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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Longitudinal target-spin azimuthal asymmetry in deeply-virtual compton scattering

Kopytin, Mikhail 29 November 2006 (has links)
In der vorliegenden Arbeit werden Ergebnisse vom Experiment HERMES präsentiert, welche eine azimutale Asymmetrie bezüglich des Spins des Protontargets zeigen, die von der Interferenz zwischen dem Bethe-Heitler und dem Tiefvirtuelle Compton Streuung (DVCS) Prozess herrührt. Diese Asymmetrie, auch als longitudinale Target-Spin Asymmetrie (LTSA) bezeichnet, erlaubt hauptsächlich den Zugang zur polarisierten verallgemeinerten Partonverteilungen (GPD) H-tilde. Die kinematische Abhängigkeit der LTSA von t, x_B und Q2 wurde gemessen und mit vorhandenen Messungen am Deuteron verglichen. Die Ergebnisse wurden mit theoretischen Berechungen und mit aktuellen Messungen des CLAS-Experiments verglichen. Die Daten, die zur Analyse in der vorliegenden Arbeit verwendet werden, wurden am HERMES Experiment bei DESY genommen, wobei im HERA-Speicherring Positronenstrahlen der Energie 27.5 GeV an Wasserstoff- und Deuterium-Gas-Targets gestreut wurden. Darüber hinaus werden Produktionstests des HELIX-128 3.0 chips diskutiert. Der Chip ist ein Frontend-Auslesechip beim Silizium-Rückstossdetektor. Letzterer ist Teil des HERMES-Rückstossdetektors, welcher den Target-Bereich umschliesst, um die Rückstossprodukte der exklusiven Prozesse zu detektieren. Das primäre Ziel dieses Detektors ist es, eine vollständigere Untersuchung von DVCS durch zusätzliche Registrierung der Rückstossprotonen zu ermöglichen. / In this thesis results from HERMES are reported on an azimuthal asymmetry with respect to the spin of the proton target, which is attributed to the interference between the Bethe-Heitler process and the Deeply Virtual Compton Scattering process. The asymmetry, also referred to as the longitudinal target-spin asymmetry (LTSA), gives access mainly to the polarized Generalized Parton Distribution H-tilde. The kinematic dependences of the LTSA on t, x_B and Q^2 are measured and compared with the corresponding measurements on the deuteron. The results are compared with theoretical calculations and with the recent CLAS measurements. The data, used for analysis in this thesis, have been accumulated by the HERMES experiment at DESY scattering the HERA 27.6 GeV positron beam off hydrogen and deuterium gas targets. Additionally, production tests of the HELIX128 3.0 chip are discussed. The chip is the frontend readout chip of the silicon recoil detector. The latter is a part of the HERMES recoil detector, which is built around the target area in order to detect the recoiling products of exclusive processes. The primary goal of this detector is to facilitate a more complete study of DVCS by registering also the recoiling protons.
2

Analysis and Comparison of eLearning Standards

Chen, Pin-Chung 18 July 2002 (has links)
Along with the development of Internet and information technology, there has been a huge revolution on the style of learning, since we¡¦ve entered a new century of elearning. At the present time, the learning resources accumulating in the Internet has been richer gradually. However, it also shows the problem about the difficulties of the management and integration of learning resources. Plenty of problems should be resolved, such as the difficulty on seeking resources and tests, low reusability, incapability of the transformation on different learning platforms, etc. On purpose to resolve these problems, various kinds of standards have been presented by many organizations. Although these standards are still under development, however, undoubtedly, they will play a very important role on the progress of the elearning. Because of the shortage of understandings and researches of this respect, we will have some discussions about the present problems resolved by the standards of elearning and the methods used upon them. Bereday¡¦s Comparative Method is adapted in this research. Four specific phases described as follows: Description Phase: Thoroughly and objectively describing each elearning standard. Interpretation Phase: Interpreting the meaning contained in the elearning standard according to the perspective of modularity, management, and continuity. Juxtaposition Phase: Defining the items on the comparison of each dimension based on content, quiz, leaner, and platform, and then concluding the key points of each standard in each item. Comparison Phase: Comparing each elearning standard item by item that is listed in the Juxtaposition Phase.
3

Modeling the behavior of the Linearly Tapered Slot Antenna

Kelly, Thomas P. 12 1900 (has links)
Approved for public release; distribution is unlimited / The Linearly Tapered Slot Antenna (LTSA) had been investigated and developed experimentally; its applications have primarily been based on empirical designs. An accurate theoretical model based on Moment Methods (MM) is developed here to study the radiation characteristics of the LTSA. Using the MM solutions to the reaction integral equation, this thesis presents an analysis to model and explain the LTSA behavior. The effects of variable design parameters on radiation patterns are studied. Discussion is augmented by relating predicted radiation patterns to calculated current distributions on the antenna surface. Conclusions are made regarding optimum designs for the LTSA. Relevant observations are made concerning the extensive computational tasks and the computer resources required for the MM model. / http://archive.org/details/modelingbehavior00kell / Major, United States Army
4

New results in dimension reduction and model selection

Smith, Andrew Korb 26 March 2008 (has links)
Dimension reduction is a vital tool in many areas of applied statistics in which the dimensionality of the predictors can be large. In such cases, many statistical methods will fail or yield unsatisfactory results. However, many data sets of high dimensionality actually contain a much simpler, low-dimensional structure. Classical methods such as principal components analysis are able to detect linear structures very effectively, but fail in the presence of nonlinear structures. In the first part of this thesis, we investigate the asymptotic behavior of two nonlinear dimensionality reduction algorithms, LTSA and HLLE. In particular, we show that both algorithms, under suitable conditions, asymptotically recover the true generating coordinates up to an isometry. We also discuss the relative merits of the two algorithms, and the effects of the underlying probability distributions of the coordinates on their performance. Model selection is a fundamental problem in nearly all areas of applied statistics. In particular, a balance must be achieved between good in-sample performance and out-of-sample prediction. It is typically very easy to achieve good fit in the sample data, but empirically we often find that such models will generalize poorly. In the second part of the thesis, we propose a new procedure for the model selection problem which generalizes traditional methods. Our algorithm allows the combination of existing model selection criteria via a ranking procedure, leading to the creation of new criteria which are able to combine measures of in-sample fit and out-of-sample prediction performance into a single value. We then propose an algorithm which provably finds the optimal combination with a specified probability. We demonstrate through simulations that these new combined criteria can be substantially more powerful than any individual criterion.
5

Formal Modeling Can Improve Smart Transportation Algorithm Development

Wathugala, Wathugala Gamage Dulan Manujinda 06 1900 (has links)
201 pages / Ensuring algorithms work accurately is crucial, especially when they drive safety critical systems like self-driving cars. We formally model a published distributed algorithm for autonomous vehicles to collaborate and pass thorough an intersection. Models are built and validated using the “Labelled Transition System Analyser” (LTSA). Our models reveal situations leading to deadlocks and crashes in the algorithm. We demonstrate two approaches to gain insight about a large and complex system without modeling the entire system: Modeling a sub system - If the sub system has issues, the super system too. Modeling a fast-forwarded state - Reveals problems that can arise later in a process. Some productivity tools developed for distributed system development are also presented. Manulator, our distributed system simulator, enables quick prototyping and debugging on a single workstation. LTSA-O, extension to LTSA, listens to messages exchanged in an execution of a distributed system and validates it against a model.
6

Netiesinių daugdarų atpažinimo metodų taikymo web-kamera gautiems vaizdų rinkiniams analizuoti tyrimas / Analysis of non-linear manifold learning methods applied on image collections provided by webcam

Petrauskas, Ignas 04 July 2014 (has links)
Šiame darbe nagrinėjami netiesiniai daugdarų atpažinimo metodai ir daugiamačių duomenų projekcijos metodai. Siūloma jais spręsti keliais laisvės laipsniais besisukančio objekto orientacijos radimo problemą. Aprašomi MDS, Trianguliacijos, Sammon, RPM, mRPM, CCA, PCA, LLE, LE, HLLE, LTSA, SMACOF ir Isomap metodai. Su kai kuriais iš jų atliekami web-kamera gautų galvos atvaizdų tyrimai. Isomap algoritmo pagrindu sukuriama programinė įranga ir su ja taipogi atliekami galvos orientacijos tyrimai. / This paper deals with Analysis of non-linear manifold learning methods and multidimensional data projection methods. It is proposed use them in solving problem of detection of orientation of object, moving in few degrees of freedom. Methods described: MDS, triangulation, Sammon, RPM, mRPM, CCA, PCA, LLE, LE, HLLE, LTSA, SMACOF and Isomap. Some of them are used to analyze head images acquired by webcam.. Application is created which is then used to analyze head orientation by implementing Isomap method.
7

Integration and miniaturization of antennas for system-on-package applications

Altunyurt, Nevin 05 April 2010 (has links)
Wireless communications have been an indispensable aspect of everyday life, and there is an increasing consumer demand for accessing several wireless communication technologies from a single, compact, mobile device. System-on-package (SOP) technology is an advanced packaging technology that has been proven to realize the convergence of multiple functions into miniaturized, high-performance systems to meet this demand. With the advancements in the SOP technology, the miniaturization of the front-end module has been achieved using embedded passives in multilayer packages. However, the integration of the antenna directly on the module package is still the barrier to achieve a fully-integrated, high-performance RF SOP system. The main reason for this missing link is that integrating the antenna on the package requires miniaturizing the antenna, which is a difficult task. The focus of this dissertation is to design high-performance antennas along with developing techniques for miniaturization and system-on-package (SOP) integration of these antennas to achieve fully-integrated SOP systems using advanced multilayer organic substrates and thin-film magneto-dielectric materials. The targeted spectrum for the antenna designs are 2.4/5 GHz WLAN/WiMAX and 60 GHz WPAN bands. Several novel antenna designs and configurations to integrate the antenna on the package along with the module are discussed in this dissertation. The advanced polymers used in this research are Liquid Crystalline Polymer (LCP), RXP, and thin-film magneto-dielectrics.

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