Дисертації: "Period of stability"

1

Koskinen, T. T. "The stability of short-period extrasolar giant planets." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444248/.

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A three-dimensional coupled thermosphere-ionosphere model for extrasolar giant planets (EXOTIM) has been developed. This is the first such model reported in the literature. This thesis contains an extensive description of the model and the methods adopted in modelling the different physical processes expected in the upper atmospheres and ionospheres of extrasolar giant planets. Modelling the upper atmosphere is important because the stability of the atmosphere against thermal evaporation is controlled by the conditions in the thermosphere. The thermosphere is heated by the absorption of EUV and X ray (XUV) radiation emitted by the host star. The radiation also ionises the neutral species in the upper atmosphere, which is expected to be composed mainly of molecular and atomic hydrogen, and atomic helium. Ionisation and subsequent photochemistry leads to the formation of the H+, Hf, H3", and He+ ions (and small quantities of HeH+). H3" emits strongly in the infrared and may act as a significant coolant in gas giant thermospheres. Assuming photochemical equilibrium, the absorption of XUV radiation and ion photochemistry were modelled in a self-consistent fashion. The 3D model can also simulate strong winds affecting the upper atmosphere, and account for both advection and diffusion of the neutral species around the planet. The results indicate that within 1.0 AU from a solar-type host star, the upper atmospheres of Jupiter-type EGPs can be substantially cooler and more stable than implied by studies that ignore the possibility of radiative (Hf) cooling. In this context, a limiting distance, or a stability limit, was identified for such EGPs that depends on the composition of the upper atmosphere and ionosphere, and within which the atmospheres of the planets undergo hydrodynamic escape. Under restricted conditions, this limit is located around 0.15 AU from a Sun-like host star. The model was also used to simulate a newly found transiting planet HD17156b, which orbits its host star on a highly eccentric orbit.

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2

Němečková, Lenka. "Hodnocení stability vybraných rostlinných olejů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2010. http://www.nusl.cz/ntk/nusl-216588.

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This diploma thesis is focused on issues concerning the stability of selected vegetable oils which are used in cosmetic industry. The stability of eight oils without additives were determined by a differential scanning calorimeter. In the first phase, the temperatures of oil degradation were determined for different rates of heating, i.e. nonisothermal stabilities. They were consequetly used to calculate isothermal stabilities alias induction periods. The calculation of induction periods was completed by using integral isoconversional methods, which applied four different temperature functions. One of the temperature functions corresponded to Arrhenius equation while the others to non-Arrhenius functions. The confrontation of induction periods under standart conditions showed that an optimal temperature function to calculate oil stabilities is one of the non-Arrhenius functions in exponential form. We can state that all oils are degraded by similar, if not the same, mechanism. The specified stabilities, in periods of months, have proved the importance of using stabilizers and other additives in the commercial and technological use of vegetable oils.

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3

Viman, Olof. "Stability and Change in Personality in Adult Women Over a 37-Year Period." Thesis, Örebro universitet, Institutionen för juridik, psykologi och socialt arbete, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-23889.

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AbstractThe present study aims to examine mean-level, rank-order, and individual-level change in personality in two population-based samples of women. Participants were followed over 37 years from mid-life to old age, including two cohorts aged 38 to 75 years and 46 to 83 years. Participants completed the Cesarec-Marke Personality Schedule – a self-report measure of Murray’s psychogenic needs – in 1968 and 2005. Mean levels of need for affiliation, order, nurturance, and succorance increased whereas need for dominance, aggression, and defense of status decreased, but effect sizes were generally small and test-retest correlations were generally strong, suggesting personality stability. By contrast, significant changes were observed at the individual level, with participants both increasing and decreasing in most psychogenic needs. Eighty five percent (85%) of the participants changed significantly in at least one psychogenic need.
SammanfattningDenna studie undersöker medelvärdes-, rangordnings- och individuell förädring av personlighet i två urval av kvinnor. Deltagarna följdes över 37 år; den ena kohorten från 38 år till 75 år och den andra från 46 år till 83 år. Deltagarna besvarade Cesarec-Marke personlighetsformulär – ett självskattningsmått av personlighet utifrån Murrays psykogena behov – 1968 och 2005. Medelvärdet ökade för behov av tillhörighet, att ha ordning, att bli omhändertagen samt att ta hand om andra. Medelvärdet minskade för behov av att leda/dominera, att hämnas/retas samt känslighet för andras åsikter/att undvika misstag. Effektstyrkan var generellt liten, och korrelationskoefficienterna mellan baslinje och uppföljning var generellt höga vilket tyder på personlighetsstabilitet. Å andra sidan sågs signifikanta förändringar på individnivå, med deltagare som både ökade och minskade signifikant på de flesta psykogena behov. Åttiofem procent (85%) av deltagarna förändrades signifikant på minst ett psykogent behov.

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4

Liu, Jingjing. "Identification and Regulatory Role of E3 Ligases in the Time-Dependent Degradation of the Circadian Factor Period 2." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/81179.

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Circadian rhythms are self-sustained, 24h, biological oscillatory processes that are present in organisms ranging from bacteria to human. Circadian rhythms, which can be synchronized by external cues, are important for organisms to adjust their behavior, physiological activity, and metabolic reactions to changes in environmental conditions. Another well-established oscillatory mechanism that shares common organizational and regulatory features with the circadian system, is the cell division cycle. Recent findings reveal that some essential regulators are common to both the cell cycle and the circadian clock. The first half of my thesis (Chapter 2-3) focuses on the function of Period 2 (Per2), a key regulatory component of the negative feedback arm of the clock and tumor suppressor protein, as a modulator of cell cycle response. We found that Per2 binds the C-terminus end of the tumor suppressor p53 thus forming a trimeric complex with p53's negative regulator Mdm2 and preventing Mdm2-mediated p53's ubiquitination and degradation. Thus, Per2 stabilizes p53 under unstressed conditions allowing for basal levels of the protein to exist and be available for a rapid response to take place in case of any stressed signals. Our experiments prove that Per2 plays an indispensible role in p53 signaling pathway. The second half of my thesis (Chapter 4-5) focuses on how Mdm2 and Per2 interplay regulate Per2 availability and its impact on circadian clock function. My research found that Mdm2 targets Per2 for ubiquitination as Mdm2 depletion stabilizes Per2 and, conversely, Mdm2 ectopic expression shorten Per2's half-life. Accordingly, association of Per2 to Mdm2 maps C-terminus of the p53 binding region in Mdm2 and thus, the RING domain remains accessible. Next, we tested the hypothesis that Mdm2-dependent ubiquitination of Per2 directly impacts circadian clock period length. Accordingly, addition of sempervirine nitrate (SN), a specific molecular inhibitor of Mdm2, to MEF cells abrogated Per2 ubiquitination leading to the accumulation of a stable pool of Per2. By recording the oscillatory behavior of the Per2:Luc reporter system in MEF cells treated with SN at different circadian times, we found that inhibition of Mdm2 E3 ligase activity promoted phase advance only when treatment took place during the degradation period. This is in agreement with our findings that radiation, but not light pulses, causes the same phase behavior. Considering the established role of both Mdm2 and p53 in the response of cells to genotoxic stress and Per2 in modulating the clock, the existence of the Mdm2-Per2-p53 complex opens the possibility of various stimuli triggering regulatory mechanisms converging in a critical node. Overall, our work provides a holistic view of how signals are integrated at multiple levels to ensure that environmental signals are sense and responses triggered timely.
Ph. D.

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5

Herö, Johan. "The effects on knee angular velocity after a 6-weeks training period with the new training device ProPrioPlate- a pilot study." Thesis, Högskolan i Halmstad, Biomekanik och biomedicin, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-25040.

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AbstractBackground: ACL injuries is common and can result in long term disability or even have a career ending outcome for the athlete. Women are more exposed to ACL injuries than men are and several factors increase the risk of ACL injuries for women where one is the knee angle velocity. It seems that prevention programs involving plyometric- and strength training has been most effective on altering these risk factors for knee injuries. But many programs involve several exercises which makes it very time consuming. Since the gluteus muscles is our main hip abductor and hip stabilizer it is of great importance for controlling the knee. The ProPrioPlate (PPP) is a device that has been validated and shown to activate the gluteus medius 40% more in a squat compared to a regular bodyweight squat.Purpose: To investigate if a 6 week long training period, 3 sessions/ week, 5minutes/session with the PPP could decrease the mean abduction angular velocity (°/sec) of the knee joint in a Drop jump (DJ) in women with poor knee stabilityMethod: An experimental study design was used. Twelve female athletes with poor knee stability and signs of knee valgus in a drop jump conducted a 6 weeks training program to investigate any changes in abduction angular velocity in a DJ. 3D motion analyzes were performed before and after the training period. Wilcoxon signed ranked test was used to investigate if there were any changes in results between the different test occasions.Results: Median abduction angular velocity of the test performed before the intervention was -34. 34 (min -70. 65 max -11. 53) deg/sec and after the intervention median -34. 22 deg/sec (min -51. 97 max -3. 28). The P value was 0.24 which indicate that there were no statistical significant differences between the three testing occasions. Compliance to the intervention was low, 15%.Conclusion: A 6 weeks training period with the PPP did not decrease the abduction angular velocity. Due to low compliance rate amongst of subjects no conclusion regarding the effect of the device can be made.
Abstrakt:Bakgrund: Svenska ligament registret rapporterar ungefär 5000 främre korsbandsskador (ACL) årligen i Sverige. ACL skador kan resultera i långvarig frånvaro från sporten eller till och med att idrottaren inte längre kan fortsätta sin karriär. Kvinnor är mer utsatta för ACL skador än män och det är flera faktorer som ökar risken för ACL skador hos kvinnor. Forskningen pekar mot att träningsprogram som syftar till att minska risken för knäskador innefattar styrketräning och plyometrisk träning. Många träningsprogram för att minska risken för knäskador innefattar många övningar vilket gör det tidskrävande. ProPrioPlate (PPP) är ett träningsredskap som är validerat och har visats aktivera gluteus medius 40% mer i en knäböj på PPP jämfört med vanliga knäböj.Syftet med denna studie var att undersöka knätabduktionshastighet i ett dropp vertikalhopp innan och efter ett 6 veckors träningsprogram med PPP för kvinnor med bristande knästabilitet.Metod: En exprementell studiedesign har använts. Tjugo frivilliga kvinnliga idrottar med bristande knästabilitet och teckan på valgus vid dropjump genomförde ett 6 veckors träningsprogram för att undersöka om knäabduktionshastighet i ett dropp vertikalhopp förändrades efter träningsperioden. 3D analyser på testpersonerna genomfördes innan och efter träningsperioden. Wilcoxons signed ranked test användes för att undersöka skillnader mellan de olika test tillfällena.Resultat: Medianen av abduktionshastigheten före interventionen var -47,88 grader/sek (min -74,76 max -30.16), -34.34 (min -70.65 max -11.53) och efter interventionen -34.22 (min -51.97 max -3.28) grader/sek. P värdet var 0.24 vilket indikerar att det inte fanns någon signifikant skillnad mellan före- och eftertesterna. Följsamheten till träningen hos deltagarna var låg (15%).Slutsats: En 6 veckors träningsperiod med PPP minskade inte abduktionshastigheten i ett DJ. Låg åtföljnad av våra testpersoner till träningsperioden innebar att inga slutsatser gällande PPP kan utgöras.

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6

Cronje, Frans Johannes Cornelius. "Beyond the high road : a scenario analysis of the prospects for political stability or instability in South Africa over the period to 2024 / Frans Johannes Cornelius Cronje." Thesis, North-West University, 2013. http://hdl.handle.net/10394/9687.

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Despite the widely hailed success of South Africa’s transition from apartheid to democracy it was apparent by the mid-2000s that beneath the veneer of stability lay a country facing serious social and economic challenges. The employment and labour market participation rates were uniquely low among emerging markets. Protest action against the state had reached levels last encountered in the volatile 1980s and early 1990s. The budget and current account deficits had reached unsustainable levels. By its own admission the government realised that the country was not recording GDP growth rates necessary to make dramatic inroads into poverty, unemployment and inequality levels. A number of analysts and commentators therefore came to question the future stability of South Africa’s political system. Trade unions and some Cabinet ministers routinely described unemployment as a “ticking time bomb”. The Chairman of the Institute of International Affairs wrote in Business Day that he could predict when South Africa’s “Tunisia Day” would arrive. The respected Economist newspaper ran a front page feature on what it called South Africa’s “downhill slide”. Former President FW de Klerk warned that South Africa was approaching a precipice. Clem Sunter, South Africa’s most renowned scenario planner, upped his prospects that South Africa may become a failed state. Global ratings agencies downgraded South Africa citing the fear that government policy could not meet popular demands. Amidst such speculation it is vitally important that the prospects for instability be investigated and determined, not via opinion or speculation, but rather against a sound body of theory. This task is complicated by the fact that the feared instability may only occur at a point in the future. The theory must therefore be applied via a methodology capable of overcoming the weak track record of political science in accurately anticipating major shifts in political systems. This problem statement will be addressed by showing that complex systems theory holds the key to a series of units of analysis via which the stability or instability of any political system can be objectively determined, compared to any other political system, and tracked over time. Secondly that there are scenario planning methodologies that can overcome the uncertainty inherent in the futures of all complex systems and thereby the poor track record that political scientists have in anticipating dramatic future changes in the systems they study. When combined into a single complex systems/scenario model, these theoretical and methodological points of departure will allow the long term prospects for stability or instability of any political system to be accurately and objectively determined.
PhD (Development and Management) North-West University, Potchefstroom Campus, 2013

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7

Foster, Tyler Michael. "Dynamic Stability and Handling Qualities of Small Unmanned-Aerial-Vehicles UNMANNED-AERIAL-VEHICLES." BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/219.

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General aircraft dynamic stability theory was used to predict the natural frequencies, damping ratios and time constants of the dynamic modes for three specific small UAVs with wingspans on the scale from 0.6 meters to 1.2 meters. Using USAF DatCom methods, a spreadsheet program for predicting the dynamic stability and handling qualities of small UAVs was created for use in the design stage of new small UAV concept development. This program was verified by inputting data for a Cessna-182, and by then comparing the program output with that of a similar program developed by DAR Corporation. Predictions with acceptable errors were made for all of the dynamic modes except for the spiral mode. The design tool was also used to verify and develop dynamic stability and handling qualities design guidelines for small UAV designers. Using this design tool, it was observed that small UAVs tend to exhibit higher natural frequencies of oscillation for all of the dynamic modes. Comparing the program outputs with military handling qualities specifications, the small UAVs at standard configurations fell outside the range of acceptable handling qualities for short-period mode natural frequency, even though multiple test pilots rated the flying qualities as acceptable. Using dynamic scaling methods to adjust the current military standards for the short period mode, a new scale was proposed specifically for small UAVs. This scale was verified by conducting flight tests of three small UAVs at various configurations until poor handling qualities were observed. These transitions were observed to occur at approximately the boundary predicted by the new, adjusted scale.

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8

Nhandara, Simbarashe. "The Operational Code of Tony Blair : Did he experience Learning, Stability or Change in his Belief System during the period he was Prime Minister?" Thesis, Södertörns högskola, Institutionen för samhällsvetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-30510.

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The intention of this project is to examine whether or not; Anthony Charles Lynton "Tony" Blair, experienced any belief changes or learning, during the period he was Prime Minister of the United Kingdom (UK), a period which lasted 10 years commencing 1997 until 2007. Our analysis will cover a timeline beginning from 1999 a point in time when the UK participated in NATO’s Operation Allied Force during the Kosovo War until 2006 when Britain took on the reins of the EU presidency for a six-month period. An exploration, of the beliefs behind a leader’s decision making logic, should always be considered a prudent undertaking especially when it comes to foreign policy studies. This is because, it is only through such activity scholars can comprehend the distinction between decisions and actions. Thus, understanding when and how; an individual leaders’ belief system changes, is of central importance in furthering our ability in explaining not only state behaviour, but, also the relationship between ‘self’ and ‘other’. The main purpose of an operational code analysis is to enable political scientists and policy makers alike, to deduce from a particular leader’s verbal content, what that actor's beliefs are and the premises they take in relation to their decision-making process. The first of our two part hypotheses seeks to determine whether Tony Blair exhibited changes in his beliefs at various stages of his premiership. These stages were signified by events which were also crucial in defining his political legacy. The events are divided into three categories, Post Kosovo – Pre Iraq, Pre 9/11 – Post 9/11 and Pre EU – Post EU. On completion of our VICS and SPSS analysis on Tony Blair’s operational code belief we discovered that there were no statistically significant changes in any of his operational indices. So, due to the lack of statistically significant changes in Blair’s Philosophical and Instrumental indices we could not classify the events selected for this analysis as having produced any influence on his belief system. Thus we rejected our null hypothesis and accept the alternative hypothesis.

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Puntriano, Rosas César Alfredo. "Legal Consequences Derived from the Violation of Exit Labor Stability by the Employer." Derecho & Sociedad, 2017. http://repositorio.pucp.edu.pe/index/handle/123456789/118330.

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After a conceptual overview of the scope of the right to job stability, its relationship with other rights (right to work, right to access to employment, right to maintain employment) and its constitutional, international and legal regulation and the position of jurisprudence, the author goes on to discuss the complex picture presented to the employer before a decision to dismiss both from a legal perspective (compensation, replacement) and case law (damages, replacement) adding a paragraph called “others” the recount administrative consequences arising from said measure both labor (SUNAFIL) and tax (SUNAT) viewpoint.
Luego de un breve repaso conceptual de los alcances del derecho a la estabilidad laboral, su relación con otros derechos (derecho al trabajo, derecho de acceso al empleo, derecho a conservar el empleo) y su regulación constitucional, internacional y legal, así como la posición de la jurisprudencia, el autor pasa a comentar el complejo panorama que se presenta al empleador ante una decisión de despido tanto desde la óptica legal (indemnización, reposición) como jurisprudencial (indemnización por daños, reposición) añadiéndose un acápite denominado “otros” para las relatar las consecuencias administrativas que surgen de la indicada medida tanto desde la óptica laboral (SUNAFIL) como tributaria (SUNAT).

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10

Eidėjienė, Audra. "Stuburo stabilizavimo pratimų efektyvumas pooperaciniu tarpslankstelinių diskų išvaržų laikotarpiu." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2006. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2006~D_20060509_125704-61768.

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Object: postoperative treatment of herniated intervertebral disc with stability exercises. Problem: degeneration of the intervertebral disc from a combination of factors can result in herniation. Disk herniation is the protrusion of the gelatinous material of the disk (nucleus pulposus) through the annulus fibrosus (Fardon & Milette, 2001). The presence of pain, radiculopathy and other symptoms depends on the site and degree of herniation. Many treatment modalities have been suggested for lumbar disc herniation, but studies often provide conflicting results (Humphreys & Eck, 1999). Postoperative treatment is very important. Doctor B.Spakauskas with co-authors (2002) says that after operative treatment condition of patient is getting worse. Hypothesis: back stability exercises applied in postoperative herniated disc period using stabilizer should improve endurance of lumbar spine muscles more than applying traditional exercises. The aim of this study was to evaluate effectiveness of back stability exercises in postoperative herniated intervertebral disc period. The tasks: to evaluate static endurance of trunk muscles, strength of hip, calf and foot muscles and low back pain before and after applying back stability exercises; to evaluate static endurance of trunk muscles, strength of hip, calf and foot muscles and low back pain before and after applying traditional (stretching, strengthening) exercise program; to determine which exercise program had better effect on... [to full text]

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11

Caliskan, Sevinc. "Development Of Forward Flight Trim And Longitudinal Dynamic Stability Codes And Their Application To A Uh-60 Helicopter." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610391/index.pdf.

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This thesis describes the development of a series of codes for trim and longitudinal stability analysis of a helicopter in forward flight. In general, particular use of these codes can be made for parametric investigation of the effects of the external and internal systems integrated to UH-60 helicopters. However, in this thesis the trim analysis results are obtained for a clean UH-60 configuration and the results are compared with the flight test data that were acquired by ASELSAN, Inc. The first of the developed trim codes, called TRIM-CF, is based on closedform equations which give the opportunity of having quick results. The second code stems from the trim code of Prouty. That code is modified and improved during the course of this study based on the theories outlined in [3], and the resultant code is named TRIM-BE. These two trim codes are verified by solving the trim conditions of the example helicopter of [3]. Since it is simpler and requires fewer input parameters, it is more often more convenient to use the TRIM-CF code. This code is also verified by analyzing the Bo105 helicopter with the specifications given in [2]. The results are compared with the Helisim results and flight test data given in this reference. The trim analysis results of UH-60 helicopter are obtained by the TRIM-CF code and compared with flight test data. A forward flight longitudinal dynamic stability code, called DYNA-STAB, is also developed in the thesis. This code also uses the methods presented in [3]. It solves the longitudinal part of the whole coupled matrix of equations of motion of a helicopter in forward flight. The coupling is eliminated by linearization. The trim analysis results are used as inputs to the dynamic stability code and the dynamic stability characteristics of a forward flight trim case of the example helicopter [3] are analyzed. The forward flight stability code is applied to UH-60 helicopter. The codes are easily applicable to a helicopter equipped with external stores. The application procedures are also explained in this thesis.

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12

Achioyamen, Chichi Violet, and Johansson Sophia Kazmi. "Institutional Factors and Financial Development in Sub-Saharan Africa for the period 2004-2018 : Control of Corruption, Rule of Law, Political Stability and Absence of Violence, and Voice and Accountability." Thesis, Södertörns högskola, Nationalekonomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-45289.

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The purpose of this study is to have an in-depth understanding of the importance of the institutional environment for financial development in 43 Sub-Saharan African countries during the years 2004-2018. Using new institutional economic theory (NIE) we study how the four institutional factors Control of Corruption, Rule of Law, Political Stability and Absence of Violence, and Voice and Accountability affect financial development. We also survey how the effect of institutional factors varies when there are either high, medium or low levels of corruption. Empirical results show a positive linear relationship between all institutional factors and financial development. However, when corruption levels are high the correlation between institutional factors and financial development varies and has a weak linear relationship. Inferential statistics results from a fixed effect regression model with robust standard errors shows; when we control for the financial environment, Political Stability and Absence of Violence is the only indicator for the institutional environment that has a positive significant effect on financial development. We thereby conclude that the institutional environment, mostly political institutions, are important for financial development.
Syftet med denna studie är att få en djupgående förståelse av institutionell miljö för finansiell utveckling i 43 Subsahariska afrikanska länder för åren 2004–2018. Med hjälp av den nya institutionella ekonomiska teorin undersöker vi hur de fyra institutionella faktorer Kontroll av Korruption, Rättsstat, Politisk Stabilitet och Frånvaro av Våld och Röst och Ansvarsskyldighet påverkar finansiell utveckling. Vi undersöker också hur effekten av institutionella faktorer varierar när det finns hög, medium eller låg nivå av korruption. Empiriskt resultat visar ett positivt linjärt samband mellan alla institutionella faktorer och finansiell utveckling. Däremot, när korruptions nivåerna är höga är korrelationen mellan institutionella faktorer och finansiell utveckling varierar och har ett svagt linjärt samband. Resultatet från inferentiell statistik med fixed-effektregressionsmodell med robust standardfel visar att; när vi kontrollerar för den finansiella miljön, kvarstår endast Politisk Stabilitet och Frånvaro av Våld som en indikator för institutionell miljö som har en positiv signifikant effekt på finansiell utveckling. Vi konstaterar därmed att institutionell miljö, särskilt politiska institutioner är viktiga för finansiell utveckling.

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Machado, Yguatyara de Luna. "Estudo da estabilidade oxidativa de amostras de biodiesel obtidas a partir de diferentes fontes de oleaginosas." reponame:Repositório Institucional da UFC, 2010. http://www.repositorio.ufc.br/handle/riufc/15878.

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MACHADO, Y. L. Estudo da estabilidade oxidativa de amostras de biodiesel obtidas a partir de diferentes fontes de oleaginosas. 86 f. 2010. Dissertação (Mestrado em Engenharia Química) – Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2010.
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Biodiesel is defined as a mixture of alkyl esters obtained by the transesterification reaction of triglycerides such as vegetable oil or animal fat with a short-chained alcohol, usually methanol or ethanol in presence of basic catalysts. However, biodiesel obtained from raw materials which have unsaturated fatty acids in their composition may show less oxidative stability. This fact may jeopardize its storage and use as fuel, but its low stability may be increased by the addition of additives. In this work, a kinetic study of the oxidation reaction of biodiesel samples from castor oil and soybean oil was carried out at different temperatures and pure oxygen pressure of 700 kPa. Kinetic studies were carried out at temperatures of 100, 120 and 140°C with preset stops, as well as the efficiencies of some synthetic antioxidant additives (BHA, PG, TBHQ, DBPC) were evaluated. This study was made according to method ASTM 7545. This method is consisted by submitting samples with and without additives to an oxidation test at 140°C and pure oxygen pressure of 700 kPa. The oxidation degree was monitored by Total Acid Number, Kinematic Viscosity at 40°C and Density at 20°C as parameters. The results showed that temperature increase has a significant effect on oxidation degree of the samples. The results also showed that synthetic antioxidants increased significantly the oxidative stability of the evaluated biodiesel samples. The antioxidant DBPC increased oxidative stability of biodiesel from castor oil by around 6 times. Samples with additive TBHQ showed similar behavior, but samples with higher concentration of DBPC (5000 ppm) showed smaller induction periods. BHA’s antioxidant maximum activity was obtained at concentration of 2000 ppm. The best performance of antioxidant PG was at concentration of 3000 ppm. Antioxidant TBHQ increased oxidative stability of biodiesel from soybean oil by 2 times, while PG showed best activity for the concentration of 1000 ppm and the same level of activity was reached for BHA for concentrations above 2000 ppm.
Biodiesel é definido como sendo uma mistura de ésteres alquílicos obtido a partir de uma reação de transesterificação de um triglicerídeo (óleo vegetal ou gordura animal) com um álcool de cadeia curta, normalmente metanol ou etanol na presença de catalisadores básicos. Entretanto, biodieseis derivados de matérias-primas que possuam ácidos graxos insaturados em sua estrutura terão uma menor estabilidade oxidativa. Este fato pode comprometer a armazenagem e a sua utilização como combustível, no entanto sua baixa estabilidade pode ser superada pela utilização de aditivos. Neste trabalho, realizou-se um estudo cinético da reação de oxidação para as amostras de biodiesel de óleo de mamona e de óleo de soja em função da temperatura e pressão de oxigênio puro a 700 kPa. Os ensaios cinéticos foram realizados nas temperaturas de 100, 120 e 140°C com paradas de tempo pré-determinadas, como também foram avaliadas a eficiência de alguns aditivos antioxidantes sintéticos (BHA, PG, TBHQ e DBPC). O presente estudo foi realizado segundo o método ASTM 7545, onde todas as amostras aditivadas e não aditivadas foram submetidas a um ensaio de oxidação acelerado sob pressão de oxigênio puro a 700 kPa e temperatura de 140°C. O grau de oxidação foi acompanhado pelo Índice de Acidez Total (IAT), Viscosidade Cinemática a 40 °C e Massa Específica a 20 °C. Os resultados obtidos mostraram que o aumento da temperatura exerceu um efeito preponderante sobre o nível de oxidação das amostras com a evolução destas propriedades. Os resultados obtidos também mostraram que os antioxidantes sintéticos aumentaram significantemente a estabilidade oxidadativa das amostras de biodiesel estudadas. Para as amostras de biodiesel de mamona aditivadas com o antioxidante DBPC sua estabilidade aumentou em até 6 vezes, enquanto as amostras aditivadas com o antioxidante TBHQ obtiveram comportamentos semelhantes ao DBPC, porém amostras aditivadas na maior concentração (5000 ppm) deste aditivo obtiveram períodos de indução menores. O antioxidante BHA apresentou uma atividade máxima para concentração de 2000 ppm, enquanto o antioxidante PG apresentou melhor desempenho para amostras aditivadas a partir de 3000 ppm. O antioxidante TBHQ aumentou a estabilidade oxidativa do biodiesel de soja 2 vezes, enquanto o antioxidante PG apresentou melhor atividade para o nível de aditivação de 1000 ppm e esta mesma atividade só pode ser evidenciada para o BHA com amostras aditivadas acima de 2000 ppm.

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Chen, Mingxiang. "Structural stability of periodic systems." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/29341.

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15

Mietka, Colin. "Ondes périodiques dans des systèmes d’ÉDP hamiltoniens : stabilité, modulations et chocs dispersifs." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1031/document.

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La première partie de cette thèse concerne l'étude du problème de Cauchy pour l'équation de KdV quasi-linéaire.On établit un théorème d'existence locale obtenu grâce à des propriétés structurelles et des techniques de jauge qui permettent de compenser les pertes de dérivées apparentes dans les estimations a priori.Dans la seconde partie, les propriétés de stabilité orbitale co-périodique et modulationnelle sont explorées numériquement en exploitant des critères algébriques tous établis à partir d'une même intégrale d'action et de ses dérivées secondes. Notre méthode utilise des quadratures numériques suivies de différences finies afin de calculer la matrice hessienne de l'intégrale d'action. Le comportement asymptotique de cette matrice nous pousse à prêter beaucoup d'attention à l'étude des ondes de grande période ou de faible amplitude. Les résultats numériquesprésentés fournissent de nombreuses informations en lien avec des questions ouvertes.On effectue également des simulations directes sur le système d' ÉDP original pour étudier à la fois le comportement des ondes périodiques sous différents types de perturbations, et les solutions de problèmes de Cauchy avec donnée initiale discontinue. Pour ces derniers, on s'attend à observer des chocs dispersifs, dont la compréhension est basée sur le problème de Gurevich-Pitaevskii, où les équations modulées à la Whitham sont utilisées pour approcher la zone oscillante des chocs. On compare des simulations directes aux solutions idéales du problème de Gurevich-Pitaevskii, en commençant par la célèbre équation de KdV
The first part of this manuscript presents a well-posedness result for a quasilinear version of the KdV equation.The proof takes advantage of structural properties and gauge techniques to deal with apparent loss of derivativesin a priori estimates.In the second part, we investigate the modulational and orbital coperiodic stability of periodic waves by computingalgebraic criteria involving the same abbreviated action integral and its second order derivatives. Our methoduses numerical integrations followed by finite differences to compute the Hessian matrix of the action integral.We pay attention to the asymptotic behavior of this matrix in the large period and small amplitude limits. Thenumerical results about stability give some new insight on several analytical open questions.Finally, direct numerical computations are done on the original system of PDEs to study the behavior of periodictraveling waves under various kinds of perturbations and the solutions of Cauchy problem with discontinuousinitial data. For the latter, we expect dispersive shock waves to arise. The building block for understandingdispersive shocks is known as the Gurevich-Pitaevskii problem, in which modulated equations 'a la Whitham'are used as an approximate model for the oscillatory zone. We compare direct numerical simulations to idealizedsolutions of Gurevich-Pitaevskii problems, starting with the famous KdV equation

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16

Drietz, Thomas. "Using Organic Amendments to Stabilize Sand-based Athletic Fields During Turfgrass Establishment Period." Thesis, North Dakota State University, 2019. https://hdl.handle.net/10365/31150.

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Athletic field rootzones are often sand-based for improved drainage. Sand-based rootzones may have stability issues if turfgrass is not fully established. Our objective was to use organic amendments to improve the stability of sand-based fields during the turfgrass establishment period and avoid overuse of inorganic materials, which have negative effects. We tested coconut coir, peat and wheat straw at 1% organic material, peat at 2% organic material, and an inorganic stabilizing fiber, StaLok, in the top 10 cm of the rootzone. Surface hardness, volumetric water content, traction, penetration resistance and visual quality were measured 2 to 4 months after construction of the plots. Surface hardness was greatest in the inorganic stabilizer and the wheat straw treatments. The kinetic penetration had no differences between the wheat straw (33.78-51.10 kPa) and the StaLok fibers (34.99-56.23 kPa). Wheat straw could be used to stabilize sand-based fields as an organic alternative to inorganic fibers.

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17

Іщик, Дмитро Володимирович. "Підвищення якості свердел із швидкорізальної сталі при магнітно-абразивному обробленні". Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/26703.

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Дисертація на здобуття наукового ступеня магістра за спеціальністю 133 – Галузеве машинобудування. – Національний технічний університет України "Київський політехнічний інститут імені Ігоря Сікорського". – Київ, 2018. Проаналізувавши сучасні методи покращення якості та продуктивності різальної кромки металорізального інструменту, на прикладі свердел, було обрано метод магнітно-абразивного оброблення. Даний метод дозволив досягти значного покращення якості різальної кромки (шорсткості), збільшення значення твердості поверхневого шару і відповідно – періоду стійкості свердла. В дисертації проаналізовано шляхи вирішення проблеми стійкості інструменту при роботі, досліджено процес МАО шляхом проведення експлуатаційних випробувань свердел, оброблених цим методом. Магнітно-абразивні порошки було підібрано зважаючи на поперед ні роботи в цій галузі, а саме – використали порошки великих фракцій. Результати досліджень підтвердили доцільність їх використання наряду з порошками малих фракцій. Експериментальні дані використані та впроваджені на підприємстві ДП «Київський бронетанковий завод».
Dissertation for a Master's degree in specialty 133 – Branch mechanical - engineering. - National Technical University of Ukraine "Kyiv Polytechnic Institute named after Igor Sikorsky". - Kyiv, 2018. Having analyzed the modern methods of improving the quality and productivity of the cutting edge of the metal cutting tool, on the example of the drill, the method of magnetic abrasive treatment was chosen. This method has allowed to achieve a significant improvement in the quality of the cutting edge (roughness), an increase in the hardness of the surface layer and, respectively, the period of drill firmness. In the dissertation the ways of solving the problem of instrument stability during work are analyzed, the process of MAO is investigated by carrying out operational tests of the drills processed by this method. Magnetically-abrasive powders were selected in the light of previous work in this field, namely, the use of powders of large fractions. The results of the studies confirmed the feasibility of their use, along with small fractions powders. Experimental data were used and implemented at the enterprise "Kyiv Armored Plant".

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SILVA, ANDRE LUIS FERREIRA DA. "STABILITY OF EQUITY BETA IN BRAZILIAN STOCK MARKET: AN ASSESSMENT ON HIGHLY VOLATILE PERIODS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=28538@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
O Capital Asset Pricing Model (CAPM) é o modelo mais difundido e utilizado para determinação do custo de capital de empresas e estimação do retorno esperado de ações. Neste modelo, o parâmetro fundamental é o beta, que define a intensidade em que determinado ativo é exposto aos retornos do mercado. O objetivo deste trabalho é avaliar a estabilidade dos betas de uma vasta quantidade de ações no mercado brasileiro em três períodos de alta volatilidade: a crise asiática de 1997, a turbulência no mercado financeiro pré-eleições 2002 e a crise financeira de 2008, nas quais foram analisadas 55, 79 e 172 empresas respectivamente. Cada ciclo de crise foi dividido em três períodos de 52 semanas e os respectivos betas foram comparados utilizando testes de Chow e com regressões com variáveis dummy. Os resultados de ambos os testes foram similares para as crises analisadas, indicando que entre 11 porcento e 27 porcento das empresas apresentaram variação de seus betas, com 5 porcento de significância, quando comparados os períodos pré-crise e durante a crise. Não obstante, ao confrontar períodos pré-crise e pós-crise, a maior parte das empresas que apresentaram variação anteriormente não rejeitaram a hipótese de estabilidade. Estes resultados indicam que, conforme esperado, os betas tendem a ser estáveis no longo prazo.
The Capital Asset Pricing Model (CAPM) is the most widespread model, used to determine the cost of capital of firms and estimate expected stock returns. In this model, the most important parameter is the beta, which defines the magnitude of exposition to market returns, for a particular asset. The objective of this essay is to evaluate beta stability of a vast amount of shares in the Brazilian stock market in three highly volatile periods: the Asian crisis in 1997, the financial market turmoil before 2002 presidential elections and the 2008 financial crisis. The sample included 55, 79 and 172 companies, respectively. Each crisis cycle was then divided into three periods of 52 weeks and then the stability of their betas was measured using regressions with dummy variables and Chow tests. We have reached similar results for the crises analyzed, indicating that between 11 percent and 27 percent of the companies changed their betas when comparing pre-crisis and during crisis periods, with a 95 percent confidence level. Nevertheless, by comparing pre-crisis and post-crisis periods, most of the companies that exhibited change in their betas when entering the crisis, did not reject the stability hypothesis. These results indicate that, as expected, betas tend to be stable in the long term.

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19

Xu, Yeyin. "STABILITY AND BIFURCATION DYNAMICS OF JOURNAL BEARING ROTOR SYSTEMS." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/dissertations/1835.

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In this dissertation, the mechanical models of 2-DOF and 4-DOF nonlinear journal bearing rotor systems are established. A more accurate model of oil film forces is derived from Reynolds equations. The periodic motions in such nonlinear journal bearing systems are obtained through discrete mapping method. Such a semi-analytical method constructs an implicit discrete mapping structure for periodic motions by discretization of the continuous journal bearing rotor differential equations. Stable and unstable periodic solutions of periodic motions are obtained with prescribed accuracy. The bifurcation tree of periodic motions in rotor system without oil film forces is demonstrated through the route from period-1 motion to period-8 motion. Stable period-2 and unstable period-1 motion are presented for 2 DOF journal bearing rotor system. Possibly infinite periodic solutions are found in 4 DOF journal bearing rotor system. For the rotor systems, the stability and bifurcations of periodic motions are analyzed through eigenvalue analysis of the corresponding Jacobian matrix of the discretized nonlinear systems. The frequency amplitude characteristics of periodic motions in 2 DOF journal bearing system are presented for a good understanding of the nonlinear dynamics of journal bearing rotor system in frequency domain . The rich dynamics of the journal bearing systems are discovered. The numerical illustrations of stable periodic motions are brought out with the initial conditions from analytical prediction.

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20

Kawas, Stephen. "The performance of UK financial institutions over periods of market stability and volatility, 1980-2015." Thesis, University of Portsmouth, 2016. https://researchportal.port.ac.uk/portal/en/theses/the-performance-of-uk-financial-institutions-over-periods-of-market-stability-and-volatility(a82eafa1-556a-4188-9516-6674640ac108).html.

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This thesis is concerned with an empirical investigation of the financial performance of UK financial institutions over the period 1980-2015. This period reflects numerous changes in the development of the UK economy and in the evolution and financial deepening of its financial system including also the deregulation and liberalisation of financial markets that culminated in financial institutions being able to compete actively in markets for financial services where previously they were prohibited; the global financial crisis of 2007-2009 and the Eurozone debt crisis which had a strong negative impact on the UK financial sector and resulted in the move away from an informal regulatory structure toward a more rigorous and formal structure of regulation. These developments make it necessary to investigate empirically important factors that shed light on the performance of UK financial institutions which should be of interest to policy makers and regulatory authorities. Following the introduction to the thesis in chapter one and a review of the literature which is presented in chapter two, there are four themes which is the primary focus of this thesis. The first theme, which occupies chapter three investigate, using a panel data regression approach, whether a number of the key drivers of performance affect the financial performance of UK financial institutions over crisis and non-crisis periods, and whether, by means of EGARCH, the risk taking behaviour of financial institutions have a decided impact on their financial performance. The findings indicate that the strength of the UK economy underpins the overall profitability of the sectors. Additionally, we provide strong evidence of risk undertaken is a key variable which impacts profitability in all financial sectors, confirming the risk-return hypothesis. The banking sector is also able to exert greater performance through a highly concentrated market. The second theme, taken up in chapter four, investigates the changing risk profile of UK financial institutions using rolling regression, the Kalman filter, DCC-GARCH, bivariate BEKK GARCH and bivariate GJR-GARCH methodologies. The results confirm the literature by determining beta to be a time-varying variable. We also contribute to the literature by demonstrating the insurance and banking sectors possesses greatest systemic risk throughout our sample years, which can be attributed to their central role in financial markets, risk management and their contribution to the economy. The third theme, which is the focus of chapter five examines the impact of macroeconomic news and other announcements on the stock prices of UK financial institutions. We utilise the event study, SUR and GJR-GARCH techniques to determine the impact of macroeconomic news, which we demonstrated investors were able to distinguish the risk levels of UK banks. Moreover, during periods of crisis government announcements are just as effective as the Bank of England to restore confidence in the financial system. We demonstrated how integrated financial markets are in today’s economic climate due to globalisation. Whereby, announcements from Western economies had a greater impact on UK non-bank financials than combined Bank of England and Government announcements. The fourth theme, which is contained in chapter six assessed the impact of regulatory changes by the UK authorities and other relevant regulatory bodies towards the security prices of UK financial institutions through event study, EGARCH and VAR GJR-GARCH techniques. The Vickers report sought to implement new standards to create financial stability and avert future crisis periods. This led to negative impacts on equity prices on the financial sectors, demonstrating the risk-return hypothesis, along with higher capital requirement regulations mirroring this result. The research provides a basis to develop in-depth knowledge of the UK financial system in order to improve risk management, allocation of resources, decision making by financial institutional managers’ and aid policy makers future decisions to improve market conditions for financial institutions, which will aid overall economic prosperity.

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21

Yedes-Bougatef, Naima. "Commande sous contraintes des systèmes discrets périodiques." Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2305/document.

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Cette thèse se situe dans le cadre de l’analyse et de la synthèse des systèmes périodiques. Les contributions présentées dans ce mémoire portent sur la commande sous contraintes des systèmes linéaires discrets périodiques. Ces contraintes, portant sur l’état du système et/ ou sur la commande, peuvent être des contraintes de positivité ou de bornitude. Dans ce travail, des conditions d’analyse en stabilité et positivité des systèmes périodiques en termes de LMI (Inégalité Matricielle Linéaire) strictes, sont présentées. Ces outils d’analyse ont ensuite permis d’élaborer une loi de commande par retour d’état périodique. Les résultats obtenus sont exploités par la suite pour développer une commande par retour d’état périodique robuste pour les systèmes périodiques incertains. Des conditions de stabilisation robuste sont élaborées en utilisant la S-procédure. En outre, des conditions de stabilité et stabilisation par retour d’état périodique des systèmes périodiques avec retards sont établies. Le problème de stabilisation de ce type de systèmes sous un certain nombre de contraintes est résolu en suivant deux approches, la première est basée sur les techniques de Lyapunov la seconde fait appel à la programmation linéaire. Outre la notion de stabilité, la notion de performance des systèmes en boucle fermée est traitée. Pour cela, nous proposons une commande de type H∞ pour résoudre le problème de rejet de perturbations
This thesis deals with the analysis and the control problem of periodic linear discrete systems (PLDS). The contributions presented in this work focuses on the constrained control of PLDS. Conditions for stability analysis and positivity are established in terms of strict LMI (Linear Matrix Inequalities). The stabilization of PLDS under the condition that the closed-loop system is positive and stable is addressed as well as the case of bounded state and/ or control variables. The obtained results are then extended to the synthesis of robust state feedback controllers, where some of which are based on the S − procedure technique. Furthermore, some conditions of stability and stabilization of PLDS with delays are established. The problem of stabilization of constrained PLDS is addressed based on the Lyapunov techniques or the Linear Programming techniques. The robust H∞ state feedback control in which both robust stability and a prescribed H∞ performance are required is investigated

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22

Jaiswal, Nitin. "Stability Analysis Of Leg Configurations For Bipedal Running." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1566828354395399.

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23

Usman, Muhammad. "Forced Oscillations of the Korteweg-de Vries Equation and Their Stability." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1186552805.

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24

Le, Blanc Valérie. "Stabilité d’ondes périodiques, schéma numérique pour le chimiotactisme." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10091/document.

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Cette thèse est articulée autour de deux facettes de l’étude des équations auxdérivées partielles. Dans une première partie, on étudie la stabilité des solutionspériodiques pour des lois de conservation. On démontre d’abord la stabilité asymptotiquedans L1 des solutions périodiques de lois de conservation scalaires et inhomogènes.On montre ensuite un résultat de stabilité structurelle des roll-waves. Plusprécisément, on montre que les solutions périodiques d’un système hyperbolique sansviscosité sont limites des solutions du problème avec viscosité, quand le terme deviscosité tend vers 0. Dans une deuxième partie, on s’intéresse à un système d’équationsaux dérivées partielles issu de la biologie : le modèle de Patlak-Keller-Segelen dimension 2 ; il décrit les phénomènes de chimiotactisme. Pour ce modèle, onconstruit un schéma de type volume fini, ce qui permet d’approcher la solution touten gardant certaines propriétés du système : positivité, conservation de la masse,estimation d’énergie
This thesis is organized around two aspects of the study of partial differentialequations. In a first part, we study the stability of periodic solutions for conservationlaws. First, we prove asymptotic L1-stability of periodic solutions of scalarinhomogeneous conservation laws. Then, we show a result on structural stability ofroll-waves. More precisely, we prove that periodic solutions of a hyperbolic systemwithout viscosity are the limits of the solutions of the problem with viscosity, as theviscous term tends to 0. In a second part, we study a system of partial differentialequations derived from biology: the model of Patlak-Keller-Segel in dimension 2, describingthe phenomena of chemotaxis. For this model, we construct a finite-volumescheme, which approaches the solution while keeping some properties of the system:positivity, conservation of mass, energy estimate

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Ghisi, Mirela. "Determinação de Cu e Fe em Biodiesel por Espectrometria de Absorção Atômica com Atomização Eletrotérmica e Estudo do Efeito Catalítico destes Metais sobre a Estabilidade Oxidativa do Biodiesel." Universidade Federal do Maranhão, 2011. http://tedebc.ufma.br:8080/jspui/handle/tede/918.

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Made available in DSpace on 2016-08-19T12:56:36Z (GMT). No. of bitstreams: 1 MIRELA GHISI.pdf: 1324849 bytes, checksum: 5d9ca5c5a49c366f3bf4959e2e942a14 (MD5) Previous issue date: 2011-05-16
Conselho Nacional de Desenvolvimento Científico e Tecnológico
The metals content in biodiesel is directly related with the raw material used and also with the utilized biodiesel production method. In this work, an evaluation of the main metals present in biodiesel samples from different sources was done. The qualitative analysis of the metal content was assessed using the Inductively Coupled Plasma Mass Spectrometry technique after sample digestion in microwave oven. The main metals identified in the analyzed biodiesel samples were Al, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr and Zn. Metals like Ag, As, Ba, Cd, Co, Tl and V have not significant presence in the samples. Among these, Cu and Fe were selected due to their relevance and importance in oxidative process of biodiesel, to the development of an analytical methodology to be used in the determination by Electrothermal Atomic Absorption Spectrometry, and also evaluate the effect of these metals over the oxidative stability of the soy biodiesel. The samples were prepared with tetramethylammonium hydroxide (TMAH), and the pyrolysis and atomization temperatures were optimized pyrolysis and atomization curves. The high pyrolysis temperature adopted, 1000 oC, certainly minimized potential interferences, but calibration had to be carried out with aqueous standard solutions in the presence of the TMAH. The detection limits in the sample (3s, n=10), were quite low 15 ng g-1 and 24 ng g-1 for Cu and Fe, respectively. Seven biodiesel samples, produced from different raw materials, including vegetable seed, waste frying oil and animal fat were analyzed. Accuracy was validated by applying the recovery test (recoveries from 105% to 120%) and through comparison with the obtained results by High Resolution Continuum Source Electrothermal Atomic Absorption Spectrometry. The precision, expressed by the relative standard deviation, was better than 3% for Cu and than 7% for Fe. Copper could be quantified in two and Fe in three of the seven samples. The biodiesel sample from fodder turnip was especially rich in the analytes in comparison to the other samples. The influence of metals Cu and Fe on soy biodiesel oxidative stability was evaluated by Rancimat method through induction period, according with the Standard EN 14112. The metals Cu2+ and Fe3+ were added to the biodiesel samples in the form of theirs salts, and different storage times of the samples were evaluated. Due to the catalytic behaviour of these metals, the oxidative stability of the samples was affected, even under low metal concentrations. Compared to Cu2+, the effect over the biodiesel stability was higher when Fe3+ was added.
A presença de metais no biodiesel está diretamente relacionada com a matéria-prima utilizada e também com o processo utilizado para a obtenção do biodiesel. Neste trabalho realizou-se uma avaliação dos principais metais presentes em amostras de biodiesel provenientes de diferentes fontes. A análise semi-quantitativa nas amostras de biodiesel foi realizada utilizando a técnica de Espectrometria de Massa com Plasma Indutivamente Acoplado após a digestão das amostras em micro-ondas. Os principais metais identificados nas amostras de biodiesel analisadas são Al, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr e Zn. Metais como Ag, As, Ba, Cd, Co, Tl e V não estão presentes em concentrações significativas nessas amostras. Em função de sua relevância e importância em processos oxidativos do biodiesel, selecionou-se Cu e Fe para o desenvolvimento de uma metodologia analítica para a determinação destes por Espectrometria de Absorção Atômica com Atomização Eletrotérmica e também a avaliação do efeito destes metais sobre a estabilidade oxidativa do biodiesel de soja. As amostras foram preparadas com hidróxido de tetrametilamônio (TMAH), e as temperaturas de pirólise e atomização foram otimizadas através de curvas de pirólise e atomização. A alta temperatura de pirólise adotada, 1000 oC, certamente ajudou a minimizar possíveis interferências; porém, a calibração teve de ser realizada com padrões aquosos na presença de TMAH. Os limites de detecção (3s, n = 10), na amostra, foram baixos, 15 ng g-1 e 24 ng g-1 para Cu e Fe, respectivamente. Sete amostras de biodiesel, produzidas de diferentes matérias-primas, incluindo óleos vegetais, óleo de fritura e gordura animal foram analisadas. A exatidão foi avaliada através do teste de recuperação (recuperações de 105% a 120%) e através da comparação com os resultados obtidos por Espectrometria de Absorção Atômica de Alta Resolução com Fonte Contínua e Atomização Eletrotérmica. A precisão, expressa pelo desvio padrão relativo foi melhor que 3% para Cu e que 7% para Fe. Cobre pôde ser quantificado em duas e Fe em três das sete amostras. A amostra de biodiesel proveniente do nabo forrageiro era especialmente rica nos analitos comparada às outras amostras. A influência dos metais Cu e Fe sobre a estabilidade oxidativa do biodiesel de soja foi avaliada pelo método Rancimat através do período de indução, de acordo com a Norma EN 14112. Os metais Cu2+ e Fe3+ foram adicionados nas amostras de biodiesel na forma de seus sais, e foram avaliados diferentes tempos de armazenamento das amostras. Devido ao efeito catalítico destes metais, a estabilidade oxidativa das amostras analisadas foi reduzida mesmo na presença de baixas concentrações dos metais. O efeito do Fe3+ sobre a estabilidade do biodiesel foi significativamente maior quando comparado ao Cu2+.

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26

Alzabut, Jehad. "Periodic Solutions And Stability Of Linear Impulsive Delay Differential Equations." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12604901/index.pdf.

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In this thesis, we investigate impulsive differential systems with delays of the form And more generally of the form The dissertation consists of five chapters. The first chapter serves as introduction, contains preliminary considerations and assertions that will be encountered in the sequel. In chapter 2, we construct the adjoint systems and obtain the variation of parameters formulas of the solutions in terms of fundamental matrices. The asymptotic behavior of solutions of systems satisfying the Perron condition is investigated in chapter 3. In chapter4, we give a result that characterizes the behavior of solutions in the case there is a bounded solution. Moreover, a necessary and sufficient condition for the existence of periodic solutions is obtained. In the last chapter, a series of consequences on the existence of periodic solutions of functionally equivlent impulsive systems with delays is established.

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27

Fedorková, Lucie. "Metody stabilizace nestabilních řešení diskrétní logistické rovnice." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400443.

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Diplomová práce pojednává o stabilizaci diskrétního logistického modelu pomocí několika řídících metod. Je zde provedena především stabilizace rovnováh, 2-periodických cyklů a 3-periodických cyklů. Ke stabilizaci systému je využito proporčního zpětně-vazebního řízení, zpětně-vazebního řízení s časovým zpožděním a řízení založeného na predikci. U každé metody je diskutovaná stabilizační množina pro řídící zesilovač spolu s oblastmi stability pro odpovídající kontrolovaná řešení. Všechny teoretické výsledky jsou ilustrovány grafickými interpretacemi v softwaru MATLAB. Podpůrné výpočty jsou provedeny pomocí softwaru Maple.

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28

Mostefaoui, Imene Meriem. "Analyse mathématique d’un système dynamique/réaction-diffusion modélisant la distribution des bactéries résistantes aux antibiotiques dans les rivières." Thesis, La Rochelle, 2014. http://www.theses.fr/2014LAROS020/document.

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L'objectif de cette thèse est l'étude qualitative de certains modèles de la dynamique et la distribution des bactéries dans une rivière. Il s'agit de la stabilité des états stationnaires et l'existence des solutions périodiques. Nous considérons, dans la première partie de la thèse, un système d'équations différentielles ordinaires qui modélise les interactions et la dynamique de quatre espèces de bactéries dans une rivière. Nous avons étudié le comportement asymptotique des états stationnaires. L'étude de la stabilité des états stationnaires est essentiellement faite par la construction d'une fonction de Lyapunov combinée avec le principe d'invariance de LaSalle. D'autre part, l'existence des solutions périodiques est démontrée en utilisant le théorème de continuation de Mawhin. La deuxième partie de la thèse est consacrée à l'étude d'un système de convection-diffusion non-autonome. Ce modèle tient compte du transport des bactéries. Nous étudions l'analyse qualitative des solutions, nous déterminons l'ensemble limite du système et nous démontrons l'existence des états stationnaires positifs. L'étude de l'existence des états stationnaires (les seuls qu'il soit possible d'obtenir) est basée sur le théorème de Leray-Schauder
The objective of this thesis is the qualitative study of some models of the dynamic and the distribution of bacteria in a river. We are interested in the stability of equilibria and the existence of periodic solutions. The thesis can be divided into two parts; the first part is concerned with a mathematical analysis of a system of differential equations modelling the dynamics and the interactions of four species of bacteria in a river. The asymptotic behavior of equilibria is established. The stability study of equilibrium states is mainly done by construction of Lyapunov functions combined with LaSalle's invariance principle. On the other hand, the existence of periodic solutions is proved under certain conditions using the continuation theorem of Mawhin. In the second part of this thesis, we propose a non-autonomous convection-reaction diffusion system with nonlinear reaction source functions. This model refers to the quantification and the distribution of antibiotic resistant bacteria (ARB) in a river. Our main contributions are : (i) the determination of the limit set of the system; it is shown that it is reduced to the solutions of the associated elliptic system; (ii) sufficient conditions for the existence of a positive solution of the associated elliptic system based on the Leray Schauder's degree theory

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29

Caetano, Marcelo Farias. "Estabilidade vertical no problema circular de Sitnikov." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/45/45132/tde-23072012-133230/.

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Estudamos um caso especial do problema restrito dos três corpos, chamado problema circular de Sitnikov, quando dois corpos de massas iguais (chamadas de primárias) estão em uma órbita circular (configuração central de dois corpos), enquanto que um terceiro corpo de massa negligenciada (chamada infinitesimal) oscila sobre uma reta perpendicular ao plano das primárias (chamaremos esse movimento de vertical periódico). Aqui analisamos a estabilidade desse movimento periódico, com relação a pequenas perturbações nas direções ortogonais a reta onde ocorre o movimento. Chamaremos a atenção ao fenômeno de alternância entre estabilidade e instabilidade na família do movimento periódico vertical, conforme variamos a amplitude do movimento.
We studied a special case of the restricted three-body problem, named circular problem of Sitnikov, when two body of equal mass (called primaries) moving around each other on circular motion (central configuration of two body), while the third body of negligible mass (called infinitesimal) performs along a straight line orthogonal to the plane of the primaries (so called periodic vertical motions). We analyze the stability of the periodic vertical motions with respect to small perturbations orthogonal to the straight line where the motions occurs. We call attention to the phenomenom of alternation of stability and instability within the family of periodic vertical motions, whenever their amplitude is varied in a continuous manner.

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30

Turan, Mehmet. "New Classes Of Differential Equations And Bifurcation Of Discontinuous Cycles." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610747/index.pdf.

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In this thesis, we introduce two new classes of differential equations, which essentially extend, in several directions, impulsive differential equations and equations on time scales. Basics of the theory for quasilinear systems are discussed, and particular results are obtained so that further investigations of the theory are guaranteed. Applications of the newly-introduced systems are shown through a center manifold theorem, and further, Hopf bifurcation Theorem is proved for a three-dimensional discontinuous dynamical system.

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31

Lange, Carsten. "Advanced nonlinear stability analysis of boiling water nuclear reactors." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-24954.

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This thesis is concerned with nonlinear analyses of BWR stability behaviour, contributing to a deeper understanding in this field. Despite negative feedback-coefficients of a BWR, there are operational points (OP) at which oscillatory instabilities occur. So far, a comprehensive and an in-depth understanding of the nonlinear BWR stability behaviour are missing, even though the impact of the significant physical parameters is well known. In particular, this concerns parameter regions in which linear stability indicators, like the asymptotic decay ratio, lose their meaning. Nonlinear stability analyses are usually carried out using integral (system) codes, describing the dynamical system by a system of nonlinear partial differential equations (PDE). One aspect of nonlinear BWR stability analyses is to get an overview about different types of nonlinear stability behaviour and to examine the conditions of their occurrence. For these studies the application of system codes alone is inappropriate. Hence, in the context of this thesis, a novel approach to nonlinear BWR stability analyses, called RAM-ROM method, is developed. In the framework of this approach, system codes and reduced order models (ROM) are used as complementary tools to examine the stability characteristics of fixed points and periodic solutions of the system of nonlinear differential equations, describing the stability behaviour of a BWR loop. The main advantage of a ROM, which is a system of ordinary differential equations (ODE), is the possible coupling with specific methods of the nonlinear dynamics. This method reveals nonlinear phenomena in certain regions of system parameters without the need for solving the system of ROM equations. The stability properties of limit cycles generated in Hopf bifurcation points and the conditions of their occurrence are of particular interest. Finally, the nonlinear phenomena predicted by the ROM will be analysed in more details by the system code. Hence, the thesis is not focused on rendering more precisely linear stability indicators like DR. The objective of the ROM development is to develop a model as simple as possible from the mathematical and numerical point of view, while preserving the physics of the BWR stability behaviour. The ODEs of the ROM are deduced from the PDEs describing the dynamics of a BWR. The system of ODEs includes all spatial effects in an approximated (spatial averaged) manner, e.g. the space-time dependent neutron flux is expanded in terms of a complete set of orthogonal spatial neutron flux modes. In order to simulate the stability characteristics of the in-phase and out-of-phase oscillation mode, it is only necessary to take into account the fundamental mode and the first azimuthal mode. The ROM, originally developed at PSI in collaboration with the University of Illinois (PSI-Illinois-ROM), was upgraded in significant points: • Development and implementation of a new calculation methodology for the mode feedback reactivity coefficients (void and fuel temperature reactivity) • Development and implementation of a recirculation loop model; analysis and discussion of its impact on the in-phase and out-of-phase oscillation mode • Development of a novel physically justified approach for the calculation of the ROM input data • Discussion of the necessity of consideration of the effect of subcooled boiling in an approximate manner With the upgraded ROM, nonlinear BWR stability analyses are performed for three OPs (one for NPP Leibstadt (cycle7), one for NPP Ringhals (cycle14) and one for NPP Brunsbüttel (cycle16) for which measuring data of stability tests are available. In this thesis, the novel approach to nonlinear BWR stability analyses is extensively presented for NPP Leibstadt. In particular, the nonlinear analysis is carried out for an operational point (OP), in which an out-of-phase power oscillation has been observed in the scope of a stability test at the beginning of cycle 7 (KKLc7_rec4). The ROM predicts a saddle-node bifurcation of cycles, occurring in the linear stable region, close to the KKLc7_rec4-OP. This result allows a new interpretation of the stability behaviour around the KKLc7_rec4-OP. The results of this thesis confirm that the RAM-ROM methodology is qualified for nonlinear BWR stability analyses
Die vorliegende Dissertation leistet einen Beitrag zum tieferen Verständnis des nichtlinearen Stabilitätsverhaltens von Siedewasserreaktoren (SWR). Trotz der Tatsache, dass in diesem technischen System nur negative innere Rückkopplungskoeffizienten auftreten, können in bestimmten Arbeitspunkten oszillatorische Instabilitäten auftreten. Obwohl relativ gute Kenntnisse über die signifikanten physikalischen Einflussgrößen vorliegen, fehlt bisher ein umfassendes Verständnis des SWR-Stabilitätsverhaltens. Das betrifft insbesondere die Bereiche der Systemparameter, in denen lineare Stabilitätsindikatoren, wie zum Beispiel das asymptotische Decay Ratio (DR), ihren Sinn verlieren. Die nichtlineare Stabilitätsanalyse wird im Allgemeinen mit Systemcodes (nichtlineare partielle Differentialgleichungen, PDG) durchgeführt. Jedoch kann mit Systemcodes kein oder nur ein sehr lückenhafter Überblick über die Typen von nichtlinearen Phänomenen, die in bestimmten System-Parameterbereichen auftreten, erhalten werden. Deshalb wurde im Rahmen der vorliegenden Arbeit eine neuartige Methode (RAM-ROM Methode) zur nichtlinearen SWR-Stabilitätsanalyse erprobt, bei der integrale Systemcodes und sog. vereinfachte SWR-Modelle (ROM) als sich gegenseitig ergänzende Methoden eingesetzt werden, um die Stabilitätseigenschaften von Fixpunkten und periodischen Lösungen (Grenzzyklen) des nichtlinearen Differentialgleichungssystems, welches das Stabilitätsverhalten des SWR beschreibt, zu bestimmen. Das ROM, in denen das dynamische System durch gewöhnliche Differentialgleichungen (GDG) beschrieben wird, kann relativ einfach mit leistungsfähigen Methoden aus der nichtlinearen Dynamik, wie zum Beispiel die semianalytische Bifurkationsanalyse, gekoppelt werden. Mit solchen Verfahren kann, ohne das DG-System explizit lösen zu müssen, ein Überblick über mögliche Typen von stabilen und instabilen oszillatorischen Verhalten des SWR erhalten werden. Insbesondere sind die Stabilitätseigenschaften von Grenzzyklen, die in Hopf-Bifurkationspunkten entstehen, und die Bedingungen, unter denen sie auftreten, von Interesse. Mit dem Systemcode (RAMONA5) werden dann die mit dem ROM vorhergesagten Phänomene in den entsprechenden Parameterbereichen detaillierter untersucht (Validierung des ROM). Die Methodik dient daher nicht der Verfeinerung der Berechnung linearer Stabilitätsindikatoren (wie das DR). Das ROM-Gleichungssystem entsteht aus den PDGs des Systemcodes durch geeignete (nichttriviale) räumliche Mittelung der PDG. Es wird davon ausgegangen, dass die Reduzierung der räumlichen Komplexität die Stabilitätseigenschaften des SWR nicht signifikant verfälschen, da durch geeignete Mittlungsverfahren, räumliche Effekte näherungsweise in den GDGs berücksichtig werden. Beispielsweise wird die raum- und zeitabhängige Neutronenflussdichte nach räumlichen Moden entwickelt, wobei für eine Simulation der Stabilitätseigenschaften der In-phase- und Out-of-Phase-Leistungsoszillationen nur der Fundamentalmode und der erste azimuthale Mode berücksichtigt werden muss. Das ROM, welches ursprünglich am Paul Scherrer Institut (PSI, Schweiz) in Zusammenarbeit mit der Universität Illinois (USA) entwickelt wurde, ist in zwei wesentlichen Punkten erweitert und verbessert worden: • Entwicklung und Implementierung einer neuen Methode zur Berechnung der Rückkopplungsreaktivitäten • Entwicklung und Implementierung eines Modells zur Beschreibung der Rezirkulationsschleife (insbesondere wurde der Einfluss der Rezirkulationsschleife auf den In-Phase-Oszillationszustand und auf den Out-of-Phase-Oszillationszustand untersucht) • Entwicklung einer physikalisch begründeten Methode zur Berechnung der ROM-Inputdaten • Abschätzung des Einflusses des unterkühlten Siedens im Rahmen der ROM-Näherungen Mit dem erweiterten ROM wurden nichtlineare Stabilitätsanalysen für drei Arbeitspunkte (KKW Leibstadt (Zyklus 7) KKW Ringhals (Zyklus 14) und KKW Brunsbüttel (Zyklus 16)), für die Messdaten vorliegen, durchgeführt. In der Dissertationsschrift wird die RAM-ROM Methode ausführlich am Beispiel eines Arbeitspunktes (OP) des KKW Leibstadt (KKLc7_rec4-OP), in dem eine aufklingende regionale Leistungsoszillation bei einem Stabilitätstest gemessen worden ist, demonstriert. Das ROM sagt die Existenz eines Umkehrpunktes (saddle-node bifurcation of cycles, fold-bifurcation) voraus, der sich im linear stabilen Gebiet nahe der Stabilitätsgrenze befindet. Mit diesem ROM-Ergebnis ist eine neue Interpretation der Stabilitätseigenschaften des KKLc7_rec4-OP möglich. Die Resultate der in der Dissertation durchgeführten RAM-ROM Analyse bestätigen, dass das weiterentwickelte ROM für die Analyse des Stabilitätsverhaltens realer Leistungsreaktoren qualifiziert wurde

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32

Sebbah, Matthieu. "Stabilité d'inégalités variationnelles et prox-régularité, équations de Kolmogorov périodiques contrôlées." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20205/document.

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Dans une première partie, nous étudions la stabilité des solutions d'une inégalité variationnelle de la forme cône normal perturbé par une fonction. Pour ce faire, nous généralisons la méthode de S. Robinson, basée sur le degré topologique, aux espaces de Hilbert et à une classe de multi-applications non nécessairement convexes, appelées multi-applications prox-régulières. Dans une deuxième partie, nous étudions des problèmes de contrôle optimal liés à la modélisation de problèmes de bio-procédés, et l'on s'intéresse à des contraintes périodiques sur l'état. Ainsi, nous étendons les résultats d'existence de solutions périodiques des EDOs de Kolmogorov au cadre du contrôle en rajoutant un paramètre contrôlé à ces équations. Ceci nous permet d'étudier par la suite un problème de commande optimale d'un chemostat sous forçage périodique, et d'en déduire la synthèse optimale pour ce problème
In the first part, we study stability of solutions of a variational inequality of the form normal cone perturbed by a mapping. To do so, we generalize the method introduced by S. Robinson, based on the topological degree, to the general Hilbert setting on the class of non-necessarily convex set-valued mapping, called prox-regular set-valued mapping. In the second part, we study optimal control problems connected to the modelization of bio-processes and we consider periodic constraints on the state variable. We first extend the existence result of periodic solutions of Kolmogorov ODEs to the setting of control by adding a controlled parameter to those ODEs. This allows us to study an optimal control problem modeling a chemostat under a periodic forcing for which we give the optimal synthesis

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33

Yan, Duokui. "Four-body Problem with Collision Singularity." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd3111.pdf.

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34

Dias, Elaine Santos. "Caracterização da região de estabilidade de sistemas dinâmicos discretos não lineares." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-21112016-110309/.

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O estudo da região de estabilidade é de extrema importância nas ciências, aplicações em engenharia e nos sistemas de controle não linear. Neste trabalho, uma caracterização completa da região de estabilidade e da fronteira da região de estabilidade de pontos fixos estáveis de uma classe ampla de sistemas dinâmicos discretos não lineares é desenvolvida. Os resultados deste trabalho estendem a caracterização da região de estabilidade já proposta na literatura para uma ampla classe de sistemas, modelados por difeomorfismos e que admitem a presença de órbitas periódicas e pontos fixos na fronteira da região de estabilidade. Caracterizações dinâmicas e topológicas são propostas para a fronteira da região de estabilidade. Além disso, são dadas condições necessárias e suficientes para que um ponto fixo ou órbita periódica pertença à fronteira da região de estabilidade. Exemplos numéricos, incluindo o modelo de uma rede neural simétrica com 2-neurônios, ilustram os resultados propostos neste trabalho.
The study of the stability region is very important in the sciences, engineering applications, and in nonlinear control systems. In this work, a complete characterization for both the stability region and the stability boundary of stable xed points of a nonlinear discrete dynamical systems is developed. The results of this work extend the characterization of the stability region already proposed in the literature for a larger class of systems, which are modeled by dieomorphisms and which admit the presence of periodic orbits and xed points on the stability boundary. Several dynamical and topological characterizations are proposed to the stability boundary. Moreover, several necessary and sucient conditions for xed points and periodic orbits to lie on the stability boundary are derived. Numerical examples, including the model of a symmetric neural network with 2-neurons, illustrate the results proposed in this work.

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35

Yilmaz, Enes. "Neural Networks With Piecewise Constant Argument And Impact Activation." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613307/index.pdf.

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This dissertation addresses the new models in mathematical neuroscience: artificial neural networks, which have many similarities with the structure of human brain and the functions of cells by electronic circuits. The networks have been investigated due to their extensive applications in classification of patterns, associative memories, image processing, artificial intelligence, signal processing and optimization problems. These applications depend crucially on the dynamical behaviors of the networks. In this thesis the dynamics are presented by differential equations with discontinuities: differential equations with piecewise constant argument of generalized type, and both impulses at fixed moments and piecewise constant argument. A discussion of the models, which are appropriate for the proposed applications, are also provided. Qualitative analysis of existence and uniqueness of solutions, global asymptotic stability, uniform asymptotic stability and global exponential stability of equilibria, existence of periodic solutions and their global asymptotic stability for these networks are obtained. Examples with numerical simulations are given to validate the theoretical results. All the properties are rigorously approved by using methods for differential equations with discontinuities: existence and uniqueness theorems
stability analysis through the Second Lyapunov method and linearization. It is the first time that the problem of stability with the method of Lyapunov functions for differential equations with piecewise constant argument of generalized type is investigated. Despite the fact that these equations are with deviating argument, stability criteria are merely found in terms of Lyapunov functions.

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36

Buyukadali, Cemil. "Periodic Solutions And Stability Of Differential Equations With Piecewise Constant Argument Of Generalized Type." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610746/index.pdf.

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In this thesis, we study periodic solutions and stability of differential equations with piecewise constant argument of generalized type. These equations can be divided into three main classes: differential equations with retarded, alternately advanced-retarded, and state-dependent piecewise constant argument of generalized type. First, using the method of small parameter due to Poincaré
, the existence and stability of periodic solutions of quasilinear differential equations with retarded piecewise constant argument of generalized type in noncritical case, that is, the unperturbed linear ordinary differential equation has not any nontrivial periodic solution, are investigated. The continuous and differential dependence of the solutions on an initial value and a parameter is considered. A new Gronwall-Bellmann type lemma is proved. Next, quasilinear differential equations with alternately advanced-retarded piecewise constant argument of generalized type is addressed. The critical case, when associated linear homogeneous system admits nontrivial periodic solutions, is considered. Using the technique of Poincaré
-Malkin, criteria of existence of periodic solutions of such equations are obtained. One of the main auxiliary results is an analogue of Gronwall-Bellmann Lemma for functions with alternately advanced-retarded piecewise constant argument. Dependence of solutions on an initial value and a parameter is investigated. Finally, a new class of differential equations with state-dependent piecewise constant argument is introduced. It is an extension of systems with piecewise constant argument. Fundamental theoretical results for the equations: existence and uniqueness of solutions, the existence of the periodic solutions, the stability of the zero solution are obtained. Appropriate examples are constructed.

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37

Chahine, Chakib. "Stabilité et bifurcation des solutions périodiques d'unsystème hamiltonien en dimension deux." Pau, 1987. http://www.theses.fr/1987PAUU3013.

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Le but essentiel du travail présenté est l'étude numérique d'un système hamiltonien conservatif non intégrale en dimension deux d'espace. Les solutions périodiques fondamentales issues de la position d'équilibre par bifurcation sont analysées, et leur stabilité orbitale etudiée. Pour chaque solution périodique fondamentale, on a pu mettre en évidence une séquence de bifurcations successives quand le paramètre énergie est varié. On a pu, enfin, mettre en évidence une transition vers un comportement chaotique lorsque le paramètre énergie augmente. Un seuil de stochasticité a pu être évalué.

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Oukil, Walid. "Systèmes couplés et morphogénèse auto-organisation de systèmes biologiques." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0459/document.

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On s’intéresse dans cette thèse à des systèmes couplés de type champ moyen en étudiant l’existence de l’état de synchronisation qui se caractérise par une distance uniformément bornée dans le temps entre chaque paire de composantes d’une solution. L’étude se base sur une méthode perturbative. Néanmoins les résultats obtenus ne sont pas évidents dans le cas non-perturbé. En outre dans le cas où le système couplé est périodique et grâce au Théorème du point fixe on montre l’existence d’une solution périodique sur le tore. L’étude de stabilité et de stabilité exponentielle est établie dans le cas linéaire et appliquée à ce type de systèmes couplés
We study in this thesis a class of a perturbed interconnected mean-field system, also known as a coupled systems. Under some assumptions we prove the existence of an invariant open set by the flow of the perturbed system ; in other word, we prove that the distance between the components of an orbit is uniformly bounded, this property is also called synchronization. We use the perturbation method to obtain the result. However the result is not trivial for the not perturbed system. We use the fixed point theorem to prove the existence of a periodic orbit in the torus. We study in addition the stability and the exponential stability of such systems by studying the stability of a linear systems

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39

Rohlén, Karl, and Pontus Ekdahl. "Uncovered Interest Parity and the Financial Crisis of 2007 : An econometric study of the robustness of the uncovered interest parity over different time periods, with varying economic stability." Thesis, Internationella Handelshögskolan, Högskolan i Jönköping, IHH, Nationalekonomi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-44249.

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The current intellectual climate regarding economics seems to be at an agreement regarding the theory of uncovered interest parity and its unreliability within real life application. The purpose of this thesis is to test how the theory holds over periods with varying economic stability, both using a short- and long-horizon test in order to establish the usefulness of uncovered interest parity as a predictor for exchange rate movements. The short-horizon test will utilize the interbank offering rate, and the long-horizon test the yield to maturity of government 10-year benchmark bonds as the interest rate. The sample period is 2000 to 2018, covering the financial crisis of 2007. We will focus on three different time periods: pre-crisis, crisis and post-crisis. We will use ordinary least squares (OLS) regression and an extreme sampling. From the regressions we conclude that most of the time periods move against the uncovered interest parity, where only the crisis period is in line with the theory. The extreme sampling supports this result, as larger interest differentials provide the rational expectations with more predictive power of the future spot exchange rate.

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Bílková, Alice. "Posouzení ekonomické efektivnosti investičního projektu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240007.

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The subject of this thesis is to assess the economic efficiency of the investment project. The theoretical part focuses on the basic definitions related to investment decisions on the investment project and the project life cycle, cash flows and their predictions and recommendations to set them correctly, methods useful for assessing the effectiveness of the investment project and the indicators presenting the financial stability and feasibility of the project as well as factors affecting the overall investment decision, and finally the possibility of financing of the investment projects in the private sector. In the practical part there are the theoretical findings applied in the real investment project. Specifically, there will be analyzed the characterized investment project and its possible alternatives and finally made the assessment of economic efficiency.

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Pancieri, José Guilherme Pelição. "Análise de movimentos periódicos em sistemas bi-linear com folga simétrica." Universidade Federal do Espírito Santo, 2012. http://repositorio.ufes.br/handle/10/6256.

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Made available in DSpace on 2016-12-23T14:08:15Z (GMT). No. of bitstreams: 1 Jose Guilherme Pelicao Pancieri.pdf: 849076 bytes, checksum: 4cc56d57d53f4b6c3d0fd9c325a5bd22 (MD5) Previous issue date: 2012-03-27
O presente trabalho apresenta a modelagem matemática de um sistema vibracional com excitação harmônica da base. Esse tipo de sistema tem sido estudado por vários pesquisadores que exploraram muitos aspectos da dinâmica global. No entanto, na grande parte dos sistemas estudados, o sistema era modelado para uma característica de vibroimpacto. No sistema aqui estudado, os impactos são substituídos por outro conjunto visco-elástico e os instantes de transição são considerados como condição de periodicidade. As condições de periodicidade são aplicadas sobre o estado nos instantes de transição a fim de obter um mapa da próxima transição baseada no estado da anterior. Este mapa não-linear é aplicado para obter as condições de existência dos movimentos periódicos com padrões específicos. Assim, aplicando as condições de existência, a estabilidade do movimento pode ser realizada por meio da análise dos autovalores do mapa linearizado, tendo em conta estas restrições
This work presents the mathematical modeling of a vibrational system with the harmonically excited base. The system has been investigated by several researchers exploring many aspects of the global dynamics. However, in most of the systems studied, the systems were modeled for a vibro-impact feature. In this system, the impacts are replaced by another visco-elastic set and the moment of transition is considered as a condition of periodicity. Periodicity conditions are applied on the state at the moment of transition in order to obtain a map of the next transition based on the state of the previous one. This nonlinear map is used to obtain the conditions of existence of periodic motions with specific patterns. Applying the existence conditions, the stability of the motion can be achieved by analyzing the eigenvalues of the linearized map while taking these conditions into account

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Luís, Rafael Domingos Garanito. "Nonautonomous difference equations with applications." Doctoral thesis, Universidade da Madeira, 2011. http://hdl.handle.net/10400.13/206.

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This work is divided in two parts. In the first part we develop the theory of discrete nonautonomous dynamical systems. In particular, we investigate skew-product dynamical system, periodicity, stability, center manifold, and bifurcation. In the second part we present some concrete models that are used in ecology/biology and economics. In addition to developing the mathematical theory of these models, we use simulations to construct graphs that illustrate and describe the dynamics of the models. One of the main contributions of this dissertation is the study of the stability of some concrete nonlinear maps using the center manifold theory. Moreover, the second contribution is the study of bifurcation, and in particular the construction of bifurcation diagrams in the parameter space of the autonomous Ricker competition model. Since the dynamics of the Ricker competition model is similar to the logistic competition model, we believe that there exists a certain class of two-dimensional maps with which we can generalize our results. Finally, using the Brouwer’s fixed point theorem and the construction of a compact invariant and convex subset of the space, we present a proof of the existence of a positive periodic solution of the nonautonomous Ricker competition model.
Henrique Oliveira and Saber Elaydi

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Pralx, Laurent. "Commande linéaire adaptative : solutions bornées et leurs propriétés." Paris 9, 1988. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=1988PA090035.

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On est amené à modifier des lois d'adaptation en remarquant que les effets non modélisés par un modèle linéaire peuvent sous des hypothèses réalistes être majorées par une norme des signaux d'entrées-sorties. D'autre part, on propose une méthode d'analyse des portraits de phase des systèmes linéaires adaptatifs

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Karaki, Mariam. "Matériaux à porosité contrôlée sulfonés : Synthèse, Caractérisation, Etude des propriétés catalytiques." Phd thesis, Université de Haute Alsace - Mulhouse, 2013. http://tel.archives-ouvertes.fr/tel-01064374.

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La catalyse solide acide a été pendant longtemps l'objet d'activité de recherche intense, en particulier pour l'industrie pétrochimique. Aujourd'hui, les catalyseurs solides acides sont de plus en plus étudiés dans d'autres domaines et en particulier dans celles liées à la "chimie verte" et à la valorisation des bioressources, telles que la synthèse de biodiesel et la transformation des polysaccharides. L'objectif de la thèse est d'étudier le potentiel des matériaux poreux sulfonés ayant une porosité contrôlée dans des réactions catalysées par un acide en condition eau surchauffé telle que l'hydrolyse de la cellobiose. Dans une première partie, nous décrivons la préparation et la caractérisation des organosilicates mésoporeux périodiques sulfonés de type SBA-15, SBA-1 et KIT-6 par co-condensation de 1,4-bis (triéthoxysilyl) benzène (BTEB). Les matériaux ont été acidifiés suivant des voies différentes à l'aide de 3-mercaptopropyltriméthoxysilane (MPTMS)/H2O2 ou d'acide chlorosulfonique (ClSO3H). Leur propriété acide a été étudiée par adsorption d'NH3 suivie par calorimétrie et par la réaction de déshydratation d'isopropanol (IPA) comme réaction modèle en phase gazeuse. Contrairement à notre attente, l'adsorption d'NH3 suivie par calorimétrie a mis en évidence l'hétérogénéité de la force des sites suggérant la présence de sites distincts de la sulfonation. Les solides sulfonés avec l'acide chlorosulfonique ont une activité équivalente à celle de la résine sulfonée, Amberlyst 15, mais ils sont moins stables en raison de la libération des espèces de soufre. Les catalyseurs préparés en utilisant un groupement mercapto-propyle suivie d'une oxydation sont moins acides et ils ont donné des niveaux d'activité plus basse dans la réaction de déshydratation d'IPA. Pour l'hydrolyse de la cellobiose, de bonnes performances ont été obtenues à 150°C, mais, ces matériaux se sont montrés instables dans des conditions hydrothermales avec une lixiviation totale de soufre réalisant alors la réaction en phase homogène. Un lavage dans l'eau surchauffée des matériaux contenant des groupements propyles-SO3H conduit à une diminution de leur efficacité dans l'hydrolyse de la cellobiose, mais un gain de stabilité a été obtenu, permettant le recyclage de ces matériaux. Dans une deuxième partie, des répliques carbonées sulfonées par l'acide chlorosulfonique ou l'acide sulfurique ont été synthétisé. La sulfonation par l'acide sulfurique suivi par un lavage dans l'eau bouillante puis un prétraitement thermique à 300°C sous azote, de ces matériaux aboutissent au meilleur catalyseur en termes d'activité/stabilité.

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Rawat, Subhandu. "Dynamique cohérente de mouvements turbulents à grande échelle." Thesis, Toulouse, INPT, 2014. http://www.theses.fr/2014INPT0116/document.

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Mon travail de thèse a porté sur la compréhension «systèmes dynamiques de la dynamique à grande échelle dans l’écoulement pleinement développé de cisaillement turbulent. Dans le plan écoulement de Couette, simulation des grandes échelles (LES) est utilisée pour modéliser petits mouvements d’échelle et de ne résoudre mouvements à grande échelle afin de calculer non linéaire ondes progressives (SNT) et orbites périodiques relatives (RPO). Artificiel sur-amortissement a été utilisé pour étancher une gamme croissante de petite échelle motions et prouvent que les motions grande échelle sont auto-entretenue. Les solutions d’onde inférieure branche itinérantes qui se trouvent sur le bassin laminaire turbulent limite sont obtenues pour ces simulation sur-amortie et continue encore dans l’espace de paramètre à des solutions de branche supérieure. Cette approche ne aurait pas été possible si, comme supposé dans certains enquêtes précédentes, les mouvements à grande échelle dans le mur bornées flux de cisaillement sont forcée par un mécanisme fondé sur l’existence de structures actives à plus petite échelle. En flux Poseuille, orbites périodiques relatives à décalage réflexion symétrie sur la limite du bassin laminaire turbulent sont calculés en utilisant DNS. Nous montrons que le RPO trouvé sont connectés à la paire de voyager vague (TW) solution via bifurcation mondiale (noeud-col-période infinie bifurcation). La branche inférieure de cette solution TW évoluer dans un état de l’envergure localisée lorsque le domaine de l’envergure est augmentée. La solution de branche supérieure développe plusieurs stries avec un espacement de l’envergure compatible avec des mouvements à grande échelle en régime turbulent
My thesis work focused on ‘dynamical systems’ understanding of the large-scale dynamics in fully developed turbulent shear flow. In plane Couette flow, large-eddy simulation (L.E.S) is used to model small scale motions and to only resolve large-scale motions in order to compute nonlinear traveling waves (NTW) and relative periodic orbits (RPO). Artificial over-damping has been used to quench an increasing range of small-scale motions and prove that the motions in large-scale are self-sustained. The lower-branch traveling wave solutions that lie on laminar-turbulent basin boundary are obtained for these over-damped simulation and further continued in parameter space to upper branch solutions. This approach would not have been possible if, as conjectured in some previous investigations, large-scale motions in wall bounded shear flows are forced by mechanism based on the existence of active structures at smaller scales. In Poseuille flow, relative periodic orbits with shift-reflection symmetry on the laminar-turbulent basin boundary are computed using DNS. We show that the found RPO are connected to the pair of traveling wave (TW) solution via global bifurcation (saddle-node-infinite period bifurcation). The lower branch of this TW solution evolve into a spanwise localized state when the spanwise domain is increased. The upper branch solution develops multiple streaks with spanwise spacing consistent with large-scale motions in turbulent regime

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Nikolajtschuk, Pawel Anatoljewitsch [Verfasser], Aleksandr Georgiewitsch [Akademischer Betreuer] Türin, Fritz [Akademischer Betreuer] Scholz, Fritz [Gutachter] Scholz, and Su-Il [Gutachter] Pyun. "Thermodynamische Einschätzung der chemischen und elektrochemischen Stabilität von Siliziden der Übergangsmetalle der vierten Periode / Pawel Anatoljewitsch Nikolajtschuk ; Gutachter: Fritz Scholz, Su-Il Pyun ; Aleksandr Georgiewitsch Türin, Fritz Scholz." Greifswald : Ernst-Moritz-Arndt-Universität, 2019. http://d-nb.info/1177241528/34.

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Nikolajčuk, Pavel Anatol'evič [Verfasser], Aleksandr Georgiewitsch Akademischer Betreuer] Türin, Fritz [Akademischer Betreuer] [Scholz, Fritz Gutachter] Scholz, and Su-Il [Gutachter] [Pyun. "Thermodynamische Einschätzung der chemischen und elektrochemischen Stabilität von Siliziden der Übergangsmetalle der vierten Periode / Pawel Anatoljewitsch Nikolajtschuk ; Gutachter: Fritz Scholz, Su-Il Pyun ; Aleksandr Georgiewitsch Türin, Fritz Scholz." Greifswald : Ernst-Moritz-Arndt-Universität, 2019. http://nbn-resolving.de/urn:nbn:de:gbv:9-opus-24859.

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Nikolajčuk, Pavel Anatol'evič [Verfasser], Aleksandr Georgiewitsch Akademischer Betreuer] Türin, Fritz [Akademischer Betreuer] Scholz, Fritz [Gutachter] Scholz, and Su-Il [Gutachter] [Pyun. "Thermodynamische Einschätzung der chemischen und elektrochemischen Stabilität von Siliziden der Übergangsmetalle der vierten Periode / Pawel Anatoljewitsch Nikolajtschuk ; Gutachter: Fritz Scholz, Su-Il Pyun ; Aleksandr Georgiewitsch Türin, Fritz Scholz." Greifswald : Ernst-Moritz-Arndt-Universität, 2019. http://d-nb.info/1177241528/34.

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Jiménez, Manuel Francisco Zuloeta. "Propriedades recursivas em sistemas semidinâmicos impulsivos." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/55/55135/tde-18032014-162058/.

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A teoria de sistemas semidinâmicos impulsivos é um capítulo importante e moderno da teoria de sistemas dinâmicos topológicos. Sistemas impulsivos descrevem processos de evolução que sofrem variações de estado de curta duração e que podem ser consideradas instantâneas. Os sistemas impulsivos admitem vários fenômenos interessantes às vezes, por causa da sua irregularidade, e às vezes por causa da sua regularidade. Para muitos fenômenos naturais, os modelos determinísticos mais realistas são frequentemente descritos por sistemas que envolvem impulsos. Esta teoria vem sendo desenvolvida continuamente. O presente trabalho apresenta resultados originais sobre a teoria de conjuntos minimais, movimentos recorrentes, movimentos quase periódicos e fracamente quase periódicos, teoria de estabilidade de Lyapunov, teoria da quase estabilidade de Zhukovskij e, finalmente, a construção de trajetórias negativas para sistemas semidinâmicos com impulsos. Os resultados novos apresentados neste trabalho estão contidos em três artigos, dos quais dois já foram aceitos para publicação. Veja [13], [14] e [15]
The theory of impulsive semidynamical systems is an important and modern chapter of the theory of topological dynamical systems. Impulsive systems describe the evolution of process whose continuous dynamics are interrupted by abrupt changes of state. This kind of systems admits various interesting phenomena sometimes, because of their irregularity, and sometimes because of their regularity. In many natural phenomena, the real deterministic models are often described by systems which involve impulses. This theory has been developed continuously. This work presents original results involving the theory of minimal sets, recurrent motions, almost periodic and weakly almost periodic motions, the study of Lyapunov stability and Zhukovshij Quasi stability and the construction of negative trajectories for impulsive semidynamical systems. The new results presented in this work are contained in three papers namely [13], [14] and [15]

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Němeček, Martin. "Vliv vnitřní tepelné akumulace konstrukcí pasivních domů na jejich letní tepelnou stabilitu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-390267.

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In recent years we may observe a growth in construction of passive houses and low energy houses using lightweight constructions such as modern wooden houses. It is assumed that wooden houses keep overheating more comparing to brick houses during summer period. Due to the lack of research in this field the paper investigates the influence of internal thermal storage mass in passive houses constructions on their summer thermal stability under the Czech climatic conditions. Only sensible heat accumulation without a usage of phase change materials is examined. Differences between wooden houses comparing to brick-built houses are emphasized. Objects of research are mostly residential passive houses in low energy building standards. However, the results of research might be applied to different types of buildings as well. The first section outlines theoretical fundamentals. For the research itself various scientific research methods were used, such as basic mathematical calculations, experimental temperature measurement of two buildings (detached house in Dubňany and in Moravany) and numerical simulations. Own tribute to the research was first of all discussion on the topic of thermal accumulation and structures heat capacity calculation. Experimental measurements outlined conclusive evidence about the importance of internal thermal storage mass in respect of interior summer overheating. The research confirmed that the highest interior temperature reached is mostly influenced by solar gains through unshaded windows. However, the influence of internal thermal storage mass is not remote. If we compare standard timber-framed wooden house to the hole ceramic bricks-built house, the wooden house will overheat by 0,5°C more during a standard day. Wider spread in the maximum temperature reached was measured for lightweight consturctions wooden houses without any internal thermal storage mass. Therefore, such structures should have an additional layer of thermal storage mass.

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