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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

Mesure des fonctions de fragmentation des jets et de leurs moments dans les collisions pp à Vs = 2.76 TeV avec ALICE au LHC / Measurement of jet fragmentation functions and of their moments in pp collisions at Vs = 2.76 TeV with ALICE at the LHC

Wang, Mengliang 10 December 2016 (has links)
Un cross-over entre la matière nucléaire ordinaire et le plasma de quarks et gluons (PQG) est prédit par la QCD sur réseau à bas PB et haute température. Expérimentalement les collisions d'ions lourds ultrarelativistes sont utilisées pour étudier cet état dense et chaud. Produits lors d'un processus dur en début de collision, un parton de grande énergie en perd dans le milieu avant de fragmenter en une gerbe de hadrons appelée jet. Une étude de la modification de la structure et de la fragmentation du jet dans le milieu par rapport au vide permet d'améliorer notre connaissance du PQG. Les fonctions de fragmentation (FF) d'un jet décrivent les distributions en impulsion des hadrons dans ce dernier. Dans les collisions proton-proton (pp), leur mesure est importante pour comprendre les mécanismes de fragmentation de partons. Dans les collisions noyau-noyau, elle permet d'étudier les mécanismes de perte d'énergie. Cependant, la présence d'un important bruit de fond qui fluctue rend la mesure complexe. Il a alors été suggéré de mesurer les moments des FF qui y seraient moins sensibles. Le détecteur ALICE au LHC a des capacités de trajectométrie uniques permettant la mesure des particules chargées jusqu'à des impulsions de 150 MeV/c rendant possible une étude fine de la structure du jet et de ses FF. Les calorimètres électromagnétiques (EMCal et DCal) peuvent aussi être utilisés pour améliorer la mesure de l'énergie du jet. Nous présentons les mesures des FF des jets chargés et les premières études des moments des FF dans les collisions pp à .s=2.76 TeV dans ALICE. Une partie du travail est aussi dédiée à l'implémentation de la géométrie de DCal dans le logiciel d'analyse. / A cross-over between ordinary nuclear matter and a state of deconfined quarks and gluons, the Quark Gluon Plasma (QGP), is predicted by lattice QCD at low PB and high temperature. Experimentally, ultra-relativistic heavy ion collisions are used to produce and to study the hot and dense QGP medium. Produced in a hard scattering at the early stage of the collision a highly energetic parton is expected to lose energy in the medium before fragmenting into a spray of hadrons called jet. A study of the modification of the jet structure and of its fragmentation pattern in medium compared to the vacuum case should provide insights into the QGP properties. The jet fragmentation functions (FF) describe the momentum distribution of hadrons inside a jet. In proton-proton (pp) collisions their measurement is important for understanding the mechanisms of parton fragmentation while it can shed light on the energy loss mechanisms in nucleus-nucleus (AA) collisions. However, the presence of a large fluctuating background in AA makes the measurement a challenging task. The use of FF moments has been proposed to overcome this difficulty. The ALICE detector at the LHC has unique tracking capabilities enabling to measure charged particles down to transverse momenta of 150 MeV/c. This allows assessing possible modifications of the jet structure and FF. The electromagnetic calorimeters (EMCal and DCal) can also be used to improve the measurement of the jet energy. We present the measurements of charged-jet FF and the first studies of FF moments in pp collisions at .s=2.76 TeV in ALICE. Part of the work is also dedicated to the implementation of the DCal geometry in the ALICE offline software.
252

Framing for Change : Effects of Message Framing on Attitudes Towards Personal- and Societal Climate Change Mitigation Efforts

Widlund, Johannes January 2016 (has links)
This study has made use of an experimental method to investigate if and how exposure to an integrated 'socioeconomic- and climate justice' framing, and a 'catastrophe' framing, alter Swedish post highschool students attitudes towards climate change mitigation efforts, both on a personal- and societal level. The experiment was conducted through 287 surveys where equal shares of the respondents were given different stimuli through a short text at the beginning of the surveys. Results indicate that contrary to the hypotheses, exposure to the 'catastrophe' frame had a larger and more positive effect on especially attitudes towards personal climate change mitigation efforts, but also to some extent on societal efforts, than did exposure to a 'justice' framing. This is possibly due to the salience of catastrophe framings in the Swedish public discourse, and /or the integrated approach the educational system has taken on the subject of sustainable development.
253

Experimenty jako nedílná součást výuky chemie / The experiments as integral part to chemical education

Karlínová, Markéta January 2017 (has links)
No description available.
254

Infrastructure design for evolvability : theory and methods

Biesek, Guilherme January 2013 (has links)
The development of new infrastructure invariably requires massive capital investments, take many years to design and deliver, and are expected to operate for several decades. During delivery and operational lifetime, the functional requirements are likely to change. To make the assets economically adaptable to foreseeable changes, sizeable investments in design flexibility may be required upfront. Under uncertainty about the future and tight budgets, multi-stakeholder teams must trade-off additional investments in flexibility with more affordable investments in rigid designs at risk of costly adaptation. How to help project teams bridge their divergences and coalesce their views of the world into a project strategy is the core question at the heart of this research. After reviewing the limitations of current practice and theory in the management of capital projects, this study turns to real options reasoning. By definition, investments in design flexibility can be equated with buying options: if the future resolves favourably, the options can be exercised to adapt the design economically. To advance theory and practice on capital design for evolvability, this study combines case-based with experimental work. First, an exploratory study reveals that, despite using options thinking, project teams find real options mathematical models inadequate to support mundane design decisions. A subsequent study on design practices at Network Rail shows the difficulties of designing for evolvability become amplified with multiple stakeholders. With asymmetry in capabilities, knowledge, and power to influence decisions, multi-stakeholder teams systematically resort to a combination of informal options thinking and ‘money talks’ to resolve concept design. Tensions flare up whenever stakeholders demanding investments in design flexibility cannot fund them. These findings suggest that a formal procedure to design for evolvability can offer a superior approach at front-end strategizing. To test this proposition, this research develops an original proof-of-principle of a formal design for evolvability framing that cross-fertilizes literature on project risk management and real options theory with insights from the fieldwork. It also develops a two-group experiment – grounded on fine-grained empirical data from a real-world rail station project – to compare the performance of the experimental and control groups in terms of effectiveness, efficiency, and satisfaction. The results show that a formal design for evolvability framing can improve front-end strategizing. As project teams become more efficient, they have more time to effectively resolve the design for evolvability strategy. Importantly, teams are unlikely to reject attempts to formalize the decision-making process. The study also shows that a formal design for evolvability strategy can improve the accountability of decision-makers for investments in design flexibility. Final considerations discuss the generalizability and limitations of these insights, and future directions.
255

On the classification and selection of orthogonal designs

Weng, Lin Chen 03 August 2020 (has links)
Factorial design has played a prominent role in the field of experimental design because of its richness in both theory and application. It explores the factorial effects by allowing the arrangement of efficient and economic experimentation, among which orthogonal design, uniform design and some other factorial designs have been widely used in various scientific investigations. The main contribution of this thesis shows the recent advances in the classification and selection of orthogonal designs. Design isomorphism is essential to the classification, selection and construction of designs. It also covers various popular design criteria as necessary conditions, such connection has led to a rapid growth of research on the novel approaches for either detecting the non-isomorphism or identifying the isomorphism. But further classification of non-isomorphic designs has received little attention, and hence remains an open question. It motivates us to propose the degree of isomorphism, as a more general view of isomorphism, for classifying non-isomorphic subclasses in orthogonal designs, and develop the column-wise identification framework accordingly. Selecting designs in sequential experiments is another concern. As a well-recognized strategy for improving the initial design, fold-over techniques have been widely applied to construct combined designs with better property in a certain sense. While each fold-over method has been comprehensively studied, there is no discussion on the comparison of them. It is the motivation behind our survey on the existing fold-over methods in view of statistical performance and computational complexity. The thesis involves five chapters and it is organized as follows. In the beginning chapter, the underlying statistical models in factorial design are demonstrated. In particular, we introduce orthogonal design and uniform design associated with commonly-used criteria of aberration and uniformity. In Chapter 2, the motivation and previous work of design isomorphism are reviewed. It attempts to explain the evolution of strategies from identification methods to detection methods, especially when the superior efficiency of the latter has been gradually appreciated by the statistical community. In Chapter 3, the concepts including the degree of isomorphism and pairwise distance are proposed. It allows us to establish the hierarchical clustering of non-isomorphic orthogonal designs. By applying the average linkage method, we present a new classification of L 27 (3 13 ) with six different clusters. In Chapter 4, an efficient algorithm for measuring the degree of isomorphism is developed, and we further extend it to a general framework to accommodate different issues in design isomorphism, including the detection of non-isomorphic designs, identification of isomorphic designs and the determination of non-isomorphic subclass for unclassified designs. In Chapter 5, a comprehensive survey of the existing fold-over techniques is presented. It starts with the background of these methods, and then explores the connection between the initial designs and their combined designs in a general framework. The dictionary cross-entropy loss is introduced to simplify a class of criteria that follows the dictionary ordering from pattern into scalar, it allows the statistical performance to be compared in a more straightforward way with visualization
256

The Importance of Failure, Experiment, and Success for Organizational Learning from Experience

Steppe, Jessica Annalena 25 August 2021 (has links)
No description available.
257

Studium turbulence plazmatu tokamaku pomocí reciprokých sond / Studium turbulence plazmatu tokamaku pomocí reciprokých sond

Ondáč, Peter January 2014 (has links)
This thesis deals with the study of turbulence in tokamak plasma and im- provement of an computer model ESEL. The first chapter deals with the theory related to the study of turbulence in the plasma. For the study of these tur- bulences the results of the probe measurements on the ASDEX Upgrade and COMPASS tokamak and model results from a computer model of the turbulent ESEL are used. The second chapter describes the used probes and the third chapter describes the model ESEL. Contribution of the work is mainly in the fourth and fifth chapter, which summarize the results of the comparisons be- tween the experimental data and model ESEL. The sixth chapter summarizes the most important conclusions from these comparisons. Some agreements and discrepancies were shown. One of the main results of the thesis is the impor- tance of one extra term in one governing equation of the ESEL, which means its improvement. However at present the ESEL is still not able to fully describe the tokamak plasma boundary. 1
258

Improving Understanding of Liquid Viscosity Through Experiments and Prediction

Passey, Jeremy W. 05 April 2021 (has links)
Liquid viscosity is an important thermophysical property in process design. While liquid viscosity has been studied for over a century, much has been left unexplored. The behavior of liquid viscosity between the melting point and normal boiling point are well established, but yet there is a lack of experimental data – with only 52% of the compounds in the 801 DIPPR database having experimental liquid viscosity data – and inadequate prediction methods. This project was able to measure liquid viscosity for 30 organic compounds to help fill in the gap in the 801 DIPPR database. The measured results also helped reiterate the need to examine family trends when looking at thermophysical properties. Prediction method shortcomings are briefly discussed when evaluating measured liquid viscosity data. A QSPR model developed by Gharagheizi is tested using liquid viscosity data from the 801 DIPPR database and found to be nonreplicable. A new QSPR model for predicting liquid viscosity at 298.15 K based on chemical family is developed and proven to be a promising starting point for future work.
259

New High-Sensitivity Searches for Neutrons Converting into Antineutrons And/or Sterile Neutrons at the HIBEAM/NNBAR Experiment at the European Spallation Source

Addazi, A., Anderson, K., Ansell, S., Babu, K. S., Barrow, J. L., Baxter, D. V., Bentley, P. M., Berezhiani, Z., Bevilacqua, R., Biondi, R., Bohm, C., Brooijmans, G., Broussard, L. J., Cederc ll, J., Crawford, C., Dev, P. S.B., Dijulio, D. D., Dolgov, A. D. 01 July 2021 (has links)
The violation of baryon number, is an essential ingredient for the preferential creation of matter over antimatter needed to account for the observed baryon asymmetry in the Universe. However, such a process has yet to be experimentally observed. The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source to search for baryon number violation. The program will include high-sensitivity searches for processes that violate baryon number by one or two units: free neutron-antineutron oscillation via mixing, neutron-antineutron oscillation via regeneration from a sterile neutron state , and neutron disappearance (n → n′); the effective process of neutron regeneration is also possible. The program can be used to discover and characterize mixing in the neutron, antineutron and sterile neutron sectors. The experiment addresses topical open questions such as the origins of baryogenesis and the nature of dark matter, and is sensitive to scales of new physics substantially in excess of those available at colliders. A goal of the program is to open a discovery window to neutron conversion probabilities (sensitivities) by up to three orders of magnitude compared with previous searches. The opportunity to make such a leap in sensitivity tests should not be squandered. The experiment pulls together a diverse international team of physicists from the particle (collider and low energy) and nuclear physics communities, while also including specialists in neutronics and magnetics.
260

Intraspecific Interference Among Larvae in a Semivoltine Dragonfly Population

Crowley, P. H., Dillon, P. M., Johnson, D. M., Watson, C. N. 01 February 1987 (has links)
This study focuses on ways that the size distribution of individuals influences the types and intensities of competitive interactions within a population of aquatic arthropod predators. Three field experiments and one laboratory experiment were designed to test for feeding interference, interference mortality, and dispersal effects within and between larval size classes of the primarily semivoltine dragonfly Tetragoneuria cynosura in Bays Mountain Lake. One field experiment documented the temporal pattern of colonization of large-mesh cylinders by the small, first-year-class larvae during a 30-day period; the results are consistent with passive (density-independent) colonization. A second field experiment examined the effect of large, second-year-class larvae at densities of 1 or 3 per cylinder (14 or 42 m-2) on colonization by small larvae; this colonization was inhibited at the high density of large larvae. In the laboratory experiment, when larvae of the two size-classes were together in the same aquarium, small larvae moved around less than when by themselves (dispersal inhibition). Thus the inhibition of colonization observed in the field may result from interference mortality, rather than from a flight response to the presence of larger conspecifics. To evaluate this interpretation, the third field experiment measured the in-situ functional response of large larvae to each other and to their small conspecific prey. Results suggest a type 1 (linear) functional response, with feeding inteference among large larvae. Moreover, the interference mortality inflicted by larger larvae on smaller conspecifics was apparently more intense on larger individuals within the small size-class. Taken together, the three field experiments and a statistical power analysis show how colonization and interference interact to determine the local density of small larvae, and why such interference effects are difficult to detect experimentally in the field.

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