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Murtagh, Daniel James. "Positron impact ionization phenomena." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1446030/.
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In the present work, a beam of positrons, obtained from a radioactive source (MNa) in conjunction with a W moderator and guided by a magnetic field, has been used to investigate low energy positron-impact ionization phenomena from atomic and molecular targets. For He below threshold, the investigation discovered vacuum contaminants in creased with gas load and hence concluded that the high 7-ray/ion signal observed by Szluinska and Laricchia (2004a) in Ne could not be safely attributed to annihila tion. A detailed measurement of the total ionization cross-section for He has been performed from below threshold for Ps formation to high energy. Combined with previously measured data and previously measured direct ionization cross-sections (Moxom et al 1996, Ashley et al 1996), a new determination of the positronium formation cross-section has been achieved and compared to other available experi mental measurements and theoretical calculations. Measurements of the excited state (n > 1) positronium formation cross-section for He and Ar have been performed and compared to available theoretical calcu lations. This work has been motivated both for a direct comparison with theory and to test the hypothesis that structure observed in the total (all n) positron ium formation cross-sections for the heavier noble gases, is due to excited state positronium formation (Laricchia et al 2002). The present study is unable to verify fully this hypothesis due to the experimental methods insensitivity to positronium formation in to the 2S or n > 2 states. However, the present results are close to the most sophisticated theoretical calculation of positronium formation into the 2P state (Campbell et al 1998).
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Wainwright, Raymond Geoffrey. "How do phenomena diagnosed as mental illness impact upon personal identity?" Thesis, Sheffield Hallam University, 2010. http://shura.shu.ac.uk/20832/.
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The central question of this study was to ascertain how phenomena diagnosed as mental illness impacted upon sense of personal identity. To facilitate the necessary research, the aims of this study were to examine the experience of mental illness from the perspective of service users. Nine adult respondents (five men, four women) participated in a series of unstructured interviews, each lasting approximately one and a half hours. Some respondents were interviewed twice. Data from the interviews were transcribed by the researcher and subjected to four levels of analysis. Of these levels, the first was the act of transcription, the second conclusions following same, the third close scrutiny of the transcribed document, and the fourth deconstruction into 'idea units'. Integral to this exercise was the use of narrative theory to develop concepts of the respondents' personal narratives with particular reference to the respondents' mental health narratives. Following the four levels of analysis, the personal narratives of the respondents were compared and contrasted in a cross-case analysis. With reference to narrative models developed for the specific purpose of this study, the conclusion was drawn that initial experience of mental illness has a profound effect upon the personal narrative. Thereafter, the resultant impact upon personal identity is influenced by a combination of personal and environmental factors. Some of these may lead to a re-evaluation of past experiences and associated understanding. Accordingly, the outcome of the illness experience may not necessarily be negative, but may be positive by virtue of insights gained. Implications for mental health practice and further research, including the personalisation agenda, are considered.
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Loken, Zach. "Law Enforcement Seat Belt Use: Impact of Policy and Phenomena on Use." ScholarWorks, 2019. https://scholarworks.waldenu.edu/dissertations/7402.
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Studies show that seat belt use by law enforcement officers is estimated to be at 50%, well below the national average. The purpose of this study was to explore what may be leading to reduced seat belt use by law enforcement patrol officers while also determining if different types of policies effect the level of seat belt usage by this population. The theoretical framework used in this study was Shafritz, Ott and Jang's theory of organizational culture and change. This quantitative study was conducted using a casual, quasi-experimental design; the research questions focused on understanding what phenomena may be occurring resulting in the lower seat belts by U.S. police patrol officers and what types of policies are resulting in increased seat belt usage by this population. Participants in this research consisted of 38 officers from police departments with patrol divisions. These departments were selected from the Phoenix Metropolitan Area. The research indicated that officers may have false perceptions in regard to seat belt use. Trainings should be delivered to debunk some of these myths while also providing practical seat belt use training. The results of this study can be used to develop better policies to increase seat belt usage by law enforcement officers, which would likely reduce the injuries and death as a result of auto accidents. Decreased injuries and deaths of law enforcement officers would lead to decreased insurance and workers' compensation claims that would reduce the tax and financial burden faced by citizens and jurisdictions.
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Daou, Maya Mounir. "Investigation of the plate-impact method as a precursor of physical phenomena and chemical processes." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066245/document.
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Ce manuscrit a pour but d'étudier un nouveau dispositif générateur de cavitation dont le potentiel favorable à l'intensification de réactions chimiques est évalué. Ce dispositif est constitué d'une plaque mobile qui frappe un liquide contenu dans un réacteur. L'impact génère une forte augmentation de pression dans le milieu suivi d'une dépressurisation. Nous montrons que la couche de gaz/vapeur piégée entre le piston et la surface du liquide influence les pics de pression et les fréquences générées dans le milieu. La visualisation à l'aide d'une caméra rapide montre que la dépressurisation active les sites de nucléation à l'origine des bulles de cavitation qui grandissent et implosent en générant occasionnellement des jets de grande vitesse. Nous étudions aussi la réponse de bulles préexistantes. Nous identifions un rayon de bulle critique qui dépend de la hauteur d'impact, de la pression extérieure et des caractéristiques du piston. Les bulles dont le rayon initial est supérieur à la valeur critique implosent au moment de l'impact, tandis que les petites bulles ne sont activées qu'après (sous tension). Des évolutions de pression différentes sont observées après l'impact en fonction de la présence/absence de grandes bulles. Nous étudions enfin l'oxydation du phénol en montrant que l'impact sur l'eau pure est incapable de générer des espèces radicalaires responsables de la dégradation. En ajoutant du peroxyde d'hydrogène comme oxydant, la molécule est décomposée sous certaines conditions. En général, la quantité d'oxydant requise pour déclencher une oxydation significative diminue lors de l'augmentation de l'intensité de l'impact sur lequel dépend le taux de dégradationThis manuscript aims at characterizing a new device based on a plate impact on a liquid surface to generate cavitation and evaluate its potential to induce chemical reactions. The device is composed of a reactor containing a liquid that a piston hits due to pressure difference. This impact generates a strong and uniform pressure increase in the medium followed by a depressurization. We show that the gas/vapor layer trapped between the piston and the liquid free surface influences the pressure peaks and frequencies generated in the medium. High-speed camera visualization shows that depressurization activates nucleation sites leading to bubble appearance in the solution. Bubbles expand and collapse intensively generating high velocity jets under some conditions. We also investigate the response of pre-existing bubbles. We identify a critical bubble radius that depends on the impact height, external pressure and piston’s characteristics. Bubbles with an initial radius larger than the critical one collapse at the moment of impact while smaller bubbles are only activated after it (under tension). Significant differences are observed in the pressure recordings after the impact depending on the presence/absence of large bubbles. We finally study the oxidation of phenol. We show that impacting on pure water is incapable of generating radical species responsible of the degradation. By adding hydrogen peroxide as an oxidant we show that the molecule is decomposed under certain conditions. In general, the amount of hydrogen peroxide required to initiate a significant oxidation decreases when increasing the intensity of the impact on which the degradation rate mainly depends
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Nadian, Behrooz. "A unified tribological model for different regimes of lubrication and rub/impact phenomena in rotor dynamics." Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1061913573.
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Jaeschke, Benedict. "Exploring phenomena that affect the fate and impact of radioactive materials in the blue mussel." Doctoral thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-83404.
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Current protection of the marine environment from radiation is based largely on measuring, estimating and modelling accumulation and impact(s) of radionuclides in a few marine species. Using a relevant marine organism, this thesis focusses on investigating some poorly described phenomena that could cause deviations from predicted measurements. Paper I investigated the biological transformation of tritium (radioactive hydrogen) into an organic compound. The resulting organically bound tritium (OBT) showed increased accumulation in mussels, unique incorporation into a key biological molecule (DNA), extended persistence in tissues, and greater toxicity than the inorganic form. Paper II demonstrated significant disparity in OBT accumulation between functionally similar microalgae species and that OBT in algae is readily transferred to a consumer. Highly radioactive particles are a complex issue in radioecology due to their concentrated dose geometry, potentially inducing very different impacts in organisms, compared to external irradiation. Paper III developed a method to introduce radioactive particles that would facilitate their recovery, improve dose-calculation, and aid the measurement of toxicological endpoints. It also showed that such particles can be incorporated into mussel tissues, causing significant effects. In Paper IV, hypoxia – another major ecological hazard in the marine environment – was expected to reduce radiosensitivity. The minimal observable effect from radiation prevented identification of such an interaction, and indicates drawbacks in the (otherwise sensitive) endpoints used. It appears that stressors like hypoxia may be more of a health hazard to marine organisms than environmental levels of ionising radiation. By understanding such causes of variation in accumulation and impact, it is possible to improve risk assessment, providing more justification for regulations chosen and minimising conservatism in setting environmental standards.At the time of doctoral defense, the following papers were not published and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.
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Adamović, Dragan. "Molecular dynamics studies of low-energy atom impact phenomena on metal surfaces during crystal growth /." Linköping : Department of Physics, Chemistry and Biology, Linköpings universitet, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7165.
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Chen, S. "An experimental investigation of drop impact phenomena with complex fluids on heated and soft surfaces." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3011893/.
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The present thesis is the result of a four year experimental research, which aims at studying the impact of non-Newtonian droplets (i.e., droplets of complex fluids such as polymer solutions) on heated surfaces (i.e., surfaces with a temperature above the Leidenfrost point) and soft surfaces (i.e., surfaces that undergo temporary or permanent deformations upon drop impact) through high-speed imaging. In the first year we focused on the Leidenfrost drop impact of different model fluids with matching flow curves. We demonstrate that the total kinetic energy carried by low-viscosity Newtonian drops during retraction is partly transformed into rotational kinetic energy rather than dissipated (published on Physical Review E, 2016). In the second year we extended the Leidenfrost drop impact experiment to viscoplastic fluids. The results show that the main contribution to drop rebound is due to surface forces rather than the elasticity of vapour cushion (published on Soft Matter, 2016). A systematic investigation on the impact of viscoplastic drops onto viscoplastic substrates was carried out in the third year. It is shown that the yield stress magnitude of drop/substrate strongly affects the final shape of the impacting drop (published on Soft Matter, 2017). The fourth year was devoted to the drop impact on spherical elastic surfaces. The dynamic contact angle measured using a novel digital image processing scheme is found to be significantly affected by the impact parameters and a quantitative estimation of the deformation energy is proposed (published on Physics of Fluids, 2017).
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Adamovic, Dragan. "Molecular Dynamics Studies of Low-Energy Atom Impact Phenomena on Metal Surfaces during Crystal Growth." Doctoral thesis, Linköpings universitet, Teoretisk Fysik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7165.
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It is a well-known fact in the materials science community that the use of low-energy atom impacts during thin film deposition is an effective tool for altering the growth behavior and for increasing the crystallinity of the films. However, the manner in which the incident atoms affect the growth kinetics and surface morphology is quite complicated and still not fully understood. This provides a strong incentive for further investigations of the interaction among incident atoms and surface atoms on the atomic scale. These impact-induced energetic events are non-equilibrium, transient processes which complete in picoseconds. The only accessible technique today which permits direct observation of these events is molecular dynamics (MD) simulations. This thesis deals with MD simulations of low-energy atom impact phenomena on metal surfaces during crystal growth. Platinum is chosen as a model system given that it has seen extended use as a model surface over the past few decades, both in experiments and simulations. In MD, the classical equations of motion are solved numerically for a set of interacting atoms. The atomic interactions are calculated using the embedded atom method (EAM). The EAM is a semi-empirical, pair-functional interatomic potential based on density functional theory. This potential provides a physical picture that includes many-atom effects while retaining computational efficiency needed for larger systems. Single adatoms residing on a surface constitute the smallest possible clusters and are the fundamental components controlling nucleation kinetics. Small two-dimensional clusters on a surface are the result of nucleation and are present during the early stages of growth. These surface structures are chosen as targets in the simulations (papers I and II) to provide further knowledge of the atomistic processes which occur during deposition, to investigate at which impact energies the different kinetic pathways open up, and how they may affect growth behavior. Some of the events observed are adatom scattering, dimer formation, cluster disruption, formation of three-dimensional clusters, and residual vacancy formation. Given the knowledge obtained, papers III and IV deal with growth of several layers with the aim to study the underlying mechanisms responsible for altering growth behavior and how the overall intra- and interlayer atomic migration can be controlled by low-energy atom impacts.On the day of the defence date the status of article II was Accepted.
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Uechi, Risa. "Modeling of Biological and Economical Phenomena Based on Analysis of Nonlinear Competitive Systems." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199432.
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Morales, Betancourt Ricardo. "On the representation of sub-grid scale phenomena and its impact on clouds properties and climate." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50373.
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This thesis addresses a series of questions related to the problem of achieving reliable and physically consistent representations of aerosol-cloud interaction in global circulation models (GCM). In-situ data and modeling tools are used to develop and evaluate novel parameterization schemes for the process of aerosol activation for applications in GCM simulations. Atmospheric models of different complexity were utilized, ranging from detailed Lagrangian parcel model simulations of the condensational growth of droplets, to one-dimensional single column model with aerosol and cloud microphysics, and finally GCM simulations performed with the Community Atmosphere Model (CAM). A scheme for mapping the sub-grid scale variability of cloud droplet number concentrations (CDNC) to a number of microphysical process rates in a GCM was tested, finding that neglecting this impact can have substantial influences in the integrated cloud properties. A comprehensive comparison and evaluation of two widely used, physically-based activation parameterizations was performed in the framework of CAM5.1. This was achieved by utilizing a numerical adjoint sensitivity approach to comprehensively investigate their response under the wide range of aerosol and dynamical conditions encountered in GCM simulations. As a result of this, the specific variables responsible for the observed differences in the physical response across parameterizations are encountered, leading to further parameterization improvement.
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Feng, Fabo [Verfasser], and Coryn [Akademischer Betreuer] Bailer-Jones. "Investigations into the impact of astronomical phenomena on the terrestrial biosphere and climate / Fabo Feng ; Betreuer: Coryn Bailer-Jones." Heidelberg : Universitätsbibliothek Heidelberg, 2015. http://d-nb.info/1180302729/34.
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Panzer, Fabian [Verfasser], and Anna [Akademischer Betreuer] Köhler. "Understanding the impact of order-disorder phenomena on the optical properties of photoactive semiconducting materials / Fabian Panzer ; Betreuer: Anna Köhler." Bayreuth : Universität Bayreuth, 2016. http://d-nb.info/1115250280/34.
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Oruganti, Pradeep Sharma. "Step Responses of a Torsional System with Multiple Clearances: Study of Vibro-Impact Phenomenon using Experimental and Computational Methods." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483033067455173.
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Carney, Melody Noelle. "The Impact of the Optical Phenomena of Color Adjustment Potential and Kubelka-Munk Layering of Dental Composite Resins on Modern Esthetic Dentistry." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429403504.
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East, Jackie R. "NATURAL PHENOMENA AS POTENTIAL INFLUENCE ON SOCIAL AND POLITICAL BEHAVIOR: THE EARTH’S MAGNETIC FIELD." UKnowledge, 2014. http://uknowledge.uky.edu/polysci_etds/11.
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Researchers use natural phenomena in a number of disciplines to help explain human behavioral outcomes. Research regarding the potential effects of magnetic fields on animal and human behavior indicates that fields could influence outcomes of interest to social scientists. Tests so far have been limited in scope. This work is a preliminary evaluation of whether the earth’s magnetic field influences human behavior it examines the baseline relationship exhibited between geomagnetic readings and a host of social and political outcomes. The emphasis on breadth of topical coverage in these statistical trials, rather than on depth of development for any one model, means that evidence is only suggestive – but geomagnetic readings frequently covary with social and political variables in a fashion that seems inexplicable in the absence of a causal relationship. The pattern often holds up in more-elaborate statistical models. Analysis provides compelling evidence that geomagnetic variables furnish valuable information to models. Many researchers are already aware of potential causal mechanisms that link human behavior to geomagnetic levels and this evidence provides a compelling case for continuing to develop the line of research with in-depth, focused analysis.
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Belhadj, Mariem. "Impact et optimisation des microporeux sur le vieillissement et la gestion en eau en pile à combustible." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0196/document.
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L’objectif de ce travail de thèse porte sur l’étude et la compréhension des phénomènes de la dégradation de la couche de diffusion des gaz. Ce composant de la PEMFC n’a pas été beaucoup discuté dans la littérature d’où le manque d’informations sur ses mécanismes de vieillissement. La dégradation physico-chimique en ex-situ de la GDL est tout d’abord étudiée par immersion et par voie électrochimique à fort potentiel. Plusieurs techniques d’analyses spectroscopiques, microscopiques et électrochimiques ont été utilisées dans le but de comprendre l’origine de cette dégradation. Les résultats de ces techniques montrent que les propriétés physico-chimiques de la GDL dépendent fortement des conditions opératoires des AST réalisés. La structure de la GDL a été gravement dégradée par voie électrochimique en particulier à 1,2 et 1,4 V vs. ECS. Cependant, l’immersion dans l’acide ou dans l’eau n’a pas réellement montré de changement au niveau de la morphologie et la structure par rapport à son état initial. Par contre, les résultats trouvés indiquent qu’indépendamment des conditions opératoires utilisées et contrairement à ce qui a été mentionné dans certaines publications, le PTFE des couches macro et microporeuse est relativement stable à la dégradation par comparaison aux composés carbonés. De plus, l’impact du vieillissement de la GDL sur la réponse de la pile étudiée par chronopotentiométrie, courbes tension vs. courant et spectroscopie d’impédance montrent une dégradation de la performance électrique de la pile à fortes densités de courant en particulier dans le cas des GDL dégradées à 1,2 et 1,4 V vs. ECS. Enfin, pour comparer les résultats des AST ex-situ à ceux d’un vieillissement in-situ, un cyclage dynamique de conduite, FCDLC, qui consiste en une variation du courant et de la tension de la pile sur un cycle de 1200 secondes, a été conduit pendant 1000 heures. Les résultats de ce cyclage montrent une dégradation de la surface active et une augmentation de la densité de courant de fuite. En contrepartie, ce FCDLC n’a pas beaucoup d’impact sur le vieillissement de la GDL par comparaison aux résultats trouvés des AST ex-situThe aim of this work is to understand the mechanism of gas diffusion layer degradation. Comparing to other PEMFC components, these layer has not been much discussed in the literature. First, in order to study ageing phenomena, ex-situ physico-chemical degradation of the GDL is carried out using acid and water immersion or electrochemical degradation at high potential. Several spectroscopic, microscopic and electrochemical techniques have been used to identify GDL degradation properties. The results of these experiments show that physicochemical properties of GDL depend strongly on the operating conditions of the ASTs produced. The structure of the GDL aged at 1.2 and 1.4 V vs. ECS has been severely changed. However, immersed GDL in acid or water did not actually show any change in morphology and structure compared to its initial state. On the other hand, the results obtained indicate that, independently of the operating conditions, and contrary to what has been mentioned in certain publications, the PTFE of the macro and microporous layers is relatively stable during AST compared to the carbon compounds. Moreover, the impact of aging of the GDL on the fuel cell response determined by chronopotentiometry, polarization curves and impedance spectroscopy show a degradation of the electrical performance of the cell, at high current density, in particular in the case aged GDL at 1.2 and 1.4 V vs. ECS. Finally, to compare ex-situ ASTs and in-situ aging impact, dynamic driving cycling, FCDLC, which consists of a variation of the current and the voltage of the fuel cell over a cycle of 1200 seconds, was conducted for 1000 hours. The result of the electrochemical characterization during cycling show that the active surface is degraded and the leakage current density is increased. However, this FCDLC does not affect the GDL properties compared to the results obtained with the ex-situ degradation experiments
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Aicheler, Markus [Verfasser], Gunther [Gutachter] Eggeler, and Werner [Gutachter] Theisen. "Surface phenomena associated with thermal cycling of copper and their impact on the service life of particle accelerator structures / Markus Aicheler ; Gutachter: Gunther Eggeler, Werner Theisen." Bochum : Ruhr-Universität Bochum, 2011. http://d-nb.info/1131354559/34.
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Richards, Kathryn H. "Mutations in the vpu and env Genes of HIV-1 Can Adversely Impact Infectivity: A Dissertation." eScholarship@UMMS, 2008. https://escholarship.umassmed.edu/gsbs_diss/378.
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The Human Immunodeficiency Virus (HIV) is able to infect CD4+ T cells as well as macrophages. Macrophage-tropism has been linked to determinants in the envelope of HIV. These determinants allow envelopes to exploit low levels of CD4 for infection. Macrophages are an important reservoir of virus, especially during chronic infection, and are likely responsible for the bulk of virus produced after CD4+T cells have declined. Viral factors that may impact the ability to infect macrophages are worth studying because this cell type is so important in infection.
It was previously reported that the macrophage-tropic primary isolate AD8 was vpu-independent. The molecular clone YU-2, derived from brain tissue without culture, was also reported to be macrophage-tropic despite having a mutation in the vpu start codon. It was therefore possible that vpu-independent envelopes could evolve in vivo. To examine this possibility, I constructed chimeras containing wild type or defective vpu start codons, and gp160 sequences from AD8, YU-2 or SF162 (a vpu-dependent control). I also used full length AD8 and YU-2 with wild type or defective vpu start codons. I infected macrophages with equal amounts of virus, and measured viral output over two weeks. Viruses with defective vpu start codons were released to lower levels compared to their wild type vpucounterparts. In contrast to previous reports, the AD8 envelope is not vpu-independent for replication in macrophages. The YU-2 envelope is also not vpu-independent.
Macrophage-tropic envelopes from late stages of infection can be sensitive to antibodies that bind the CD4 binding site on gp120, implying that macrophage-tropic envelopes have more exposed CD4 binding sites. Neutralizing antibodies may act as modulators of macrophage-tropism over the course of infection. Using chimeras containing gp120 sequences derived from the PBMC of four HIV+patients, I examined the capacity for envelopes to infect macrophages. Three patients (MM1, 4, and 8) had macrophage-tropic envelopes before and after developing autologous neutralizing antibodies. Three patients (MM1, 4, and 23) developed heterologous antibodies against IIIB, an easily neutralized T-cell line adapted strain of HIV-1. This data indicates that macrophage-tropism in these patients is not modulated by the presence of neutralizing antibodies.
The macrophage-tropism of envelopes tends to segregate depending on the tissue origin of the virus. Envelopes from two separate tissues from the same patient exhibit very different infectivity characteristics. The B33 envelope, from brain tissue, is very infectious and is macrophage-tropic, while the LN40 envelope, from lymph node tissue, is weakly infectious and is not macrophage-tropic. Replacing the entire gp41 of LN40 with that of B33 restores some infectivity to LN40. The cytoplasmic domain of gp41 contains many motifs important for assembly and infectivity. To examine which motifs are responsible for the weak infectivity of LN40, I made chimeras of gp41, as well as point mutations in gp41. The LN40 chimera containing the entire gp41 of B33 restored the most infectivity. Point mutations in the palmitoylation site, Pr55gagbinding region, and dileucine motif at the C-terminus also restored infectivity when combined. Determinants in the gp41 cytoplasmic domain are responsible for the weak infectivity of LN40; however, it is possible that there are contributing determinants in gp120, such as the ability to use low levels of CD4.
Here, I examined how changes in the vpu and env genes of HIV-1 can impact infectivity, especially infectivity of macrophages. Changes that adversely impact the virus’ ability to infect macrophages may also impact the overall course of disease. However, the data here show that retaining the ability to infect, and replicate in, macrophages give HIV an advantage. I speculate that retaining the ability to infect macrophages gives the virus a reservoir for later in disease, when CD4+ T cells have been depleted, as well as way of avoiding neutralizing antibodies. This work further defines the importance of macrophages in HIV-1 infectivity and disease.
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Mohammad, Mohammad-Shafi Abdullah. "Dust storm phenomena and their environmental impacts in Kuwait." Thesis, University of Glasgow, 1989. http://theses.gla.ac.uk/4135/.
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Dust storms are one of the significant phenomena in the desert areas of the world. It is internationally agreed that days with visibility below 1000 metres due to dust present in the air are a result of strong winds. As Kuwait is part of the Arabian desert, which is identified as one of the major dust sources, so dust storm occurrence is more frequent especially during summer. Dust storms in Kuwait are mainly associated with north and north westerly winds, which are locally known `Shamal'. That is because this wind crosses the Iraqi and Arabian deserts before reaching Kuwait carrying a huge amount of dust and sand. There are local dust sources within Kuwait which supply these winds with dust. Dust occurs in Kuwait in four main types: 1) Sand/dust storm 2) Rising dust 3) Suspended dust 4) Haze There are many factors which play an important role in the occurrence of dust in Kuwait, they include the following: 1) Kuwait's location within the great desert belt. 2) Lack of rainfall. 3) Lack of vegetation cover. 4) Surface air turbulence due to huge amounts of radiation. 5) Human activities such as over-grazing, off-road driving. Dust and sand storms have a bad effect on environment in Kuwait. The main aspects of the environmental impact of dust which have been focussed on in this thesis, are: 1) Dust effects on vehicle body parts and the role of dust storms in road accidents due to poor visibility. 2) Dust effect on house parts and buildings. 3) Dust effects on human health from inhaling the fine dust particles which contain many organic and non-organic material. These materials, which are carried by dust, cause various types of allergies especially with respiratory system. There are many methods which have been used to reduce the amount of dust which is raised up in the air by strong winds. But it seems the most suitable method is tree planting which has many positive effects other than stabilising sand.
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Wang, Xiaoxiao. "The Second Home Phenomenon in Haikou, China." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/1010.
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Second home ownership is a new and booming phenomenon in China. Although it has been widely discussed in newspaper, radio and other mass media, it has not raised much academic concern. This study is a preliminary research in this field. In western counties, second home growth has caused a series of socio-economic impacts to the host community, including housing price inflation, displacement of local people, disruption of local service, etc. These effects identified by western literatures are examined in the context of Haikou, China.
Through applications of interview, on-site observation and secondary research, this study generally confirms the impacts addressed by other second home research. Similar to the western experience, the growth of second homes in Haikou has both positive and negative impacts. On the positive side, the increase of second home purchase contributes to the boom of property-related industry. On the negative side, it causes inflation pressure on housing price and affects the affordability of the housing for local people. The seasonality of second home occupation also leads to a "ghost communit" problem. However, as the development of second homes in Haikou is at an early stage, both their positive and negative impacts are not significant. Some effects such as the displacement of locals, the effects on local retail outlets and services are not detectable. Remarkably, this study addresses two problems that can only be found in China: "college entrance exam immigration" and "illegal sale of hukou".
Based on the major findings, policy recommendations for local government are provided. Implications for conducting research in China, and for future research opportunities are also suggested.
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Hildebrand, Ann E. "Impact of the ENSO phenomenon on Florida fresh tomatoes." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0014885.
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AGUIAR, ROMULO REIS. "EXPERIMENTAL INVESTIGATION AND NUMERICAL ANALYSIS OF THE VIBRO-IMPACT PHENOMENON." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=34221@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
BOLSA NOTA 10
Existem aplicações técnicas onde o principal elemento de um sistema mecânico está sujeito a um padrão de vibração. Um exemplo se encontra na perfuração de poços de petróleo em rochas duras utilizando brocas tricônicas, uma vez que esse tipo de interação broca/ rocha impõe uma vibração longitudinal à estrutura. É possível utilizar parte desta energia para excitar um martelo, uma subestrutura do sistema principal capaz de gerar impactos. A onda de tensão gerada pelo impacto pode ser útil para remover o sistema de uma condição de stick (stick-slip) ou ajudar na propagação de trincas no material a ser perfurado. A perfuração de rochas duras ainda é um grande desao para as empresas de perfuração e exploração de petróleo. Neste contexto, uma forma de conseguir maior eciência da coluna de perfuração é combinando a perfuração rotativa convencional com um dispositivo de vibro-impacto. A tarefa de desenvolver um martelo embarcado na coluna de perfuração e que impacta sobre a broca ainda é uma sugestão a ser implementada. O propósito deste trabalho é a investigação experimental e a modelagem matemática do comportamento da força de impacto num sistema de vibro-impacto embarcado. Mudando a rigidez do martelo e a folga é possível investigar o comportamento do sistema sob diferentes freqüências de excitação. É apresentada uma metodologia para a integração numérica de equações diferenciais descontínuas. Este trabalho também estuda a modelagem da força de impacto, investigando qual modelo matemático disponível na literatura melhor representa os dados experimentais. Os resultados experimentais serão usados para validar o modelo matemático, através do qual o sistema será estudado em maior detalhe. Uma análise não-linear é realizada (diagramas de bifurcação, mapas de Poincaré e mapas de Peterka). Finalmente, este trabalho mostra uma aplicação prática deste sistema de vibro-impacto, onde um sistema massa-mola é montado a uma bancada experimental de perfuração. Resultados experimentais mostram que a aplicação da força de impacto durante a perfuração aumenta a taxa de penetração.
There are technical applications when the main element of a mechanical system is subjected to a regular vibration pattern. An example of this is drilling with tricone bits on hard material, because under normal condition the contact surface becomes lobular, imposing a longitudinal vibration on the drilling structure. It is possible to use part of this energy to resonate a hammer, that is a substructure of the system and impacts on it. The stress wave created by the impact may be useful to release the system from the stick condition of stick-slip phenomenon or to help in the crack propagation of the material being cut. Hard rock drilling is still a great challenge for oil companies. Optimum productivity is made possible by combining the advantages of rotary and percussive drilling. The task of developing an internal hammer in the drillstring that impacts on the drill bit remains an idea to be implemented. The subject of this work is the experimental investigation and the mathematical modeling of the impact force behavior in a vibro-impact system, where a hammer is mounted on a cart that imposes a prescribed displacement. By changing the hammer stiffness and the impact gap it is possible to investigate the impact force behavior under different excitation frequencies. A methodology is presented to numerically integrate the ODEs with a discontinuous right-hand side. This work also compares different models of the impact force presented in prevailing scientific literature to determine which one best fits the experimental data. This information will be used to create a mathematical model of the test rig. The experimental data will be used to validate the mathematical model. The hammer behavior is studied in more detail using a nonlinear analysis (bifurcation diagrams, Poincaré maps and Peterka map). Nonlinear analysis shows the various responses of the hammer, such as dynamical jumps, bifurcations and chaos. Finally, this work shows the field application of this vibro-impact system. A mass-spring system is mounted to an experimental drilling rig. Experimental results shows that impact forces during drilling improve the rate of penetration.
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Carvalho, Nefi Julião. "Impact of the nonlinear phenomenon on wireless radio telecommunications systems." Master's thesis, Universidade de Aveiro, 2008. http://hdl.handle.net/10773/1996.
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Mestrado em Engenharia InformáticaA dimensão e heterogeneidade de recentes sistemas de telecomunicações sem fios impossibilitam a previsão do comportamento do sistema completo quando operado nos limites das suas capacidades. Isto torna irrealista o estudo do impacto do fenómeno não linear no desempenho dos sistemas em especial devido a que os resultados são diferentes quando estudados em separado ou embebidos num sistema. Este trabalho ultrapassa estas problemáticas através do uso de técnicas de co-simulação e de modelação do actual estado da arte as quais tornam possível uma representação mais realista do desempenho de um sistema. ABSTRACT: The dimension and heterogeneity of recent wireless radio telecommunication systems makes impracticable the prediction of the full system behavior when pushed to its performance limits. This makes unrealistic the study of the impact of the nonlinear phenomenon on the systems performance, especially because the results are different when studied alone or embedded in a system. This work overcomes these difficulties by using state-of-the-art cosimulation and modeling techniques that made possible the presentation of more realistic system performance evaluations.
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Palmer, Jolene Maeve. "The phenomenon of resilience among adolescents with learning difficulties in the Vaal Triangle area / by J.M. Palmer." Thesis, North-West University, 2009. http://hdl.handle.net/10394/3102.
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The purpose of this study was to document, by means of a literature review and empirical research, the phenomenon of resilience among adolescents with learning difficulties (LD). My study was motivated by a gap in current literature. Although there are some South African studies that explore the personal antecedents of resilience in youth with LD, there were almost no studies explaining what interpersonal antecedents might contribute to resilience. The aim of the empirical study was to investigate the phenomenon of resilience among adolescent learners coping with LD. This was done by conducting phenomenological research with ten learners who have LD and attend a school for learners with special learning needs. The findings of the study are in accordance with previous studies that suggest that resilience is encouraged by dynamic processes that are both interpersonal and intrapersonal. This study makes a contribution to theory in that it suggests that resilience among adolescent learners with LD is also encouraged by their home environment and the positive relationship with siblings that might be brought on by parents treating all their children impartially. This has not been noted in previous studies. This study also raises questions about whether inclusion of all learners in mainstream schools are beneficial to learners with LD. Because my study identified interpersonal processes (unconditional acceptance, safe spaces, championship and pedagogical expertise) that promoted resilience among those participants who took part in my study, my study contributes to what was understood about the process of resilience in learners with LD and in so doing contributes to practice in that guidelines could be drafted for Life Orientation teachers based on the findings of this study. These guidelines can enable dedicated teachers to adapt their classroom environment so that a learner with LD can benefit.Thesis (M.Ed.)--North-West University, Vaal Triangle Campus, 2009.
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Rachfall, Thomas. "The impact of information and communication technology on the information overload phenomenon." Thesis, Glasgow Caledonian University, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.688316.
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Colton, Katie L. "The Sue-and-Settle Phenomenon: Its Impact on the Law, Agency, and Society." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7412.
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Sue-and-settle is the name applied to a federal agency’s use of litigation to create policy outside of the normal regulatory process. This paper discusses the impact that the sue-and-settle policy has had on Congress, the judiciary, and the Environmental Protection Agency. Specifically, this paper will discuss the issues caused by the perception of collusion within the sue-and-settle policy. First, this paper examines whether a relationship occurs between the litigants. The paper then discusses whether the relationship between the litigants in sue-and-settle cases tends to be collusive or not. The second part of the paper examines how Congress, the Environmental Protection Agency, and the judiciary are viewed because of the continued perception of collusion in the agency’s settlements. Overall, this paper finds that, the impacts of the sue-and-settle policy, and the perception of collusion, has affected Congress, the Environmental Protection Agency, and the judiciary by increasing regulation, distorting the purpose of the courts, and resulting in a lost value for the regulatory process.
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Wood, Enid. "The phenomenon of resilience in aids orphans / Enid Wood." Thesis, North-West University, 2007. http://hdl.handle.net/10394/2466.
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Smit, Trudi. "The impact(s) of enclosed neighbourhoods on transport patterns within the City of Tshwane." Diss., University of Pretoria, 2011. http://hdl.handle.net/2263/33365.
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The occurrence of enclosed neighbourhoods has become a common phenomenon in South African cities from the early 1990’s as a direct impact of crime rates and the fear of crime. While the enclosure of neighbourhoods provide an immediate (temporary) solution to combatting crime within existing neighbourhoods, a number of (unintentional) socio-physical and spatial consequences occur.
Numerous research have been done to establish the social implications of enclosed neighbourhoods in South African cities, including the City of Tshwane, while very little research have been done to establish the physical impacts of enclosed neighbourhoods on the urban form, its impact on the transport patterns or travel behaviour and consequently the increased greenhouse gas levels being emitted into the atmosphere. This study establishes the occurrence and extent of enclosed neighbourhoods within the City of Tshwane to create a generic classification system to establish the practical impact of enclosed neighbourhoods on urban form. In-depth case studies into two enclosed neighbourhoods and a neighbourhood located adjacent to an enclosed neighbourhood were conducted to examine the impact(s) of these neighbourhoods on transport patterns, travel behaviour and greenhouse gas emissions.
An overview of movement networks and an investigation of the influence of the built environment versus self-selection were launched to gain insight into the different factors that might contribute to travel behaviour in general, in addition to neighbourhood enclosures and neighbourhood re-design. This brought forth the very important relationship between land use management, transport planning and the different governing bodies and policies.
The ultimate results gained from the study of selected neighbourhoods clearly showed that a number of factors influence individual transport patterns and travel behaviour, such as self-selection, initial neighbourhood design and population growth. The study did however reveal that through enclosing neighbourhoods and altering its initial neighbourhood design and movement networks, travel behaviour, transport patterns and inevitably greenhouse gas emissions for the specific neighbourhoods and adjacent neighbourhoods will unavoidably change and thus impact negatively (in some ways) on the urban form. More specifically, the results gained from this study showed that those residing within and adjacent to enclosed neighbourhoods travel greater distances on an average day, compared to those who live in an ‘open’ neighbourhood. Consequently, the average household residing within an enclosed neighbourhood emit on average up to (approximately) 4600 g/km CO2 per day more than households residing in ‘open’ neighbourhoods, which result in enclosed neighbourhoods emitting up to 26% more CO2 than ‘open’ neighbourhoods.
Despite these results, residents of these enclosed neighbourhoods believe that the enclosure of these once ‘open’ neighbourhoods do not affect their travel behaviour or any traffic congestion and proclaim that their number one priority is safety which they believe is achieved through the enclosure.Dissertation (MTRP)--University of Pretoria, 2011.
gm2014
Town and Regional Planning
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Kaltenstadler, Albert, and Patrick Ksiazkiewicz. "The Euro Crisis as a Contemporary Phenomenon : The Impact of Germany's Leadership in the Euro Crisis." Thesis, Linnéuniversitetet, Ekonomihögskolan, ELNU, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-12580.
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The current euro crisis is shaped by urgency and actuality. Since it affects a lot of people and different countries, it is also denoted by transboundary effects. Considering these circumstances, the call for quick crisis solution occurs. Therefore, the aim of this thesis is to investigate the leadership issue during the euro crisis. Based on theoretical principles of crisis leadership, we examine the role and behavior of Germany in the euro crisis. Due to the fact that Germany is currently in a significant position, we narrow down the crisis leadership aspect to this specific view. Providing an overall and thorough picture, we investigate Germany’s leadership in the euro crisis from different perspectives. In order to achieve this purpose, we determine this issue from a political, economical and societal perception, which seem to be the most influencing factors in the case of the euro crisis. By assembling the crucial findings of these separate categories, we gain a broader perspective and hence a generalized evaluation and understanding of the German leadership style.
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Hanna, Kinora. "Elevers syn på klimatfrågan : Klimatundervsiningen i skolan." Thesis, Södertörn University College, Lärarutbildningen, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-3350.
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The aim of this study is to find out in which way the education about climate in school is taught and how the students experience the world situation today. There are various theories about the greenhouse effect and its origin and these theories should be addressed to ensure that students get a broader understanding of how climate change occurs. This includes the natural phenomena and also the human impact on climate change. Students in school are a source of concern that only human are the cause of global warming, and know little or almost nothing about the natural phenomena of global warming. I will mention what has emphasized in the national steering documents in the case of environmental education at school.
I have used a qualitative method, where interviews and document analysis were used as techniques. The interviews took place with five students in ninth grade and with three science teachers in the same school.
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Herselman, Charlene. "From ‘logging capital’ to ‘tourism phenomenon’ : the impact of literary tourism on Forks, WA., United States of America." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/45925.
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Literary tourism refers to any travel inspired by literature. This dissertation considers literary
tourism from the perspective of a contemporary literary tourism attraction. It investigates the
origins of literary tourism both in the historical context as well as in academic writing as
interdisciplinary research between geography and literature. The current state of literary
tourism research is also considered and the main research themes at present are identified,
that is, authenticity and who the literary tourists are. This study also considers what the future
might hold for literary tourism by looking at popular contemporary examples, including the
works of J.K. Rowling, G.R.R. Martin, J.R.R. Tolkien, Dan Brown, Stieg Larsson and L.J.
Smith. In this context, literary tourism’s reciprocal relationship with film tourism is unpacked.
This dissertation then moves on to discuss the main focus of this investigation. A mere
decade ago, the world was unaware of a book series called The Twilight Saga by Stephenie
Meyer. Yet in a few short years, the literary tourism associated with this series has turned a
small town in northwest Washington State into a tourism phenomenon. This study considers
the development, extent and impact of literary tourism on this town, called Forks. It also
considers other literary and film tourism sites associated with The Twilight Saga to show the
vast range of the impact literature can have on tourism.Dissertation (MHCS)--University of Pretoria, 2014.
tm2015
Historical and Heritage Studies
MHCS
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GROWETTE, BOSTAPH LISA M. "RACE AND REPEATS: DOES THE REPETITIVE NATURE OF POLICE MOTOR VEHICLE STOPS IMPACT RACIALLY BIASED POLICING?" University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100215923.
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Ortiz, Carlos. "First Principles Calculations of Electron Transport and Structural Damage by Intense Irradiation." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-102376.
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Gnanakumarr, Max Mahadevan. "Integrated investigation of impact-induced noise and vibration in vehicular drivetrain systems." Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/11575.
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This thesis highlights one of the most significant concerns that has preoccupied drivetrain engineers in recent times, namely drivetrain clonk. Clonk is an unacceptable audible sound, which is accompanied by a tactile drivetrain response. This may occur under several different driving conditions. Many drivetrain NVH concerns are related to impact loading of subsystems down-line of engine. These concerns are induced by power torque surge through engagement and disengagement processes, which may propagate through various transmission paths as structural waves. The coincidence of these waves with the acoustic modes of sub-system components leads to audible responses, referred to as clonk. The approach usually undertaken and reported in literature is either purely theoretical or constitutes experimental observation of vehicle conditions. A few research workers have reported rig-based investigations, but not under fully dynamic conditions with controlled and reproducible impulsive action. The research reported in this thesis combines experimental and numerical investigation of high frequency behaviour of light truck drivetrain systems, when subjected to sudden impulsive action, due to driver behaviour. The problem is treated as a multi-physics interactive phenomenon under transient conditions. The devised numerical method combines multi-body dynamics, structural modal analysis, impact dynamics in lash zones and acoustic analysis within an overall investigation framework. A representative drivetrain system rig is designed and implemented, and controlled tests simulating driver behaviour undertaken. The combined numerical predictions and experimental noise and vibration monitoring has highlighted the fundamental aspects of drivetrain behaviour. Good agreement is' also found between the detailed numerical approach and the experimental findings. Novel methods of measurement such as Laser Doppler Vibrometery have been employed. Simultaneous measurements of vibration and noise radiation confirm significant elasto-acoustic coupling at high impact energy levels. One of the major finds of the thesis is the complex nature of the clonk signal, being a combination of accelerative and ringing noise, with the latter also comprising of many other lower energy content as observed in the case of transmission rattle and bearing-induced responses. Therefore, the link between rattle and clonk, long suspected, but not hitherto shown has been confirmed in the thesis. Another major find of particular commercial interest is the insignificant contribution of torsional damping devices such as dual mass flywheels upon the accelerative component of the clonk response.
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Monkhe, Mapolo. "The impact of the xenophobia phenomenon of international students at a selected institution of higher learning in the Western Cape." Thesis, Cape Peninsula University of Technology, 2015. http://hdl.handle.net/20.500.11838/1676.
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Submitted in partial fulfillment of the requirements for the degree Master of Technology: Public Management in the Faculty of Business and Management Sciences at the Cape Peninsula University of TechnologyThis study is based upon the understanding that xenophobia has become a contentious issue in South Africa. International migrants have increasingly become victims of xenophobia at the hands of South African citizens. The commitment to shed some light on the nature of xenophobia in South Africa by examining the experiences of international students in a selected institution of higher learning in Cape Town is what has anchored this study. There is, indeed, evidence of some tension between a fraction of the South African population and international migrants from other African countries. Examining the experiences of international students and their views about xenophobia, the study concluded that the country’s segregated history was a contributing factor to the negative behavior of citizens towards non-citizens. International students have the potential to strengthen both the development of South African institutions of higher learning and the economy at large, they are, however, regarded as being here to disrupt the social order. Even though all international students share the same sense of need to meet and get along with others in the new country, African students endure special difficulties. For, whatever unfortunate reasons, most institutions of higher learning seem not to be doing much to enlighten their local students about other African countries, cultures and histories. Students from elsewhere in Africa often find their South African classmates to be rather uninformed when it comes to appreciating their heritage. This lack of knowledge often sets the stage for xenophobic sentiments between the locals, international migrants in general and international students in particular.
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Habib, MD Zakaria. "The Impacts of UHV AC Transmission Lines on Traditional Line Differential Protection Functions." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-228389.
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UHV transmission lines have several advantages when it comes to transferring of bulk amount ofpower in long distances. Although the technology is available from 1980’s, the number of UHVtransmission lines around the world has been increased in the beginning of this century in orderto supply the high demand of electricity. The number is going to increase even more in the nextfew years. Thus, it is important to study the UHV line characteristics and update the powersystem equipment as well as the operation procedure accordingly.UHV transmission lines exhibits some distinct phenomena which are not present in thetransmission lines with lower voltage levels e.g. high amount of charging current, non-linearincrease of apparent fault impedance with the increase in fault distance, longer time constant forthe DC component in fault current etc. Some of these are very important for different protectionschemes of the transmission line. The aim of this thesis work is to study the impact of UHV linecharacteristics on line differential protection and propose solutions to overcome them.Line differential protection is popular for its good selectivity and simplicity as long as there is adependable reliable communication system between the two ends of the line. High amount ofcapacitive charging current and large phase shift between sending and receiving end currents aretwo important characteristics of UHV lines which have severe impact on the line differentialprotection. It becomes very critical for the protection scheme to maintain good sensitivity andsecurity at the same time. As a result, compensation of the charging current becomes essential.The fixed compensation method is used to compensate the charging current of long lines withlower voltage levels. However, it cannot satisfy the sensitivity requirements for line differentialprotection scheme on UHV lines. Hence, it is necessary to search for other compensationmethods.In this thesis, a solution related with charging current compensation method is proposed with theuse of adaptive phase shift compensation. Several simulations have been done to examine thecharacteristics of the developed method in the worst case scenarios. It is found that the methodexhibits very good sensitivity as well as security for line differential protection on UHV lines.UHV-transmissionsledningar har ett antal fördelar när det gäller överföringskapacitet av effektöver långa avstånd. Även om tekniken har varit tillgänglig sedan 1980-talet är det inte förränunder det senaste årtiondet som utbyggnaden har tagit fart ordentligt. Detta har skett för att mötaden höga efterfrågan på elektricitet. De närmaste åren väntas utbyggnaden öka ytterligare. Motdenna bakgrund är det relevant att studera karaktäristiken av UHV samt att uppdaterakraftsystemutrustning såväl som driften.UHV-tramsmissionslinor är förenade med vissa fenomen som inte förekommer förtransmissionsledningar med lägre spänning. Vissa av dessa fenomen är har stor inverkan påskyddsutrustning för transmissionslinorna. Syftet med denna uppsats är att studera inverkan frånUHV-transmissionsledningar på differentialskydd samt att föreslå lösningar för att överkommainverkan.Differentialskydd är populärt tack vare goda selektiva egenskaper och enkelhet så länge det finnsett pålitligt kommunikationssystem. Hög kapacitans och stor fasskiftning mellan strömmen påavsändar- och mottagarsidan är två viktiga egenskaper hos UHV-transmissionsledningar vilkahar stor inverkan på differentialskyddet. Det är väldigt viktigt att skyddsutrustningen kanupprätthålla god sensitivitet samt säkerhet. Av denna anledning är kompensation för den högakapacitansen viktig. Konstant kompensation används för att kompensera för hör kapacitans hoslånga transmissionslinor med lägre spänning. Denna metod är däremot inte fungerande för UHV.Det är därför nödvändigt att söka efter en annan lösning.I denna uppsats föreslås en lösning på behovet att kompensera för hög kapacitans genom attanvända adaptiv fasskiftkompensation. Flertalet simuleringar har genomförts för att utvärderakaraktäristiken av den utvecklade metoden. Det konstateras att metoden väldigt god känslighetoch säkerhet för differentialskydd av UHV-transmissionsledningar.
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GROSDIDIER, YVES. "Le phenomene wolf-rayet au sein des etoiles chaudes de populations i et ii : histoire des vents stellaires et impact sur la structure nebulaire circumstellaire." Université Louis Pasteur (Strasbourg) (1971-2008), 2000. http://www.theses.fr/2000STR13231.
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A partir du suivi spectroscopique intensif des raies d'emission ciii5696 et civ5801/12, nous analysons les vents issus de 5 etoiles centrales de nebuleuses planetaires (np) galactiques presentant le phenomene wr ; nous etudions aussi l'impact de la fragmentation des vents issus de deux etoiles wr pop. I sur le milieu circumstellaire via : i) l'imagerie ir (nicmos2/hst) de wr 137, et ii) l'imagerie h-alpha (wfpc2/hst) et l'interferometrie fabry-perot h-alpha (sis-cfht) de la nebuleuse m 1-67. Les principaux resultats sont : vents wr pop. Ii : (1) nous demontrons la variabilite spectroscopique intrinseque des vents issus des noyaux de np hd 826 (wc 8), bd +30 3639 (wc 9) et lss 3169 (wc 9), observes durant respectivement 22, 15 et 1 nuits, et rapportons des indications de variabilite pour les noyaux wc 9 hd 167362 et he 2-142 ; (2) la cinematique des sous-pics de bd +30 3639 suggere une anisotropie transitoire de la distribution des fragments dans le vent ; (3) le phenomene wr apparait purement atmospherique, ne depend pas de la population etudiee ; (4) comme pour les wr pop. I, de grands parametres beta sont requis pour ajuster les accelerations observees avec une loi de vitesse de type beta. Impact des vents : (1) au periastre, de la poussiere est detectee dans l'environnement de la binaire wc+ob wr 137. La formation de poussieres est soit facilitee, soit provoquee par la collision des deux vents chauds ; le role capital de la fragmentation des vents est suggere ; (2) la nebuleuse m 1-67 affiche une interaction avec le milieu interstellaire (mis) non-negligeable. Les champs de densite et de vitesse sont tres perturbes. Ces perturbations sont reliees a l'histoire des vents issus de wr 124 durant sa propre evolution, et a l'interaction avec le mis. Les fonctions de structure des champs de densite et de vitesse de m 1-67 ne revelent aucun indice en faveur d'une turbulence.
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Centurion, Adriana Molina. "Impacto das rajadas no desempenho de serviços executados em ambientes em nuvens." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-10092015-144229/.
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Esta tese apresenta a caracterização de desempenho dos serviços executados em um ambiente em nuvem, quando são consideradas rajadas de diferentes origens, intensidades e variabilidades nas cargas de trabalho. Os resultados mostram que a presença de rajadas no processo de chegada das requisições e/ou nas demandas de serviço, ocasiona uma considerável degradação no desempenho dos serviços e, portanto, devem ser consideradas nos modelos de cargas de trabalhos e nas atividades voltadas para avaliação de desempenho em computação em nuvem. Considerando-se a grande influência das rajadas, é proposta e validada uma metodologia que permite monitorar uma carga de trabalho e determinar a ocorrência de rajadas tanto nas taxas de chegadas de requisições quanto nas demandas de serviços. A metodologia utilizada na condução deste trabalho consta de diferentes modelos de cargas de trabalho com rajadas de diferentes variabilidades e intensidades, desenvolvidos e integrados à arquitetura CloudSim-BEQoS proposta nesta tese. Utilizando-se essa arquitetura é possível executar um conjunto de experimentos que possibilitam a obtenção dos resultados que caracterizam o desempenho dos serviços quando são criadas condições de rajadas nas cargas de trabalho submetidas à nuvem.This thesis presents the performance characterization of the services executed in a cloud environment, when bursts are considered from different sources, intensity and variability in the workload. The results show that the presence of bursts in the arrival process of requests and/or in service demands, causes a significant degradation in the performance of services and therefore should belong to the models of workloads and in the activities considered for performance evaluation in cloud computing. Considering the great influence of bursts, a methodology to monitor a workload and predict the occurrence of bursts in both the rates of request arrivals and the service demands is proposed and validated. The methodology used in the conduction of this work consists in different types of workloads with bursts of different variability and intensity, developed and integrated into the CloudSim-BEQoS architecture proposed in this thesis. By using this architecture it is possible to execute a set of experiments that enable the achievement of the results that characterize the performance of services when bursts conditions are created in the workload submitted to the cloud.
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Fakir, Somaya. "The South African application of the global phenomenon of limitation of liability and the impact of proposed amendments to the South African legislation." Master's thesis, Faculty of Law, 2019. http://hdl.handle.net/11427/31162.
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A person who suffers loss, damage or some other form of damage as the result of another party’s action, may in these instances invoke the law of the country in order to claim damages. The damages which are claimed are aimed at compensating the person who has suffered a loss and are based on the law of delict and contract. In South Africa, the stakes are a bit higher in so far as the claimant will need to show that the damage was foreseeable, that there was causation and further remoteness which are all listed as the deciding factors in a claim for liability1 . To this end, Maritime Law in South Africa has a primary exclusion which is applied to the shipowners2 right to limit his/her liability based on the causative enquiry into “actual fault or privity”3 . Causative actual fault or privity is thus the primary exclusion for a shipower’s right to limit his liability and is extensively based on the English Law rules. The concept of Limitation of Liability has extensive history in so far as its evolution is concerned and currently acts as a 'basic premise upon which maritime commerce is conducted4 ’. Based on the importance of the concept and the issues around the South African application of the rules and interpretation of legislation in decided cases, the South African Government has published a draft Merchant Shipping Bill (draft MSB)5 for comment. Among other changes it proposes, is that it advocates the replacement of the current dispensation on limitation of shipowners’ liability with that contained in the Convention on Limitation of Liability for Maritime Claims, 1976 (LLMC)6
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Wells, Rossano S. "The impact of motivation on academic success: using the imposter phenomenon to understand the experiences of a selected group in a ‘black’ higher education institution." Thesis, University of Zululand, 2011. http://hdl.handle.net/10530/1097.
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A dissertation submitted in partial fulfillment of the requirements for the degree PhD Psychology in the Department of Psychology, at the University of Zululand, South Africa, 2011.The present study investigated the impact of motivation on academic success by using the impostor phenomenon to understand the experiences of a selected group in a Black Higher Education institution. The researcher used a questionnaire, interviewed and observed research participants. Questionnaires were sent out in the first week of term to ascertain maximum number of participants as well as receive demographical information. The Impostor Phenomenon questionnaire [IP; 6]: which is a 20- item scale developed by Clarence (1985), was used to assess impostor feelings, that is, feelings of not being deserving of one’s success with an associated fear of being found out as a “fake” . The interview was used to obtain narrative information that would have been difficult to gather through the questionnaire. Recordings from the interviews and observations during interviews were captured, forming data for the final analysis. The study revealed that a positive student –teacher relationship enhanced positive self- concepts in students. This support from teachers was found to engender goal motivations despite situational conditions. I have argued in this study that the social, gender based disparities expressed as culture in South African society, impact negatively on the maintenance of intrinsic motivation. The study also supports the impression that psycho-social development of students needs to be integrated into student’s academic lives for a holistic understanding and possibly enhance their academic performance. Findings in this study were found to correspond with other studies of resiliency, especially among traditional African women.
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Menday, M. T. "Multi-body dynamics analysis and experimental investigations for the determination of the physics of drive train vibro-impact induced elasto-acoustic coupling." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/20789.
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A very short and disagreeable audible and tactile response from a vehicle driveline may be excited when the throttle is abruptly applied or released, or when the clutch is rapidly engaged. The condition is most noticeable in low gear and in slow moving traffic, when other background engine and road noise levels are low. This phenomenon is known as clonk and is often associated with the first cycle of shuffle response, which is a low frequency longitudinal vehicle movement excited by throttle demand. It is often reported that clonk may coincide with each cycle of the shuffle response, and multiple clonks may then occur. The problem is aggravated by backlash and wear in the drivetrain, and it conveys a perception of low quality to the customer. Hitherto, reported investigations do not reveal or discuss the mechanism and causal factors of clonk in a quantitative manner, which would relate the engine impulsive torque to the elastic response of the driveline components, and in particular to the noise radiating surfaces. Crucially, neither have the issues of sensitivity, variability and non-linearity been addressed and published. It is also of fundamental importance that clonk is seen as a total system response to impulsive torque, in the presence of distributed lash at the vibro-elastic impact sites. In this thesis, the drivetrain is defined as the torque path from the engine flywheel to the road wheels. The drivetrain is a lightly damped and highly non-linear dynamic system. There are many impact and noise emitting locations in the driveline that contribute to clonk, when the system is subjected to shock torque loading. This thesis examines the clonk energy paths, from the initial impact to many driveline lash locations, and to the various noise radiating surfaces. Both experimental and theoretical methods are applied to this complex system. Structural and acoustic dynamics are considered, as well as the very important frequency couplings between elastic structures and acoustic volumes. Preliminary road tests had indicated that the clonk phenomenon was a, very short transient impact event between lubricated contacts and having a high frequency characteristic. This indicated that a multi-body dynamics simulation of the driveline, in conjunction with a high frequency elasto-acoustic coupling analysis, would be required. In addition, advanced methods of signal analysis would be required to handle the frequency content of the very short clonk time histories. These are the main novelties of this thesis. There were many successful outcomes from the investigation, including quantitative agreement between the numerical and experimental investigations. From the experimental work, it was established that vehicle clonk could be accurately reproduced on a driveline rig and also on a vehicle chassis dynamometer, under controlled test conditions. It then enabled Design of Experiments to be conducted and the principal causal factors to be identified. The experimental input and output data was also used to verify the mathematical simulation. The high frequency FE analysis of the structures and acoustic cavities were used to predict the dynamic modal response to a shock input. The excellent correlation between model and empirical data that was achieved, clearly established the clonk mechanism in mathematical physics terms. Localised impact of meshing gears under impulsive loads were found to be responsible for high frequency structural wave propagation, some of which coupled with the acoustics modes of cavities, when the speed of wave propagation reached supersonic levels. This finding, although previously surmised, has been shown in the thesis and constitutes a major contribution to knowledge.
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Wang, Lu. "Valorization of apple by-products by the extraction and purification of polyphenols : impact of the ultrasound." Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2509/document.
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Cette thèse porte sur l'intensification de l'extraction de polyphénols à partir de produits à base de pomme (chair, peau et marc) par ultrasons (US) et sur la purification d'extraits de peau de pomme par adsorption/désorption et technologie membranaire. L'extraction sélective des polyphénols issus des produits de la pomme a été analysée. Les données obtenues ont démontré la possibilité d’une régulation fine de l’extraction sélective de la matière soluble, de la catéchine et des composés polyphénoliques totaux en utilisant différentes températures, protocoles UAE, mélanges éthanol/aqueux. La sélectivité de l'extraction de la catéchine dépendait également du type de tissu (chair, peau ou marc) et de la variété de pomme (verte ou rouge). Le phénomène de cavitation généré par les ultrasons pourrait augmenter l'extraction de composants précieux des pelures de fruits en endommageant les membranes cellulaires des échantillons et en accélérant ainsi le transfert de chaleur et de masse. D’autre part, les solvants eau-gaz pourraient améliorer l'efficacité d'extraction des polyphénols des peaux de pomme en renforçant le phénomène de cavitation généré par les ultrasons. L'efficacité de la purification de polyphénols d'extraits de pelure de pomme par adsorption/désorption assisté par ultrasons (adsorbant polyaromatique Amberlite XAD-16) et par électrofiltration sur membrane a été mise en évidence. Les données obtenues ont démontré que la sonication facilitait significativement la cinétique d’adsorption, la capacité d’adsorption accrue et augmentation de l’énergie d’activation de l’adsorption des polyphénols. En outre, le taux de désorption a été positivement affecté par la sonication au cours de l'étape d'adsorption. Par ailleurs, les résultats ont montré que l’électrofiltration sur membrane permettait de purifier les polyphénols dans l’espace anodique (+) et d’obtenir un volume plus important de filtratsThis thesis focuses on the intensification of polyphenols extraction from apple products (flesh, peel, and pomace) by ultrasound (US) and the purification of apple peel extracts by adsorption/desorption and membrane technology. The selective extraction of phenolic contents from apple products has been analyzed. The obtained data evidenced the possibility of fine regulation of selective extraction of soluble matter, catechin and total polyphenolic compounds using different temperatures, ultrasound-assisted extraction (UAE) protocols, ethanol/aqueous mixtures. The selectivity of catechin extraction was also depended on the type of the tissue (flesh, peel or pomace) and apple variety (green or red). The cavitation phenomenon generated by ultrasound could increase extraction of valuable components from fruit peels by damaging cell membranes of samples and accelerating heat and mass transfer by disrupted cell walls of samples. Meanwhile, the gas water solvents could enhance the extraction efficiency of polyphenols and antioxidant activity from apple peels by enhancing cavitation phenomenon generated by ultrasound. The efficiency of polyphenols purification from apple peel extracts with adsorption/desorption process by ultrasound treatment with the polyaromatic amberlite adsorbent XAD-16 and with membrane electro-filtration were studied. The obtained data demonstrated that the sonication significantly facilitated adsorption kinetics and increased activation energy of polyphenols adsorption. In addition, the desorption ratio was positively affected by the sonication during the adsorption step. On the other hand, the results demonstrated that the membrane electro-filtration allowed the purification of polyphenols in the anode (+) space and obtaining larger volume of filtrates
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Nguyen, Phuoc Quy An. "Méthodologie d'évaluation des impacts des eaux usées sur les zones côtières : Application au site de Danang, Vietnam." Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4036.
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La croissance industrielle et démographique mondiale a affecté les zones côtières qui reçoivent quantité de polluants par les effluents. Ces polluants proviennent des eaux usées des systèmes de collecte, des stations d’épuration, et des activités industrielles. Ils affectent considérablement la qualité des eaux. Cet aspect est encore plus marqué dans les pays en développement du fait de rejets directs à la côte. De plus, les populations ainsi que les décideurs locaux ne sont pas réellement sensibilisés aux conséquences sur l’environnement côtier. Dans un tel contexte, les actions d’évaluation doivent être envisagées selon des approches pouvant aboutir avec peu de données disponibles. L’usage de la modélisation permet de simuler une grande variété de sources de polluants et leur impact sur les zones côtières. Les résultats de simulations présentent en particulier une valeur démonstrative pouvant être utilisées pour la sensibilisation du public et des décideurs. Ce travail de recherche cible le développement de méthodologies d’évaluation de l’impact des sources d’eaux usées sur la qualité des eaux côtières. Cette approche est appliquée à la ville de Danang (Vietnam), 3e agglomération du pays, avec un littoral de 74 km intégrant de nombreux enjeux et projets balnéaires, mais avec un nombre significatif de rejets directs d’eaux usées à la côte. Un outil de modélisation a été conçu, bâti sur la simulation d’hydrodynamique et de qualité des eaux. Le scénario 1 simule les effets des eaux usées issues des réseaux de collecte des quartiers NW et SE. Le scénario 2 simule les effets de la première chasse des mêmes quartiers. Le scénario 3 propose 3 sous-scénarios de diffusion des eaux usées depuis les émissaires des usines d’épuration. Le scénario 4 utilise la direction de vent dominant observée, mais fait varier sa vitesse pour simuler la dispersion des polluants le long de la côte. Le scénario 5 établit une simulation avec le déversement de 43 émissaires côtiers en condition d’averse violente, d’arrêt et de débordement des stations d’épuration. Le scénario 6 propose 3 sous-scénarios variant l’orientation du mur déflecteur en sortie du chenal de Phu Loc. Le scénario 7 simule un éloignement de la côte de la sortie du chenal de Phu Loc. L’approche de modélisation proposée est basée sur la combinaison d’outils de modélisation destinés à la simulation de polluants associés aux zones urbaines, à des sources d’eau usées, et à leur dispersion dans l’environnement marin. Le modèle hydrodynamique (Mike Urban avec Mouse Engine) calcule le débit d’eaux usées au débouché du réseau d’assainissement pour les quartiers NW et SE de Danang. Le modèle de qualité des eaux (Mouse Trap, basé sur le package Mouse) est utilisé pour calculer la concentration en polluants durant la première chasse. Pour simuler l’évolution de la qualité des eaux, les différentes sources de pollution sont injectées dans un modèle hydrodynamique 2D (Mike 21 FM 2D) couvrant l’ensemble de la zone côtière, couplé à un modèle de qualité des eaux (Mike 21 FM ECOLab) simulant la diffusion de NH4+ et PO43-. Le domaine couvre une surface d’environ 5000 km2 (70 x 70 km). Les résultats démontrent la faisabilité d’une approche de modélisation pour l’évaluation de la qualité des eaux côtières, par couplage de modèles urbain et côtier. Cette approche développée pour Danang peut s’appliquer à la modélisation de la distribution spatiale des polluants en zone côtière et à l’évaluation de leurs impactsWith the increasing industrial development and significant population growth worldwide, the coastal areas have received many pollutants from wastewater. Pollutants include wastewater from the drainage system, treatment plants, and industrial activities. Their influences seriously affect and damage water quality. In developing and developing countries, the impacts of wastewater on the coastal area are more serious due to many sources directly discharging on the coastal areas. At the same time, the local population and decision-makers are not aware of the consequences of the coastal environment. In this context, assessment actions must be developed and implemented with the relevant approaches that can deal with limited field data sets. The use of modelling tools can allow simulating the various wastewater sources and their effects on the coastal areas. The simulation results have significant educational value and can be used to raise awareness of the public and decision-makers. This research is focusing on developing an assessment methodology of wastewater sources on coastal water quality. The approach is applied to Danang City (Vietnam). Danang City is the third-largest city of Vietnam with a 74 km-long coastline and many major touristic development projects along the shoreline. Some sources of wastewater directly discharge into the Danang City coastal area. Following the development of a modelling tool based on hydrodynamic and water quality simulations. This research proposes seven scenarios to assess the effects of wastewater on the coastal area of Danang City. Scenario 1 simulates the effect of wastewater from the drainage system of North-West and South-East areas. Scenario 2 simulates the impact of the first flush phenomenon from South-East and North-West areas. Scenario 3 suggests three sub-scenarios of wastewater diffusion from the outlet of the WWTPs. Scenario 4 keeps the same direction of the observed wind but changes its speed to simulate the dispersion of pollutants on the coast. Scenario 5 simulates with direct discharge into the sea of 43 outlets along the coast, which may achieve directly to the sea when following conditions occur: heavy rain, power outage, wastewater overpassing the capacity of the treatment plant. Scenario 6 proposes three sub-scenarios of changing a flow-directed wall at the outlet of the Phu Loc Channel. Scenario 7 simulates when moving the outlet of Phu Loc channel far from the coastline. The proposed modelling approach is based on a combination of modelling tools dedicated to simulating pollutants associated with urban runoff, wastewater sources, and dispersion within the marine environment. One hydrodynamic model - Mike Urban model with MOUSE engine - calculates the flow discharge of wastewater at the outlets of the sewage network for North-West and South-East areas of Danang City. A water quality model - MOUSE TRAP, based on the MOUSE package - is used to calculate the concentration of pollutants during the first flush phenomenon. The water quality model is used to analyse the sensitivity of contaminants in the first flush phenomenon. In order to assess the impact within the coastal area, the various sources are injected within a 2D hydrodynamic model covering the full coastal region and the water quality evolution is simulated. In the approach, the Mike 21 FM 2D hydrodynamics model is coupled to a water quality model - Mike 21 FM ECOLab - to simulate the water quality and to identify the diffusion of NH4+ and PO43- on the coast of Danang. The domain is set up over an area of about 5,000 km2 (70 x 70 km). The results show the feasibility of the modelling approach for the assessment of the coastal area water quality by coupling the urban model and the coastal model. The method implemented in Danang is used to model the spatial distribution of pollutants within the coastal area and to assess impacts
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BRAG, Gustava. "PREDICTING THE FUTURE OF INFLUENCER MARKETING : How Public Relations Experts perceive and measure the impacts of Influencer Marketing in their organizations. A Critical Study reflecting the discussions and future thinking of this particular phenomenon." Thesis, Stockholms universitet, Institutionen för mediestudier, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-172674.
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The body of marketing is drastically changing, pushing frontiers in numerous of domains, geographically, behaviourally and strategically with much enhanced technology in an increasingly globalized world. As this phenomenon pushes forward on many fronts, it is worthwhile to ask what will happen in the near future in this field. In today’s society ‘Influencer Marketing’ is known to be an incredibly popular and successful marketing tool, where one might be wondering: What is a plausible future in this area? What are the potential threats and challenges (if any) that we may encounter? What drives Influencer Marketing in organizations and what questions do they have about its impacts and measurements? I am hoping to fulfil this gap with the assistance of Critical Future Studies, Inayatullah (1990,1998) Luke Goode, Michael Godhe (2017,2018) in analysing the various facts and information that are being addressed and most importantly critically assess what is being missed. This Master thesis is a critical study, reflecting the future thinking and strategies relating to Emotional Branding, Danny Brown, Sam Fiorella (2013) made by experts in the fields of Public Relations, using a quantitative content analysis and semi-structured interviews. The chosen methods demonstrate two distinctive results, the content analysis showing a rather positive overview whereas the semi-structured interviews unpack the complexities and challenges in Influencer Marketing and has a negative stance towards its future. Future Studies, is a rigorous branch of study, where unfortunately no one can know for certain what the future holds, however I believe that it is important that we acknowledge values and invite scholars to join this critical dialogue about possible futures and the way we can imagine and discuss the future. The results in this thesis also further demonstrates the necessity in studying this branch of study due to the contradicting answers that are being addressed in the analysis. This thesis also intends to signify that it will not be closure but an encouragement to consider the impetus for a much larger conversation.
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Saidaoui, Hamed Ben Mohamed. "Impact of Disorder on Spin Dependent Transport Phenomena." Diss., 2016. http://hdl.handle.net/10754/619953.
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The impact of the spin degree of freedom on the transport properties of electrons traveling through magnetic materials has been known since the pioneer work of Mott [1]. Since then it has been demonstrated that the spin angular momentum plays a key role in the scattering process of electrons in magnetic multilayers. This role has been emphasized by the discovery of the Giant Magnetoresistance in 1988 by Fert and Grunberg [2, 3]. Among the numerous applications and effects that emerged in mesoscopic devices two mechanisms have attracted our attention during the course of this thesis: the spin transfer torque and the spin Hall effects. The former consists in the transfer of the spin angular momentum from itinerant carriers to local magnetic moments [4]. This mechanism results in the current-driven magnetization switching and excitations, which has potential application in terms of magnetic data storage and non-volatile memories. The latter, spin Hall effect, is considered as well to be one of the most fascinating mechanisms in condensed matter physics due to its ability of generating non-equilibrium spin currents without the need for any magnetic materials. In fact the spin Hall effect relies only on the presence of the spin-orbit interaction in order to create an imbalance between the majority and minority spins.
The objective of this thesis is to investigate the impact of disorder on spin dependent transport phenomena. To do so, we identified three classes of systems on which such disorder may have a dramatic influence: (i) antiferromagnetic materials, (ii) impurity-driven spin-orbit coupled systems and (iii) two dimensional semiconducting electron gases with Rashba spin-orbit coupling.
Antiferromagnetic materials - We showed that in antiferromagnetic spin-valves, spin transfer torque is highly sensitive to disorder, which prevents its experimental observation. To solve this issue, we proposed to use either a tunnel barrier as a spacer or a local spin torque using spin-orbit coupling. In both cases, we demonstrated that the torque is much more robust against impurities, which opens appealing venues for its experimental observation.
Extrinsic spin-orbit coupled systems - In disordered metals accommodating spin orbit coupled impurities, it is well-known that spin Hall effect emerges due to spin dependent Mott scattering. Following a recent prediction, we showed that another effect coexists: the spin swapping effect, that converts an incoming spin current into another spin current by "swapping" the momentum and spin directions. We showed that this effect can generate peculiar spin torque in ultrathin magnetic bilayers.
Semiconductors spintronics - This last field of research has attracted a massive amount of hope in the past fifteen years, due to the ability of coherently manipulating the spin degree of freedom through interfacial, so-called Rashba, spin-orbit coupling. However, numerical simulations failed reproducing experimental results due to coherent interferences between the very large number of modes present in the system. We showed that spin-independent disorder can actually wash out these interferences and promote the conservation of the spin signal. In the course of this PhD, we showed that while disorder-induced dephasing is usually detrimental to the transmission of spin information, in selected situation, it can actually promote spin transport mechanisms and participate to the enhancement of the desired spintronics phenomenon.
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Liu, Chia-wei, and 劉家瑋. "Analysis of Impact Phenomena of Blast Wave Over Bodies." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/03147127041646141881.
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碩士國立屏東科技大學
車輛工程系碩士班
93
The leading edge of a blast wave is in the form of a shock wave which propagates at supersonic speed and is capable of causing severe damage. This study investigates the behavior of blast waves by employing the finite volume method to solve the associated three-dimensional, time-dependent, inviscous flow Euler equations. The complex transitional shock phenomena are investigated by means of a multi-block mesh system and a flux computational model. In simulating the complex shock propagation problem, the Total Variation Diminishing (TVD) upwind method is applied to solve the Euler equations. Spatial discretization is performed using Roe’s solver with high-order Kappa Monotone Upwind-centered Schemes for Conservation Laws (MUSCL) interpolation. Time integration is achieved via the second-order explicit Hancock method. The simulation results enable the prediction of the blast wave behavior as it impacts against the wall of a bomb shelter and travels through its smooth tunnel Specifically, this study identifies the complex phenomena of flow structures, pressure distributions, and shock-shock and shock-vortex interactions for closed-ended and open-ended bomb shelters. The numerical results are shown in good agreement with the experimental results obtained from shock tube flow studies. Meanwhile, a wheeled armored vehicle case is simulated in this study. Wheeled armored vehicles are used for transportation of combat crew, weapon systems and facilities in the battlefields. The highly mobility is also the primary requirement under the tactical deployment missions. The fragments and blast waves generated by an explosion of a bomb would damage the vehicle and crew. In this study, numerical investigation about the interaction of a blast wave in an unsteady explosion with a wheeled armored vehicle is presented. The objective of this paper aims at the study of blasting wave propagation, reflection and interaction with vehicle, especially those around the front and chassis regions. The result of complex flow structure and analysis of pressure distribution are presented in this work.
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Mihaly, Jonathan Michael. "Investigation of Hypervelocity Impact Phenomena Using Real-time Concurrent Diagnostics." Thesis, 2013. https://thesis.library.caltech.edu/7869/1/Mihaly_Jonathan_2013_thesis.pdf.
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Hypervelocity impact of meteoroids and orbital debris poses a serious and growing threat to spacecraft. To study hypervelocity impact phenomena, a comprehensive ensemble of real-time concurrently operated diagnostics has been developed and implemented in the Small Particle Hypervelocity Impact Range (SPHIR) facility. This suite of simultaneously operated instrumentation provides multiple complementary measurements that facilitate the characterization of many impact phenomena in a single experiment. The investigation of hypervelocity impact phenomena described in this work focuses on normal impacts of 1.8 mm nylon 6/6 cylinder projectiles and variable thickness aluminum targets. The SPHIR facility two-stage light-gas gun is capable of routinely launching 5.5 mg nylon impactors to speeds of 5 to 7 km/s. Refinement of legacy SPHIR operation procedures and the investigation of first-stage pressure have improved the velocity performance of the facility, resulting in an increase in average impact velocity of at least 0.57 km/s. Results for the perforation area indicate the considered range of target thicknesses represent multiple regimes describing the non-monotonic scaling of target perforation with decreasing target thickness. The laser side-lighting (LSL) system has been developed to provide ultra-high-speed shadowgraph images of the impact event. This novel optical technique is demonstrated to characterize the propagation velocity and two-dimensional optical density of impact-generated debris clouds. Additionally, a debris capture system is located behind the target during every experiment to provide complementary information regarding the trajectory distribution and penetration depth of individual debris particles. The utilization of a coherent, collimated illumination source in the LSL system facilitates the simultaneous measurement of impact phenomena with near-IR and UV-vis spectrograph systems. Comparison of LSL images to concurrent IR results indicates two distinctly different phenomena. A high-speed, pressure-dependent IR-emitting cloud is observed in experiments to expand at velocities much higher than the debris and ejecta phenomena observed using the LSL system. In double-plate target configurations, this phenomena is observed to interact with the rear-wall several micro-seconds before the subsequent arrival of the debris cloud. Additionally, dimensional analysis presented by Whitham for blast waves is shown to describe the pressure-dependent radial expansion of the observed IR-emitting phenomena. Although this work focuses on a single hypervelocity impact configuration, the diagnostic capabilities and techniques described can be used with a wide variety of impactors, materials, and geometries to investigate any number of engineering and scientific problems.
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Hahn, Thomas. "Interfacial electrokinetic transport phenomena and their impact on DNA electrophoresis in microfluidics." Phd thesis, 2011. http://tuprints.ulb.tu-darmstadt.de/2433/1/PhDthesis_Hahn.pdf.
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The dissertation examines two different options to separate DNA based on differences in size by utilising electric fields. Each of the techniques is based on a new approach and faces several fundamental problems concerning electrokinetics. A microfluidic environment is chosen to experimentally investigate DNA electrophoresis at a small scale. A sophisticated setup is employed that on the one hand enables a multiphase flow, while at the same time it stabilises two immiscible polymer phases in a microfluidic compartment. An aqueous two-phase system consisting of poly(ethylene glycol) and dextran provides a stable liquid-liquid interface under quiescent conditions. Such a setup allows the application of an electric field perpendicular to the liquid-liquid interface. In doing so, DNA accumulates at the interface. The parameters influencing the electrophoretic adsorption process are examined in detail. A highlight of the experimental investigations is desorption of DNA from the interface that is triggered by increasing the electric field strength. The latter phenomenon affords a separation of different sized DNA fragments across the liquid-liquid interface. Smaller DNA fragments desorb at lower field amplitudes while larger ones desorb at larger field strengths. Although liquid-liquid interfacial phenomena in aqueous two-phase systems are complex, a preliminary understanding is achieved addressing basic theoretical issues. In the following the reader is introduced into a second and alternative setup to yield a size separation of DNA. The approach is based on traditional capillary electrophoresis. The novelty is examined by combining several preconcentration techniques with a gel-based size separation of DNA in a preparative manner. The DNA migrates due to the application of an electric field. The preconcentration is accomplished by electrokinetic trapping at a charged membrane embedded into a poly(methyl methacrylate) microchip. It has been found that a fluidic counter flow supports DNA trapping at a membrane. A subsequent DNA size separation is exploited to separate free fetal DNA from maternal DNA in blood of pregnant women providing preliminary results to afford a basis for non-invasive prenatal diagnosis.
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Kurniawan, Tetuko, and 陳炳萊. "Investigation on the Partial Coalescence and Vortex Ring Phenomena of Drop Impact onto Deep Liquid." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/31624738934494510419.
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碩士國立臺灣大學
應用力學研究所
99
An investigation on phenomena occurs when a drop impact onto deep liquid was done and two major cases were concentrated. In very small impact velocity of drop, partial coalescence phenomenon was investigated inside a controllable vacuum chamber. It was found that the reduced air pressure causes the period of coalescence cascade become shorter. It revealed that the reduced air pressure decreases the ability of drop to float and to pinch-off a secondary droplet. Another investigated case was the vortex ring produced by impacted drop. Extensive study on how to produce highly repeatable vortex ring was first conducted. It was found the hydrostatic and control of the drop nozzle is critical in producing repeatable drop-formed vortex ring. More details of experiment set up for such a system are discussed in this report such as how to reduce the meniscus and how to reduce current in the target liquid. As repeatable results have been achieved, series of experiment with various drop sizes and different liquids were conducted. It has been found that the maximum penetration depth Lmax occurs when impact drop shape near the peak of b1/R. The value of b1/R corresponds to the production of Lmax is around 0.9 peak value of b1/R. This finding was found valid for various drop sizes and various liquid conducted.