Um die anderen Arten von Veröffentlichungen zu diesem Thema anzuzeigen, folgen Sie diesem Link: Telecommunication systems Mathematical models.
Dissertationen zum Thema „Telecommunication systems Mathematical models“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit Top-50 Dissertationen für die Forschung zum Thema "Telecommunication systems Mathematical models" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Sehen Sie die Dissertationen für verschiedene Spezialgebieten durch und erstellen Sie Ihre Bibliographie auf korrekte Weise.
1
Britton, Matthew Scott. „Stochastic task scheduling in time-critical information delivery systems“. Title page, contents and abstract only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09phb8629.pdf.
Der volle Inhalt der QuelleAnnotation:
"January 2003" Includes bibliographical references (leaves 120-129) Presents performance analyses of dynamic, stochastic task scheduling policies for a real- time-communications system where tasks lose value as they are delayed in the system.
2
Hou, Yuen Tan. „Resource management in multimedia communication systems“. HKBU Institutional Repository, 2003. http://repository.hkbu.edu.hk/etd_ra/478.
Der volle Inhalt der Quelle
3
Witosurapot, Suntorn, und wsuntorn@fivedots coe psu ac th. „Resolving competition for resources between multimedia and traditional Internet applications“. Swinburne University of Technology, 2004. http://adt.lib.swin.edu.au./public/adt-VSWT20050309.123048.
Der volle Inhalt der QuelleAnnotation:
Although the Internet is the dominant broadband network, it still has a fundamental shortcoming in traffic management that does not properly support efficient use of resources together with differentiated quality of service for mixed traffic types. Even though a number of mechanisms have been proposed under key approaches of resource adaptation, resource reservation, and resource pricing, this problem remains unsolved to date because of its complexity and the way it relates to so many considerations of engineering and economics, and the diverse range of services desired by users. Hence it is considered difficult to devise a perfect mechanism that can universally solve this problem. In this respect, this dissertation contributes to insights into potential combinations and trade-offs of key approaches above in some efficient manner for managing traffic and scarce resources in the Internet. The first part of this work considers the combination of relaxed resource reservation and resource pricing schemes for handling the unfair bandwidth distribution problem in soft-bandwidth guarantee services of the Differentiated Services (DiffServ) Internet. We show that this unfairness problem can be handled using a network-user cooperative approach that addresses both individual user satisfaction and global optimization. We propose to add a mechanism based on price-based feedback signaling to DiffServ-capable routers providing Assured Forwarding (AF) Service so that they can offer per-flow signaling. This still allows them to work at an aggregate traffic level, hence the scalability feature of the DiffServ network can be retained. Our proposed mechanism allows the network to offer reliable service assurances via a distributed optimization algorithm, without introducing special protocols or requiring routers to have access of individual user requirements. Moreover, it can provide incentives for users to cooperate so that optimum performance can be accomplished. This approach has broad applicability and is relevant to all types of assured service classes. The second part of this work considers the combination of a specific resource pricing scheme based on a distributed optimization algorithm and multimedia adaptation schemes. Such a capability has not been available because most utility functions of multimedia applications do not meet the concavity constraints required by optimization algorithm. We proposed to overcome this limitation by redefining user utility functions into equivalent discrete forms and using combinatorial (discrete) optimization so that interfacing the resource-pricing scheme can be done in a normal way. However, to obtain feasible solutions in a scalable manner, an agent is included into the scheme for solving the combinatorial (discrete) optimization on behalf of a small group of users. In return, all users belonging to this group can benefit from social welfare maximization of their utilities over a network resource constraint. The last part of this work considers the combination of relaxed resource reservation and resource pricing schemes to enable a proper charging scheme for adaptive applications in the DiffServ Internet. We provide an optimization formulation of the problems of revenue and social welfare maximization, applied at a service provider (SP) who gives access to the DiffServ Internet. In this scheme, resources are provisioned per QoS-oriented class in a long time scale (service level agreement (SLA) duration), then priced based on user demand in the short time scale. We also show that the proposed charging scheme can provide feedback and incentives for users to use the network resource optimally via the standard packet marking, hence eliminating the need for specific pricing protocol. All of the proposals in this work can be used together, solving these key problems as a coordinated whole, and all use readily available network mechanisms.
4
Tomlin, Toby-Daniel. „Analysis and modelling of jitter and phase noise in electronic systems : phase noise in RF amplifiers and jitter in timing recovery circuits“. University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0021.
Der volle Inhalt der QuelleAnnotation:
Timing jitter and phase noise are important design considerations in most electronic systems, particularly communication systems. The desire for faster transmission speeds and higher levels of integration, combined with lower signal levels and denser circuit boards has placed greater emphasis on managing problems related to phase noise, timing jitter, and timing distribution. This thesis reports original work on phase noise modelling in electronic systems. A new model is proposed which predicts the up-conversion of baseband noise to the carrier frequency in RF amplifiers. The new model is validated by comparing the predicted phase noise performance to experimental measurements as it applies to a common emitter (CE), bipolar junction transistor (BJT) amplifier. The results show that the proposed model correctly predicts the measured phase noise, including the shaping of the noise about the carrier frequency, and the dependence of phase noise on the amplifier parameters. In addition, new work relating to timing transfer in digital communication systems is presented. A new clock recovery algorithm is proposed for decoding timing information encoded using the synchronous residual time-stamp (SRTS) method. Again, theoretical analysis is verified by comparison with an experimental implementation. The results show that the new algorithm correctly recovers the source clock at the destination, and satisfies the jitter specification set out by the ITU-T for G.702 signals.
5
Bradley, W. Scott. „Propagation modeling for land mobile satellite communications“. Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/74511.
Der volle Inhalt der QuelleAnnotation:
Satellite systems are being planned for two-way communication with mobile vehicles using UHF and L-band frequencies. Of special concern in the system design are the characteristics of propagation in suburban and rural areas where fading occurs due to multipath effects and vegetative shadowing. A review of the literature was performed to study these propagation impairments. Available experimental data are examined, compared, and summarized. Propagation through vegetation is studied in order to compare reported modeling efforts and to determine the parameter dependences of path loss. A simple deterministic path model is then presented to estimate vegetative path loss. An overall statistical model is also proposed to describe the signal level fading statistics. The statistical model is compared to data, and the deterministic path model is used to determine the mean of signal level distribution functions in the presence of shadowing.Master of Science
6
Barreira, Ramiro Roque Antunes. „Modelo mel-cepstral generalizado para envoltória espectral de fala“. [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259047.
Der volle Inhalt der QuelleAnnotation:
Orientadores: Fábio Violaro, Edmilson da Silva MoraisDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-17T02:12:55Z (GMT). No. of bitstreams: 1 Barreira_RamiroRoqueAntunes_M.pdf: 2303475 bytes, checksum: 72e03fe8e41e9e440f2d4a266666763d (MD5) Previous issue date: 2010
Resumo: A análise Mel-Cepstral Generalizada (MGC) corresponde a uma abordagem para estimação de envoltória espectral de fala que unifica as análises LPC, Mel-LPC, Cepstral e Mel-Cepstral. A forma funcional do modelo MGC varia continuamente com dois parâmetros reais ? e ?, possibilitando que o modelo assuma diferentes características. A flexibilidade oferecida pelo modelo MGC aliada à sua estabilidade e bom desempenho sob manipulação de parâmetros tem feito com que os parâmetros MGC sejam empregados com sucesso em codificação de fala e síntese de fala via HMM (Hidden Markov Models). O presente trabalho foca os aspectos matemáticos da análise MGC, abordando e demonstrando, em extensão, a formulação em seus vieses analítico e computacional para a solução do modelo. As propriedades e formulações básicas da análise MGC são tratadas na perspectiva do espectro mel-logarítmico generalizado. Propõe-se um método para a computação dos coeficientes MGC e Mel-Cepstrais que não envolve o uso de fórmulas recursivas de transformação em freqüência. As análises e experimentos relacionados ao método encontram-se em estágio inicial e devem ser completados no sentido de se identificar a relação ganho computacional × qualidade da representação.
Abstract: Mel-Generalized Cepstral analysis (MGC) is an approach for speech spectral envelope estimation that unifies LPC, Mel-LPC, Cepstral and Mel-Cepstral Analysis. The functional form of the MGC model varies continuously with the real parameters ? e ?, enabling the model to acquire different characteristics. The flexibility of MGC model associated with its stability and good performance under parameter manipulation have made MGC parameters to be successfully employed in speech codification and HMM speech synthesis. The present study focuses on mathematical aspects of MGC analysis, treating and proving, in a fairly extended way, analytical and computational formulation for model solution. MGC analysis properties and basic formulation are treated in melgeneralized logarithmic spectrum perspective. A method for the computation of MGC and Mel-Cepstral coefficients that do not require frequency transformation recursion formulas is proposed. Experiments and analysis concerning the method are in their initial stage and needs to be completed in the sense to identify computational × representation performances.
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
7
Borg, Andreas. „Processes and Models for Capacity Requirements in Telecommunication Systems“. Doctoral thesis, Linköping : Department of Computer and Information Science, Linköpings universitet, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-16932.
Der volle Inhalt der Quelle
8
Coyle, Andrew James. „Some problems in queueing theory“. Title page, contents and summary only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09phc8812.pdf.
Der volle Inhalt der Quelle
9
Pawlowska, Bogna Julia. „Mathematical models of microbial evolution : cooperative systems“. Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/26819.
Der volle Inhalt der QuelleAnnotation:
Microbes usually live in large communities, where they interact with other organisms and species. These interactions include cooperation, when individuals facilitate each others growth and reproduction. Such cooperation has been for instance observed within pathogens in the process of infection. Therefore, given the number and the frequency of infectious diseases, understanding the nature and the dynamics of microbial cooperation may be a crucial step in modern medicine. Microbes often secrete costly enzymes which extracellularly metabolise resources available in the environment. This external metabolism is a form of ’public good cooperation’, in which individuals invest their energy in producing ’public goods’, available to other organisms. To study this phenomenon we deploy mathematical models which are based on biologically relevant assumptions. Our models not only aim to capture the dynamics of studied microbial communities, but also to remove the natural complexity arising in the empirical studies and thus to provide a mechanistic understanding of their results. We first recover and explain the recent empirical finding, about mixed strain infections, showing that an addition of a low virulent strain which does not produce public goods (termed ’cheat’) may counter-intuitively enhance the total population virulence. What drives this result turns out to be an interaction of two different cooperative traits and the presence of spatial structure. Next we study the competition between the strains that do and do not produce public goods. Our results depend on environmental conditions, such as resource concentration and population density, but they are also determined by the degree of spatial structure - the ecological trait which so far has been treated only as a binary variable. Finally, we identify some environmental threats for the external metabolism feeding strategy, and we examine its competitiveness in comparison to ’internal metabolism’, in which the costly enzymes are private.
10
Nagarajan, Krishnamurthy. „New resource allocation strategies based on statistical network traffic models“. Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/33437.
Der volle Inhalt der Quelle
11
梁慧敏 und Wai-man Wanthy Leung. „Evolutionary optimisation of industrial systems“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B30252994.
Der volle Inhalt der Quelle
12
Downs, Michael S. „Developing integrated decision support systems from mathematical models“. Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA303712.
Der volle Inhalt der QuelleAnnotation:
Thesis (M.S. in Information Technology Management) Naval Postgraduate School, September 1995.Thesis advisor(s): H. Bhargava,R.K. Wood. "September 1995." Bibliography: p. 43. Also available online.
13
Gómez, Bardón María del Rocío. „Mathematical models and simulations of complex social systems“. Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1287/.
Der volle Inhalt der QuelleAnnotation:
In this thesis we present two different models of Complex Social Systems. The first model represents a vector-borne disease that takes place in a heterogeneous environment composed of areas of different types. Two populations take part in the epidemic process: humans and vectors. The population of humans moves around the heterogeneous environment. The idea of this model is to understand how the movement of people in the heterogeneous environment can affect the dynamics of the disease. The second model represents a Susceptible-Infected-Susceptible process on a social network. The population is represented as nodes, and the edges represent the possible transmissions between two people. We investigate how different topologies in the network affect the spread of the disease in the system. We simulate both models, and we perform a mathematical analysis of both of them. For the mathematical analysis we use an adapted version of the Random Heuristic Search framework, which was originally used for the understanding of Genetic Algorithms. In this thesis we investigate the predictability power of the mathematical approach.
14
Ma, Chunyan. „Mathematical security models for multi-agent distributed systems“. CSUSB ScholarWorks, 2004. https://scholarworks.lib.csusb.edu/etd-project/2568.
Der volle Inhalt der QuelleAnnotation:
This thesis presents the developed taxonomy of the security threats in agent-based distributed systems. Based on this taxonomy, a set of theories is developed to facilitate analyzng the security threats of the mobile-agent systems. We propose the idea of using the developed security risk graph to model the system's vulnerabilties.
15
馮達淸 und Tat-ching Fung. „Steady state solutions of nonlinear dynamic systems“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B31231809.
Der volle Inhalt der Quelle
16
Stuk, Stephen Paul. „Multivariable systems theory for Lanchester type models“. Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/24171.
Der volle Inhalt der Quelle
17
Zhou, Wen, und 周雯. „A study of channel estimation for OFDM systems and system capacity forMIMO-OFDM systems“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45555850.
Der volle Inhalt der Quelle
18
Li, Yang. „Models and applications of wireless networks in rural environments“. Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
Der volle Inhalt der QuelleAnnotation:
With the unprecedented growth of the communication industry that the world is experiencing, the demand from rural inhabitants for high quality communications at an economically affordable cost is growing. However, rural areas are rather restricted from deploying communication services due to the rough natural environment, and the shortage of rudimentary communication facilities and technical personnel. Appropriate models for building rural wireless networks and a concomitant simulation environment are, therefore, expected to enable the construction of technologically-optimal and economically-efficient networks in specified rural areas.The research has set up two independent models, one for the economic need and the other for the technical need of building networks in rural areas. One model was the Impact of Telecommunications Model, which disclosed the importance of building a wireless network in specified rural areas by choosing an economic parameter to forecast the profitability of the network. The other was the Service Model, which collected primitive data from given rural areas and abstracted these data by flowing them through four technical layers to form the predicted technical wireless network. Both of the models had been applied to real-world cases to demonstrate how to use them.
A simulation environment was finally designed and implemented to realize the above two models for the sake of instantiation. This environment could simulate the specified rural network by constructing a wireless network on the invented areas and evaluating its quality and economic efficiency. It was written in Scilab simulation language, which was an open source.
19
Basak, Rishi. „Environmental management systems and the intra-firm risk relationship“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0034/MQ64316.pdf.
Der volle Inhalt der Quelle
20
Dasci, Abdullah. „Discrete and continuous models for production-distribution systems“. Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37625.
Der volle Inhalt der QuelleAnnotation:
This thesis presents a series of integrated models for simultaneous optimization of location, capacity, product range, and production technology decisions in production-distribution systems. The interactions between these decisions can be significant. This thesis draws its motivation from these interactions. In order to benefit from the capital and/or employment subsidies, preferential tax rates, and free trade zones provided by governments, firms need to take the interdependencies between their location, capacity and technology decisions into account. These decisions could be further complicated due to varying scale and scope economies inherent in different production technologies.The models proposed in this thesis are based on two fundamentally different but equally central approaches. The first approach builds on traditionally popular integer programming formulation in facility location theory, in which two such models presented in this thesis. The first one assumes that there are a number of dedicated production technologies for each product whereas, the second one assumes that a set of flexible technologies is also present. Analytical properties of the models are described, which lead to the development of exact and heuristic solution procedures. Results of several sets of computational experiments are also reported. The second approach is based on continuous approximation (also known as continuum mechanics), which has not been used to its potential in the literature. The third model in this thesis is proposed for a system with single product. It is based on the use of continuous functions in representing spatial distribution of cost parameters and decision variables. In this model, the focus is to compute the service regions leaving the precise plant locations to a subsequent analysis. This model lends itself to closed form solutions and allows derivation of a number of insights on the impact of several cost factors on facility design decisions. Then, it is utilized in an analytical framework to analyze several plant focus decisions of firms in a multi-product environment. The closed form solution is used to analyze several product and market focus strategies, which have provided several insights into more sophisticated plant focus decisions and into the impact of different production technologies on these decisions.
21
Kröckel, Silke. „Stochastic production-inventory systems with significant setup times“. Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/24367.
Der volle Inhalt der Quelle
22
Yuen, Wai-on, und 袁偉安. „Models and numerical algorithms for re-manufacturing systems“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30292931.
Der volle Inhalt der Quelle
23
Li, Tang, und 李唐. „Markov chain models for re-manufacturing systems and credit risk management“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40203700.
Der volle Inhalt der Quelle
24
陳立梅 und Lap-mui Ann Chan. „Near optimal lot-sizing policies for multi-stage production/inventory systems“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1990. http://hub.hku.hk/bib/B31209129.
Der volle Inhalt der Quelle
25
Cong, Yang, und 丛阳. „Optimization models and computational methods for systems biology“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B47752841.
Der volle Inhalt der QuelleAnnotation:
Systems biology is a comprehensive quantitative analysis of the manner in
which all the components of a biological system interact functionally along with
time. Mathematical modeling and computational methods are indispensable
in such kind of studies, especially for interpreting and predicting the complex
interactions among all the components so as to obtain some desirable system
properties. System dynamics, system robustness and control method are three
crucial properties in systems biology. In this thesis, the above properties are
studied in four different biological systems.
The outbreak and spread of infectious diseases have been questioned and
studied for years. The spread mechanism and prediction about the disease could
enable scientists to evaluate isolation plans to have significant effects on a particular
epidemic. A differential equation model is proposed to study the dynamics
of HIV spread in a network of prisons. In prisons, screening and quarantining
are both efficient control manners. An optimization model is proposed to study
optimal strategies for the control of HIV spread in a prison system.
A primordium (plural: primordia) is an organ or tissue in its earliest recognizable
stage of development. Primordial development in plants is critical to the
proper positioning and development of plant organs. An optimization model and
two control mechanisms are proposed to study the dynamics and robustness of primordial systems.
Probabilistic Boolean Networks (PBNs) are mathematical models for studying
the switching behavior in genetic regulatory networks. An algorithm is proposed
to identify singleton and small attractors in PBNs which correspond to
cell types and cell states. The captured problem is NP-hard in general. Our
algorithm is theoretically and computationally demonstrated to be much more
efficient than the naive algorithm that examines all the possible states.
The goal of studying the long-term behavior of a genetic regulatory network is
to study the control strategies such that the system can obtain desired properties.
A control method is proposed to study multiple external interventions meanwhile
minimizing the control cost.
Robustness is a paramount property for living organisms. The impact degree
is a measure of robustness of a metabolic system against the deletion of single
or multiple reaction(s). An algorithm is proposed to study the impact degree
in Escherichia coli metabolic system. Moreover, approximation method based
on Branching process is proposed for estimating the impact degree of metabolic
networks. The effectiveness of our method is assured by testing with real-world
Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae and Homo Sapiens
metabolic systems.published_or_final_version
Mathematics
Doctoral
Doctor of Philosophy
26
Almohri, Hussain. „High Assurance Models for Secure Systems“. Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/22030.
Der volle Inhalt der QuelleAnnotation:
Despite the recent advances in systems and network security, attacks on large enterprise networks consistently impose serious challenges to maintaining data privacy and software service integrity. We identify two main problems that contribute to increasing the security risk in a networked environment: (i) vulnerable servers, workstations, and mobile devices that suffer from vulnerabilities, which allow the execution of various cyber attacks, and, (ii) poor security and system configurations that create loopholes used by attackers to bypass implemented security defenses.Complex attacks on large networks are only possible with the existence of vulnerable intermediate machines, routers, or mobile devices (that we refer to as network components) in the network. Vulnerabilities in highly connected servers and workstations, that compromise the heart of today\'s networks, are inevitable. Also, modern mobile devices with known vulnerabilities cause an increasing risk on large networks. Thus, weak security mechanisms in vulnerable network components open the possibilities for effective network attacks.
On the other hand, lack of systematic methods for an effective static analysis of an overall complex network results in inconsistent and vulnerable configurations at individual network components as well as at the network level. For example, inconsistency and faults in designing firewall rules at a host may result in enabling more attack vector. Further, the dynamic nature of networks with changing network configurations, machine availability and connectivity, make the security analysis a challenging task.
This work presents a hybrid approach to security by providing two solutions for analyzing the overall security of large organizational networks, and a runtime framework for protecting individual network components against misuse of system resources by cyber attackers. We observe that to secure an overall computing environment, a static analysis of a network is not sufficient. Thus, we couple our analysis with a framework to secure individual network components including high performance machines as well as mobile devices that repeatedly enter and leave networks. We also realize the need for advancing the theoretical foundations for analyzing the security of large networks.
To analyze the security of large enterprise network, we present the first scientific attempt to compute an optimized distribution of defensive resources with the objective of minimizing the chances of successful attacks. To achieve this minimization, we develop a rigorous probabilistic model that quantitatively measures the chances of a successful attack on any network component. Our model provides a solid theoretical foundation that enables efficient computation of unknown success probabilities on every stage of a network attack. We design an algorithm that uses the computed attack probabilities for optimizing security configurations of a network. Our optimization algorithm uses state of the art sequential linear programming to approximate the solution to a complex single objective nonlinear minimization problem that formalizes various attack steps and candidate defenses at the granularity of attack stages.
To protect individual network components, we develop a new approach under our novel idea of em process authentication.
We argue that to provide high assurance security, enforcing authorization is necessary but not sufficient. In fact, existing authorization systems lack a strong and reliable process authentication model for preventing the execution of malicious processes (i.e., processes that intentionally contain malicious goals that violate integrity and confidentiality of legitimate processes and data). Authentication is specially critical when malicious processes may use various system vulnerabilities to install on the system and stealthily execute without the user\'s consent.
We design and implement the Application Authentication (A2) framework that is capable of monitoring application executions and ensuring proper authentication of application processes. A2 has the advantage of strong security guarantees, efficient runtime execution, and compatibility with legacy applications. This authentication framework reduces the risk of infection by powerful malicious applications that may disrupt proper execution of legitimate applications, steal users\' private data, and spread across the entire organizational network.
Our process authentication model is extended and applied to the Android platform. As Android imposes its unique challenges (e.g., virtualized application execution model), our design and implementation of process authentication is extended to address these challenges. Per our results, process authentication in Android can protect the system against various critical vulnerabilities such as privilege escalation attacks and drive by downloads.
To demonstrate process authentication in Android, we implement DroidBarrier. As a runtime system, DroidBarrier includes an authentication component and a lightweight permission system to protect legitimate applications and secret authentication information in the file system. Our implementation of DroidBarrier is compatible with the Android runtime (with no need for modifications) and shows efficient performance with negligible penalties in I/O operations and process creations.
Ph. D.
27
Perry, Stanley Foster. „Distributed Economic Systems with Agents that Learn“. PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/1271.
Der volle Inhalt der QuelleAnnotation:
Economic systems are distributed in the sense that economic agents make decisions without any central control. Prices, quantities, wealth, and market structure emerge from the interaction of agents acting in their own self interest. The concepts and language of systems science are used to define economic systems in a manner that captures and articulates the distributed nature of economic systems. Further, the systems definition permits multiple views of the economic system, and in addition, allows the agents to "step outside" the system in order to study it. Economic systems are defined in such a way that it is feasible to construct artificial economic systems, and in particular, ones that are composed of self-interested agents that operate according to principles that are prescribed by the researcher. An artificial economic system was actually constructed and tested in a computer environment. The model was verified with reference to several theoretical models such as static and adaptive expectations. The system constructed allows up to 1000 agents to interact without any central control. A computer "blackboard system" is used as the architecture for providing common information to the agents in the artificial economic system. The blackboard design successfully allows complex agents to compete and trade in an artificial economic system created by the researcher. Prices, quantities, wealth, and market structure emerge naturally in the artificial economy that depend on the characteristics and prescribed strategies of the agents in the system. After a transition period, the trading frequently produces price and quantity time series that have the characteristics of a random walk, a condition that is well known in real world markets. Three classes of producer agents were used in these artificial economic systems: optimizing agents that incorporate neural networks, satisficing agents that incorporate very simple rule-based approaches, and Stackelberg agents that have knowledge about the consumers in the system, but do not have knowledge about their competitor's strategies or intentions. Neural networks are used to model the behavior and strategies of economic agents that can be said to learn, i.e., those agents that develop general principles for adapting to changing market conditions that transfer across markets. The focus of this research was on the producers in the system. The consumption side of the economic system was represented by a set of simple consumers. An important result emerging from this research is that at least one agent out of four in these experiments with accurate knowledge about market demand increases the wealth of the system as a whole. Markets containing a single Stackelberg or neural agent produced far more wealth than markets composed only of satisficing agents. However, the agents with knowledge do not necessarily capture the highest share of the wealth. The success of individual agents depends on the agent's trading strategy, as expected, and in addition depends on the combination of agents in the system. Certain strategies appeared to be flexible while others were brittle, and were easily foiled by changing the agents in the market, or by changing the market conditions. Earlier studies attempted to use neural networks to simulate an entire economic system, but were rejected because the organizing principles of the two systems are not analogous. Additionally, neural networks were successfully tested for solving various economics problems that were not related to the simulation of economic systems. Neural networks were found to effectively solve problems with missing and redundant data that are not directly solvable with well known methods such as least squares.
28
HAMMEL, STEPHEN MARK. „A DISSIPATIVE MAP OF THE PLANE--A MODEL FOR OPTICAL BISTABILITY (DYNAMICAL SYSTEMS)“. Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/188149.
Der volle Inhalt der QuelleAnnotation:
We analyze a dissipative map of the plane. The map was initially defined by Ikeda as a model for bistable behavior in an optical ring cavity. Our analysis is based upon an examination of attracting sets and basins of attraction. The primary tools utilized in the analysis are stable and unstable manifolds of fixed and periodic saddle points. These manifolds determine boundaries of basins of attraction, and the extent and evolution of attracting sets. We perform extensive numerical iterations of the map with a central focus on sudden changes in the topological nature of attractors and basins. Our analysis concentrates on the destruction of the lower branch attractor as a prominent example of attractor/basin interaction. This involves an examination of a possible link between two fixed points L and M, namely the heteroclinic connection Wᵘ(L) ∩ Wˢ(M) ≠ 0. We use two different methods to approach this question. Although the Ikeda map is used as the working model throughout, both of the techniques apply to a more general class of dissipative maps satisfying certain hypotheses. The first of these techniques analyzes Wˢ(M) when Wᵘ(M) ∩ Wˢ(M) ≠ 0, with the result that Wˢ(M) is found to invade some minimum limiting region for Wᵘ(M) ∩ Wˢ(M) ≠ 0 arbitrarily close to tangency. The second approach is more topological in nature. We define a mesh of subregions to bridge the spatial gap between the points L and M, and concentrate on the occurrence of Wᵘ(L) ∩ Wˢ(M) ≠ 0 (destruction of the attractor). The first main result is a necessary condition for the heteroclinic connection in terms of the behavior of the map on these subregions. The second result is a sequence of sufficient conditions for this link. There remains a gap between these two conditions, and in the final sections we present numerical investigations indicating that the concept of intersection links between subregions is useful to resolve cases near the boundary of the destruction region.
29
Luo, Yang. „Stochastic modelling in biological systems“. Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610145.
Der volle Inhalt der Quelle
30
Giannessi, Massimo <1982>. „Development of Clinical Decision Support Systems based on Mathematical Models of Physiological Systems“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2655/.
Der volle Inhalt der QuelleAnnotation:
In the last years of research, I focused my studies on different physiological problems. Together with my supervisors, I developed/improved different mathematical models in order to create valid tools useful for a better understanding of important clinical issues.
The aim of all this work is to develop tools for learning and understanding cardiac and cerebrovascular physiology as well as pathology, generating research questions and developing clinical decision support systems useful for intensive care unit patients.
I. ICP-model Designed for Medical Education
We developed a comprehensive cerebral blood flow and intracranial pressure model to simulate and study the complex interactions in cerebrovascular dynamics caused by multiple simultaneous alterations, including normal and abnormal functional states of auto-regulation of the brain.
Individual published equations (derived from prior animal and human studies) were implemented into a comprehensive simulation program. Included in the normal physiological modelling was: intracranial pressure, cerebral blood flow, blood pressure, and carbon dioxide (CO2) partial pressure. We also added external and pathological perturbations, such as head up position and intracranial haemorrhage.
The model performed clinically realistically given inputs of published traumatized patients, and cases encountered by clinicians. The pulsatile nature of the output graphics was easy for clinicians to interpret.
The manoeuvres simulated include changes of basic physiological inputs (e.g. blood pressure, central venous pressure, CO2 tension, head up position, and respiratory effects on vascular pressures) as well as pathological inputs (e.g. acute intracranial bleeding, and obstruction of cerebrospinal outflow).
Based on the results, we believe the model would be useful to teach complex relationships of brain haemodynamics and study clinical research questions such as the optimal head-up position, the effects of intracranial haemorrhage on cerebral haemodynamics, as well as the best CO2 concentration to reach the optimal compromise between intracranial pressure and perfusion.
We believe this model would be useful for both beginners and advanced learners. It could be used by practicing clinicians to model individual patients (entering the effects of needed clinical manipulations, and then running the model to test for optimal combinations of therapeutic manoeuvres).
II. A Heterogeneous Cerebrovascular Mathematical Model
Cerebrovascular pathologies are extremely complex, due to the multitude of factors acting simultaneously on cerebral haemodynamics.
In this work, the mathematical model of cerebral haemodynamics and intracranial pressure dynamics, described in the point I, is extended to account for heterogeneity in cerebral blood flow. The model includes the Circle of Willis, six regional districts independently regulated by autoregulation and CO2 reactivity, distal cortical anastomoses, venous circulation, the cerebrospinal fluid circulation, and the intracranial pressure-volume relationship.
Results agree with data in the literature and highlight the existence of a monotonic relationship between transient hyperemic response and the autoregulation gain. During unilateral internal carotid artery stenosis, local blood flow regulation is progressively lost in the ipsilateral territory with the presence of a steal phenomenon, while the anterior communicating artery plays the major role to redistribute the available blood flow. Conversely, distal collateral circulation plays a major role during unilateral occlusion of the middle cerebral artery.
In conclusion, the model is able to reproduce several different pathological conditions characterized by heterogeneity in cerebrovascular haemodynamics and can not only explain generalized results in terms of physiological mechanisms involved, but also, by individualizing parameters, may represent a valuable tool to help with difficult clinical decisions.
III. Effect of Cushing Response on Systemic Arterial Pressure.
During cerebral hypoxic conditions, the sympathetic system causes an increase in arterial pressure (Cushing response), creating a link between the cerebral and the systemic circulation.
This work investigates the complex relationships among cerebrovascular dynamics, intracranial pressure, Cushing response, and short-term systemic regulation, during plateau waves, by means of an original mathematical model.
The model incorporates the pulsating heart, the pulmonary circulation and the systemic circulation, with an accurate description of the cerebral circulation and the intracranial pressure dynamics (same model as in the first paragraph). Various regulatory mechanisms are included: cerebral autoregulation, local blood flow control by oxygen (O2) and/or CO2 changes, sympathetic and vagal regulation of cardiovascular parameters by several reflex mechanisms (chemoreceptors, lung-stretch receptors, baroreceptors). The Cushing response has been described assuming a dramatic increase in sympathetic activity to vessels during a fall in brain O2 delivery. With this assumption, the model is able to simulate the cardiovascular effects experimentally observed when intracranial pressure is artificially elevated and maintained at constant level (arterial pressure increase and bradicardia). According to the model, these effects arise from the interaction between the Cushing response and the baroreflex response (secondary to arterial pressure increase). Then, patients with severe head injury have been simulated by reducing intracranial compliance and cerebrospinal fluid reabsorption. With these changes, oscillations with plateau waves developed.
In these conditions, model results indicate that the Cushing response may have both positive effects, reducing the duration of the plateau phase via an increase in cerebral perfusion pressure, and negative effects, increasing the intracranial pressure plateau level, with a risk of greater compression of the cerebral vessels.
This model may be of value to assist clinicians in finding the balance between clinical benefits of the Cushing response and its shortcomings.
IV. Comprehensive Cardiopulmonary Simulation Model for the Analysis of Hypercapnic Respiratory Failure
We developed a new comprehensive cardiopulmonary model that takes into account the mutual interactions between the cardiovascular and the respiratory systems along with their short-term regulatory mechanisms.
The model includes the heart, systemic and pulmonary circulations, lung mechanics, gas exchange and transport equations, and cardio-ventilatory control.
Results show good agreement with published patient data in case of normoxic and hyperoxic hypercapnia simulations.
In particular, simulations predict a moderate increase in mean systemic arterial pressure and heart rate, with almost no change in cardiac output, paralleled by a relevant increase in minute ventilation, tidal volume and respiratory rate.
The model can represent a valid tool for clinical practice and medical research, providing an alternative way to experience-based clinical decisions.
In conclusion, models are not only capable of summarizing current knowledge, but also identifying missing knowledge. In the former case they can serve as training aids for teaching the operation of complex systems, especially if the model can be used to demonstrate the outcome of experiments. In the latter case they generate experiments to be performed to gather the missing data.
31
丘杰 und Jie Qiu. „Scheduling flexible manufacturing systems using fuzzy heuristics“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244671.
Der volle Inhalt der Quelle
32
Alparslan, Denizhan N. Sohraby Khosrow. „Modeling and analysis of generalized random mobility models for wireless ad hoc networks“. Diss., UMK access, 2005.
Den vollen Inhalt der Quelle findenAnnotation:
Thesis (Ph. D.)--School of Computing and Engineering. University of Missouri--Kansas City, 2005."A dissertation in telecommunication networking and computer networking." Advisor: Khosrow Sohraby. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed May 30, 2006. Includes bibliographical references (leaves 119-123). Online version of the print edition.
33
Doustmohammadi, Ali. „Modeling and analysis of production systems“. Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15776.
Der volle Inhalt der Quelle
34
Moi, Adriano. „Mathematical modelling of integrin-like receptors systems“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11255/.
Der volle Inhalt der QuelleAnnotation:
Nel presente lavoro, ho studiato e trovato le soluzioni esatte di un modello matematico applicato ai recettori cellulari della famiglia delle integrine. Nel modello le integrine sono considerate come un sistema a due livelli, attivo e non attivo. Quando le integrine si trovano nello stato inattivo possono diffondere nella membrana, mentre quando si trovano nello stato attivo risultano cristallizzate nella membrana, incapaci di diffondere. La variazione di concentrazione nella superficie cellulare di una sostanza chiamata attivatore dà luogo all’attivazione delle integrine.
Inoltre, questi eterodimeri possono legare una molecola inibitrice
con funzioni di controllo e regolazione, che chiameremo v, la quale, legandosi al recettore, fa aumentare la produzione della sostanza attizzatrice, che chiameremo u. In questo modo si innesca un meccanismo di retroazione positiva. L’inibitore v regola il meccanismo di produzione di u, ed assume, pertanto, il ruolo di modulatore. Infatti, grazie a questo sistema di fine regolazione il meccanismo di feedback positivo è in grado di autolimitarsi. Si costruisce poi un modello di equazioni differenziali partendo dalle semplici reazioni chimiche coinvolte.
Una volta che il sistema di equazioni è impostato, si possono desumere le soluzioni per le concentrazioni dell’inibitore e dell’attivatore per un caso particolare dei parametri. Infine, si può eseguire un test per vedere cosa predice il modello in termini di integrine. Per farlo, ho utilizzato un’attivazione del tipo funzione gradino e l’ho inserita nel sistema, valutando la dinamica dei recettori. Si ottiene in questo modo un risultato in accordo con le previsioni: le integrine legate si trovano soprattutto ai limiti della zona attivata, mentre le integrine libere vengono a mancare nella zona attivata.
35
Blanding, James Michael. „An analytical study and computer analysis of three-dimensional, steady-state vibration of multishaft geared-rotor systems“. Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/54198.
Der volle Inhalt der QuelleAnnotation:
A unique multifrequencied transfer matrix method performs three-dimensional harmonic, steady-state response calculations on geared-rotor systems. The full six degrees-of-freedom method includes physical branching to accommodate multiple shafting and frequency branching to simultaneously accommodate multiple frequencies and their interdependence resulting from time-varying mesh stiffness.
Areas of emphasis include development of a modified transfer matrix to handle multiple frequencies and shafting; description of the time-varying stiffness tensor representing the involute spur gear mesh based on bending, shear, compression, and local contact deformation; development of the mesh transfer matrix; development of an automatic system solver to allow the engineer to analyze systems of arbitrary construction; and the development of a matrix solver to efficiently handle large systems.
A computer analysis demonstrates the significance of terms included in the stiffness evaluation as compared with less rigorous treatment in the literature. An analytical example problem illustrates the automated model generation through complete rotor system dynamic response analysis produced by the current work with special attention to the significance of parametric excitation due to the gear mesh.Ph. D.
36
Min, Rui, und 闵瑞. „Channel estimation and data detection of OFDM systems under unknown channel order doppler frequency: from point-to-point to relaying systems“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47323930.
Der volle Inhalt der QuelleAnnotation:
Recently, there has been an increasing demand for OFDM system operating in
high mobility environment. In such situation, wireless channel is both
frequency-selective and time-varying, a.k.a. doubly-selective, making it hard for the
receiver to keep track of the channel state information (CSI). Moreover, the statistical
information of channel, e.g., tap positions, channel length, Doppler shifts and noise
power, is generally unknown to the receiver. In this thesis, two kinds of mobile
OFDM systems are investigated for data detection and channel estimation. Different
from previous works, which highly depend on the statistical information of the doubly
selective channel to deliver accurate channel estimation and data detection results, we
focus on more practical scenarios with unknown channel orders and Doppler
frequencies.
Firstly, point-to-point OFDM system with high mobility is considered. Due to
the unknown channel characteristics, we formulate the channel using GCE-BEM with
a large oversampling factor. The resulted GCE-BEM coefficients are sparse on
delay-Doppler domain and contain only a few nonzero elements. To enable the
identification of nonzero entries, sparsity enhancing Gaussian priors with Gamma
hyperpriors are adopted. An iterative algorithm is developed under variational
inference (VI) framework. The proposed algorithm iteratively estimate the channel,
recover the unknown data using Viterbi algorithm and learn the channel and noise
statistical information, using only limited number of pilot subcarrier in one OFDM
symbol.
Secondly, we investigate multihop amplify-and-forward (AF) OFDM system,
where system structure is generally unknown to the receiver due to the variable
number of hops and relaying paths in high mobility environment. We notice that in AF
relaying systems, the composite source-relay-destination channel is sufficient for data
detection. Then we integrate the multilink, multihop channel matrices into one
composite channel matrix, which turns out to have the same structure as the
point-to-point OFDM channel. The reformulated system model is more concise and a
similar iterative algorithm to that of the point-to-point case can be derived to estimate
the composite channel and detect data. This means that the proposed framework
applies to OFDM system under high mobility regardless of the system structure.
Simulation results show that the performance of the proposed algorithm is very
close to that of the optimal channel estimation and data detection algorithm, which
requires specific information of system structure, channel tap positions, channel
lengths, Doppler shifts as well as noise powers. It is worth noting that, the
close-to-ideal performance of the proposed algorithms is achieved with none of the
above information.published_or_final_version
Electrical and Electronic Engineering
Master
Master of Philosophy
37
Coburn, Brian John. „Multi-Species Influenza Models with Recombination“. Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/363.
Der volle Inhalt der QuelleAnnotation:
Avian influenza strains have been proven to be highly virulent in human populations, killing approximately 70 percent of infected individuals. Although the virus is able to spread across species from birds-to-humans, some strains, such as H5N1, have not been observed to spread from human-to-human. Pigs are capable of infection by both avian and human strains and seem to be likely candidates as intermediate hosts for co-infection of the inter-species strains. A co-infected pig potentially acts as a mixing vessel and could produce a new strain as a result of a recombination process. Humans could be immunologically naive to these new strains, hence making them super-strains. We propose an interacting host system (IHS) for such a process that considers three host species that interact by sharing strains; that is, a primary and secondary host species can both infect an intermediate host. When an intermediate host is co-infected with the strains from both the other hosts, co-infected individuals may become carriers of a super-strain back into the primary host population. The model is formulated as a classical susceptible-infectious-susceptible (SIS) model, where the primary and intermediate host species have a super-infection and co-infection with recombination structure, respectively. The intermediate host is coupled to the other host species at compartments of given infectious subclasses of the primary and secondary hosts. We use the model to give a new perspective for the trade-off hypothesis for disease virulence, by analyzing the behavior of a highly virulent super-strain. We give permanence conditions for a number of the subsystems of the IHS in terms of basic reproductive numbers of independent strains. We also simulate several relevant scenarios showing complicated dynamics and connections with epidemic forecasting.
38
Wan, Frank Lup Ki. „Genetic algorithms, their applications and models in nonlinear systems identification“. Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30107.
Der volle Inhalt der QuelleAnnotation:
The Genetic Algorithm was used to estimate the hydraulic compliance of the hydraulic system on the UBC teleoperated heavy duty excavator. Using real recorded and simulation data from the excavator, the Genetic Algorithm has successfully identified the compliance of single link and multi-link hydraulic system of the excavator.
A Parallel GA ( PGA ) was implemented with 16 T800 Transputers. It achieved a speedup factor of 12 over a traditional GA. With such a high speedup factor, real-time monitoring of hydraulic compliance and other hydraulic parameters is becoming possible.
New mechanisms such as the distributed fitness function, the active error analysis were used to enhance the performance of a PGA. A PGA which incorporated these mechanisms actually outperformed a traditional GA in key areas such as variance of the estimated parameter and parameter tracking ability.
Finally, a physical model that explains the fundamental properties of GAs was introduced. The physical model ( a hypercube ) not only provides an excellent explanation of GAs searching power, but also gives insight to GAs users ways to improve and to predict the performance of GAs in most applications.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
39
Hassanli, A. M. „Modelling and optimisation of pressure irrigation systems /“. Title page, abstract and contents only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phh353.pdf.
Der volle Inhalt der Quelle
40
Zhang, Wenjun. „Waves in mathematical models of intracellular calcium and other excitable systems“. Thesis, University of Auckland, 2011. http://hdl.handle.net/2292/14482.
Der volle Inhalt der QuelleAnnotation:
Oscillations in cytoplasmic calcium concentration are a crucial control mechanism in almost every cell type. Two important classes of oscillation are of particular interest: solitary and periodic waves. Both types of waves are commonly observed in physical experiments and found in mathematical models of calcium dynamics and other excitable systems. In this thesis, we try to understand these two classes of wave solutions. We first investigate wave solutions of the canonical excitable model, the FitzHugh-Nagumo (FHN) equations. We analyze the FHN equations using geometric singular perturbation theory and numerical integration, and find some new codimension-two organizing centres of the overall dynamics. Many analytical results about the FHN model in its classical form have already been established. We devise a transformation to change the form of the FHN equations we study into the classical form to make use of the results. This enables us to show how basic features of the bifurcation structure of the FHN equations arise from the singular limit. We then study waves of a representative calcium model. We analyze the dynamics of the calcium model in the singular limit, and show how homoclinic and Hopf bifurcations of the full system arise as perturbations of singular homoclinic and Hopf bifurcations. We compare the wave solutions in the FHN model and the calcium model, and show that the dynamics of the two models differ in some respects (most importantly, in the way in which diffusion enters the equations). We conclude that the FHN model should not uniformly be used as a prototypical model for calcium dynamics. Motivated by phenomena seen in the FHN and calcium models, we then investigate reduction techniques for excitable systems, including the quasi-steady state approximation and geometric singular perturbation theory, and show that criticality of Hopf bifurcations may be changed when applying these reduction methods to slow-fast biophysical systems. This suggests that great care should be taken when using reduction techniques such as these, to ensure that spurious conclusions about the dynamics of a model are not drawn from the dynamics of a reduced version of the model. Finally, we describe the class of numerical algorithms used to compute features of the detailed bifurcation sets for the FHN and calcium models, and show how these were used to locate a non-structurally stable heteroclinic connection between periodic orbits in a calcium model; this is the first time such a global bifurcation has been computed.
41
Gestrelius, Sara. „Mathematical models for optimising decision support systems in the railway industry“. Licentiate thesis, Mälardalens högskola, Inbyggda system, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-27758.
Der volle Inhalt der QuelleAnnotation:
After the deregulation of the Swedish railway industry, train operating companies compete for and on the same infrastructure. This makes the allocation of rail capacity a most delicate problem, and for a well-functioning railway system the allocation must be fair, efficient and functional. The capacity allocation tasks include e.g. constructing the yearly timetable and making track allocation plans for rail yards. The state of practice is that experienced planners construct the schedules manually with little or no decision support. However, as the planners are often faced with large combinatorial problems that are notoriously hard to solve there is a great potential in implementing optimising decision support systems. The research presented in this licentiate thesis aims at developing and examining mathematical models and methods that could be part of such support systems. The thesis focuses on two planning problems in particular, and the presented methods have been developed especially for the Swedish railway system. First of all, a model for optimising a train timetable with respect to robustness is presented. The model tries to increase the number of alternative meeting locations that can be used in a disturbed traffic situation and has an execution time of less than 5 minutes when solving the problem for the track section between Boden and Vännäs. Secondly, the problem of generating efficient classification bowl schedules for shunting yards is examined. The aim is to find the track allocation that minimises the number of required shunting movements while still respecting all operational, physical and time constraints imposed by the yard. Three optimisation models are presented, and simple planning rules are also investigated. The methods are tested on historic data from Hallsberg, the largest shunting yard in Sweden, and the results show that while the simple planning rules are not adequate for planning the classification bowl, two of the optimisation models consistently return an optimal solution within an acceptable execution time.
42
Ozcaldiran, Kadri. „Control of descriptor systems“. Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/13531.
Der volle Inhalt der Quelle
43
Nikishkov, Yuri G. „Computational stability analysis of dynamical systems“. Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/12149.
Der volle Inhalt der Quelle
44
Zhao, Ying, und 趙穎. „Optimization of cooperative material handling systems“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37837710.
Der volle Inhalt der Quelle
45
Wikström, Gunilla. „Computation of Parameters in some Mathematical Models“. Doctoral thesis, Umeå University, Computing Science, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-565.
Der volle Inhalt der QuelleAnnotation:
In computational science it is common to describe dynamic systems by mathematical models in forms of differential or integral equations. These models may contain parameters that have to be computed for the model to be complete. For the special type of ordinary differential equations studied in this thesis, the resulting parameter estimation problem is a separable nonlinear least squares problem with equality constraints. This problem can be solved by iteration, but due to complicated computations of derivatives and the existence of several local minima, so called short-cut methods may be an alternative. These methods are based on simplified versions of the original problem. An algorithm, called the modified Kaufman algorithm, is proposed and it takes the separability into account. Moreover, different kinds of discretizations and formulations of the optimization problem are discussed as well as the effect of ill-conditioning.
Computation of parameters often includes as a part solution of linear system of equations Ax = b. The corresponding pseudoinverse solution depends on the properties of the matrix A and vector b. The singular value decomposition of A can then be used to construct error propagation matrices and by use of these it is possible to investigate how changes in the input data affect the solution x. Theoretical error bounds based on condition numbers indicate the worst case but the use of experimental error analysis makes it possible to also have information about the effect of a more limited amount of perturbations and in that sense be more realistic. It is shown how the effect of perturbations can be analyzed by a semi-experimental analysis. The analysis combines the theory of the error propagation matrices with an experimental error analysis based on randomly generated perturbations that takes the structure of A into account
46
El, Didy Sherif Mohamed Ahmed 1951. „Two-dimensional finite element programs for water flow and water quality in multi-aquifer systems“. Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/191110.
Der volle Inhalt der QuelleAnnotation:
Multiple aquifer systems similar to those that exist at coal gasification sites are complicated groundwater situations. In these types of systems, the aquifers are separated by aquitards through which interaction between aquifers can occur. The movement of the products of combustion into the coal seam and adjacent aquifers is a serious problem of interest. This dissertation presents two-dimensional finite element models for water flow and water quality in multiple aquifer systems. These models can be applied for general problems as well as the problems associated with the burned cavities in coal gasification sites. The Galerkin weightedresidual method is used in both models. Eight-noded isoparametric elements are used. Spatial numerical integration is performed using Gaussian quadrature. A weighted finite difference scheme is used, in both of them, for time integration. The two models are written in FORTRAN V for the CDC CYBER 175. They are applicable to one- or two-dimensional problems involving steady-state or transient flow. Each aquifer can have different initial conditions and boundary conditions. Boundary conditions, pumping rates, and the recharge can be specified as a function of time. The output of the flow program-nodal heads and velocity components is used as an input to the quality program. The numerical models were validated for simple problems that have available analytical solutions.
47
Modarres, Najafabadi Seyed Ali. „Dynamics modelling and analysis of impact in multibody systems“. Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115886.
Der volle Inhalt der QuelleAnnotation:
In this thesis, we discuss a novel approach to the dynamics modelling and analysis of impact in unilaterally constrained multibody systems. This approach is based on an analysis of energy absorption and restitution during impact, using a decomposition technique, which decouples the kinetic energy associated with the spaces of admissible and constrained motions of unilateral contacts. This is done based on the decomposition of the tangent space of the configuration manifold at the pre-impact instant. The decomposition of the kinetic energy can provide a picture of how the energy absorption and dissipation during impact is related to the variation of the generalized velocities and the configuration of multibody systems.Further, based on the above analysis approach, we introduce a new interpretation of the energetic coefficient of restitution, specially applicable to contact involving multibody systems. This interpretation generalizes the concept of the energetic coefficient of restitution and allows for consideration of simultaneous multiple-point contact scenarios. Moreover, based on the concept of the generalized energetic coefficient of restitution, the contact modes and the post-impact state of planar single-point impact are determined. Further, the problem of simultaneous multiple-point impact is considered, where it is shown that our approach can also be advantageous to characterize the dynamics of interaction in such systems.
The use and applicability of the approach reported are further investigated by conducting an experimental study on a robotic testbed. The open architecture of the testbed allows us to perform various contact experiments, such as single- and multiple-point impact scenarios, with different pre-impact configurations and velocities. The kinematic and dynamic models of the system have been developed and implemented for real-time analysis. It is shown that impact between multibody systems is considerably affected by not only the local dynamics characteristics of the interacting bodies, but also the (global) configuration of the interacting multibody systems. The reported results suggest that the material presented herein offers a useful means to characterize impact in complex systems.
48
Tai, Hoi-lun Allen, und 戴凱倫. „Quantitative analysis in monitoring and improvement of industrial systems“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B4394193X.
Der volle Inhalt der Quelle
49
Chen, Mo. „Data compression for inference tasks in wireless sensor networks“. Diss., Online access via UMI:, 2006.
Den vollen Inhalt der Quelle findenAnnotation:
Thesis (Ph. D.)--State University of New York at Binghamton, Department of Electrical Engineering, Thomas J. Watson School of Engineering and Applied Science, 2006.Includes bibliographical references.
50
Clark, O. Grant (Osborne Grant). „Characterization of cyborged ecosystems“. Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36567.
Der volle Inhalt der QuelleAnnotation:
In this thesis, a philosophy and lexicon for the engineering of biosystems are established. The focus is on a specific class of biosystems ( ecocyborgs) created by combining ecosystems and technological Components. This work is part of the EcoCyborg Project, a highly interdisciplinary research program which concerns the development of a general theory for biosystems engineering, with an emphasis on system autonomy as a design goal. In the short term, the objective is to develop computational models and simulations for use in the study of ecocyborgs as representative instances of substantially autonomous biosystems. Accordingly, in this thesis an explicit conceptual basis is established for the EcoCyborg Project, as well as for biosystems engineering in general.First, in the body of the thesis, a biosystem is defined as a coherent assemblage of entities that is alive to some degree as a whole. The sole criterion for life is considered to be comportment that is somewhat autopoietic , whereby local interactions among the components combine to Continually renew the overall system. Next, concepts related to autonomy, or the formulation and pursuit of proprietary goals, are elaborated. The degree of autonomy of a system is seen to depend on its consciousness, or ability to reason using a model of itself. Hence, a substantially autonomous system requires an ensemble of information storage and processing devices (mind) of the type and sophistication (intelligence ) appropriate for this. The approach that is taken here to the creation of ecocyborgs with such minds is described, and a specific mental architecture is delineated, comprising functionally semidifferentiated, intermediate-scale components arranged according to a semihierarchical control organization. Finally, the characterization of such systems is scrutinized as an epistemic process in which knowledge is generated by an observer, but in which only a limited degree of objectivity is possible. A paradigm appropriate to the engineering of ecocyborgs is defined as an illustration, and associated archetypal concepts and descriptive procedures (such as measures) are given that are useful in this context. Such tools are required by significantly autonomous ecocyborgs because they must characterize themselves. They are also necessary to observers with scientific and engineering agendas.