Multicasting can be done in two different ways: source based tree approach andshared tree approach. Shared tree approach is preferred over source-based treeapproach because in the later construction of minimum cost tree per source is neededunlike a single shared tree in the former approach. However, in shared tree approach asingle core needs to handle the entire traffic load resulting in degraded multicastperformance. Besides, it also suffers from „single point failure‟. Multicast is acommunication between one or multiple senders and multiple receivers, which used asa way of sending IP datagrams to a group of interested receivers in one transmission.Core-based trees major concerns are core selection and core as single point of failure.The problem of core selection is to choose the best core or cores in the network toimprove the network performance.In this dissertation we propose 1) a multiple core selection approach for core-based tree multicasting, senders can select different cores to have an efficient loadbalanced multicore multicasting. It will overcome any core failure as well. 2) Novel andefficient schemes for load shared multicore multicasting are presented. Multiple coresare selected statically, that is, independent of any existing multicast groups and also theselection process is independent of any underlying unicast protocol. Some of theselected cores can be used for fault- tolerant purpose also to guard against any possible core failures. 3) We have presented two novel and efficient schemes forgroup-based load shared multicore multicasting in which members of a multicast groupuse the same core tree for their multicasting. 4) We also presented two schemes aim atachieving low latency multicasting along with load sharing for delay sensitive multicastapplications. Besides, we have presented a unique approach for core migration, whichuses two very important parameters, namely, depth of a core tree and pseudo diameterof a core. One noteworthy point from the viewpoint of fault tolerance is that the degreeof fault-tolerance can be enhanced from covering single point-failure to any number ofcore failures.

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Esta pesquisa propõe-se a oferecer uma análise inédita sobre o campo de administração pública, utilizando metodologias da área de sistemas complexos para interpretar questões pertinentes ao objeto de pesquisa. Dessa forma, buscou-se mapear e construir a rede de pesquisadores em Administração Pública, como forma de oferecer subsídios para constatações e reflexões específicas sobre o campo, complementando alguns estudos já realizados, bem como oferecendo novos subsídios para análises sobre seu desenvolvimento. Desta forma, fundamentado em problemas específicos do campo de administração pública, já constatados em outros estudos, utiliza-se a metodologia de redes complexas, para modelagem desta rede. Para tanto, foram coletados dados dos principais eventos (EnANPAD e EnAPG) e periódicos (RAC, RAP, RSP e O&S) do campo, no período recente (2000 2010) para composição e posterior análise de sua configuração. A análise se deu a partir da evolução da rede em termos de número de pesquisadores e artigos publicados, bem como pela constatação dos pesquisadores mais prolíficos, com a finalidade de verificar alguns aspectos peculiares ao campo. Como resultado, verificou-se o crescimento do campo no período recente, acompanhado da inclusão de novos pesquisadores, mas que não representam, necessariamente, a consolidação do campo, haja vista a pouca permanência que estes têm no campo ao longo dos anos. Ademais, verificou-se que os principais pesquisadores, que possuem fortes laços com as tradicionais instituições do campo, na maioria das vezes não têm formação acadêmica diretamente ligada a área, bem como apresentam produção científica dispersa. Tais constatações reforçam, de maneira quanti e qualitativa, as dificuldades próprias do campo de administração pública / This research proposes to offer a unprecedented analysis about the field of public administration, using methodologies in the area of complex systems, to interpret questions pertaining to the object of research. Thus, this study sought to map and build the network of researchers in public administration as a way to provide insights to specific findings and specific reflections about the field, complementing some previous studies, as well as offering new subsidies for analysis on their development. Thus, based on the specific problems of the public administration field, already observed in other studies, it was used the methodology of complex systems, especially complex networks for modeling this network. Therefore, data were collected from major events (EnANPAD and EnAPG) and journals (RAC, RAP, RSP and O & S) of the field in the recent period (2000 - 2010) for the composition and subsequent analysis of its configuration. The analysis was performed based on network evolution in terms of number of researchers and published articles, as well as the identification of the most prolific researchers, in order to verify some aspects peculiar to the field. As a result, it was found the growth of the field in recent years, followed by the inclusion of new researchers, which not necessarily represent the consolidation of the field, due to the low permanence that they have in it over the years. Moreover, it was found that the main researchers, who have strong ties to traditional institutions of the field, most of the time, have no academic graduation directly linked to the area and present scientific production dispersed. Such findings reinforce, so quantitative and qualitative, the difficulties inherent to the field of public administration

Esta pesquisa propõe-se a oferecer uma análise inédita sobre o campo de administração pública, utilizando metodologias da área de sistemas complexos para interpretar questões pertinentes ao objeto de pesquisa. Dessa forma, buscou-se mapear e construir a rede de pesquisadores em Administração Pública, como forma de oferecer subsídios para constatações e reflexões específicas sobre o campo, complementando alguns estudos já realizados, bem como oferecendo novos subsídios para análises sobre seu desenvolvimento. Desta forma, fundamentado em problemas específicos do campo de administração pública, já constatados em outros estudos, utiliza-se a metodologia de redes complexas, para modelagem desta rede. Para tanto, foram coletados dados dos principais eventos (EnANPAD e EnAPG) e periódicos (RAC, RAP, RSP e O&S) do campo, no período recente (2000 2010) para composição e posterior análise de sua configuração. A análise se deu a partir da evolução da rede em termos de número de pesquisadores e artigos publicados, bem como pela constatação dos pesquisadores mais prolíficos, com a finalidade de verificar alguns aspectos peculiares ao campo. Como resultado, verificou-se o crescimento do campo no período recente, acompanhado da inclusão de novos pesquisadores, mas que não representam, necessariamente, a consolidação do campo, haja vista a pouca permanência que estes têm no campo ao longo dos anos. Ademais, verificou-se que os principais pesquisadores, que possuem fortes laços com as tradicionais instituições do campo, na maioria das vezes não têm formação acadêmica diretamente ligada a área, bem como apresentam produção científica dispersa. Tais constatações reforçam, de maneira quanti e qualitativa, as dificuldades próprias do campo de administração pública / This research proposes to offer a unprecedented analysis about the field of public administration, using methodologies in the area of complex systems, to interpret questions pertaining to the object of research. Thus, this study sought to map and build the network of researchers in public administration as a way to provide insights to specific findings and specific reflections about the field, complementing some previous studies, as well as offering new subsidies for analysis on their development. Thus, based on the specific problems of the public administration field, already observed in other studies, it was used the methodology of complex systems, especially complex networks for modeling this network. Therefore, data were collected from major events (EnANPAD and EnAPG) and journals (RAC, RAP, RSP and O & S) of the field in the recent period (2000 - 2010) for the composition and subsequent analysis of its configuration. The analysis was performed based on network evolution in terms of number of researchers and published articles, as well as the identification of the most prolific researchers, in order to verify some aspects peculiar to the field. As a result, it was found the growth of the field in recent years, followed by the inclusion of new researchers, which not necessarily represent the consolidation of the field, due to the low permanence that they have in it over the years. Moreover, it was found that the main researchers, who have strong ties to traditional institutions of the field, most of the time, have no academic graduation directly linked to the area and present scientific production dispersed. Such findings reinforce, so quantitative and qualitative, the difficulties inherent to the field of public administration

As the next evolutionary step in digital communication systems, mobile ad hoc networks (MANETs) and their specialization like wireless sensor networks (WSNs) have been attracting much interest in both research and industry communities. In MANETs, network nodes can come together and form a network without depending on any pre-existing infrastructure and human intervention. Unfortunately, the salient characteristics of MANETs, in particular the absence of infrastructure and the constrained resources of mobile devices, present enormous challenges when designing security mechanisms in this environment. Without necessary measures, wireless communications are easy to be intercepted and activities of users can be easily traced. This thesis presents our solutions for two important aspects of securing MANETs, namely efficient key management protocols and fast implementations of cryptographic primitives on constrained devices. Due to the tight cost and constrained resources of high-volume mobile devices used in MANETs, it is desirable to employ lightweight and specialized cryptographic primitives for many security applications. Motivated by the design of the well-known Enigma machine, we present a novel ultra-lightweight cryptographic algorithm, referred to as Hummingbird, for resource-constrained devices. Hummingbird can provide the designed security with small block size and is resistant to the most common attacks such as linear and differential cryptanalysis. Furthermore, we also present efficient software implementations of Hummingbird on 4-, 8- and 16-bit microcontrollers from Atmel and Texas Instruments as well as efficient hardware implementations on the low-cost field programmable gate arrays (FPGAs) from Xilinx, respectively. Our experimental results show that after a system initialization phase Hummingbird can achieve up to 147 and 4.7 times faster throughput for a size-optimized and a speed-optimized software implementation, respectively, when compared to the state-of-the-art ultra-lightweight block cipher PRESENT on the similar platforms. In addition, the speed optimized Hummingbird encryption core can achieve a throughput of 160.4 Mbps and the area optimized encryption core only occupies 253 slices on a Spartan-3 XC3S200 FPGA device. Bilinear pairings on the Jacobians of (hyper-)elliptic curves have received considerable attention as a building block for constructing cryptographic schemes in MANETs with new and novel properties. Motivated by the work of Scott, we investigate how to use efficiently computable automorphisms to speed up pairing computations on two families of non-supersingular genus 2 hyperelliptic curves over prime fields. Our findings lead to new variants of Miller's algorithm in which the length of the main loop can be up to 4 times shorter than that of the original Miller's algorithm in the best case. We also generalize Chatterjee et al.'s idea of encapsulating the computation of the line function with the group operations to genus 2 hyperelliptic curves, and derive new explicit formulae for the group operations in projective and new coordinates in the context of pairing computations. Efficient software implementation of computing the Tate pairing on both a supersingular and a non-supersingular genus 2 curve with the same embedding degree of k = 4 is investigated. Combining the new algorithm with known optimization techniques, we show that pairing computations on non-supersingular genus 2 curves over prime fields use up to 55.8% fewer field operations and run about 10% faster than supersingular genus 2 curves for the same security level. As an important part of a key management mechanism, efficient key revocation protocol, which revokes the cryptographic keys of malicious nodes and isolates them from the network, is crucial for the security and robustness of MANETs. We propose a novel self-organized key revocation scheme for MANETs based on the Dirichlet multinomial model and identity-based cryptography. Firmly rooted in statistics, our key revocation scheme provides a theoretically sound basis for nodes analyzing and predicting peers' behavior based on their own observations and other nodes' reports. Considering the difference of malicious behaviors, we proposed to classify the nodes' behavior into three categories, namely good behavior, suspicious behavior and malicious behavior. Each node in the network keeps track of three categories of behavior and updates its knowledge about other nodes' behavior with 3-dimension Dirichlet distribution. Based on its own analysis, each node is able to protect itself from malicious attacks by either revoking the keys of the nodes with malicious behavior or ceasing the communication with the nodes showing suspicious behavior for some time. The attack-resistant properties of the resulting scheme against false accusation attacks launched by independent and collusive adversaries are also analyzed through extensive simulations. In WSNs, broadcast authentication is a crucial security mechanism that allows a multitude of legitimate users to join in and disseminate messages into the networks in a dynamic and authenticated way. During the past few years, several public-key based multi-user broadcast authentication schemes have been proposed in the literature to achieve immediate authentication and to address the security vulnerability intrinsic to μTESLA-like schemes. Unfortunately, the relatively slow signature verification in signature-based broadcast authentication has also incurred a series of problems such as high energy consumption and long verification delay. We propose an efficient technique to accelerate the signature verification in WSNs through the cooperation among sensor nodes. By allowing some sensor nodes to release the intermediate computation results to their neighbors during the signature verification, a large number of sensor nodes can accelerate their signature verification process significantly. When applying our faster signature verification technique to the broadcast authentication in a 4×4 grid-based WSN, a quantitative performance analysis shows that our scheme needs 17.7%~34.5% less energy and runs about 50% faster than the traditional signature verification method.

As the next evolutionary step in digital communication systems, mobile ad hoc networks (MANETs) and their specialization like wireless sensor networks (WSNs) have been attracting much interest in both research and industry communities. In MANETs, network nodes can come together and form a network without depending on any pre-existing infrastructure and human intervention. Unfortunately, the salient characteristics of MANETs, in particular the absence of infrastructure and the constrained resources of mobile devices, present enormous challenges when designing security mechanisms in this environment. Without necessary measures, wireless communications are easy to be intercepted and activities of users can be easily traced. This thesis presents our solutions for two important aspects of securing MANETs, namely efficient key management protocols and fast implementations of cryptographic primitives on constrained devices. Due to the tight cost and constrained resources of high-volume mobile devices used in MANETs, it is desirable to employ lightweight and specialized cryptographic primitives for many security applications. Motivated by the design of the well-known Enigma machine, we present a novel ultra-lightweight cryptographic algorithm, referred to as Hummingbird, for resource-constrained devices. Hummingbird can provide the designed security with small block size and is resistant to the most common attacks such as linear and differential cryptanalysis. Furthermore, we also present efficient software implementations of Hummingbird on 4-, 8- and 16-bit microcontrollers from Atmel and Texas Instruments as well as efficient hardware implementations on the low-cost field programmable gate arrays (FPGAs) from Xilinx, respectively. Our experimental results show that after a system initialization phase Hummingbird can achieve up to 147 and 4.7 times faster throughput for a size-optimized and a speed-optimized software implementation, respectively, when compared to the state-of-the-art ultra-lightweight block cipher PRESENT on the similar platforms. In addition, the speed optimized Hummingbird encryption core can achieve a throughput of 160.4 Mbps and the area optimized encryption core only occupies 253 slices on a Spartan-3 XC3S200 FPGA device. Bilinear pairings on the Jacobians of (hyper-)elliptic curves have received considerable attention as a building block for constructing cryptographic schemes in MANETs with new and novel properties. Motivated by the work of Scott, we investigate how to use efficiently computable automorphisms to speed up pairing computations on two families of non-supersingular genus 2 hyperelliptic curves over prime fields. Our findings lead to new variants of Miller's algorithm in which the length of the main loop can be up to 4 times shorter than that of the original Miller's algorithm in the best case. We also generalize Chatterjee et al.'s idea of encapsulating the computation of the line function with the group operations to genus 2 hyperelliptic curves, and derive new explicit formulae for the group operations in projective and new coordinates in the context of pairing computations. Efficient software implementation of computing the Tate pairing on both a supersingular and a non-supersingular genus 2 curve with the same embedding degree of k = 4 is investigated. Combining the new algorithm with known optimization techniques, we show that pairing computations on non-supersingular genus 2 curves over prime fields use up to 55.8% fewer field operations and run about 10% faster than supersingular genus 2 curves for the same security level. As an important part of a key management mechanism, efficient key revocation protocol, which revokes the cryptographic keys of malicious nodes and isolates them from the network, is crucial for the security and robustness of MANETs. We propose a novel self-organized key revocation scheme for MANETs based on the Dirichlet multinomial model and identity-based cryptography. Firmly rooted in statistics, our key revocation scheme provides a theoretically sound basis for nodes analyzing and predicting peers' behavior based on their own observations and other nodes' reports. Considering the difference of malicious behaviors, we proposed to classify the nodes' behavior into three categories, namely good behavior, suspicious behavior and malicious behavior. Each node in the network keeps track of three categories of behavior and updates its knowledge about other nodes' behavior with 3-dimension Dirichlet distribution. Based on its own analysis, each node is able to protect itself from malicious attacks by either revoking the keys of the nodes with malicious behavior or ceasing the communication with the nodes showing suspicious behavior for some time. The attack-resistant properties of the resulting scheme against false accusation attacks launched by independent and collusive adversaries are also analyzed through extensive simulations. In WSNs, broadcast authentication is a crucial security mechanism that allows a multitude of legitimate users to join in and disseminate messages into the networks in a dynamic and authenticated way. During the past few years, several public-key based multi-user broadcast authentication schemes have been proposed in the literature to achieve immediate authentication and to address the security vulnerability intrinsic to μTESLA-like schemes. Unfortunately, the relatively slow signature verification in signature-based broadcast authentication has also incurred a series of problems such as high energy consumption and long verification delay. We propose an efficient technique to accelerate the signature verification in WSNs through the cooperation among sensor nodes. By allowing some sensor nodes to release the intermediate computation results to their neighbors during the signature verification, a large number of sensor nodes can accelerate their signature verification process significantly. When applying our faster signature verification technique to the broadcast authentication in a 4×4 grid-based WSN, a quantitative performance analysis shows that our scheme needs 17.7%~34.5% less energy and runs about 50% faster than the traditional signature verification method.

In the present study syngas-air diffusion flames are simulated using LES with artificial neural network (ANN) based chemical kinetics modeling and the results are compared with previous direct numerical simulation (DNS) study, which exhibits significant extinction-reignition and forms a challenging problem for ANN. The objective is to obtain speed-up in chemistry computation while still having the accuracy of stiff ODE solver. The ANN methodology is used in two ways: 1) to compute the instantaneous source term in the linear eddy mixing (LEM) subgrid combustion model used within LES framework, i.e., laminar-ANN used within LEMLES framework (LANN-LEMLES), and 2) to compute the filtered source terms directly within the LES framework, i.e., turbulent-ANN used within LES (TANN-LES), which further dicreases the computational speed. A thermo-chemical database is generated from a standalone one-dimensional LEM simulation and used to train the LANN for species source terms on grid-size of Kolmogorov scale. To train the TANN coefficients the thermo-chemical database from the standalone LEM simulation is filtered over the LES grid-size and then used for training. To evaluate the performance of the TANN methodology, the low Re test case is simulated with direct integration for chemical kinetics modeling in LEM subgrid combustion model within the LES framework (DI-LEMLES), LANN-LEMLES andTANN-LES. The TANN is generated for a low range of Ret in order to simulate the specific test case. The conditional statistics and pdfs of key scalars and the temporal evolution of the temperature and scalar dissipation rates are compared with the data extracted from DNS. Results show that the TANN-LES methodology can capture the extinction-reignition physics with reasonable accuracy compared to the DNS. Another TANN is generated for a high range of Ret expected to simulate test cases with different Re and a range of grid resolutions. The flame structure and the scalar dissipation rate statistics are analyzed to investigate success of the same TANN in simulating a range of test cases. Results show that the TANN-LES using TANN generated fora large range of Ret is capable of capturing the extinction-reignition physics with a very little loss of accuracy compared to the TANN-LES using TANN generated for the specific test case. The speed-up obtained by TANN-LES is significant compared to DI-LEMLES and LANN-LEMLES.

Over recent years, the study of industrial districts, and inter-organizational relations has become a major theme of interest in network research. Theories characterized by an increased inter-relatedness between heterogeneous actors and knowledge fields point to a new form of inter-organizational relationship development. This is basicly based on the idea of creating trust between firms to increase their chances of success and to keep pace with the development of all relevant technologies. In this thesis, we present some data from a research project we have conducted in OSTIM industrial district, Ankara, Turkey. First, we present the theoretical perspectives which appear relevant to such investigation, and which aims at developing a better a network model of the inter-organizational relations of district firms, as well as trust, informal contracts and centrality issues, particularly as regards technological innovation and technology transfer of firms, respectively. Moreover, the evidence presented in this thesis is unequivocal in noting that long term inter-organizational relations and trust may be a necessary and a sufficent condition for a small and medium sized enterprise (SME) to take its place in the center of a complex web of inter-organizational relations as seen in an industrial district.

Diploma thesis describes a system for automatic detection of buttons from a screen photo.The system is used together with a robotic arm and a camera to detect buttons on the screens of embedded devices. After detecting buttons on the screen, the algorithm commands the robotic arm to click on the position of the detected button. The algorithm creates a navigation map in which all screens of the device are visible by systematically clicking through all buttons on all screens. For each screen, the positions of the detected buttons and the destination to which the screen points are stored.

No description available.