Dissertationen zum Thema „Codes minimaux“
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Qian, Liqin. „Contributions to the theory of algebraic coding on finite fields and rings and their applications“. Electronic Thesis or Diss., Paris 8, 2022. http://www.theses.fr/2022PA080064.
Der volle Inhalt der QuelleAlgebraic coding theory over finite fields and rings has always been an important research topic in information theory thanks to their various applications in secret sharing schemes, strongly regular graphs, authentication and communication codes.This thesis addresses several research topics according to the orientations in this context, whose construction methods are at the heart of our concerns. Specifically, we are interested in the constructions of optimal codebooks (or asymptotically optimal codebooks), the constructions of linear codes with a one-dimensional hull, the constructions of minimal codes, and the constructions of projective linear codes. The main contributions are summarized as follows. This thesis gives an explicit description of additive and multiplicative characters on finite rings (precisely _\mathbb{F}_q+u\mathbb{F}_q~(u^2= 0)s and S\mathbb{F}_q+u\mathbb{F}_q~(u^2=u)S), employees Gaussian, hyper Eisenstein and Jacobi sums and proposes several classes of optimal (or asymptotically optimal) new codebooks with flexible parameters. Next, it proposes(optimal or nearly optimal) linear codes with a one-dimensional hull over finite fields by employing tools from the theory of Gaussian sums. It develops an original method to construct these codes. It presents sufficient conditions for one-dimensional hull codes and a lower bound on its minimum distance. Besides, this thesis explores several classes of (optimal for the well-known Griesmer bound) binary linear codes over finite fields based on two generic constructions using functions. It determines their parameters and weight distributions and derives several infinite families of minimal linear codes. Finally, it studies (optimal for the sphere packing bound) constructions of several classes of projective binary linear codes with a few weight and their corresponding duals codes
Luu, Tien Duc. „Régularité des cônes et d’ensembles minimaux de dimension 3 dans R4“. Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112301/document.
Der volle Inhalt der QuelleIn this thesis we study the problems of regularity of three-dimensional minimal cones and sets in l'espace Euclidien de dimension 4In the first part we study the Hölder regularity for minimal cones of dimension 3 in l'espace Euclidien de dimension 4. Then we use this for showing that there exists a local diffeomorphic mapping between a minimal cone of dimension 3 and a minimal cone of dimension 3 of type P, Y or T, away from the origin. The techniques used here are the same as the ones for the regularity of two-dimensional minimal sets. We construct some competitors to reduce to the known situation of two-dimensional minimal sets in l'espace Euclidien de dimension 3.In the second part, we use the first part to give somme results of the Hölder regularity for three-dimensional minimal sets in l'espace Euclidien de dimension 4. We interested also in Mumford-Shah minimal sets and we get a result of the existence of a T-point
Miller, John. „High code rate, low-density parity-check codes with guaranteed minimum distance and stopping weight /“. Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3090443.
Der volle Inhalt der QuelleFang, Yangqin. „Minimal sets, existence and regularity“. Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112191/document.
Der volle Inhalt der QuelleThis thesis focuses on the existence and regularity of minimal sets. First we show, in Chapter 3, that there exists (at least) a minimizerfor Reifenberg Plateau problems. That is, Given a compact set B⊂R^n, and a subgroup L of the Čech homology group H_(d-1) (B;G) of dimension (d-1)over an abelian group G, we will show that there exists a compact set E⊃B such that L is contained in the kernel of the homomorphism H_(d-1) (B;G)→H_(d-1) (E;G) induced by the natural inclusion map B→E, and such that the Hausdorff measure H^d (E∖B) is minimal under these constraints. Next we will show, in Chapter 4, that if E is a sliding almost minimal set of dimension 2, in a smooth domain Σ that looks locally like a half space, and with sliding boundary , and if in addition E⊃∂Σ, then, near every point of the boundary ∂Σ, E is locally biHölder equivalent to a sliding minimal cone (in a half space Ω, and with sliding boundary ∂Ω). In addition the only possible sliding minimal cones in this case are ∂Ω or the union of ∂Ω with a cone of type P_+ or Y_+
Ketkar, Avanti Ulhas. „Code constructions and code families for nonbinary quantum stabilizer code“. Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/2743.
Der volle Inhalt der QuelleZeng, Fanxuan. „Nonlinear codes: representation, constructions, minimum distance computation and decoding“. Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/284241.
Der volle Inhalt der QuelleCadic, Emmanuel. „Construction de Turbo Codes courts possédant de bonnes propriétés de distance minimale“. Limoges, 2003. http://aurore.unilim.fr/theses/nxfile/default/2c131fa5-a15a-4726-8d49-663621bd2daf/blobholder:0/2003LIMO0018.pdf.
Der volle Inhalt der QuelleThis thesis is aimed at building turbo codes with good minimum distances and delaying the``error-floor'' which corespond to a threshold of 10-6 for the binary error rate. Under this threshold, the slope of the curve decreases significantly. This problem is alleviated by the use of duo-binary turbo codes [11] which guarantee better minimum distances. In order to obtain good minimum distances with short turbo codes (length inferior to 512), the first construction used and studied is the one proposed by Carlach and Vervoux [26]. It allows to obtain very good minimum distances but its decoding is unfortunately very difficult because of its structure. After identifying the reasons for this problem, we have modified these codes by using some graphicals structures which are the gathering of low complexity components codes. The idea is to realize this change without loosing the minimum distances properties, and consequently we had to understand why minimum distances are good for this familly of codes and define a new criteria to choose ``good'' components codes. This criteria is independent from the minimum distance of the component codes because it is derived from the Input-Output Weight Enumerator (IOWE) of the components codes. It allows us to choose components codes with very low complexity which are combined in order to provide 4-state tail-biting trellises. These trellises are then used to build multiple parallel concatenated and serial turbo codes with good minimum distances. Some extremal self-dual codes have been built in that way
Siap, Irfan. „Generalized [Gamma]-fold weight enumerators for linear codes and new linear codes with improved minimum distances /“. The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488193272067477.
Der volle Inhalt der QuelleKumar, Santosh. „Upper bounds on minimum distance of nonbinary quantum stabilizer codes“. Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/2744.
Der volle Inhalt der QuelleChan, Evelyn Yu-San. „Heuristic optimisation for the minimum distance problem“. Thesis, Nottingham Trent University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324569.
Der volle Inhalt der QuelleAhmed, Naveed, und Waqas Ahmed. „Classification of perfect codes and minimal distances in the Lee metric“. Thesis, Linnaeus University, School of Computer Science, Physics and Mathematics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-6574.
Der volle Inhalt der QuellePerfect codes and minimal distance of a code have great importance in the study of theoryof codes. The perfect codes are classified generally and in particular for the Lee metric.However, there are very few perfect codes in the Lee metric. The Lee metric hasnice properties because of its definition over the ring of integers residue modulo q. It isconjectured that there are no perfect codes in this metric for q > 3, where q is a primenumber.The minimal distance comes into play when it comes to detection and correction oferror patterns in a code. A few bounds on the number of codewords and minimal distanceof a code are discussed. Some examples for the codes are constructed and their minimaldistance is calculated. The bounds are illustrated with the help of the results obtained.
Cavallotto, Edoardo. „Résultats de régularité et d'existence pour des ensembles minimaux ; Problème de Plateau“. Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS180/document.
Der volle Inhalt der QuelleSolving the Plateau problem means to find the surface with minimal area among all surfaces with a given boundary. Part of the problem actually consists of giving a suitable definition to the notions of “surface”, “area” and “boundary”. In our setting the considered objects are sets whose Hausdorff area is locally finite. The sliding boundary condition is given in term of a one parameter family of compact deformations which allows the boundary of the surface to moove along a closed set. The area functional is related to capillarity and free-boundary problems, and is a slight modification of the Hausdorff area.We focused on minimal boundary cones ; that is to say tangent cones on boundary points of sliding minimal surfaces. In particular we studied cones contained in an half-space and whose boundary can slide along the bounding hyperplane. After giving a classification of one-dimensional minimal cones in the half-plane we provided four new two-dimensional minimal cones in the three-dimensional half space (which cannot be obtained as the Cartesian product of the real line with one of the previous cones). We employed the technique of paired calibrations and in one case could also generalise it to higher dimension.In order to prove that the provided list of minimal cones is complete, we started the classification of cones satisfying the necessary conditions for the minimality, and with numeric simulations we obtained better competitors for these new candidates
Wunderlich, Marcel [Verfasser], und Boris [Akademischer Betreuer] Vertman. „Mean curvature flow of cones near minimal cones / Marcel Wunderlich ; Betreuer: Boris Vertman“. Münster : Universitäts- und Landesbibliothek Münster, 2019. http://d-nb.info/1190175517/34.
Der volle Inhalt der QuellePapadimitriou, Panayiotis D. „Code design based on metric-spectrum and applications“. Texas A&M University, 2004. http://hdl.handle.net/1969.1/1365.
Der volle Inhalt der QuelleBazzi, Louay Mohamad Jamil 1974. „Minimum distance of error correcting codes versus encoding complexity, symmetry, and pseudorandomness“. Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17042.
Der volle Inhalt der QuelleIncludes bibliographical references (leaves 207-214).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
We study the minimum distance of binary error correcting codes from the following perspectives: * The problem of deriving bounds on the minimum distance of a code given constraints on the computational complexity of its encoder. * The minimum distance of linear codes that are symmetric in the sense of being invariant under the action of a group on the bits of the codewords. * The derandomization capabilities of probability measures on the Hamming cube based on binary linear codes with good distance properties, and their variations. Highlights of our results include: * A general theorem that asserts that if the encoder uses linear time and sub-linear memory in the general binary branching program model, then the minimum distance of the code cannot grow linearly with the block length when the rate is nonvanishing. * New upper bounds on the minimum distance of various types of Turbo-like codes. * The first ensemble of asymptotically good Turbo like codes. We prove that depth-three serially concatenated Turbo codes can be asymptotically good. * The first ensemble of asymptotically good codes that are ideals in the group algebra of a group. We argue that, for infinitely many block lengths, a random ideal in the group algebra of the dihedral group is an asymptotically good rate half code with a high probability. * An explicit rate-half code whose codewords are in one-to-one correspondence with special hyperelliptic curves over a finite field of prime order where the number of zeros of a codeword corresponds to the number of rational points.
(cont.) * A sharp O(k-1/2) upper bound on the probability that a random binary string generated according to a k-wise independent probability measure has any given weight. * An assertion saying that any sufficiently log-wise independent probability measure looks random to all polynomially small read-once DNF formulas. * An elaborate study of the problem of derandomizability of AC₀ by any sufficiently polylog-wise independent probability measure. * An elaborate study of the problem of approximability of high-degree parity functions on binary linear codes by low-degree polynomials with coefficients in fields of odd characteristics.
by Louay M.J. Bazzi.
Ph.D.
Fingeret, Samuel (Samuel P. ). „Defeating code reuse attacks with minimal tagged architecture“. Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/105986.
Der volle Inhalt der QuelleThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 93-97).
In this thesis, we argue that software-based defenses to code reuse attacks are fundamentally flawed. With code pointer integrity as a case study, we show that a secure and efficient software-based defense to code reuse attacks is impossible and thus motivate the case for hardware approaches. We then propose our tagged architecture system Taxi (Tagged C) as a practical defense against code reuse attacks which minimally modifies existing hardware components. We also propose strong defense policies which aim to guarantee security while minimizing tag memory usage. Our Taxi prototype, a modified RISC-V ISA simulator, demonstrates that we can defeat code reuse attacks with high compatibility and low memory overhead.
by Samuel Fingeret.
M. Eng.
Nikolaidis, Christos. „On binary linear codes with 2-transitive automorphism group and minimum weight four“. Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318832.
Der volle Inhalt der QuelleMartin, Timothy Michael. „Codes of Interaction“. VCU Scholars Compass, 2005. http://scholarscompass.vcu.edu/etd/849.
Der volle Inhalt der QuelleAppleby, Paul [Verfasser]. „Mean curvature flow of surfaces asymptotic to minimal cones / Paul Appleby“. Berlin : Freie Universität Berlin, 2011. http://d-nb.info/1025510003/34.
Der volle Inhalt der QuelleGaland, Fabien. „Construction de codes Z indice p à la puissance k linéaires de bonne distance minimale et schémas de dissimulation fondés sur les codes de recouvrement“. Caen, 2004. http://www.theses.fr/2004CAEN2047.
Der volle Inhalt der QuelleMahmudi, Ali. „The investigation into generic VHDL implementation of generalised minimum distance decoding for Reed Solomon codes“. Thesis, University of Huddersfield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417302.
Der volle Inhalt der QuelleAssuena, Samir. „Códigos metacíclicos“. Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/45/45131/tde-30102013-065155/.
Der volle Inhalt der QuelleWe consider semisimple group algebras F_G of non abelian split metacyclic groups over a finite field. First we give necessary and suficiente conditions for them to have a minimal number of simple components and find the primitive central idempotents of F_G in the case when the order G is equals p^l^, where p and l are different prime numbers. Then, we consider the special case when the order of G is 2n. Finally, when G=D_{p^} the dihedral group of order 2p^, we obtain two decomposition of the algebra into direct sum of minimal left ideals, compute their dimensions and weights. We show that one of these decompositions gives raise to minimal codes that are not combinatorially equivalent to abelian codes giving an affirmative answer to a conjecture formulated by Sabin and Lomonaco in 1995.
Corazza, Federico Augusto. „Analysis of graph-based quantum error-correcting codes“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23801/.
Der volle Inhalt der QuelleFang, Juing. „Décodage pondère des codes en blocs et quelques sujets sur la complexité du décodage“. Paris, ENST, 1987. http://www.theses.fr/1987ENST0005.
Der volle Inhalt der QuelleAssis, Ailton Ribeiro de. „Idempotentes em Álgebras de Grupos e Códigos Abelianos Minimais“. Universidade Federal da Paraíba, 2011. http://tede.biblioteca.ufpb.br:8080/handle/tede/7401.
Der volle Inhalt der QuelleCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
In this work, we study the semisimple group algebras FqCn of the finite abelian groups Cn over a finite field Fq and give conditions so that the number of its simple components is minimal; i.e. equal to the number of simple components of the rational group algebra of the same group. Under such conditions, we compute the set of primitive idempotents of FqCn and from there, we study the abelian codes as minimal ideals of the group algebra, which are generated by the primitive idempotents, computing their dimension and minimum distances.
Neste trabalho, estudamos álgebras de grupos semisimples FqCn de grupos abelianos finitos Cn sobre um corpo finito Fq e as condições para que o número de componentes simples seja mínimo, ou seja igual ao número de componentes simples sobre a álgebra de grupos racionais do mesmo grupo. Sob tais condições, calculamos o conjunto de idempotentes primitivos de FqG e a de partir daí, estudamos os códigos cíclicos como ideais minimais da álgebra de grupo, os quais são gerados pelos idempotentes primitivos, calculando suas dimensões e distâncias mínimas.
Augot, Daniel. „Étude algèbrique des mots de poids minimum des codes cycliques, méthodes d'algèbre linéaire sur les corps finis“. Phd thesis, Université Pierre et Marie Curie - Paris VI, 1993. http://tel.archives-ouvertes.fr/tel-00723227.
Der volle Inhalt der QuelleAugot, Daniel. „Etude algebrique des mots de poids minimum des codes cycliques, methodes d'algebre lineaire sur les corps finis“. Paris 6, 1993. https://tel.archives-ouvertes.fr/tel-00723227.
Der volle Inhalt der QuelleAl-Fahad, Jasem Y. „Reform of building codes, regulations, administration and enforcement in Kuwait : within the legal, administrative, technical & social framework“. Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/9883.
Der volle Inhalt der QuelleAbdallah, Saeed. „Widely linear minimum variance channel estimation with application to multicarrier CDMA systems“. Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112550.
Der volle Inhalt der QuelleZeh, Alexander. „Algebraic Soft- and Hard-Decision Decoding of Generalized Reed--Solomon and Cyclic Codes“. Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00866134.
Der volle Inhalt der QuelleDang, Xiaoyu. „An Optimum Detector for Space-Time Trellis Coded Differential MSK“. International Foundation for Telemetering, 2007. http://hdl.handle.net/10150/604515.
Der volle Inhalt der QuelleThe accuracy of channel estimation plays a crucial role in the demodulation of data symbols sent across an unknown wireless medium. In this work a new analytical expression for the channel estimation error of a multiple input multiple output (MIMO) system is obtained when the wireless medium is continuously changing in the temporal domain. Numerical examples are provided to illustrate our findings. Space-time (ST) coding using Continuous Phase Modulation (CPM) has spectral advantages relative to linear modulations. In spite of the spectral benefits, Space-Time Trellis Codes (STTC) using the CPM implementation of Minimum Shift Keying (MSK) scheme has inherent inphase and quadrature interference, when the received complex baseband signal is the input into the matchfilter to remove the shaped sinusoid pulses. In this paper a novel optimum transmitting and detecting structure for STTC-MSK is proposed. Treating the Alamouti scheme as an outer code, each STTC MSK waveform frame is immediately followed by the orthogonal conjugate waveform frame at the transmit side. At the receiver first orthogonal wave forming is applied, then a new time-variant yet simple trellis structure of the STTC-MSK signals is developed. This STTC-MSK detector is absolutely guaranteed to be I/Q interference-free and still keeps a smaller computation load compared with STTC-QPSK. Simulations are made over quasi-static AWGN fading channel. It is shown that our detector for ST-MSK has solved the I/Q interference problem and has around 2.8 dB gain compared with the Alamouti Scheme and 3.8 dB gain for bit error rate at 5 X 10^(-3) in a 2 by 1 Multiple Input Single Output system.
Triantafillou, Thanasis C. (Thanasis Christos). „Failure mode maps and minimum weight design for structural sandwich beams with rigid foam cores“. Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14944.
Der volle Inhalt der QuelleMICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 69-71.
by Thanasis C. Triantafillou.
M.S.
Merlino, Enzo Maria. „Fractional Perimeter and Nonlocal Minimal Surfaces“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Den vollen Inhalt der Quelle findenGarcia, Vitor Araujo. „Idempotentes centrais primitivos em algumas álgebras de grupos“. Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/45/45131/tde-05102015-225032/.
Der volle Inhalt der QuelleOur goal in this project is to present some results about group rings and its applications, as presented in books and articles about this subject. First of all we are going to establish some basic fact about group rings, which can be found mainly in [5], and then we will present the main results, which are more recent, and have been studied in two different articles. In [4], the authors presented a way of evaluating the number of simple components of some finite group algebras, as well presented a way of evaluating idempotent generators of some minimal abelian codes, their dimension and their weights. In [2] there is a complete description of all the primitive central idempotents of the rational group algebra of finite nilpotent groups.
Su, Yong. „Mathematical modeling with applications in high-performance coding“. Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127139848.
Der volle Inhalt der QuelleTitle from first page of PDF file. Document formatted into pages; contains xiv, 130 p.; also includes graphics (some col.). Includes bibliographical references (p. 125-130). Available online via OhioLINK's ETD Center
Garcia-Alis, Daniel. „On adaptive MMSE receiver strategies for TD-CDMA“. Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366896.
Der volle Inhalt der QuelleSepúlveda, Castellanos Alonso. „Sobre codigos hermitianos generalizados“. [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/307073.
Der volle Inhalt der QuelleTese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica
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Resumo: Estudamos os códigos de Goppa (códigos GH) sobre certos corpos de funções algébricas com muitos lugares racionais. Estes códigos generalizam os bem conhecidos códigos Hermitianos; portanto podemos esperar que estes códigos tenham bons parâmetros. Bulygin (IEEE Trans. Inform. Theory 52 (10), 4664¿4669 (2006)) inicia o estudo dos códigos GH; enquanto Bulygin considerou somente característica par, nosso trabalho 'e feito em qualquer característica. Em qualquer caso, nosso trabalho é fortemente influenciado pelo de Bulygin. A seguir, listamos alguns dos nossos resultados com respeito aos códigos GH. ¿ Calculamos ¿distâncias mínimas exatas¿, em particular, melhoramos os resultados de Bulygin; ¿ Encontramos cotas para os pesos generalizados de Hamming, al'em disso, mostramos um algoritmo para aplicar estes cálculos na criptografia; ¿ Calculamos um subgrupo de Automorfismos; ¿ Consideramos códigos em determinados subcorpos dos corpos usados para construir os códigos GH
Abstract: We study Goppa codes (GH codes) based on certain algebraic function fields whose number of rational places is large. These codes generalize the well-known Hermitian codes; thus we might expect that they have good parameters. Bulygin (IEEE Trans. Inform. Theory 52 (10), 4664¿4669 (2006)) initiate the study of GH-codes; while he considered only the even characteristic, our work is done regardless the characteristic. In any case our work was strongly influenced by Bulygin¿s. Next we list some of the results of our work with respect to GH-codes. ¿ We calculate ¿true minimum distances¿, in particular, we improve Bulygin¿s results; ¿ We find bounds on the generalized Hamming weights, moreover, we show an algorithm to apply these computations to the cryptography; ¿ We calculate an Automorphism subgroup; ¿ We consider codes on certain subfields of the fields used for to construct GH-codes
Doutorado
Algebra (Geometria Algebrica)
Doutor em Matemática
Karaer, Arzu. „Optimum bit-by-bit power allocation for minimum distortion transmission“. Texas A&M University, 2005. http://hdl.handle.net/1969.1/4760.
Der volle Inhalt der QuelleMoro, Eliton Mendonça [UNESP]. „Códigos de bloco espaço-temporais via corpos quadráticos“. Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/148757.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Os sistemas de comunicação com Múltiplas Entradas e Múltiplas Saídas (MIMO), são sistemas constituídos por estruturas que utilizam várias antenas, tanto no transmissor como no receptor. Por serem transmitidos via antenas, naturalmente surgem problemas de ruídos e de multipercursos, que impõe um desafio para o desenvolvimento dos sistemas de comunicação MIMO. Por esses motivos, muitos estudos focam em certas propriedades dos sinais enviados a fim de minimizar os efeitos sofridos na informação durante a transmissão. Existem muitos tipos diferentes de Códigos de Bloco Espaço-Temporais (STBC) disponíveis para duas antenas transmissoras, dentre eles, o código de bloco espaço-temporal ciclotômico, Código de Ouro e Código de Prata. Neste trabalho apresentamos uma construção de STBC cujos os sinais utilizados na transmissão são identificados por elementos de anéis de inteiros de corpos de números totalmente imaginários, Q(√d), com d<0, e apresentamos os melhores STBC em termos do critério que denominamos como critério produto, considerando extensões de Q(√d) com d=-1,-2,-3,-7, -11.
The communication systems of Multiple Input and Multiple Output (MIMO), are systems consisting of structures that use multiple antennas, both on the transmitter and the receiver. For being transmitted via antennas, noise and path problems naturally arise, which poses a challenge for the development and optimization of MIMO systems. For these reasons, many studies focus on certain properties of the signals sent in order to minimize the effects suffered on the information during transmission. There are many different types of Space-Time Block Codes (STBC) available for two transmitting antennas, such as the cyclotomic space-time block code, Golden code, and Silver code. In this work, we present a STBC construct via totally imaginary quadratic fields, Q(√d) with d <0 and present the best STBC in terms of the criterion that we call product criteria, considering extensions of Q(√d) with d = -1, - 2, - 3, - 7, -11.
Ghayour, Mehdi. „Enhancements to the sample-matrix-inversion based minimum- variance-distortionless-response detectors in code-division- multiple-access systems“. Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18464.
Der volle Inhalt der QuelleCette thèse explore de nouvelles méthodes d'amélioration de la performance du détecteur MVDR dans des systèmes DS-CDMA BPSK lorsque le nombre de vecteurs reçus utilisés pour estimer la matrice de corrélation est peu élevé. Une analyse des détecteurs conventionnel et optimal ainsi que les méthodes principal component (PC), cross-spectral (CS) et auxiliary vector(AV) sont présentés. Le concept de filtrage widely linear (WL) est introduit. L'équivalence de deux versions différentes du filtre WL MVDR est démontrée. La réalisation du détecteur WL MVDR utilisant une structure AV est proposée et le gain de performance significatif accompli par ce détecteur est prouvé. Nous proposons aussi deux nouvelles méthodes de réalisation des filtres MVDR WL et régulier. La première méthode, basé sur l'idée de limiter les valeurs propres de la matrice de corrélation estimée, est moins performante que la méthode AV. L'autre méthode obtient une approximation de l'inverse de la matrice de corrélation estimée en inversant ses valeurs propres l'aide d'une fonction polynomiale. Cette méthode est meilleure que la méthode AV en terme de complexité tout en présentant des performances similaires.
SILVA, JORGE KENEDY ALMEIDA. „TECHNICAL REGULATION: PROPOSITION OF A MINIMUM CODE OF THE GOOD REGULATORY PRACTICES AND DIAGNOSIS OF THE BRAZILIAN SYSTEM“. PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9964@1.
Der volle Inhalt der QuelleObjetivo: Proposição de um código mínimo das boas práticas da regulamentação técnica com vistas a disciplinar o desenvolvimento e a aplicação de regulamentos e assegurar que estes somente sejam introduzidos quando justificados com base em objetivos legítimos e em benefício da eficiência de qualquer sistema regulatório, com o propósito de evitar barreiras desnecessárias ao comércio e sem prejuízo dos interesses públicos. Motivação: Contribuir para o avanço do conhecimento sobre regulamentação técnica e para o aprimoramento das práticas regulatórias do sistema brasileiro, assim facilitando a inserção comercial do País em âmbito internacional. Contextualização: O trabalho se desenvolveu no contexto de um movimento mundial de harmonização de nomenclaturas e procedimentos regulatórios ainda em uso nos países membros da Organização Mundial do Comércio, reconhecendo-se, entretanto, que aspectos puramente técnicos não são capazes de justificar um modelo unificado. Metodologia: A proposição das boas práticas da regulamentação baseou-se: (i) na análise das características mínimas dos sistemas regulatórios em relação às recomendações da Organização Mundial do Comércio, do Código de Alfândega e de acordos comerciais regionais e internacionais de conceituados organismos; (ii) no diagnóstico da regulamentação técnica vigente no País à luz da prática internacional e na identificação dos diferentes atores que integram o sistema regulatório brasileiro; e (iii) na identificação dos aspectos funcionais e na eficácia do sistema regulatório brasileiro, por meio de pesquisa de campo conduzida junto aos 29 organismos que integram o referido sistema. Resultados: À luz da prática internacional, o trabalho identifica, discute e fundamenta um conjunto de nove parâmetros considerados essenciais às boas práticas da regulamentação, a saber: (i) aderência aos preceitos básicos e nomenclatura internacional; (ii) coordenação integrada do sistema nacional de regulamentação; (iii) sistemática para avaliação de riscos pela introdução ou não de um determinado regulamento técnico; (iv) infra-estrutura de comitês técnicos; (v) sistema nacional de normalização; (vi) sistema nacional de metrologia; (vii) infra-estrutura básica para avaliação da conformidade; (viii) redes de segurança do sistema regulatório e (ix) acompanhamento de mercado. Conclusões: A introdução de um código de boas práticas da regulamentação constitui pré-condição ao adequado funcionamento de qualquer sistema regulatório. Nove atributos essenciais foram caracterizados à luz da prática internacional como elementos que devem integrar um código mínimo capaz de proporcionar a harmonização entre os órgãos regulamentadores do país, a interação dos órgãos regulamentadores com o Ponto Focal Brasileiro, a promoção da cidadania, o desenvolvimento econômico e a redução dos impactos sócio- econômico-ambientalcultural da regulamentação técnica.
Objectives: The aim of this study is to formalize a set of rules, principles and instruments to suit the purpose of a good technical regulatory practice that would discipline the development and application of technical regulations based on legitimate objectives oriented by public interests. Such framework is required for the benefit of an efficient regulatory system to avoid unnecessary barriers to trade and without loss of public interests. Motivation: To contribute to the advance of technical regulation and best regulatory practices in Brazil, as a strategy to promote the country internationally. Context: The study was developed in the context of a worldwide movement, coordinated by the WTO, to harmonize nomenclature and procedures and to develop good regulatory practices, recognizing that purely technical aspects are not suffice to justify an unified approach. Methodology: The good regulatory practice here proposed is based on: (i) a diagnosis of technical regulation in place (ii) a search of the minimum characteristics of the regulatory systems in the light of WTO recommendations and relevant commercial agreements and (iii) a review of the specialized literaure and an exploratory survey among the regulatory bodies to find out their functional and operational aspects. Results: In the light of international practices, this work identifies, discusses and establishes a set of guiding principles considered essential to good regulatory practice, namely: (i) adherence to basic precepts and international practices; (ii) risk assessment associated with the introduction or not of a specific regulation; (iii) integrated coordination of a national system of regulation; (iv) infra-structure of national committees; (v) a national system of standardization; (vi) a national system of metrology; (vii) basic infra-structure for conformity assessment; (viii) security networks for the regulatory system and (ix) market surveillance. Conclusions: The introduction of a code of regulatory practices constitutes a pre-condition to an adequate functioning of any regulatory system. In the light of the best international regulatory practices, nine essential attributes were identified to promote harmonization of the regulatory bodies and information exchange between them; citizenship; economic development and reduction of their cultural, environmental, economic and social impacts.
Bezerra, Kelton Silva. „Rigidity and unstability of hypersurfaces and an unicity theorem on semi-Rieamannian manifolds“. Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=16530.
Der volle Inhalt der QuelleOur aim in this work is threefold. First, we get an extension, to the spherical case, of a theorem due to J. Simons, which concerns unstability of minimal cones constructed over a certain class of minimal submanifolds of the Euclidean sphere. Second, we classify the quasi-Einstein structures of the Riemannian product Hn x R. Third, we get a rigidity theorem for complete hypersurfaces into the De Sitter space, under certain conditions on the mean and scalar curvatures.
Este trabalho aborda trÃs problemas em Geometria Diferencial. Primeiro, obtemos uma extensÃo, para o caso esfÃrico, de um teorema devido a J. Simons sobre instabilidade de cones mÃnimos construÃdos sobre uma certa classe de subvariedades mÃnimas da esfera Euclidiana. Depois, classificamos as estruturas quasi-Einstein existentes sobre o produto Riemanniano Hn X R. Por fim, obtemos um teorema de rigidez para hipersuperfÃcies tipo-espaÃo completas do espaÃo de De Sitter, sob certas condiÃÃes sobre as curvaturas mÃdia e escalar, alÃm de uma condiÃÃo de integrabilidade.
Beirami, Ahmad. „Characterizing the redundancy of universal source coding for finite-length sequences“. Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45750.
Der volle Inhalt der QuelleIrmer, Ralf. „Multiuser Transmission in Code Division Multiple Access Mobile Communications Systems“. Doctoral thesis, Aachen : Shaker, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=013194664&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Der volle Inhalt der QuelleIrmer, Ralf. „Multiuser Transmission in Code Division Multiple Access Mobile Communications Systems“. Doctoral thesis, Technische Universität Dresden, 2004. https://tud.qucosa.de/id/qucosa%3A24546.
Der volle Inhalt der QuelleDer codegeteilte Mehrfachzugriff (CDMA) wird bei allen zellularen Mobilfunksystemen der dritten Generation verwendet und ist ein aussichtsreicher Kandidat für zukünftige Technologien. Die Netzkapazität, also die Anzahl der Nutzer je Funkzelle, ist durch auftretende Interferenzen zwischen den Nutzern begrenzt. Für die Aufwärtsstrecke von den mobilen Endgeräten zur Basisstation können die Interferenzen durch Verfahren der Mehrnutzerdetektion im Empfänger verringert werden. Für die Abwärtsstrecke, die höhere Datenraten bei Multimedia-Anwendungen transportiert, kann das Sendesignal im Sender so vorverzerrt werden, dass der Einfluß der Interferenzen minimiert wird. Die informationstheoretische Motivation liefert dazu das Writing-on-Dirty-Paper Theorem. Das Signal-zu-Rausch-Verhältnis ist ein geeignetes Kriterium für die Performanz in rauschdominierten Szenarien. Mit Sende- und Empfangsfiltern kann das SNR durch den vorgeschlagenen Eigenprecoder maximiert werden. Durch den Einsatz von Mehrfachantennen im Sender und Empfänger kann die Performanz signifikant erhöht werden. Mit dem Generalized Selection MIMO Eigenprecoder können Transceiver mit reduzierter Komplexität ermöglicht werden. Sowohl für den Empfänger als auch für den Sender existieren Methoden, die Interferenzen vollständig zu eliminieren, oder den mittleren quadratischen Fehler zu minimieren. Der Maximum-Likelihood-Empfänger minimiert die Bitfehlerwahrscheinlichkeit (BER), hat jedoch kein entsprechendes Gegenstück im Sender. Die in dieser Arbeit vorgeschlagene Minimum Bit Error Rate Multiuser Transmission (TxMinBer) minimiert die BER am Detektor durch Sendesignalverarbeitung. Dieses nichtlineare Verfahren nutzt die Kenntnis der Datensymbole und des Mobilfunkkanals, um ein Sendesignal zu generieren, dass die BER unter Berücksichtigung einer Sendeleistungsnebenbedingung minimiert. Dabei werden nichtlineare Optimierungsverfahren wie Sequentielle Quadratische Programmierung (SQP) verwendet. Die Performanz linearer und nichtlinearer MUT-Verfahren MUT-Algorithmen mit linearen Empfängern wird am Beispiel des TD-SCDMA-Standards verglichen. Das Problem der Interferenzen kann mit allen untersuchten Verfahren gelöst werden, die TxMinBer-Methode benötigt jedoch die geringste Sendeleistung, um eine bestimmt Anzahl von Nutzern zu unterstützen. Die hohe Rechenkomplexität der MUT-Algorithmen ist ein wichtiges Problem bei der Implementierung in Real-Zeit-Systemen. Durch die Ausnutzung von Struktureigenschaften der Systemmatrizen kann die Komplexität der linearen MUT-Verfahren signifikant reduziert werden. Verschiedene Verfahren zur Invertierung der Systemmatrizen werden aufgezeigt und verglichen. Es werden Vorschläge gemacht, die Komplexität der Minimum Bit Error Rate Multiuser Transmission zu reduzieren, u.a. durch Vermeidung der Sendeleistungsnebenbedingung durch eine Beschränkung der Optimierung auf die Phasen des Sendesignalvektors. Die Komplexität der nichtlinearen Methoden ist um einige Größenordungen höher als die der linearen Verfahren. Weitere Forschungsanstrengungen an diesem Thema sowie die wachsende Rechenleistung von integrierten Halbleitern werden künftig die Ausnutzung der besseren Leistungsfähigkeit der nichtlinearen MUT-Verfahren erlauben.
David, Vincent. „Algorithmique parallèle sur les arbres de décision et raisonnement en temps contraint : étude et application au minimax“. Toulouse, ENSAE, 1993. http://www.theses.fr/1993ESAE0008.
Der volle Inhalt der QuelleÁvila, Dane Marques de. „O segundo peso de Hamming do código de Reed-Muller generalizado“. Universidade Federal de Uberlândia, 2016. https://repositorio.ufu.br/handle/123456789/16822.
Der volle Inhalt der QuelleIn this work we present the determination of the second Hamming weight of generalized Reed- Muller codes in most cases (see Teorema 4.6). Our main reference is [13], although we have also used results from [3] and [5]. In the first chapter we describe finite fields e we show how they can be constructed. In chapter 2 we present the basics of coding theory. We define what are error correcting codes, the Hamming metric, the parameters of a code, the equivalence of codes through the concept of isometry, and we briefly present generalized Reed-Muller codes and their parameters. In chapter 3 we present some results from Grobner bases theory and the definition of Affine Cartesian codes, which generalize the generalized Reed-Muller codes. we use tools from Grobner bases theory to determine the dimension and the minimum distance of Affine Cartesian codes. We finish our work in chapter 4, with the determination of the second Hamming weight for generalized Reed-Muller codes in most cases.
Nesse trabalho apresentamos o cálculo do segundo peso de Hamming de códigos de Reed-Muller generalizados na maioria dos casos (v. Teorema 4.6). Nossa referência principal sera [13], embora tenhamos utilizado também resultados de [3] e [5]. No primeiro capítulo descrevemos os corpos finitos e mostramos como podem ser construídos. No capítulo 2 apresentamos os conceitos básicos da teoria de códigos. Nele, definimos o que são os códigos corretores de erros, a métrica de Hamming, os parâmetros de um código, a equivalência de códigos através da noção de isometria, bem como uma breve apresentação dos códigos de Reed-Muller generalizados e seus parâmetros. No capítulo 3 sao apresentados alguns resultados da teoria de Bases de Grobner e a definição dos Códigos Cartesianos Afins, que são uma generalização dos códigos de Reed-Muller generalizados. Usamos ferramentas da teoria de bases de Grobner para determinar a dimensão e distância mínima de Códigos Cartesianos Afins. Para finalizar nosso trabalho, no capítulo 4 determinamos o segundo peso de Hamming do Código de Reed-Muller generalizado na maioria dos casos.
Mestre em Matemática
Bernon, Jérémy. „Caractérisation du secteur de Higgs et aspects du problème de la saveur“. Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY020/document.
Der volle Inhalt der QuelleThe Standard Model (SM) of particle physics stands as the most successful description of the fundamental interactions between elementary particles. The discovery of a Higgs boson, at a mass of 125 GeV, in July 2012 at the Large Hadron Collider (LHC), marked its ultimate confirmation. However, various observational and theoretical problems lie in the heart of the SM, with the majority of them linked to the Higgs sector. Being a scalar, the Higgs boson is subject to very large radiative corrections and this ultimately leads to the electroweak hierarchy problem. One of the main goals of the LHC program is to precisely probe the Higgs sector, in order to characterize the mechanism at the origin of the breaking of the electroweak symmetry and test possible solutions to the hierarchy problem. The Higgs sector is also responsible for the generation of the fermion masses, as it induces the Yukawa couplings. The SM flavor sector is highly hierarchical and this leads to flavor puzzles in theories beyond the SM.The first part of this thesis is dedicated to the precise characterization of the Higgs sector. In particular, the public tool Lilith is presented, which allows to derive constraints on new physics models based on the Higgs measurements at colliders. It is then used to perform global fits of the Higgs couplings in the context of various scenarios. In the second part, the phenomenology of two-Higgs-doublet models is studied in the light of the results from the first run of the LHC. The so-called alignment limit is explored in detail, as well as the possible presence of light scalar states. Finally, in the last part of this thesis, the Minimal Flavor Violation hypothesis is introduced as a possible solution to the flavor puzzles beyond the SM. Enforcing it in the Minimal Supersymmetric Standard Model, the renormalisation group evolution of the baryonic R-parity violating couplings is then studied in detail
Oliveira, Fabrício Alves. „Códigos parametrizados afins“. Universidade Federal de Uberlândia, 2014. https://repositorio.ufu.br/handle/123456789/16809.
Der volle Inhalt der QuelleIn this work, we present a special class of linear codes: parameterized affine codes. We show that these codes are easy to construct and that given a parameterized affine code one can easily obtain an equivalent projective parameterized code equivalent to it. We also studied some topics which served as the theoretical foundations for the work, such as the theory of Groebner Bases, the footprint of an ideal and some topics of algebraic geometry and commutative algebra. This work has as main goal to obtain the basic parameters (length, dimension and minimum distance) of parameterized codes related and also to relate them to the projective parameterized codes, as done in [7]. We finish by applying the theory of Groebner Bases to the footprint of a certain ideal in order to obtain the basic parameters of the parameterized code over an affine torus.
Neste trabalho apresentamos uma classe especial de códigos lineares: os códigos parametrizados afins. Mostramos que esses códigos são de fácil construção e que, dado um código parametrizado afim, pode-se facilmente obter um código parametrizado projetivo equivalente a ele. Também estudamos algumas teorias que nos serviram como base teórica tais como: a teoria de Bases de Groebner e a Pegada de um ideal e alguns tópicos de geometria algébrica e álgebra comutativa. Este trabalho tem por objetivo principal obter os parâmetros básicos (comprimento, dimensão e distância mínima) dos códigos parametrizados afins e relacioná-los com os códigos parametrizados projetivos, assim como na referência [7]. Encerramos aplicando a teoria de Bases de Groebner a Pegada de um ideal para obter os parâmetros básicos do código parametrizado no toro afim.
Mestre em Matemática
Marachli, Alaa. „Sur la stabilité de certaines surfaces minimales sous le flot de courbure moyenne nulle dans l'espace de Minkowski“. Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC0034.
Der volle Inhalt der QuelleThis thesis focuses on the stability of some minimal surfaces under the vanishing mean curvature flow in Minkowski space. This issue amounts to investigate a system which turns out to be hyperbolic as long as the involved surfaces are time-like surfaces.The work presented here includes two parts. The first part in joint work with Hajer Bahouri and Galina Perelman is dedicated to the issue of singularity formation in finite time for surfaces asymptotic to the Simons cone at infinity and the second part is devoted to the study of the stability of the helicoid.In the first part of this thesis, we prove by a constructive approach the existence of a family of surfaces which evolve by the vanishing mean curvature flow in Minkowski space and which as t tends to~0 blow up towards a surface which behaves like the Simons cone at infinity. This issue amounts to investigate the singularity formation for a second order quasilinear wave equation.The aim of the second part is to investigate the stability of the helicoid under normal radial perturbations. Actually, the helicoid is linearly unstable of index 1, and that is why we cannot expect to have stability for arbitrary perturbations. In this part, we establish that this instability is the only obstruction to the global nonlinear stability for the helicoid. More precisely, in the framework of normal radial perturbations, we prove the existence of a codimension one set of small initial data generating global solutions converging to the helicoid at infinity