Дисертації з теми "CA Networks"
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Weitzen, Christopher James. "Service differentiation using managed sleep in CSMA/CA networks." Winston-Salem, NC : Wake Forest University, 2009. http://dspace.zsr.wfu.edu/jspui/handle/10339/44746.
Повний текст джерелаMedapalli, Kameswara Rao. "Design, analysis and optimization of CSMA/CA based wireless networks /." May be available electronically:, 2006. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Повний текст джерелаMawlawi, Baher. "Random access for dense networks : Design and Analysis of Multiband CSMA/CA." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0112/document.
Повний текст джерелаOpportunistic protocols are promising candidates for future wireless systems dedicated to machine to machine (M2M) communication. Such protocols are usually based on a random access with simple techniques of medium sensing and deferring to reduce collisions while avoiding the use of complex schedulers. Among different protocols, Carrier sense multiple access/collision avoidance with a Request-To-Send/Clear-To-Send (CSMA/CA-RTS/CTS) is an opportunistic protocol which could be adopted for M2M scenarios. Such approach is efficient to avoid collisions between data packets but in a very dense network, the random access used to send the RTS suffers itself from a high probability of collision which degrades the performance. In order to mitigate this effect, RTS collisions should be reduced. This thesis proposes to address this issue by splitting the common channel in sub-channels for transmitting the RTS messages. While the common channel is used as a whole for data transmission. Multiple nodes can then contend in time and frequency for these RTS sub-channels, thereby reducing RTS collisions and increasing overall efficiency. In this work, we thus derive a complete protocol solution relying on CSMA/CA - RTS/CTS multiplexing a multi-channel configuration for RTS messages and a unique channel for data transmission. An enhanced version based on users scheduling is integrated as well. In this thesis, the proposed protocol is investigated from a joint PHY-MAC point of view. This strategy is shown to provide better system performance particularly for loaded networks. An accurate analytical model derived as a straightforward extension of the Bianchi model is analyzed and validated by simulations. Performance in terms of saturation throughput, transmission delay and packet drop probability is discussed
Wu, Jingqi. "Cooperative Jamming in Wireless Networks - Turning Attacks into Privacy Protection." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/885.
Повний текст джерелаLuan, Hao. "Performance Analysis of Integrated Multihop Heterogeneous Networks." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1273167630.
Повний текст джерелаFreund, Kyle P. "Lithic Technology and Obsidian Exchange Networks in Bronze Age Sardinia, Italy (ca. 1600-850 B.C.)." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3429.
Повний текст джерелаMoslehi, Farhood. "Simulation of the MAC Portion of IEEE 802.11 and Bursts of Errors for Wireless Data Networks." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36936.
Повний текст джерелаMaster of Science
Fu, Guoxing. "Structure Based Study of CA SPASE-3 and D-Arginine Dehydrogenase." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/biology_diss/124.
Повний текст джерелаDao, Trong Nghia Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Modelling 802.11 networks for multimedia applications." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2008. http://handle.unsw.edu.au/1959.4/41222.
Повний текст джерелаShaw, Samuel. "Effects of Mass Wasting and Uplift on Fluvial Networks within the Central Franciscan Melange Complex - Eel River, CA." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23145.
Повний текст джерелаRAJSHIVA, KIRTIMAAN. "PERFORMANCE ENHANCEMENTS FOR Ad Hoc NETWORKS USING MOBILITY-LOCATION INFORMATION." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1132338696.
Повний текст джерелаAli, Mohamad Jaafar. "Wireless body area networks : co-channel interference mitigation & avoidance." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCB252/document.
Повний текст джерелаA Wireless Body Area Network (WBAN) is a short-range network that consists of a coordinator (Crd) and a collection of low-power sensors that can be implanted in or attached to the human body. Basically, WBANs can provide real-time patient monitoring and serve in various applications such as ubiquitous health-care, consumer electronics, military, sports, etc. [1]. As the license-free 2.4 GHz ISM band is widely used among WBANs and across other wireless technologies, the fundamental problem is to mitigate the resulting co-channel interference. Other serious problems are to extend the network lifetime and to ensure reliable transmission within WBANs, which is an urgent requirement for health-care applications. Therefore, in this thesis, we conduct a systematic research on a few number of research problems related to radio co-channel interference, energy consumption, and network reliability. Specifically, we address the following problems ranging from theoretical modeling and analysis to practical protocol design: • Intra-WBAN interference mitigation and avoidance • Cooperative inter-WBAN interference mitigation and avoidance • Non-cooperative inter-WBAN interference mitigation and avoidance • Interference mitigation and avoidance in WBANs with IoT Firstly, to mitigate the intra-WBAN interference, we present two mechanisms for a WBAN. The first is called CSMA to Flexible TDMA combination for Interference Mitigation, namely, CFTIM, which dynamically allocates time-slots and stable channels to lower the intra-WBAN interference. The second is called Interference Avoidance Algorithm, namely IAA that dynamically adjusts the superframe length and limits the number of channels to 2 to lower the intra-WBAN interference and save energy. Theoretically, we derive a probabilistic model that proves the SINR outage probability is lowered. Simulation results demonstrate the effectiveness and the efficiency of CFTIM and IAA in terms of lowering the probability of interference, extending network lifetime, improving throughput and reliability. Secondly, we address the problem of interference among cooperative WBANs through using orthogonal codes. Motivated by distributed time provisioning supported in IEEE 802.15.6 standard [2], we propose two schemes. The first is called Distributed Time Correlation Reference, namely, DTRC that provides each WBAN with the knowledge about which superframes overlap with each other. The second is called Orthogonal Code Allocation Algorithm for Interference Mitigation, namely, OCAIM, that allocates orthogonal codes to interfering sensors belonging to sensor interference lists (SILs), which are generated based on the exchange of power-based information among WBANs. Mathematically, we derive the successful and collision probabilities of frames transmissions. Extensive simulations are conducted and the results demonstrate that OCAIM can diminish the interference, improve the throughput and save the power resource. Thirdly, we address the problem of co-channel interference among non-cooperative WBANs through time-slot and channel hopping. Specifically, we propose two schemes that are based on Latin rectangles. The first is called Distributed Algorithm for Interference mitigation using Latin rectangles, namely, DAIL that allocates a single channel to a timeslot combination to each sensor to diminish inter-WBAN interference and to yield better schedules of the medium access within each WBAN. The second is called Channel Hopping for Interference Mitigation, namely, CHIM, which generates a predictable interference free transmission schedule for all sensors within a WBAN. CHIM applies the channel switching only when a sensor experiences interference to save the power resource. Furthermore, we present an analytical model that derives bounds on collision probability and throughput for sensors transmissions. (...)
Sánchez, Garache Marvin. "Multihop Wireless Networks with Advanced Antenna Systems : An Alternative for Rural Communication." Doctoral thesis, KTH, Kommunikationssystem, CoS, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4755.
Повний текст джерелаQC 20100908
Graham, Emily E. "The patronage of the Spiritual Franciscans : the roles of the Orsini and Colonna cardinals, key lay patrons and their patronage networks." Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/904.
Повний текст джерелаAldabbas, Hamza. "Securing data dissemination in vehicular ad hoc networks." Thesis, De Montfort University, 2012. http://hdl.handle.net/2086/7987.
Повний текст джерелаGhasemi, Saeed, and Moussa Haisam El-hajj. "Fair Medium Access Control Mechanism Reducing Throughput Degradation in IEEE 802.11s Wireless Mesh Networks." Thesis, Malmö högskola, Fakulteten för teknik och samhälle (TS), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-20052.
Повний текст джерелаThis thesis rapport deals with the performance issues of the newly standardized Wireless mesh protocol (IEEE 802.11s). In this thesis, we work on improving the conditions that results in throughput degradation in a chain of nodes topology. The mesh standard is very promising with many advantages for both IoT systems and home wireless networks.We work on the issue of unfairness when CSMA/CA is applied, which causes throughput degradation due to packet loss and indicates starvation. We analyze the implication of the Collision Avoidance (CA) mechanism and propose a replacement for the CA that is both fair and able to maintain collision avoidance. We implement this in a simulator and the result shows significantly higher end-to-end throughput compared to the original CSMA/CA and no packet loss due to buffer overflow.
Hotta, Carlos Takeshi. "Positioning Ca²⁺ within the circadian signalling network." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604252.
Повний текст джерелаTsertou, Athanasia. "Modelling interference in a CSMA/CA wireless network." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/14589.
Повний текст джерелаBenson, Kirk C. "Modeling data encapsulation and a communication network for the National Training Center, Fort Irwin, CA." Thesis, Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/8689.
Повний текст джерелаThe National Training Center (NTC) located at Fort Irwin, California provides the U.S. Army sole replication of a desert combat environment. The NTC provides U.S. Army brigade size heavy forces both realistic training scenarios and an accurate record of mission execution. The primary emphasis of this research is to develop the methodology for modeling both data encapsulation and transmission via a fiber optic cable for the NTC. To capitalize on technological advances, the NTC requires a relational database for data encapsulation. The database structure in this effort efficiently stores Range Data Management System (RDMS) and Observer/Controller (OC) data input. The NTC also requires a mathematical modeling (network) tool with the capability of flexible analysis of a modular fiber optic cable system. The NTC Route Optimizer program developed in this effort provides a tool for rapid manipulation of design factors with immediate graphical and numerical feedback. Additionally, the reader is given methods to design future upgrades to the database and change specifications of the fiber optic cable system. This allows the reader to manipulate technology for specific goals instead of receiving transparent improvements that are disconnected
Vinod, Kalkotwar Divya. "Wireless Body Area Network for Patient Monitoring in Hospitals." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-206121.
Повний текст джерелаOliveira, Hércules Araújo. "Rede híbrida de distribuição de energia em CC e CA como solução alternativa para microrredes isoladas." Universidade Federal do Maranhão, 2017. http://tedebc.ufma.br:8080/jspui/handle/tede/1408.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ)
This work proposes a topology of isolated microgrids with hybrid network (part in DC and part in AC) of electric power distribution. This topology can serve as an alternative model to the conventional AC distribution network model for the electrical service of isolated communities. The topology consists of using a main system of DC power distribution and subsystems with an AC distribution. DC/AC converters are strategically distributed along the DC main network, forming AC subsystems, in order to serve a certain number of consumers with AC loads. Although there are loads that can be fed in DC, this is not a reality for household loads, which are basically AC powered. Thus, the interest of this work is to evaluate the possible advantages of this topology over the conventional microrredes with distribution network in low voltage in AC. In this contexto, the analysis parameters to be studied are: the increasing the extension of the distribution network without the need to use transformers, electric conductors with larger cross sections or distributed generation; the efficiency in the distribution of energy, evaluating the losses, and the reduction of implantation and operation costs. In order to compare the microgrid with hybrid distribution network, an isolated microgrid with purely CA distribution network was adopted as reference: the microgrid with solar-wind generation of Lençóis Island, located in the northeast of Brazil, which has been in operation since July 2008.
Este trabalho propõe uma topologia de microrredes isoladas com rede híbrida (parte em CC e parte em CA) de distribuição de energia elétrica. Essa topologia pode servir como modelo alternativo ao modelo convencional de rede de distribuição de energia totalmente em CA para o atendimento elétrico de comunidades isoladas. A topologia consiste em utilizar um sistema tronco de distribuição de energia em CC e de subsistemas com distribuição CA. Conversores CC/CA são distribuídos estrategicamente ao longo da rede tronco CC, formando subsistemas CA, com a finalidade de atender determinado número de consumidores com carga em CA. Apesar de existirem cargas que podem ser alimentadas em CC, essa não é uma realidade para as cargas de uso doméstico, que basicamente são alimentadas em CA. Assim, o interesse deste trabalho é avaliar as possíveis vantagens dessa topologia sobre as convencionais microrredes com rede de distribuição em baixa tensão em CA. Neste contexto, os parâmetros de análise a serem estudados são o aumento da extensão da rede de distribuição sem a necessidade de se utilizar transformadores, condutores elétricos com seções transversais maiores ou geração distribuída; a eficiência na distribuição de energia, avaliando as perdas, e a redução de custos de implantação e operação. Para se comparar a microrrede com rede de distribuição híbrida, adotouse como referência uma microrrede isolada com rede de distribuição somente CA: a microrrede com geração eólica-solar da Ilha de Lençóis está localizada no nordeste do Brasil, a qual está em operação desde julho de 2008.
Sadli, Rahmad. "Étude et développement d'un dispositif routier d'anticollision basé sur un radar ultra large bande pour la détection et l'identification notamment des usagers vulnérables." Thesis, Valenciennes, 2019. http://www.theses.fr/2019VALE0005.
Повний текст джерелаIn this thesis work, we focused on the study and development of a system identification using UWB-Ultra-Wide-Band short range radar to detect the objects and particularly the vulnerable road users (VRUs) that have low RCS-Radar Cross Section- such as cyclist and pedestrian. This work is composed of two stages i.e. detection and recognition. In the first approach of detection stage, we have proposed and studied a robust UWB radar detector that works on one dimension 1-D radar data ( A-scan). It relies on a combination of Higher Order Statistics (HOS) and the well-known CA-CFAR (Cell-Averaging Constant False Alarm Rate) detector. This combination is performed by firstly applying the HOS to the received radar signal in order to suppress the noise. After eliminating the noise of the received radar signal, we apply the CA-CFAR detector. By doing this combination, we finally have an UWB radar detector which is robust against the noise and works with the adaptive threshold. In order to enhance the detection performance, we have evaluated the approach of using two dimensions 2-D (B-Scan) radar data. In this 2-D radar approach, we proposed a new method of noise suppression, which works on this B-Scan data. The proposed method is a combination of WSD (Wavelet Shrinkage Denoising) and HOS. To evaluate the performance of this method, we performed a comparative study with the other noise removal methods in literature including Principal Component Analysis (PCA), Singular Value Decomposition (SVD), WSD and HOS. The Signal-to-Noise Ratio (SNR) of the final result has been computed to compare the effectiveness of individual noise removal techniques. It is observed that a combination of WSD and HOS has better capability to remove the noise compared to that of the other applied techniques in the literature; especially it is found that it allows to distinguish efficiency the pedestrian and cyclist over the noise and clutters whereas other techniques are not showing significant result. In the recognition phase, we have exploited the data from the two approaches 1-D and 2-D, obtained from the detection method. In the first 1-D approach, Support Vector Machines (SVM) and Deep Belief Networks (DBN) have been used and evaluated to identify the target based on the radar signature. The results show that the SVM gives good performances for the proposed system where the total recognition accuracy rate could achieve up to 96,24%. In the second approach of this 1-D radar data, the performance of several DBN architectures compose of different layers have been evaluated and compared. We realised that the DBN architecture with four hidden layers performs better than those of with two or three hidden layers. The results show also that this architecture achieves up to 97.80% of accuracy. This result also proves that the performance of DBN is better than that of SVM (96.24%) in the case of UWB radar target recognition system using 1-D radar signature. In the 2-D approach, the Convolutional Neural Network (CNN) has been exploited and evaluated. In this work, we have proposed and investigated three CNN architectures. The first architecture is the modified of Alexnet model, the second is an architecture with three convolutional layers and one fully connected layer, and the third is an architecture with five convolutional layers and two fully connected layers. The performance of these proposed architectures have been evaluated and compared. We found that the third architecture has a good performance where it achieves up to 99.59% of accuracy. Finally, we compared the performances obtained using CNN, DBN and SVM. The results show that CNN gives a better result in terms of accuracy compared to that of DBN and SVM. It allows to classify correctly the UWB radar targets like cyclist and pedestrian
Caracas, João Victor Mapurunga. "Avaliação das Estratégias de Controle e Projeto de Inversores para Conexão de Fontes Fotovoltaicas à Rede CA." Universidade Federal do Maranhão, 2013. http://tedebc.ufma.br:8080/jspui/handle/tede/500.
Повний текст джерелаConselho Nacional de Desenvolvimento Científico e Tecnológico
Today's highly eletricity dependent society together with the scarcity of conventional energy sources and magnitude of environmental problems brought by them, has raised the level of importance of renewable energy sources such as photovoltaic energy. However, it is necessary to develop new techniques of PV panel production and electronic converters required in their use, as well as the dissemination of such technologies in Brazil. This work contributes to the systematic design of an inverter for photovoltaic systems connected to the mains. The key techniques needed to control these systems are described and analyzed within a common base. Furthermore, this paper describes the hardware design of an inverter for connecting PV panels to the AC mains, allowing an overview of all the steps required for the design of a PV inverter. A new methodology for the design of current controllers for current injection into the grid is presented and the advantages of the proportional resonant controller are shown. This work resulted in a functional inverter with commercially viable features, a total current harmonic distortion of 2.03%, maximum power point operation and in conformance to international regulatory standards.
A dependência quase que imperativa da sociedade atual à energia elétrica aliada à escassez das fontes de energia convencionais e à magnitude dos problemas socioambientais trazidos por elas, tem elevado o nível de importância de fontes renováveis de energia, tais como a fotovoltaica. Entretanto, ainda é necessário o desenvolvimento de novas técnicas de produção de painéis FV e dos conversores eletrônicos necessários ao seu uso, bem como a disseminação dessas tecnologias no Brasil. Este trabalho contribui com a sistematização do projeto de um inversor para sistemas fotovoltaicos conectados à rede CA. São descritas e analisadas, dentro de uma base comum, as principais técnicas de controle necessárias a estes sistemas. Além disso, esse trabalho descreve o projeto de hardware de um inversor para conexão entre painéis FV e a rede CA, possibilitando uma visão global de todas as etapas necessárias para o projeto de um inversor fotovoltaico. É apresentada uma nova metodologia para o projeto dos controladores da corrente injetada na rede e mostra-se as vantagens do controlador proporcional ressonante. Tem-se como resultado um inversor funcional, com características comercialmente viáveis, com uma taxa de distorção harmônica de corrente de 2,03%, funcionamento no ponto de máxima potência e adequado às normas regulatórias internacionais.
Olofsson, Sven. "Till ömsesidig nytta : Entreprenörer, framgång och sociala relationer i centrala Jämtland ca. 1810-1850." Doctoral thesis, Uppsala universitet, Historiska institutionen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-158684.
Повний текст джерелаReichert, Melanie. "Malta im phönizischen Handelsnetzwerk zwischen 1000 und 500 v. Chr. Einflüsse auf das Keramikrepertoire und die Kleinfunde." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22912.
Повний текст джерелаMalta played an important role in history because of its specific location right in the middle of the Mediterranean Sea. The Phoenicians, a seafaring nation who is originated at today’s Lebanon coast, did use the island for strategic and economic purpose. That dissertation deals with the Phoenician epoch on Malta. In special analyzing focus stands the period between 1000 and 500 B.C. The study focuses the ceramic repertoire and the small finds which are classified into that period. The first chapter consider the current research literature concerning the Phoenicians. Identity, language and the origin of the inhabitants of the nowadays Lebanon coast are in special interest. The next chapter is leading to the research literature concerning the Phoenicians on Malta. Amongst others it deals with questions about chronology, the ceramic repertoire, the sanctuary of Tas-Silġ and the erstwhile phoenician settlement. The main chapter of this study considers a systematic analysis of the ceramic and the small finds. An analysis of every specific shape of the ceramic items and the small finds is made. 680 objects have been observed in total. 554 ceramic objects and 126 small finds. The last chapter deals with the results of the study. Especially emphasized is the hypothesis, that the early phoenician settlers were creating an “island-network” between Sicily, Sardinia, North Africa and Malta. For proving this thesis much better, comparison models were used which comes from the antiquity and from the middle ages.
Klasson, Sebastian, and Nina Lindström. "Longitudinal analysis of the certificate chains of big tech company domains." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-178396.
Повний текст джерелаBednařík, Martin. "Návrh paketového analyzátoru pro bezdrátové senzorové sítě založené na standardu IEEE 802.15.4." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-218974.
Повний текст джерелаMonteiro, Thiago Costa. "Proposta de modelo e método para determinação dos parâmetros de transformadores operando em saturação." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-31052011-154602/.
Повний текст джерелаSeveral power electronics based equipments are connected to the alternating current network through transformers, which perform galvanic insulation, voltage increasing/lowering, etc. These transformers may experience saturation under transitory conditions (inrush), or when its converter imposes non-zero average voltage. Such problem is commonly treated in the converter\'s control loops, but the tuning of these loops in a computer simulation environment requires a transformer model that represents adequately the ferromagnetic core saturation effect. The current work proposes a computer simulation model that adequately describes the operation of the transformer at deep saturation, suitable for design of power electronics applications with single phase transformers connected to power inverter. Additionally, an experimental method for determining its core saturation characteristic is demonstrated. This method does not require previous knowledge of the core\'s constructive parameters. Simulation and experimental results are presented to confirm the validity of the model and the method.
Panunzio, Paulo Armando [UNESP]. "Proposta de equipamento de conexão à rede para a utilização da geração de energia solar em consumidores de pequeno e médio porte." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/136277.
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A proposta dessa Tese é o projeto e desenvolvimento de um sistema de fornecimento de energia elétrica conectada à rede sem a utilização de circuitos eletrônicos complexos. O sistema eletroeletrônico convencional utiliza um inversor de frequência que transfere a potência ativa do nível de tensão e corrente CC para o nível compatível com a rede elétrica CA em frequência, tensão e sincronismo de fases. Já o desenvolvimento do projeto teve como parte experimental a utilização de indutores adequados com valores variáveis de 200 mH a 500 mH entre os painéis fotovoltaicos e a rede convencional. A tensão e a corrente máxima de CC foi de 29,6 V e a máxima possível foi de 20 amperes. Utilizou-se do princípio do casamento de impedâncias entre o painel fotovoltaico e o sistema de fornecimento de energia CA. Assim o painel fotovoltaico fornece somente potência ativa para a rede não interferindo no sincronismo. Na onda de tensão e corrente CA há uma pequena alteração no nível CA em relação a simetria do eixo dos tempos, dentro dos limites previstos para a rede convencional de energia. Logo evidencia-se o fornecimento de potência ativa para a rede CA. Os resultados obtidos permitiram inserção na rede de cerca de 10% da potência ativa dos painéis fotovoltaicos, com a otimização dos valores dos indutores, ocorrendo a transferência de potência ativa dos painéis fotovoltaicos para a rede convencional de energia CA.
The purpose of this thesis is the design and development of a delivery system of electricity connected to the network without the use of complex electronic circuits. The electronics system uses a frequency inverter that transfers the active power level voltage and DC current to the level compatible with the mains AC frequency, voltage and phase synchronization. But the project was to develop experimental part the use of suitable inductors with variable values of 200 mH to 500 mH between the PV panels and the conventional network. The maximum current was 20 amperes. We used the principle of impedance matching between the photovoltaic panel and the power supply system CA. So the photovoltaic panel supplies only active power to the grid not interfering with the timing. In the wave of AC voltage and current for a small change in CA level against the symmetry axis of time. Logo is evident in the supply of active power to the grid CA. The results allowed inclusion in the network of about 10% of the active power of photovoltaic panels by optimizing the values of the inductors for the occurrence of power transfer of conventional photovoltaic panels for energy occurs CA.
Doležal, Jan. "Minimalizace vlivu rušení na bezdrátovou síť." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217521.
Повний текст джерелаYu-Liang, Kuo. "QoS Guarantee in CSMA/CA-Based Wireless Mesh Networks." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2501200717083800.
Повний текст джерелаKuo, Yu-Liang, and 郭育良. "QoS Guarantee in CSMA/CA-Based Wireless Mesh Networks." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/82619907737855547528.
Повний текст джерела國立臺灣大學
資訊工程學研究所
95
Recently, CAMA/CA-based wireless mesh networking technology has received much attention, because they can provide metropolitan-scale wireless broadband Internet access networks, and enable a cost-effective scalable deployment with less wired lines. A wireless mesh network consists of several mesh backhaul networks where any two mesh nodes in a mesh backhaul network communicate with each other by wireless radio in a multi-hop manner. Some mesh nodes also act as gateways for connecting the mesh backhaul network to the Internet. Each mesh node in a mesh backhaul network forms its own mesh client network, where its associated mobile users can use it as an access point to communicate with other users or access Internet services through the mesh backhaul network. With the diversity of applications evolved until today, in addition to traditional best effort applications, multimedia applications with different quality requirements will be available in the near future. In order to provide quality delivery to multimedia applications, it is imperative that wireless mesh networks have to support quality-of-service (QoS) so that their required resource can be guaranteed. Thus far, providing QoS in a CAMA/CA-based mesh backhaul network is still a challenge, due to the spatial contention among shared wireless medium. In this dissertation, we focus on the QoS routing problems in a mesh backhaul network with the following two aspects. (P1) QoS routing with bandwidth requirement. (P2) QoS routing with maximum bandwidth. On the other hand, in a CSMA/CA-based mesh client network, a performance anomaly problem will incur when there are multiple applications transmitted with different channel bit rates. The anomaly problem arises because the basic CSMA/CA channel access method guarantees that the long-term channel access probabilities of the mobile devices transmitting at different data rates are equivalent to one another, and hence the long-term channel occupancy time for those devices transmitting at a lower data rate will be larger than those devices transmitting at a higher rate. When one device transmitting at a lower data rate captures the channel, it will last for a long time and hence penalize the total throughput of those devices transmitting at a higher data rate. Since the problem will bring about great impact on the quality transmission in a mesh client network, the following problem is identified. (P3) A throughput optimization method when multi-rate traffic is presented. In this dissertation, one of objectives is to study the QoS routing problems in the CSMA/CA-based mesh backhaul network such that the required resource of multimedia applications can be attained. The other objective is to alleviate the impact of the performance anomaly in the CSMA/CA-based mesh client network by maximizing the total throughput. To evaluate their performance, extensive experiments shall be carried out.
Yang, Wun-Cin, and 楊文欽. "Design of CSMA/CA Based Wireless Networks Providing Differentiated Services." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/20047714849541743970.
Повний текст джерела國立暨南國際大學
電機工程學系
100
Wireless LANs have been part of our daily life thanks to the development of wireless technologies. However, the original design of IEEE 802.11 can not provide a good service in a large network. The new IEEE 802.11 standard defines EDCA for differentiated services, where each AC queue operates independently to contend for the wireless channel. When number of station increases, the collision probability increases dramatically. Furthermore, the lower priority ACs may starves at heavy load situations. In an infrastructure WLAN, the AP is the bottleneck for downlink packets because the AP needs to contend with numerous stations, resulting in asymmetric throughputs between downlink and uplink. In order to mitigate the above mentioned problems. In this thesis, we propose a new MAC architecture including the new queue management module and the super mode. In addition, a contention-free MAC is also investigated to provide a collision-free wireless access way instead of the traditional random access manner. By the scheduler of the queue management module, we can mix different AC packets for a given TXOP duration. With the super mode, the AP can grant the wireless channel without contention. Simulation results show that, the proposed system can balance the uplink and downlink traffic, reduces high collision probability, and improves the overall capacity.
Karim, Shafiqul. "Throughput Management for CSMA/CA Networks : IEEE 802.11e Wireless LAN." Thesis, 2012. http://hdl.handle.net/2440/80596.
Повний текст джерелаThesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2012
"An adaptive approach on the carrier sensing range of CSMA/CA multi-hop wireless networks." 2008. http://library.cuhk.edu.hk/record=b5893689.
Повний текст джерелаThesis (M.Phil.)--Chinese University of Hong Kong, 2008.
Includes bibliographical references (leaves 62-65).
Abstracts in English and Chinese.
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Multihop Ad Hoc Wireless Networks --- p.1
Chapter 1.1.1 --- Introduction to Multihop Ad Hoc Networks --- p.2
Chapter 1.1.2 --- Scalability of Ad Hoc Wireless Networks --- p.3
Chapter 1.2 --- Hidden Terminal Problem --- p.3
Chapter 1.3 --- Exposed Terminal Problem --- p.5
Chapter 1.4 --- Overview of the Thesis --- p.6
Chapter 2 --- Background --- p.8
Chapter 2.1 --- MAC Protocols for Wireless Networks --- p.8
Chapter 2.1.1 --- Aloha --- p.8
Chapter 2.1.2 --- CSMA/CA --- p.9
Chapter 2.1.3 --- IEEE 802.11 DCF Standard --- p.10
Chapter 2.2 --- Related Work --- p.12
Chapter 2.2.1 --- Schemes for Hidden Node Problem --- p.12
Chapter 2.2.2 --- Schemes for Exposed Node Problem --- p.13
Chapter 2.3 --- Tradeoff between Hidden and Exposed Nodes --- p.14
Chapter 2.4 --- The Effect of Carrier Sensing Range --- p.17
Chapter 3 --- Analysis on Carrier Sensing Range --- p.18
Chapter 3.1 --- Analysis Model --- p.18
Chapter 3.1.1 --- Terminal Configurations --- p.18
Chapter 3.1.2 --- Timing/Packet Parameters --- p.19
Chapter 3.1.3 --- Protocol Approximation --- p.20
Chapter 3.1.4 --- Throughput Measurement --- p.21
Chapter 3.2 --- Derivation of Throughput --- p.21
Chapter 3.2.1 --- Channel Modeling --- p.22
Chapter 3.2.2 --- Actual Transmission Rate --- p.24
Chapter 3.2.3 --- Case One --- p.24
Chapter 3.2.4 --- Case Two --- p.26
Chapter 3.2.5 --- Mathematical Form of Throughput --- p.28
Chapter 3.2.6 --- Analysis Results --- p.30
Chapter 3.3 --- Implications --- p.31
Chapter 3.3.1 --- Value of Sensing Range in CSMA/CA --- p.31
Chapter 3.3.2 --- Need for New MAC Protocols --- p.32
Chapter 4 --- MAC Protocols by Congestion Control --- p.34
Chapter 4.1 --- Motivations and Principles --- p.34
Chapter 4.1.1 --- Balancing Hidden and Exposed Nodes --- p.35
Chapter 4.1.2 --- Controlling Carrier Sensing Range --- p.36
Chapter 4.1.3 --- Non-homogenous Sensing Range --- p.36
Chapter 4.2 --- Algorithm Descriptions --- p.38
Chapter 4.2.1 --- Core Concept --- p.38
Chapter 4.2.2 --- LDMI Control Scheme --- p.40
Chapter 4.2.3 --- Tahoe Control Scheme --- p.41
Chapter 5 --- Simulation Analysis --- p.44
Chapter 5.1 --- Simulation Configurations --- p.44
Chapter 5.1.1 --- Geometric Burst Traffic Model --- p.45
Chapter 5.1.2 --- Network Topology --- p.46
Chapter 5.1.3 --- Simulation Parameters --- p.47
Chapter 5.2 --- Throughput Comparisons --- p.48
Chapter 5.3 --- Fairness Comparisons --- p.50
Chapter 5.3.1 --- Situation of Unfairness --- p.50
Chapter 5.3.2 --- Fairness Measurement --- p.52
Chapter 5.4 --- Convergence Comparisons --- p.54
Chapter 5.5 --- Summary of Performance Comparison --- p.55
Chapter 6 --- Conclusions --- p.56
Chapter A --- Categories of CSMA/CA --- p.58
Chapter A.1 --- 1-persistent CSMA/CA --- p.58
Chapter A.2 --- non-persistent CSMA/CA --- p.58
Chapter A.3 --- p-persistent CSMA/CA --- p.59
Chapter B --- Backoff Schemes --- p.60
Chapter B.1 --- Constant Window Backoff Scheme --- p.60
Chapter B.2 --- Geometric Backoff Scheme --- p.60
Chapter B.3 --- Binary Exponential Backoff Scheme --- p.61
Bibliography --- p.62
鄭維中. "Interplay of Spatial Reuse and Transmission Reliability in CSMA/CA-based Wireless Networks." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/j8ubr6.
Повний текст джерела國立交通大學
電信工程研究所
103
In CSMS/CA-based, multi-hop, multi-rate wireless ad-hoc networks, we can balance the interplay of spatial reuse and transmission reliability by dynamicly tuning carrier-sensing threshold (Tcs) according to environmental situations in order to reach the maximum network capacity. Lower carrier-sensing thresholds generally lead to larger carrier-sensing ranges (dcs), which ensure higher transmission reliability. In this manner, we actually increase the transmission reliability by reducing packet collisions due to mitigated interference produced by concurrent transmissions. However, the total network capacity suffers because of too preservative channel access attempts. On the other hand, higher carrier-sensing thresholds usaually result in smaller carrier-sensing ranges, which encourage better spatial reuse yet transmission collisions will happen more frequently due to potentially increased interference. Therefore, it is important to make adequate adjustments of carrier-sensing thresholds according to environmental conditions in a CSMA/CA-based wireless network. In this thesis, we address the above issue by proposing an adaptive mechanism to dynamicly adjust carrier-sensing thresholds used by wireless nodes in a distributed manner within reasonable computation time. Simulation results show that our proposed algorithm outperforms other implemented carrier-sensing tuning approaches in terms of aggregate network capacity.
Shrestha, Bharat. "Analysis of Hybrid CSMA/CA-TDMA Channel Access Schemes with Application to Wireless Sensor Networks." 2013. http://hdl.handle.net/1993/22284.
Повний текст джерелаLIU, YU-FU, and 劉祐甫. "Throughput Simulation of CSMA/CA Mechanism in Memory Impulse Channel for Power Line Communication Networks." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/279nsb.
Повний текст джерела國立臺北科技大學
電子工程系
107
In the previous study, [1] analyzed and simulated the throughput of DS CDMA/unslotted ALOHA networks with Markov Gaussian impulse noise. All previous research papers in CSMA/CA for power line communication (PLC) do not consider impulse noise in the physical (PHY) layer. The exception is [2], which considers CSMA/CA with Bernoulli-Gaussian impulse noise and do not consider queue effect in PLC. However, its impulse noise is memoryless. In this paper, we propose the throughput simulation of CSMA/CA with the Markov Gaussian impulse noise in PLC. The simulation results show that the throughput is higher due to the CSMA/CA mechanism compared to non-CDMA version of the previous ALOHA with Markov Gaussian impulse noise [1]. However, when the Gaussian noise/impulse noise ratio R is larger, the throughput decreases.
Zhuang, Xiang-Wei, and 莊翔瑋. "A Study on Combination of CSMA/CA and Non-Overlapped Spatial TDMA in Ad Hoc Networks." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/71555455347853257238.
Повний текст джерела國立高雄第一科技大學
電腦與通訊工程所
97
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) of IEEE 802.11 is a common access method of media access control (MAC). When the number of nodes running CSMA protocol is increased, the package collision probability becomes larger. It also causes total throughput of the network worse. In this study, Time Division Multiple Access (TDMA) assigns a slot to each node. And it is able to arrange the transmission order among nodes, and there is no collision. However, in TDMA, when there are few transmitting nodes, it causes total throughput become low, due to poor slot utilization. To overcome the weakness of CSMA/CA and TDMA, we propose a protocol, which groups ad hoc nodes into non-overlapped spatial clusters. Within a cluster, each node runs both CSMA/CA and Spatial TDMA to improve total throughput. Among clusters, CSMA/CA and AODV are adopted. Finally, we analyze the protocol, which is the combination of CSMA/CA and Spatial TDMA, using ns2.
Kao, Hsin-Yu, and 高欣毓. "Combining Simulated Annealing and Genetic Algorithm for Tuning Carrier-sensing Threshold in CSMA/CA-based Wireless Networks." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/35h43a.
Повний текст джерела國立交通大學
電信工程研究所
106
With the arising of Internet of Things (IoT) applications and the fast growing of wireless devices, the Internet has become more and more crowded. How to deploy the resources effectively and make the best use of wireless channel is an essential yet non-trivial problem. Generally, increasing the spatial reuse will decrease the channel reliability simultaneously. In CSMA/CA-based wireless networks, adjusting physical carrier sensing threshold is an effective way to influence the spatial reuse factor. Increasing carrier sensing threshold typically encourages a better spatial reuse, which also means a better networks capacity. However, too many simultaneous transmissions will incur a higher packet collision probability. In this paper, we propose to combine the Simulated Annealing and Genetic Algorithm to obtain a global network-wise carrier sensing threshold for throughput improvement. Our simulation results validate the efficacy of the proposed tuning approach.
Gao, J. L., J. Hu, Geyong Min, and L. Xu. "Analysis of the MAC protocol in low rate wireless personal area networks with bursty ON-OFF traffic." 2013. http://hdl.handle.net/10454/9655.
Повний текст джерелаSupported by the IEEE 802.15.4 standard, embedded sensor networks have become popular and been widely deployed in recent years. The IEEE 802.15.4 medium access control (MAC) protocol is uniquely designed to meet the desirable requirements of the low end-to-end delay, low packet loss, and low power consumption in the low rate wireless personal areas networks (LR-WPANs). This paper develops an analytical model to quantify the key performance metrics of the MAC protocol in LR-WPANs with bursty ONOFF traffic. This study fills the gap in the literature by removing the assumptions of saturated traffic or nonbursty unsaturated traffic conditions, which are unable to capture the characteristics of bursty multimedia traffic in sensor networks. This analytical model can be used to derive the QoS performance metrics in terms of throughput and total delay. The accuracy of the model is verified through NS-2 (http://www.isi.edu/nsnam/ns/) simulation experiments. This model is adopted to investigate the performance of the MAC protocol in LR-WPANs under various traffic patterns, different loads, and various numbers of stations. Numerical results show that the traffic patterns and traffic burstiness have a significant impact on the delay performance of LR-WPANs.
Manco-Vega, Alejandra. "Early career researchers and PhD students from the social sciences use of Social Networking Sites (SNS) for science communication: an affordances approach." Thesis, 2017. http://eprints.rclis.org/31922/1/Early%20career%20researchers%20and%20PhD%20students%20from%20the%20social%20sciences%20use%20of%20Social%20Networking%20Sites%20%28SNS%29%20for%20science%20communication.pdf.
Повний текст джерелаTanta, Mohamed. "Rail power conditioners based on modular multilevel converter in AC railway networks." Doctoral thesis, 2020. http://hdl.handle.net/1822/76856.
Повний текст джерелаRailway systems have progressively been developed since James Watt presented a technique of converting steam power into a circular movement back in 1763. With the novelty of steam engines at that time and the increasing of railway networks, railway industry quickly became an economic catalyst throughout the world due to the advantages of passenger and freight transport. In 1879, Siemens & Halske company introduced the world’s first electric train in the city of Berlin, consisting of a locomotive and three wagons, and supplied via an insulated third rail with 150 V direct current (DC). From that time, the world has begun to recognize the important transition from steam power to electric power, and the potential of the electrified railway as a mode of mass transport. Due to the plenty of fuel in the last century, Diesel trains were not only common, but they also dominated the railway sector for a few decades. Consequently, the development in the infrastructures of electric trains decelerated, and the path to having fully electrified trains was long enough. In this context, electric trains have introduced progressively, in which Diesel and electric power have been combined to create hybrid locomotives. However, and with the increased demand for transportation and the higher fuel prices in the last decades, electric trains can substantially offer lower operating costs and lower emissions compared with the Diesel-powered trains. Nowadays, most of the high-speed electric trains use alternating current (AC) power supply for their traction power systems, which provide better performance under long-distance power transmission than DC power supply. However, as the need for railway transportation increases due to more passengers and higher mobility requirements, more flexible and efficient traction systems are always needed. In Europe, AC traction power systems are mainly classified according to the voltage and frequency parameters (15 kV, 16.7 Hz) or (1×25 kV or 2×25 kV, 50 Hz). In all cases, railway operators have an absolute interest to run the electrified trains with the lowest possible operation and maintenance costs. In this context, power quality improvement at the three-phase power grid, associated with the AC electrified railway has drawn more attention in the last decades, especially after the evolution in the Power Electronics field. Subsequently, various solutions based on Power Electronics converters have been proposed to improve power quality in the electrified railway, e.g., the flexible AC transmission systems (FACTS). The rail power conditioner (RPC) is one of the FACTS devices that can be used to improve power quality by compensating harmonic contents, reactive power and negative sequence components of currents generated by the railway system. Among the other possible multilevel power converters, the modular multilevel converter (MMC) is an attractive solution for medium-voltage applications due to harmonics reduction, lower switching losses, and higher flexibility, scalability and reliability. Therefore, the MMC has been enhanced to be combined with the FACTS family. Taking into consideration the existing opportunities in the railway industry, not only in the development of the electric train itself, but also on the power quality improvement in the electrified railway, there is a strong investment in technological development for electrified railway systems. Therefore, this work presents a new topology of Power Electronics converter (RPC based on MMC) that compensates power quality problems associated with traction power systems, thus, reducing the operating costs of the electrified trains and increasing the power capacity of the electric traction grid. The main innovations of the RPC based on MMC are the integration of the MMC topology to operate as a railway power quality conditioner, benefiting from the advantages of the MMC in the traction power supply system. In this context, the research work proposed and developed in this Ph.D. thesis aimed to design, develop and validate a reduced-scale laboratory prototype of the RPC based on MMC, including all the necessary control algorithms and simulation models that are important to support the correct operation of the proposed system. Under simulation conditions, this work developed control algorithms for different RPC topologies, (full-bridge, half-bridge, three-wire, etc.) for demonstrating the general capabilities of the RPC system, and also for two different transformers connections (V/V and Scott). The most favorable RPC based on MMC topology (based on half-bridge MMC) was deeply and extensively simulated, namely employing predictive control approach. The experimental results obtained from a developed reduced-scale prototype confirm the validity of the presented control theory, as well as the power quality improvement capability of the proposed solution.
Os sistemas ferrovias foram progressivamente desenvolvidos desde que James Watt apresentou uma técnica de conversão da energia a vapor para um movimento circular em 1763. Com a novidade dos motores a vapor e a sua implementação nas redes ferroviárias, a indústria ferroviária rapidamente se tornou um catalisador econômico em todo o mundo devido às vantagens no transporte de passageiros e mercadorias. Em 1879, a empresa Siemens & Halske introduziu o primeiro comboio elétrico do mundo na cidade de Berlim, consistindo numa locomotiva com três vagões, alimentado por um terceiro trilho isolado alimentado com corrente contínua em 150 V (CC). A partir desse momento, o mundo começou a reconhecer a importante transição da energia a vapor para a energia elétrica e o potencial na ferrovia eletrificada como um meio de transporte de massa. Devido à abundância de combustível fóssil no século passado, os comboios a Diesel não eram apenas comuns, mas também dominaram o setor ferroviário. Consequentemente, o desenvolvimento das infraestruturas dos comboios elétricos desacelerou, e o caminho para haver comboios totalmente eletrificados tornou-se bastante longo. Nesse contexto, os comboios elétricos começaram a impor-se progressivamente, inicialmente pela combinação do motor Diesel e do motor elétrico, resultando numa locomotiva híbrida. No entanto, com o aumento da demanda pelo transporte, e com o aumento do preço dos combustíveis nas últimas décadas, os comboios elétricos afirmaram-se por poderem oferecer custos operacionais mais baixos, assim como melhor desempenho ambiental. Atualmente, a maioria dos comboios elétricos de alta velocidade utilizam sistema de tração em corrente alternada (CA), que oferece melhor desempenho na transmissão de energia a longa distância do que sistema de tração em corrente contínua CC. No entanto, o aumento do transporte ferroviário requer a melhoria da eficiência energética devido a haver mais passageiros e maiores requisitos de mobilidade. Na Europa, os sistemas de tração elétrica são classificados principalmente de acordo com os parâmetros de tensão e frequência (15 kV, 16,7 Hz) ou (1×25 kV ou 2×25 kV, 50 Hz). Em ambos os casos, os operadores ferroviários têm interesse absoluto em otimizar os custos. Nesse contexto, a melhoria da qualidade de energia elétrica na ferrovia suscitou mais atenção nas últimas décadas, principalmente pela introdução da eletrônica de potência. Posteriormente, várias soluções baseadas em conversores de eletrônica de potência foram propostas para melhorar a qualidade de energia elétrica na ferrovia, como por exemplo, os sistemas flexíveis de transmissão CA (FACTS – Flexible AC Transmission Systems). O condicionador ativo de potência ferroviário (RPC – Rail Power Conditioner) é um dos dispositivos FACTS que pode ser usado para melhorar a qualidade da energia elétrica, compensando o conteúdo harmônico, a potência reativa e os componentes de sequência negativa das correntes. Por outro lado, o conversor multinível modular (MMC – Modular Multilevel Converter) é uma solução atraente para aplicações de média tensão, devido à redução dos harmónicos e das perdas de comutação, e ao aumento da flexibilidade, confiabilidade e escalabilidade. Deste modo, o MMC foi aprimorado para ser integrado na família FACTS. Levando em consideração as oportunidades existentes no setor ferroviário, não apenas no desenvolvimento do próprio comboio elétrico, mas também na melhoria da qualidade de energia elétrica na ferrovia, existe um forte investimento no desenvolvimento tecnológico para os sistemas ferroviários eletrificados. Assim sendo, este trabalho apresenta uma nova topologia de conversor de eletrônica de potência (RPC baseado em MMC) que compensa os problemas de qualidade de energia elétrica associados aos sistemas de tração, reduzindo os custos operacionais dos comboios elétricos e otimizando a qualidade de energia da rede elétrica. As inovações principais do RPC baseado em MMC são a integração da topologia do MMC para operar como condicionador de qualidade de energia elétrica na ferrovia, beneficiando das vantagens do MMC. Neste contexto, o trabalho de investigação proposto e desenvolvido nesta tese apontou como objetivo projetar, desenvolver e validar um protótipo laboratorial em escala reduzida do RPC baseado em MMC, incluindo todos os algoritmos de controlo necessários e os modelos de simulação que são importantes para suportar a operação correta do sistema. Sob condições de simulação, este trabalho desenvolveu algoritmos de controlo para diferentes topologias do RPC (ponte completa, meia ponte, três fios, etc.), para demonstrar as capacidades gerais do sistema do RPC, e também para dois transformadores diferentes (V/V e Scott). O RPC mais favorável baseado na topologia do MMC (baseado no MMC de meia ponte) foi profunda e extensivamente simulado, nomeadamente utilizando uma abordagem de controlo preditivo. As simulações e os resultados experimentais confirmam a validade da teoria de controlo apresentada, bem como a capacidade de melhoria da qualidade de energia elétrica na solução proposta.
Fundação para a Ciência e a Tecnologia – FCT), which allowed me to continue my studies with the PD/BD/127815/2016 Ph.D. scholarship under the Innovation in Railway Systems and Technologies Doctoral Program – iRail.
Chang, Jo-Yu, and 常若愚. "The Collision Analysis of CSMA/CA for IEEE 802.15.4 Low-Rate Wireless Personal Area Network." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/63188747574601239614.
Повний текст джерела逢甲大學
資訊工程所
92
With the growth quickly of the wireless network technology, there are more and more existent network servies trending to adopt wireless network technology. The popularization of IEEE 802.11 Wireless LAN and IEEE 802.16 Wireless Broadband Network, all make the wireless network technology become more and more important, and there are many relative technologies and products appeared. Following Bluetooth’s rise and development, Wireless Personal Area Network (WAPN) also became popular. Therefore, one application of WPAN – Wireless Sensor Network, also start to be discuss widely. Wireless Sensor Network (WSN) make use of a large number of sensor nodes to dispose in a particular range, and every sensor node must to sense the special information in the area (ex:temperature, humidity, pressure,etc). Then, transmit the data through wireless transmission technology to a special equipment (Sink) to analyze to sensing data and to do corresponding actions. WSN is one application of WPAN, there is no definite specifications. Now, many WSN research use IEEE 802.15.4 to design, it characteristic includes low rate, low transit distance, low power, simple architecture, low cost, small size, etc. All characteristic are similar to the applications of WSN. In IEEE 802.15.4, packets maybe occur collision or packet loss when sensor nodes try to transit. WSN’s transmission characteristic is differ from general network. General network always have large number of packets to be transmit, but WSN transmissive interval is long (1 min, 5 min, even 1 hour.).therefore, the characteristic of collision problem maybe differ from general network. IEEE 802.15.4 make use of CSMA/CA to solve collision problem, the CSMA/CA algorithm is similar to IEEE 802.11, but not all the same. We called Slotted CSMA/CA algorithm. I will explain in this paper. Furthermore, in this paper, I will aim at IEEE 802.15.4 collision mechanism, and use program to simulate the operation of IEEE 802.15.4. Finally, Analyze and estimate the performance of Slotted CSMA/CA algorithm, and try to find out the Slotted CSMA/CA’s optimum BE parameter in simulation result.
Chen, Ching-hsiang, and 陳慶祥. "A Study on Security Assessment of Network Connection through SSL / TLS and CA Flow Analysis." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/j2a4f8.
Повний текст джерела大同大學
資訊經營學系(所)
106
In recent years, with the trend of Internet services, personal information is often disclosed and compromised on the Internet. In order to enhance information security with consideration of communication convenience, most websites and communication software support HTTPS connection. Nowadays more than 50% of Internet traffic has taken HTTPS encrypted communication protocol. Previous studies focused on encrypted network communication trying to identify software connection signature. Their disadvantage is that if the version of signature varies with the time, the original signature is no more valid. In addition, they did not consider the connection security. This study started from establishing a system to monitor network traffic by collecting various kinds of communication protocols (such as SSL or TLS). It also checked the validity of certificates by their issuers and valid dates of the certificates. To analyze the access to websites through secure channel, we use HTTPS (SSL/TLS) and credential information to determine the security of the connection. We use the version of SSL or TLS and the site digital certificate such as CA voucher issuing unit and expiration date as conditions for judging the security of HTTPS connection. The experimental results summarized from 20 experiments reveal that the security of the internal HTTPS connection within the enterprise can be identified. Advantage of this approach includes that version updates of software do not affect the effectiveness of our method. It is suggested that research in the future could include identifications of other software to increase connection security.
Lin, Jing-Ting, and 林敬庭. "Analysis and Improvement of IEEE 802.15.4 Slotted CSMA/CA over a Real-Time Wireless Sensor Network." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/52h47e.
Повний текст джерела國立臺北科技大學
電腦與通訊研究所
97
In this paper, we propose the effective analysis methodology to be applied to the monitoring network of synchronous under the IEEE 802.15.4 standard, we call it real-time wireless sensor network (RT-WSN) in this network that is build for the “real-time” specific application. We aim at the slotted Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) of algorithm of channel access mechanism in IEEE 802.15.4 MAC layer to build the network model and analyze the average packet delay over RT-WSN based on probability theory. The proposed theoretical analysis was nearly consistent with the correct result of simulation and the experiment. The result shows that this slotted CSMA/CA cannot be effectively applied to RT-WSN since it cannot avoid the high packet collision in the saturation throughput conditions. When receiving 10 sensor nodes, the packet delay caused by packet collision is 6.29 times more than one ideal model. Hence, we propose the like Time Division Multiple Access (TDMA) to improve CSMA/CA in packet collision problem. With neighbor table, TDMA can record the network states and implement the dynamic network configuration. Our experimental results show that TDMA can own the characteristics of the stable and limited packet delay. Once the total traffic load is lower than maximum throughput, it can guarantee the packet transmission of real-time without considering the amount of sensor nodes in network. Moreover, compare with CSMA/CA in 10 sensor nodes conditions, 57 % of the maximum throughput is improved. Therefore, we can meet with the QoS requirement of packet delay in RT-WSN. In the end, we install a remote ECG monitoring system for an example of application situation in the sanatorium. We provide steady wireless transmission media for the front of this system and reach the purpose of real-time remote medical care.
Κατερινοπούλου, Αικατερίνη. "Σύνθεση, δομή και ιδιότητες βιοενεργών υάλων SiO2-MO (M=Ca, Mg) και SiO2-CaO-P2O5". Thesis, 2008. http://nemertes.lis.upatras.gr/jspui/handle/10889/1631.
Повний текст джерелаIn the present thesis our work was focused on the study of the synthesis and characterization of bioactive glasses. Pure SiO2 and mixed glasses composed of SiO2–ΜΟ (Μ=Ca, Mg) and SiO2–CaΟ–P2O5 were prepared using different amounts of modifiers (Ca, Mg). Next the prepared materials were characterized by using various techniques such as: BET, SEM, TGA, XRD and IR. Finally their bioactivity was studied in vitro after immersion in SBF solution. It was found that the prepared materials showed a mesoporous structure. Regarding the bioactivity glasses with compositions of SiO2–CaO and SiO2–CaΟ–P2O5 induced the formation of apatite layer on their surface.
Skorova, Ekaterina. "Calcium and cAMP homeostasis determine network organisation of respiratory pre-Bötzinger neurons in Mecp2 null mice in vitro." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-0001-BAA2-0.
Повний текст джерелаDörpinghaus, Jens. "Soziale Netzwerke im frühen Christentum nach der Darstellung in Apg 1-12." Diss., 2020. http://hdl.handle.net/10500/26609.
Повний текст джерелаIncludes bibliographical references (leaves 197-211)
Biblical studies in New Testament are generating considerable interest in the investigation of historical groups, for example by using prosopographic approaches. This thesis presents a new approach to reconstruct the early Christian network in Acts 1-12. We consider the social network analyses (SNA), critical spatiality and Proximal Point Analyses (PPA). Although these approaches show interesting results, they suffer from a global distance measure. Thus, we introduce a novel approach combining SNA and critical spatiality to analyse geographic and social distances. This method represents a valuable alternative to traditional theological tools for answering exegetical questions concerning the social network in Acts 1-12 offering ways for re-thinking and re-interpretation. The network represents the first fulfillment of the promise given in Acts 1:8. Moreover, it allows us to distinguish between protagonists and their influence. Using different distance measurements, we were not only able to describe the high level of solidarity in this network but could also find strong evidences for Peter, Philip and Barnabas being key figures. Acts 1-12 describes mission as led by God and performed by different people with Jerusalem as the centre of activity. This mission is both peripheral and open to people with diverse social, religious and geographic backgrounds. In the novel network of people belonging to the body of Christ human leadership is not important. It was not possible to apply this method to all exegetical questions due to the fact that there are only limited historic sources available.
In der neutestamentlichen Wissenschaft wurden verschiedene Methoden wie die Prosopographie zur Erforschung bestimmter Personenkreise verwendet. Diese Arbeit beschäftigt sich mit der Rekonstruktion des frühchristlichen sozialen Netzwerks nach der Darstellung in Apg 1-12. Dazu wird die Methode der sozialen Netzwerkanalyse (SNA), der critical spatiality sowie die Proximal Point Analyse (PPA) verwendet. Dabei werden die methodischen Ansätze von verschiedenen historischen Netzwerkanalysen zusammengetragen und durch eine Verknüpfung von SNA und critical spatiality eine einheitliche Herangehensweise hergeleitet, die auch geographische wie soziale Distanzen darstellen kann. Dabei finden sich in Apg 1-12 sowohl exegetische Fragestellungen, auf die diese Methode aufgrund der schlechten Quellenlage nicht angewendet werden kann, als auch Fragestellungen, die mit dieser Methode unter neuen Gesichtspunkten interpretiert werden kann. So lässt sich im rekonstruierten Netzwerk von Apg 1-12 der erste Abschnitt der Erfüllung der Verheißung aus Apg 1,8 erkennen. Außerdem hilft die SNA, die einzelnen Akteure und ihr Handeln in der Apg besser zu würdigen. So ist ein eigenes Kapitel nicht nur Petrus, sondern auch Philippus und Barnabas gewidmet. Apg 1-12 stellt eine Mission dar, deren alleiniger Urheber Gott ist und die von verschiedensten Menschen mit der Stadt Jerusalem als Zentrum überwiegend dezentral und offen für verschiedene soziale, religiöse und geographische Hintergründe ausgeführt wird. Sie zeichnet ein besonderes Bild vom urchristlichen sozialen Netzwerk, das wenig menschliche Leitung beinhaltet und sich qualitativ unterscheidet. Die Analyse mit verschiedenen Zentralitätsmaßen zeigt ebenfalls die starke Verbundenheit der urchristlichen Gemeinschaft und den signifikanten Beitrag mehrerer Personen
New Testament
M. Th. (New Testament)
Pereira, Paulo Macedo. "Analysis of Network Attacks and Security Events using Modern Data Visualization Techniques." Master's thesis, 2015. http://hdl.handle.net/10400.6/6009.
Повний текст джерелаAs técnicas de visualização de dados contêm recursos vitais em várias áreas, desde a pesquisa até há área pro ssional. Representações e cazes estão frequentemente a contribuir para a compreensão do quadro geral, a partir de um grande volume de dados, às vezes permite novas descobertas ou para uma síntese e ciente. Devido há grande quantidade de dados que os computadores lidam nos dias de hoje, muitas técnicas modernas de visualização de dados foram desenvolvidas para lidar com os grandes conjuntos de dados, permitindo perceber características únicas. Na era da informação, os computadores (e os seus utilizadores) e as redes estão entre as maiores fontes de dados, embora eles também sejam utilizados no seu processamento e armazenamento. Muitos sistemas de monitorização de rede e dispositivos de segurança fazem uso de técnicas de visualização de dados tradicionais para reportar funcionalidades ou para fornecer informações pro ssionais sobre o estado dos dados. O âmbito deste trabalho insere-se no cruzamento dos campos, das técnicas de segurança de rede e de visualização dos dados. Os objectivos são estudar abordagens modernas para representar os dados, que podem actualmente ser utilizados em outras áreas, e aplicar uma dessas abordagens na visualização de tráfego de rede e ataques. Avaliar a sua utilidade das visualiza ções também era um objectivo, juntamente com a constituição de um grande conjunto de representações para várias classes de tráfego e ataques de rede clássicos. A técnica conhecida como Circos, amplamente utilizada para representações genéticas, foi aplicada para alcançar os objectivos deste programa de mestrado. Muitas representações para pelo menos 18 conjuntos de tráfego diferentes foram produzidas ao longo deste trabalho, com muitas analisadas detalhadamente nesta dissertação. Esses conjuntos, contendo tráfego gerados pelas aplicações contemporâneas e ataques clássicos de rede ou actividades de sondagem, foram seleccionados a partir de dois conjuntos de dados. De forma a produzir o Circos, um conjunto mínimo de características de tráfego foram identi cadas, e foram implementados vários scripts para automatizar o processo. Para a parte nal deste trabalho, uma experiência baseada na comparação (humana) entre nove conjuntos conhecidos e nove desconhecidos foram criados. Para demonstrar que as representações foram úteis para identi car as classes de tráfegos ou ataques. Durante a experiência, foi possível identi car correctamente oito, dos nove conjuntos (um dos ataques foi incorrectamente classi cado como tráfego Hypertext Transfer Protocol (HTTP)), comprovando a utilidade desta técnica nesta área.