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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.
71

Constructions Of Bent Functions

Sulak, Fatih 01 January 2006 (has links) (PDF)
In cryptography especially in block cipher design, Boolean functions are the basic elements. A cryptographic function should have high nonlinearity as it can be attacked by linear attack. In this thesis the highest possible nonlinear boolean functions in the even dimension, that is bent functions, basic properties and construction methods of bent functions are studied. Also normal bent functions and generalized bent functions are presented.
72

Algunos resultados sobre B-matrices y matrices con inversa positiva

Abad Rodríguez, Manuel Francisco 26 July 2012 (has links)
El objetivo de esta memoria es analizar, desde diferentes puntos de vista, dos clases de matrices ampliamente utilizadas, las matrices con inversa positiva y las B-matrices. Vamos a generalizar, en unos casos, y completar en otros los resultados obtenidos por diferentes investigadores. El problema de caracterizar matrices inversa-positiva ha sido extensamente tratado en la literatura. Diversos autores estudiaron el concepto para matrices inversa-positiva que además fuesen Z-matriz (es decir, M-matrices). Otros autores se ocuparon de caracterizar los patrones de signos que debe seguir una matriz inversa-positiva. La inversa-positividad de matrices cuadradas reales juega un rol muy importante en diferentes áreas de la ciencia y la ingeniería y ha sido analizada en diferentes contextos. En nuestro trabajo presentamos nuevas caracterizaciones de matrices inversa-positiva. Analizamos también el concepto inversa-positiva para un tipo particular de patrón de signos: el patrón 'checkerboard'. La suma sub-directa de matrices es una generalización de la suma habitual de matrices. Fue introducida por C. Johnson y S. Fallat y aparece de un modo natural en completación de matrices y subdominios solapados en métodos de descomposición de dominios, entre otros contextos. También aparece en diversas variantes de precondicionamiento aditivo de Schwartz, y cuando se analizan métodos aditivos de Schwartz para cadenas de Markov. En este trabajo aportamos nuevos resultados acerca de la suma sub-directa de matrices con inversa positiva y de la suma sub-directa de las distintas clases de B-matrices, planteándonos las preguntas de Fallat y Johnson y respondiéndolas para las clases de matrices mencionadas. Johnson, estudió los posibles patrones de signos de una matriz compatibles con el hecho de que tenga su inversa positiva. Siguiendo sus resultados, analizamos el concepto inversa-positiva para un tipo particular de patrón: el patrón 'checkerboard'. Estudiamos también en esta memoria la / Abad Rodríguez, MF. (2012). Algunos resultados sobre B-matrices y matrices con inversa positiva [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16883 / Palancia
73

Modulátor s rozprostřeným spektrem / Spread spectrum modulator

Lejsková, Alena January 2011 (has links)
This thesis deals with a method of spectrum-spreading of the data signals transmitted in the radio channel. There exist three different ways of spreading application, they uses pseudorandom sequences and also orthogonal sequences. In these systems we can find various kinds of modulations, one of them (Quadrature Phase Shift Keying) is shown at the end of the thesis. Spectrum spreading orthogonal multiplex OFDM is based on this method. The thesis wants to present the principle of the spectrum spreading method and the description of systems, transmitters and receivers that are using this method.
74

Aspects of Gauge Theories in Lorentzian Curved Space-times

Taslimitehrani, Mojtaba 12 December 2018 (has links)
We study different aspects of perturbatively renormalized quantum gauge theories in the presence of non-trivial background Lorentzian metrics and background connections. First, we show that the proof of nilpotency of the renormalized interacting BRST charge can be reduced to the cohomological analysis of the classical BRST differential. This result guarantees the self-consistency of a class of local, renormalizable field theories with vanishing 'gauge anomaly'' at the quantum level, such as the pure Yang-Mills theory in four dimensions. Self-consistency here means that the algebra of gauge invariant observables can be constructed as the cohomology of this charge. Second, we give a proof of background independence of the Yang-Mills theory. We define background independent observables in a geometrical formulation as flat sections of a cohomology algebra bundle over the manifold of background configurations, with respect to a flat connection which implements background variations. We observe that background independence at the quantum level is potentially violated. We, however, show that the potential obstructions can be removed by a finite renormalization. Third, we construct the advanced/retarded Green's functions and Hadamard parametrices for linearized Yang-Mills and Einstein equations in general linear covariant gauges. They play an essential role in formulating gauge theories in curved spacetimes. Finally, we study a superconformal gauge theory in three dimensions (the ABJM theory) which is conformally coupled to a curved background. The superconformal symmetry of this theory is described by a conformal symmetry superalgebra on manifolds which admit twistor spinors. By analyzing the relevant cohomology class of an appropriate BV-BRST differential, we show that the full superalgebra is realized at the quantum level.
75

An in-depth examination of two-dimensional Laplace inversion and application to three-dimensional holography

Feng, Le 26 August 2014 (has links)
No description available.
76

A new approach for implementing QO-STBC over OFDM

Dama, Yousef A.S., Migdadi, Hassan S.O., Shuaieb, Wafa S.A., Elkhazmi, Elmahdi A., Abdulmula, E.A., Abd-Alhameed, Raed, Hammoudeh, W., Masri, A. January 2015 (has links)
No / A new approach for implementing QO-STBC and DHSTBC over OFDM for four, eight and sixteen transmitter antennas is presented, which eliminates interference from the detection matrix and improves performance by increasing the diversity order on the transmitter side. The proposed code promotes diversity gain in comparison with the STBC scheme, and also reduces Inter Symbol Interference.
77

RFI Mitigation and Discrete Digital Signal Processing RFSoC Algorithm Implementations for Radio Astronomy and Wideband Communication Systems

Ward, Devon Christopher 28 March 2024 (has links) (PDF)
Due to the massive increase of active transmitters broadcasting over wideband frequencies, such as 5G wireless systems, LEO/MEO satellites, satellite constellations, and the increase of IoT devices in the average home, the radio frequency spectrum is becoming more and more congested by interference. Passive receivers face additional challenges due to the growing use of wideband frequency transmissions aimed at boosting communication system throughput. As a result, passive receivers must adopt more robust and intricate techniques to mitigate radio frequency interference. A proposed RFI removal system, known as the true time delay Hadamard projection algorithm, has been introduced in previous work to eliminate a single RFI source while preserving a narrowband signal of interest. An RF frontend is developed to assess the effectiveness of the Hadamard projection algorithm implemented on an RFSoC ZCU216. Additionally, the TTD Hadamard projection algorithm is expanded to enable the cancellation of multiple RFI sources rather than just a single source for a uniform linear array and a uniform rectangular array. Over-the-air tests are conducted to verify the performance of the interference cancellation algorithms and demonstrate the algorithms' ability to preserve the signals of interest while removing the wideband interference. Multiple algorithms are proposed to estimate the time delays used by the interference cancellation algorithm to effectively eliminate wideband interference. These algorithms address diverse scenarios encompassing interference sources ranging from strong to weak SNR. Detailed reports of algorithm performance provide insights into their effectiveness and suitability across specific interference conditions.
78

Incorporation of Causal Factors Affecting Pilot Motivation for Improvement of Airport Runway and Exit Design Modeling

Olamai, Afshin 18 October 2022 (has links)
This research aims to improve the design and placement of runway exits at airports through analysis and modeling of the effects that exogenous causal factors have on pilots' landing behavior and exit selections. Incorporating these factors into modeling software will strengthen the software's utility by providing project teams the ability to specify which pilot motivational causal factors apply to a new or existing runway. The main findings suggest pilots' exit selections are deterministic but dependent on the presence (or absence) of six (6) causal factors. A model and two (2) case studies are presented and compared against predictions generated by existing modeling software. The results support a finding that the causal factor model improves motivation-based predictions over current modeling techniques, which are drawn from stochastic distributions. The accuracy of this model enables designers to optimize runway exit placement and geometry to maximize runway capacity. / Master of Science / Airport design engineers currently plan the locations and geometric characteristics of runway exits by balancing the expected fleet mix of aircraft on that runway with the capacity and delay effects that the number and placement of these exits might cause. This technique originated from research beginning in the early 1970s, which found that pilots' exit motivations primarily resulted from the capabilities and limitations of their aircraft. Since pilots tend to "fly by the numbers" (i.e., exhibit predictable approach airspeeds, power levels, wing flaps, touchdown locations, landing speeds, and braking efforts), engineers thus employed design principles in which the numbers, locations and geometries of exits were primarily functions of the physical and performance-based characteristics of the specific types of aircraft expected to utilize the runway. However, in studying more than 4 million landings by a single aircraft type (the Boeing 737-800) at 42 U.S. airports, the evidence in this thesis shows that pilots' exit selections are behaviorally motivated by more than the physics of motion. This thesis aims to refine previous research and engineering methods by showing evidence that pilots' exit selections have as much to do with the presence (or absence) of certain environmental factors within the landing system. These factors (described in detailed within) are unique to each airport's overall physical network of interconnected runways, exits, taxiways, terminals and other features. Within this network, a pilot's landing behavior and exit selection depends on the locational and relational interactions that each exit choice will have on the time and distance to their apron (gate) assignment. These "interactions" are referred to as causal factors – defined as physical features within a landing environment that pilots have little-to-no control over – but which nevertheless influence their specific exit selections. Two (2) runway case studies provided in this thesis evidence a finding that a causal factor model reliably predicts pilots' exit selections better than current modeling techniques, which are drawn from probability-based statistical distributions. The stability and accuracy of the new model enables engineering design and project teams to optimize runway exit placement and geometry to maximize runway capacity, and can be adopted for use in both existing and future runways.
79

兩個組合數學的主題: Hadamard 矩陣的建構及有關森林的研究 / Two Combinatorial Topics: Constructions of Hadamard Matrices and Studies of Forests

施耀振, Shih,Yaio-Zhern Unknown Date (has links)
在這篇論文,我們主要探討兩個獨立的組合數學主題:一個是Hadamard矩陣的建構,一個是有關森林的研究。在第一個主題,所得者又分為二,其一,我們從一個已知的Hadamard矩陣,利用Sylvester的方法去建構名為Jm-Hadamard矩陣。從這個矩陣裡,藉由在Sm上適當的排列,可以獲致其他2mm!-1個Hadamard矩陣。另外,我們引進Jm-class的概念, 將之寫成CJm,並探討當n整除n'時,CJn'是否包含於CJn。關於這個問題,我們得到最初的結論是CJ8 CJ4 CJ2。其二,在已知的t個階數分別是4m1,4m2,…,4mt的Hadamard矩陣,希望獲得一個階數是2km1m2… mt的Hadamard矩陣,使得k值愈小愈好。我們可以找到最小指數的上界,這個數稍好於Craigen及de Launey所得到的值。在第二個主題裡,我們致力於三個目標,首先,我們將平面樹上的一些結果,推廣到平面森林上,諸如Shapiro的結果,葉子的偶數、奇數問題,Catalan數與類似數之間的恒等式。其二,我們用了一個很簡潔的方法去證明Chung-Feller定理,也獲致相關的結果及應用。最後,我們以研究數種n-caterpillars的優美標法,作為本文的結束,最特別的是我們可藉用拉丁方陣去建構2n-caterpillars的優美標法。
80

Generalized vector equilibrium problems and algorithms for variational inequality in hadamard manifolds / Problemas de equilíbrio vetoriais generalizados e algoritmos para desigualdades variacionais em variedades de hadamard

Batista, Edvaldo Elias de Almeida 20 October 2016 (has links)
Submitted by Jaqueline Silva (jtas29@gmail.com) on 2016-12-09T17:10:49Z No. of bitstreams: 2 Tese - Edvaldo Elias de Almeida Batista - 2016.pdf: 1198471 bytes, checksum: 88d7db305f0cfe6be9b62496a226217f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2016-12-09T17:11:03Z (GMT) No. of bitstreams: 2 Tese - Edvaldo Elias de Almeida Batista - 2016.pdf: 1198471 bytes, checksum: 88d7db305f0cfe6be9b62496a226217f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-12-09T17:11:03Z (GMT). No. of bitstreams: 2 Tese - Edvaldo Elias de Almeida Batista - 2016.pdf: 1198471 bytes, checksum: 88d7db305f0cfe6be9b62496a226217f (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-10-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this thesis, we study variational inequalities and generalized vector equilibrium problems. In Chapter 1, several results and basic definitions of Riemannian geometry are listed; we present the concept of the monotone vector field in Hadamard manifolds and many of their properties, besides, we introduce the concept of enlargement of a monotone vector field, and we display its properties in a Riemannian context. In Chapter 2, an inexact proximal point method for variational inequalities in Hadamard manifolds is introduced, and its convergence properties are studied; see [7]. To present our method, we generalize the concept of enlargement of monotone operators, from a linear setting to the Riemannian context. As an application, an inexact proximal point method for constrained optimization problems is obtained. In Chapter 3, we present an extragradient algorithm for variational inequality associated with the point-to-set vector field in Hadamard manifolds and study its convergence properties; see [8]. In order to present our method, the concept of enlargement of maximal monotone vector fields is used and its lower-semicontinuity is established to obtain the convergence of the method in this new context. In Chapter 4, we present a sufficient condition for the existence of a solution to the generalized vector equilibrium problem on Hadamard manifolds using a version of the KnasterKuratowski-Mazurkiewicz Lemma; see [6]. In particular, the existence of solutions to optimization, vector optimization, Nash equilibria, complementarity, and variational inequality is a special case of the existence result for the generalized vector equilibrium problem. / Nesta tese, estudamos desigualdades variacionais e o problema de equilíbrio vetorial generalizado. No Capítulo 1, vários resultados e definições elementares sobre geometria Riemanniana são enunciados; apresentamos o conceito de campo vetorial monótono e muitas de suas propriedades, além de introduzir o conceito de alargamento de um campo vetorial monótono e exibir suas propriedades em um contexto Riemanniano. No Capítulo 2, um método de ponto proximal inexato para desigualdades variacionais em variedades de Hadamard é introduzido e suas propriedades de convergência são estudadas; veja [7]. Para apresentar o nosso método, generalizamos o conceito de alargamento de operadores monótonos, do contexto linear ao contexto de Riemanniano. Como aplicação, é obtido um método de ponto proximal inexato para problemas de otimização com restrições. No Capítulo 3, apresentamos um algoritmo extragradiente para desigualdades variacionais associado a um campo vetorial ponto-conjunto em variedades de Hadamard e estudamos suas propriedades de convergência; veja [8]. A fim de apresentar nosso método, o conceito de alargamento de campos vetoriais monótonos é utilizado e sua semicontinuidade inferior é estabelecida, a fim de obter a convergência do método neste novo contexto. No Capítulo 4, apresentamos uma condição suficiente para a existência de soluções para o problema de equilíbrio vetorial generalizado em variedades de Hadamard usando uma versão do Lema Knaster-Kuratowski-Mazurkiewicz; veja [6]. Em particular, a existência de soluções para problemas de otimização, otimização vetorial, equilíbrio de Nash, complementaridade e desigualdades variacionais são casos especiais do resultado de existência do problema de equilíbrio vetorial generalizado.

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