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1
Toure, Almamy. "Collection, analysis and harnessing of communication flows for cyber-attack detection." Electronic Thesis or Diss., Valenciennes, Université Polytechnique Hauts-de-France, 2024. http://www.theses.fr/2024UPHF0023.
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La complexité croissante des cyberattaques, caractérisée par une diversification des techniques d'attaque, une expansion des surfaces d'attaque et une interconnexion croissante d'applications avec Internet, rend impérative la gestion du trafic réseau en milieu professionnel. Les entreprises de tous types collectent et analysent les flux réseau et les journaux de logs pour assurer la sécurité des données échangées et prévenir la compromission des systèmes d'information. Cependant, les techniques de collecte et de traitement des données du trafic réseau varient d'un jeu de données à l'autre, et les approches statiques de détection d'attaque présentent des limites d'efficacité et précision, de temps d'exécution et de scalabilité. Cette thèse propose des approches dynamiques de détection de cyberattaques liées au trafic réseau, en utilisant une ingénierie d'attributs basée sur les différentes phases de communication d'un flux réseau, couplée aux réseaux de neurones à convolution (1D-CNN) et leur feature detector. Cette double extraction permet ainsi une meilleure classification des flux réseau, une réduction du nombre d'attributs et des temps d'exécution des modèles donc une détection efficace des attaques. Les entreprises sont également confrontées à des cybermenaces qui évoluent constamment, et les attaques "zero-day", exploitant des vulnérabilités encore inconnues, deviennent de plus en plus fréquentes. La détection de ces attaques zero-day implique une veille technologique constante et une analyse minutieuse, mais coûteuse en temps, de l'exploitation de ces failles. Les solutions proposées garantissent pour la plupart la détection de certaines techniques d'attaque. Ainsi, nous proposons un framework de détection de ces attaques qui traite toute la chaîne d'attaque, de la phase de collecte des données à l'identification de tout type de zero-day, même dans un environnement en constante évolution. Enfin, face à l'obsolescence des jeux de données et techniques de génération de données existants pour la détection d'intrusion et à la nature figée, non évolutive, et non exhaustive des scénarios d'attaques récents, l'étude d'un générateur de données de synthèse adapté tout en garantissant la confidentialité des données est abordée. Les solutions proposées dans cette thèse optimisent la détection des techniques d'attaque connues et zero-day sur les flux réseau, améliorent la précision des modèles, tout en garantissant la confidentialité et la haute disponibilité des données et modèles avec une attention particulière sur l'applicabilité des solutions dans un réseau d'entrepriseThe increasing complexity of cyberattacks, characterized by a diversification of attack techniques, an expansion of attack surfaces, and growing interconnectivity of applications with the Internet, makes network traffic management in a professional environment imperative. Companies of all types collect and analyze network flows and logs to ensure the security of exchanged data and prevent the compromise of information systems. However, techniques for collecting and processing network traffic data vary from one dataset to another, and static attack detection approaches have limitations in terms of efficiency and precision, execution time, and scalability. This thesis proposes dynamic approaches for detecting cyberattacks related to network traffic, using feature engineering based on the different communication phases of a network flow, coupled with convolutional neural networks (1D-CNN) and their feature detector. This double extraction allows for better classification of network flows, a reduction in the number of attributes and model execution times, and thus effective attack detection. Companies also face constantly evolving cyber threats, and "zero-day" attacks that exploit previously unknown vulnerabilities are becoming increasingly frequent. Detecting these zero-day attacks requires constant technological monitoring and thorough but time-consuming analysis of the exploitation of these vulnerabilities. The proposed solutions guarantee the detection of certain attack techniques. Therefore, we propose a detection framework for these attacks that covers the entire attack chain, from the data collection phase to the identification of any type of zero-day, even in a constantly evolving environment. Finally, given the obsolescence of existing datasets and data generation techniques for intrusion detection, and the fixed, non-evolving, and non-exhaustive nature of recent attack scenarios, the study of an adapted synthetic data generator while ensuring data confidentiality is addressed. The solutions proposed in this thesis optimize the detection of known and zero-day attack techniques on network flows, improve the accuracy of models, while ensuring the confidentiality and high availability of data and models, with particular attention to the applicability of the solutions in a company network
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Izadinia, Vafa Dario. "Fingerprinting Encrypted Tunnel Endpoints." Diss., University of Pretoria, 2005. http://hdl.handle.net/2263/25351.
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Operating System fingerprinting is a reconnaissance method used by Whitehats and Blackhats alike. Current techniques for fingerprinting do not take into account tunneling protocols, such as IPSec, SSL/TLS, and SSH, which effectively `wrap` network traffic in a ciphertext mantle, thus potentially rendering passive monitoring ineffectual. Whether encryption makes VPN tunnel endpoints immune to fingerprinting, or yields the encrypted contents of the VPN tunnel entirely indistinguishable, is a topic that has received modest coverage in academic literature. This study addresses these question by targeting two tunnelling protocols: IPSec and SSL/TLS. A new fingerprinting methodology is presented, several fingerprinting discriminants are identified, and test results are set forth, showing that endpoint identities can be uncovered, and that some of the contents of encrypted VPN tunnels can in fact be discerned.Dissertation (MSc (Computer Science))--University of Pretoria, 2005.
Computer Science
unrestricted
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Heller, Mark D. "Behavioral analysis of network flow traffic." Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/5108.
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Approved for public release, distribution unlimitedNetwork Behavior Analysis (NBA) is a technique to enhance network security by passively monitoring aggregate traffic patterns and noting unusual action or departures from normal operations. The analysis is typically performed offline, due to the huge volume of input data, in contrast to conventional intrusion prevention solutions based on deep packet inspection, signature detection, and real-time blocking. After establishing a benchmark for normal traffic, an NBA program monitors network activity and flags unknown, new, or unusual patterns that might indicate the presence of a potential threat. NBA also monitors and records trends in bandwidth and protocol use. Computer users in the Department of Defense (DoD) operational networks may use Hypertext Transport Protocol (HTTP) to stream video from multimedia sites like youtube.com, myspace.com, mtv.com, and blackplanet.com. Such streaming may hog bandwidth, a grave concern, given that increasing amounts of operational data are exchanged over the Global Information Grid, and introduce malicious viruses inadvertently. This thesis develops an NBA solution to identify and estimate the bandwidth usage of HTTP streaming video traffic entirely from flow records such as Cisco's NetFlow data.
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McClenney, Walter O. "Analysis of the DES, LOKI, and IDEA algorithms for use in an encrypted voice PC network." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA297919.
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Kattadige, Chamara Manoj Madarasinghe. "Network and Content Intelligence for 360 Degree Video Streaming Optimization." Thesis, The University of Sydney, 2023. https://hdl.handle.net/2123/29904.
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In recent years, 360° videos, a.k.a. spherical frames, became popular among users
creating an immersive streaming experience. Along with the advances in smart-
phones and Head Mounted Devices (HMD) technology, many content providers
have facilitated to host and stream 360° videos in both on-demand and live stream-
ing modes. Therefore, many different applications have already arisen leveraging
these immersive videos, especially to give viewers an impression of presence in a
digital environment. For example, with 360° videos, now it is possible to connect
people in a remote meeting in an interactive way which essentially increases the
productivity of the meeting. Also, creating interactive learning materials using
360° videos for students will help deliver the learning outcomes effectively.
However, streaming 360° videos is not an easy task due to several reasons. First,
360° video frames are 4–6 times larger than normal video frames to achieve the
same quality as a normal video. Therefore, delivering these videos demands higher
bandwidth in the network. Second, processing relatively larger frames requires
more computational resources at the end devices, particularly for end user devices
with limited resources. This will impact not only the delivery of 360° videos but
also many other applications running on shared resources. Third, these videos need
to be streamed with very low latency requirements due their interactive nature.
Inability to satisfy these requirements can result in poor Quality of Experience
(QoE) for the user. For example, insufficient bandwidth incurs frequent rebuffer-
ing and poor video quality. Also, inadequate computational capacity can cause
faster battery draining and unnecessary heating of the device, causing discomfort
to the user. Motion or cyber–sickness to the user will be prevalent if there is an
unnecessary delay in streaming. These circumstances will hinder providing im-
mersive streaming experiences to the much-needed communities, especially those
who do not have enough network resources.
To address the above challenges, we believe that enhancements to the three main
components in video streaming pipeline, server, network and client, are essential.
Starting from network, it is beneficial for network providers to identify 360° video
flows as early as possible and understand their behaviour in the network to effec-
tively allocate sufficient resources for this video delivery without compromising the
quality of other services. Content servers, at one end of this streaming pipeline, re-
quire efficient 360° video frame processing mechanisms to support adaptive video streaming mechanisms such as ABR (Adaptive Bit Rate) based streaming, VP
aware streaming, a streaming paradigm unique to 360° videos that select only
part of the larger video frame that fall within the user-visible region, etc. On the
other end, the client can be combined with edge-assisted streaming to deliver 360°
video content with reduced latency and higher quality.
Following the above optimization strategies, in this thesis, first, we propose a mech-
anism named 360NorVic to extract 360° video flows from encrypted video traffic
and analyze their traffic characteristics. We propose Machine Learning (ML) mod-
els to classify 360° and normal videos under different scenarios such as offline, near
real-time, VP-aware streaming and Mobile Network Operator (MNO) level stream-
ing. Having extracted 360° video traffic traces both in packet and flow level data
at higher accuracy, we analyze and understand the differences between 360° and
normal video patterns in the encrypted traffic domain that is beneficial for effec-
tive resource optimization for enhancing 360° video delivery. Second, we present
a WGAN (Wesserstien Generative Adversarial Network) based data generation
mechanism (namely VideoTrain++) to synthesize encrypted network video traffic,
taking minimal data. Leveraging synthetic data, we show improved performance
in 360° video traffic analysis, especially in ML-based classification in 360NorVic.
Thirdly, we propose an effective 360° video frame partitioning mechanism (namely
VASTile) at the server side to support VP-aware 360° video streaming with dy-
namic tiles (or variable tiles) of different sizes and locations on the frame. VASTile
takes a visual attention map on the video frames as the input and applies a com-
putational geometric approach to generate a non-overlapping tile configuration to
cover the video frames adaptive to the visual attention. We present VASTile as a
scalable approach for video frame processing at the servers and a method to re-
duce bandwidth consumption in network data transmission. Finally, by applying
VASTile to the individual user VP at the client side and utilizing cache storage
of Multi Access Edge Computing (MEC) servers, we propose OpCASH, a mech-
anism to personalize the 360° video streaming with dynamic tiles with the edge
assistance. While proposing an ILP based solution to effectively select cached
variable tiles from MEC servers that might not be identical to the requested VP
tiles by user, but still effectively cover the same VP region, OpCASH maximize
the cache utilization and reduce the number of requests to the content servers in
congested core network. With this approach, we demonstrate the gain in latency
and bandwidth saving and video quality improvement in personalized 360° video
streaming.
6
Dandachi, Najib H. "Network flow method for power system analysis." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47398.
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Martin, Kevin M. "A geographic and functional network flow analysis tool." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/42679.
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Approved for public release; distribution is unlimitedCritical infrastructure systems, such as water and electricity, are important for society and national defense. There is a need for network analysis tools that allow analysts to study potential scenarios to discover vulnerabilities, assess consequences, and evaluate effective solutions to overcome network weaknesses. In order to be useful, models of critical infrastructure systems need to be realistic, both geospatially and functionally. The objective of this thesis is to bridge the gap between geospatial and functional network analysis by developing a software tool that allows users to create and edit networks in a Graphical Information System (GIS) visual environment, and then also run and view the results of functional network models. Our primary contribution is to provide an easy-to-use, graphical interface in the form of a plugin that allows users, regardless of their network expertise, to create networks and exercise network flow models on them. We demonstrate the usefulness of our plugin through the analysis of a fictional case study with a realistic Internet infrastructure. We run several minimum cost flow models with simulated network attacks to assess the robustness of the network.
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Zickel, Michael J. "Using ecosystem network analysis to quantify fluid flow." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2987.
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Thesis (M.S.) -- University of Maryland, College Park, 2005.Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Herbert, Alan. "Bolvedere: a scalable network flow threat analysis system." Thesis, Rhodes University, 2019. http://hdl.handle.net/10962/71557.
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Since the advent of the Internet, and its public availability in the late 90’s, there have been significant advancements to network technologies and thus a significant increase of the bandwidth available to network users, both human and automated. Although this growth is of great value to network users, it has led to an increase in malicious network-based activities and it is theorized that, as more services become available on the Internet, the volume of such activities will continue to grow. Because of this, there is a need to monitor, comprehend, discern, understand and (where needed) respond to events on networks worldwide. Although this line of thought is simple in its reasoning, undertaking such a task is no small feat. Full packet analysis is a method of network surveillance that seeks out specific characteristics within network traffic that may tell of malicious activity or anomalies in regular network usage. It is carried out within firewalls and implemented through packet classification. In the context of the networks that make up the Internet, this form of packet analysis has become infeasible, as the volume of traffic introduced onto these networks every day is so large that there are simply not enough processing resources to perform such a task on every packet in real time. One could combat this problem by performing post-incident forensics; archiving packets and processing them later. However, as one cannot process all incoming packets, the archive will eventually run out of space. Full packet analysis is also hindered by the fact that some existing, commonly-used solutions are designed around a single host and single thread of execution, an outdated approach that is far slower than necessary on current computing technology. This research explores the conceptual design and implementation of a scalable network traffic analysis system named Bolvedere. Analysis performed by Bolvedere simply asks whether the existence of a connection, coupled with its associated metadata, is enough to conclude something meaningful about that connection. This idea draws away from the traditional processing of every single byte in every single packet monitored on a network link (Deep Packet Inspection) through the concept of working with connection flows. Bolvedere performs its work by leveraging the NetFlow version 9 and IPFIX protocols, but is not limited to these. It is implemented using a modular approach that allows for either complete execution of the system on a single host or the horizontal scaling out of subsystems on multiple hosts. The use of multiple hosts is achieved through the implementation of Zero Message Queue (ZMQ). This allows for Bolvedre to horizontally scale out, which results in an increase in processing resources and thus an increase in analysis throughput. This is due to ease of interprocess communications provided by ZMQ. Many underlying mechanisms in Bolvedere have been automated. This is intended to make the system more userfriendly, as the user need only tell Bolvedere what information they wish to analyse, and the system will then rebuild itself in order to achieve this required task. Bolvedere has also been hardware-accelerated through the use of Field-Programmable Gate Array (FPGA) technologies, which more than doubled the total throughput of the system.
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Glockner, Gregory D. "Dynamic network flow with uncertain arc capacities." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/30734.
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Huang, Henna Priscilla. "Hybrid flow data center network architecture design and analysis." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108998.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 127-132).
In this thesis, we propose a hybrid flow network architecture for future data center. The hybrid flow architecture has its origins in the early 1990s with studies on all-optical networks and fiber-optical computer networks. Research in optical flow switching has spanned over two decades. Our contribution to the study of all-optical networks is on the performance of hybrid flow data center networks. We compare the delay performance of hybrid flow architectures and traditional packet switched networks in future data center. We present a simplified data center traffic model, where data center traffic is categorized into mice traffic and elephant flows. The electronic packet switched architecture allows for low overhead and complexity for small transactions. However, mice traffic suffers as the size, fraction, and arrival rates of elephant flows increase. In the hybrid flow architecture, elephant flows are transmitted on an all-optical flow-switched data plane, where wavelength channels are reserved for the duration of a flow. In addition, the hybrid flow architecture allows for the dynamic allocation of optical wavelengths. In electronic packet switched networks, wavelength assignments are static, where traditional networking protocols do not consider the optical domain in routing decisions. We show that the hybrid flow architecture allows for superior delay performance compared to the electronic packet switched architecture as data rates and data volume increase in future data center networks.
by Henna Huang.
Ph. D.
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Wang, Shentao. "Supply chain planning using network flow optimization." online access from Digital Dissertation Consortium access full-text, 2003. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?MQ89164.
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Cassir, C. "A flow model for the analysis of transport network reliability." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364764.
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Lam, Yan-yan, and 林欣欣. "Algorithms for the minimum cost flow problem." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30246052.
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NOGUEIRA, GIOVANE BARROSO LIMA. "ANALYSIS OF EMULSION FLOW THROUGH POROUS MEDIA USING CAPILLARY NETWORK MODEL." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=18104@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEmulsões podem ser utilizadas como agentes de controle de mobilidade em diferentes processos de recuperação melhorada de petróleo e armazenamento de carbono em reservatórios porosos. A aplicação desta técnica, com a escolha correta das características das emulsões injetadas e a determinação das condições de operação ótimas, requer um entendimento adequado do escoamento de emulsões em meios porosos. As características macroscópicas do fluxo de emulsões através de meios porosos estão diretamente ligadas ao escoamento bifásico na escala de poros. Modelos de rede de capilares permitem a implementação dos mecanismos de fluxo das gotas nas gargantas de poros e fornecem parâmetros macroscópicos do escoamento. Neste trabalho, o escoamento de emulsões em meios porosos é analisado através de um modelo dinâmico de rede de capilares tridimensional e não-estruturada. A distribuição de pressão nos poros, e consequentemente o fluxo em cada capilar da rede, é determinada pelo balanço de massa em cada poro. O efeito das gotas da fase dispersa no comportamento do escoamento em cada elemento da rede é descrito por um fator de bloqueio de fluxo baseado em resultados experimentais de escoamento de emulsões através de micro capilares com gargantas. O fator de bloqueio descreve a mudança da condutividade de cada elemento e é uma função da geometria da garganta, do tamanho e concentração volumétrica da fase dispersa e do número de capilaridade local. A distribuição de concentração da fase dispersa ao longo da rede é descrita através de uma equação de transporte de massa, permitindo assim o estudo do processo de filtragem de gotas nos poros e o estudo da injeção alternada de água e emulsão. A integração no tempo do modelo dinâmico é feita por um método semi-implícito e o sistema de equações não linear obtido a cada passo de tempo é resolvido através de um método iterativo. Os resultados apresentam a evolução da redução da permeabilidade e concentração de gotas na saída do meio poroso em função do tamanho das gotas, da vazão de injeção, da concentração da emulsão injetada e do volume injetado de emulsão. A análise da injeção alternada de água-emulsão mostra claramente o bloqueio de poros por gotas da emulsão e a alteração no padrão de escoamento após reiniciada a injeção de água.
Emulsions can be used as mobility control agents in different enhanced oil recovery and carbon storage methods in oil reservoirs. The application of this technique, with the correct choice of the injected emulsion characteristics and the determination of optimal operating conditions, requires an adequate understanding of the emulsion flow in porous media. The macroscopic characteristics of the emulsion flow through porous media are directly linked to the two-phase flow at the pore scale. Capillary network models allow the implementation of the drop flow mechanisms in the pore throats and the determination of macroscopic flow parameters. In this work, emulsion flow in porous media is analyzed through an unstructured 3D dynamic network model. The pressure distribution, and consequently the flow rate in each capillary of the network, isdetermined by mass balance equation in each pore. The effects of the drops of dispersed phase in the flow behavior within each element of the network is described by a flow blocking factor based on experimental results on emulsion flow through single microcapillary tubes with throats. The blocking factor describes the changes in the conductivity of each element and it is a function of the throat geometry, the size and volumetric concentration of the dispersed phase and the local capillary number. The concentration distribution of the dispersed phase along the network is described by a mass transport equation, allowing the study of the filtration process of the drops in the pores and the analysis of the alternate injection of water and emulsion.Time integration in the dynamic model is performed by a semi-implicit method and the non-linear system of equations obtained in each time step is solved by an iterative method. The results illustrate the evolution of the permeability reduction and the effluent concentration of drops as a function of the drops size, injection flow rate, concentration of the injected emulsion and injected volume of emulsion. The analysis of the emulsion/water alternate injection clearly shows the pore blockage by the emulsion drops and the change in the flow pattern after the reinjection of water.
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PISA, GIULIA. "Evaluation of ecological network effectiveness by means of gene flow analysis." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2014. http://hdl.handle.net/10281/51785.
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The aim of this project is to study the fragmentation in broad-leaved forests, so the species selected were mainly linked to this ecosystem. Almost all amphibian species are model candidates for studies of fragmentation effects on connectivity: in fact most amphibian species occur as metapopulations; in addition, they are a taxon particularly susceptible to isolation, as they generally have low dispersal capabilities and are rather philopatric to breeding sites. These characteristics often lead to high genetic differentiation, even at restricted scales. In particular we choose the Fire Salamander (Salamandra salamandra, AMPHIBIA, URODELA) that is strongly linked to broad-leaved forest ecosystems, depends on ecosystem processes (such as those that allow the development of an adequate litter structure); is strongly affected by specific resources (such as hydrology, some chemical and physical water parameters); and it is also limited by a low dispersal capability.
However not only amphibian species are affected by habitat fragmentation, also arboreal mammals, such tree squirrels and dormice, are often more threatened than other species due to their low dispersal capability in absence of structural connection between habitat patches. In European regions, various single-species studies have been carried out, suggesting similar responses in this guild of mammals. Among them, the Hazel Dormouse (Muscardinus avellanarius, RODENTIA, GLIRIDAE) is an arboreal rodent living in woodland and hedgerows, whose presence is negatively affected by fragmentation. For its poor conservation status and negative long-term trend in almost all Europe, the species is included in the Annex IV of the 92/43/ECC Directive (Habitat Directive), concerning species that require a strict protection regime that must be applied across their entire natural range within the EU. For this reason we sampled also the Hazel Dormouse that can be defined as a focal species sensu Lambeck (1997) at least for three out four ecological traits (they are limited by resources, dispersal capability, and ecological processes). We choose two different areas of study, both affected by the habitat fragmentation: Lombardy Region (Northern Italy, where we worked on the Fire Salamander), and Latium Region (central Italy, where we sampled the Dormouse). In both regions we sampled a fragmented forest area and a continuous one, our control.
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Zhang, Pengfei, and Neng Fan. "Analysis of budget for interdiction on multicommodity network flows." Springer, 2016. http://hdl.handle.net/10150/623040.
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In this paper, we concentrate on computing several critical budgets for interdiction of the multicommodity network flows, and studying the interdiction effects of the changes on budget. More specifically, we first propose general interdiction models of the multicommodity flow problem, with consideration of both node and arc removals and decrease of their capacities. Then, to perform the vulnerability analysis of networks, we define the function F(R) as the minimum amount of unsatisfied demands in the resulted network after worst-case interdiction with budget R. Specifically, we study the properties of function F(R), and find the critical budget values, such as , the largest value under which all demands can still be satisfied in the resulted network even under the worst-case interdiction, and , the least value under which the worst-case interdiction can make none of the demands be satisfied. We prove that the critical budget for completely destroying the network is not related to arc or node capacities, and supply or demand amounts, but it is related to the network topology, the sets of source and destination nodes, and interdiction costs on each node and arc. We also observe that the critical budget is related to all of these parameters of the network. Additionally, we present formulations to estimate both and . For the effects of budget increasing, we present the conditions under which there would be extra capabilities to interdict more arcs or nodes with increased budget, and also under which the increased budget has no effects for the interdictor. To verify these results and conclusions, numerical experiments on 12 networks with different numbers of commodities are performed.
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Feinauer, Lynn Ralph. "Generic Flow Algorithm for Analysis of Interdependent Multi-Domain Distributed Network Systems." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/40010.
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Since the advent of the computer in the late 1950s, scientists and engineers have pushed the limits of the computing power available to them to solve physical problems via computational simulations. Early computer languages evaluated program logic in a sequential manner, thereby forcing the designer to think of the problem solution in terms of a sequential process.
Object-oriented analysis and design have introduced new concepts for solving systems of engineering problems. The term object-oriented was first introduced by Alan Kay [1] in the late 1960s; however, mainstream incorporation of object-oriented programming did not occur until the mid- to late 1990s. The principles and methods underlying object-oriented programming center around objects that communicate with one another and work together to model the physical system. Program functions and data are grouped together to represent the objects.
This dissertation extends object-oriented modeling concepts to model algorithms in a generic manner for solving interconnected, multi-domain problems. This work is based on an extension of Graph Trace Analysis (GTA) which was originally developed in the 1990â s for power distribution system design. Because of GTAâ s ability to combine and restructure analysis methodologies from a variety of problem domains, it is now being used for integrated power distribution and transmission system design, operations and control. Over the last few years research has begun to formalize GTA into a multidiscipline approach that uses generic algorithms and a common model-based analysis framework. This dissertation provides an overview of the concepts used in GTA, and then discusses the main problems and potential generic algorithm based solutions associated with design and control of interdependent reconfigurable systems. These include:
â ¢ Decoupling analysis into distinct component and system level equations.
â ¢ Using iterator based topology management and algorithms instead of matrices.
â ¢ Using composition to implement polymorphism and simplify data management.
â ¢ Using dependency components to structure analysis across different systems types.
â ¢ Defining component level equations for power, gas and fluid systems in terms of across and though variables.
This dissertation presents a methodology for solving interdependent, multi-domain networks with generic algorithms. The methodology enables modeling of very large systems and the solution of the systems can be accomplished without the need for matrix solvers. The solution technique incorporates a binary search algorithm for accelerating the solution of looped systems. Introduction of generic algorithms enables the system solver to be written such that it is independent of the system type. Example fluid and electrical systems are solved to illustrate the generic nature of the approach.Ph. D.
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Azab, Ahmad. "Classification of network information flow analysis (CONIFA) to detect new application versions." Thesis, Federation University Australia, 2015. http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/97576.
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Monitoring network traffic to identify applications or services is vital for internet service providers, network engineers and law enforcement agencies. The identification of applications enables network traffic to be prioritized, sophisticated plans for network infrastructure to be developed and facilitates the work of law enforcement agencies. Voice over IP (VoIP) and malware services are important to be classified because of the reliance by both legitimate users and cybercriminals respectively on these services. This dissertation addresses the detection of these services, represented by Skype application voice calls traffic and Zeus application command and control traffic. Three major approaches have been used to fulfil the classification goal, which are port-based, deep packet inspection and the use of the statistical features in conjunction with the machine learning algorithms. The latter approach addressed many of the limitations of the first two. However, the existing approach still contains many limitations. The detection of new versions by analysing and building the classifier on an old version was not deeply discussed for the machine learning approach. However, not all the statistical values are similar for different versions for Skype voice calls and Zeus command and control traffic. This is because Skype uses different codecs for different versions and Zeus uses different malware builders for different versions. While some approaches, aside from the machine learning approach, tackled the detection of the different versions, none of them maintain all the characteristics supported by the machine learning approach in terms of providing online classification capability and supporting various transport and application protocols, without the need to access different device’s traffic, access packet’s content or monitor different phase’s traffic. This research study aims to tackle this gap by proposing a novel framework called Classification of Network Information Flow Analysis (CONIFA). CONIFA addresses the detection of different untrained versions for a targeted application (Skype voice calls and Zeus command and control traffic) with a low detection time by analysing and building the classifier on a different single version in a systematic and well-defined approach, providing online classification capability and supporting various transport and application protocols, without the need to access different device’s traffic, access packet’s content or monitor different phase’s traffic. CONIFA is not limited to a specific application and could be extended to other types of applications. CONIFA utilizes the concepts of cost sensitive algorithms and different feature combinations for building the classifiers, unlike the machine learning approach that utilizes cost insensitive algorithms and a single feature combination. The outputs of the first phase are two classifiers, lenient and strict, that are used by the next phase to detect the untrained versions of a targeted application as well as to reduce the error rate. CONIFA results, for detecting the untrained version of Skype voice calls and Zeus C&C traffic, supported this approach in providing a better detection performance compared to the previous approach. While the previous approach was not able to reliably detect new versions of VoIP, CONIFA was able to consistently detect a previously unseen version. For the botnet detection, the previous approach had a good efficacy at the network level. However, CONIFA outperformed this approach in detecting a new version of a known piece of malware.Doctor of Philosophy
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Chong, Yew Chuan. "Thermal analysis and air flow modelling of electrical machines." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10466.
Full textAbstract:
Thermal analysis is an important topic that can affect the electrical machine performance, reliability, lifetime and efficiency. In order to predict the electrical machine thermal performance accurately, thermal analysis of electrical machines must include fluid flow modelling. One of the technologies which may be used to estimate the flow distribution and pressure losses in throughflow ventilated machines is flow network analysis, but suitable correlations that can be used to estimate the pressure losses in rotor ducts due to fluid shock is not available. The aim of this work is to investigate how the rotation affects the pressure losses in rotor ducts by performing a dimensional analysis. Apart from the additional friction loss due to the effects of rotation, other rotational pressure losses that appear in a rotor-stator system are: duct entrance loss due to fluid shock and combining flow loss at the exit of the rotor-stator gap. These losses are analysed using computational fluid dynamics (CFD) methods. The CFD simulations use the Reynolds-averaged Navier Stokes (RANS) approach. An experimental test rig is built to validate the CFD findings. The investigation showed that the CFD results are consistent with the experimental results and the rotational pressure losses correlate well with the rotation ratio (a dimensionless parameter). It shows that the rotational pressure loss generally increases with the increase in the rotation ratio. At certain operating conditions, the rotational pressure loss can contribute over 50 % of the total system loss. The investigation leads to an original set of correlations for the pressure losses in air ducts in the rotor due to fluid shock which are more suitable to be applied to fluid flow modelling of throughflow ventilated machines. Such correlations provide a significant contribution to the field of thermal modelling of electrical machines. They are incorporated into the air flow modelling tool that has been programmed in Portunus by the present author. The modelling tool can be integrated with the existing thermal modelling method, lumped-parameter thermal network (LPTN) to form a complete analytical thermal-fluid modelling method.
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Brown, Douglas Graeme. "Formal network behaviour analysis using model checking." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/93693/1/Douglas_Brown_Thesis.pdf.
Full textAbstract:
In this research we modelled computer network devices to ensure their communication behaviours meet various network standards. By modelling devices as finite-state machines and examining their properties in a range of configurations, we discovered a flaw in a common network protocol and produced a technique to improve organisations' network security against data theft.
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Liu, Dan. "Computational analysis of blood flow and oxygen transport in the retinal arterial network." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6033.
Full textAbstract:
Pathological changes in retinal microvasculature are known to be associated with systemic diseases such as hypertension and diabetes, and may result in potentially disadvantageous blood flow and impair oxygen distribution. Therefore, in order to improve our understanding of the link between systemic diseases and the retinal circulation, it is necessary to develop an approach to quantitatively determine the hemodynamic and oxygen transport parameters in the retinal vascular circulation. This thesis aims to provide more insights into the detailed hemodynamic features of the retinal arterial tree by means of non-invasive imaging and computational modelling. It covers the following two aspects: i) 3D reconstruction of the retinal arterial tree, and ii) development of an image-based computational model to predict blood flow and oxygen transport in realistic subject-specific retinal arterial trees. The latter forms the main body of the thesis. 3D reconstruction of the retinal arterial tree was performed based on retinal images acquired in vivo with a fundus camera and validated using a simple 3D object. The reproduction procedure was found to be feasible but with limited accuracy. In the proposed 2D computational model, the smaller peripheral vessels indistinguishable from the retinal images were represented by self-similar asymmetric structured trees. The non-Newtonian properties of blood, and nonlinear oxyhemoglobin dissociation in the red blood cells and plasma were considered. The simulation results of the computational model were found in good agreement with in vivo measurements reported in the literature. In order to understand the effect of retinal vascular structure on blood flow and oxygen transport, the computational model was applied to subject-specific geometries for a number of hypertensive and diabetic patients, and comparisons were made with results obtained from healthy retinal arterial networks. Moreover, energy analysis of normal and hypertensive subjects was performed using 3D hypothetical models. Finally, the influence of different viscosity models on flow and oxygen transport in a retinal tree and the advantage of low dimensional models were examined. This study has demonstrated the applicability of the image-based computational modelling to study the hemodynamics and oxygen distribution in the retinal arterial network.
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Gülpinar, Nalân. "Analysis of large scale linear programming problems with embedded network structures : detection and solution algorithms." Thesis, Brunel University, 1998. http://bura.brunel.ac.uk/handle/2438/7123.
Full textAbstract:
Linear programming (LP) models that contain a (substantial) network structure frequently arise in many real life applications. In this thesis, we investigate two main questions; i) how an embedded network structure can be detected, ii) how the network structure can be exploited to create improved sparse simplex solution algorithms. In order to extract an embedded pure network structure from a general LP problem we develop two new heuristics. The first heuristic is an alternative multi-stage generalised upper bounds (GUB) based approach which finds as many GUB subsets as possible. In order to identify a GUB subset two different approaches are introduced; the first is based on the notion of Markowitz merit count and the second exploits an independent set in the corresponding graph. The second heuristic is based on the generalised signed graph of the coefficient matrix. This heuristic determines whether the given LP problem is an entirely pure network; this is in contrast to all previously known heuristics. Using generalised signed graphs, we prove that the problem of detecting the maximum size embedded network structure within an LP problem is NP-hard. The two detection algorithms perform very well computationally and make positive contributions to the known body of results for the embedded network detection. For computational solution a decomposition based approach is presented which solves a network problem with side constraints. In this approach, the original coefficient matrix is partitioned into the network and the non-network parts. For the partitioned problem, we investigate two alternative decomposition techniques namely, Lagrangean relaxation and Benders decomposition. Active variables identified by these procedures are then used to create an advanced basis for the original problem. The computational results of applying these techniques to a selection of Netlib models are encouraging. The development and computational investigation of this solution algorithm constitute further contribution made by the research reported in this thesis.
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Haiba, Mohamed Salem. "A study and implementation of the network flow problem and edge integrity of networks." Virtual Press, 1991. http://liblink.bsu.edu/uhtbin/catkey/834644.
Full textAbstract:
Fundamental problems in graph theory are of four types existence, construction, enumeration and optimization problems. Optimization problems lie at the interface between computer science and the field of operations research and are of primary importance in decision-making. In this thesis, two optimization problems are studied: the edge-integrity of networks and the network flow problem. An implementation of the corresponding algorithms is also realized.The edge integrity of a communication network provides a way to assess the vulnerability of the network to disruption through the destruction or failure of some of its links. While the computation of the edge-integrity of graphs in general has been proven to be NPcomplete, a recently published paper was devoted to a good algorithm using a technique of edge separation sequence for computing the edge integrity of trees. The main results of this paper will be presented and an implementation of this algorithm is achieved.The network flow problem models a distribution system in which commodities are flowing through an interconnected network. The goal is to find a maximum feasible flow and its value, given the capacity constraints for each edge. The three majors algorithms for this problem (Ford -Fulkerso n, Edmonds-Karp method, MPKM algorithm) are discussed, their complexities compared and an implementation of the Ford-Fulkerson and the MPKM algorithms is presented.Department of Computer Science
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Pretorius, Johannes Jacobus. "A network approach for the prediction of flow and flow splits within a gas turbine combustor." Diss., University of Pretoria, 2005. http://hdl.handle.net/2263/26712.
Full textAbstract:
The modern gas turbine engine industry needs a simpler and faster method to facilitate the design of gas turbine combustors due to the enormous costs of experimental test rigging and detailed computational fluid dynamics (CFD) simulations. Therefore, in the initial design phase, a couple of preliminary designs are conducted to establish initial values for combustor performance and geometric characteristics. In these preliminary designs, various one-dimensional models using analytical and empirical formulations may be used. One of the disadvantages of existing models is that they are typically geometric dependant, i.e. they apply only to the geometry they are derived for. Therefore the need for a more versatile design tool exists. In this work, which constitutes the first step in the development of such a versatile design tool, a single equation-set network simulation model to describe both steady state compressible and incompressible isothermal flow is developed. The continuity and momentum equations are solved through a hybrid type network model analogy which makes use of the SIMPLE pressure correction methodology. The code has the capability to efficiently compute flow through elements where the loss factor K is highly flow dependant and accurately describes variable area duct flow in the case of incompressible flow. The latter includes ducts with discontinuously varying flow sectional areas. Proper treatment of flow related non-linearities, such as flow friction, is facilitated in a natural manner in the proposed methodology. The proposed network method is implemented into a Windows based simulation package with a user interface. The ability of the proposed method to accurately model both compressible and incompressible flow is demonstrated through the analyses of a number of benchmark problems. It will be shown that the proposed methodology yields similar or improved results as compared to other’s work. The proposed method is applied to a research combustor to solve for isothermal flows and flow splits. The predicted flows were in relatively close agreement with measured data as well as detailed CFD analysis.Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2005.
Mechanical and Aeronautical Engineering
unrestricted
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Azhar, Maryam. "Design optimisation of a CO2 pipeline network in Australia under variable flow." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28856.
Full textAbstract:
Carbon Capture and Storage is a promising technique for mitigating greenhouse gas emissions that involves separating CO2 from other emitted gases, transporting and storing it in a geologic formation. Pipeline transport of CO2 is generally the preferred method for long-term onshore transport. However, pipeline operations and related costs are impacted by flow rate variability. Hence, this thesis develops and investigates stochastic pipeline design methods suitable for pipelines operating under variable CO2 flow rates.
First, the generation rate of CO2 at power plants with potential for capture is analysed stochastically, and the most suitable probability distribution function for modelling the related CO2 flow rates is identified. This selected probabilistic model is then used for developing an optimal pipeline design method, based on an exhaustive search technique. A shortcut method is then proposed, that approximates the costs of the optimal pipeline design for a variable CO2 flowrate with a typical scaled mean flow. Using the proposed method, analysis of the resulting designs shows that pipelines operating at variable flow rate are always overdesigned relative to steady-state, to accommodate the maximum flow rate.
The proposed simplistic models for pre-feasibility assessments of CO2 pipeline design and costs identify the scaled mean flow rate as a key parameter for determining the optimal pipeline diameter and unitised cost (A$/t-km). Sensitivity analyses indicate that under either variable flow or steady-state conditions, the steel price, cost of electricity and booster pump costs are the main drivers for the optimal diameter. Finally, simple adjustment factors for pipeline design and costs for a variable flow pipeline are proposed. These adjustment factors can provide quick estimates of design and costs for a scoping analysis within limited ranges of steel price, cost of electricity and booster pump costs.
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Raini, Rebecca Kemunto. "IPM information network analysis case study on information flow in integrated tomato pest management in Kenya." Weikersheim Margraf, 2006. http://deposit.d-nb.de/cgi-bin/dokserv?id=2849928&prov=M&dok_var=1&dok_ext=htm.
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Trussell, Larry V. "Segflow: a new object-oriented load flow which uses trace methods and affiliation objects." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40082.
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Gautier, Antoine. "Singly-constrained monotropic network flow problems : a linear time transformation to unconstrained problems and qualitative sensitivity analysis." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30879.
Full textAbstract:
This thesis examines several problems related to singly-constrained Monotropic Network Flow Problems. In the first part, a linear time algorithm that reduces the solution of a monotropic network flow problem with an additional linear equality constraint to the solution of lower dimensional subproblems is presented. Of the subproblems, at most one is a singly-constrained monotropic network flow problem while the others are unconstrained. If none of the subproblems is constrained, the algorithm provides a linear-time transformation of constrained to unconstrained monotropic network flow problems. Extensions to nonlinear and inequality constraints are given.
In the second part the qualitative theory of sensitivity analysis for Unconstrained Minimum-Cost Flow Problems presented by Granot and Veinott [GV85] is extended to Minimum-Cost Flow Problems with one additional linear constraint. The departure from the unconstrained network structure is shown to have a profound effect on computational issues. Two natural
extensions of the "less-dependent-on" partial ordering of the arcs given in [GV85] are presented. One is decidable in linear time while the other yields more information but is NP-complete in general. The Ripple Theorem gives upper bounds on the absolute value of optimal-flow variations as a function of variations in the problem parameter. Moreover, it shows how changes may "ripple down" throughout the network, decreasing in magnitude as one gets "further away" from the arc whose parameter initiated the change. The Theory of Substitutes and Complements presents necessary and sufficient conditions for optimal-flow changes to consistently have the same (or the opposite) sign in two given arcs. The complexity
of determining Substitutes and Complements is shown to be NP-complete in general. However, for all intractable problems, families of cases arise from easily recognizable graph structures and can be computed in linear time. The Monotonicity Theory links the changes in the value of the parameters to the change in the optimal arc-flows. Bounds on the rates
of changes are discussed.
We further provide a number of practical situations where our theory may apply. We discuss some Multi-Period Multi-Product Inventory-Production models that can be formulated
as nonlinear parametric network flow problems with one additional linear constraint. We then apply our theory to help decision makers understand qualitatively how to respond to changes in the environment such as machine breakdown, strike or variations in inventory carrying costs without additional computation. In a second example, we show how a Cash-Flow Management model can be formulated as a nonlinear parametric network flow problem with one additional linear constraint. The theory is then recommended as a method by which a decision maker could understand qualitatively how to respond to changes in the environment such as variations in interest rates, taxes or asset prices without any additional computation.Business, Sauder School of
Graduate
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Jadidi, Zahra. "Flow-based Anomaly Detection in High-Speed Networks." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/367890.
Full textAbstract:
With the advent of online services, the Internet has become extremely busy and demanding faster access. The increased dependency on the Internet obliges Internet service providers to make it reliable and secure. In this regard, researchers are tirelessly working on a number of technologies in order to ensure the continued viability of the Internet. Intrusion detection is one of the fields that enables secure operation of the Internet. An intrusion detection system (IDS) attempts to discover malicious activities in a network. However, with the increasing network throughput, IDSs should be able to analyse high volumes of traffic in real-time. Flow-based analysis is one of the methods capable of handling high-volume traffic. This method reduces the input traffic of IDSs because it analyses only packet headers. Flow-based anomaly detection can increase the reliability of the Internet, provided this method is functional at an early stage and complemented by packet-based IDSs at later stages.
Employing artificial intelligence (AI) methods in IDSs provides the capability to detect attacks with better accuracy. Compared with typical IDSs, AI-based systems are more inclined towards detecting unknown attacks. This thesis proposes an artificial neural network (ANN) based flow anomaly detector optimised with metaheuristic algorithms. The proposed method is evaluated using a number of flow-based datasets generated. An ANN-based flow anomaly detection enables a high detection rate; hence, this thesis investigates this system more thoroughly. The ANN-based system is a supervised method which needs labelled datasets; however, labelling of a large amount of data found in high-speed networks is difficult. Semi-supervised methods are the combination of supervised and unsupervised methods, which can work with both labelled and unlabelled data. A semi-supervised method can provide a high detection rate even when there is a small proportion of labelled data; therefore, the application of this method in flow-based anomaly detection is considered.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Information and Cmmunication Technology
Science, Environment, Engineering and Technology
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Wang, Zhuoyang. "Application of Complex Network Theory in Power System Security Assessment." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/17367.
Full textAbstract:
The power demand increases every year around the world with the growth of population and the expansion of cities. Meanwhile, the structure of a power system becomes increasing complex. Moreover, increasing renewable energy sources (RES) has linked to the power network at different voltage levels. These new features are expected to have a negative impact on the security of the power system. In recent years, complex network (CN) theory has been studied intensively in solving practical problems of large-scale complex systems. A new direction for power system security assessment has been provided with the developments in the CN field. In this thesis, we carry out investigations on models and approaches that aim to make the security assessment from an overview system level with CN theory. Initially, we study the impact of the renewable energy (RE) penetration level on the vulnerability in the future grid (FG). Data shows that the capacity of RE has been increasing over by 10% annually all over the world. To demonstrate the impact of unpredictable fluctuating characteristics of RES on the power system stability, a CN model given renewable energy integration for the vulnerability analysis is introduced. The numerical simulations are investigated based on the simplified 14-generator model of the South Eastern Australia power system. Based on the simulation results, the impact of different penetrations of RES and demand side management on the Australian FG is discussed. Secondly, the distributed optimization performance of the communication network topology in the photovoltaic (PV) and energy storage (ES) combined system is studied with CN theory. A Distributed Alternating Direction Method of Multipliers (D-ADMM) is proposed to accelerate the convergence speed in a large dimensional communication system. It is shown that the dynamic performance of this approach is highly-sensitive to the communication network topology. We study the variation of convergence speed under different communication network topology. Based on this research, guidance on how to design a relatively more optimal communication network is given as well. Then, we focus on a new model of vulnerability analysis. The existing CN models usually neglect the detailed electrical characteristics of a power grid. In order to address the issue, an innovative model which considers power flow (PF), one of the most important characteristics in a power system, is proposed for the analysis of power grid vulnerability. Moreover, based on the CN theory and the Max-Flow theorem, a new vulnerability index is presented to identify the vulnerable lines in a power system. The comparative simulations between the power flow model and existing models are investigated on the IEEE 118-bus system. Based on the PF model, we improve a power system cascading risk assessment model. In this research the risk is defined by the consequence and probabilities of the failures in the system, which is affected by both power factors and the network structure. Furthermore, a cascading event simulation module is designed to identify the cascading chain in the system during a failure. This innovation can form a better module for the cascading risk assessment of a power system. Finally, we argue that the current cyber-physical network model have their limitations and drawbacks. The existing “point-wise” failure model is not appropriate to present the interdependency of power grid and communication network. The interactions between those two interdependent networks are much more complicated than they were described in some the prior literatures. Therefore, we propose a new interdependency model which is based on earlier research in this thesis. The simulation results confirm the effectiveness of the new model in explaining the cascading mechanism in this kind of networks.
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Kuo, Hsien-Chih. "Applying network flow and simulated annealing in job shop rescheduling due to machine breakdowns." Ohio : Ohio University, 1996. http://www.ohiolink.edu/etd/view.cgi?ohiou1178224749.
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Min, Liang. "Decomposition algorithms for multi-area power system analysis." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5919.
Full textAbstract:
A power system with multiple interconnected areas needs to be operated coordinately
for the purposes of the system reliability and economic operation, although
each area has its own ISO under the market environment. In consolidation of different
areas under a common grid coordinator, analysis of a power system becomes more
computationally demanding. Furthermore, the analysis becomes more challenging
because each area cannot obtain the network operating or economic data of other
areas.
This dissertation investigates decomposition algorithms for multi-area power system
transfer capability analysis and economic dispatch analysis. All of the proposed
algorithms assume that areas do not share their network operating and economic
information among themselves, while they are willing to cooperate via a central coordinator
for system wide analyses.
The first proposed algorithm is based on power transfer distribution factors
(PTDFs). A quadratic approximation, developed for the nonlinear PTDFs, is used to
update tie-line power flows calculated by Repeated Power Flow (RPF). These tie-line
power flows are then treated as injections in the TTC calculation of each area, as
the central entity coordinates these results to determine the final system-wide TTC
value.
The second proposed algorithm is based on REI-type network equivalents. It uses
the Continuation Power Flow (CPF) as the computational tool and, thus, the problem of voltage stability is considered in TTC studies. Each area uses REI equivalents of
external areas to compute its TTC via the CPF. The choice and updating procedure
for the continuation parameter employed by the CPF is implemented in a distributed
but coordinated manner.
The third proposed algorithm is based on inexact penalty functions. The traditional
OPF is treated as the optimization problems with global variables. Quadratic
penalty functions are used to relax the compatible constraints between the global
variables and the local variables. The solution is proposed to be implemented by
using a two-level computational architecture.
All of the proposed algorithms are verified by numerical comparisons between the
integrated and proposed decomposition algorithms. The proposed algorithms lead to
potential gains in the computational efficiency with limited data exchanges among
areas.
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López, Claudio David. "Shortening time-series power flow simulations for cost-benefit analysis of LV network operation with PV feed-in." Thesis, Uppsala universitet, Elektricitetslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-242099.
Full textAbstract:
Time-series power flow simulations are consecutive power flow calculations on each time step of a set of load and generation profiles that represent the time horizon under which a network needs to be analyzed. These simulations are one of the fundamental tools to carry out cost-benefit analyses of grid planing and operation strategies in the presence of distributed energy resources, unfortunately, their execution time is quite substantial. In the specific case of cost-benefit analyses the execution time of time-series power flow simulations can easily become excessive, as typical time horizons are in the order of a year and different scenarios need to be compared, which results in time-series simulations that require a rather large number of individual power flow calculations. It is often the case that only a set of aggregated simulation outputs is required for assessing grid operation costs, examples of which are total network losses, power exchange through MV/LV substation transformers, and total power provision from PV generators. Exploring alternatives to running time-series power flow simulations with complete input data that can produce approximations of the required results with a level of accuracy that is suitable for cost-benefit analyses but that require less time to compute can thus be beneficial. This thesis explores and compares different methods for shortening time-series power flow simulations based on reducing the amount of input data and thus the required number of individual power flow calculations, and focuses its attention on two of them: one consists in reducing the time resolution of the input profiles through downsampling while the other consists in finding similar time steps in the input profiles through vector quantization and simulating them only once. The results show that considerable execution time reductions and sufficiently accurate results can be obtained with both methods, but vector quantization requires much less data to produce the same level of accuracy as downsampling. Vector quantization delivers a far superior trade-off between data reduction, time savings, and accuracy when the simulations consider voltage control or when more than one simulation with the same input data is required, as in such cases the data reduction process can be carried out only once. One disadvantage of this method is that it does not reproduce peak values in the result profiles with accuracy, which is due to the way downsampling disregards certain time steps in the input profiles and to the averaging effect vector quantization has on the them. This disadvantage makes the simulations shortened through these methods less precise, for example, for detecting voltage violations.
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Bard, Ari. "Modeling and Predicting Heat Transfer Coefficients for Flow Boiling in Microchannels." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1619091352188123.
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Akbar, Ghanadian Sara. "A Framework Based on Social Network Analysis (SNA) to Evaluate Facilities and Alternative Network Designs for Closed Loop Supply Chains." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1596583638602018.
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Martin, Mogamat Noer. "Optimal placement and effect of a wind farm on load flow and protection systems in a municipal distribution network." Master's thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/31005.
Full textAbstract:
Much research has been done on the effects of distributed generation on network characteristics. However, little research has been done on the effects of this distributed generation on current network protection schemes. An IPP has approached a South African municipality regarding the connection of a wind farm that would be connected to the municipality’s existing grid. This presented a unique opportunity to simulate and study the impact and effect that this wind farm would have on a real-life network in terms of network operation and protection schemes. This also presents the possibility of connecting the wind farm in a different configuration, possibly resulting in better network operation at a lower cost. The network optimisation in this research was done using the probability-based incremental learning (PBIL) and differential evolution (DE) optimisation techniques. These algorithms were programmed and modelled according to the desired IPP wind farm requirements using the MATLAB and MATPOWER simulation packages. The networks used in these algorithms were modelled in the text-based MATPOWER format. This research goes on to study a modified 14-bus IEEE test network in terms of network characteristics and protection performance so that an idea of the performance of the optimisation algorithms can be obtained. Protection data for the IEEE network was not available. The network was thus graded for use in this study. The research then continues to model the existing and proposed network configuration, and proposes various other points of connection to the municipal network using the PBIL and DE algorithms. These studies were conducted using the DIgSILENT PowerFactory simulation package, with the networks and protection data being modelled in this package. Network and protection performance results were recorded for each case in both networks under study. The results show that in the case of the modified IEEE network, the DE algorithm provides a better solution in terms of improving power losses while the PBIL algorithm provides a better solution in terms of improving the voltage profile. In the case of the municipality network, the DE algorithm provides the best performance, with the DE result managing to reduce power losses by 83.89% compared to the current and proposed network configurations. The overall voltage profile was also seen to improve by over 23%. The research also found that the change in fault level for the various cases are minimal. This is due to the limitation in fault current contribution imposed by the use of an inverter system connecting the wind farm to the grid. This means that, as the results shows, network grading is not very much affected by the addition of the wind farm connections. However, it is seen that the municipal network is not optimally graded in the base case. Finally, it is also seen that, though not often used in research, the MATPOWER package works well as a network simulation tool. A costing analysis was also conducted and shows that the DE solution is the most cost-effective solution, in addition to being the best-performing solution. The study recommends that the results produced by the DE algorithm be implemented instead of the proposed implementation. The municipal network should also be regraded and new protection settings should be implemented.
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Conley, Thomas A. "Effective Programmatic Analysis of Network Flow Data for Security and Visualization using Higher-order Statistics and Domain Specific Embedded Languages." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1336482912.
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Stansberry, Kathleen, and Kathleen Stansberry. "One-Step, Two-Step, or Multi-Step Flow: The Role of Influencers in Information Processing and Dissemination in Online, Interest-Based Publics." Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12416.
Full textAbstract:
This research examines information flow in online, interest-based networks to determine if existing models of information dissemination are adequate to describe the communication processes that occur in online publics. This study finds that a small number of primary influencers from within online communities are central to information collection, collation, and distribution in online, interest-based networks. This finding is inconsistent with one-step, two-step, and multi-step flow models, which privilege mass media as the central source of information. To more accurately depict online information flow in interest-based networks, this study introduces the radial model of information flow. Furthermore, the results of this study show that communication processes in online publics are best explained using a combination of the transmissive paradigm of communication, on which information flow models are based, and a ritual view of communication.
This research also contributes to the ongoing development of the situational theory of publics by identifying organized publics as a key subgroup of active publics. Organized publics are networks of individuals within active publics who frequently and consistently communicate on a shared interest or concern. Organized publics form active online communication networks and prepare for advocacy related to a shared interest, making them of particular interest to public relations professionals.
Using a case study approach, this dissertation uses online network analysis and qualitative cluster analysis to study the role of community influencers in information flow and cultural development within the online young adult cancer community. Instead of focusing exclusively on social media as channel for message dissemination, the results of this study indicate that successful relationship building can best by achieved by public relations practitioners who work to develop authentic presences in online communities. This research shows that embracing a participatory model of public relations that actively engages primary influencers in the planning and campaign implementation processes can promote authentic online presences.
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Sikdar, Kieran Jonah. "Material Flow Optimization And Systems Analysis For Biosolids Management: A Study Of The City Of Columbus Municipal Operations." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1218074193.
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Isik, Zerrin. "Network Structure Based Pathway Enrichment System To Analyze Pathway Activities." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612951/index.pdf.
Full textAbstract:
Current approaches integrating large scale data and information from a
variety of sources to reveal molecular basis of cellular events do not
adequately benefit from pathway information. Here, we portray a network structure based pathway enrichment system that fuses and exploits model and data: signalling pathways are taken as the biological models while microarray and ChIP-seq data are the sample input data sources among many other alternatives. Our model- and data-driven hybrid system allows to quantitatively assessing the biological activity of a cyclic pathway and simultaneous enrichment of the significant paths leading to the ultimate cellular response. Signal Transduction Score Flow (SiTSFlow) algorithm is the fundamental constituent of proposed network structure based pathway enrichment system. SiTSFlow algorithm converts each pathway into a cascaded graph and then gene scores are mapped onto the protein nodes. Gene scores are transferred to en route of the pathway to form a final activity score describing behaviour of a specific process in the pathway while enriching of the gene node scores. Because of cyclic pathways, the algorithm runs in an iterative manner and it terminates when the node scores converge. The converged final activity score provides a quantitative measure to assess the biological significance of a process under the given experimental conditions. The conversion of cyclic pathways into cascaded graphs is performed by using a linear time multiple source Breadth First Search Algorithm. Furthermore, proposed network structure based pathway enrichment system works in linear time in terms of nodes and edges of given pathways.
In order to explore various biological responses of several processes in a
global signalling network, the selected small pathways have been unified based on their common gene and process nodes. The merge algorithm for pathways also runs in linear time in terms of nodes and edges of given pathways.
In the experiments, SiTSFlow algorithm proved the convergence behaviour of activity scores for several cyclic pathways and for a global signalling network. The biological results obtained by assessing of experimental data by described network structure based pathway enrichment system were in correlation with the expected cellular behaviour under the given experimental conditions.
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Wan, Yen-Tai. "Material transport system design in manufacturing." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-03282006-231022/.
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Thesis (Ph. D.)--Industrial and Systems Engineering, Georgia Institute of Technology, 2006.Dr. Yih-Long Chang, Committee Member ; Dr. Martin Savelsbergh, Committee Member ; Dr. Leon McGinnis, Committee Co-Chair ; Dr. Gunter Sharp, Committee Chair ; Dr. Doug Bodner, Committee Member ; Dr. Joel Sokol, Committee Member.
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Yeates, Christopher. "Multi-Scale Study of Foam Flow Dynamics in Porous Media." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS023/document.
Full textAbstract:
Pour ce travail, nous utilisons un micromodèle à haute complexité et à structure fixe pour faire une série d’expériences en variant la vitesse d’injection, la qualité de la mousse, les distributions de taille de bulles d’injection, et la méthode d’injection. Nous mettons en œuvre un suivi individuel de bulles pour associer les propriétés d’écoulement aux propriétés de taille de bulles ainsi que les caractéristiques structurelles du milieu poreux. Nous proposons de nouveaux outils pour décrire l’écoulement d’un point de vue global et local de différentes manières. Nous établissons des comportements spécifiques à chaque taille de bulle, en montrant que les bulles des mousses piégées sont plus probables d’être de taille inférieure aux tailles de bulles moyennes, alors que les mousses en mouvement accèdent elles-mêmes à différents chemins d’écoulement selon les tailles de bulles. Les bulles plus volumineuses s’écoulent en majorité dans des chemins préférentiels à haute vitesse, généralement parallèles au gradient de pression, mais les petites bulles sont transportées en supplément à l’intérieur de chemins transversaux liant les chemins préférentiels. Ailleurs, pour nos données nous démontrons l’importance supérieure de la fraction de mousse piégée vis-à-vis de la densité de bulles quant à l’explication microscopique de la viscosité apparente, malgré une contribution des deux. Nous caractérisons structurellement les zones piégées à répétition, comme étant soit des zones à faible coordination de pore, de faible taille de seuil d’entrée, d’orientation de seuil désavantageuse, ou une combinaison de ceux-ci. Les zones à fort écoulement échappent à une caractérisation en termes de paramètres de structure locale et nécessitent une considération de l’information des différents chemins traversant la totalité du modèle. À ce but, afin de décrire les zones à fort écoulement, nous développons un modèle générant des chemins, utilisant une représentation en graphe du milieux poreux, basé sur une décomposition initiale en pores et seuils, qui intègre seulement les notions de taille de seuil et d’orientation de seuil relatif au gradient de pression pour caractériser les cheminsIn this work, we use of a high-complexity micromodel of fixed structure on which we perform a series of experiments with varying injection rates, foam qualities, inlet bubble size distributions and injection methods. We perform individual bubble tracking and associate flow properties with bubble size properties and structural characteristics of the medium. We propose new tools describing the local and global flow in different ways. We establish specific behaviors for different bubble sizes, demonstrating that trapped foams are more likely to have smaller than average bubble sizes, while flowing bubbles also tend to segregate in different flow paths according to bubble size. Larger bubbles tend to flow in high-velocity preferential paths that are generally more aligned with pressure gradient, but smaller bubbles tend to access in supplement transversal paths linking the different preferential paths. Furthermore, for our data we establish the pre-eminence of the trapped foam fraction over bubble density within the microscopic explanation of apparent viscosity, although both contribute to some degree. We structurally characterize consistently trapped zones as areas with either low pore coordination, low entrance throat size, unfavorable throat orientation or a combination thereof. High-flow zones however cannot be characterized in terms of local structural parameters and necessitate integration of complete path information from the entire model. In this regard, in order to capture the high-flow zones, we develop a path-proposing model that makes use of a graph representation of the model, from an initial decomposition into pores and throats, that uses only local throat size and throat orientation relative to pressure gradient to characterize paths
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Lei, Peng. "A Linear Programming Method for Synthesizing Origin-Destination (O-D) Trip Tables from Traffic Counts for Inconsistent Systems." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36860.
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Origin-Destination (O-D) trip tables represent the demand-supply information of each directed zonal-pair in a given region during a given period of time. The effort of this research is to develop a linear programming methodology for estimating O-D trip tables based on observed link volumes. In order to emphasize the nature of uncertainty in the data and in the problem, the developed model permits the user's knowledge of path travel time to vary within a band-width of values, and accordingly modifies the user-optimality principle. The data on the observed flows might also not be complete and need not be perfectly matched. In addition, a prior trip table could also be specified in order to guide the updating process via the model solution. To avoid excessive computational demands required by a total numeration of all possible paths between each O-D pair, a Column Generation Algorithm (CGA) is adopted to exploit the special structures of the model. Based on the known capacity of each link, a simple formula is suggested to calculate the cost for the links having unknown volumes. An indexed cost is introduced to avoid the consideration of unnecessary passing-through-zone paths, and an algorithm for solving the corresponding minimum-cost-path problem is developed. General principles on the design of an object-oriented code are presented, and some useful programming techniques are suggested for this special problem. Some test results on the related models are presented and compared, and different sensitivity analyses are performed based on different scenarios. Finally, several research topics are recommended for future research.Master of Science
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Zhang, Lei Ph D. Massachusetts Institute of Technology Department Electrical Engineering and Computer Science fl 2014. "Network management and control of flow-switched optical networks : joint architecture design and analysis of control plane and data plane with physical-layer impairments." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/100879.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 175-178).
Optical Flow Switching (OFS) that employs agile end-to-end lightpath switching for users with large transactions has been shown to be cost-effective and energy-efficient. However, whether it is possible to coordinate lightpath switching and scheduling at a global scale on a per-session basis, and how the control plane and data plane performance correlate remained un-answered. In this thesis, we have addressed the network management and control aspect of OFS, and designed a network architecture enabling both a scalable control plane and an efficient data plane. We have given an overview of essential network management and control entities and functionalities. We focused on the scheduling problem of OFS because its processing power and generated control traffic increase with traffic demand, network size, and closely correlate with data network architecture, while other routine maintenance type of control plane functionalities contribute either a fixed amount or negligibly to the total efforts. We considered two possible Wide Area Network architectures: meshed or tunneled, and developed a unified model for data plane performance to provide a common platform for the performance comparison of the control plane. The results showed that with aggregation of at least two wavelengths of traffic and allowing about two transactions per wavelength to be scheduled to the future, the tunneled architecture provides comparable data plane performance as the meshed architecture. We have developed a framework to analyze the processing complexity and traffic of the control plane as functions of network architecture, and traffic demand. To guarantee lightpath quality in presence of physical-layer impairments, we developed models for quality of EDFA-amplified optical links and impairment-aware scheduling algorithms for two cases, a) the known worst case of channel quality is when there is no "On" channel in a fiber, and b) detailed channel configuration of a fiber is needed to determine channel quality. Without physical-layer impairments, tunneled architecture reduces control plane traffic and processing complexity by orders of magnitude. With impairment-aware scheduling, detailed channel configuration information reporting leads to heavy control traffic (~250 Gbps/edge); while known worst case and tunneling leads to manageable control traffic (~36 Gbps/edge) and processing power (1-4 i7 CPUs).
by Lei Zhang.
Ph. D.
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Meredith, Gwendŵr R. "Boundaries and Bridges in Rangeland Social-Ecological Systems: Studies of Collaboration, Innovation, and Information Flow." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7688.
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Public rangelands are managed by a mixture of federal, state, and local governments. Often, these groups are charged with managing adjacent lands that are part of the same greater landscape. To do this effectively, communication and collaboration is required. This dissertation examines federal, state, and local agencies’ level of communication through three projects.
The first project examined barriers to agencies adopting management tools from each other. I found that individuals within agencies were mainly staying within their own agency when seeking advice, so individuals were not communicating about tools or their findings across agencies. Furthermore, agency policies and fear of being sued restricted individuals’ ability to adopt management tools. The second project studied how land and wildlife managers in Southeastern Utah work together, or not, in managing mule deer populations that migrate to and from land managed by different agencies. I found that managers are working together to manage mule deer populations, but there are only a few individuals that tie everyone together. The third project looked at how federal, state, and local governments work together to rehabilitate lands after a wildfire that burned parts of Southwestern Idaho and Southeastern Oregon. I found that policy decisions at the federal level can heavily impact who works together and when.
All three projects revealed that there are still barriers to federal, state, and local governments working together to manage the same landscape. However, the results from this dissertation also highlight opportunities for bridging the gap between agencies and, ultimately, improving management of rangelands.
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Elfstadius, Martin, and Daniel Gecer. "Method to Detect and Measure Potential Market Power Caused by Transmission Network Congestions on Electricity Markets." Thesis, Linköping University, Department of Electrical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-12133.
Full textAbstract:
This thesis is based on studies of the deregulated electricity markets located in the United States of America. The problem statement of the thesis evolved continuously throughout our initial period of research. Focus was finally put on monitoring and detection of potential market power caused by congestion in the transmission network. The existence of market power is a serious concern in today’s electric energy markets. A system that monitors the trading is needed and much research and many proposals on how to deal with this problem have been introduced over the years. We focus on some of these approaches and develop an approach of our own, which we call “Monopolistic Energy Calculation”. We adopt the idea to identify participants with the ability to raise prices without losing market share. An ability that should not be present on a competitive market. We take this idea further by identifying participants with the ability to make considerable price raises without losing all market shares. We propose a way to calculate the remaining market shares (Monopolistic Energy Levels) after a large price raise. These calculated levels of energy, that are only deliverable by a certain participant or by a certain group of participants, are caused by the active congestions in the network.
The approach detects the amounts of these energy levels and the location in the network at which they are present. This is a prospective method if used with a prediction of the following day’s demand, which is regularly available with high accuracy. The method can also be used for monitoring purposes to identify critical situations in real-time. The method is implemented and two sets of simulations are done in which we explain and evaluate the approach. The results are promising and the correlation between “Monopolistic Energy” and market power is confirmed.
Detta examensarbete är baserat på studier av de deregulerade electricitsmarknaderna i USA. Problemformuleringen var i början av detta arbete inte definitiv, utan utvecklades under en längre inledande fas av forskningsarbete. Slutligen kunde vi faställa att detektion av potentiell marknadskraft på elektricitetsmarknaden, orsakat av överbelastningar i transmissionnätverket, var av särskilt intresse. Ett system som övervakar handeln och förekomster av orättvisor orsakat av detta är nödvändigt. Det har de senaste åren gjorts mycket forskning inom detta område. Baserat på denna forskning utvecklades sedan ett eget förslag, som vi kallar ”Monopolistic Energy Calculations”. Vissa tidigare förslag på hur problemet kan angripas blev av särskilt intresse. En idé från dessa var att identifiera marknadsaktörer med förmågan att höja priser utan att förlora marknadsandelar, en icke önskvärd egenskap hos aktörer då en konkurrenskraftig marknad är eftertraktad.
Vi tar denna idé ett steg längre genom att identifiera marknadsaktörer med förmågan att höja priser signifikant utan att förlora alla marknadsandelar. Vi föreslår ett sätt att beräkna dessa energinivåer som endast är möjliga att levereras av en eller ett fåtal särskilda aktörer, som direkt följd av de aktiva stockningarna i nätverket, under antagandet av en inelastisk efterfrågan. Vi föreslår ett sätt att beräkna de återstående marknadsandelarna (Monopolistic Energy Levels) efter en stor prishöjning. Vår metod beräknar mängden av denna energi och var i nätverket dessa mängder förekommer. Denna metod kan sia om framtida problem om en estimering av morgondagens efterfråga används. Sådana estimeringar görs idag
regelbundet med hög träffsäkerhet. Metoden kan även användas i realtid för upptäckt av kritiska marknadssituationer. Simuleringar av detta görs som förklarar vår lösning och utvärderar den. Resultaten är lovande och korrelationen mellan ”Monopolistisk Energi” och marknadskraft är bekräftade.
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Högstedt, Malin, and MIKAELA KENNE. "En effektiv etablering av kundinfomation för att öka värdet i produktutveckling." Thesis, KTH, Maskinkonstruktion (Inst.), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192525.
Full textAbstract:
Idag är det vedertaget att det är vitalt för företag att involvera kunderna i produktutvecklingen för att bättre förstå marknadens behov och maximera värdeskapandet av produkterna. Denna involvering kommer att resultera i en ökad innovationskapacitet för organisationen. Denna fallstudie har för avsikt att besvara forskningsfrågan; hur ska ett medelstort högteknologiskt företag fördela kundinformationsflödet på ett systematiskt tillvägagångssätt för att öka innovationskapaciteten? Forskningsmetodiken består av tre delar; såsom förstudie, social nätverksanalys, samt intern och extern benchmarking. Förstudien består av 21 intervjuer internt i organisationen och det sociala nätverket baseras på en enkät, som 49 individer har besvarat. Benchmarkingen har involverat sex individer från en intern avdelning och två intervjuer med externa företag inom samma bransch. Resultatet tyder på att mängden interaktioner med externa kunder bör reduceras för att systematiskt och strukturerat inhämta kundinformationen. För att öka informationsflödet inom organisationen bör en särskild avdelning, som har daglig kontakt med alla avdelningar, ha en informationsspridande roll som överför informationen från marknadsavdelningen till resterande avdelningar internt. Därtill bör spridningen av kundinformation integreras i den dagliga arbetsprocessen, då det underlättar att anamma och använda informationen i det dagliga arbete.Nowadays, it is well known that it is highly important to involve the customers in the product development in order to better understand the needs of the market, increase the relations to customers and maximize the value creation of the products. This will result in a higher innovation capacity for the organization. This case study intends to answer the research questions, how to allocate the customer information flow in a systematic approach at a medium size high technology company in order to increase the innovation capacity. The research methodology consists of three different parts including pre study, social network analysis, and internal and external benchmarking. The pre study consists of 21 interviews internally in the organization and the social network analysis is based on a survey, which 49 individuals have answered. The benchmarking involves six employees from another department and two interviews with external companies within the same business. The results indicate that the amount of customer interactions with external parties must be decreased in order to systematically receive and maintain customer information. In order to increase the information flow within the organization a specific department, that have daily contacts with almost all departments, should act as a transmitting function as they would connect marketing with research and development. Furthermore, the customer information should be included in the daily working process as it is easier for the employees to embrace and jointly utilize this information.
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Portelli, Rebecca. "CheesePi: Delay Characterization through TCP-based Analysis from End-to-End Monitoring." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-194244.
Full textAbstract:
With increasing access to interconnected IP networks, people demand a faster response time from Internet services. Traffic from web browsing, the second most popular service, is particularly time-sensitive. This demands reliability and a guarantee of delivery with a good quality of service from ISPs. Additionally, the majority of the population do not have the technical background to monitor the delay themselves from their home networks, and their ISPs do not have a vantage point to monitor and diagnose network problems from the users’ perspective. Hence, the aim for this research was to characterise the “in-protocol” network delay encountered during web browsing from within a LAN. This research presents TCP traffic monitoring performed on a client device as well as TCP traffic monitoring over both the client-end and the server-end devices separately observing an automated web client/server communication. This was followed by offline analysis of the captured traces where each TCP flow was dissected into: handshake, data transfer, and teardown phases. The aim behind such extraction was to enable characterisation of network round-trip delay as well as network physical delay, end host processing delay, web transfer delay, and packets lost as perceived by the end hosts during data transfer. The outcome of measuring from both end devices showed that monitoring from both ends of a client/server communication results to a more accurate measurement of the genuine delay encountered when packets traverse the network than when measuring from the client-end only. Primarily, this was concluded through the ability to distinguish between the pure network delay and the kernel processing delay experienced during the TCP handshake and teardown. Secondly, it was confirmed that the two RTTs identified in a TCP handshake are not symmetrical and that a TCP teardown RTT takes longer than the TCP handshake RTT within the same TCP flow since a server must take measures to avoid SYN flooding attacks. Thirdly, by monitoring from both end devices, it was possible to identify routing path asymmetries by calculating the physical one-way delay a packet using the forward path in comparison to the physical delay of a packet using the reverse path. Lastly, by monitoring from both end devices, it is possible to distinguish between a packet that was actually lost and a packet that arrived with a higher delay than its subsequent packet during data transfer. Furthermore, utilizing TCP flows to measure the RTT delay excluding end host processing gave a better characterisation of the RTT delay as opposed to using ICMP traffic.Med ökande tillgång till den sammankopplade IP-nätet, krävs det en snabbare responstid från Internettjänster. Trafik från surfning, den näst mest populära tjänsten är särskilt tidskänsliga. Detta kräver tillförlitlighet och en garanti för data leverans med en god servicekvalitet från Internetleverantörer. Dessutom har de flesta av befolkningen inte den tekniska bakgrunden för att övervaka fördröjning sig från sina hemmanätverk, och deras Internetleverantörer har ingen utsiktspunkt för att övervaka och diagnostisera nätverksproblem från användarnas perspektiv. Därför syftet med denna forskning är att karakterisera “in-protokoll” fördöljingen i nätet, som påträffas under surfning inifrån ett LAN. Denna forskning visar TCP-trafik monitoring som utförs på en klientenhet, samt separat TCP-trafik monitoring över både klient-end och serve-end enheter, för att observera en automatiserad webbklient / server-kommunikation. Detta följs av offline analys av de infångade tracer där varje TCP flöde dissekerades in: handskakning, dataöverföring, och nedkoppling faser. Syftet bakom sådan utvinning är att möjliggöra karakterisering av nätverk fördröjning samt nätverkets fysiska fördröjning, behandlingsfördröjning, webböverföringsfördröjning och förlorade paket som uppfattas av end-device under dataöverföring. The outcome of measuring from both end devices showed that monitoring from both ends of a client/server communication results to a more accurate measurement of the genuine delay encountered when packets traverse the network than when measuring from the client-end only. Primarily, this was concluded through the ability to distinguish between the pure network delay and the kernel processing delay experienced during the TCP handshake and teardown. Secondly, it was confirmed that the two RTTs identified in a TCP handshake are not symmetrical and that a TCP teardown RTT takes longer than the TCP handshake RTT within the same TCP flow since a server must take measures to avoid SYN flooding attacks. Thirdly, by monitoring from both end devices, it was possible to identify routing path asymmetries by calculating the physical one-way delay a packet using the forward path in comparison to the physical delay of a packet using the reverse path. Lastly, by monitoring from both end devices, it is possible to distinguish between a packet that was actually lost and a packet that arrived with a higher delay than its subsequent packet during data transfer. Furthermore, utilizing TCP flows to measure the RTT delay excluding end host processing gave a better characterisation of the RTT delay as opposed to using ICMP traffic. Resultatet av mätningarna från både slut-enheter visar att övervakning från båda ändar av en klient / server-kommunikation resulterar en noggrannare mätning av fördröjningar som uppstår när paketen färdas över nätverket än vid mätning från den enda klienten. Främst avslutades detta genom förmågan att skilja mellan den rena nätfördröjningen och kernel bearbetning under TCP handskakning och nedkoppling. För det andra bekräftades att de två RTT som identifierats i en TCP handskakning inte är symmetriska och att TCP nedkoppling RTT är längre än TCP handskakning RTT inom samma TCP flödet, eftersom servern måste vidta åtgärder för att undvika SYN översvämning attacker. För det tredje, genom att övervaka från båda avancerade enheter, var det möjligt att identifiera path asymmetrier genom att beräkna den fysiska envägsfördröjningen av ett paket på framåtriktade banan i jämförelse med den fysiska fördröjningen för ett paket på den omvända banan. Slutligen genom att övervaka från båda end enheter, är det möjligt att skilja mellan ett paket som faktiskt förlorades och ett paket som kom med en högre fördröjning än dess efterföljande paket under dataöverföring. Dessutom utnyttjande av TCP flöden för att mäta RTT exkluderat end-nod porocessering gav en bättre karakterisering av RTT fördröjning jämfört med att ICMP-trafik.
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Facó, Renata Tilemann. "Análise de papéis, formas de comunicação e fluxos de informação para o atendimento ao usuário na assistência farmacêutica : um estudo pela percepção do serviço de farmácia." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/135399.
Full textAbstract:
A Assistência Farmacêutica (AF) é um conceito de prática profissional onde o usuário que precisa do medicamento é o mais importante beneficiário das ações do farmacêutico e dos demais profissionais de saúde que atendem este serviço, ou seja, o usuário é o centro da atenção destes profissionais. Ela, entretanto, não pode ser visualizada apenas pela função de dispensar medicamentos, mas sim como um serviço que complementa as ações em saúde, com um enfoque amplo, incorpora a multidisciplinaridade e a integralidade. O sucesso deste processo depende da participação das diferentes classes de profissionais da saúde, além dos usuários. Este trabalho tem como objetivo analisar os papéis, as formas de comunicação e os fluxos de informação que influenciam nas operações multiprofissionais de atendimento ao usuário na Assistência Farmacêutica. Para tanto, foi escolhido o município de Arroio do Tigre/RS onde foram entrevistados os médicos, enfermeiros, técnicos de enfermagem, farmacêuticos, agentes de saúde, dentistas, psicólogos e assistentes sociais envolvidos na rede multiprofissional de Assistência Farmacêutica do município. Os dados obtidos nas entrevistas foram analisados qualitativamente, com o apoio de planilhas no software Excel para identificação de padrões entre os respondentes. Os fluxos de comunicação/informação foram analisados com o auxílio da ferramenta de análise de redes sociais, o NodeXL. O estudo permitiu observar que há uma necessidade de melhoria da comunicação e do fluxo de informação existente entre os profissionais além de um aumento da clareza do conceito do sistema entre os envolvidos na rede de atendimento ao usuário, esclarecendo as responsabilidades e papéis de cada um dentro da rede para uma gestão de atendimento na AF mais eficaz.The Pharmaceutical Services consists of a set of people with different relations among them, exchanging lots of information on a daily basis. Thus, it cannot be seen as just a function of dispensing drugs, but as a resource complementing healthcare actions, with a wide approach that incorporates a multidisciplinary and integrality. The success of this process depends on the participation of different classes of healthcare professionals, besides users. The aim of this paper is to study the roles, the forms of communication and information flows that influence multidisciplinary operations of service to users in Pharmaceutical Services. Therefore, the city of Arroio do Tigre/RS was chosen and interviews occurred with professionals such as doctors, nurses, nursing technicians, pharmacists, health workers, dentists, psychologists and social workers involved in the city’s Pharmaceutical Services multidisciplinary network. The data obtained from the interviews were qualitatively analyzed, with the support of Microsoft Excel’s spreadsheets for the identification of patterns among the interviewed. The communication/information flows were analyzed with the aid of NodeXL, a social network analysis tool. The study concluded that there is a need of communication and information flow improvement as well as a more clarity regarding the system concept among the professionals involved in the user service network, clarifying the accountabilities and roles of each one inserted in the network for a more effective drug management.