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Sanchez, Caballero Lizeth Katherine. "Geostatistical modeling of geotechnical variables considering directional dependence." Electronic Thesis or Diss., Université Paris sciences et lettres, 2022. https://thesesprivees.mines-paristech.fr/2022/2022UPSLM045_archivage.pdf.
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Avec la modélisation géologique et géométallurgique, la modélisation géotechnique est l'une des composantes essentielles de la planification et du développement de projets miniers à ciel ouvert et souterrains. Une caractéristique particulière de nombreuses variables géotechniques est d'être dépendante de la direction, c'est-à-dire que la mesure d'une carotte de sondage dépend non seulement de sa position géographique mais aussi de son orientation. Pour tenir compte de cette caractéristique, il est proposé de régionaliser les variables géotechniques dans un espace à cinq dimensions correspondant au produit sur l'espace géographique à trois dimensions et la sphère à deux dimensions, de sorte que chaque mesure soit indexée par ses coordonnées est, nord, élévation, azimut et pendage. Au lieu de faire des prédictions et des simulations conditionnées à une direction particulière, ce nouveau paradigme permet d'interpoler des variables géotechniques à n'importe quel endroit de l'espace géographique, et pour n'importe quelle direction. La structure de corrélation spatiale peut être inférée et modélisée en utilisant des covariances séparables ou des combinaisons de covariances séparables, sous une hypothèse de stationnarité dans l'espace géographique et d'isotropie sur la sphère. De plus, une simulation conditionnelle peut être effectuée par des méthodes spectrales ou de bandes tournantes, basées sur des produits de champs aléatoires stationnaires dans l'espace géographique et de champs aléatoires isotropes sur la sphère. La méthodologie proposée est illustrée par modélisation de la fréquence de discontinuité linéaire (P10), la désignation de la qualité de la roche (RQD), et le Slope Mass Rating (SMR) dans trois gisements miniersTogether with geological and geometallurgical modeling, geotechnical modeling is one of the essential components for the planning and development of open pit and underground mining projects. A particular characteristic of many geotechnical variables is to be direction-dependent, i.e., the measurement of a core sample not only depends on the in-situ position of this sample but also on its in-situ orientation. To account for this characteristic, it is proposed to regionalize such variables in a five-dimensional space corresponding to the product on the three-dimensional geographical space and the two-dimensional sphere, so that each measurement is indexed by its easting, northing, elevation, azimuth, and dip. Instead of making predictions and simulations conditioned to a particular direction, this new paradigm allows geotechnical variables to be interpolated at any place in the geographic space, for any direction. The spatial correlation structure can be inferred and modeled by using separable covariances or combinations of separable covariances, under an assumption of stationarity in the geographical space and isotropy on the sphere. Also, conditional simulation can be performed by turning bands, based on products of stationary random fields in the geographic space and isotropic random fields on the sphere. The proposed methodology is illustrated with the modeling of the linear discontinuity frequency (P10), the rock quality designation (RQD), and Slope Mass Rating (SMR) in three mineral deposits
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Ulbrich, Carolin [Verfasser]. "Spectral and directional dependence of light-trapping in solar cells / Carolin Ulbrich." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2011. http://d-nb.info/1018190570/34.
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Yoder, Tim. "Investigation in to nonlinear grasshoff number dependence of convection within a hot melt during directional solidification." Connect to this title online, 2005. http://hdl.handle.net/1811/311.
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Thesis (Honors)--Ohio State University, 2005.Title from first page of PDF file. Document formattted into pages: contains 31 p.; also includes graphics. Includes bibliographical references (p. 31). Available online via Ohio State University's Knowledge Bank.
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Bourgeois, Raymond C. "Phonotactic orientation behavior of tethered flying crickets (Teleogryllus oceanicus) and its dependence on stimulus carrier frequency." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63311.
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Noureldin, Diaa. "Essays on multivariate volatility and dependence models for financial time series." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:fdf82d35-a5e7-4295-b7bf-c7009cad7b56.
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This thesis investigates the modelling and forecasting of multivariate volatility and dependence in financial time series. The first paper proposes a new model for forecasting changes in the term structure (TS) of interest rates. Using the level, slope and curvature factors of the dynamic Nelson-Siegel model, we build a time-varying copula model for the factor dynamics allowing for departure from the normality assumption typically adopted in TS models. To induce relative immunity to structural breaks, we model and forecast the factor changes and not the factor levels. Using US Treasury yields for the period 1986:3-2010:12, our in-sample analysis indicates model stability and we show statistically significant gains due to allowing for a time-varying dependence structure which permits joint extreme factor movements. Our out-of-sample analysis indicates the model's superior ability to forecast the conditional mean in terms of root mean square error reductions and directional forecast accuracy. The forecast gains are stronger during the recent financial crisis. We also conduct out-of-sample model evaluation based on conditional density forecasts. The second paper introduces a new class of multivariate volatility models that utilizes high-frequency data. We discuss the models' dynamics and highlight their differences from multivariate GARCH models. We also discuss their covariance targeting specification and provide closed-form formulas for multi-step forecasts. Estimation and inference strategies are outlined. Empirical results suggest that the HEAVY model outperforms the multivariate GARCH model out-of-sample, with the gains being particularly significant at short forecast horizons. Forecast gains are obtained for both forecast variances and correlations. The third paper introduces a new class of multivariate volatility models which is easy to estimate using covariance targeting. The key idea is to rotate the returns and then fit them using a BEKK model for the conditional covariance with the identity matrix as the covariance target. The extension to DCC type models is given, enriching this class. We focus primarily on diagonal BEKK and DCC models, and a related parameterisation which imposes common persistence on all elements of the conditional covariance matrix. Inference for these models is computationally attractive, and the asymptotics is standard. The techniques are illustrated using recent data on the S&P 500 ETF and some DJIA stocks, including comparisons to the related orthogonal GARCH models.
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Zhao, Ding. "Spherulitic Growth and Thermodynamic Equilibrium in Multicomponent Elastic Films Under Solvent-vapor Annealing." UKnowledge, 2018. https://uknowledge.uky.edu/math_etds/56.
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In this dissertation, we will study solvent-vapor induced spherulitic growth in multicomponent thin films modeled as prestressed elastic solids. The interface between the crystalline phase and the amorphous phase will be treated as an evolving thermodynamic system and no diffusion of any component will be considered.
The dissertation is divided into three parts. In Part I we will determine necessary conditions of thermodynamic equilibrium between the two solid phases, the inter- face, and the vapor. In Part II we will derive the thermodynamic driving force for spherulitic growth in multicomponent elastic thin films. In Part III we will investigate the effect of prestress on the directional dependence of the growth. There a formula that delineates how the prestress affects the shape of the spherulite will be proposed.
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Fisch, Adam(Adam Joshua). "Typology-aware neural dependency parsing : challenges and directions." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128400.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, February, 2020
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 39-41).
This thesis explores the task of leveraging typology in the context of cross-lingual dependency parsing. While this linguistic information has shown great promise in pre-neural parsing, results for neural architectures have been mixed. The aim of the investigation put forth in this thesis is to better understand this state-of-the-art. Our main findings are as follows: 1) The benefit of typological information is derived from coarsely grouping languages into syntactically-homogeneous clusters rather than from learning to leverage variations along individual typological dimensions in a compositional manner; 2) Typology consistent with the actual corpus statistics yields better transfer performance; 3) Typological similarity is only a rough proxy of cross-lingual transferability with respect to parsing. Code for the work in this thesis is available at https://github.com/ajfisch/TypologyParser.
by Adam Fisch.
S.M.
S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Jack, David Abram. "Incorporation of directionally dependent diffusion with polymer composite flow theory." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4579.
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Thesis (M.S.) University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 23, 2007) Includes bibliographical references.
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Jagannathan, Preshanth. "Full Mueller imaging: direction dependent corrections in polarimetric radio imaging." Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/28421.
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Magnetic fields pervade the universe, spanning a multitude of scales from the dipolar field on Earth, to the largest gravitationally bound structures such as galaxy clusters [1]. The magnetic fields play a vital role in the evolution of these astronomical systems. In addition to the multitude of scales, magnetic fields are present in different astronomical systems of varying strengths. The strongest observed astronomical magnetic fields are in neutron stars with a field strength of ≈ 1015 G [2], far higher than any man-made fields till date. In stark contrast magnetic fields in the interstellar medium while ubiquitous are only a few µG in field strength. Many fundamental processes in astrophysics have magnetism at their heart, be it cosmic ray particle acceleration, star formation, or the launch of radio galaxy jets, pulsars, etc. One key fundamental process that allows us to detect and characterize cosmic magnetic fields with radio astronomy is the polarization of synchrotron radiation. Synchrotron radiation is intrinsically polarized broadband continuum radiation emitted by relativistic charged particles accelerated by the presence of magnetic fields. The emissivity of the synchrotron radiation is tied to the magnetic field strength B and the spectral index α (defined such that the flux density S ∝ ν −α ) such that ε ∝ B 1+α .
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Chehab, Abdul Ghafar. "Time dependent response of pulled-in-place HDPE pipes." Thesis, Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1239.
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Helmersson, Irene. "Uppskattning av vindklimat : – Implementering och utvärdering även metod för normalårskorrektion." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-303977.
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The expected technical lifetime for a wind turbine is 20-25 years (Wizelius, 2007). In the process of planning a wind farm on a site an estimation of the average wind speed and the energy yield is required from the site. Due to large fluctuations in wind velocity from one year to another it is, from a climatologically point of view, not sufficient to measure the wind for a short period of time, e.g. one year. The year measured may have uncommonly high or uncommonly low winds and thereby generate an average not representative of the wind climate on the site. In the same time it is neither practical nor economically desirable to measure for a longer time period. Instead the measured data collected for a short period of time is scaled into a normal year before it is used to calculate the energy content. This normal year correction can be preformed using different methods. Principally, the methods relate the short time series, measured on the site, to one or more variables of a long time reference series. As a long time reference series the geostrophic wind on the site or a series of measured wind nearby can be used. If the correlation between the two series is sufficiently high a normal year correction may be done using the relation. Normal year correction has foremost been done using the relation between the velocities of the measured wind and a reference wind. The purpose in this study is to evaluate and implement a part of an algorithm for normal year correction considering additional variables besides wind velocity. The relationships studied are between measured wind speed and geostrophic wind speed, geostrophic wind direction and time of the year. For the purpose of evaluating the algorithm two wind data series from Näsudden, on the Swedish island of Gotland, for a period of 15 years has been used. Measured wind on 75 meters and geostrophic wind on 850hPa. Where the geostrophic wind has been used as a long time reference and the measured wind for one year at the time has been related to this reference. The relation has then been used together with the geostrophic wind data to create an estimation of the wind climate on Näsudden in three steps. Step one establishes the estimation due to the relation of geostrophic wind speed. Step two corrects the estimation due to the relation of geostrophic wind direction and step three corrects the estimation due to the relation of time of year. The conclusions from this study showed that with the method used for implementing the algorithm the normal year correction using only the relation between the velocities of the measured wind and the geostrophic wind gives the best estimation of the climatically mean wind speed. The standard deviation gives a 5 % risk for more than 0.436 m/s error for estimation of the mean wind on the site, which is comparable to earlier studies. The introduction of the wind direction dependence overestimates the mean wind on the site and amplifies the error. The introduction of the season dependence amplifies the error further and overestimates the mean wind additionally.En vindturbin har en planerad livslängd på 20-25 år (Wizelius, 2007). Vid planering av en vindkraftspark behöver en estimering av medelvinden och energiutvinningen utföras för platsen man är intresserad av. På grund av stora fluktuationer av vindhastighet från år till år är det ur klimatologisk synpunkt inte tillräckligt att mäta under en kort period, exempelvis ett år. Det år man mäter kan ha ovanligt starka eller ovanligt svaga vindar och ge en icke representativ bild av vindklimatet på platsen. Samtidigt är det inte praktiskt eller ekonomiskt önskvärt att mäta under en längre tidsperiod. Istället kan den korta mätserie som insamlats korrigeras till ett normalår med hjälp av en långtidsreferens innan den används för att beräkna energiinnehållet. I princip går normalårskorrigering ut på att relatera den korta mätserien till en eller flera variabler i långtidsreferensen. Som långtidsreferensdata kan den geostrofiska vinden på platsen eller en lång mätserie från en närliggande plats användas. Om korrelationen mellan de två serierna är tillräckligt hög kan en normalårskorrigering göras med hjälp av relationen. Tidigare har man vid normalårskorrigering främst sett till relationen mellan vindhastigheterna för den uppmätta vinden och en referensvind. Syftet i detta arbete är att utvärdera en del av en algoritm för normalårskorrigering där hänsyn tas till fler variabler än endast vindhastighet. Samband som studeras är mellan uppmätt vindhastighet och geostrofisk vindhastighet, geostrofisk vindriktning och tid på året. För utvärderingen av algoritmen har två vinddataserier från Näsudden på Gotland använts för en period av 15 år med uppmätt vind på 75m och geostrofisk vind på 850hPa. Där den geostrofiska vinden fått representera långtidsreferensen och den uppmätta vinden för ett år i taget har relaterats till denna. Efter normalårskorrigeringen har den uppmätta vinden för 15 år fått representera vindklimatet på platsen som jämförelse. Enligt algoritmen har uppskattning av vindklimatet på Näsudden skapats i tre steg. Steg 1 är en uppskattning av vinden från sambandet för geostrofisk vindhastighet. Steg 2 är en korrektion av uppskattningen genom sambandet till geostrofisk vindriktning och steg 3 en korrektion av uppskattningen genom sambandet till tid på året. Efter vart steg skickas det aktuella estimatet vidare till nästa steg där det korrigeras med avseende på nästa samband. Slutsatserna från undersökningen visade att med den metod som använts ger normalårskorrigeringen med enbart sambandet till hastighet bäst uppskattning av den klimatologiska medelvinden. Standardavvikelsen för estimatet ger 5 % risk för mer än 0,436 m/s fel vid uppskattning av klimatologisk medelvind vilket är jämförbart med tidigare studier. Vidare överskattar införandet av vindriktningsberoendet den uppskattade medelvindhastigheten samt ökar osäkerheten. Även införandet av säsongsberoendet överskattar medelvindhastigheten ytterligare samt även osäkerheten.
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Tan, Ai Hui. "System identification and its applications, with emphasis on direction-dependent processes." Thesis, University of Warwick, 2002. http://wrap.warwick.ac.uk/66737/.
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In the first sub-section of the thesis, signal design for both linear and nonlinear system identification is considered. To identify a linear system using a perturbation test, a binary signal is sufficient and has the advantage of maximising the power available within a specified peak-to-peak amplitude. For this purpose, a program was written to generate five classes of binary and near-binary signal. However, to identify a nonlinear system with a Hammerstein structure, a multi-level signal is required, and methods to optimise such a signal are proposed. In the second sub-section, the detection of the departure from linearity for direction dependent processes is considered. It was found that only signals based on maximum length sequences allow the detection of such characteristics due to the coherent patterns formed in the cross correlation function. The 'combined' linear dynamics of the system are identified. The modelling of such processes using Wiener and neural network models is investigated. Practical results from an electronic nose are presented. The control of direction-dependent processes using the PID controller is then examined, with the design rules set according to the identified 'combined' dynamics. The thesis then moves on to the topic of autotuning. The autotuning of Smith predictors for processes with significant dead time is considered. The frequency response of the process is identified in closed-loop using a multi sine signal. Tuning rules for robust control are suggested which relate the controller parameters to the process parameters. A real application using a hot-air flow device is illustrated. The final sub-section of the thesis looks at the identification of Wiener-Hammerstein models. A new technique using linear interpolation is proposed which is based on the symmetry properties of the Volterra kernel. This method has the advantages that only a single experiment is needed, and it is simple to use since no optimisation or recursive computations are required. Simulation examples are provided to illustrate the effectiveness of the technique, and its robustness in the presence of noise and input signal distortion.
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Young, Andre. "Improving the direction-dependent gain calibration of reflector antenna radio telescopes." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80915.
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Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Utilising future radio interferometer arrays, such as the Square Kilometre Array (SKA), to their full potential will require calibrating for various direction- dependent effects, including the radiation pattern (or primary beam in the parlance of radio astronomers) of each of the antennas in such an array. This requires an accurate characterisation of the radiation patterns at the time of observation, as changing operating conditions may cause substantial variation in these patterns. Furthermore, fundamental imaging limits, as well as practical time constraints, limit the amount of measurement data that can be used to perform such characterisation. Herein three techniques are presented which aim to address this requirement by providing pattern models that use the least amount of measurement data for an accurate characterisation of the radiation pattern. These methods are demonstrated through application to the MeerKAT Offset Gregorian (OG) dual-reflector antenna. The first technique is based on a novel application of the Jaco bi-Bessel series in which the expansion coefficients are solved directly from the secondary pattern. Improving the efficiency of this model in the desired application leads to the development of a different set of basis functions, as well as two constrained solution approaches which reduce the number of pattern measurements required to yield an accurate and unique solution. The second approach extends the application of the recently proposed Characteristic Basis Function Patterns (CBFPs) to compensate for non-linear pattern variations resulting from mechanical deformations in a reflector antenna system. The superior modelling capabilities of these numerical basis functions, which contain most of the pattern features of the given antenna design in a single term, over that of analytic basis functions are demonstrated. The final method focusses on an antenna employing a Phased Array Feed (PAF) in which multiple beam patterns are created through th e use of a beam-former. Calibration of such systems poses a difficult problem as the radiation pattern shape is susceptible to gain variations. Here we propose a solution which is based on using a Linearly Constrained Minimum Varia nce (LCMV) beamformer to conform the realised beam pattern to a physics-based analytic function. Results show that the LCMV beamformer successful ly produces circularly symmetric beams that are accurately characterised with a single-term analytic function over a wide FoV.
AFRIKAANSE OPSOMMING: Die volle benutting van toekomstige radio interferometersamestellings, soos die Square Kilometre Array (SKA), benodig die kalibrering van verskeie rigting-afhanklike effekte, insluitend die stralingspatroon (bekend as die primêre bundel onder radio astronome) van elke antenne in só ’n samestelling. Hierdie benodig ’n akkurate karakterisering van die stralingspatrone op die waarnemingstydstip, aangesien veranderende bedryfskarakteristieke ’n beduidende afwyking in hierdie patrone veroorsaak. Verder, weens fund amentele perke in beeldverwerking, asook praktiese tydbeperkinge, bestaan daar ’n limiet op die hoeveelheid gemeetde data wat benut kan word om die nodige karakterisering mee te doen. Hierin word drie tegnieke ten toon gestel wat gemik is daarop om aan hierdie behoefte te voorsien deur die gebruik van modelle wat ’n minimum hoeveelheid metingdata benodig om ’n akkurate beskrywing van die stralingspatroon te lewer. Die verskeie metodes word aangebied aan die hand van die MeerKAT afset-Gregorian dubbelreflektorantenne. Die eerste tegniek is gebasseer op ’n nuwe toepassing van die Jacobi- Besselreeks waarin die sekondêre stralingspatroon direk gebruik word om die uitsettingskoëffisiënte op te los. Die doelmatigheidsverbetering van hierdie model in die huidige toepassing lei na die ontwikkeling van ’n nuwe versameling van basisfunksies, asook twee voorwaardelike oplossings wat die nodige aantal metings vir ’n akkurate, unieke oplossing verminder. In die tweede tegniek word die toepassing van die onlangs voorgestelde Karakteristieke Basisfunksie Patrone uitgebrei om te vergoed vir die nie-lineêre stralingspatroonafwykings wat teweeggebring word deur meganiese vervormings in die reflektorantenne. Die superieure modelleringsvermoëns van hierdie numeriese basisfunksies, wat meeste van die patroonkenmerke vasvang in ’n enkele term, bo dié van analitiese basisfunksies word gedemonstreer. Die laaste metode fokus op die gebruik van ’n gefaseerde samestellingvoer waarin veelvoudige bundelpatrone geskep word deur die gebruik van ’n bundelvormer. Die kalibrering van sulke instrumente word bemoeilik daardeur dat die patroonvorm gevoelig is vir aanwinsafwykings. Hier stel ons ’n oplossing voor waarin ’n lineêrbegrensde minimumstrooiing bundelvormer gebruik word om die stralingspatroon te pas op ’n fisika-gebasseerde analitiese funksie. Resultate toon dat hierdie bundelvormer sirkelsimmetriese bundels kan skep wat akkuraat beskryf word deur ’n een-term analitiese funksie oor ’n wye gesigsveld.
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Pipe, Mark. "Limits on spin-dependent WIMP-proton cross-sections using the DRIFT-IId directional dark matter detector." Thesis, University of Sheffield, 2011. http://etheses.whiterose.ac.uk/2088/.
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The nature of dark matter remains one of the biggest questions in physics today. Weakly Interacting Massive Particles (WIMPs) are a particularly well motivated candidate for the missing matter that makes up 85% of the mass of the Universe. The most promising method for an unambiguous proof of the existence of WIMPs is via detection of the predicted directional anisotropy. The DRIFT detector at the Boulby Underground Laboratory in the UK is the world's first large scale directionally sensitive dark matter detector. This thesis presents work focussing on the ability of DRIFT to be competitive with non-directional detectors in exploring new spin-dependent WIMP interaction phase-space. Experimental efforts towards this are discussed, including the first calibration measurements of spin-dependent target gases in DRIFT, and development and implementation of an automated gas mixing system required for spin-dependent gas mixture operation. This thesis presents the first long-term study of backgrounds in DRIFT in which current limiting backgrounds are identified and studied, providing information crucial to future background reduction strategies. Developments of the WIMP analysis procedure are presented that result in an improved sensitivity to WIMP-mimicking neutron-induced nuclear recoils by a factor of 2.4. Data from the first runs with spin-dependent sensitive CS2-CF4 gas mixtures are presented with improved analysis methods. This thesis presents the first blind analysis results from a directionally sensitive dark matter detector with upper limits on the SD WIMP-proton interaction cross-section with a minimum of 0.93 pb for a 100 GeV WIMP.
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Holt, Galen, and Peter Chesson. "Scale-Dependent Community Theory for Streams and Other Linear Habitats." UNIV CHICAGO PRESS, 2016. http://hdl.handle.net/10150/621321.
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The maintenance of species diversity occurs at the regional scale but depends on interacting processes at the full range of lower scales. Although there is a long history of study of regional diversity as an emergent property, analyses of fully multiscale dynamics are rare. Here, we use scale transition theory for a quantitative analysis of multiscale diversity maintenance with continuous scales of dispersal and environmental variation in space and time. We develop our analysis with a model of a linear habitat, applicable to streams or coastlines, to provide a theoretical foundation for the long-standing interest in environmental variation and dispersal, including downstream drift. We find that the strength of regional coexistence is strongest when local densities and local environmental conditions are strongly correlated. Increasing dispersal and shortening environmental correlations weaken the strength of coexistence regionally and shift the dominant coexistence mechanism from fitness-density covariance to the spatial storage effect, while increasing local diversity. Analysis of the physical and biological determinants of these mechanisms improves understanding of traditional concepts of environmental filters, mass effects, and species sorting. Our results highlight the limitations of the binary distinction between local communities and a species pool and emphasize species coexistence as a problem of multiple scales in space and time.
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Yu, Xiaoju, Rongguo Zhou, Hualiang Zhang, and Hao Xin. "A Microwave Direction of Arrival Estimation Technique Using a Single Antenna." IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2016. http://hdl.handle.net/10150/621549.
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A direction of arrival (DoA) estimation technique for broadband microwave signals is proposed using a single ultrawideband antenna. It is inspired by the sound source localization ability of a human auditory system using just one ear (monaural localization). By exploiting the incident angle-dependent frequency response of a wideband antenna, the DoA of a broadband microwave signal can be estimated. The DoA estimation accuracies are evaluated for two antenna configurations and microwave signals with different signal-to-noise ratios. Encouraging the DoA estimation performance of the proposed technique is demonstrated in both simulation and experiment.
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Tan, Michelle M. "Field dependence and the effect of misleading cues to delineation on driver perception of road direction at right /." Adelaide, 1998. http://web4.library.adelaide.edu.au/theses/09ARPS/09arpst1612.pdf.
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Serbichenko, Daria. "Modal analysis of time-dependent structures using Derictional Derivatives." Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0059.
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Dans un grand nombre de domaines, l'analyse modale de structures est une composante capitale du dimensionnement. Pour l'identification des fréquences et modes propres, les logiciels de calcul éléments finis sont maintenant souvent utilisés et offrent des réponses rapides et satisfaisantes dans une grande majorité de cas. Cependant, lorsqu'une structure possède une géométrie qui varie au cours du temps ou alors lorsqu'une fissure se propage dans cette structure, les méthodes classiques employées peuvent être contraignantes et consommatrice de temps CPU (remaillage, résolution itérative de problèmes aux valeurs propres...), surtout si l'on veut suivre l'évolution des solutions propres.Dans ces travaux de doctorat, une méthode originale est proposée afin d’améliorer la gestion de l’analyse modale de structures subissant des changements de forme au cours du temps. Celle-ci est basée sur les dérivées directionnelles et sur la méthode X-FEM. En effet, les dérivées directionnelles permettent de prédire l’évolution des solutions propres entre deux configurations temporelles de la structure et X-FEM permet de s’affranchir des contraintes liées au maillage de chacune des configurations. Grâce à des critères spécifiquement développés, la méthodologie a été testée pour des cas de problèmes plans et axysymétrique. Les résultats obtenus en regard des méthodes classiques et les conclusions qu’elles peuvent amener, permettent de voir les nombreux avantages de l’outil que nous avons proposéIn many industrial fields, modal analysis of structures is a primary key during the design. Finite Element Method is often used to identify both natural frequencies and shapes, offering quick and satisfactory answers in most cases. However, when a structure possesses a time-dependent geometry or if the structure is subjected to a crack propagation, the standards methods used can be constraining. They can also be CPU time consuming (due to remeshing, iterative solving of eigenvalue problems…), especially if one wants to track the evolution of the eigensolutions.In this research work, an original method is proposed to improve the management of finding the evolution of eigensolutions in case of time-dependent structures. This methology is based on the combination of directional derivatives and X-FEM. The directional derivatives allow to estimate the evolution of the eigensolutions between two configurations of the structure and X-FEM overcomes the constraints related to mesh generation of each configuration. Through specific developed criteria, the methodology has been tested for cases of plane and axisymmetric problems. The results obtained in comparison to the standard modal analyses and the conclusions that they can bring, highlight the advantages of the numerical tool that we proposed
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Qamar, Raheel. "Dependence of the Kinetic Mechanism of Adenosine 3',5'-Monophosphate Dependent Protein Kinase Catalytic Subunit in the Direction of Magnesium Adenosine 5'-Diphosphate Phosphorylation on pH and the Concentration of Free Magnesium Ions." Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc277956/.
Full textAbstract:
To define the overall kinetic and chemical mechanism of adenosine 3',5'-monophosphate dependent protein kinase catalytic subunit, the mechanism in the direction of MgADP phosphorylation was determined, using studies of initial velocity in the absence and presence of dead-end inhibitors. The kinetic mechanism was determined as a function of uncomplexed Mg^2+ (Mg_f) at pH 7.2 and as a function of pH at low (0.5 mM) Mg_f. At pH 7.2 data are consistent with a random kinetic mechanism in the direction of MgADP phosphorylation with both pathways allowed: the pathway in which MgADP binds to enzyme prior to phosphorylated peptide (PSP) and that in which PSP binds before MgADP. One or the other pathway predominates, depending on Mg_f concentration. At 0.5 mM Mg_f, the mechanism is steady-state ordered with the pathway where PSP binds first preferred; at 10 mM Mg_f, the mechanism is equilibrium ordered, and the pathway in which MgADP binds first preferred. This change in mechanism to equilibrium ordered is due to an increase in affinity of enzyme for MgADP and a decrease in affinity for PSP. There is also a pH-dependent change in mechanism at 0.5 mM Mg_f. At pH 6 the mechanism is equilibrium ordered with the pathway where PSP binds first preferred. At pH 7.6 the mechanism is ordered with MgADP binding first. The log V/E_t vs. pH profile is pH-independent, suggesting only the correctly protonated form of each substrate binds to enzyme. The log V/K_MgADP vs. PH profile gives a pK of 7, likely that of a general acid, which must be protonated for activity. The pK_iPSP vs. pH profile gives a pK of 6.5, likely reflecting the peptide phosphoryl group, which must be unprotonated for activity.
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Ayotte, Dana C. (Dana Christine). "Direction-dependent constriction flow in a poroelastic solid : a model of the intervertebra disc valve." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/46051.
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Atemkeng, Marcellin T. "Data compression, field of interest shaping and fast algorithms for direction-dependent deconvolution in radio interferometry." Thesis, Rhodes University, 2017. http://hdl.handle.net/10962/6324.
Full textAbstract:
In radio interferometry, observed visibilities are intrinsically sampled at some interval in time and frequency. Modern interferometers are capable of producing data at very high time and frequency resolution; practical limits on storage and computation costs require that some form of data compression be imposed. The traditional form of compression is simple averaging of the visibilities over coarser time and frequency bins. This has an undesired side effect: the resulting averaged visibilities “decorrelate”, and do so differently depending on the baseline length and averaging interval. This translates into a non-trivial signature in the image domain known as “smearing”, which manifests itself as an attenuation in amplitude towards off-centre sources. With the increasing fields of view and/or longer baselines employed in modern and future instruments, the trade-off between data rate and smearing becomes increasingly unfavourable. Averaging also results in baseline length and a position-dependent point spread function (PSF). In this work, we investigate alternative approaches to low-loss data compression. We show that averaging of the visibility data can be understood as a form of convolution by a boxcar-like window function, and that by employing alternative baseline-dependent window functions a more optimal interferometer smearing response may be induced. Specifically, we can improve amplitude response over a chosen field of interest and attenuate sources outside the field of interest. The main cost of this technique is a reduction in nominal sensitivity; we investigate the smearing vs. sensitivity trade-off and show that in certain regimes a favourable compromise can be achieved. We show the application of this technique to simulated data from the Jansky Very Large Array and the European Very Long Baseline Interferometry Network. Furthermore, we show that the position-dependent PSF shape induced by averaging can be approximated using linear algebraic properties to effectively reduce the computational complexity for evaluating the PSF at each sky position. We conclude by implementing a position-dependent PSF deconvolution in an imaging and deconvolution framework. Using the Low-Frequency Array radio interferometer, we show that deconvolution with position-dependent PSFs results in higher image fidelity compared to a simple CLEAN algorithm and its derivatives.
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Kokten, Selen. "Bounding Procedures On Bi-directional Labeling Algorithm Of Time Dependent Vehicle Routing Problem With Time Windows In Branch-and-cut-and-price Framework." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613790/index.pdf.
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In this thesis we consider a Time-Dependent Vehicle Routing Problem with Time Windows
(TDVRPTW) which is solved by a Branch and Cut and Price (BCP) algorithm. The decomposition
of an arc based formulation leads to a set-partitioning problem as the master problem,
and a Time-Dependent Elementary Shortest Path Problem with Resource Constraints (TDESPPRC)
as the pricing problem. The main contribution of this thesis is the modified fathoming
and bounding procedures applied on bi-directional Time-Dependent Labeling algorithm
(TDL) which is used solve the TDESPPRC. The aim of the fathoming proposed is to solve
TDVRPTW more efficiently by not extending the unproductive labels in bi-directional TDL
algorithm. Moreover, an arc bounding model is introduced to stop the extension of labels as
an alternative to resource bounding used in bi-directional search. In addition, independent
from the work on TDVRPTW, the thesis includes an effects analysis of a new customer on
Kuehne+Nagel(K+N) Netherlands Fast Moving Consumer Goods (FMCG) and returns distribution
network. This study focused on analyzing the current performance of the distribution
network and evaluating the scenarios for K+N&rsquos future distribution network by a simulation study.
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Hausgen, Paul E. "A thermal analysis of an alkali metal thermal to electric converter with geometrically designed interior surfaces exhibiting directionally dependent radiative properties." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16701.
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Rouf, Hasan. "Unconditionally stable finite difference time domain methods for frequency dependent media." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/unconditionally-stable-finite-difference-time-domain-methods-for-frequency-dependent-media(50e4adf1-d1e4-4ad2-ab2d-70188fb8b7b6).html.
Full textAbstract:
The efficiency of the conventional, explicit finite difference time domain (FDTD)method is constrained by the upper limit on the temporal discretization, imposed by the Courant–Friedrich–Lewy (CFL) stability condition. Therefore, there is a growing interest in overcoming this limitation by employing unconditionally stable FDTD methods for which time-step and space-step can be independently chosen. Unconditionally stable Crank Nicolson method has not been widely used in time domain electromagnetics despite its high accuracy and low anisotropy. There has been no work on the Crank Nicolson FDTD (CN–FDTD) method for frequency dependent medium. In this thesis a new three-dimensional frequency dependent CN–FDTD (FD–CN–FDTD) method is proposed. Frequency dependency of single–pole Debye materials is incorporated into the CN–FDTD method by means of an auxiliary differential formulation. In order to provide a convenient and straightforward algorithm, Mur’s first-order absorbing boundary conditions are used in the FD–CN–FDTD method. Numerical tests validate and confirm that the FD–CN–FDTD method is unconditionally stable beyond the CFL limit. The proposed method yields a sparse system of linear equations which can be solved by direct or iterative methods, but numerical experiments demonstrate that for large problems of practical importance iterative solvers are to be used. The FD–CN–FDTD sparse matrix is diagonally dominant when the time-stepis near the CFL limit but the diagonal dominance of the matrix deteriorates with the increase of the time-step, making the solution time longer. Selection of the matrix solver to handle the FD–CN–FDTD sparse system is crucial to fully harness the advantages of using larger time-step, because the computational costs associated with the solver must be kept as low as possible. Two best–known iterative solvers, Bi-Conjugate Gradient Stabilised (BiCGStab) and Generalised Minimal Residual (GMRES), are extensively studied in terms of the number of iteration requirements for convergence, CPU time and memory requirements. BiCGStab outperforms GMRES in every aspect. Many of these findings do not match with the existing literature on frequency–independent CN–FDTD method and the possible reasons for this are pointed out. The proposed method is coded in Fortran and major implementation techniques of the serial code as well as its parallel implementation in Open Multi-Processing (OpenMP) are presented. As an application, a simulation model of the human body is developed in the FD–CN–FDTD method and numerical simulation of the electromagnetic wave propagation inside the human head is shown. Finally, this thesis presents a new method modifying the frequency dependent alternating direction implicit FDTD (FD–ADI–FDTD) method. Although the ADI–FDTD method provides a computationally affordable approximation of the CN–FDTD method, it exhibits a loss of accuracy with respect to the CN-FDTD method which may become severe for some practical applications. The modified FD–ADI–FDTD method can improve the accuracy of the normal FD–ADI–FDTD method without significantly increasing the computational costs.
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Al-Sader, Mohamed. "Gaze-driven interaction in video games." Thesis, Linköpings universitet, Medie- och Informationsteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-156718.
Full textAbstract:
The introduction of input devices with natural user interfaces in gaming hardware has changed the way we interact with games. Hardware with motion-sensing and gesture recognizing capabilities remove the constraint of interacting with games through typical traditional devices like mouse-keyboard and gamepads. This changes the way we approach games and how the game communicates back to us as the player opening new levels of interactivity. This thesis covers how eye tracker technology can be used to affect rendering effects in games.
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Smith, Daniel J. "Rapid determination of temperature-dependent parameters for the crystal viscoplasticity model." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43670.
Full textAbstract:
Thermomechanical fatigue life prediction is important in the design of Ni-base superalloy components in gas turbine engines and requires a stress-strain analysis for accurate results. Crystal viscoplasticity models are an ideal tool for this stress-strain analysis of Ni-base superalloys as they can capture not only the anomalous yielding behavior, but also the non-Schmid effect, the strain rate dependence, and the temperature dependence of typically large grained directionally-solidified and single crystal alloys. However, the model is difficult to calibrate even for isothermal conditions because of the interdependencies between parameters meant to capture different but similar phenomena at different length scales, many tied to a particular slip system. The need for the capacity to predict the material response over a large temperature range, which is critical for the simulation of hot section gas turbine components, causes the determination of parameters to be even more difficult since some parameters are highly temperature dependent. Rapid parameter determination techniques are therefore needed for temperature-dependent parameterizations so that the effort needed to calibrate the model is reduced to a reasonable level.
Specific parameter determination protocols are established for a crystal viscoplasticity model implemented in ABAQUS through a user material subroutine. Parameters are grouped to reduce interdependencies and a hierarchical path through the groups and the parameters within each group is established. This dual level hierarchy creates a logical path for parameter determination which further reduces the interdependencies between parameters, allowing for rapid parameter determination.
Next, experiments and protocols are established to rapidly provide data for calibration of the temperature-dependencies of the viscoplasticity. The amount of data needed to calibrate the crystal viscoplasticity model over a wide temperature range is excessively large due to the number of parameters that it contains which causes the amount of time spent in the experimentation phase of parameter determination to be excessively large. To avoid this lengthy experimentation phase each experiment is designed to contain as much relevant data as possible. This is accomplished through the inclusion of multiple strain rates in each experiment with strain ranges sufficiently large to clearly capture the inelastic response.
The experimental and parameter determination protocols were exercised by calibrating the model to the directionally-solidified Ni-bas superalloy DS-CM247LC. The resulting calibration describes the material's behavior in multiple loading orientations and over a wide temperature range of 20 °C to 1050 °C. Several parametric studies illustrate the utility of the calibrated model.
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Brink, Stephen Isaac. "Learning in silicon: a floating-gate based, biophysically inspired, neuromorphic hardware system with synaptic plasticity." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50143.
Full textAbstract:
The goal of neuromorphic engineering is to create electronic systems that model the behavior of biological neural systems. Neuromorphic systems can leverage a combination of analog and digital circuit design techniques to enable computational modeling, with orders of magnitude of reduction in size, weight, and power consumption compared to the traditional modeling approach based upon numerical integration. These benefits of neuromorphic modeling have the potential to facilitate neural modeling in resource-constrained research environments. Moreover, they will make it practical to use neural computation in the design of intelligent machines, including portable, battery-powered, and energy harvesting applications. Floating-gate transistor technology is a powerful tool for neuromorphic engineering because it allows dense implementation of synapses with nonvolatile storage of synaptic weights, cancellation of process mismatch, and reconfigurable system design. A novel neuromorphic hardware system, featuring compact and efficient channel-based model neurons and floating-gate transistor synapses, was developed. This system was used to model a variety of network topologies with up to 100 neurons. The networks were shown to possess computational capabilities such as spatio-temporal pattern generation and recognition, winner-take-all competition, bistable activity implementing a "volatile memory", and wavefront-based robotic path planning. Some canonical features of synaptic plasticity, such as potentiation of high frequency inputs and potentiation of correlated inputs in the presence of uncorrelated noise, were demonstrated. Preliminary results regarding formation of receptive fields were obtained. Several advances in enabling technologies, including methods for floating-gate transistor array programming, and the creation of a reconfigurable system for studying adaptation in floating-gate transistor circuits, were made.
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Higham, Christopher John. "Modeling larval connectivity among coral habitats, Acropora palmata populations, and marine protected areas in the Florida Keys National Marine Sanctuary." [Tampa, Fla] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0001918.
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Bennett, James Edward Matthew. "Pattern formation in neural circuits by the interaction of travelling waves with spike-timing dependent plasticity." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:29387080-4213-4179-98b6-bf3d4c49dd00.
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Spontaneous travelling waves of neuronal activity are a prominent feature throughout the developing brain and have been shown to be essential for achieving normal function, but the mechanism of their action on post-synaptic connections remains unknown. A well-known and widespread mechanism for altering synaptic strengths is spike-timing dependent plasticity (STDP), whereby the temporal relationship between the pre- and post-synaptic spikes determines whether a synapse is strengthened or weakened. Here, I answer the theoretical question of how these two phenomenon interact: what types of connectivity patterns can emerge when travelling waves drive a downstream area that implements STDP, and what are the critical features of the waves and the plasticity rules that shape these patterns? I then demonstrate how the theory can be applied to the development of the visual system, where retinal waves are hypothesised to play a role in the refinement of downstream connections. My major findings are as follows. (1) Mathematically, STDP translates the correlated activity of travelling waves into coherent patterns of synaptic connectivity; it maps the spatiotemporal structure in waves into a spatial pattern of synaptic strengths, building periodic structures into feedforward circuits. This is analogous to pattern formation in reaction diffusion systems. The theory reveals a role for the wave speed and time scale of the STDP rule in determining the spatial frequency of the connectivity pattern. (2) Simulations verify the theory and extend it from one-dimensional to two-dimensional cases, and from simplified linear wavefronts to more complex realistic and noisy wave patterns. (3) With appropriate constraints, these pattern formation abilities can be harnessed to explain a wide range of developmental phenomena, including how receptive fields (RFs) in the visual system are refined in size and topography and how simple-cell and direction selective RFs can develop. The theory is applied to the visual system here but generalises across different brain areas and STDP rules. The theory makes several predictions that are testable using existing experimental paradigms.
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Silva, Júlia Reis da. "A clínica psicanalítica das toxicomanias." Universidade do Estado do Rio de Janeiro, 2010. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=2312.
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Esta dissertação propõe investigar o fenômeno das toxicomanias como conseqüência do declínio da imago paterna na cultura atual. O estudo foi iniciado pelo cotejamento do tema na teoria de Sigmund Freud e pela interpretação de que a toxicomania é uma resposta à satisfação sexual recalcada. A pesquisa explorou ainda esse tema no ensino escrito e falado de Jacques Lacan. O uso abusivo de drogas promove um gozo auto-erótico que busca liberar o toxicômano de ter que lidar com os impasses da castração. Por tal motivo foi explorada a queda da operatividade do significante Nome-do-Pai na atualidade. Se o significante autentica o sujeito do inconsciente e opera como regulador de gozo, a ascensão do objeto a ao zênite social provoca efeitos decisivos sobre o sujeito: a inconsistência do Outro, a predominância do discurso da ciência e do capitalista, e a proliferação dos novos sintomas. Nesse sentido, a segunda clínica de Lacan, a chamada clínica borromeana, foi utilizada para interpretar os modos de gozo na contemporaneidade. O atendimento de um paciente psicótico que faz uso de drogas mostrou a importância de trabalhar o diagnóstico diferencial para orientar a direção do tratamento.This dissertation proposes to investigate the chemical dependency phenomenon as a consequence of the paternal imago decline in current culture. The study begun by collating the theme in Sigmund Freud theory and by the interpretation that chemical dependency is a response to repressed sexual satisfaction. The research also explored this theme in Jacques Lacans written and spoken teaching. The abusive use of drugs promotes a self-erotic enjoyment that searches to release the chemical dependent from dealing with the castration impasses. Therefore, the operative decrease of the significant Name-of-Father in nowadays was explored. If the significant authenticates the unconscious subject and operates as a regulator of enjoyment, the rise of the a object to the social zenith causes a decisive effect on the subject: the inconsistency of the Other, the predominance of the science and capitalist discourse and the proliferation of new symptoms. Accordingly, the second clinic of Lacan, called borromean clinic, was used to interpret the ways of enjoyment in contemporary period. The surveillance of a psychotic patient who uses drugs showed the importance of working on the differentials diagnosis in order to treatment direction.
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Grieves, Roderick McKinlay. "The neural basis of a cognitive map." Thesis, University of Stirling, 2015. http://hdl.handle.net/1893/21878.
Full textAbstract:
It has been proposed that as animals explore their environment they build and maintain a cognitive map, an internal representation of their surroundings (Tolman, 1948). We tested this hypothesis using a task designed to assess the ability of rats to make a spatial inference (take a novel shortcut)(Roberts et al., 2007). Our findings suggest that rats are unable to make a spontaneous spatial inference. Furthermore, they bear similarities to experiments which have been similarly unable to replicate or support Tolman’s (1948) findings. An inability to take novel shortcuts suggests that rats do not possess a cognitive map (Bennett, 1996). However, we found evidence of alternative learning strategies, such as latent learning (Tolman & Honzik, 1930b) , which suggest that rats may still be building such a representation, although it does not appear they are able to utilise this information to make complex spatial computations. Neurons found in the hippocampus show remarkable spatial modulation of their firing rate and have been suggested as a possible neural substrate for a cognitive map (O'Keefe & Nadel, 1978). However, the firing of these place cells often appears to be modulated by features of an animal’s behaviour (Ainge, Tamosiunaite, et al., 2007; Wood, Dudchenko, Robitsek, & Eichenbaum, 2000). For instance, previous experiments have demonstrated that the firing rate of place fields in the start box of some mazes are predictive of the animal’s final destination (Ainge, Tamosiunaite, et al., 2007; Ferbinteanu & Shapiro, 2003). We sought to understand whether this prospective firing is in fact related to the goal the rat is planning to navigate to or the route the rat is planning to take. Our results provide strong evidence for the latter, suggesting that rats may not be aware of the location of specific goals and may not be aware of their environment in the form of a contiguous map. However, we also found behavioural evidence that rats are aware of specific goal locations, suggesting that place cells in the hippocampus may not be responsible for this representation and that it may reside elsewhere (Hok, Chah, Save, & Poucet, 2013). Unlike their typical activity in an open field, place cells often have multiple place fields in geometrically similar areas of a multicompartment environment (Derdikman et al., 2009; Spiers et al., 2013). For example, Spiers et al. (2013) found that in an environment composed of four parallel compartments, place cells often fired similarly in multiple compartments, despite the active movement of the rat between them. We were able to replicate this phenomenon, furthermore, we were also able to show that if the compartments are arranged in a radial configuration this repetitive firing does not occur as frequently. We suggest that this place field repetition is driven by inputs from Boundary Vector Cells (BVCs) in neighbouring brain regions which are in turn greatly modulated by inputs from the head direction system. This is supported by a novel BVC model of place cell firing which predicts our observed results accurately. If place cells form the neural basis of a cognitive map one would predict spatial learning to be difficult in an environment where repetitive firing is observed frequently (Spiers et al., 2013). We tested this hypothesis by training animals on an odour discrimination task in the maze environments described above. We found that rats trained in the parallel version of the task were significantly impaired when compared to the radial version. These results support the hypothesis that place cells form the neural basis of a cognitive map; in environments where it is difficult to discriminate compartments based on the firing of place cells, rats find it similarly difficult to discriminate these compartments as shown by their behaviour. The experiments reported here are discussed in terms of a cognitive map, the likelihood that such a construct exists and the possibility that place cells form the neural basis of such a representation. Although the results of our experiments could be interpreted as evidence that animals do not possess a cognitive map, ultimately they suggest that animals do have a cognitive map and that place cells form a more than adequate substrate for this representation.
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Vanappelghem, Cédric. "Le rôle et l'efficacité du conseil d'administration selon sa sympathie à l'égard du dirigeant : le cas des firmes françaises cotées." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAG004/document.
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Notre thèse s'intéresse aux conséquences de la sympathie du conseil d'administration (CA) vis-à-vis du dirigeant en termes de politique financière et de performance de la firme. La gouvernance d'entreprise est généralement étudiée à l'aide de la théorie de l'agence. Elle conçoit le CA comme un dispositif de surveillance disciplinaire du dirigeant protégeant les droits des financeurs. Il s'assure que les décisions prises par le dirigeant sont conformes aux intérêts des financeurs. Cette vision de la gouvernance s'oppose à celle défendue par la théorie de la dépendance aux ressources. Selon cette dernière, le CA a avant tout un rôle d'accompagnement stratégique du dirigeant. Il exerce un rôle d'interface entre la firme et son environnement, ce qui permet au dirigeant de prendre des décisions créatrices de valeur. La surveillance disciplinaire et l'accompagnement stratégique sont peu compatibles. La composition du CA détermine quel rôle est renforcé au détriment de l'autre. Ainsi, les administrateurs en relation avec le dirigeant accroissent les compétences d'accompagnement stratégique du CA tandis que sa capacité à restreindre la marge de manœuvre du dirigeant diminue. Nous nous sommes focalisés sur 78 grandes entreprises françaises cotées. Nous avons convenu qu'un administrateur peut être en relation avec le dirigeant s'ils appartiennent aux mêmes réseaux d'anciens étudiants d'une institution universitaire donnée. Les données de gouvernance utilisées ont été collectées manuellement dans les rapports annuels émis par les firmes entre 2007 et 2011. Les informations concernant les dirigeants et les administrateurs sont issues dictionnaire biographique Who's Who in France 2013 ou dans les notices biographiques des rapports annuels. Nous avons tout d'abord pu constater que la présence d'administrateurs en relation avec le dirigeant conduit à une diminution du niveau de dividendes. En même temps, le dirigeant favorise un financement par des dettes au détriment des capitaux propres. Nous avons également montré que cette relation dépend de la structure de propriété de la firme. Ainsi, le constat précédent demeure pour les firmes au capital fortement concentré, ce qui est conforme à la théorie de la dépendance aux ressources. En revanche, le dirigeant préfère financer la firme par capitaux propres mais le niveau de dividendes reste inchangé dans le cas des firmes au capital dilué. Ceci est conforme à la théorie de l'agence. Ainsi, la capacité du dirigeant à décider d'une politique financière servant ses intérêts à l'aide de ses relations sociales dépend de la structure de propriété de la firme. Lorsque le capital est concentré, l'actionnaire majoritaire préfère financer la firme par de la dette obtenue à moindre coût grâce au dirigeant et ses relations sociales. Cela empêche l'entrée d'autres actionnaires au capital. Le fait de ne pas verser de dividendes permet de renforcer les capacités financières de la firme. Lorsque le capital est dilué, le dirigeant peut éviter la pression disciplinaire de l'endettement. Suite à cela nous avons montré, conformément à cette même théorie, que le coût du capital croît lorsque des administrateurs connaissent le dirigeant. La relation est plus forte pour les firmes peu connues des marchés. Enfin, la performance croît en fonction de la sympathie du CA. Cela est conforme à la théorie de la dépendance aux ressources. Nous nous sommes également aperçus que l'effet bénéfique des relations du dirigeant se retrouve uniquement pour les firmes en phase de croissance. Ainsi, même si elle est source de coûts d'agence, la sympathie du conseil d'administration à l'égard du dirigeant est bénéfique pour les firmes ayant besoin d'accompagnement stratégique tandis qu'elle est davantage néfaste aux firmes parvenues à maturitéThis dissertation deals with the consequences of board friendliness on the financial policy and the performance of the firm. It revolves around four empirical studies. Until now, the study of corporate governance was based on Agency Theory. It conceives the board of directors as aimed at monitoring the Chief Executive Officer (CEO) in order to protect claimholders' interests. However, Resource Dependence Theory states that the board of directors is aimed at bringing information and resources to the CEO. These two roles are opposing, and board composition determines its dominant role toward the other one. Thus, CEO social ties enhance the advising role of the board and impede its monitoring role. Our dissertation is based on these two theories. Our studies are based on 78 French firms. We decided that a director was a social tie of the CEO when they were graduated from the same university or grande ecole (Polytechnique, Ecole Nationale d'Administration, HEC ...). Corporate governance data are manually collected in the annual reports launched by the firm between 2007 and 2011. Data concerning CEO and directors vita are extracted from the biographical dictionary Who's Who in France 2013 or the annual reports. We first find that friendly boards lead to fewer dividends and higher leverage. We decided to refine our results and analyze the effect of ownership concentration on these two relationships. We found that these relationships remained in a context of high ownership concentration, but the relation between board friendliness and leverage turned negative. The relation between board friendliness and dividends remained negative in a context of high ownership concentration but disapeared in a context of low ownership concentration. Consequently, the possibility for the CEO to use his social ties in order to set up a financial policy to entrench depends on ownership concentration. The higher ownership concentration, the harder it is for the CEO to entrench. In the third empirical study, we found that CEO social ties lead to a higher implied cost of capital. This relationship is stronger for the most risky and opaque firms. Finally, we find that friendly boards increase the performance of the firm. More precisely, this positive effect of board friendliness is concentrated on opaque firms with a lot of growth opportunities. Consequently, even if friendly boards generate agency costs, shareholders accept them when the firm has a lot of growth opportunities because the CEO needs advice to exploit investments properly. When the CEO does not have advisory needs, CEO social ties prevent the financing of the firm at an optimal cost of capital insofar as the CEO is only entrenched
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Boudjellal, Abdelouahab. "Contributions à la localisation et à la séparation de sources." Thesis, Orléans, 2015. http://www.theses.fr/2015ORLE2063.
Full textAbstract:
Les premières recherches en détection, localisation et séparation de signaux remontent au début du 20ème siècle. Ces recherches sont d’actualité encore aujourd’hui, notamment du fait de la croissance rapide des systèmes de communications constatée ces deux dernières décennies. Par ailleurs, la littérature du domaine consacre très peu d’études relatives à certains contextes jugés difficiles dont certains sont traités dans cette thèse. Ce travail porte sur la localisation de signaux par détection des temps d’arrivée ou estimation des directions d’arrivée et sur la séparation de sources dépendantes ou à module constant. L’idée principale est de tirer profit de certaines informations a priori disponibles sur les signaux sources telles que la parcimonie, la cyclostationarité, la non-circularité, le module constant, la structure autoregressive et les séquences pilote dans un contexte coopératif. Une première partie détaille trois contributions : (i) un nouveau détecteur pour l’estimation des temps d’arrivée basé sur la minimisation de la probabilité d’erreur ; (ii) une estimation améliorée de la puissance du bruit, basée sur les statistiques d’ordre ; (iii) une quantification de la précision et de la résolution de l’estimation des directions d’arrivée au regard de certains a priori considérés sur les sources. Une deuxième partie est consacrée à la séparation de sources exploitant différentes informations sur celles-ci : (i) la séparation de signaux de communication à module constant ; (ii) la séparation de sources dépendantes connaissant la nature de la dépendance et (iii) la séparation de sources autorégressives dépendantes connaissant la structure autorégressiveSignal detection, localization, and separation problems date back to the beginning of the twentieth century. Nowadays, this subject is still a hot topic receiving more and more attention, notably with the rapid growth of wireless communication systems that arose in the last two decades and it turns out that many challenging aspects remain poorly addressed by the available literature relative to this subject. This thesis deals with signal detection, localization using temporal or directional measurements, and separation of dependent source signals. The main objective is to make use of some available priors about the source signals such as sparsity, cyclo-stationarity, non-circularity, constant modulus, autoregressive structure or training sequences in a cooperative framework. The first part is devoted to the analysis of (i) signal’s time-of-arrival estimation using a new minimum error rate based detector, (ii) noise power estimation using an improved order-statistics estimator and (iii) side information impact on direction-of-arrival estimation accuracy and resolution. In the second part, the source separation problem is investigated at the light of different priors about the original sources. Three kinds of prior have been considered : (i) separation of constant modulus communication signals, (ii) separation of dependent source signals knowing their dependency structure and (iii) separation of dependent autoregressive sources knowing their autoregressive structure
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Hunter, Brandon. "Channel Probing for an Indoor Wireless Communications Channel." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/64.
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The statistics of the amplitude, time and angle of arrival of multipaths in an indoor environment are all necessary components of multipath models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath parameters at 2.4 GHz for multiple locations in an indoor environment. Another system was built to measure the angle of transmission for a 6 GHz channel. The addition of this parameter allows spatial diversity at the transmitter along with the receiver to be simulated. The process of going from raw measurement data to discrete arrivals and then to clustered arrivals is analyzed. Many possible errors associated with discrete arrival processing are discussed along with possible solutions. Four clustering methods are compared and their relative strengths and weaknesses are pointed out. The effects that errors in the clustering process have on parameter estimation and model performance are also simulated.
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Shum, Alex. "Optimal Direction-Dependent Path Planning for Autonomous Vehicles." Thesis, 2014. http://hdl.handle.net/10012/8353.
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The focus of this thesis is optimal path planning. The path planning problem is posed as an optimal control problem, for which the viscosity solution to the static Hamilton-Jacobi-Bellman (HJB) equation is used to determine the optimal path. The Ordered Upwind Method (OUM) has been previously used to numerically approximate the viscosity solution of the static HJB equation for direction-dependent weights.
The contributions of this thesis include an analytical bound on the convergence rate of the OUM for the boundary value problem to the viscosity solution of the HJB equation. The convergence result provided in this thesis is to our knowledge the tightest existing bound on the convergence order of OUM solutions to the viscosity solution of the static HJB equation. Only convergence without any guarantee of rate has been previously shown.
Navigation functions are often used to provide controls to robots. These functions can suffer from local minima that are not also global minima, which correspond to the inability to find a path at those minima. Provided the weight function is positive, the viscosity solution to the static HJB equation cannot have local minima. Though this has been discussed in literature, a proof has not yet appeared. The solution of the HJB equation is shown in this work to have no local minima that is not also global. A path can be found using this method.
Though finding the shortest path is often considered in optimal path planning, safe and energy efficient paths are required for rover path planning. Reducing instability risk based on tip-over axes and maximizing solar exposure are important to consider in achieving these goals. In addition to obstacle avoidance, soil risk and path length on terrain are considered. In particular, the tip-over instability risk is a direction-dependent criteria, for which accurate approximate solutions to the static HJB equation cannot be found using the simpler Fast Marching Method.
An extension of the OUM to include a bi-directional search for the source-point path planning problem is also presented. The solution is found on a smaller region of the environment, containing the optimal path. Savings in computational time are observed.
A comparison is made in the path planning problem in both timing and performance between a genetic algorithm rover path planner and OUM. A comparison in timing and number of updates required is made between OUM and several other algorithms that approximate the same static HJB equation. Finally, the OUM algorithm solving the boundary value problem is shown to converge numerically with the rate of the proven theoretical bound.
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Chueh, Cheng-Chang, and 闕成昌. "Ferromagnetic resonance of permalloy microstructures : dependence of direction of external magnetic fields." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/c5mhj5.
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碩士國立中興大學
奈米科學研究所
101
We report the ferromagnetic resonance of permalloy microstructures. The chip with permalloy microstructures are flipped and attached on a ceramic substrate with a grounded coplanar waveguide. We define different microstructure patterns, including dot array and rod-like array, on GaAs substrates by e-beam lithography. Three kinds of samples were investigated. The first one is a bare 30 nm thick permalloy thin film on a 3 mm × 2 mm GaAs substrate, the second one is a permalloy dot array consisted of 500-nm-diameter dots with pitch of 200 nm and thickness of 175 nm on a 2 mm × 1 mm GaAs substrate, and the third one is a rod-like permalloy array consisted of 1-um-long, 600-nm-wide rod-likes with pitch of 600 nm and thickness of 30 nm on a 2 mm × 1 mm GaAs substrate. We measure the ferromagnetic resonance characteristics of samples by applying the microwave signal in the frequency range from 40 MHz to 13.5 GHz and a magnetic field from -7900 Oe to +7900 Oe. The transmission and reflection signals are measured by a vector network analyzer (VNA). The measurement data reveal that the magnetic field of the FMR increases as the microwave frequency increases. At the same microwave frequency, the field of FMR evolves to lower field as the angle of the applied field is varied from 0° to 90°. We found that the variation of the field of FMR is the greatest as the angle approach to zero for these samples. We can deduce the gyromagnetic ratio(r), the Gilbert damping parameter(a), and the Demagnetizing factor(Nx、Ny、Nz) by using Kittel''s equation.
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Chuang, ChienHui. "Long-range directional movement of an interphase chromosome site dependent on actin and nuclear myosin /." 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3269863.
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Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4214. Adviser: Andrew S. Belmont. Includes supplementary digital materials. Includes bibliographical references (leaves 64-71) Available on microfilm from Pro Quest Information and Learning.
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Lu, Y., Glen P. Thompson, D. Lyu, Philip D. Caton-Rose, Philip D. Coates, and Y. Men. "Orientation direction dependency of cavitation in pre-oriented isotactic polypropylene at large strains." 2018. http://hdl.handle.net/10454/17002.
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YesOrientation direction dependency of whitening activated at large strains was studied using four pre-oriented isotactic polypropylene (iPP) samples with different molecular weights stretched along different directions with respect to the pre-orientation (0°, 45°, and 90°) by means of in situ wide-, small-, and ultra-small-angle X-ray scattering techniques. A macroscopic fracture of iPP materials was also observed following the stress whitening at large strains. These two associated processes in pre-oriented iPP samples at elevated temperatures were found to be governed by not only the molecular weight of iPP but also the pre-orientation direction. For a certain pre-orientation direction of iPP, both the critical stress of cavitation induced-whitening and failure stress increased with increasing molecular weight. For one given molecular weight, the pre-oriented iPP showed the smallest critical stress for whitening and failure stress along the pre-orientation direction (0°) while the samples displayed larger values for the same behaviors when stretched at 45° or 90° with respect to the pre-orientation direction. Such behavior suggested that oriented amorphous networks, with different mechanical strengths, can be generated during the second deformation processes in these pre-oriented iPP samples. The evolution of inter-fibrillar tie chains in highly oriented amorphous networks was considered as the main factor controlling the response of the inner network to the external stress since the cavitation-induced whitening activated at large strains was caused by the failure of load bearing inter-fibrillar tie chains in the oriented amorphous network.
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Kim, Hojeong. "Biophysics underlying bistable neurons with branching dendrites." Phd thesis, 2011. http://hdl.handle.net/10048/1832.
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The goal of this thesis is to investigate the biophysical basis underlying the nonlinear relationship between firing response and current stimulation in single motor neurons. After reviewing the relevant motoneuron physiology and theories that describe complex dendritic signaling properties, I hypothesize that at least five passive electrical properties must be considered to better understand the physiological input-output properties of motor neurons in vivo: input resistance, system time constant, and three signal propagation properties between the soma and dendrites that depend on the signal direction (i.e. soma to dendrites or vice versa) and type (i.e. direct (DC) or alternating (AC) current). To test my hypothesis, I begin with characterizing the signal propagation of the dendrites, by directly measuring voltage attenuations along the path of dendrites of the type-identified anatomical neuron models. Based on this characterization of dendritic signaling, I develop the novel realistic reduced modeling approach by which the complex geometry and passive electrical properties of anatomically reconstructed dendrites can be analytically mapped into simple two-compartment modeling domain without any restrictive assumptions. Combining mathematical analysis and computer simulations of my new reduced model, I show how individual biophysical properties (system input resistance, time constant and dendritic signaling) contribute to the local excitability of the dendrites, which plays an essential role in activating the plateau generating membrane mechanisms and subsequent nonlinear input-output relations in a single neuron. The biophysical theories and computer simulations in this thesis are primarily applied to motor neurons that compose the motor neuron pool for control of movement. However, the general features of the new reduced neuron modeling approach and important insights into neuronal computations are not limited to this area. My findings can be extended to other areas including artificial neural networks consisting of single compartment processors.Medical Sciences – Biomedical Engineering
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Chen, Shih-Min, and 陳仕珉. "In-situ Neutron Diffraction Measurements to Investigate the Additive-Direction-Dependent Deformation of Additive Manufactured (AM) Stainless Steel." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/9hwvnz.
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碩士國立交通大學
材料科學與工程學系奈米科技碩博士班
105
The field of additive manufacturing (AM) has experienced significant growth around all worlds. In engineering, selective laser melting (SLM) is an additive manufacturing process for building metallic parts. Metallic parts are created layer by layer to form a layered structure. The mechanical properties of metallic parts are attributed to the numbers of building layers and the orientation of defects which is relative to building direction. In this research, we prepared two types of samples made of PH15-5 stainless steel fabricated by two different building direction. One building direction is parallel to loading direction, called cylindrical sample, and the other building direction is perpendicular to loading direction. During the tensile test, we apply in-situ neutron diffraction measurements with two orthogonal detectors to resolve the differences from additive directions. Besides, we used rietveld software, MAUD and CMWP to understand the crystal structure, phase evolution and microstructures of this material. When we know the information about the difference properties between samples fabricated by two different building directions, the strategy of additive manufacturing can be described clearly.