-wave infrared (SWIR) typically refers to the photons in the wavelength range from 1 to 3 micrometers. Applications in this wavelength window exploit various advantages such as long penetration length in biological tissue, spectral coverage of the atmospheric nightglow, and the characteristic excitation energy of certain molecular vibration modes. SWIR photodetectors are thus the key technological components to achieve optical communication, environmental gas sensing, biodiagnostics, and passive night vision. Current SWIR technologies mainly rely on low-bandgap compound semiconductors, such as InGaAs, InSb, PbS, and HgCdTe. While classical SWIR photodetectors exhibit excellent detectivity, they are costly (due to epitaxial growth requirement) and/or environment unfriendly involving highly toxic elements. There are, therefore, continuous research and development efforts for alternative material systems and fabrication methods to expand the scope of applications of SWIR photodetection. In recent years, many new materials have been proposed, including black phosphorus, graphene, MoS2, and colloidal PbS nanocrystals. They show great promise in terms of operation at high modulation frequencies or high sensitivity. But some disadvantages still keep them away from the market: rigorous production process (poor reproducibility), non-adaptability to scale-up fabrication, manufactory safety and security concerns (due to the use of highly toxic elements). Alternatively, solution-processed colloidal nanoparticles, such as colloidal gold nanorods (Au NRs) and upconversion nanoparticles (UCNPs), exhibit interesting characteristics possible to overcome these disadvantages: capability of scaling-up synthesis, solution-processability adaptable to low-cost fabrication, high stability, low biological toxicity, and good optical absorption for SWIR photons. This PhD thesis aims to apply these colloidal nanoparticles to fabricate SWIR photodetectors and verifies their possibilities for new generation of photodetection. A few SWIR photodetectors (Au-NRs/Thermistor, Au-NRs/Pt photodetector and UCNPs/Polymers photodetector) were developed in this work, showing high responsivity and sensitivity. In addition, the preparation of these devices is a low-cost and scalable up to mass production process both in the materials synthesis and device fabrication, opening a new and convenient path to the next-generation SWIR photodetectors
31
Jolley, Caitlin. "The Effect of Computer-Based Pronunciation Readings on ESL Learners' Perception and Production of Prosodic Features in a Short-Term ESP Course." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4321.
Full textAbstract:
Recent studies on pronunciation teaching in ESL classrooms have found that the teaching of suprasegmentals, namely stress, pausing, and intonation, has a great effect on improving intelligibility (Derwing, Munro, & Wiebe, 1998; Kang, Rubin, & Pickering, 2010; Morley, 1991). The current project describes the development and implementation of computer-based pronunciation materials used for an English for Specific Purposes (ESP) program. The pronunciation program made use of cued pronunciation readings (CPRs) which used suprasegmentals and were developed for English as a second language (ESL) missionaries at the Provo, Utah, Missionary Training Center (MTC). Because there was no pronunciation program in place at the MTC, instructional materials that focused on prosodic features were greatly needed. Missionaries participated in the program anywhere from three to six weeks. Results from the implementation period revealed that missionaries made medium to large gains in their ability to perceive suprasegmentals after using the practice tasks and small-medium gains in their ability to produce suprasegmentals during this short time period. Recommendations for further development, implementation, and testing of similar materials are made for use with individuals in other ESP settings like these missionaries at the MTC.
32
Meslin, Frédéric. "Propriétés rhéologiques des composites fibres courtes à l'état fondu." Cachan, Ecole normale supérieure, 1997. http://www.theses.fr/1997DENS0020.
Full textAbstract:
Ce travail traite de l'étude des suspensions de particules axisymétriques et rigides dans une matrice fluide. Plus précisément, nous nous sommes intéressés au comportement rhéologique de ces matériaux. Le contexte industriel associe est la mise en forme des thermoplastiques renforces par des fibres courtes. Dans une partie théorique, nous proposons un modèle de comportement, issu d'une approche micromécanique, pour les suspensions de sphéroïdes rigides dans une matrice newtonienne : une loi reliant les contraintes et les taux de déformations macroscopiques, une équation pour décrire le mouvement des particules. Ce modèle de comportement est applicable au cas des solutions en régime semi-dilue. Dans une partie expérimentale, nous proposons d'identifier des paramètres rhéologiques du modèle de comportement. A cet effet, des mesures de viscosité en cisaillement sont présentées, ainsi qu'un nouvel écoulement. Ce dernier écoulement, dit écoulement en croix, doit permettre d'identifier le paramètre rhéologique caractérisant l'anisotropie des suspensions.
33
Prabhudesai, Ashish Govind. "The impact of short-course preoperative radiotherapy, lymph node involvement and immune mechanisms on the outcome of patients with cancer of the rectum." Thesis, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431084.
Full text
34
Guevara, Olivares Miguel. "Disentangling the short white matter connections using a fiber's geometry based dimensional reduction approach." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST053.
Full textAbstract:
L'étude de la substance blanche superficielle (SBS) a souvent été laissée de côté car elle est difficile à accéder et très variable. Des méthodes d'acquisition de meilleure qualité et le développement de nouveaux outils d'analyse ont facilité son étude à partir de l'IRM de diffusion et la tractographie. La connectivité du cortex et son plissement sont fortement liés, en particulier pour les fibres en U qui contournent les sillons. Comme la morphologie des motifs du plissement est spécifique à chaque être humain, la configuration des fibres sous-jacentes devrait l'être aussi. Un pipeline pour démêler les différentes configurations des connexions de la SBS et pour caractériser leur relation avec d'autres structures a été conçu. Une méthode pour définir les faisceaux courts à partir de tractographies a d’abord été élaborée selon une approche hybride, en extrayant les fibres reliant deux régions d'intérêt puis en les regroupant en faisceaux reproductibles d'un sujet à l'autre. Une transformation affine fondée sur l’IRM T1 et une base de données de tractographie déterministe ont été utilisées. Cela a permis de générer un atlas des faisceaux du cerveau entier, utilisé pour segmenter les faisceaux de nouveaux sujets, afin de réaliser des études cliniques sur des connexions spécifiques. Cet atlas a été comparé à deux autres atlas publics afin d'évaluer la reproductibilité des faisceaux. Un grand nombre de faisceaux ont été trouvé similaires entre les trois atlas. La définition des faisceaux de la SBS n’étant pas encore consensuelle, une sur-segmentation peut être néanmoins observée d’un atlas à l’autre. Cependant, une plus grande granularité que celle de ces atlas est souhaitable pour étudier la variabilité de leurs configurations entre les individus. Le niveau de démêlage escompté a été obtenu en utilisant une ISOMAP, un algorithme de réduction de dimension, pour stratifier la population en fonction de la géométrie des fibres locales avant la définition des faisceaux. Pour chaque région étudiée, les fibres contournant un sulcus spécifique ont été ciblées et des ROI ont été sélectionnées en conséquence. Ces régions correspondent aux sillons central, temporal supérieur, cingulaire et au gyrus précentral. La méthode a été appliquée sur les données de tractographie probabiliste de 816/897 sujets de la base HCP. Pour chaque région, les fibres ont été extraites puis utilisées dans le calcul de l’ISOMAP, qui à son tour a été utilisé pour diviser la population en dix groupes. Dans chaque groupe, la méthode d'identification des faisceaux courts a été appliquée, afin d'obtenir des faisceaux reproductibles. Ceux-ci ont ensuite été automatiquement mis en correspondance avec ceux des autres groupes, sur la base d'une distance entre centroïdes. Un principe d'hystérésis a été utilisé pour récupérer certains faisceaux précédemment rejetés. Afin d'identifier les faisceaux à l'origine des différences reflétées par les dimensions de l'ISOMAP, une distance «faisceau à tractogramme» pour chaque paire de sujets a été corrélée à leur position dans l’ISOMAP. Une corrélation élevée a été observée entre les premières dimensions de l’ISOMAP fondée sur les fibres et de celle fondée sur la morphologie des sillons. Les faisceaux contribuant à cette dimension de l’ISOMAP montrent des transitions morphologiques cohérentes, et sont situés dans des zones où le sillon présente également des transitions de forme. De plus, les changements des faisceaux sont également spatialement corrélés aux changements des activations fonctionnelles. Ces résultats prouvent le lien entre le câblage cérébral et le plissement cortical. De plus, ils montrent qu'une délimitation plus fine des faisceaux permet de voir des différences qui, la plupart du temps, sont brouillées en raison du mélange des configurationsThe study of superficial white matter (SWM) has often been left aside, mainly because of its high variability. Higher quality acquisition methods and the development of new analysis tools have facilitated the study of SWM from diffusion MRI and tractography. Brain connectivity and cortical folding pattern must be strongly related, especially for short U-fibers, which circumvent the folds. As the folding patterns morphology is specific to each human being, so should be the underlying fibers configuration. In this work we created a pipeline to disentangle the short white matter connections into their different configurations and to characterize their relation with other structures.First a method to delineate short bundles from a tractography set was built using a hybrid approach, by extracting fibers connecting two cortical regions of interest (ROIs) (incorporating anatomical information) and then clustering them into bundles (considering their shape), reproducible across subjects. Subjects were aligned by a T1-based affine transformation and a deterministic tractography database (79 subjects) was used. This generated a whole brain streamline bundle atlas, which allows distance-based segmentation of the bundles in new subjects, in order to perform clinical studies over specific connections. The bundles obtained were compared against other two publicly available atlases (using alternative non-linear alignment across subjects), to evaluate their reproducibility given different methods and databases. A non-negligible number of bundles were found similar among the three atlases. As SWM bundle definition is still a subjective matter, over-segmentation can nevertheless occur. However, even greater granularity is required when aiming to classify the different bundle configurations. This level of disentanglement was achieved by an ISOMAP dimensionality reduction algorithm. It aimed to stratify the population based on their fibers using geometrical changes across subjects. For each region under study, the fibers surrounding a specific sulcus were targeted and therefore the ROIs were selected accordingly. These regions are: central sulcus, superior temporal sulcus, cingulate sulcus and precentral gyrus. The method was applied over 816/897 subjects of the S900 release of the HCP database and a preprocessed probabilistic tractography database. For each region the fibers were extracted, sampled and then used in the ISOMAP computation, which in turn was employed to split the population in ten groups. In each group a refined version of a short bundle identification method was applied, in order to obtain reproducible bundles. These were then automatically matched with their corresponding ones in the other groups, based on a centroid fiber distance. A Hysteresis principle was used to recover missing bundles (previously discarded) in each group. In order to identify the bundles driving the differences reflected on each ISOMAP dimension, the correlation of the fibers geometry with the subjects ISOMAP values was performed, by using a “bundle to tractogram” distance for each pair of subjects. The fiber-based ISOMAP values were also compared to a sulcus-based ones, obtaining a high correlation for the first dimension. The bundles showing correlation with the ISOMAP values show coherent morphological transitions along the groups, and are located in areas where the sulcus also exhibits differences in shape. Moreover, the bundles are also spatially correlated to changes in functional activations. These results prove the link between the brain wiring and the cortical folding pattern. Moreover, they evidence that a finer delineation of the bundles allow the detection of differences that most of the time are blurred out due to the mixing of configurations
35
Xing, Bin. "Confrontation des aspects statistiques et déterministes de l'amorçage des fissures de fatigue dans les alliages d'aluminium." Châtenay-Malabry, Ecole centrale de Paris, 1998. http://www.theses.fr/1998ECAP0592.
Full textAbstract:
Le travail de cette thèse comprend l'étude du phénomène de la distribution de la durée de vie de fatigue, qui présente deux zones pour l'alliage aluminium des séries 2000 et 7000. De nombreuses éprouvettes sont soumises à des chargements d'amplitude constante. Les résultats d'essais sont analysés par la méthode statistique. Les surfaces de rupture et les surfaces libres des éprouvettes sont observées et analysées pour étudier le mécanisme d'amorçage des fissures. Les fissures courtes sont observées et étudiées avec plusieurs méthodes d'examen améliorées. Enfin, une nouvelle courbe de Wolhler est établie avec tous les résultats d'étude. Avec cette courbe, un moyen de prévision de vie de l'amorçage des fissures est donc trouvé. Il est facile à utiliser dans les cas rencontres usuellement dans le mode aéronautique.
36
Lim, Yi Punnee Pitisuttithum. "Prospective study of the treatment of cryptococcal meningitis in aids patients with short course amphotericin B followed by fluconazole at Bamrasnaradura Hospital, Nonthaburi, Thailand /." Abstract, 2003. http://mulinet3.li.mahidol.ac.th/thesis/2546/4538018.pdf.
Full text
37
Serrano, Abello Leonell. "Caractérisation thermomécanique du comportement en fatigue des thermoplastiques renforcés de fibres de verre courtes." Thesis, Brest, 2015. http://www.theses.fr/2015BRES0052/document.
Full textAbstract:
L’allégement des véhicules est une préoccupation majeure de l’industrie automobile, puisque cela permet de réduire les émissions des gaz à effet de serre, ce qui entraînerait une réduction des impacts de ceux-ci sur l’environnement à l’échelle mondiale. Cette volonté d’allégement des véhicules tout en restant accessible en termes de coûts, a conduit au remplacement des matériaux métalliques par des composites à matrices thermoplastiques pour de nombreuses applications. Le compromis entre la tenue thermomécanique et le coût massique du matériau amène à sélectionner des matrices polyamides renforcées par des fibres de verre courtes, et mises en forme par injection. Cependant, les outils prédictifs du comportement et les critères robustes pour la caractérisation des propriétés en fatigue, manquent encore. Ils sont pourtant indispensables pour la conception de pièces structurelles dans l’industrie automobile. La caractérisation en fatigue des polyamides renforcés de fibres de verre courtes présente de nombreuses difficultés, liées au comportement fortement non linéaire de la matrice dans les conditions de service visées (température et humidité), à la nature composite de ces matériaux, à l’influence du procédé de fabrication (orientation des fibres) et au caractère fortement dissipatif de la matrice thermoplastique (augmentations de température non négligeables lors des chargements cycliques). Un enjeu majeur est de comprendre les liens entre la microstructure, le chargement thermo-(hygro)-mécanique et les propriétés de fatigue (sites d’initiation, scénarios d’évolution, critère de rupture). Le premier objectif de cette thèse est de proposer des protocoles d’analyse permettant de caractériser l’influence de chaque paramètre sur le comportement en fatigue. Par ailleurs, la complexité des pièces industrielles en termes de géométrie et d’orientation des fibres soulève la question de la pertinence des éprouvettes classiques. Le second objectif principal de cette thèse est donc de concevoir des éprouvettes représentatives en terme d’orientation des fibres et d’accidents géométriques des pièces industrielles (appelées éprouvettes de structure) et de valider pour ces cas complexes, les démarches et critères proposés. Pour répondre à ces objectifs, nous souhaitons proposer un protocole basé sur des mesures d’auto-échauffement, qui donnerait accès d’une part aux champs d’énergie dissipée pour les cas hétérogènes investigués et qui offrirait, d’autre part, une opportunité de caractérisation rapide des propriétés en fatigue au travers de critères énergétiquesVehicle weight reduction is a major issue in the automotive industry, because this contributes to reducing global warming emissions, resulting in a reduction of negative environmental impacts at the worldwide scale. To replace heavy metallic materials conventionally used, short fiber reinforced thermoplastics (SFRT) provide today a major opportunity to obtain lightweight automotive parts at a reasonable cost for several applications. The cost and the thermomechanical properties motivate the choice of polyamide matrix reinforced with glass fibers manufactured by injection molding. However, predictive modeling behavior tools and robust fatigue criteria must be identified. Both are needed for the design of structural pieces in the automotive industry. The fatigue design of SFRT components for structural applications in the automotive industry requires an accurate knowledge of several factors because the material features are complex, these features are related to the strong nonlinear behavior of the matrix under the service conditions (temperature and humidity), the composite nature of the material, the influence of the injection molding (fiber orientation) and the dissipative characteristics of the thermoplastic matrix (significant temperature rise during the cyclic loadings). A major issue is to understand the relations between the microstructure, the thermo-hydro-mechanical loading and the fatigue properties (fatigue initiation sites, evolution scenarios, and failure criterion). The first objective of this thesis is to suggest methods that allow for the characterization of the influence of each parameter on the fatigue behavior. Furthermore, the complexity of the industrial pieces in terms of geometry and fiber orientation challenges the relevancy of the classical samples. The second objective of this thesis is consequently to design more complex samples that intend to be representative in terms of fiber orientation and geometric details found in the industrial pieces (called structural samples) and to validate the methods and the fatigue criteria suggested for these complex cases. To achieve these objectives, a method based on thermal measurements giving access to the dissipation fields for the heterogeneous cases considered is proposed, this method also offers a very high reduction of the characterization duration of the fatigue properties through energetic criteria
38
Aiyegoro, Olayinka Ayobami. "Determinants of adherence to tuberculosis therapy among patients receiving Directly Observed Treatment from a district hospital in Pretoria, South Africa." University of the Western Cape, 2016. http://hdl.handle.net/11394/5546.
Full textAbstract:
Magister Public Health - MPHBackground: The incidence of tuberculosis in South Africa last measured at 834 in 2015 as reported by the World Bank. Out of these cases, only 54% cured and 13% of patients stop taking treatment. In Pretoria, Gauteng, comprehensive TB services are available in 87% of clinics and all these clinics offer the Directly Observed Treatment Short-course (DOTS) programme and help to diagnose TB and trace contacts. However, the average Pretoria district DOTS coverage has decreased from 88.8% to 84.7% in the last few years. The health district's cure rate as at 2012 is 61%, and its average rate of successful treatment of all new smear positive cases is 66% since 2005. Certain factors that determine patients' adherence towards TB treatment have been identified to include demographic, psychosocial and health system related factors. However, the WHO identified factors responsible for or predisposing patients to discontinue the DOTS programme have not been investigated in the study setting. Aim: The aim of this study was to assess the determinants of adherence to DOTS therapy amongst TB patients who commenced TB treatment at the TB clinic of a district hospital during April – June 2014. Methodology: A quantitative study was conducted using a descriptive cross-sectional design. An inclusive sample was drawn from adults in the DOTS programme receiving first line treatment during the 6-month period prior to commencement of the research. The calculated sample size was 234 individuals. The data collection tools included a questionnaire, 2-day recall and 30-day recall instruments and pill counts. Data were analysed using EPI info version 7 which included descriptive statistics to measure level of adherence. Associations between identified factors and adherence to TB treatment were also determined. Results: The final sample size was 80 participants of which 76% were male. The mean composite adherence rate was found to be 94% while the proportion of the patients who achieved adherence of 95% and above was 75%. Identified barriers to adherence include forgetfulness, lack of transport fare on clinic appointment days, patients not feeling well and so were not strong enough to attend clinic appointments. On the other hand, the role of treatment supporters and counseling were found to have a positive impact on adherence to DOT in this setting. The use of reminders such as cell phones and alarm-radios were also identified as facilitators to adherence. Patients' knowledge of consequences for not taking medications as prescribed, which is closely linked with counseling, was found to be significantly associated with adherence in this study. Education status of participants was found to be significantly associated with adherence to DOTS (p = 0.01), when considering the pharmacy refill pill count as the adherence measure. Significant association was found between DOTS treatment regimens and 30-day recall adherence measures (p = 0.002). Significant association was also found for medication side effects and the adherence measures of 2-day recall, 30-day recall and pill count with p = 0.04; p = 0.03; p = 0.05 respectively There were significant associations between age and adherence with two of the adherence measures (30-day recall and pill count) at p = 0.002 and p = 0.003 level of significance respectively. Significant association was observed between duration of DOTS treatment when dichotomised using the mean treatment period (17 weeks) as the cut-off point and any of the adherence measures. Conclusion: The factors identified in this study can be classified into patient related factors, economic factors, social factors and health care workers and health system related factors. Furthermore, the factors at these different levels impact on one another and their improvements need to be made at all these levels to address the challenges facing TB patients to achieve optimal treatment adherence. This study is the first study of its kind in the study location and the findings have provided useful baseline data on the adherence rates and some insights into the major factors that affect adherence among patients on DOTS at a Pretoria West District Hospital. However further qualitative and quantitative studies are required to explore the factors influencing adherence further.
39
Niang, Alioune. "Manipulation d’un grand nombre de solitons dissipatifs dans les lasers à fibre." Thesis, Angers, 2014. http://www.theses.fr/2014ANGE0023/document.
Full textAbstract:
Ce travail est consacré à l’étude des interactions d’un grand nombre de solitons dans un laser à fibre dopée erbium/ytterbium. Les impulsions interagissent entre elles et se structurent pour former des distributions plus ou moins organisées. Deux cavités ont été réalisées, l’une basée sur la rotation non-linéaire de la polarisation (RNLP) et l’autre sur le miroir optique à boucle non-linéaire (NOLM) en configuration de laser en forme de huit. Avec la RNLP, nous nous sommes intéressés d’abord à une distribution où les impulsions sont liées (cristal de solitons). Ce cristal, stable pour des puissances moyennes, devient instable lorsque la puissance augmente : il se disloque. Les solitons se réorganisent pour former un régime de verrouillage harmonique (HLM) de 50 cristaux. Nous avons ensuite cherché s’il était possible de contrôler les distributions de solitons par l’injection d’une composante continue externe. Nous avons montré que le HLM peut être forcé par l’injection de cette composante. Nous avons développé deux approches afin de modéliser un laser verrouillé en phase et soumis à l'injection d'une composante continue, l'une est scalaire et l'autre vectorielle. Ces modèles démontrent que le signal injecté peut modifier les interactions entre les solitons. Enfin, le NOLM a permis d’observer plusieurs dynamiques : pluie de solitons, gaz de solitons, liquide de solitons, poly-cristal de solitons, multi-cristal de solitons, cristal de solitons, états liés et verrouillage harmonique d’états liés. Ce laser a permis également d’observer une émission laser continue et impulsionnelle autour de 1600 nmThis work has been devoted to study the interaction of the large number of solitons in the erbium/ytterbium doped fiber laser. The interaction of pulses with each other causes to form more or less organized distribution. Two laser cavities have been constructed, one based on the non-linear polarization rotation (NLPR) and the other based on the nonlinear optical loop mirror (NOLM) in a figure-eight laser configuration. With the NLPR, we were interested to the distribution of coherent pulses (crystal solitons). This crystal, stable for moderate power, becomes unstable at high power, which means to get loose from the initial soliton. These solitons rearrange their relative position to form one harmonic-mode locking regime (HML) of 50 crystals. Afterward, we have investigated the possibility of controlling the solitons distribution by injecting an external continuous wave (cw). It has been observed that cw could force the laser to operate at HLM regime. Moreover, we have developed two theoretical approaches, such as scalar and vectorial, to model the passively mode-locked fiber laser submitted to the cw. Both models confirm that the injected signal could modify the interactions between the solitons. Finally, the NOLM allowed us to observe several dynamics, including rain solitons, gas solitons, liquid solutions, poly-crystal solitons, multi-crystal solitons, crystal solitons, bound states and harmonic-mode locking of bound states. Furthermore, it made possible to observe the continuous as well as pulsed laser emission around 1600 nm
40
Casey, E. (Etain). "Walter Ripman and the University of London Holiday Course in English for Foreign Teachers 1903–1952." Doctoral thesis, Oulun yliopisto, 2017. http://urn.fi/urn:isbn:9789526216133.
Full textAbstract:
Abstract The thesis presents a case-study through which the linguistic purpose and historical and social context of the University of London Holiday Course in English Language for Foreign Teachers, is analysed and interpreted. The study foregrounds the context, content and development of one of the smallest academic units, a four-week short course, to contribute to our understanding of how international students of English language were taught and assessed in a particular university context in the early 20th century. The period from 1903 to 1952 is examined in order to understand why the course was successful and the impact of the work of Walter Ripman (1869-1947) who directed the course until 1939. Ripman is better known as a teacher of German and a significant figure in the German Reform Movement, which originated in 19th century Germany, but his approach to culture, phonetics and vocabulary acquisition in English language teaching and learning is less well known. The study goes beyond a history of his methodology to investigate and critically assess the formula that Ripman developed for the design of the short, university English language course and compares it with a similar course run at University College London by Daniel Jones. The changes that were made to the content and purpose of the course, following Ripman’s retirement in 1939, are examined as to how far they reflected the effects of war and the continued desire to internationalise the University itself by aligning the content of the courses more closely to the University programmes. The nature and importance of the web of relationships between staff in the success and longevity of the course are analysed and in particular the contribution of women to better understand their role in the learned world at that timeTiivistelmä Tässä tapaustutkimuksessa analysoidaan ja tulkitaan Lontoon yliopiston ulkomaisille opettajille suunnatun englannin kielen lomakurssin kielellisiä tavoitteita sekä historiallista ja sosiaalista kontekstia. Tutkimus nostaa tarkastelun kohteeksi yhden pienimmistä akateemisista opintokoko-naisuuksista eli neliviikkoisen lyhytkurssin ja sen kontekstin, sisällön ja kehityksen. Tavoitteena on syventää ymmärrystä siitä, kuinka kansainvälisiä englannin kielen opiskelijoita opetettiin ja arvioitiin tässä yliopistokontekstissa 1903–1952. Tutkimuksen tarkoituksena on selvittää, miksi kurssi oli menestyksekäs ja mikä rooli tässä oli Walter Ripmanilla (1869–1947), joka johti kurssia vuoteen 1939 asti. Ripman tunnetaan saksan kielen opettajana ja tärkeänä hahmona kieltenopetuksen uudistustyössä, joka alkoi 1800-luvulla Saksassa, mutta hänen englannin opetukseen ja oppimiseen liittyvät näkemyksensä kulttuurista, fonetiikasta ja sanaston oppimisesta ovat vähemmän tunnettuja. Tutkimuksessa tarkastellaan Ripmanin metodologian historiaa mutta arvioidaan myös kriittisesti yliopistollisen englannin kielen lyhytkurssin toimintamallia, jota hän kehitti. Mallia verrataan vastaavaan kurssiin, jota Daniel Jones johti Lontoon University Collegessa. Työssä tutkitaan niitä muutoksia, joita tehtiin kurssin sisältöön ja tavoitteisiin sodan jälkeen, kun Ripman oli jo siirtynyt eläkkeelle. Muutoksia tarkastellaan suhteessa yliopiston kansainvälistämispyrki¬myksiin ja toiveisiin suunnata kurssisisältöä yliopiston tutkinto-ohjelmien mukaisesti. Lisäksi tutkimuksessa kiinnitetään huomiota henkilökunnan keskinäisten verkostojen luonteeseen ja merkitykseen kurssin menestykselle ja pitkäikäisyydelle sekä erityisesti naisten panokseen ajan akateemisessa maailmassa
41
Chrétien, Gaëlle. "Etude de la propagation de fissures physiquement courtes dans les alliages de titane pour turbomachines d'hélicoptères à différentes températures." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2017. http://www.theses.fr/2017ESMA0022.
Full textAbstract:
Cette thèse s’inscrit dans le cadre général de l’étude de la tolérance au dommage des pièces tournantes dans les turbomachines d’hélicoptères et porte sur la résistance à la propagation de fissures courtes 2D.Pour mener à bien cette étude, l’effet de la température est d’abord étudié sur les seuils de propagation de fissures longues à R=0,1 sur deux alliages TA6V et Ti6242 de microstructure bimodale (20°C et 400°C pour le TA6V et 20°C, 200°C et 500°C pour le Ti6242). Au voisinage du seuil, le comportement effectif(après correction de la fermeture) est sensiblement identique pour les deux alliages aux températures testées. La fermeture est principalement induite par l’oxyde à haute température et par la rugosité des surfaces de rupture à température ambiante.L’évolution du seuil de propagation en fonction de la longueur de fissure a ensuite été étudiée à R=0,1. Un outil de détermination automatique du niveau de fermeture a été mis en place afin d’améliorer la mesure pour des fissures très courtes (80 μm). La fermeture mesurée pour différentes longueurs de fissure obtenues par usinage progressif du sillage plastique est comparable à celle obtenue au cours de la propagation d’une fissure courte 2D au seuil, sauf pour les hautes températures où la fermeture induite par l’oxyde se développe rapidement. Les différences de comportement entre fissure longue et fissure courte sont expliquées par une contribution réduite de la fermeture lorsque le sillage de la fissure est réduit.Un critère de non-propagation s’inspirant du formalisme initialement proposé par Kitagawa et une loi de propagation adaptée permettent de mieux prédire la résistance à la propagation des fissures physiquement courtesDamage tolerance analyses of rotating parts, containing 2D-short crack, in turbomachines of helicopters is the main focus of this thesis.Fatigue crack propagation tests were performed at R=0.1 on two bimodal Titanium alloys at different temperatures (20°C and 400°C for TA6V and 20°C, 200°C and 500°C for Ti6242). Near-threshold effective behaviors (after crack closure correction) were approximately the same for the two alloys attested temperatures. Crack closure was principally due to oxide layer at high temperatures and to fracture surface roughness at ambient temperature.Then the variations of the crack propagation threshold with crack length was studied at R=0.1 and different temperatures. A numerical tool was developed to automatically detect crack closure level more precisely for, as short as, 80μm cracks. Crack closure levels measured at different crack lengths obtained from progressive machining of the plastic wake were quite similar to the ones obtained during propagation of 2D-short cracks near the threshold, except at high temperatures where oxide-induced crack closure developed rapidly. Differences in behavior of long cracks and short cracks were explained by a reduction of crack closure level when crack wake was not fully developed.A non-propagation criterion based on formalism initially proposed by Kitagawa and a modified-Paris propagation law allow to give a better description of physically 2D-short crack propagation resistance
42
Despringre, Nicolas. "Analyse et modélisation des mécanismes d'endommagement et de déformation en fatigue multiaxiale de matériaux composites : polyamide renforcé par des fibres courtes." Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0058/document.
Full textAbstract:
Le présent travail de thèse se consacre au développement d'un nouveau modèle micromécanique pour les composites en thermoplastique renforcé par des fibres de verre courtes. L'objectif est notamment la modélisation du comportement visco-endommageable en fatigue du PA66-GF30. Ce matériau, particulièrement utilisé dans l'industrie automobile, est sujet à une microstructure spécifique issue du procédé de moulage par injection. L'approche multi-échelles développée consiste en une méthode de Mori-Tanaka modifiée, appliquée à des renforts avec enrobage et prenant en compte l'évolution de l'endommagement à l'échelle microscopique. La description des mécanismes d'endommagement se base sur une investigation expérimentale poussée préalablement menée au sein de l'équipe. Des scénarios d'endommagement ont été proposés et incluent trois processus locaux différents : la décohésion de l'interface, la microfissuration de la matrice et les ruptures de fibres. Ceux-ci sont spécialement affectés par la microstructure. L'approche développée intègre ces cinétiques d'endommagement ainsi que la viscoélasticité non-linéaire de la matrice et la distribution d'orientation des inclusions due au procédé de fabrication. Chaque mécanisme d'endommagement est modélisé par une loi d'évolution basée sur les contraintes locales calculées à l'échelle microscopique. La loi constitutive finale, à l'échelle du volume élémentaire représentatif, est implémentée dans une bibliothèque scientifique en C++, SMART+, et est conçue pour être compatible avec une analyse de structures par éléments finis. L'identification du modèle est réalisée par rétro-ingénierie, en tirant profit de résultats expérimentaux multi-échelles, dont notamment des tests in-situ au MEB ainsi qu'une analyse qualitative et quantitative par μCTThe current work focuses on a new micromechanical high cycle fatigue visco-damage model for short glass fiber reinforced thermoplastic composites, namely: PA66/GF30. This material, extensively used for automotive applications, has a specific microstructure which is induced by the injection process. The multi-scale developed approach is a modified Mori-Tanaka method that includes coated reinforcements and the evolution of micro-scale damage processes. Their description is based on the experimental investigations of damage mechanisms previously performed by the team. Damage chronologies have been proposed involving three different local degradation processes: fiber-matrix interface debonding/coating degradation, matrix microcracking and fiber breakage. Their occurrence strongly depends on the microstructure. The developed model integrates these damage kinetics and accounts for the complex matrix viscoelasticity and the reinforcement orientation distributions induced by the process. Each damage mechanism is introduced through an evolution law involving local stress fields computed at the microscale. The developed constitutive law at the representative volume element scale is implemented into a C++ scientific library, SMART+, and is designed to work with Finite Element Methods. The model identification is performed via reverse engineering, taking advantage of the multiscale experimental results: in-situ SEM tests as well as quantitative and qualitative μCT investigations
43
Maurel, Martin. "Dynamique propagative d’impulsions optiques ultra-courtes pour un module de compression à base de fibre creuse." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0116.
Full textAbstract:
Les lasers de durées ultra-courtes, de l’ordre de la centaine de femtoseconde, sont actuellement des outils incontournables pour bon nombres d’applications industrielles ou académiques. Cependant leurs durées restent limitées par la technologie même de ces dispositifs. Par ailleurs, le développement de nouvelles fibres optiques microstructurées offre un guidage d’impulsions de hautes énergies dans des milieux gazeux permettant de ce fait la génération d’effets non-linéaires moteurs aux dynamiques de compression et de post-compression. Les travaux de cette thèse s’inscrivent donc dans ce contexte. Les études de dynamiques de compression d’impulsions ultra-courtes sont ainsi présentées. Les démonstrations d’auto-compression et de post-compression ont été faites à des longueur d’ondes de 343 nm et 1030 nm pour des régimes d’énergies allant de quelques microjoules à plusieurs centaines de microjoules pour des puissances moyennes jusqu’à 100 W. Des compressions de facteur 29 sont présentées faisant passer des impulsions de 580 fs à 19 fs via une dynamique de compression solitonique. De plus, cette technologie s’est vu intégrée dans une plateforme industrielle installée chez différents clientsUltra-short pulse laser, hundred femtoseconds, are currently an essential tool for many industrial or academic applications. However, their duration remains limited by the technology which composed this device itself. In addition, development of new microstructured optical fibers offers high-energy pulse guidance in gaseous media, thus allowing the generation of non-linear effects, key parameter for pulse compression and post-compression dynamics. The work of this thesis is therefore part of this context. Studies of ultra-short pulse compression dynamics are presented. Self-compression and post-compression are demonstrated at wavelengths ranging from 343 nm to 1030 nm with energy from few microJoules to several hundred microJoules and average power up to 100 W. Factor 29 of compressions are presented, with solitonic dynamic pulse with duration of 580 fs are compressed down to 19 fs. In addition, this technology has been integrated into an industrial platform installed at various customers' sites
44
Hérault-Fournier, Catherine. "La proximité perçue par les consommateurs vis à vis d'un circuit de distribution : conceptualisation et application à la vente directe de produits alimentaires." Thesis, Montpellier, SupAgro, 2014. http://www.theses.fr/2014NSAM0014/document.
Full textAbstract:
La recherche d'une « plus grande proximité » avec le consommateur n'est pas qu'une formule à la mode désignant un phénomène conjoncturel, comme en témoigne l'utilisation récurrente de ce concept dans différents champs des sciences humaines pour analyser les relations interpersonnelles, inter-entreprises ou entre clients et fournisseurs. L'objectif de ce travail doctoral est de spécifier le concept de proximité perçue du point de vue du marketing et d'analyser son rôle dans la gestion de la relation du client au point de vente. Cette recherche, menée, dans le cadre spécifique de la vente directe de produits alimentaires, démontre l'intérêt théorique et managérial du concept de proximité.Une revue de littérature et une étude qualitative par entretiens semi directifs menée auprès de 35 acheteurs, dans différents formats de vente directe de produits alimentaires (AMAP, Marchés et Points de ventes collectifs) permet tout d'abord de démontrer que le concept de proximité perçue est multiforme : 1- la proximité d'accès correspond à la facilité et la praticité perçue qu'a le consommateur pour se rendre sur le point de vente; 2- la proximité relationnelle, exprime la force de la relation directe entre le personnel en contact et le consommateur ; 3- la proximité identitaire, renvoie à un partage de valeurs avec le le point de vente et enfin 4- la proximité de processus, est liée au partage de connaissances sur son fonctionnement interne. Une échelle de mesure de ces formes de proximité est proposée, puis validée.Dans un second temps, l'application empirique de cette échelle de mesure, auprès de 579 acheteurs, dans trois formats de vente directe fournit une mesure effective de la proximité perçue dans ce contexte. Ces études permettent, via un modèle d'équations structurelles, de tester l'impact des différentes formes de proximité sur la confiance, attestant du pouvoir prédictif du concept. Les résultats montrent en effet que la confiance à l'égard du circuit de vente directe est influencée positivement par : la proximité identitaire, la proximité de processus, et la proximité d'accès. En revanche, la proximité relationnelle n'influence pas directement la confiance à l'égard du circuit. Elle y participe néanmoins via son rôle dans la construction des autres formes de proximité.Dans un troisième temps, prenant appui sur ces mêmes enquêtes, nous démontrons le pouvoir discriminant du concept. Tout d'abord vis-à-vis des formats de vente. Les Points de vente collectifs génèrent en effet une proximité identitaire plus forte, accompagnée par une formalisation et une communication plus importantes de leurs valeurs et principes d'action. Les AMAP créent quant à elles davantage de proximité de processus. Proposant à leurs adhérents de participer aux activités de production mais également à l'organisation et la gestion de la distribution, elles renforcent le sentiment de contrôle des consommateurs. Sur les marchés, où la dynamique collective est quasi inexistante et les principes de fonctionnement ni formalisés ni communiqués, les différentes proximités perçues sont significativement plus faibles.Le concept de proximité discrimine également les consommateurs. Une segmentation en fonction de la proximité perçue montre qu'il est possible de distinguer trois types de consommateurs : les intimes, caractérisés par une proximité multiforme (identitaire, relationnelle et de processus), les affiliés qui se sentent proches des valeurs et des manières de travailler mais prennent peu de temps pour échanger et les distants qui ne se sentent proches du point de vente qu'à travers les valeurs qu'il représente.Enfin, une enquête quantitative complémentaire conduite auprès de 1208 clients de boucheries, petits commerces d'alimentation et primeurs nous permet de démontrer la spécificité de la vente directe uniquement en terme de proximité identitaire, remettant en cause l'idée d'une proximité relationnelle plus forte dans ces circuitsThe desire for a "closer relationship" with the consumer is not just a buzzword denoting a conjunctural phenomenon. The recurrent use of this concept in social sciences to analyze interpersonal and inter-enterprise relationships or relationships between customers and suppliers testifies it. This thesis specifies the concept of perceived closeness from the marketing point of view and analyzes its role in the management of customer relationship to the point of sale. Conducted in the specific context of direct selling of food products, this research demonstrates the theoretical and managerial interests of the concept of closeness.A literature review and a qualitative study using semi-directive interviews conducted with 35 customers in different formats of direct sale of food products (CSA, Markets and farm shops) demonstrates that the concept of perceived closeness takes many forms: 1- the access closeness is the ease and convenience perceived by the consumer to go to the point of sale 2- relational closeness expresses the strength of the direct relationship between the salesperson in contact and the consumer 3- identity closeness refers to values shared with the point of sale and finally 4- process closeness is related to the sharing of knowledge about the internal functioning of the point of sale. A measurement-scale of these forms of closeness is given, and then validated.In a second time, the empirical application of this measurement scale, to 579 customers in three formats of direct sales provides an effective measure of perceived closeness in this context. These studies, using a structural equation model, allow to test the impact of different forms of closeness on trust, demonstrating the predictive power of the concept. Results show that trust in the direct point of sale is positively influenced by identity closeness, process closeness and access closeness. However, relational closeness does not directly influence customer trust in the point of sale. It participates to it via its role in the construction of other forms of closeness.In a third part, we demonstrate the discriminative power of the concept. Firstly towards the sales formats. Farm shops generate a stronger identity closeness accompanied by a greater formalization and communication of their values and principles. CSA create for their part greater process closeness. By allowing their members to participate in production but also in the organization and management of the distribution of products, they reinforce the consumer's sense of control. On the markets, where the collective dynamics is almost nonexistent and the principles of operation neither formalized nor communicated, the different forms of perceived closeness are significantly lower.The concept of closeness is also discriminant for consumers. A segmentation according to the perceived closeness shows that it is possible to distinguish three types of consumers: the intimates, characterized by a multifaceted closeness (identity, relational and process), the affiliates who feel close to the values and ways of working but take little time to exchange, and the distants who feel close to the point of sale only through the values it represents.Finally, a complementary quantitative survey of 1208 customers of small food shops, of butcheries, and of fruit and vegetables shops, allows us to demonstrate the specificity of direct sale only in terms of identity closeness, challenging the idea of a stronger relational closeness in these circuits
45
Pawelko, Romain. "Étude des phénomènes thermiques associés à des sollicitations mécaniques à grande vitesse." Thesis, Paris 10, 2018. http://www.theses.fr/2018PA100058/document.
Full textAbstract:
Lorsqu'un matériau est soumis à une sollicitation mécanique rapide, une partie de l'énergie mécanique est convertie en énergie thermique et une autre partie est stockée dans le matériau (energy of cold work). Dans le cas où la vitesse de déformation est très élevée, il peut se produire un phénomène de localisation accompagné d'une élévation importante de la température. Celle-ci peut atteindre localement des valeurs proches de la température de fusion du matériau. Ce phénomène appelé cisaillement adiabatique possède de nombreuses applications : usinage à grande vitesse, balistique, projection cold-spray... L'énergie thermique émise est une valeur observable, elle est utilisée depuis quelques années pour essayer de comprendre les mécanismes d'endommagement. Nous avons mis au point un dispositif capable de mesurer la température dans les bandes de cisaillement. L'utilisation combinée d'une caméra à balayage de fente fonctionnant aux courtes longueurs d'ondes et d'une barrette de 32 détecteurs fonctionnant dans l'infrarouge nous permet de limiter les incertitudes. Un programme d'inversion a été développé afin de caractériser le terme source thermique. Des mesures de température ont aussi été effectuées sur des matériaux énergétiques composites afin de mieux comprendre les mécanismes de réactionWhen a material is subjected to a mechanical loading, part of the energy will be transformed into thermal energy and another part will be stored inside the material énergy of cold work). In the case of a dynamic loading, a localization phenomenon may occur accompanied by a significant rise in temperature which can locally reach values close to the melting point of the material. This phenomenon called adiabatic shear has many applications: high-speed machining, ballistics, cold-spray , blanking... The emitted thermal energy is an observable value which has been used in the past years in order to better understand the failure mechanisms. We have developed a device able to measure the temperature in the shear bands. The combined use of a short-wavelength streak camera and a 32- infrared detectors array allows us to limit uncertainties. An inversion program has also been developed to identify the thermal source term. Temperature measurements were also performed on composite energetic materials to better understand the reaction mechanisms
46
Crevel, Jeremy. "Étude et modélisation du comportement et de l’endommagement d’un composite injecté à matrice PEEK renforcée de fibres courtes de carbone." Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0003/document.
Full textAbstract:
Durant ces dernières décennies les matériaux composites organiques ont subi un très grand essor dans le domaine des structures aéronautiques. Leur principal avantage est d’alléger les structures tout en gardant de bonnes propriétés mécaniques. De plus, leur microstructure leur permet d’avoir un caractère multi-fonctionnel, ce qui facilite leur intégration pour remplacer les technologies existantes. Dans l’industrie aéronautique, il existe un besoin croissant de grande quantité de petite et moyenne pièces (clips, éléments de jonctions). Cependant, il est aujourd’hui difficile de fabriquer en série des pièces ayant des formes tridimensionnelles complexes par des procédés conventionnels (autoclave). Ainsi, l’orientation envisagée est d’utiliser les procédés de la « famille » automobile pour des applications aéronautiques « semi-structurales », comme le moulage par injection de composites thermoplastiques renforcés de fibres courtes. Cette application nécessite une maîtrise et une fiabilisation du procédé ainsi que des propriétés induites. Ceci a été réalisé par l’identification et la quantification des effets des paramètres qui influent significativement sur la microstructure et les propriétés macroscopiques, par un plan d’expériences. De plus, le dimensionnement de telles pièces requiert une modélisation robuste du comportement mécanique pour prédire au mieux leur capacité d’utilisation. Les données sur la microstructure ont permis d’alimenter un modèle micromécanique comportant un critère d’endommagement de l’interface fibre/matrice. Développé sur un code éléments finis industriel, il a permis de prédire les résultats expérimentaux d’une pièce industrielleDuring the last decades, organic composite materials have undergone great development in the field of aeronautical structures. Their main avantage is to reduce the structures weight while maintaining good mechanical properties. In addition, their microstructure allows them to have a multi-fuctional nature, which facilitates their integration to replace existing technologies. In the aviation industry, there is a growing need for large amount of small and medium parts (clips, connecting elements). However, nowadays it is difficult to produce parts with complex by conventional methods dimensional shapes (autoclave). Thus, the considered path is tu use methods of the automotive “family” for “semi-structual” aerospace applications such as injection-moulding of thermoplastic composites reinforced by short fibres. This application requires a mastery and reliability of the process and the induced properties. This was achieved by the identification and quantification of the parameters effects that significantly influence the microstructure and macroscopic properties, by a design of experiments. Moreover, the dimensioning of such parts requires a robust mechanical behabior modelling to predict the best use of their capacity. The data on the microstructure enable to feed a micromechanical model featuring damage criteria of the fiber/matrics interface. Developed on a industrial finite element code, it was used to predict the experimental results of an industrial part
47
Holzer, Verena Leïla. "Does the german renewable energies act fulfil sustainable development objectives? : Paper presented at the Research Workshop & Short Course: Investment in Sustainable Energy, Helsinki, Finland, 28.6. - 1.7.2004." Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2007/1418/.
Full textAbstract:
Table of contens
1 Introduction
2 The concept of sustainability
2.1 Ecological sustainability
2.2 Social sustainability
2.3 Economic sustainability
2.4 The sustainability strategy of the german government
3 Effects of energy use on the enviromment
4 Requirements of the SSGG for energy policy
4.1 Ecological implications of thr SSGG
4.2 Social and economic requirements of the SSGG
5 The German Renewable Energies Act
5.1 Objectives
5.2 Design and mechanisms
5.3 Fees-in tariffs
6 Does the EEG meet the sustainability requirements of the SSGG?
6.1 Management rules
6.2 Social sustainability
6.3 Economic sustainability
6.4 Development tendencis
7 Possible amendments for more sustainability
7.1 Changing the promotional system
7.2 A European regulation
48
Domingos, Mirian Pereira. "Tuberculose em Recife, PE: o efeito da estratégia DOTS (Directly Observed Treatment Short-course) e fatores associados ao óbito e ao abandono de tratamento, 1996 a 2005." Universidade Federal de Minas Gerais, 2007. http://hdl.handle.net/1843/BUOS-9UJGAE.
Full textAbstract:
The abandonment of tuberculosis treatment is considered as the main obstacle to control the disease. The persistence of the infection source, increase in mortality and recurrence rate, besides the development of medicament resistant types are related to abandonment of the treatment. The essential components of tuberculosis control policies have been synthesized into a set, which constitutes the DOTS (Directly Observed Treatment Short-course) strategy, recommended by the WHO. This paper is meant to identify the factors associated with deaths and abandonment of treatment in tuberculosis cases for those living in Recife, PE, before and after the implementation of DOTS. Furthermore, it intends to assess the impact of this strategy on epidemiological and operational indicators of the disease such as incidence coefficient, mortality coefficient, mortality rate and percentage of patients abandoning the treatment. Deaths by TB have been compared to those who have survived in a comparison case research with a single event, involving the cases diagnosed from 1996 to 2004. Observing the situation before death, the patients have been analyzed in another case-comparison with more than one result where the variable responses were: healing, death and abandonment of the treatment. Death by TB and the association HIV-AIDS have been confirmed in the Aids and Mortality system. The census was the base for the population data base. At first, analysis by periods have been carried out; pre-DOTS, diagnosis of 1996-2000 and DOTS, from 2001 to 2005; followed by various analysis of the whole set of information. The occurrence and mortality coefficients accumulated by period for 100,000 inhabitants have been, respectively, 82.3 and 13.7 during the pre-DOTS period and 108.6 and 7.1 during the DOTS period. The mortality rates have been 14.8% and 6.0%. The implementation of the DOTS strategy has reduced the risk of death in 50% (OR=0,5; IC95% 0,40-0,70) whereas the supervised treatment has reduced the likelihood of abandonment of the treatment in 28%. In the pre-DOTS death was associated with (p< 0.05): age when diagnosed (OR=1,04; IC95% 1,03-1,05), previous abandonment of the treatment (OR=3,94; IC95% 2,17-7,15) and mixed clinical form (OR=4,91; IC95% 2,17-11,16); whereas, male gender (OR=1,22; IC95% 1,06-1,41) and previous abandonment of the treatment (OR=3,42; IC95% 2,65-4,41) were associated with abandonment of the treatment. In the DOTS period death was associated with: age when diagnosed (OR=1,04; IC95% 1,021,06) and complications associated with TB (OR=2,36; IC95% 1,224,58); whereas low educational level (OR=1,74; IC95% 1,13-2,67), previous abandonment of the treatment (OR=2,44; IC95% 1,41-4,23) recurrence (OR=1,62; IC95% 1,022,56), any associated complication (OR=1,55; IC95% 1,172,04) or being under supervised treatment (OR=0,73; IC95% 0,570,93) were associated to the abandonment of the treatment. Changes in TB mortality and detection indicators have been observed with the implementation of DOTS strategy in Recife. The detection of cases has been extended and the risk of death reduced with a change in death profile. With regard to the cases of abandonment of the treatment, despite the changes in the patients profiles, the strategy impact as compared to this result was lighter. In the patients included in supervised treatment the likelihood to abandon the treatment was slightly reduced. Previous abandonment of the treatment, mainly for patients without HIV/AIDS, continues to be a relevant fact for the mortality rate and to abandon the treatment, therefore it shall be prioritized for inclusion in supervised treatment. The need for improvement in the assistance to elders and to those with low education and integration with other assistance services to other complication factors are also provided herein.O abandono de tratamento de tuberculose é considerado o principal obstáculo no controle da doença. Persistência da fonte de infecção, aumento da mortalidade e da taxa de recidiva, além do desenvolvimento de cepas resistentes aos fármacos, estão associados ao abandono. Os componentes essenciais das políticas de controle da tuberculose foram sintetizados num pacote que constitui a estratégia DOTS (Directly Observed Treatment Short-course), recomendada pela Organização Mundial de Saúde. Este trabalho objetivou identificar os fatores associados ao óbito e ao abandono de tratamento em casos de tuberculose residentes na cidade do Recife, PE, antes e após a implantação da estratégia DOTS. Ademais, pretende avaliar o impacto dessa estratégia nos indicadores epidemiológicos e operacionais da doença como coeficiente de incidência, coeficiente de mortalidade, taxa de letalidade e percentual de abandono de tratamento. Óbitos por TB de pacientes foram comparados aos que sobreviveram em um estudo tipo caso comparação com apenas um evento, envolvendo os casos diagnosticados nos anos de 1996 a 2004. Observados os preditores do óbito, os pacientes foram analisados em um outro estudo caso-comparação com mais de um desfecho onde as variáveis respostas eram: cura, óbito e abandono de tratamento. Óbito por TB e associação HIV-AIDS foram confirmados no sistema de Mortalidade e de Aids. O censo foi a base de dados populacional. Inicialmente foram feitas análises por períodos; pré-DOTS, diagnósticos de 1996-2000 e DOTS, de 2001-2005; seguidas de análises multivariadas de todo o conjunto de informações. Os coeficientes de incidência e mortalidade acumulados por períodos por 100.000 habitantes foram, respectivamente, de 82,3 e 13,7 no período pré-DOTS e de 108,6 e 7,1 no DOTS. As taxas de letalidade foram de 14,8% e 6,0%. A implementação da estratégia DOTS reduziu a chance de óbito em 50% (OR=0,5; IC95% 0,400,70) e o tratamento supervisionado per si reduziu a chance de abandono em 28%. No período pré-DOTS se associaram ao óbito (p< 0,05): idade no diagnóstico (OR=1,04; IC95% 1,03-1,05), abandono prévio (OR=3,94; IC95% 2,17-7,15) e forma clínica mista (OR=4,91; IC95% 2,1711,16); enquanto que, sexo masculino (OR=1,22; IC95% 1,06-1,41) e abandono prévio (OR=3,42; IC95% 2,65-4,41) estavam associados a abandono de tratamento. No período DOTS estavam associados ao óbito: idade no diagnóstico (OR=1,04; IC95% 1,021,06) e apresentar algum agravo associado à TB (OR=2,36; IC95% 1,224,58); enquanto que, baixa escolaridade (OR=1,74; IC95% 1,13-2,67), abandono de tratamento anterior (OR=2,44; IC95% 1,41-4,23) recidiva (OR=1,62; IC95% 1,022,56), algum agravo associado (OR=1,55; IC95% 1,172,04) e estar sob tratamento supervisionado (OR=0,73; IC95% 0,570,93) estavam associados ao abandono. Mudanças nos indicadores de detecção e mortalidade da TB foram observadas com a implantação da estratégia DOTS em Recife. A detecção de casos foi ampliada e o risco de morrer foi reduzido com modificação no perfil do óbito. No abandono de tratamento, apesar de mudanças no perfil dos pacientes, o impacto da estratégia na proporção desse desfecho foi menor. PAra pacientes incluídos em tratamento supervisionado, a chance de abandonar foi sensivelmente reduzida. Abandono de tratamento anterior, notadamente entre pacientes sem HIV/AIDS, continua sendo relevante na mortalidade e no abandono de tratamento, devendo ser priorizado para inclusão em tratamento supervisionado. Necessidade de melhora na atenção aos idosos e nos de baixa escolaridade e a integração com os serviços de atenção aos outros agravos também são apontadas nesta pesquisa.
49
Brugier, François. "Modèle condensé de plasticité pour la fissuration et influence de la contrainte T." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLN028/document.
Full textAbstract:
Les divers composants d'un réacteur d'avion sont soumis à des chargements de fatigue mécaniques et thermiques fortement variables. Afin de prédire au mieux leurs durées de vie, il est alors nécessaire de prendre en compte l'ensemble de ces variations. Pour ce faire, un modèle représentant de façon incrémentale l'évolution de la plasticité en pointe de fissure a été développé. Celui-ci permet de prédire la vitesse de propagation d'une fissure tout en prenant en compte les effets d'histoire provenant de la plasticité produite lors de surcharges ou de sous-charges. Dans cette étude, ce modèle condensé de plasticité a été exprimé plus simplement à partir du facteur d'intensité des contraintes et l'identification automatisée de ses divers paramètres a été redéveloppée. Dans ce but, un essai de fissuration stable a été conçu pour déterminer simplement le seuil de non-propagation du matériau. Par ailleurs, les éventuelles fissures se propageant dans un composant sont en général amorcées en surface à partir de chocs ou de rayures. Ces fissures passent la majeure partie de leur vie dans un régime de propagation de fissure courte, différant de celui d'une fissure longue. En effet, à facteur d'intensité des contraintes équivalent, une fissure courte se propagera plus rapidement qu'une fissure longue. La prise en compte de ce comportement dans la prédiction de durée de vie est donc primordiale. En outre, il a été observé qu'une fissure longue subissant une contrainte T négative se propage de façon analogue à une fissure courte. Il a donc été choisi de développer un nouveau modèle adapté aux fissures courtes en prenant en compte l'influence de la contrainte T sur la vitesse de propagation. Enfin, à partir des essais de fissuration stable, un protocole a été développé pour réaliser des éprouvettes comportant fissure courte. Une campagne d'essais multiaxiaux pour différentes valeurs de contrainte T a été menée en régime permanent et transitoire afin d'étudier les similitudes entre effet de fissure courte et influence de la contrainte TThe various components of an aircraft engine undergo strong changes in mechanical and thermal fatigue loadings. All these variations must be taken into account in order to anticipate the components' total fatigue life to the best. An incremental model showing the changes in plasticity at the crack tip has therefore been developed. It allows us to foresee the crack growth rate with history effects by modelling the plastic behaviour produced when overloads or underloads occur. In this study, the plasticity condensed model has been represented in an easier way, using the stress intensity factor and the automated identification of its parameters has been redeveloped. A stable crack growth test has been designed to determine easily the fatigue crack growth threshold of the material. Cracks usually grow from scratches or impacts on the surface of the component. These cracks spend much of their fatigue life growing with a short crack behaviour, differing from the long crack one. As a matter of fact, a short crack grows faster than a long crack for a same stress intensity factor. This behaviour must therefore be taken into account while modelling the crack growth to accurately predict the total fatigue life of the component. It appeared furthermore that a long crack undergoing a negative T-stress grows the same way as a short crack. It has consequently been chosen to develop a short crack growth model using the influence of T-stress on the crack growth rate. Finally, using the stable crack growth specimens, an experimental protocol has been designed to produce new specimens containing a short crack. A multiaxial tests campaign was carried out for various values of T-stress in permanent and transitional regimes in order to compare short crack and T-stress effects
50
Achour, Nadia. "Modélisation multi-échelle et analyse expérimentale du comportement de composites à matrice thermoplastique renforcés fibres de verre sous sollicitations dynamiques modérées." Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0062/document.
Full textAbstract:
Le présent travail de thèse a pour objectif de développer un outil de modélisation par transition d’échelles sous forme de machine d’essais virtuels. Celle-ci, utilisée conjointement aux codes de calculs de structures, permet de déterminer le comportement anisotrope complexe de composites à matrice polypropylène chargés en fibres de verre courtes sous sollicitations dynamiques. La microstructure en cœur-peau induite par le procédé d’injection du matériau est investiguée expérimentalement par μCT. Le comportement dynamique est caractérisé pour des vitesses de déformation allant jusqu’à 200s-1 au moyen d’une une méthodologie expérimentale basée sur l’utilisation d’un joint d’amortissement et d’une optimisation des éprouvettes. Les mécanismes d’endommagement sont analysés expérimentalement par essai in situ. Ils mettent en évidence le phénomène d’endommagent prépondérant qui est la décohésion de l’interface fibre matrice. Basé sur ces résultats expérimentaux, l’approche multi échelles développée consiste en une méthode de Mori Tanaka incrémentale appliquée à une matrice élastoviscoplastique et des renforts enrobés intégrant l’évolution de l’endommagement à l’échelle mésoscopique. L’endommagement introduit dans les enrobages perturbe le transfert de charge entre la matrice et les renforts. De plus, la dépendance à la vitesse de déformation, aux orientations et aux taux de fibre du modèle sont corrélés par des essais. La machine d’essais virtuels est validée par modélisation de structures. L’outil prédictif ainsi développé prend en compte le minimum nécessaire à la description de la microstructure tout en étant fiable et pertinent dans la modélisation de composites sous sollicitations dynamiques modéréesThe current work focuses on the development of a micromechanical modeling tool in the form of a virtual test machine which, used with the structural calculation codes, allows to determine the complex anisotropic behavior of polypropylene matrix composites reinforced with short glass fibers under dynamic loading. The core-skin microstructure induced by the material injection process is investigated experimentally by μCT. The dynamic behavior is characterized for strain rates of up to 200s-1 using an experimental methodology based on the use of a damping joint and specimen optimization. The mechanisms of damage are analyzed experimentally by in situ SEM testing. They highlight the importance of the debonding phenomenon in the damage scenario. Based on these experimental results, the multiscale approach developed consists of an incremental Mori Tanaka method applied to an elastoviscoplastic matrix and coated reinforcements integrating the evolution of damage at the mesoscopic scale. The damage introduced into the coatings disturbs the load transfer between the matrix and the reinforcements. In addition, the strain rate, orientation, and fiber rate dependence of the model are correlated by testing. The virtual testing machine is validated by modeling structures. The developed predictive tool thus takes into account the minimum necessary to describe the microstructure while being reliable and relevant in the modeling of composites under moderate dynamic stress