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1
Aguilar, Acosta Milton Alberto, e Vara Juan Emilio Asto. "Modelo de Inteligencia de Negocios en la empresa “Contact Center JMT”". Master's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/655779.
Texto completo da fonteResumo:
La Empresa JMT Contact Center es una empresa que se dedica al rubro de Telemarketing, Centro de Contacto y Business Process Outsourcing, con presencia en los mercados de Europa y Latinoamérica. Es una empresa en constante crecimiento y en la actualidad a pesar de estar en medio de una Pandemia ha tenido el reto de enfrentar una demanda de crecimiento en los puestos de atención.
En los últimos años, la empresa ha tenido que enfrentar ciertos retos financieros ligado a los costos planificados y a los costos operativos, de tal forma que su rentabilidad como negocio se ha visto impactada, sumando a ello nuevas regulaciones y el efecto de la pandemia a nivel global.
El objetivo principal de la presente tesis es plantear un modelo de inteligencia de negocios para JMT Contact Center con la finalidad de reducir los costos operativos de la organización al mejorar la calidad de información utilizada en los procesos de planificación de operaciones, el discado dirigido y la categorización de perfiles de usuarios; para lo cual se analiza el contexto, se plantean los objetivos y se alinea la estrategia de inteligencia de negocios con los procesos existentes.
La propuesta de este modelo de inteligencia de negocios se enfoca especialmente en el uso efectivo de las herramientas del Business Intelligence para lograr una optimización de recursos y costos en la operación de las campañas Outbound del Centro De Atención Telefónica, de tal forma que estas se conviertan en rentables y eviten perdidas a la organización.The JMT Contact Center Company is a company dedicated to the Telemarketing, Contact Center and Business Process Outsourcing business, with a presence in the markets of Europe and Latin America. It is a company in constant growth and today, despite being in the middle of a Pandemic, it has had the challenge of facing a demand for growth in service positions. In recent years, the company has had to face certain financial challenges related to planned costs and operating costs, in such a way that its profitability as a business has been impacted, adding new regulations and the effect of the pandemic at the global. The main objective of this thesis is to propose a business intelligence model for JMT Contact Center in order to reduce the operational costs of the organization by improving the quality of information used in the operations planning processes, directed dialing and categorization of user profiles; for which the context is analyzed, objectives are set and the business intelligence strategy is aligned with existing processes. The proposal of this business intelligence model focuses especially on the effective use of Business Intelligence tools to achieve an optimization of resources and costs in the operation of the Outbound campaigns of the Call Center, in such a way that they become profitable and avoid losses to the organization.
Trabajo de investigación
2
Dumas, Louise. "Méthodologie de préparation d’échantillons et de lecture d’états logiques de cellules mémoires MRAM par microscopie à force atomique". Electronic Thesis or Diss., Bordeaux, 2025. http://www.theses.fr/2025BORD0009.
Texto completo da fonteResumo:
Dans le contexte de la sécurité de l'information, l’évolution des techniques de test électrique interne et leurs capacités à identifier et lire les données sensibles des technologies mémoires est un sujet crucial, leur veille technologique est donc nécessaire. Quelques études ont été réalisées sur la lecture des mémoires volatiles comme la SRAM et des mémoires non volatiles comme la Flash, la FeRAM et la RRAM. Malgré l’attrait des mémoires magnéto-résistives (MRAM), de par leur potentiel de devenir une mémoire universelle, une lecture directe des données au cœur du circuit MRAM n'a jamais été démontrée dans la littérature avant ce travail de thèse.Ce travail démontre qu’il est possible de récupérer les données stockées dans les MRAM grâce à des techniques invasives. Ce manuscrit présente la méthodologie développée pour lire les données stockées (“0” / “1”) dans une Toggle MRAM (nœud technologique de 130 nm) et dans une STT-MRAM (nœud technologique de 40 nm). Ces composants sont représentatifs des deux types de MRAM commercialisées avec des nœuds technologiques courants et plus avancés. Cette méthodologie est faite de quatre étapes : détermination de la technique de mesure la plus adéquate, analyse technologique pour connaître la structure physique de la mémoire, préparation de la mémoire pour rendre les données accessibles et lecture des données. Deux tentatives de lecture sont détaillées : mesure de l’orientation magnétique des jonctions magnétiques tunnel (dites JMT, lieu de stockage de l’information) et mesure de leur résistance électrique induite par le phénomène de magnétorésistance, à l’aide d’un microscope à force atomique (AFM) et du Nanoprobing. Les modes AFM utilisés sont le MFM (mode magnétique), le C-AFM (mode conducteur) et le SSRM (mode résistif). Pour les deux types de mémoires, c’est la mesure de courant en C-AFM qui permet de discriminer les deux états logiques. Celle-ci est réalisée après une préparation complexe de la face arrière du composant composée d’une ouverture chimique, d’un polissage jusqu’aux transistors, de gravures FIB de niveaux de métallisation entourant la JMT et d’un dépôt métallique. L’avantage de cette méthodologie est qu’elle devrait être applicable à tout nœud technologique et potentiellement à toutes les mémoires basées sur une valeur de résistance (SOT-MRAM, RRAM et PCM)In the context of information security, the evolution of internal electrical test techniques and their ability to identify and read sensitive data from memory technologies is a crucial matter, their technological watch is therefore necessary. A few studies have been carried out on the readout of volatile memories such as SRAM and non-volatile memories such as Flash, FeRAM and RRAM. Despite the attractiveness of magneto-resistive memories (MRAM), due to their potential to become a universal memory, a direct readout of data at the core of the MRAM circuit has never been demonstrated in the literature prior to this work.This work demonstrates that it is possible to retrieve data stored in MRAMs using invasive techniques. This manuscript presents the methodology used to recover stored data (“0” / “1”) in a Toggle MRAM (130 nm technology node) and in a STT-MRAM (40 nm technology node). These components thus represent the two types of MRAM on the market, with current and more advanced technology nodes. The methodology consists of four stages: determination of the most suitable measurement technique, technological analysis to identify the physical structure of the memory, preparation of the memory to make the data accessible, and reading of the data. Two readout attempts are detailed: measurement of the magnetic orientation of magnetic tunnel junctions (known as MTJs, where the information is stored) and measurement of their electrical resistance induced by the magneto-resistance phenomenon, using an atomic force microscope (AFM) and Nanoprobing. The used AFM modes are MFM (magnetic mode), C-AFM (conductive mode) and SSRM (resistive mode). For both memory types, it's the C-AFM current measurement that makes it possible to discriminate between the two logic states. This is achieved after a complex preparation of the backside of the device, consisting of a chemical opening, a polishing down to the transistors, FIB etches of metallization levels surrounding the MTJ and metal deposition. The advantage of this methodology is that it should be applicable to any technology node and potentially to all resistance-based memories (SOT-MRAM, RRAM and PCM)
3
Spiekermann-Hoff, Sarah, e Jana Korunovska. "Towards a value theory for personal data". Palgrave Macmillan, 2017. http://dx.doi.org/10.1057/jit.2016.4.
Texto completo da fonteResumo:
Analysts, investors and entrepreneurs have recognized the value of personal data for Internet economics. Personal data is viewed as the "oil" of the digital economy. Yet, ordinary people are barely aware of this. Marketers collect personal data at minimal cost in exchange for free services. But will this be possible in the long term, especially in the face of privacy concerns? Little is known about how users really value their personal data. In this paper, we build a user-centered value theory for personal data. On the basis of a survey experiment with 1269 Facebook users, we identify core constructs that drive the value of volunteered personal data. We find that privacy concerns are less influential than expected and influence data value mainly when people become aware of data markets. In fact, the consciousness of data being a tradable asset is the single most influential factor driving willingness-to-pay for data. Furthermore, we find that people build a sense of psychological ownership for their data and hence value it more. Finally, our value theory helps to unveil market design mechanisms that will influence how personal data markets thrive: First, we observe a majority of users become reactant if they are consciously deprived of control over their personal data; many drop out of the market. We therefore advice companies to consider user-centered data control tools to have them participate in personal data markets. Second, we find that in order to create scarcity in the market, centralized IT architectures (reducing multiple data copies) may be beneficial.
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Peters, Jacob R., Robert Keasling, Stacy D. Brown e Brooks B. Pond. "Quantification of Synthetic Cathinones in Rat Brain Using HILIC–ESI-MS/MS". Digital Commons @ East Tennessee State University, 2016. https://doi.org/10.1093/jat/bkw074.
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The abuse of synthetic cathinones, formerly marketed as “bath salts”, has emerged over the last decade. Three common drugs in this class include 3,4-methylenedioxypyrovalerone (MDPV), 4-methylmethcathinone (mephedrone), and 3,4-methylenedioxymethcathinone (methylone). An LC–MS/MS method has been developed and validated for the simultaneous quantification of MDPV, mephedrone, and methylone in brain tissue. Briefly, MDPV, mephedrone, methylone, and their deuterium-labeled analogs were subjected to solid phase extraction (SPE) and separated using an HILIC Silica Column. The HPLC was coupled to a Shimadzu IT-TOF (ion trap-time of flight) system with the electrospray source running in positive mode (+ESI). The method was validated for precision, accuracy, and extraction efficiency. All inter-day and intra-day % RSD (percent relative standard deviation) and % error values were less than 15% and extraction efficiency exceeded 80%. These conditions allowed for limits of detection of 1ng/mL for MDPV, and 5 ng/mL for both mephedrone and methylone. The limits of quantification were determined to be 5ng/mL for MDPV and 10 ng/mL for mephedrone and methylone. The method was utilized to evaluate the pharmacokinetics of these drugs in adult male rats following administration of a drug cocktail including MDPV, mephedrone, and methylone. All three compounds reached peak concentrations in the brain within 15 min. Although methylone and mephedrone were administered at the same dose, the peak concentration (Cmax) of mephedrone in the brain was significantly higher than that for methylone, as was the area under the curve (AUC). In summary, this quick and sensitive method for measuring synthetic cathinones may be used for future pharmacokinetic investigations of these drugs in target tissue.
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Hatak, Isabella, Rainer Harms e Matthias Fink. "Age, job identification, and entrepreneurial intention". Emerald, 2014. http://dx.doi.org/10.1108/JMP-07-2014-0213.
Texto completo da fonteResumo:
Purpose: The purpose of this paper is to examine how age and job identification affect entrepreneurial intention.
Design/methodology/approach: The researchers
draw on a representative sample of the Austrian adult workforce and apply binary logistic regression on entrepreneurial intention.
Findings: The findings reveal that as employees age they are less inclined to act entrepreneurially, and that their entrepreneurial intention is lower the more they identify with their job. Whereas gender, education, and previous entrepreneurial experience matter, leadership and having entrepreneurial parents seem to have no impact on the entrepreneurial intention of employees.
Research implications: Implications relate to a contingency perspective on entrepreneurial intention where the impact of age is exacerbated by stronger identification with the job. Practical implications: Practical implications
include the need to account for different motivational backgrounds when addressing entrepreneurial employees of different ages. Societal implications include the need to adopt an age perspective to foster entrepreneurial intentions within established organizations.
Originality/value: While the study corroborates and extends findings from entrepreneurial intention research,
it contributes new empirical insights to the age and job
- dependent contingency perspective on entrepreneurial
intention. (authors' abstract)
6
Salsman, John M. "THE RELATIONSHIP BETWEEN RELIGIOSITY AND PSYCHOLOGICAL DISTRESS: A SCALE DEVELOPMENT STRATEGY WITH THE SCL-90-R". Lexington, Ky. : [University of Kentucky Libraries], 2002. http://lib.uky.edu/ETD/ukypcps2002t00044/JMS-Thes.pdf.
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Christoph, Fuchs, Emanuela Prandelli, Martin Schreier e Darren W. Dahl. "All That Is Users Might Not Be Gold: How Labeling Products as User Designed Backfires in the Context of Luxury Fashion Brands". American Marketing Association, 2013. http://dx.doi.org/10.1509/jm.11.0330.
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An emerging literature stream posits that drawing on users rather than internal designers in new product creation may benefit firms because the resulting products effectively satisfy consumer needs. Four studies conducted in the context of the luxury fashion industry uncover an important conceptual boundary condition of this positive user-design effect. Contrary to extant research, the results show that being "close" to users does not help but rather harms luxury fashion brands. Specifically, the authors find that user design backfires because consumer demand for a given luxury fashion brand collection is reduced if the collection is labeled as user (vs. company) designed. The results further reveal the underlying rationale for this reversal: user-designed luxury products are perceived to be lower in quality and fail to signal high status, which results in a loss of agentic feelings for the consumer. The authors explore several strategies luxury brands can pursue to overcome this negative user-design effect. Finally, they find that negative outcomes of user design are attenuated for luxury fashion products that are not used for status signaling - that is, product categories of a luxury brand that are characterized by lower status relevance for the consumer. (authors' abstract)
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Leder, Garth Duncan. "Jet rates and new jet algorithms". Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624739.
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Friedmann, Miriam. "Early modern English fairs". E-thesis Full text (Hebrew University users only), 1997. http://shemer.mslib.huji.ac.il/dissertations/H/JMS/001497172.pdf.
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Feldman, Anna. "Discourse markers codification of 'Hearer-Old' information the Russian discourse marker ze and its English and Hebrew correlates /". E-thesis Full text (Hebrew University users only), 1999. http://shemer.mslib.huji.ac.il/dissertations/H/JMS/001497195.pdf.
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Doxsee, Drew. "A religious point of view a reinterpretation of Wittgenstein's philosophical task /". E-thesis Full text (Hebrew University users only), 2003. http://shemer.mslib.huji.ac.il/dissertations/H/JMS/001498781.pdf.
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Cerra, Gabriela. "Linguistic questions in Cicero's poetic translations from Greek into Latin". E-thesis Full text (Hebrew University users only), 2008. http://shemer.mslib.huji.ac.il/dissertations/H/JMS/001473305.pdf.
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Nir, Dina. "The negotiational self identifying and transforming negotiation outcomes within the self /". E-thesis Full text (Hebrew University users only), 2008. http://shemer.mslib.huji.ac.il/dissertations/H/JMS/001478708.pdf.
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Verhelst, Stephane. "La liturgie de Jérusalem à l'époque byzantine genèse et structure de l'année liturgique /". E-thesis Full text, 1999. http://shemer.mslib.huji.ac.il/dissertations/W/JMS/001481250.pdf.
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Shamir, Barhum Ruth. "Painting at a cinematic glance the New Museum in films of the 1980's and 1990's /". E-thesis Full text, 1999. http://shemer.mslib.huji.ac.il/dissertations/W/JMS/001489438.pdf.
Texto completo da fonteResumo:
Thesis (Ph.D.)--Hebrew University of Jerusalem, 1999.Not included -- the illustrated album and the video tape with visual examples from all films. Under the supervision of Dimitri Segal and Abraham Kampf. Includes bibliographical references.
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Maayan, Sagy. "Islam and the European legal systems the headscarf debate in France and Germany as case studies /". E-thesis Full text (Hebrew University users only), 2008. http://shemer.mslib.huji.ac.il/dissertations/H/JMS/001489455.pdf.
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Mangoubi, Claude. "Analytical and numerical problems in the computation of the flow of viscoelastic fluids". E-thesis Full text, 2008. http://shemer.mslib.huji.ac.il/dissertations/W/JMC/001491630.pdf.
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Tyagi, Ashok K. "Jet to jet impingement in a confined space". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30117.pdf.
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Sellas, Alexis B. "Ghost-Jet". FIU Digital Commons, 2011. http://digitalcommons.fiu.edu/etd/352.
Texto completo da fonteResumo:
GHOST-JET is a collection of poems rooted in the lyrical tradition, often juxtaposing images of the natural world--the human body, insects, the Florida terrain--against images of surrealism--ethereal spirits, monsters, dreamscapes--in order to create metaphorical leaps of the imagination. In these poems there is the world as we know it and the world on the peripheral--zombies and babies turning into crocodiles, portraying the anxieties of the contemporary world we face as parents, children, and citizens. Written primarily in free verse, the collection also contains more traditional forms: pantoum, sestina, and haiku. There are no section breaks in this collection. Instead, the poems alternate between the personal and the political; between the particular fears of parenting and the more abstract fears in a new, post-September 11th America; between the violence perpetuated by family members and violence committed by the unknown, faceless aggressors in the world around us.
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Klymenko, К., e L. M. Meleshkevych. "Jet pack". Thesis, КНУТД, 2016. https://er.knutd.edu.ua/handle/123456789/5047.
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Lee, Jit Sean. "Collaborations, board independence and website social impact disclosures: A study of social enterprises". Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/102847/4/Jit%20Sean%20Lee%20Thesis.pdf.
Texto completo da fonteResumo:
The thesis examines motivation behind the website social impact reporting practices of 102 social enterprises operating across 29 countries. To identify the motivation which determines the level and quality of disclosure, the thesis has applied stakeholder and collaboration theories to test the impact of board independence and collaborations with other organisations on disclosures. By using multiple regression analyses, the thesis has found that collaborations and board independence influence the quality and extent of disclosure at a significant level.
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Bylund, Patrick. "JMS communication : Communicating with a legacy JMS broker using JavaScript". Thesis, Mittuniversitetet, Avdelningen för informationssystem och -teknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-31078.
Texto completo da fonteResumo:
The objective of this thesis is to research how to use JavaScript to communicate with a legacy JMS broker, specifically OpenMQ 4.1 and implementing a proof- of-concept of this. This proof-of-concept should be able to send and receive JMS messages. The necessary preparations for designing this application was to research possible ways of communicating with different JMS brokers using oth- er languages than Java. This research showed that the only viable method in or- der to communicate with this version of OpenMQ is to create a Java bridge be- tween JavaScript and the JMS broker. The results shows that it's possible to use JavaScript to communicate with OpenMQ 4.1 by using a Java Bridge together with NodeJS. This result is performed by making an integration test, by first sending a message with a certain ID to the API and then receiving a response at the intended response destination with the same ID. The front-end of the proof- of-concept provides a web application UI for performing this integration test. Future improvements of this implementation can be done by extending the Java Bridge and API in such a way that it can be used against many different JMS brokers. The configuration data used can also be stored in more reliable ways, if multiple users are using the API and web application at the same time, for example by using a database instead of JSON files.
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Kiran, Amit. "Jet noise : aeroacoustic distribution of a subsonic co-axial jet". Thesis, University of Warwick, 2008. http://wrap.warwick.ac.uk/3914/.
Texto completo da fonteResumo:
The noise generated by aircraft can be easily heard by those living under the flight path of passenger or cargo carriers. It is considered an environmental pollutant and is treated as such by the International Civil Aviation Organization (ICAO) who monitor and review noise levels. The ICAO imposes substantial fines on those carriers who do not adhere to the decibel limitations. With the new limit or `stage' enforced in 2006, aircraft manufacturers (including jet engine manufacturers) are seeking ways to reduce the noise created by an aircraft. A 1/150th scale model, based on the exit geometry typically found on commercial jet engines, was designed and manufactured at Warwick. The laboratory jet flow conditions operated at 0.7 Mach. The work presented in this thesis looks at the noise generated in a subsonic, co- owing jet, with particular focus given to the distribution sound sources from 5 kHz to 80 kHz (0.375 St to 6.0 St). An acoustic mirror mounted on a motorized 3-way traverse measured radiated sound in the co-flowing jet to produce 2D sound source maps. This is done using combinations of smooth cowl and chevrons for the core and bypass nozzles. For frequencies less than 30 kHz, a reduction of noise was observed using the bypass chevron nozzle compared with the bypass smooth cowl nozzle. Laser Doppler Anemometry (LDA) was used to reveal the 2D flow dynamics of the jet, supporting the acoustic distribution results with velocity profiles of the flow. The change in the flow dynamics with different nozzle combinations is discussed and different regions of the flow were identified.
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Varley, Juliet. "Submerged jet oxygenation". Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334290.
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Lyu, Benshuai. "Installed jet noise". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273735.
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This thesis studies the prediction and reduction of installed jet noise, combining both analytical and experimental techniques. In the prediction part, it starts with formulating a low-order but robust isolated jet noise prediction model, based on which a remarkably fast code with pre-informed data is developed. A semi-empirical low-order model is then developed to predict installed jet noise. The model consists of two parts, the first of which is based on the Lighthill's acoustic analogy theory. The second part embraces Amiet's approach to model the sound due to the scattering of jet instability waves. It is shown that the significant low-frequency noise enhancement observed in installed jet experiments is due to the scattering of near-field instability waves. The trailing edge scattering model can successfully predict noise spectra at all distinct angles. The quadrupole-induced high-frequency sound is either efficiently shielded at $90^\circ$ to the jet axis on the shielded side or enhanced by around $3$ dB at $90^\circ$ on the reflected side. But these effects gradually diminish as the observer angle decreases. The high-frequency spectra can be robustly predicted at large observer angles while deviation occurs at low observer angles due to jet refraction effects. An experimental study on installed jet noise is then conducted. The effects of plate positions and Mach numbers are studied. Excellent agreement between the experimental results and model predictions is achieved at low frequencies for all plate positions and Mach numbers tested. At high frequencies, the noise spectra at $90^\circ$ on the reflected side can also be correctly predicted. At lower observer angles, deviations occur due to jet refraction effects. In the noise reduction part, an experimental study is firstly carried out to study the effects of lobed nozzles on installed jet noise at constant flow rates. It is found that lobed nozzles do not noticeably change the installed jet noise spectra at low frequencies. However, they do result in a slight noise reduction at high frequencies. To understand why lobed nozzles hardly change low-frequency installed jet noise, an analytical stability analysis for lobed vortex sheets is performed. The results show that lobed jets change both the convection velocity and the temporal growth rate of instability waves. The changes become more pronounced as the number of lobes $N$ and the penetration ratio $\epsilon$ increase. A second set of experiments is carried out to explore the possibility of reducing installed jet noise by using two pylons. The results show that even in the most conservative case installed jet noise is reduced by around $2\sim3$ dB at low frequencies. It is concluded that using two pylons to reduce installed jet noise has significant practical potential.
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Žwaková, Vendula. "Administrativní budova JmP". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226073.
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The subject of this Master’s thesis was recalculation and design two variants of existing supporting steel structure storey administrative building which is located in the complex of Jihomoravská plynárenská a.s. in the city center of Brno. Dimensions and disposition based on the specifications of the Master‘s thesis. The total height of the structure is 29.46 m and circular platform has a diameter of 16.088 m. The supporting structure of an existing building consists of circumferential lattice structure. The main supporting elements of both variants are columns. Option A has 8 columns. Option B has 16 columns. These two variants were preliminarily designed and statically evaluated. After that was made a comparison of variants, and one was selected for more detailed processing (Option A). This included the calculation of anchorage, draft of mounting joints, technical report and drawing documentation.
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Ritchie, Brian Douglas. "Quantitative Acetone PLIF Measurements of Jet Mixing with Synthetic Jet Actuators". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10536.
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Fuel-air mixing enhancement in axisymmetric jets using an array of synthetic jet actuators around the perimeter of the flows (primarily parallel to the flow axis) was investigated using planar laser-induced fluorescence of acetone. The synthetic jets are a promising new mixing control and enhancement technology with a wide range of capabilities. An image correction scheme that improved on current ones was applied to the images acquired to generate quantitative mixing measurements. Both a single jet and coaxial jets were tested, including different velocity ratios for the coaxial jets. The actuators run at a high frequency (~1.2 kHz), and were tested with all of them on and in other geometric patterns. In addition, amplitude modulation was imposed at a lower frequency (10-100 Hz).
The actuators generated small-scale structures in the outer (and inner, for the coaxial jets) mixing layers. These structures significantly enhanced the mixing in the near field (x/D less than 1) of the jets, which would be useful for correcting an off-design condition in a combustor. The amplitude modulation generated large-scale structures that became apparent farther downstream (x/D greater than 1). The impulse at the start of the duty cycle was responsible for creating the structures. The large structures contained broad regions of uniformly mixed fluid, and also entrained fluid significantly. In addition, highly asymmetric forcing geometries displayed the power of the actuators to control the spatial distribution of jet fluid. This spatial control is important for the correction of hot spots in the pattern factor.
In order to extend quantitative acetone PLIF to two-phase flows, the remaining unknown photophysical properties of acetone were identified. Tests showed that the technique could simultaneously capture acetone vapor and acetone droplets. A model of droplet fluorescence was developed, and applied to images acquired in a dilute spray. The sensitivity of the model to the value of the unknowns was evaluated, including a best and worst case. The results revealed that several liquid acetone photophysical properties must be measured for the further development of the technique, especially the phosphorescence yield. Quantitative two-phase acetone PLIF will provide a powerful new tool for studying spray flows.
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Loizides, Constantinos A. "Jet physics in ALICE". Stuttgart Ibidem-Verl, 2005. http://deposit.ddb.de/cgi-bin/dokserv?id=2672387&prov=M&dok_var=1&dok_ext=htm.
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Clements, Daniel Robert. "Jet physics at ATLAS". Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/365/.
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The use and optimisation of integration grid techniques to generate next-to-leading order predictions of jet cross-sections, independent of parton distribution functions, was investigated. Such methods were found to provide an accurate approximation to a standard Monte-Carlo simulation (within 1%) and enable collider data to be readily included in global PDF fitting procedures. However, the benefit of including inclusive-jet cross-section data from ATLAS in global fits is only significant if the jet energy scale (JES) can be constrained to ~1% at high pT. Uncertainties in the theoretical prediction of the inclusive-jet cross-section such as PDFs and fixed-order (scale) uncertainties were studied and compared with experimental errors arising from jet energy resolution and absolute scale. These uncertainties were then considered in the context of a quark compositeness search where a sensitivity to a compositeness scale of Lambda<10TeV can be achieved with 10 inverse femtobarns of data, if the jet energy scale can be constrained to ~1%. An analysis using dijet angular distributions found a similar sensitivity without the dependence on the jet energy scale. A potential method of evaluating the stability of the jet energy scale out to high pT by `bootstrapping' the calibration at low pT by the use of multi-jet events was also investigated. This suggests that a calorimeter non-linearity can be detected for jets with pT>500GeV at ~1.5%/500GeV (i.e. a 1.5% change in JES over 500GeV in pT). An investigation of inner-detector commissioning issues associated with the ATLAS Semiconductor Tracker (SCT), including a review of `noisy' modules on the SCT Barrel (from May 2007) was carried out. In addition a tool for DCS monitoring within the online monitoring framework was developed and tested during the M5 and M6 commissioning weeks. Finally, a method of assessing the track reconstruction efficiency by track-insertion was considered for the particular case of minimum bias events.
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Sanders, John E. "Jet dispersion in channels". Thesis, University of East London, 1998. http://roar.uel.ac.uk/1254/.
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This is an experimental and theoretical investigation of the dispersion of a round water jet discharging at various angles into a rectangular channel. A fundamental study of the jet is not only essential for a better understanding of the flow conditions produced by confined water jets but for a scientific approach to the design of hydraulic structures and to determine an efficient form of stilling basin for high velocity discharge from pipe outlets. The Laser Doppler Anemometry (LDA) technique was adapted for measurement of mean velocities and turbulence characteristics,, without any interference in the flow, and was utilised for the investigation of the complex three dimensional circulating flow which was experienced in the channel. In the experiments the inclination of the jet was varied from 45 to 90 degrees to the bed of the channel, while differing ratios of channel width and depth to jet diameter were studied for various Froude numbers. Detailed measurements of velocity decay, normal and lateral velocity profiles, distributions of pressure and turbulence characteristics have been carried out for selected flow conditions relating to the 45 degree oblique and vertical jet in order to determine the flow pattern and head dissipations. The experimental results have been analysed and compared with Glauert Is theory for a radial wall jet as a first approximation neglecting gravity forces when small compared with turbulent forces. Based on these results erosion experiments and model studies using a solid apron and a sand bed downstream, have been conducted to predict the minimum size of an efficient stilling basin and dimensions of any required blocks. Finally generalised design guide-lines and a standard code of practice have been developed for a stilling basin with high velocity pipe outlets. The research work will provide practical information and design procedures for consultants and other organisations working on the design and maintenance of a variety of water projects both in the UK and overseas.
31
Maurel, Agnès. "Instabilité d'un jet confiné". Paris 6, 1994. http://www.theses.fr/1994PA066771.
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Une etude experimentale et numerique est menee sur l'oscillation auto-entretenue d'un jet bidimensionnel dans une cavite rectangulaire. L'etude experimentale permet de preciser les differents regimes observes lorsque la vitesse d'entree du jet et la longueur de la cavite varient. Une etude plus detaillee du regime d'oscillations auto-entretenues est presentee. Elle met en evidence l'existence de modes (stages), caracterises par une longueur d'onde constante verifiant l=(n+1/4), ou l est la longueur de la cavite ; la valeur n selectionnee depend de la largeur d'entree du jet et de la vitesse d'entree du jet. Le mecanisme d'amplification presume est fonde sur un modele de synchronisation entre l'oscillation a la sortie de la cavite et les perturbations declenchees a l'entree du jet. L'etude numerique est menee sur une cavite carree (les simulations 2d sont effectuees avec le code de calcul nekton, fonde sur une methode d'elements finis spectraux) et s'attache a decrire l'instabilite proche du seuil. Une frequence fondamentale est degagee en regime lineaire et les non-linearites font apparaitre l'harmonique 2 et un mode stationnaire de frequence nulle ; elle modifie le motif de l'ecoulement moyen. Le developpement de cet ecoulement moyen est le mecanisme de saturation de l'instabilite oscillante: il stabilise les profils de vitesse. Une methode d'analyse en modes est presentee, qui tente de degager des grandeurs caracteristiques de l'instabilite. Les methodes d'exploitation des resultats des simulations sont applicables dans d'autres geometries et, en particulier, les resultats presentes dans cette these sont comparables a ceux mis en evidence dans des etudes numeriques du sillage
32
Hossain, Mohammad Arif. "Sweeping Jet Film Cooling". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586462423029754.
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Majerčin, Jakub. "Podnikatelský záměr - Business Jet". Master's thesis, Vysoká škola ekonomická v Praze, 2012. http://www.nusl.cz/ntk/nusl-162957.
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The aim of this thesis is to develop a business plan for the establishment of private airlines in the Czech Republic, based in Prague. The first part describes the theoretical part of the business plan. Its contents are facts that business plan should include, describes the practical meaning of this work and the reason for its assembly. Theoretical part describes in detail each part of the business plan and defines methods which are used in the practical part. The second part of this thesis deals with the transfer of theory into practical application. The practical part describes a preparation of the business plan, the establishment of private airlines. The content of the business plan is the executive summary, organizational structure, description of services offered, operation and analysis of competition and market. There are also accurately described activities of business, risk analysis and financial plan. The financial plan is created for five years in business and it has three possible variants of development. The conclusion contains a summary of the project and recommendations.
34
Bilgin, Murat. "Stationary and rotating hot jet ignition and flame propagation in a premixed cell /". Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9986.
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Ho, Chu Eu. "Turbulent fluid jet excavation in cohesive soil : with particular application to jet grouting". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32416.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Includes bibliographical references (p. 267-271).
This thesis reviews the jet grouting methodology, and the current state of practice and research. Current methods of prediction of jet grout diameters are highly empirical and site specific, and do not take into account the jet hydrodynamics and soil properties explicitly. A rational model to describe the jet excavation mechanism for cohesive soil is presented in this thesis, with the aim of providing an improved prediction tool that can be used in jetting design. The model is based on the assumption that the velocity distribution in the cutting jet is equivalent to that of a free jet with boundaries corresponding to the dimensions of the cavity excavated in the ground. The shape of the cavity formed depends on the erosional properties of the soil and jet expansion is limited by the resistance at the jet-soil interface. It is hypothesized that the shape of the cavity excavated follows the locus of the jet radius satisfying the condition of constant wall shear stress. The model predicts that the limit of jet penetration is reached when the dynamic pressure at the jet tip becomes equal to the ultimate soil bearing resistance. The model was validated by laboratory jetting tests, using soil specimens manufactured from powdered kaolin clay, cement and water. Cement-soil ratios (CSR) of 2.5 to 7.5% were used to produce specimens with undrained shear strength (Su) ranging from 5 to 45 kPa. A period of at least 3 days was allowed for the specimen to cure in the test tank before jetting was commenced. The tests were conducted using different nozzle diameters, jetting pressures, rotation speeds and soil strengths. The specimens were exhumed after completion of each test to map the shape of the cuts excavated.
(cont.) The insitu shear strength of the specimens was obtained using torvane and laboratory vane shear tests. Samples were also obtained for density and moisture content measurements. The experimental results showed that the measured and predicted shapes of cut were in reasonable agreement, with the predicted jet width being conservative in most cases. A strong linear correlation was found between jet penetration, nozzle diameter, nozzle pressure difference and soil bearing capacity. It was found that a bearing capacity coefficient (Sc) of 2.4 was applicable for failure at the jet tip. This value of Sc was corroborated by field trial data. Wall shear stresses back-calculated from the experiments were much smaller than the residual soil strengths obtained from laboratory vane shear tests and correspond more closely to the erosional strength of clays. The model enables the lift step of the jetting monitor to be computed directly. The present research demonstrated that valuable information regarding the excavation mechanism can be obtained by careful examination of the actual cut in a soil formed by a jet. It is recommended that further work be done to investigate the erosional process at the jet-soil interface and the properties of the grouted soil, using higher jetting pressures and soils with higher shear strengths. The effect of withdrawal rate on column formation and uniformity of mix is of interest. The brittleness of the grouted product and its effect on strength and deformation behavior is also important.
Chu Eu Ho.
Sc.D.
36
Monoté, Guy. "Atomisation d'un jet liquide par un jet de gaz coaxial : analyse du mélange". Poitiers, 1994. http://www.theses.fr/1994POIT2286.
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Cette etude contribue a la modelisation de la pulverisation d'un jet liquide par un jet de gaz coaxial. La configuration de jets diphasiques mise en place est une simulation de l'injection coaxiale generee avec de l'oxygene liquide lox et de l'hydrogene gazeux gh#2 dans le moteur cryotechnique vulcain de la fusee ariane v. La visualisation de jets d'eau ou de solutions aqueuses d'un tensioactif, assistes par des jets d'air, par l'intermediaire d'une nappe laser stroboscopee, fournit des photographies utiles a la comprehension de la structure des jets coaxiaux. Les mesures du taux de presence de liquide, effectuees au moyen d'une fibre optique, dans la zone dense des pulverisations, ont permis de mettre en evidence l'interaction entre les deux ecoulements adjacents. En particulier, elles montrent que le gaz penetre tres tot dans le liquide en formant une surface d'echange complexe. D'autre part, ces mesures ont rendu possible la classification des jets coaxiaux liquide/gaz en deux regimes d'ecoulement distincts, fonctions des conditions initiales d'injection. La mise en equation du taux de presence axial de liquide dans le voisinage de l'injecteur nous a conduit a proposer une correlation destinee a la prediction de la longueur de rupture du jet diphasique. Un analyseur de particules par la methode des phases doppler (pdpa) a servi a l'exploration de la zone diluee des jets. La taille des gouttes, leur vitesse axiale moyenne ou fluctuante ont ete determinees. Enfin, une premiere approche du bilan de masse montre que la zone centrale dense des jets coaxiaux se caracterise par un glissement entre les phases
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Smith, Matthew James. "The Analysis and Prediction of Jet Flow and Jet Noise about Airframe Surfaces". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23897.
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Aircraft noise mitigation has been an ongoing challenge for the aeronautics research community. In response to this challenge, aircraft concepts have been developed in which the
propulsion system is integrated with the airframe to shield the noise from the observer.
These concepts exhibit situations where the jet exhaust interacts with an airframe surface.
Jet flows interacting with nearby surfaces exhibit a complex behavior in which acoustic and
aerodynamic characteristics are altered. The physical understanding and accurate modeling
of these characteristics are essential to designing future low-noise aircraft. In this thesis,
an alternative approach is created for predicting jet mixing noise that utilizes an acoustic
analogy and the solution of the steady Reynolds-Averaged Navier-Stokes (RANS) equations
using a two equation turbulence model. A tailored Green's function is used in conjunction
with the acoustic analogy to account for the propagation effects of mixing noise due to a
nearby airframe surface. The tailored Green's function is found numerically using a newly
developed ray tracing method. The variation of the aerodynamics, acoustic source, and far-
field acoustic intensity are examined as a large flat plate is moved relative to the nozzle exit.
Steady RANS solutions are used to study the aerodynamic changes in the field-variables and
turbulence statistics. To quantify the propulsion airframe aeroacoustic (PAA) installation
effects on the aerodynamic source, a non-dimensional number is formed that can be used
as a basic guide to determine if the aerodynamic source is affected by the airframe and if
additional noise produced by the airframe surface is present. The aerodynamic and noise
prediction models are validated by comparing results with Particle Image Velocimetry (PIV)
and far-field acoustic data respectively. The developed jet noise scattering methodology is
then used to demonstrate the shielding effects of the Hybrid Wing Body (HWB) aircraft.
The validation assessment shows that the acoustic analogy and tailored Green's function
provided by the ray tracing method are capable of capturing jet shielding characteristics for
multiple configurations and jet exit conditions.Master of Science
38
Tipnis, T. J. "Effects of upstream nozzle geometry on rectangular free jets". Thesis, Depatment of Engineering Systems and Mangement, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/4557.
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This study is aimed at understanding the effects of changing the upstream nozzle geometry on the development of rectangular free jets. An existing converging rectangular nozzle with an exit aspect ratio of 4 and a circular inlet (AR4 nozzle) has been used as the basic configuration for this work. The study is primarily based on the results of numerical simulations wherein the internal geometry variation is accomplished by changing the inlet aspect ratio (AR,) and the length of the converging section, expressed as a ratio with respect to the length of the nozzle (called 'converging section ratio*, CSR); all the other parameters are kept constant. The results from LDA experiments done on the AR4 nozzle are presented and used as validation data for the CPD simulations. Analyses of the numerical results help in understanding the variation of the jet spreading for different combinations of AR, and CSR. Two parameters are identified for describing the jet development: the cross-over point (XC), defined as the location downstream of the exit where the jet half-velocity-widths (B) along the major and minor axes are equal, and the difference in the half-velocity-widths at 30 nozzle equivalent diameters (Dm) from the exit (AB30), to ascertain the occurrence of axis-switching. For a given AR,, XC varies linearly with CSR; the variation of XC is non-linear with AR, for a constant CSR. The A1330 variation is non-linear with both AR, and CSR; the other variable being kept constant. The data obtained from the simulations are further used to propose two parametric models which can be used to predict the occurrence of axis-switching, within the scope of this work. The parametric models are validated and future work is proposed.
39
Sivapragasam, M. "Numerical and experimental investigations on multiple air jets in counterflow for generating aircraft gas turbine engine inlet flow distortion patterns". Thesis, Coventry University, 2014. http://curve.coventry.ac.uk/open/items/0ad1d0c2-6693-4c6e-9224-5a2237862074/1.
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The performance of an aircraft gas turbine engine is adversely affected by the non-uniform or distorted flow in the inlet duct. Inlet flow distortion lowers the surge margin of the engine‟s compression system with surge occurring at much lower pressure ratios at all engine speeds. The compressor and/or engine are subjected to ground tests in the presence of inlet distortion to evaluate its performance. The simplest method of simulating inlet distortion during these tests is by installing a distortion screen ahead of the engine on the test bed. The uniform inlet flow to the compressor becomes nonuniform with total pressure loss after passing through the distortion screen. Though the distortion screens offer a number of significant advantages, they have some disadvantages. The air jet distortion system can alleviate many of the operational disadvantages encountered with the conventional distortion screens. The system consists of a number of air jets arranged in a circumferential array in a plane and issuing opposite to the primary air flow entering the engine. The jets interact with the primary stream and cause a local total pressure loss due to momentum exchange. The individual mass flow rates from the jets can be varied to obtain a required total pressure pattern ahead of the compressor at the Aerodynamic Interface Plane (AIP). A systematic study of the flow field of confined, turbulent, incompressible, axisymmetric jet issuing into counterflow is covered in this research programme. The jet penetration length and the jet width are reduced compared to unconfined counterflow and a linear relationship between the velocity ratio and the jet length ceases to be valid. The flow field of a circular compressible turbulent jet and then a system of four jets arranged circumferentially and issuing into a confined counterflow was studied experimentally and numerically. For the four jet system the mass flow rates in the four jets were equal in the first part of the study and in the second part they were unequal. The loss in total pressure due to the jet(s) interacting with the counterflow was quantified by a total pressure loss parameter λp0. The total pressure loss increased with increasing mass flow ratio. The total pressure loss distribution was evaluated at several locations behind the jet injector(s). The total pressure non-uniformity quantified by Distortion Index (DI) was found to be highest at a location just downstream of the jet injector and at far downstream locations low values of DI were observed. From the understanding gained with a single jet and four jets in counterflow a methodology was developed to generate a given total pressure distortion pattern at the AIP. The methodology employs computations to obtain the total pressure distortion at the AIP with quasi-one-dimensional inviscid analysis used as a starting point to estimate the mass flow rate in the jets. The inviscid analysis also provides a direction to the iterative procedure to vary the mass flow rate in the jets at the end of each computational step. The methodology is demonstrated to generate a given total pressure distortion pattern using four jets and is further extended to a larger number of jets, twelve and later twenty jets. The total pressure distortion patterns typical of use in aircraft gas turbine engine testing are generated accurately with a smaller number of jets than reported in the literature.
40
Trzebinski, Maciej. "Etude de la diffraction dans l'experience ATLAS au LHC". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00908126.
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Cette thèse porte sur l'étude de la diffraction avec le détecteur ATLAS au LHC. Après une brève introduction a la physique diffractive incluant la diffraction dure et molle, nous présenterons la production d'évènements "Jet-Gap-Jet" qui est particulirement intéressante pour tester les équations d'évolution de la Chromodynamique Quantique de Balitski Fadin Kuraev Lipatov. En utilisant des coupures permettant de sélectionner ce signal et une définition du "gap" basée sur la reconstruction des traces dans le détecteur interne d'ATLAS, nous observons un signal clair d'évènements "Jet-Gap-Jet" dans les données. A partir d'une taille de "demi-gap" de 0.8, les données ne peuvent pas être décrites de manière correcte en utilisant l'échantillon Monte Carlo des données de jets sans gap. Nous prouvons également que la production d'évènements "Jet-gap-Jet" avec les deux protons détectes dans AFP permet de réaliser un test propre de la théorie BFKL avec une luminosité de 300 pb-1. Dans la derniere partie de la these, nous presentons la production exclusive de jets et de pi+pi-. Apres la selection des donnes, le rapport signal sur bruit est de l'ordre de 5/9 (1/13) pour µ = 23 (46). Pour une luminosite integree respective de 40(300) fb-1 (pour un "pile-up" de 23(46)), cette mesure permettra d'etablir des contraintes sur les modeles theoriques dix fois plus precises qu'actuellement. La mesure de la production exclusive de pions en utilisant le detecteur ALFA permet de contraindre egalement les modeles exclusifs. Nous avons montre que les donnees accumulees par ALFA suffiront deja pour mesurer la section efficace de production et pour etudier differentes distributions comme la masse invariante du systeme pion-pion.
41
Belias, Anastasios. "Electron/jet discrimination and b-jet tagging at the second level trigger of ATLAS". Thesis, Royal Holloway, University of London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326090.
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Kim, Yongsun Ph D. Massachusetts Institute of Technology. "Study of jet quenching using [gamma]-jet events in heavy ion collisions at 2.76TeV". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83825.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.In title on title-page, "[gamma]" appears as the lower case Greek letter. Cataloged from PDF version of thesis.
Includes bibliographical references (pages 149-156).
The kinematic correlations of isolated-[gamma]+jet scatterings in proton-proton and lead-lead collisions at centre-of-mass energy of 2.76TeV per nucleon pair are studied for the investigation of the jet quenching phenomena in hot and dense QCD medium. The analysis uses collision data delivered by the LHC and recorded by CMS detector at CERN. The angular correlation, the transverse momentum ratio and the rate of mono-photon events are measured and their dependence on the collisional impact parameter is examined in lead-lead collision. The results of proton-proton collisions are used as the reference to which the lead-lead results are compared. Significant energy loss of jets induced by the hot and dense medium, and its gradual rise in correlation to the size of the medium are observed in lead-lead collisions, while a modification of the direction of jet axis is not detected.
by Yongsun Kim.
Ph.D.
43
Bernero, Stefano. "A turbulent jet in counterflow". [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=961718285.
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Nyblom, Per. "Designing a very light jet". Thesis, Mälardalen University, School of Innovation, Design and Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-4673.
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Introduction
Very light jet is a hot subject growing stronger and stronger. The new type of air craft is an air plane that weighs less than 10000 pounds and uses a jet engine.
Problem
The student was proposed to designing a conceptual very light jet that could be used for inspiration and accepted the challenge.
Method
In this thesis the reader can follow the project progress in detail, the proposed methods and the results. The student divided the project into four activities analysis, creation, development and documentation.
Result
The project ended with a concept very light jet with simple specifications. Illustrations for inspirational usage and a simulation testing for verification of the proposed concept specifications.
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Emanuelsson, Jörgen, Mona Karlsson e Benjamin Kibebe. "Strategiimplementering hos IT-företaget JMB". Thesis, Växjö University, School of Management and Economics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-1514.
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Syfte: Syftet med denna uppsats är att beskriva och analysera hur IT-företaget JMB gått tillväga för att implementera sin strategi samt att undersöka vilka faktorer som har varit viktiga för JMB:s strategiimplementering.
Avgränsningar: Vi har i studien avgränsat oss till ett fallföretag vilket innebär att strategiimplementering och faktorer i andra företag har inte beaktas. Vi har även avstått ifrån att fördjupa oss i utvärdering och uppföljning av strategin.
Metod: En fallstudie har genomförts på ett IT-företag, där vi har genomfört intervjuer på tre olika nivåer i organisationen. Utifrån den konceptuella modellen har det empiriska och teoretiska materialet analyserats.
Resultat, slutsatser: Svaret på frågeställningen är att JMB implementerar sin strategi genom att arbeta i en decentraliserad organisationsstruktur där företagets olika affärsområden får arbeta självständigt efter målstyrning samt ”empowerment”. Viktiga övergripande faktorer är organisationsstruktur och inflytande, ledarskap, organisationskultur, samt strategisk kontroll och förändring.
46
Solovev, Alexander Alexandrovich. "Catalytic Tubular Micro-Jet Engines". Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-92005.
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This dissertation offers demonstrations of autonomous catalytic microtubes (microjet engines) with tunable diameters ranging from micro- to nanoscale and lengths from 50 μm to 1 mm. These results open the door to effective microengines and represent the entry in the Guinness Book of World Records for “the smallest man-made jet engine.”
Several attractive methodologies of machine-based functions at the micro- and nanoscale are shown. For instance, catalytic Ti/Cr/Pt microjets, which are integrated on a planar substrate, can operate as “on chip” chemical micropumps by decomposition of hydrogen peroxide fuel into oxygen bubbles and water. When released from a substrate, microjets self-propel autonomously in solution. The incorporation of ferromagnetic layer (Fe) into the rolled-up geometry enables their remote control using external magnetic field. Such microjets were used to load, transport, deliver and assemble multiple cargo particles, including biological cells in bulk solutions and microfluidic channels. Furthermore, it is demonstrated that for microjets that are fixed to or self-propelled above a platinum patterned surface, the microengine power/speed can be controlled using a white lightsource. A change in intensity of the white light leads to a controllable switching “off” and “on” of the microengine power on demand. Light degrades a local concentration of the hydrogen peroxide fuel and surface tension and subsequently suppresses the generation of oxygen microbubbles.
In the next step, the diameter of the microjets was rigorously reduced to 250 nm by using hybrid heteroepitaxial/catalytic InGaAs/GaAs/Cr/Pt nanotubes. Due to asymmetry of the rolled-up layers, these nanojets move in corkscrew-like motions and act as “self-propelled nanotools,” which were used in the next step to transport yeast cells and drill into fixed cancer Hela cells. Although it is well-known that hydrogen peroxide cannot be used to sustain viable cellular function, it is however conceivable that alternative fuels, such as glucose, might enable operation of such nanotools under biologically compatible conditions. As a first step to achieve this goal, demonstrations were made using metal-enzyme biocatalytic Ti/Au/SAM/Catalase microengines.
Synthetic components with competing interactions are well-suited to study the emergence of their collective behavior, such as swarms of large numbers of individuals. Microengines’ self-organization in bistable swarms is shown at the air-liquid interface of the mixture of propylene carbonate and hydrogen peroxide. Microengines act as “water striders.” Buoyed by oxygen bubbles, they self-propel via the microbubble recoiling mechanism and, depending on the bubbles’ sizes, self-organize into swarms due to the meniscus climbing effect. These reversible swarms depend on the microengine power, which competes against attracting surface tension force.
The demonstrated microjet engines show great promise for emerging applications, including biomedical, on-chip, environmental, and robotic micromachines. Furthermore, a key method discovered, entitled “rolled-up nanotechnology on polymers,” allowed for the fabrication of highly parallel arrays of microtubes with multiple functionalities and aimed for different purposes.
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Williams, John Charles. "Water ingestion in jet engines". Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/265455.
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Civil aircraft engines are required to operate reliably in a variety of inclement weather situations. Ingestion of airborne water has been found to cause problems for certain engine types, particularly during aircraft descent at low engine power settings. The effects of water ingestion under these engine operating conditions are not well understood. It is believed that the engine pe1formance is largely dete1mined by the behaviour of liquid water in the core compression system. A programme of experimental and theoretical research has therefore been undertaken to investigate the effects of water ingestion on an axial flow compressor operating at low speed, in isolation from other engine components. Experimental studies have been conducted using a low-speed, four-stage axial flow laboratory compressor, modified to facilitate injection of water through spray nozzles fitted at the inlet. In the process, new methods were developed for the reliable measurement of static pressure in a wet environment. Compressor pe1formance changes were quantified by measming the overall total-to-static pressure-rise characteristic and the torque requirement. Initiation of water ingestion was shown to move the compressor operating point on the characteristic to a new position at reduced pressure rise and reduced air mass flowrate, and to increase significantly the torque requirement. In some cases, it was shown that initiation of water ingestion would lead to rotating stall. Experiments were conducted to investigate the effects of water-to-air mass flowrate ratio, droplet size and spray coverage. The spray coverage is the fraction of the compressor inlet area over which the water is distributed. This was determined principally by the divergence (or spray) angle of the water emerging from each nozzle. The results suggest that droplet size is relatively unimportant in determining the performance with water ingestion. The spray coverage is, however, important, with small spray coverage resulting in little or no loss of compressor surge margin and large spray coverage resulting in significant loss. The pe1formance of the first compressor stage is c1itical in explaining these differences in behaviour. Theoretical studies were conducted with the aim of predicting the spatial disttibution of liquid water inside a compressor. New models were developed for key aspects of liquid water behaviour and incorporated into a computer program. Droplet velocity (or momentum) is often found to play an important role in determining the water behaviour. Theories are suggested to explain the experimentally observed effects of water ingestion, drawing on insight gained from both the expe1imental and theoretical results. Compressor modifications that may reduce the adverse effects of water ingestion are then suggested. These comprise, firstly, the removal of water from the casing immediately upstream of the compressor and, secondly, the application of a "non-stick" coating to the blades of the first rotor blade row.
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Lowry, Christopher Graham. "Plasma-limiter interactions on JET". Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392350.
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Joslin, Evelyn. "Jet spectroscopy of aromatic molecules". Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261303.
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Babaei, Lavasani Mohammad R. "Ink-jet printing of textiles". Thesis, University of Manchester, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488155.
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