Spelling suggestions: "subject:"space/time"" "subject:"apace/time""
211 |
Real-Time Space-Time Adaptive Processing on the STI CELL MultiprocessorLi, Yi-Hsien January 2007 (has links)
Space-Time Adaptive Processing (STAP) has been widely used in modern radar systems such as Ground Moving Target Indication (GMTI) systems in order to suppress jamming and interference. However, the high performance comes at a price of higher computational complexity, which requires extensive powerful hardware. The new STI Cell Broadband Engine (CBE) processor combines PowerPC core augmented with eight streamlined high-performance SIMD processing engine offers an opportunity to implement the STAP baseband signal processing without any full custom hardware. This paper presents the implementation of an STAP baseband signal processing flow on the state-of-the-art STI CELL multiprocessor, which enables the concept of Software-Defined Radar (SDR). The potential of the Cell BE processor is studied so that kernel subroutine such as QR decomposition, Fast Fourier Transform (FFT), and FIR filtering of STAP are mapped to the SPE co-processors of Cell BE processor with variety of architectural specific optimization techniques. This report starts with an overview of airborne radar technique and then the standard, specifically the third-order Doppler-factored STAP are introduced. Next, it goes with the thorough description of Cell BE architecture, its programming tool chain and parallel programming methods for Cell BE. In later chapter, how the STAP is implemented on the Cell BE processor is discussed and the simulation results are presented. Furthermore, based on the result of earlier benchmarking, an optimized task partition and scheduling method is proposed to improve the overall performance.
|
212 |
Study and optimization of new differential space-time modulation schemes based on the Weyl group for the second generation of MIMO systems / Etude et optimisation de nouveaux schémas de codage temps-espace différentiels basés sur le groupe de Weyl pour la seconde génération de systèmes MIMOJi, Hui 09 November 2015 (has links)
Actuellement, l’étude des systèmes multi-antennaires MIMO (Multiple Input Multiple Output) est orientée dans beaucoup de cas vers l’augmentation considérable du nombre d’antennes de la station de base (« massive MIMO », « large-scale MIMO »), afin notamment d’augmenter la capacité de transmission, réduire l’énergie consommée par bit transmis, exploiter la dimension spatiale du canal de propagation, diminuer l’influence des évanouissements, etc. Pour les systèmes MIMO à bande étroite ou ceux utilisant la technique OFDM (Orthogonal Frequency Division Multiplex), le canal de propagation (ou les sous-canaux correspondants à chaque sous-porteuse d’un système OFDM) sont pratiquement plats (non-sélectifs en fréquence), ce qui revient à considérer la réponse fréquentielle de chaque canal SISO invariante par rapport à la fréquence mais variante dans le temps. Ainsi, le canal de propagation MIMO peut être caractérisé en bande de base par une matrice dont les coefficients sont des nombres complexes. Les systèmes MIMO cohérents nécessitent pour pouvoir démoduler le signal en réception de disposer de la connaissance de cette matrice de canal, donc le sondage périodique, en temps réel, du canal de propagation. L’augmentation du nombre d’antennes et la variation dans le temps, parfois assez rapide, du canal de propagation, rend ce sondage de canal difficile, voire impossible. Il est donc intéressant d’étudier des systèmes MIMO différentiels qui n’ont pas besoin de connaître la matrice de canal. Pour un bon fonctionnement de ces systèmes, la seule contrainte est que la matrice de canal varie peu pendant la transmission de deux matrices d’information successives. Le sujet de cette thèse concerne l’étude et l’analyse de nouveaux systèmes MIMO différentiels. On considère des systèmes à 2, 4 et 8 antennes d’émission, mais la méthode utilisée peut être étendue à des systèmes MIMO avec 2n antennes d’émission, le nombre d’antennes de réception étant quelconque. Pour les systèmes MIMO avec 2 antennes d’émission qui ont été étudiés dans le cadre de cette thèse, les matrices d’information sont des éléments du groupe de Weyl. Pour les systèmes avec 2n antennes d’émission, (n ≥ 2), les matrices utilisées sont obtenues en effectuant des produits de Kronecker des matrices unitaires du groupe de Weyl. Pour chaque nombre d’antennes d’émission on identifie d’abord le nombre de matrices disponibles et on détermine la valeur maximale de l’efficacité spectrale. Pour chaque valeur de l’efficacité spectrale on détermine les meilleurs sous-ensembles de matrices d’information à utiliser (selon le spectre des distances ou le critère du produit de diversité). On optimise ensuite la correspondance ou mapping entre les vecteurs binaires et les matrices d’information. Enfin, on détermine par simulation les performances des systèmes MIMO différentiels ainsi obtenus et on les compare avec celles des systèmes similaires existants. […] / At present, the study of multi-antenna systems MIMO (Multiple Input Multiple Output) is developed in many cases to intensively increase the number of base station antennas («massive MIMO», «largescale MIMO»), particularly in order to increase the transmission capacity, reduce energy consumed per bit transmitted, exploit the spatial dimension of the propagation channel, reduce the influence of fading, etc. For MIMO systems with narrowband or those using OFDM technique (Orthogonal Frequency Division Multiplex), the propagation channel (or the sub-channels corresponding to each sub-carrier of an OFDM system) are substantially flat (frequency non-selective). In this case the frequency response of each SISO channel is invariant with respect to frequency, but variant in time. Furthermore, the MIMO propagation channel can be characterized in baseband by a matrix whose coefficients are complex numbers. Coherent MIMO systems need to have the knowledge of the channel matrix to be able to demodulate the received signal. Therefore, periodic pilot should be transmitted and received to estimate the channel matrix in real time. The increase of the number of antennas and the change of the propagation channel over time, sometimes quite fast, makes the channel estimation quite difficult or impossible. It is therefore interesting to study differential MIMO systems that do not need to know the channel matrix. For proper operation of these systems, the only constraint is that the channel matrix varies slightly during the transmission of two successive information matrices. The subject of this thesis is the study and analysis of new differential MIMO systems. We consider systems with 2, 4 and 8 transmit antennas, but the method can be extended to MIMO systems with 2n transmit antennas, the number of receive antennas can be any positive integer. For MIMO systems with two transmit antennas that were studied in this thesis, information matrices are elements of the Weyl group. For systems with 2n (n ≥ 2) transmit antennas, the matrices used are obtained by performing the Kronecker product of the unitary matrices in Weyl group. For each number of transmit antennas, we first identify the number of available matrices and the maximum value of the spectral efficiency. For each value of the spectral efficiency, we then determine the best subsets of information matrix to use (depending on the spectrum of the distances or the diversity product criterion). Then we optimize the correspondence or mapping between binary vectors and matrices of information. Finally, the performance of differential MIMO systems are obtained by simulation and compared with those of existing similar systems. […]
|
213 |
TRANSFORMAÇÕES NA ORGANIZAÇÃO ESPACIAL DO MUNICÍPIO DE RIO PARDO RS / TRANSFORMATIONS IN THE TERRITORIAL ORGANIZATION OF RIO PARDO COUNTY RSSilveira, Emerson Lizandro Dias 24 November 2009 (has links)
The present thesis aims to understand the process of territorial organization of Rio Pardo County (RS) from territorial transformations throughout distinct historical
moments, since its foundation until the contemporary action of new political and economical factors which take place in the county observed. The main objectives sought here are: (a) characterize the differing marks of economic stagnation undertaken by the county along time; (b) apprehend the economic effects of the globalization process in the Gaucha economy as well as in Rio Pardo county which is responsible for transformations in traditional agricultural activities; (c) comprehend
the State role and also the public policies and private companies in Rio Pardo, that redefine new dynamics and territorial functionalities; (d) verify how such new
dynamics cause repercussion in the social and economic sectors; as well as in the culture, reorganizing the territory of the county observed. The methodology of this
study is based on the dialectic method, aiming to comprehend along time the different historical periods of development and stagnation that Rio Pardo went
through; and its social-territorial consequences. The research was carried out through a collection of primary data, such as semi-structured and open interviews
and photographic record taken during field work. All secondary data was extracted from publications of the Statistic and Geographical Brazilian Institute, from FEE
(State Economical Foundation) and Emater. The territorial organization of Rio Pardo county is the result of a historical process that is confused with Rio Grande do Sul
own history. In reason of many transformations of the social, political and economic order suffered by the gaucho territory, the city was losing importance in the political and economic scenarios; as it kept its productive base set in the traditional and animal agriculture; therefore becoming a stagnated territory with no economic dynamics able to attract investments and develop itself. Currently in reason of the new capitalist thinking in Rio Grande do Sul and different public policies towards development, it s possible to notice new dynamics taking place in the territory and causing technical, cultural, political and economical changes in Rio Pardo. / A presente dissertação busca compreender o processo de organização espacial do município de Rio Pardo(RS) a partir das transformações territoriais em distintos momentos históricos, desde sua fundação, até a ação contemporânea dos novos atores econômicos e políticos que se articulam no município em estudo. Os objetivos específicos buscam: (a) caracterizar os diferentes marcos de estagnação econômica
sofridos pelo município ao longo do tempo;(b) apreender os efeitos do processo de globalização na economia gaúcha e no município de Rio Pardo, o qual é responsável por transformações nas atividades agrícolas tradicionais; (c)
compreender o papel do estado, das políticas públicas e das empresas privadas em Rio Pardo, os quais redefinem novas dinâmicas e funcionalidades espaciais; (d) verificar como as novas dinâmicas repercutem nos setores econômicos, sociais e na cultura, reorganizando o espaço do município em estudo. A metodologia de pesquisa embasa-se no método dialético, buscando compreender, ao longo do tempo, os diferentes períodos históricos de desenvolvimento e estagnação que Rio
Pardo sofreu, bem como suas consequências sócioespaciais. A pesquisa foi realizada a partir da coleta de dados primários, tais como entrevistas semiestruturadas e abertas e registros fotográficos através de trabalho de campo. Os dados secundários foram extraídos de publicações do Instituto Brasileiro de Geografia e Estatística, da FEE (Fundação de Economia e Estatística) e Emater. A organização espacial do município de Rio Pardo é resultado de um processo histórico que confunde-se com a própria história do Rio Grande do Sul. Em função de diversas transformações de ordem econômica, política, social e cultural sofridas pelo território gaúcho, a cidade foi perdendo importância no cenário econômico e
político, pois manteve sua base produtiva assentada na agropecuária tradicional, tornando-se um espaço estagnado, sem dinamismo econômico capaz de atrair investimentos e de se desenvolver. Atualmente, em função das novas lógicas
capitalistas no Rio Grande do Sul e de diferentes políticas públicas desenvolvimentistas, percebem-se novas dinâmicas que se desenham no espaço e provocam mudanças econômicas, políticas, culturais e técnicas em Rio Pardo.
|
214 |
Space-Time Transportation System Modelling: from Traveler’s Characteristics to the Network Design ProblemParsafard, Mohsen 29 June 2017 (has links)
Traditional network design problems only consider the long-term stationary travel patterns (e.g., fixed OD demand) and short-term variations of human mobility are ignored. This study aims to integrate human mobility characteristics and travel patterns into network design problems using a space-time network structure. Emerging technologies such as location-based social network platforms provide a unique opportunity for understanding human mobility patterns that can lead to advanced modeling techniques. To reach our goal, at first multimodal network design problems are investigated by considering safety and flow interactions between different modes of transport. We develop a network reconstruction method to expand a single-modal transportation network to a multi-modal network where flow interactions between different modes can be quantified. Then, in our second task, we investigate the trajectory of moving objects to see how they can reveal detailed information about human travel characteristics and presence probability with high-resolution detail. A time geography-based methodology is proposed to not only estimate an individual’s space-time trajectory based on his/her limited space-time sample points but also to quantify the accuracy of this estimation in a robust manner. A series of measures including activity bandwidth and normalized activity bandwidth are proposed to quantify the accuracy of trajectory estimation, and cutoff points are suggested for screening data records for mobility analysis.
Finally, a space-time network-based modeling framework is proposed to integrate human mobility into network design problems. We construct a probabilistic network structure to quantify human’s presence probability at different locations and time. Then, a Mixed Integer Nonlinear Programming (MINLP) model is proposed to maximize the spatial and temporal coverage of individual targets. To achieve near optimal solutions for large-scale problems, greedy heuristic, Lagrangian relaxation and simulated annealing algorithms are implemented to solve the problem. The proposed algorithms are implemented on hypothetical and real world numerical examples to demonstrate the performance and effectiveness of the methodology on different network sizes and promising results have been obtained.
|
215 |
Space-time turbo coded modulation for wireless communication systemsTujkovic, D. (Djordje) 23 April 2003 (has links)
Abstract
High computational complexity constrains truly exhaustive computer searches for good space-time (ST) coded modulations mostly to low constraint length space-time trellis codes (STTrCs). Such codes are primarily devised to achieve maximum transmit diversity gain. Due to their low memory order, optimization based on the design criterion of secondary importance typically results in rather modest coding gains. As another disadvantage of limited freedom, the different low memory order STTrCs are almost exclusively constructed for either slow or fast fading channels. Therefore in practical applications characterized by extremely variable Doppler frequencies, the codes typically fail to demonstrate desired robustness. On the other hand, the main drawback of eventually increased constraint lengths is the prohibitively large decoding complexity, which may increase exponentially if optimal maximum-likelihood decoding (MLD) is applied at the receiver. Therefore, robust ST coded modulation schemes with large equivalent memory orders structured as to allow sub-optimal, low complexity, iterative decoding are needed.
To address the aforementioned issues, this thesis proposes parallel concatenated space-time turbo coded modulation (STTuCM). It is among the earliest multiple-input multiple-output (MIMO) coded modulation designs built on the intersection of ST coding and turbo coding. The systematic procedure for building an equivalent recursive STTrC (Rec-STTrC) based on the trellis diagram of an arbitrary non-recursive STTrC is first introduced. The parallel concatenation of punctured constituent Rec-STTrCs designed upon the non-recursive Tarokh et al. STTrCs (Tarokh-STTrCs) is evaluated under different narrow-band frequency flat block fading channels. Combined with novel transceiver designs, the applications for future wide-band code division multiple access (WCDMA) and orthogonal frequency division multiplexing (OFDM) based broadband radio communication systems are considered. The distance spectrum (DS) interpretation of the STTuCM and union bound (UB) performance analysis over slow and fast fading channels reveal the importance of multiplicities in the ST coding design. The modified design criteria for space-time codes (STCs) are introduced that capture the joint effects of error coefficients and multiplicities in the two dimensional DS of a code. Applied to STTuCM, such DS optimization resulted in a new set of constituent codes (CCs) for improved and robust performance over both slow and fast fading channels. A recursive systematic form with a primitive equivalent feedback polynomial is assumed for CCs to assure good convergence in iterative decoding. To justify such assumptions, the iterative decoding convergence analysis based on the Gaussian approximation of the extrinsic information is performed. The DS interpretation, introduced with respect to an arbitrary defined effective Hamming distance (EHD) and effective product distance (EPD), is applicable to the general class of geometrically non-uniform (GNU) CCs. With no constrains on the implemented information interleaving, the STTuCM constructed from newly designed CCs achieves full spatial diversity over quasi-static fading channels, the condition commonly identified as the most restrictive for robust performance over a variety of Doppler spreads. Finally, the impact of bit-wise and symbol-wise information interleaving on the performance of STTuCM is studied.
|
216 |
Utópia v diele Aleja Carpentiera / The Concept of Utopia in the Work of Alejo CarpentierMištríková, Jana January 2017 (has links)
The goal of this master's thesis was to focus on the presence of utopia in three works written by the Cuban writer Alejo Carpentier The Lost Steps (Los pasos perdidos), Explosion in a Cathedral (El siglo de las luces) and The Kingdom of this World (El reino de este mundo). It has been defined the characteristics of utopia as a literary genre, which have been subsequently applied to the novels mentioned above. The study devoted to the novel The Lost Steps was the most detailed one. Attention was also paid to writer's perceptions of Latin America through "marvelous real".
|
217 |
ROTARY-WING FLIGHT TESTS TO DETERMINE THE BENEFITS OF FREQUENCY AND SPATIAL DIVERSITY AT THE YUMA PROVING GROUNDDiehl, Michael, Swain, Jason, Wilcox, Tab 11 1900 (has links)
The United States (U.S.) Army Yuma Proving Ground (YPG) conducted a series of rotary-wing
flight tests for the sole purpose of checking out Telemetry data link instrumentation. Four flights
were conducted at YPG in February 2016 that built upon an earlier test flight conducted in June
2015. The most recent iteration of testing examined the benefits of frequency diversity on aircraft
and the spatial diversity of receiving sites using existing hardware at YPG. Quantitative analysis
from those flight results will be presented and include discussion on how results will affect future
mission operations at YPG.
|
218 |
Combinación de Códigos LDPC No Binarios con Sphere Packing y Space TimeVergara Ordenes, Italo Rodrigo January 2007 (has links)
No description available.
|
219 |
Análise espaço-temporal da leishmaniose visceral americana no município de Bauru, São Paulo / Space-time analysis of American visceral leishmaniasis in Bauru, São PauloSouza, Vanessa Aparecida Feijó de 07 July 2010 (has links)
Uma análise espaço-temporal da leishmaniose visceral americana (LVA) humana no município de Bauru foi conduzida baseada em 239 casos diagnosticados entre junho de 2003 a outubro de 2008. O georreferenciamento, tomando como unidade os setores censitários, foi realizado a partir de informações cedidas pela Secretaria de Saúde de Bauru a respeito do endereço residencial dos pacientes acometidos pela enfermidade. A análise da distribuição espacial da doença demonstrou que os casos ocorreram especialmente na área urbana do município. As incidências cumulativas anuais de LVA, considerando os casos adotados por ano e as respectivas projeções populacionais, foram calculadas, evidenciando que a taxa mais elevada foi observada em 2006. Tal fato foi confirmado pelo delineamento da série histórica, que também derivou o cálculo da tendência, demonstrando que esta foi positiva durante o período analisado. O índice sazonal obtido foi confrontado com dados referentes às médias mensais de precipitação pluviométrica e temperatura do município, o que nos permitiu inferir que meses que obtiveram índices com valores superiores a um, eram, de maneira geral, precedidos por períodos chuvosos. A variável temperatura, por sua vez, apesar de provavelmente estar relacionada à ocorrência da enfermidade na região, aparentemente não exerceu influência na sazonalidade da doença por se apresentar sem oscilações importantes no período. A análise de clusters, utilizando o método estatístico espaço-temporal scan, detectou um provável aglomerado localizado nas regiões sudoeste e central do município no ano de 2006. Uma análise descritiva univariada, comparando setores censitários que apresentaram LVA com relação aos que não relataram casos da doença, foi conduzida. Apesar da diferença significativa observada entre os dois grupos, novos estudos são necessários para se confirmar a hipótese de que variáveis socioeconômicas são prováveis fatores de risco para a infecção na região. / A space-time analysis of human American visceral leishmaniasis (AVL) was carried out based on 239 cases diagnosed from June 2003 through October 2008. The georeferencing, taking the census tracts as units, was performed according to information supplied by the Bauru Health Department about AVL patient addresses. The disease spatial analysis showed that cases occurred specially at the urban area of the city. AVL annual incidence rates, considering adopted cases per year and the respective projected population, were calculated, demonstrating that the highest rate was observed in 2006. It was confirmed by the time series analysis, which also resulted the tendency calculation, showing that it was positive during the analyzed moment. The obtained seasonal indices were confronted with data about the citys average rainfall and temperature, which allowed us to infer that months with indices higher than one, were, generally, preceded by rainy periods. The temperature, on the other hand, although is probably related to the infection occurrence at the region, seemingly did not exert influence on the disease seasonality because it was presented without important fluctuations in the period. The cluster analysis, using scan space-time statistics, detected a most likely cluster located in the Southwest and Central city side in 2006. A univariate descriptive analysis, comparing census tracts that presented AVL with those that did not report case disease, was carried out. Although the significant difference observed between both groups, new researchers are needed to confirm the hypothesis that socioeconomic variables were likely infection risk factors in the region.
|
220 |
Modeling space-time activities and places for a smart space —a semantic approachFan, Junchuan 01 August 2017 (has links)
The rapid advancement of information and communication technologies (ICT) has dramatically changed the way people conduct daily activities. One of the reasons for such advances is the pervasiveness of location-aware devices, and people’s ability to publish and receive information about their surrounding environment. The organization, integration, and analysis of these crowdsensed geographic information is an important task for GIScience research, especially for better understanding place characteristics as well as human activities and movement dynamics in different spaces. In this dissertation research, a semantic modeling and analytic framework based on semantic web technologies is designed to handle information related with human space-time activities (e.g., information about human activities, movement, and surrounding places) for a smart space. Domain ontology for space-time activities and places that captures the essential entities in a spatial domain, and the relationships among them. Based on the developed domain ontology, a Resource Description Framework (RDF) data model is proposed that integrates spatial, temporal and semantic dimensions of space-time activities and places. Three different types of scheduled space-time activities (SXTF, SFTX, SXTX) and their potential spatiotemporal interactions are formalized with OWL and SWRL rules. Using a university campus as an example spatial domain, a RDF knowledgebase is created that integrates scheduled course activities and tweet activities in the campus area. Human movement dynamics for the campus area is analyzed from spatial, temporal, and people’s perspectives using semantic query approach. The ontological knowledge in RDF knowledgebase is further fused with place affordance knowledge learned through training deep learning model on place review data. The integration of place affordance knowledge with people’s intended activities allows the semantic analytic framework to make more personalized location recommendations for people’s daily activities.
|
Page generated in 0.0608 seconds