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Russell, Leslie Wallace. "Control system synthesis for plants with time delays". Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7650.
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Wang, Qing. "Model reduction for dynamic systems with time delays a linear matrix inequality approach /". Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38645439.
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Rahman, Bootan Mohammed. "Dynamics of neural systems with time delays". Thesis, University of Sussex, 2017. http://sro.sussex.ac.uk/id/eprint/67773/.
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Complex networks are ubiquitous in nature. Numerous neurological diseases, such as Alzheimer's, Parkinson's, epilepsy are caused by the abnormal collective behaviour of neurons in the brain. In particular, there is a strong evidence that Parkinson's disease is caused by the synchronisation of neurons, and understanding how and why such synchronisation occurs will bring scientists closer to the design and implementation of appropriate control to support desynchronisation required for the normal functioning of the brain. In order to study the emergence of (de)synchronisation, it is necessary first to understand how the dynamical behaviour of the system under consideration depends on the changes in systems parameters. This can be done using a powerful mathematical method, called bifurcation analysis, which allows one to identify and classify different dynamical regimes, such as, for example, stable/unstable steady states, Hopf and fold bifurcations, and find periodic solutions by varying parameters of the nonlinear system. In real-world systems, interactions between elements do not happen instantaneously due to a finite time of signal propagation, reaction times of individual elements, etc. Moreover, time delays are normally non-constant and may vary with time. This means that it is vital to introduce time delays in any realistic model of neural networks. In this thesis, I consider four different models. First, in order to analyse the fundamental properties of neural networks with time-delayed connections, I consider a system of four coupled nonlinear delay differential equations. This model represents a neural network, where one subsystem receives a delayed input from another subsystem. The exciting feature of this model is the combination of both discrete and distributed time delays, where distributed time delays represent the neural feedback between the two sub-systems, and the discrete delays describe neural interactions within each of the two subsystems. Stability properties are investigated for different commonly used distribution kernels, and the results are compared to the corresponding stability results for networks with no distributed delays. It is shown how approximations to the boundary of stability region of an equilibrium point can be obtained analytically for the cases of delta, uniform, and gamma delay distributions. Numerical techniques are used to investigate stability properties of the fully nonlinear system and confirm our analytical findings. In the second part of this thesis, I consider a globally coupled network composed of active (oscillatory) and inactive (non-oscillatory) oscillators with distributed time delayed coupling. Analytical conditions for the amplitude death, where the oscillations are quenched, are obtained in terms of the coupling strength, the ratio of inactive oscillators, the width of the uniformly distributed delay and the mean time delay for gamma distribution. The results show that for uniform distribution, by increasing both the width of the delay distribution and the ratio of inactive oscillators, the amplitude death region increases in the mean time delay and the coupling strength parameter space. In the case of the gamma distribution kernel, we find the amplitude death region in the space of the ratio of inactive oscillators, the mean time delay for gamma distribution, and the coupling strength for both weak and strong gamma distribution kernels. Furthermore, I analyse a model of the subthalamic nucleus (STN)-globus palidus (GP) network with three different transmission delays. A time-shift transformation reduces the model to a system with two time delays, for which the existence of a unique steady state is established. Conditions for stability of the steady state are derived in terms of system parameters and the time delays. Numerical stability analysis is performed using traceDDE and DDE-BIFTOOL in Matlab to investigate different dynamical regimes in the STN-GP model, and to obtain critical stability boundaries separating stable (healthy) and oscillatory (Parkinsonian-like) neural ring. Direct numerical simulations of the fully nonlinear system are performed to confirm analytical findings, and to illustrate different dynamical behaviours of the system. Finally, I consider a ring of n neurons coupled through the discrete and distributed time delays. I show that the amplitude death occurs in the symmetric (asymmetric) region depending on the even (odd) number of neurons in the ring neural system. Analytical conditions for linear stability of the trivial steady state are represented in a parameter space of the synaptic weight of the self-feedback and the coupling strength between the connected neurons, as well as in the space of the delayed self-feedback and the coupling strength between the neurons. It is shown that both Hopf and steady-state bifurcations may occur when the steady state loses its stability. Stability properties are also investigated for different commonly used distribution kernels, such as delta function and weak gamma distributions. Moreover, the obtained analytical results are confirmed by the numerical simulations of the fully nonlinear system.
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Huang, Wei-Ping. "Quasilinear Control of Systems with Time-Delays and Nonlinear Actuators and Sensors". ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/967.
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This thesis investigates Quasilinear Control (QLC) of time-delay systems with nonlinear actuators and sensors and analyzes the accuracy of stochastic linearization for these systems. QLC leverages the method of stochastic linearization to replace each nonlinearity with an equivalent gain, which is obtained by solving a transcendental equation. The idea of QLC is to stochastically linearize the system in order to analyze and design controllers using classical linear control theory. In this thesis, the existence of the equivalent gain for a closed-loop time-delay system is discussed. To compute the equivalent gain, two methods are explored. The first method uses an explicit but complex algorithm based on delay Lyapunov equation to study the time-delay, while the second method uses Pade approximant. It is shown that, under a suitable criterion, Pade approximant can be effectively applied for QLC of time-delay systems. Furthermore, the method of Saturated-Root Locus (S-RL) is extended to nonlinear time-delay systems. It turns out that, in a time-delay system, S-RL always terminates prematurely as opposed to a delay-free system, which may or may not terminate prematurely. Statistical experiments are performed to investigate the accuracy of stochastic linearization compared to a system without time-delay. The impact of increasing the time-delay in the approach of stochastic linearization is also investigated. Results show that stochastic linearization effectively linearizes a nonlinear time-delay system, even though delays generally degrade accuracy. Overall, the accuracy remains relatively high over the selected parameters. Finally, this approach is applied to pitch control in a wind turbine system as a practical example of a nonlinear time-delay system, and its performance is analyzed to demonstrate the efficacy of the approach.
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Wang, Qing y 王卿. "Model reduction for dynamic systems with time delays: a linear matrix inequality approach". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38645439.
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Stupak, Noah. "Time-delays and system response times in human-computer interaction /". Online version of thesis, 2009. http://hdl.handle.net/1850/10867.
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Umang, Nitish. "Evaluating passenger delays in the US domestic air transportation system". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60813.
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Thesis (S.M. in Transportation)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 104-107).
A fundamental component of any National Airspace System (NAS) performance evaluation is the cost impact of air traffic delays, and more generally capacity limitations, on the traveling passengers. In previous research it has been conclusively shown that flight delay data and flight centric metrics fail to accurately represent the passenger travel experience and passenger trip delays accurately. This is because they do not capture the effect of passenger itinerary disruptions such as flight cancellations and mis connections. There are several complexities and subtleties underlying the conversion of flight delay data to passenger trip delay data, because of which delay cost to passengers is typically not measured accurately nor understood well. The primary aim of this thesis is to use the passenger-based metric, passenger delay, to capture the effect of itinerary disruptions, and evaluate the performance of the air transportation system from the passenger's perspective. A new methodology to improve current estimates of passenger delays relying solely on publically available data sources is reviewed. Later, the methodology is applied to estimate the magnitude of passenger delays in the US domestic air transportation system for the year 2007. The passenger trip data generated using this methodology is also used to carry out a comprehensive disaggregate analysis of air traffic delays in the US domestic air transportation system for the same timeframe.
by Nitish Umang.
S.M.in Transportation
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Tu, Yufeng. "Air transportation system performance estimation and comparative analysis of departure delays /". College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/4135.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Business and Management. 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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Evans, Antony David 1977. "Responses to airport delays : a system study of Newark International Airport". Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/28254.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics; and, (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2002.Includes bibliographical references (p. 119-121).
Airport delays are a significant problem in the United States air transportation system. Between 1997 and 2000 the number of flights delayed increased by between 20 and 25% per year, despite only a 3 to 5% increase in enplanements per year. Newark International Airport (EWR), one of New York City's primary airports, is one of the airports in the United States most impacted by delays. Newark had the highest percentage of operations delayed in 1999, and was second only to LaGuardia Airport in 2000. Nearly 85% of delays at Newark are caused by adverse weather impacting the airport. Because of limited capacity and a very full schedule operated at the airport, when adverse weather impacts the airport departure operations are severely delayed. Despite this, unlike the national average, delays at Newark have not increased significantly since 1998. This indicates that the airlines, air traffic control (ATC), and the Port Authority of New York and New Jersey have successfully adapted. On June 29, 2000, a research team from MIT visited Newark Airport to identify the key problems and assess the effectiveness of any adaptations made. Results of this study indicate that airspace capacity limitations downstream of the airport become a primary flow constraint at the airport, and that when these constraints occur they are the source of most surface delays. Responses to the delays at Newark have been both tactical and strategic. Key tactical ATC responses examined include the application of restrictions; re-routing with the help of the National Playbook; the use of decision-aiding tools; improved inter-facility communication; and utilization of runway 11-29. Key strategic ATC responses examined include the formation of the Air Traffic Control System Command Center, and the New York airspace redesign. A number of tactical airline responses to delays were also examined, including cancellation of low priority flights and the transfer of the passengers to ground transportation; pre-sequencing of departures; and improved access to information. Key strategic responses examined include changes to the schedule operated at the airport, and particularly flattening out of the banks operated; a new fleet, which requires less maintenance and has greater dispatch reliability; and improved relations with the FAA and Port Authority of New York and New Jersey. After examination of the problems at the 10 most delayed airports in the United States, the applicability of the key responses identified at Newark to these airports was also examined in detail. Those airports for which the most responses were identified to be applicable were Atlanta, San Francisco, Philadelphia and Dallas/Fort Worth. Those responses identified to be most applicable to other airports were the further extension of the National Playbook to other regions, the use of decision aiding tools, airspace redesign, pre-sequencing of departures, and a decrease in the number of operations at the airport. A policy analysis was completed for each of these responses.
by Antony David Evans.
S.M.
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Feyzmahdavian, Hamid Reza. "Performance Analysis of Positive Systems and Optimization Algorithms with Time-delays". Doctoral thesis, KTH, Reglerteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177651.
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Time-delay dynamical systems are used to model many real-world engineering systems, where the future evolution of a system depends not only on current states but also on the history of states. For this reason, the study of stability and control of time-delay systems is of theoretical and practical importance. In this thesis, we develop several stability analysis frameworks for dynamical systems in the presence of communication and computation time-delays, and apply our results to different challenging engineering problems. The thesis first considers delay-independent stability of positive monotone systems. We show that the asymptotic stability of positive monotone systems whose vector fields are homogeneous is independent of the magnitude and variation of time-varying delays. We present explicit expressions that allow us to give explicit estimates of the decay rate for various classes of time-varying delays. For positive linear systems, we demonstrate that the best decay rate that our results guarantee can be found via convex optimization. We also derive a set of necessary and sufficient conditions for asymptotic stability of general positive monotone (not necessarily homogeneous) systems with time-delays. As an application of our theoretical results, we discuss delay-independent stability of continuous-time power control algorithms in wireless networks. The thesis continues by studying the convergence of asynchronous fixed-point iterations involving maximum norm pseudo-contractions. We present a powerful approach for characterizing the rate of convergence of totally asynchronous iterations, where both the update intervals and communication delays may grow unbounded. When specialized to partially asynchronous iterations (where the update intervals and communication delays have a fixed upper bound), or to particular classes of unbounded delays and update intervals, our approach allows to quantify how the degree of asynchronism affects the convergence rate. In addition, we use our results to analyze the impact of asynchrony on the convergence rate of discrete-time power control algorithms in wireless networks. The thesis finally proposes an asynchronous parallel algorithm that exploits multiple processors to solve regularized stochastic optimization problems with smooth loss functions. The algorithm allows the processors to work at different rates, perform computations independently of each other, and update global decision variables using out-of-date gradients. We characterize the iteration complexity and the convergence rate of the proposed algorithm, and show that these compare favourably with the state of the art. Furthermore, we demonstrate that the impact of asynchrony on the convergence rate of the algorithm is asymptotically negligible, and a near-linear speedup in the number of processors can be expected.Tidsfördröjningar uppstår ofta i tekniska system: det tar tid för två ämnen attblandas, det tar tid för en vätska att rinna från ett kärl till ett annat, och det tar tid att överföra information mellan delsystem. Dessa tidsfördröjningar lederofta till försämrad systemprestanda och ibland även till instabilitet. Det är därförviktigt att utveckla teori och ingenjörsmetodik som gör det möjligt att bedöma hur tidsfördröjningar påverkar dynamiska system. I den här avhandlingen presenteras flera bidrag till detta forskningsområde. Fokusligger på att karaktärisera hur tidsfördröjningar påverkar konvergenshastigheten hos olinjära dynamiska system. I kapitel 3 och 4 behandlar vi olinjära system varstillstånd alltid är positiva. Vi visar att stabiliteten av dessa positiva system är oberoende av tidsfördröjningar och karaktäriserar hur konvergenshastigheten hos olinjära positiva system beror på tidsfördröjningarnas storlek. I kapitel 5 betraktar vi iterationer som är kontraktionsavbildningar, och analyserar hur deras konvergens påverkas av begränsade och obegränsade tidsfördröjningar. I avhandlingens sistakapitel föreslår vi en asynkron algoritm för stokastisk optimering vars asymptotiska konvergenshastighet är oberoende av tidsfördröjningar i beräkningar och i kommunikation mellan beräkningselement.
QC 20151204
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Salazar, Rosales Leandro Julian. "Analysing uncertainty and delays in aircraft heavy maintenance". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/analysing-uncertainty-and-delays-in-aircraft-heavy-maintenance(6a64acb7-6780-4dc4-acc5-1497bcf8654b).html.
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This study investigates the influence of unscheduled maintenance activities on delays and disruptions during the execution of aircraft heavy maintenance services by developing a simulation model based on Systems Dynamics (SD) and supported by an Evidential Reasoning (ER) rule model. The SD model studies the complex interrelationship between scheduled and unscheduled tasks and its impact on delays during a maintenance service execution. It was found that the uncertain nature of the unscheduled maintenance tasks hinders the planning, control and allocation of resources, increasing the chances to miss deadlines and incur in cost overruns. Utilising causal loop diagrams and SD simulation the research explored the relevance that the resource allocation management, the precise estimation of the unscheduled tasks and their prompt identification have on the maintenance check duration. The influence that delays and attitudes in the decision-making process have on project performance was also investigated. The ER rule model investigates the uncertainty present during the execution of a maintenance check by providing a belief distribution of the expected unscheduled maintenance tasks. Through a non-parametric discretisation process, it was found that the size and array of distribution intervals play a key role in the model estimation accuracy. Additionally, a sensitivity analysis allowed the examination of the significance that the weight, reliability and dependence of the different pieces of evidence have on model performance. By analysing and combining historical data, the ER rule model provides a more realistic and accurate prediction to analyse variability and ambiguity. This research extends SD capabilities by incorporating the ER rule for analysing system uncertainty. By using the belief distributions provided by the ER model, the SD model can simulate the variability of the process given certain pieces of evidence. This study contributes to the existing knowledge in aircraft maintenance management by analysing, from a different perspective, the impact of uncertain unscheduled maintenance activities on delays and disruptions through an integrated approach using SD and the ER rule. Despite the fact that this research focuses on studying a particular problem in the airline industry, the findings and conclusions obtained could be used to understand and address problems embodying similar characteristics. Therefore, it can be argued that, due to the close similarities between the heavy maintenance process and complex projects, these contributions can be extended to the Project Management field.
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Nguyen, Le Ha Vy. "Stability and stabilization of several classes of fractional systems with delays". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112387/document.
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Nous considérons deux classes de systèmes fractionnaires linéaires invariants dans le temps avec des ordres commensurables et des retards discrets. La première est composée de systèmes fractionnaires à entrées multiples et à une sortie avec des retards en entrées ou en sortie. La seconde se compose de systèmes fractionnaires de type neutre avec retards commensurables. Nous étudions la stabilisation de la première classe de systèmes à l'aide de l'approche de factorisation. Nous obtenons des factorisations copremières à gauche et à droite et les facteurs de Bézout associés: ils permettent de constituer l'ensemble des contrôleurs stabilisants. Pour la deuxième classe de systèmes, nous nous sommes intéressés au cas critique où certaines chaînes de pôles sont asymptotiques à l'axe imaginaire. Tout d'abord, nous réalisons une approximation des pôles asymptotiques afin de déterminer leur emplacement par rapport à l'axe. Le cas échéant, des conditions nécessaires et suffisantes de stabilité H-infini sont données. Cette analyse de stabilité est ensuite étendue aux systèmes à retard classiques ayant la même forme. Enfin, nous proposons une approche unifiée pour les deux classes de systèmes à retards commensurables de type neutre (standards et fractionnaires). Ensuite, la stabilisation d'une sous-classe de systèmes neutres fractionnaires est étudiée. Premièrement, l'ensemble de tous les contrôleurs stabilisants est obtenu. Deuxièmement, nous prouvons que pour une grande classe de contrôleurs fractionnaires à retards il est impossible d'éliminer dans la boucle fermée les chaînes de pôles asymptotiques à l'axe imaginaire si de telles chaînes sont présentes dans les systèmes à contrôlerWe consider two classes of linear time-invariant fractional systems with commensurate orders and discrete delays. The first one consists of multi-input single-output fractional systems with output or input delays. The second one consists of single-input single-output fractional neutral systems with commensurate delays. We study the stabilization of the first class of systems using the factorization approach. We derive left and right coprime factorizations and Bézout factors, which are the elements to constitute the set of all stabilizing controllers. For the second class of systems, we are interested in the critical case where some chains of poles are asymptotic to the imaginary axis. First, we approximate asymptotic poles in order to determine their location relative to the axis. Then, when appropriate, necessary and sufficient conditions for H-infinity-stability are derived. This stability analysis is then extended to classical delay systems of the same form and finally a unified approach for both classes of neutral delay systems with commensurate delays (standard and fractional) is proposed. Next, the stabilization of a subclass of fractional neutral systems is studied. First, the set of all stabilizing controllers is derived. Second, we prove that a large class of fractional controllers with delays cannot eliminate in the closed loop chains of poles asymptotic to the imaginary axis if such chains are present in the controlled systems
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Jennings, Otis Brian. "Multiclass queueing networks with setup delays : stability analysis and heavy traffic approximation". Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/25190.
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Materna, Kathryn. "Analysis of atmospheric delays and asymmetric positioning errors in the global positioning system". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90657.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014.15
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 50-51).
Abstract Errors in modeling atmospheric delays are one of the limiting factors in the accuracy of GPS position determination. In regions with uneven topography, atmospheric delay phenomena can be especially complicated. Current delay models used in analyzing GPS data from the Plate Boundary Observatory (PBO) are successful in achieving millimeter-level accuracy at most locations; however, at a subset of stations, the time series for position estimates contain an unusually large number of outliers. In many cases these outliers are oriented in the same direction. The stations which exhibit asymmetric outliers occur in various places across the PBO network, but they are especially numerous in California's Mammoth Lakes region, which served as a case study for this project. The phenomenon of skewed residuals was analyzed by removing secular trends and variations with periods longer than 75 days from the signal using a median filter. The skewness of the station position residuals was subsequently calculated in the north, east and up directions. In the cases examined, typical position outliers are 5-15 mm. In extreme cases, skewed position residuals, not related to snow on antennas, can be as large as 20 mm. I examined the causes of the skewness through site-by-site comparisons with topographic data and various forms of weather data such as numerical weather models, radiosondes, and satellite images. Analysis suggests that the direction of the skewness is generally parallel to the local topographic gradient at a scale of several kilometers. Comparison with weather data suggests that outlier data points in the Mammoth Lakes region occur when lee waves are likely to form downstream of the Sierra Nevada Mountains. The results imply that coupling between the atmosphere and local topography, e.g. lee waves, is responsible for the phenomenon of skewed residuals.
by Kathryn Materna.
S.B.
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Brown, Neil E. "Sequential phased estimation of ionospheric path delays for improved ambiguity resolution over long GPS baselines /". Connect to thesis, 2006. http://eprints.unimelb.edu.au/archive/00003170.
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Dhulipala, Sudheer. "A System for Travel Time Estimation on Urban Freeways". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/33426.
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Travel time information is important for Advanced Traveler Information Systems (ATIS) applications. People traveling on urban freeways are interested in knowing how long it will take them to reach their destinations, particularly under congested conditions. Though many advances have been made in the field of traffic engineering and ITS applications, there is a lack of practical travel time estimation procedures for ATIS applications.
Automatic Vehicle Identification (AVI) and Geographic Information System (GPS) technologies can be used to directly estimate travel times, but they are not yet economically viable and not widely deployed in urban areas. Hence, data from loop detectors or other point estimators of traffic flow variables are predominantly used for travel time estimation. Most point detectors can provide this data efficiently. Some attempts have been made in the past to estimate travel times from point estimates of traffic variables, but they are not comprehensive and are valid for only particular cases of freeway conditions. Moreover, most of these methods are statistical and thus limited to the type of situations for which they were developed and are not of much general use.
The purpose of current research is to develop a comprehensive system for travel time estimation on urban freeways for ATIS applications. The system is based on point estimates of traffic variables obtained from detectors. The output required from the detectors is flow and occupancy aggregated for a short time interval of 5 minutes. The system for travel time estimation is based on the traffic flow theory rather than statistical methods. The travel times calculated using this system are compared with the results of FHWA simulation package TSIS 5.0 and the estimation system is found to give reasonable and comparable results when compared with TSIS results.Master of Science
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Cummings, Alycia Erin. "Brain and behavior in children with phonological delays phonological, lexical, and sensory system interactions /". Diss., [La Jolla] : [San Diego] : University of California, San Diego ; San Diego State University, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3352373.
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Thesis (Ph. D.)--University of California, San Diego, and San Diego State University, 2009.Title from first page of PDF file (viewed May 8, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 244-259).
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Eberhardt, Brittney Elizabeth. "Teaching Idiomatic Expressions to Children with Developmental Delays Using the PEAK Relational Training System". OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2019.
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AN ABSTRACT OF THE THESIS OF BRITTNEY E. EBERHARDT, for the Master of Science degree in Behavior Analysis and Therapy, presented on August 2016, at Southern Illinois University Carbondale. TITLE: TEACHING IDIOMATIC EXPRESSIONS TO CHILDREN WITH DEVELOPMENTAL DELAYS USING THE PEAK RELATIONAL TRAINING SYSTEM MAJOR PROFESSOR: Dr. Mark R. Dixon Idiomatic expressions are commonly used phrases, which require the listener to interpret the meaning figuratively rather than literally. The purpose of this study was to expand the research in the area of stimulus equivalence to determine whether untaught symmetrical and transitive responding in relation to idiomatic expressions would emerge for two participants with developmental delays. The first phase of the study involved directly training participants to respond with the statement (B stimuli; i.e.: “Go to bed.”) that corresponded with an intraverbal (A stimuli; i.e.: “What do you do at night after you put on your pajamas?”). After participants mastered these relationships, they were directly trained to respond with the idiomatic expression (C stimuli; i.e.: “Hit the hay”) when the experimenter verbally asked, “What is another way to say [A stimuli]?”. The results indicate that both participants achieved mastery criteria during the first phase of the study on A-B relations, however they were unable to demonstrate the derived equivalence A-C relation or C-B relation. After training on the B-C relationship, participants were again able to achieve criteria on the trained relationship and demonstrated some of the derived symmetrical relationships as well as derived transitive relationships. In addition, this study utilized the procedures from the PEAK-E relational training system to aid in replication in research and clinical practice.
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Bharadwaj, V. "Distributed Computation With Communication Delays: Design And Analysis Of Load Distribution Strategies". Thesis, Indian Institute of Science, 1994. http://hdl.handle.net/2005/161.
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Load distribution problems in distributed computing networks have attracted much attention in the literature. A major objective in these studies is to distribute the processing load so as to minimize the time of processing of the entire load. In general, the processing load can be indivisible or divisible. An indivisible load has to be processed in its entirety on a single processor. On the other hand, a divisible load can be partitioned and processed on more than one processor. Divisible loads are either modularly divisible or arbitrarily divisible. Modularly divisible loads can be divided into pre-defined modules and cannot be further sub-divided. Further, precedence relations between modules may exist. Arbitrarily divisible loads can be divided into several fractions of arbitrary lengths which usually do not have any precedence relations. Such type of loads are characterized by their large volume and the property that each data element requires an identical and independent processing. One of the important problems here is to obtain an optimal load distribution, which minimizes the processing time when the distribution is subject to communication delays in the interconnecting links. A specific application in which such loads are encountered is in edge-detection of images. Here the given image frame can be arbitrarily divided into many sub-frames and each of these can be independently processed. Other applications include processing of massive experimental data. The problems associated with the distribution of such arbitrarily divisible loads are usually analysed in the framework of what is known as divisible job theory.
The research work reported in this thesis is a contribution in the area of distributing arbitrarily divisible loads in distributed computing systems subject to communication delays. The main objective in this work is to design and analyseload distribution strategies to minimize the processing time of the entire load in a given network. Two types of networks are considered, namely (i) single-level tree (or star) network and (ii) linear network. In both the networks we assume that there is a non-zero delay associated with load transfer. Further, the processors in the network may or may not be equipped with front-ends (Le., communication co-processors). The main contributions in this thesis are summarized below.
First, a mathematical formulation of the load distribution problem in single-level tree and linear networks is presented. In both the networks, it is assumed that there are (m +1) processors and m communication links. In the case of single-level tree networks, the load to be processed is assumed to originate at the root processor, which divides the load into (m +1) fractions, keeps its own share of the load for processing, and distributes the rest to the child processors one at a time and in a fixed sequence. In all the earlier studies in the literature, it had been assumed that for a load distribution to be optimal, it should be such that all the processors must stop computing at the same time. In this thesis, it is shown that this assumption is in general not true, and holds only for a restricted class of single-level tree networks which satisfy a certain condition. The concept of an equivalent network is introduced to obtain a precise formulation of this condition in terms of the processor and link speed parameters. It is shown that this condition can be used to identify processor-link pairs which can be eliminated from a given network (i.e., these processors need not be given any computational load) without degrading its time performance. It is proved that the resultant reduced network (a network from which these inefficient processor-link pairs have been removed) gives the optimal time performance if and only if the load distribution is such that all the processors stop computing at the same time instant. These results are first proved for the case when the root processor is equipped with a front-end and then extended to the case when it is not. In the latter case, an additional condition, between the speed of the root processor and the speed of each of the links, to be satisfied by the network is specified. An optimal sequence for applying these conditions is also obtained. In the case of linear networks the processing load is assumed to originate at the processor situated at one end of the network. Each processor in the network keeps its own load fraction for computing and transmits the rest to its successor. Here too, in all the earlier studies in the literature, it has been assumed that for the processing time to be a minimum, the load distribution must be such that all the processors must stop computing at the same instant in time. Though this condition has been proved by others to be both necessary and sufficient, a different and more rigorous proof, similar to the case of single-level tree network, is presented here. Finally, the effect of inaccurate modelling on the processing time and on the above conditions are discussed through an illustrative example and it is shown that the model adopted in this thesis gives reasonably accurate results.
In the case of single-level tree networks, so far it has been assumed that the root processor distributes the processing load in a fixed sequence. However, since there are m child processors, a total of m! different sequences of load distribution are possible. Using the closed-form derived for the processing time, it is proved here that the optimal sequence of load distribution follows the decreasing order of link speeds. Further, if physical rearrangement of processors and links is allowed, then it is shown that the optimal arrangement follows a decreasing order of link and processor speeds with the fastest processor at the root. The entire analysis is first done for the case when the root processor is equipped with a front-end, and then extended to the case when it is not. In the without front-end case, it is shown that the same optimal sequencing result holds. However, in an optimal arrangement, the root processor need not be the fastest. In this case an algorithm has been proposed for obtaining optimal arrangement. Illustrative examples are given for all the cases considered.
Next, a new strategy of load distribution is proposed by which the processing time obtained in earlier studies can be further minimized. Here the load is distributed by the root processor to a child processor in more than one installment (instead of in a single installment) such that the processing time is further minimized. First; the case in which all the processors are equipped :tn front-ends is considered. Recursive equations are obtained for a heterogeneous network and these are solved for the special case of a homogeneous network (having identical processors and identical links). Using this closed-form solution, the ultimate limits of performance are explored through an asymptotic analysis with respect to the number of installments and number of processors in the network. Trade-off relationships between the number of installments and the number of processors in the network are also presented. These results are then extended to the case when the processors are not equipped with front-ends. Finally, the efficiency of this new strategy of load distribution is demonstrated by comparing it with the existing single-installment strategy in the literature.
The multi-installment strategy explained above is then applied to linear net-As. Here, .the processing load is assumed to originate at one extreme end of the network, First the case when all the processors are equipped with front-ends is considered. Recursive equations for a heterogeneous network are obtained and these are solved for the special case of a homogeneous network. Using this closed form solution, an asymptotic analysis is performed with respect to the number of installments. However, the asymptotic results with respect to the number of processors was obtained computationally since analytical results could not be obtained. It is found that for a given network, once the number of installments is fixed, there is an optimum number of processors to be used in the network, beyond which the time performance degrades. Trade-off relationships between the number of installments and the number of processors is obtained. These results are then extended to the case when the processors are not equipped with front-ends. Comparisions with the existing single-installment strategy is also done.
The single-installment strategy discussed in the literature has the disadvantage that the front-ends of the processors are not utilized efficiently in a linear network. This is due to the fact that a processor starts computing its own load fraction only after the entire load to be communicated through its front-end has been received. In this thesis, a new strategy is proposed in which a processor starts computing as soon as it receives its load fraction, simultaneously allowing its front-end to receive and transmit load to its successors. Recursive equations are developed and solved for the special case of a heterogeneous network in which the processors and links are arranged in the decreasing order of speeds. Further, it is shown that in this strategy, if the processing load originates in the interior of the network, the sequence of load distribution should- be such that the load should be first distributed to the side with a lesser number of processors. An expression for the optimal load origination point in the network is derived. A comparative study of this strategy with an earlier strategy is also presented. Finally, it is shown that even though the analysis is carried out for a special case of a heterogeneous network, this load distribution strategy can also be applied to a linear network in which the processors and links are arbitrarily arranged and still obtain a significant improvement in the time performance.
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Reber, David Patrick. "Exponential Stability of Intrinsically Stable Dynamical Networks and Switched Networks with Time-Varying Time Delays". BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7136.
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Dynamic processes on real-world networks are time-delayed due to finite processing speeds and the need to transmit data over nonzero distances. These time-delays often destabilize the network's dynamics, but are difficult to analyze because they increase the dimension of the network.We present results outlining an alternative means of analyzing these networks, by focusing analysis on the Lipschitz matrix of the relatively low-dimensional undelayed network. The key criteria, intrinsic stability, is computationally efficient to verify by use of the power method. We demonstrate applications from control theory and neural networks.
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Wirzberger, Maria, René Schmidt, Maria Georgi, Wolfram Hardt, Guido Brunnett y Günter Daniel Rey. "Effects of system response delays on elderly humans’ cognitive performance in a virtual training scenario". Springer Nature, 2019. https://monarch.qucosa.de/id/qucosa%3A34294.
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Observed influences of system response delay in spoken human-machine dialogues are rather ambiguous and mainly focus on perceived system quality. Studies that systematically inspect effects on cognitive performance are still lacking, and effects of individual characteristics are also often neglected. Building on benefits of cognitive training for decelerating cognitive decline, this Wizard-of-Oz study addresses both issues by testing 62 elderly participants in a dialogue-based memory training with a virtual agent. Participants acquired the method of loci with fading instructional guidance and applied it afterward to memorizing and recalling lists of German nouns. System response delays were randomly assigned, and training performance was included as potential mediator. Participants’ age, gender, and subscales of affinity for technology (enthusiasm, competence, positive and negative perception of technology) were inspected as potential moderators. The results indicated positive effects on recall performance with higher training performance, female gender, and less negative perception of technology. Additionally, memory retention and facets of affinity for technology moderated increasing system response delays. Participants also provided higher ratings in perceived system quality with higher enthusiasm for technology but reported increasing frustration with a more positive perception of technology. Potential explanations and implications for the design of spoken dialogue systems are discussed.
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Oztas, Ahmet. "The mitigation of the effects of delays in construction projects : a knowledge based system approach". Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.683471.
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Zhang, Li y Xi Ren. "A two-factor evaluation of bus delays based on GIS-T database and simulation". Thesis, Högskolan i Gävle, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-7985.
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During the urbanization process, vehicles quantity increase with expansion in population. Under this situation, bus transportation system also suffers from bus delay. Bus delay could be caused by a series of factors, for instance, overload passengers, traffic jam, traffic accident and other unpredictable situations. Therefore, choosing crucial elements to efficiently evaluate bus delay is a complex problem in bus delay researches and operation management. The thesis propose an approach to evaluate and explain bus delay by two elements: traffic congestion and passengers’ waiting time. Those two elements would represent the action of external and internal factors on bus operation. This approach could be adaptive to explain the reasons for bus delays, thus to help the optimization of bus lines and give useful information for decision making of transportation company. To achieve the research aim, a GIS-T database was created by combining the GIS database and TIS database. Spatial data as well as attribute data are combined in the database to represent the crucial information for bus delay. Based on GIS-T the database, the impact of traffic congestion and passengers’ waiting time was calculated using the bus line simulation. By implementing the above steps, the main cause of bus delay was studied. A case study application of this method is narrated; focusing on optimize the bus system of Guiyang city, South China. Different methods are used to find out the problem of system and the reason for delay. Moreover, optimization suggestion is proposed according to result. Compared with other methods, the two-factor method has the advantage of locating the reason of delay for each station. The time performance is not superior to other methods. By comparing the situation of adjacent station, the proportion of traffic congestion and overload passenger in bus delay was determined. The two-factor method is applicable for other transit system in different cities which has similar structure as Guiyang. However, for cities with other structure, a feasibility should be made to select an appropriate model.
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Widener, Scott D. "Measuring Airport Efficiency with Fixed Asset Utilization to Minimize Airport Delays". Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/485.
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Deregulation of the airlines in the United States spawned a free-for-all system which led to a variety of agents within the aviation system all seeking to optimize their own piece of the aviation system, and the net result was that the aviation system itself was not optimized in aggregate, frequently resulting in delays. Research on the efficiency of the system has likewise focused on the individual agents, primarily focusing on the municipalities in an economic context, and largely ignoring the consumer. This paper develops the case for a systemic efficiency measurement which incorporates the interests of the airlines and the consumers with those of the airport operating municipalities in three different Data Envelopment Analysis (DEA) models: traditional Charnes-Cooper-Rhodes and Banker-Charnes-Cooper models, and a Directional Output Distance Function model, devised and interpreted using quality management principles. These models were combined to allow the resulting efficiencies of the operating configurations of the given airport to predict the efficiency of the associated airport. Based upon regression models, these efficiency measurements can be used as a diagnostic for improving the efficiency of the entire United States airspace, on a systemic basis, at the individual airport configuration level. An example analysis using this diagnostic is derived in the course of the development and description of the diagnostic and two additional case studies are presented.
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Abdallah, Fadel. "Optimization and Scheduling on Heterogeneous CPU/FPGA Architecture with Communication Delays". Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0301.
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Le domaine de l'embarqué connaît depuis quelques années un essor important avec le développement d'applications de plus en plus exigeantes en calcul auxquels les architectures traditionnelles à base de processeurs (mono/multi cœur) ne peuvent pas toujours répondre en termes de performances. Si les architectures multiprocesseurs ou multi cœurs sont aujourd'hui généralisées, il est souvent nécessaire de leur adjoindre des circuits de traitement dédiés, reposant notamment sur des circuits reconfigurables, permettant de répondre à des besoins spécifiques et à des contraintes fortes particulièrement lorsqu'un traitement temps-réel est requis. Ce travail présente l'étude des problèmes d'ordonnancement dans les architectures hétérogènes reconfigurables basées sur des processeurs généraux (CPUs) et des circuits programmables (FPGAs). L'objectif principal est d'exécuter une application présentée sous la forme d'un graphe de précédence sur une architecture hétérogène CPU/FPGA, afin de minimiser le critère de temps d'exécution total ou makespan (Cmax). Dans cette thèse, nous avons considéré deux cas d'étude : un cas d'ordonnancement qui tient compte des délais d'intercommunication entre les unités de calcul CPU et FPGA, pouvant exécuter une seule tâche à la fois, et un autre cas prenant en compte le parallélisme dans le FPGA, qui peut exécuter plusieurs tâches en parallèle tout en respectant la contrainte surfacique. Dans un premier temps, pour le premier cas d'étude, nous proposons deux nouvelles approches d'optimisation, GAA (Genetic Algorithm Approach) et MGAA (Modified Genetic Algorithm Approach), basées sur des algorithmes génétiques. Nous proposons également de tester un algorithme par séparation et évaluation (méthode Branch & Bound). Les approches GAA et MGAA proposées offrent un très bon compromis entre la qualité des solutions obtenues (critère d'optimisation de makespan) et le temps de calcul nécessaire à leur obtention pour résoudre des problèmes à grande échelle, en comparant à la méthode par séparation et évaluation (Branch & Bound) proposée et l'autre méthode exacte proposée dans la littérature. Dans un second temps, pour le second cas d'étude, nous avons proposé et implémenté une méthode basée sur les algorithmes génétiques pour résoudre le problème du partitionnement temporel dans un circuit FPGA en utilisant la reconfiguration dynamique. Cette méthode fournit de bonnes solutions avec des temps de calcul raisonnables. Nous avons ensuite amélioré notre précédente approche MGAA afin d'obtenir une nouvelle approche intitulée MGA (Multithreaded Genetic Algorithm), permettent d'apporter des solutions au problème de partitionnement. De plus, nous avons également proposé un algorithme basé sur le recuit simulé, appelé MSA (Multithreaded Simulated Annealing). Ces deux approches proposées, basées sur les méthodes métaheuristiques, permettent de fournir des solutions approchées dans un intervalle de temps très raisonnable aux problèmes d'ordonnancement et de partitionnement sur système de calcul hétérogèneThe domain of the embedded systems becomes more and more attractive in recent years with the development of increasing computationally demanding applications to which the traditional processor-based architectures (either single or multi-core) cannot always respond in terms of performance. While multiprocessor or multicore architectures have now become generalized, it is often necessary to add to them dedicated processing circuits, based in particular on reconfigurable circuits, to meet specific needs and strong constraints, especially when real-time processing is required. This work presents the study of scheduling problems into the reconfigurable heterogeneous architectures based on general processors (CPUs) and programmable circuits (FPGAs). The main objective is to run an application presented in the form of a Data Flow Graph (DFG) on a heterogeneous CPU/FPGA architecture in order to minimize the total running time or makespan criterion (Cmax). In this thesis, we have considered two case studies: a scheduling case taking into account the intercommunication delays and where the FPGA device can perform a single task at a time, and another case taking into account parallelism in the FPGA, which can perform several tasks in parallel while respecting the constraint surface. First, in the first case, we propose two new optimization approaches GAA (Genetic Algorithm Approach) and MGAA (Modified Genetic Algorithm Approach) based on genetic algorithms. We also propose to compare these algorithms to a Branch & Bound method. The proposed approaches (GAA and MGAA) offer a very good compromise between the quality of the solutions obtained (optimization makespan criterion) and the computational time required to perform large-scale problems, unlike to the proposed Branch & Bound and the other exact methods found in the literature. Second, we first implemented an updated method based on genetic algorithms to solve the temporal partitioning problem in an FPGA circuit using dynamic reconfiguration. This method provides good solutions in a reasonable running time. Then, we improved our previous MGAA approach to obtain a new approach called MGA (Multithreaded Genetic Algorithm), which allows us to provide solutions to the partitioning problem. In addition, we have also proposed an algorithm based on simulated annealing, called MSA (Multithreaded Simulated Annealing). These two proposed approaches which are based on metaheuristic methods provide approximate solutions within a reasonable time period to the scheduling and partitioning problems on a heterogeneous computing system
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Gupta, Shubham Ph D. Massachusetts Institute of Technology. "Transient analysis of D(t)/M(t)/1 queuing system with applications to computing airport delays". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61194.
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Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 44-45).
This thesis is motivated by the desire to estimate air traffic delays at airports under a range of assumptions about the predictability of (a) inter-arrival times of demands (arrivals and departures) and (b) service times of aircraft movements (landings and takeoffs). It consists of two main parts. In the first, a transient analysis of a D(t)/M(t)/1 queuing system is presented. The reason for focusing on such a system is that it may be useful in evaluating some of the benefits of a future Air Traffic Management (ATM) system, such as the Next Generation Air Transportation System (NGATS or NextGen) currently being developed in the United States. One of the main features of these future ATM systems will be high predictability and regularity of the inter-arrival times of airport demands, i.e., a nearly deterministic demand process. This will be achieved through significant reductions in aircraft trajectory uncertainty, with the expectation that airport delays will also decrease substantially as a result. We develop a novel, computationally-efficient numerical approach for solving D(t)/M(t)/1 queuing systems with general, dynamic demand and service rates. We also discuss the complexity of the approach and some characteristics of the resulting solutions. In the second part of the thesis, we use a set of models of dynamic queuing systems, in addition to our D(t)/M(t)/1 model to explore the range of values that airport delays may assume under different sets of assumptions about the level of uncertainty associated with demand inter-arrival times and with service times. We thus compute airport delays under different queuing systems in a dynamic setting (where demand and service rates are time-varying) to capture the entire range of uncertainties expected during the deployment of various future ATM system technologies. The specific additional models we consider are: a deterministic D(t)/D(t)/1 model in which it is assumed that airport demands for landings and takeoffs occur at exactly as scheduled; and a M(t)/Ek(t)/1 model which, because of the "richness" of the family of Erlang distributions, Ek, can be used to approximate most M(t)/G(t)/1 models that may arise in airport applications. It can be seen that these models, when used together, provide bounds on estimated airport delays, with the D(t)/D(t)/1 model most likely to offer a lower bound and the M(t)/M(t)/1 model (i.e., the special case of M(t)/Ek(t)/1 with k = 1), an upper bound. We show through a set of examples based on a few of the busiest airports in the United States that: the closeness of the delay estimates provided by the different models depend on the level of congestion at an airport and the relative shapes of the dynamic profiles of capacity and demand at the airport; the difference (on a "percentage" basis) between the estimates provided by the deterministic model and the stochastic ones is largest for uncongested airports and decreases as the level of congestion increases; D(t)/M(t)/1 and M(t)/D(t)/1 produce estimates of the same order of magnitude, and reflect delays in the presence of "moderate" uncertainty at an airport; and delays under a D(t)/M(t)/1 queuing system are always higher than under a M(t)/D(t)/1 system.
by Shubham Gupta.
S.M.
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Kime, Dena LaRae. "TRAINING DEICTIC RELATIONS TO CHILDREN WITH DEVELOPMENTAL DELAYS THROUGH THE USE OF THE PEAK RELATIONAL TRAINING SYSTEM". OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1794.
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Children with developmental delays often do not acquire perspective taking skills without training. These skills are imperative to the ability to relate to others socially and the development of appropriate social behavior. They may lack the ability to recognize that another person’s view may differ from their own, or that reality may differ from appearance. This study used deictic relational training to aid in the development of a ‘Theory of Mind’ and the acquisition of perspective taking skills. The PEAK relational training system was used in a special education classroom to train YOU and I relations, as well as YOU and I reversal, to two nine year old students with intellectual disability. Multiple exemplar training was then used to promote the generalization of these perspective taking skills to an in situ deceptive container task. One subject participated in the first two training phases, but was absent for the remainder of the study. The second subject successfully completed all training phases and was then able to correctly respond when asked to report what the perspective of another individual would be.
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Frank, Lawrence H. "Effects of visual display and motion system delays on operator performance and uneasiness in a driving simulator". Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/54315.
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Liu, Fei. "Dual-user haptic training system". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI082/document.
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Dans le secteur médical tout particulièrement, la qualité du geste est primordiale et les professionnels doivent être formés par la pratique pour acquérir un niveau de compétences compatible avec l'exercice de leur métier. Depuis une dizaine d'année, les simulateurs informatiques aident les apprenants dans de nombreux apprentissages mais ils doivent encore être associés à des travaux pratiques sur mannequins, animaux ou cadavres, qui pourtant n'offrent pas toujours suffisamment de réalisme par rapport aux vrais patients, et sont coûteux à l'usage. Aussi, leur formation s'achève généralement sur de vrais patients, ce qui présente des risques. Les simulateurs haptiques (fournissant une sensation d'effort) deviennent aujourd'hui une solution plus appropriée car ils peuvent reproduire des efforts résistant réalistes et proposer une infinité de cas d'étude pré-enregistrés. Cependant, apprendre seul sur un simulateur n'est pas toujours aussi efficace qu'un apprentissage "à quatre mains" (celles de l'instructeur et de l'apprenant manipulant les mêmes outils en coopération). Cette étude propose donc un système haptique de formation pratique à deux utilisateurs : l'instructeur et l'apprenant, interagissant chacun à travers leur propre interface haptique. Ils collaborent ainsi, avec des outils et un environnement de travail soit réels (l'outil est manipulé par un robot) soit virtuels. Une approche énergétique, faisant appel notamment à la modélisation par port-Hamiltonien, a été utilisée pour garantir la stabilité et la robustesse du système. Une étude comparative (en simulation) avec deux autres systèmes haptiques multi utilisateurs a montré l'intérêt de ce nouveau système pour la formation pratique. Il a été développé et validé expérimentalement sur des interfaces à un seul degré de liberté. Son extension à six degrés de liberté est facilitée par les choix de modélisation. Afin de pouvoir utiliser le système quand les deux protagonistes sont éloignés, cette étude propose des pistes d'amélioration qui ne sont pas encore optimiséesMore particularly in the medical field, gesture quality is primordial. Professionals have to follow hands-on trainings to acquire a sufficient level of skills in the call of duty. For a decade, computer based simulators have helped the learners in numerous learnings, but these simulations still have to be associated with hands-on trainings on manikins, animals or cadavers, even if they do not always provide a sufficient level of realism and they are costly in the long term. Therefore, their training period has to finish on real patients, which is risky. Haptic simulators (furnishing an effort feeling) are becoming a more appropriated solution as they can reproduce realist efforts applied by organs onto the tools and they can provide countless prerecorded use cases. However, learning alone on a simulator is not always efficient compared to a fellowship training (or supervised training) where the instructor and the trainee manipulate together the same tools. Thus, this study introduces an haptic system for supervised hands-on training: the instructor and the trainee interoperate through their own haptic interface. They collaborate either with a real tool dived into a real environment (the tool is handled by a robotic arm), or with a virtual tool/environment. An energetic approach, using in particular the port-Hamiltonian modeling, has been used to ensure the stability and the robustness of the system. This system has been designed and validated experimentally on a one degree of freedom haptic interface. A comparative study with two other dual-user haptic systems (in simulation) showed the interest of this new architecture for hands-on training. In order to use this system when both users are away from each other, this study proposes some enhancements to cope with constant communication time delays, but they are not optimized yet
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Jenvald, Mattias y Mikael Hovmöller. "Reducing Delays for Unplanned Maintenance of Service Parts in MRO Workshops : A case study at an aerospace and defence company". Thesis, Linköpings universitet, Produktionsekonomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-167203.
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Service parts sometimes break down unexpectedly and require maintenance. The irregular nature of the need for this type of maintenance makes forecasting difficult and unreliable. Saab currently experiences problems with long delays when performing unplanned maintenance of service parts used in the two models of Gripen aircraft, Gripen C and Gripen D. These delays are source of monetary waste, as late delivery of maintained service parts results in Saab having to pay penalty fines to the customers. The purpose of this master thesis was to analyze data collected during a case study at Saab in Linköping, and suggest improvements for how to reduce these delays. This study focused on analyzing what caused the delays, and how the information provided by the customers can be used by the operative planners at the Maintenance, Repair \& Overhaul (MRO) workshops in order to be more efficient. The data was collected during the case study using semi-structured interviews of 16 people working with the current system, as well as by collecting historical data from an internal database at Saab. This data was analyzed in parallel with a literature study of relevant research related to service parts supply chains, MRO workshops, and unplanned maintenance operations. The analysis showed that there were four types of interruptions of maintenance; Internal stock-out of spare parts, internal stock-out of sub-units, external delays at the Original Equipment Manufacturer (OEM), and internal equipment breakdowns. A root cause analysis found that the four root causes of delays were: Saab does not have any contracts that incentivizes their OEM's to deliver on time. The data from the technical report is not used to provide the operative planners with information about incoming orders. The MRO workshops do not have a standardized system for prioritizing maintenance of service parts. The MRO workshops currently lacks a method for predicting certain types of machine breakdowns.
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Odimabo, Onengiyeofori. "Risk management system to guide building construction projects in developing countries : a case study of Nigeria". Thesis, University of Wolverhampton, 2016. http://hdl.handle.net/2436/618537.
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Project risk assessment is an effective tool for planning and controlling cost, time and achieving the technical performance of a building construction project. Construction projects often face a lot of uncertainties, which places building construction projects at the risk of cost, time overruns as well as poor quality delivery. Considering the limited resources of developing countries, there is need to complete building projects on-time, on-budget, and to meet optimal quality hence, risk management is an important part of the decision making process in construction industry as it determines the success or failure of construction projects. In line with this need, this research aims to establish a system to improve the time, cost and quality performance of building construction projects in developing countries, through a comprehensive risk management model that ensures the expectations of clients are met. To achieve the aim of this research, a mixed methodological approach was adopted. Through the review of literature, a conceptual risk management framework suitable to elaborate risk assessment of building construction projects especially for developing countries was developed. A questionnaire survey using a nonprobability sampling technique was conducted to elicit information from construction professionals in Nigeria to assess their perception of 79 risk factors identified from literature review based on the likelihood of occurrence and impact on projects using a five point scale. Responses from 343 construction professionals were drawn from 305 contractors and subcontractors and 38 clients (private and public) within the Nigerian construction sector. Response data was subjected to descriptive statistics to depict the frequency distribution and central tendency of responses. Subsequently, the risk acceptability matrix (RAM) was adopted to categorise and prioritise risk factors. 27 critical risks that affect building construction projects were identified. A Bayesian Belief Network (BBN) model was developed by structural learning and used to examine the cause and effect relationship amongst the 27 critical risk factors. The developed BBN model was subjected to validation using a multiple case study of two building construction projects in Nigeria. The result showed the interrelation between the 27 risk factors and how they contributed to cost and time overruns as well as quality problems. The critical risks directly affecting the cost of building construction project were: fluctuation of material prices; health and safety issues; bribery and corruption; material wastage; poor site management and supervision; and time overruns. The critical factors identified to directly affect quality were: supply of defective materials; working under harsh conditions; improper construction methods; lack of protective equipment; ineffective time allocation; poor communication between involved stakeholders; and unsuitable leadership style. Time overruns on building construction projects was directly caused by: quality problems; low productivity; improper construction methods; poor communication between involved parties; delayed payments in contracts; and poor site management and supervision. As a consolidation of the findings of this research, a BBN model for identifying risk factors that directly affect time, cost and quality on building construction projects has been developed which has the potential for assisting construction stake holders to manage risks on their projects. In view of the findings, a best practice system for risk management in building construction projects in Nigeria has been developed with an implementation guide to help building construction practitioners to successfully implement risk management on their building construction projects. Suitable risk responses, also in the form of recommendations have been identified. The strategies include actions to be taken to respond to risks based on their perceived significance or acceptability as well as some positive risk responses, such as exploiting, sharing, enhancing and accepting, and other negative risk responses, such as avoidance, mitigation transfer and acceptance.
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Daher, Jalil. "Exposure of endothelial cells to physiological levels of myeloperoxidase modified LDL delays pericellular fibrinolysis and reduces cell motility". Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209337.
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Cardiovascular diseases are considered the first cause of death in westernized societies. They are directly linked to atherosclerosis, a clinical condition characterized by a thickening of the arterial wall. Atherosclerosis is in his turn linked to various genetic and environmental factors; among those factors are high oxidized LDL levels and endothelial dysfunction. In the present study, we have analyzed in vitro the effect of myeloperoxidase oxidized LDL on endothelial cells at the level of fibrinolysis and cell motility.In the first part of the work, we measured fibrinolysis in real time at the surface of endothelial cells. Our results suggest that myeloperoxidase oxidized LDL interferes with the regulation of fibrinolysis by endothelial cells by decreasing their pro-fibrinolytic activity. This effect was not related to a modification in expression of major regulators of fibrinolysis such as PAI-1 and t-PA. Our data link the current favorite hypothesis that oxidized LDL has a causal role in atheroma plaque formation with an old suggestion that fibrin may also play a causal role. A model that best explains our results would be as follows: oxidized LDL increases fibrin deposition on endothelial cells which will increase their permeability resulting in more oxidized LDL infiltration into the subendothelial space of the arterial wall initiating atherogenesis.
In the second part of the work, we investigated the effect of myeloperoxidase oxidized LDL at the level of endothelial cell motility. We have shown that oxidized LDL is able to decrease cell migration, wound healing and tubulogenesis in endothelial cells. Those effects were not associated with any alteration at the level of neither cell viability nor proliferation. Subsequent gene expression analyses enabled us to link the oxidized LDL induced phenotypical changes in the cells to a change in expression of both microRNA-22 and Heme Oxygenase 1 genes. Our observations suggest a novel role of oxidized LDL not only as an important factor in the initiation of atheromatous lesions, but also as a potential player in the progression of the atherosclerosis disease by impeding blood vessel repair and wound healing at the sites of lesions.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Lazem, Shaimaa. "Analysis of the Relationships between Changes in Distributed System Behavior and Group Dynamics". Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/26732.
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The rapid evolution of portable devices and social media has enabled pervasive forms of distributed cooperation. A group could perform a task using a heterogeneous set of the devices (desktop, mobile), connections (wireless, wired, 3G) and software clients. We call this form of systems Distributed Dynamic Cooperative Environments (DDCEs).
Content in DDCEs is created and shared by the users. The content could be static (e.g., video or audio), dynamic (e.g.,wikis), and/or Objects with behavior. Objects with behavior are programmed objects that take advantage of the available computational services (e.g., cloud-based services).
Providing a desired Quality of Experience (QoE) in DDCEs is a challenge for cooperative systems designers. DDCEs are expected to provide groups with the utmost flexibility in conducting their cooperative activities. More flexibility at the user side means less control and predictability of the groupsâ behavior at the system side.
Due to the lack of Quality of Service (QoS) guarantees in DDCEs, groups may experience changes in the system behavior that are usually manifested as delays and inconsistencies in the shared state. We question the extent to which cooperation among group members is sensitive to system changes in DDCEs. We argue that a QoE definition for groups should account for cooperation emergence and sustainability.
An experiment was conducted, where fifteen groups performed a loosely-coupled task that simulates social traps in a 3D virtual world. The groups were exposed to two forms of system delays. Exo-content delays are exogenous to the provided content (e.g., network delay). Endo-content delays are endogenous to the provided content (e.g., delay in processing time for Objects with behavior). Groups' performance in the experiment and their verbal communication have been recorded and analyzed.
The results demonstrate the nonlinearity of groups' behavior when dealing with endo-content delays. System interventions are needed to maintain QoE even though that may increase the cost or the required resources.
Systems are designed to be used rather than understood by users. When the system behavior changes, designers have two choices. The first is to expect the users to understand the system behavior and adjust their interaction accordingly. That did not happen in our experiment. Understanding the system behavior informed groups' behavior. It partially influenced how the groups succeeded or failed in accomplishing its goal. The second choice is to understand the semantics of the application and provide guarantees based on these semantics. Based on our results, we introduce the following design guidelines for QoE provision in DDCEs.
â ¢If possible the system should keep track of information about group goals and add guarding constraints to protect these goals.
â ¢QoE guarantees should be provided based on the semantics of the user-generated content that constitutes the group activity.
â ¢Users should be given the option to define the content that is sensitive to system changes (e.g., Objects with behavior that are sensitive to delays or require intensive computations) to avoid the negative impacts of endo-content delays.
â ¢Users should define the Objects with behavior that contribute to the shared state in order for the system to maintain the consistency of the shared state.
â ¢Endo-content delays were proven to have significantly negative impacts on the groups in our experiment compared to exo-content delays. We argue that system designers, if they have the choice, should trade processing time needed for Objects with behavior for exo-content delay.Ph. D.
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Mohleji, Nandita. "Decision Modeling Framework to Minimize Arrival Delays from Ground Delay Programs". Thesis, The George Washington University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3740141.
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Convective weather and other constraints create uncertainty in air transportation, leading to costly delays. A Ground Delay Program (GDP) is a strategy to mitigate these effects. Systematic decision support can increase GDP efficacy, reduce delays, and minimize direct operating costs. In this study, a decision analysis (DA) model is constructed by combining a decision tree and Bayesian belief network. Through a study of three New York region airports, the DA model demonstrates that larger GDP scopes that include more flights in the program, along with longer lead times that provide stakeholders greater notice of a pending program, trigger the fewest average arrival delays. These findings are demonstrated to result in a savings of up to $1,850 per flight. Furthermore, when convective weather is predicted, forecast weather confidences remain the same level or greater at least 70% of the time, supporting more strategic decision making. The DA model thus enables quantification of uncertainties and insights on causal relationships, providing support for future GDP decisions.
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Deng, Yang. "Delay estimation and predictor-based control of time-delay systems with a class of various delays". Thesis, Ecole centrale de Nantes, 2020. http://www.theses.fr/2020ECDN0014.
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Le retard est un phénomène largement présent dans les systèmes de commande(i.e.retard physique, latence de communication, temps de calcul) et peut en dégrader les performances ou même les déstabiliser. Si le retard est faible, la stabilité en boucle fermée peut être garantie par des lois de commande conventionnelles mais ces techniques ne sont plus efficaces si le retard est long. Cette thèse est dédiée à la commande des systèmes à retard avec retards longs inconnus ou avec des retards incertains. Pour compenser les retards longs, la commande prédictive est adoptée et des techniques d’estimation de retard sont développées. Selon les différents types de systèmes et de retards, trois objectifs sont visés dans la thèse. Le premier objectif considère la commande des systèmes linéaires avec retards constants inconnus pour lesquels un nouvel estimateur de retard est proposé pour estimer les retards inconnus. Le retard estimé est ensuite utilisé dans la commande prédictive pour stabiliser le système. Le deuxième objectif se concentre sur la stabilisation pratique des systèmes commandés à distance avec des retards inconnus variants. Dans ce cas, les retards sont estimés de manière pratique : une boucle de communication spécifique est utilisée pour estimer le retard en temps fini puis le système est stabilisé par une commande prédictive. Les tests expérimentaux réalisés sur un réseau WiFi ont montré que l’algorithme permet d’estimer de manière robuste les retards variants. Le dernier objectif est consacré à la commande des systèmes commandés en réseau avec retards variants. La commande prédictive discrète est utilisée pour compenser les retards longs et variants et les ré-ordonnancements de paquets dans le canal capteur-contrôleur sont également considérés. De plus, cette méthode est validée par l’asservissement visuel d’un pendule inverse commandé en réseau. Les performances obtenues sont meilleures que les méthodes de commande non-prédictives classiquesTime-delay is a widely-found phenomenon (i.e. physical dead time, communication latency, computation time) in real control systems, which can degrade the performances of the system or destabilize the system. If the time-delay is small, then the closed-loop stability can be guaranteed with conventional control techniques; but these techniques are no longer effective if the time-delay is long. This thesis is dedicated to the control of time-delaysystemswithunknown or uncertain long time-delays. In order to compensate long time-delays, the predictor-based control technique is adopted, and the delay estimation techniques are developed to assist the predictor-based controller. According to the different types of the systems and the time-delays, three objectives are analyzed in the thesis. The first objective considers the control of LTI systems with unknown constant delays, a new type of delay estimator is proposed to estimate the unknown time-delays, then it is plugged into apredictor-based controller to stabilize the system. The second objective focuses on the practical stabilization of remote control systems with unknown time-varying delays, at this time, the time-delays are estimated by a practical way: a specific communication loop is used to estimate the round-trip delay in finite time, and the system is stabilized with a predictor-based controller. This practical delay estimation algorithm is implemented on a real WiFi network, it can estimate the time-varying delays with good performances and robustness. The last objective is devoted to the control of networked control systems with time-varying delays, the discrete predictor-based control techniques are used to compensate long time-varyingdelays,and the packet reordering in the sensor-to-controller channel is also considered. Moreover, this control solution is validated on a networked visual servo inverted pendulum system, and the control performances are fairly better than the non-predictive control methods
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Krampell, Martin. "About time : Temporality in interaction". Thesis, Linköpings universitet, Institutionen för datavetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-108353.
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Ever since the inception of the modern computer, researchers and designers alike have been interested in the effects of system delays on users. The current study was conducted in order to examine the most central issues to the field of temporality in interaction, and presents a consolidation of a selection of publications on the subject. A distinction between two types of interactive systems, discretionary and continuous, is proposed in order to situate previous studies by the system being studied. The type of control being exerted by users differs on a fundamental level between the two types, hence affecting the effects of delays. Furthermore, an experiment was conducted to examine the effects of constant, sub-second system delays in discretionary tasks using a digitalised version of the Trail Making Test (FR-TMT, Summala et al., 2008). The experiment yielded but one significant result in form of an improvement in user response time as delays were increased. The other results showed no significant positive or negative effect of increased delays. These results are indicative that the chosen delays do not have any detrimental effects on users, in accordance with the presently coined ’theory of task interruption’. This theory considers delays as either interruptive or non-interruptive and maintains that only delays that disrupt user work-flow are to be removed from interactive systems. The current study gives reason to why some delays can be positive to user interaction, or in themselves be informative of system status, and be an integral part of a feedback structure. Further research is needed before all aspects of system delays are fully understood. New ways of looking at delays and using them in system design, like predictability and predictivity, are becoming more prevalent, and may become the focus of research and temporal design in the near future.
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Gallage, Roshini Samanthi. "Approximation Of Continuously Distributed Delay Differential Equations". OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2196.
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We establish a theorem on the approximation of the solutions of delay differential equations with continuously distributed delay with solutions of delay differential equations with discrete delays. We present numerical simulations of the trajectories of discrete delay differential equations and the dependence of their behavior for various delay amounts. We further simulate continuously distributed delays by considering discrete approximation of the continuous distribution.
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Lu, Mu-Chiao. "Delay identification and model predictive control of time delayed systems". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22045.
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Two research problems involving the class of linear and nonlinear time delayed systems are addressed in this thesis. The first problem concerns delay identification in time delayed systems. The second problem concerns in the design of receding horizon controllers of time delayed systems. Original solutions to both problems are provided and their efficiency is assessed with examples and applications. In this thesis, delay identification problem is tackled first. Steepest descent and generalized Newton type delay identifiers are proposed. The receding horizon control problems for delayed systems are extensively investigated next. For both of linear and nonlinear time delayed systems, asymptotically stabilizing receding control laws are delivered. Finally, to reduce the conservativeness caused by delay uncertainties, an adaptive receding horizon strategy which combines feedback control with on-line delay identification is also discussed. The thesis demonstrates the following: (1) Development of delay identifiers which are independent of system parameter identification and robust with respect to errors in the measured trajectory and exogenous input function. (2) Development of practical delay identifiers for linear and nonlinear time delayed systems for reducing conservativeness of existing robust control designs. (3) Development of model predictive control techniques for linear and nonlinear time delayed systems. (4) Rigorous proofs of the asymptotic stability of the proposed model predictive controllers. (5) Application of on-line estimation schemes to the proposed model predictive controllers.Cette thèse aborde deux problématiques de recherche relatives à la classe des systèmes linéaires et non-linéaires avec retard. Le premier problème a trait à l'identification des retards dans les systèmes avec retard. Le second problème consiste à concevoir des commandes d'horizon fuyant pour les systèmes avec retard. Des solutions originales sont proposées pour ces deux problèmes et leur efficacité est évaluée à l'aide d'exemples et d'applications. Dans cette thèse, le problème de l'identification du retard est abordé en premier. La descente prononcée et les identificateurs du retard du type Newton généralisé sont proposés. Les problèmes de commande d'horizon fuyant pour les systèmes avec retard sont explorés. Tant pour les systèmes avec retard linéaires que non-linéaires, des règles de commandes asymptotiquement stabilisatrice pour les horizons fuyants sont proposées. Finalement, pour reduire conservatisme untraduit par l'incertitude du retard, une stratégie d'horizon fuyant adaptif, qui combine le contrôle de retour avec le retard d'identification en ligne, est aussi discuté. La thèse démontre les points suivants. (1) Développement d'identificateurs de retard qui sont indépendants de l'identification des paramètres du système et robuste à l'égard des erreurs de trajectoire mesurée et de fonctions d'entreés externes. (2) Développement d'identificateurs de retard pratiques pour les systèmes avec retard linéaires et non-linéaires pour réduire la conservatisme de conception des commandes robustes existantes. (3) Développement de techniques de commande prédictive pour les systèmes avec retard linéaires et non-linéaires. (4) Preuve rigoureuse de la stabilité asymptotique des commandes prédictives proposées. (5) Application du schéma d'estimation en ligne aux commandes prédictives proposées.
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Valldor-Blücher, Johan. "Upgrading the Control and Monitoring system for the TOFOR neutron time-of-flight spectrometer at JET". Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-197586.
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This report describes the development and testing of the upgraded Control and Monitoring (C&Mu) system for the TOFOR neutron spectrometer. TOFOR is currently performing plasma diagnostics for the JET experimental fusion reactor. The purpose of the C&Mu system is to enable monitoring of the amplitude dependent time delays of TOFOR. In order to perform this monitoring function the C&Mu system must comprise a pulsed light source with variable intensity and a reference time signal. In this work a reference time signal has been retrieved from a laser comprising a motorized polarizer. This has been accomplished by installing a photomultiplier tube and a beamsplitter cube. The beamsplitter cube splits the laser light into two parts and directs one part into the photomultiplier tube. The photomultiplier tube converts the light into an electrical reference time signal. A control program has been developed for the motorized polarizer, enabling the user to vary the intensity of the light over the interval from 0% to 100%. The C&Mu system has been performance tested and it was found that the time resolution of the system is about 0.1ns and the time stability of the system is about 0.12ns over 27 hours. The system is more than adequate to monitor variations in time delays at TOFOR of several nanoseconds, over a full JET day. The C&Mu system is ready to be installed on TOFOR.
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Bergström, David y Jacob Heyle. "Förhindra förseningar i distributionscentraler : Med syfte att öka leveransprecision". Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Industriell organisation och produktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-37813.
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Abstract Purpose – The purpose of the study is to investigate how distribution centers can prevent delays to achieve higher on-time delivery. To fulfill the purpose of the study three study questions have been conducted: • What factors causes delays in distribution centers? • Why do delays occur in distribution centers? • How can distribution centers prevent delays to achieve higher on-time delivery? Method – A qualitative approach has been used throughout the study to enable fulfilment of the study´s purpose. The study has implemented a case study at a distribution center to investigate what factors causes delays. A theoretical framework that attends the research areas of on-time delivery, distribution centers function, operational problems and classification of factors was used to conduct suggestions addressing how businesses can prevent delays. Findings – The study emphasizes that all delays that effect on-time delivery could be classified as individual- or system dependent. The study suggests that businesses should focus on preventing delays classified as system dependent, since they may also prevent individual dependent delays. By improving education and prioritize development of education and standards businesses should be able to improve their on-time delivery. Implications – The study maps factors that causes delays in distribution centers. Categorization and classification could be used to identify where factors occur and explain their dependencies. This study focuses on how on-time delivery is affected by distribution centers performance. The study indicates the possibility to applicate already presented theories in this context but also that categorization and classification of factors is possible. Furthermore, the study has identified problems due to non-used standards, even though they are available for the user. Limitations – The delimitations of the study mark the study’s focus to stocked goods in distribution centers and do not attend economic aspects of on-time delivery. Key words: On-time delivery, distribution centers, delays, individual dependent, system dependentSammanfattning Syfte – Syftet med studien är att undersöka hur distributionscentraler kan förhindra förseningar för att uppnå högre leveransprecision. För att uppfylla syftet har tre frågeställningar utformats: • Vilka faktorer orsakar förseningar i distributionscentraler? • Varför uppstår förseningar i distributionscentraler? • Hur kan distributionscentraler förhindra förseningar för att uppnå högre leverans-precision? Metod – För att uppnå syftet har studien använt en kvalitativ ansats där en fallstudie har genomförts på en distributionscentral i syfte att undersöka vilka faktorer som kan orsaka förseningar. Ett teoretiskt ramverk som behandlar leveransprecision, distributionscentralers funktion, verksamhetsproblem och klassificering av faktorer har använts för att ta fram förslag på hur distributionscentraler kan förhindra faktorer som orsakar förseningar. Resultat – Studien indikerar att alla identifierade faktorer som orsakar förseningar och därmed påverkar leveransprecision kan vara antingen individ- eller systemberoende. Studien föreslår att verksamheter bör fokusera på att förhindra systemberoende faktorer som orsakar förseningar eftersom de även kan förhindra individberoende förseningar. Studien föreslår; genom att förbättra utbildning samt prioritera utveckling av utbildning och standarder skulle verksamheters leveransprecision kunna öka. Implikationer – Det har kartlagts faktorer som kan orsaka förseningar i distributions-centraler. Kategoriseringen tillsammans med klassificering kan användas för att identifiera var faktorer uppstår och vad de beror på. Kategoriseringen tillsammans med klassificering kan användas för att identifiera var faktorer uppstår och vad de beror på. Vidare identifierar studien problem på grund av att standarder inte används, trots att de finns tillgängliga för användare. Begränsningar – Studien är avgränsad till att endast studera produkter som lagerförs i distributionscentraler och tar inte hänsyn till ekonomiska aspekter kopplat till leverans-precision. Nyckelord: Leveransprecision, distributionscentraler, förseningar, individberoende, systemberoende.
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Maiolini, Jacopo. "On delay compensation control for systems with distributed input delay". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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Questa tesi riguarda lo sviluppo di una nuova tecnica di controllo chiamata Delay Compensation per sistemi scalari che presentano un ritardo distribuito nei canali di ingresso. Lo scopo principale è di compensare realmente il lag intrinseco del sistema per un dato instante T_0. Esistono, infatti, alcune tecniche già utilizzate in questo ambito, chiamate predictor-like, che assegnano uno spettro stabile in closed-loop solamente dopo che il sistema è stato soggetto a tutto il ritardo presente in ingresso, non riuscendo perciò a compensarlo esattamente. L'obbiettivo secondario è dovuto a delle approssimazioni scaturite dall'implementazione in controllori real-time di questi controlli. Tutte le tecniche di cui sopra, inclusa Delay Compensation, necessitano infatti di un controllo anch'esso distribuito. Quando ci si scontra con la realtà, l'integrale di controllo deve essere approssimato tramite un integrazione numerica. Negli anni questa non idealità è stata ampiamente studiata, in particolar modo per il controllo Finite Spectrum Assignment (FSA) che verrà, nel caso di ritardi distribuiti di ingresso, relazionato con la tecnica Delay Compensation qui introdotta. Differenti metodi di quadratura verranno utilizzati e confrontati, per l'approssimazione dell'integrale di controllo, effettuando un analisi sia nel dominio del tempo sia nel dominio delle frequenze. Verrà poi effettuata un'estensione della tecnica nel caso di sistemi vettoriali, con dimostrazione annessa della validità nell'utilizzo del controllo Delay Compensation in questo frangente. Anche se non è presente una dimostrazione rigorosa dell'applicabilità del controllo Delay Compensation anche nel caso di un sistema Multi-Input, nella tesi sono presenti alcuni risultati considerando una semplificazione nel sistema controllato. La tesi si conclude elencando gli aspetti positivi e negativi derivanti dall'applicazione della tecnica Delay Compensation qui presentata e da un'indicazione di futuri sviluppi.
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Zhang, Liqian. "Optimal H2 model reduction for dynamic systems /". Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21841548.
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Seuret, Alexandre, Dimos V. Dimarogonas y Karl Henrik Johansson. "Consensus under communication delays". KTH, Reglerteknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-28520.
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This paper deals with the consensus problem under communication network inducing delays. It is well-known that introducing a delay leads in general to a reduction of the performance or to instability due to the fact that timedelay systems are infinite dimensional. For instance, the set of initial conditions of a time-delay system is not a vector but a function taken in an interval. Therefore, investigating the effect of time-delays in the consensus problem is an important issue. In the present paper, we assume that each agent receives instantaneously its own state information but receives the state information from its neighbors after a constant delay. Two stability criteria are provided based on the frequency approach and on Lyapunov-Krasovskii techniques given in terms of LMI. An analytic expression of the consensus equilibrium which depends on the delay and on the initial conditions taken in an interval is derived. The efficiency of the method is tested for different network communication schemes.QC 20110120
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Stoica, Lorelei I. "Gene Therapy for Amyotrophic Lateral Sclerosis: An AAV Delivered Artifical MicroRNA Against Human SOD1 Increases Survival and Delays Disease Progression of the SOD1G93A Mouse Model: A Dissertation". eScholarship@UMMS, 2015. http://escholarship.umassmed.edu/gsbs_diss/813.
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Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by loss of motor neurons, resulting in progressive muscle weakness, atrophy, paralysis and death within five years of diagnosis. About ten percent of cases are inherited, of which twenty percent are due to mutations in the superoxide dismutase 1 (SOD1) gene. Since the only FDA approved ALS drug prolongs survival by just a few months, new therapies for this disease are needed. Experiments in transgenic ALS mouse models have shown that decreasing levels of mutant SOD1 protein alters and in some cases entirely prevents disease progression. We explored this potential therapeutic approach by using a single stranded AAV9 vector encoding an artificial microRNA against human SOD1 injected bilaterally into the cerebral lateral ventricles of neonatal SOD1G93A mice. This therapy extended median survival from 135 to 206 days (a 50% increase) and delayed hind limb paralysis. Animals remained ambulatory until endpoint, as defined by a sharp drop in body weight. Treated animals had a reduction of mutant human SOD1 mRNA levels in upper and lower motor neurons. As compared to untreated SOD1G93A mice, the AAV9 treated mice also had significant improvements in multiple parameters including the number of motor neurons, diameter of ventral root axons, and degree of neuroinflammation in the spinal cord. These studies clearly show that an AAV9-delivered artificial microRNA is a translatable therapeutic approach for ALS.
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Perennes, Cédric. "Energy dependent time delays in blazar light curves : a first look at the modeling of source-intrinsic effect in the MeV-TeV range and constraints on Lorentz Invariance Violation with H.E.S.S". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS183/document.
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Des modèles spécifiques de gravitation quantique suggèrent l’existence d’une Violation de l’Invariance de Lorentz (LIV en anglais) à l’échelle de Planck. Une des signatures de cette violation est la modification de la propagation des photons dans le vide, induisant des décalages temporels dépendant de l’énergie des photons observés sur Terre. De tels décalages dans le temps d’arrivée de rayons γ sont recherchés avec l’expérience H.E.S.S. (High Energy Stereoscopic System), grâce aux émissions de très hautes énergies en provenance de sources lointaines telles que les blazars. Néanmoins, l’origine du décalage temporel doit être comprise en détails. En effet, un décalage intrinsèque à la source pourrait venir biaiser les contraintes sur les modèles de gravitation quantique. Cette thèse propose dans un premier temps de s’intéresser à la modélisation temporelle des éruptions de blazars, pour étudier les possibles décalages intrinsèques liés aux processus d’émissions de ces éruptions. Grâce à l’élaboration d’un modèle simple, cette étude met en relief les différentes caractéristiques de ces décalages intrinsèques sur les scénarios d’éruptions de blazar afin d’essayer de les distinguer des décalages potentiellement dus à un effet de LIV et aussi de proposer de nouvelles contraintes basées sur ces décalages temporels. Dans un deuxième temps, la méthode de recherche de décalages temporels dépendant de l’énergie avec H.E.S.S. est présentée ainsi qu’une application sur l’éruption du blazar Markarian 501 ayant eu lieu en juillet 2014. Cette analyse a permis d’établir la meilleure limite obtenue sur le terme quadratique de la signature de la LIV avec l’utilisation d’éruption de blazarsSpecific models of quantum gravity suggest the existence of a Lorentz Invariance Violation (LIV) at the Planck scale. One signature of that violation is a modification the propagation of photons in vacuum which induces energy dependent delays in the arrival time of photons on Earth. The H.E.S.S. (High Energy Stereoscopic System) experiment can search for such delays in the arrival time of gamma rays, thanks to the very high energy emission coming from distant blazars. However, the time delay origin have to be fully understood. Indeed, an intrinsic time delay coming from the source can bias the constraints made on quantum gravity models. In the first part of this thesis, a time dependent blazar flare model is considered to search for the presence of intrinsic time delays related to the emission mechanisms of flares. With the elaboration of a simple scenario, this study highlights the different characteristics of intrinsic time delays in order to investigate how to disentangle them from delays due to LIV as well as to provide new constraints on blazar modeling. In the second part of this thesis, the method used to search for LIV signatures in blazar light curves at very high energy is presented as well as an application to the flare of Markarian 501 which occurred in July 2014. This analysis provides in particular the best upper limit on the quadratic term of LIV signature
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Wang, Jian. "From local to global: Complex behavior of spatiotemporal systems with fluctuating delay times: From local to global: Complex behavior of spatiotemporal systemswith fluctuating delay times". Doctoral thesis, Universitätsverlag der Technischen Universität Chemnitz, 2013. https://monarch.qucosa.de/id/qucosa%3A20006.
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The aim of this thesis is to investigate the dynamical behaviors of spatially extended systems with fluctuating time delays. In recent years, the study of spatially extended systems and systems with fluctuating delays has experienced a fast growth. In ubiquitous natural and laboratory situations, understanding the action of time-delayed signals is a crucial for understanding the dynamical behavior of these systems. Frequently, the length of the delay is found to change with time. Spatially extended systems are widely studied in many fields, such as chemistry, ecology, and biology. Self-organization, turbulence, and related nonlinear dynamic phenomena in spatially extended systems have developed into one of the most exciting topics in modern science. The first part of this thesis considers the discrete system. Diffusively coupled map lattices with a fluctuating delay are used in the study. The uncoupled local dynamics of the considered system are represented by the delayed logistic map. In particular, the influences of diffusive coupling and fluctuating delay are studied. To observe and understand the influences, the results for the considered system are compared with coupled map lattices without delay and with a constant delay as well as with the uncoupled logistic map with fluctuating delays. Identifying different patterns, determining the existence of traveling wave solutions, and specifying the fully synchronized stable state are the focus of this part of the study. The Lyapunov exponent, the master stability function, spectrum analysis, and the structure factor are used to characterize the different states and the transitions between them. The second part examines the continuous system. The delay is introduced into the reactionterm of the Fisher-KPP equation. The focus of this part of study is the time-delay-induced Turing instability in one-component reaction-diffusion systems. Turing instability has previously only been found in multiple-component reaction-diffusion systems. However, this work demonstrates with the help of the stability exponent that fluctuating delay can result in Turing instability in one-component reaction-diffusion systems as well.Ziel der vorliegenden Arbeit ist die Untersuchung der Einflüsse der zeitlich fluktuierenden Verzögerungen in räumlich ausgedehnten diffusiven Systemen. Durch den Vergleich von Systemen mit konstanter Verzögerung bzw. Systemen ohne räumliche Kopplung erhält man ein tieferes Verständnis und eine bessere Beschreibungsweise der Dynamik des räumlich ausgedehnten diffusiven Systems mit fluktuierenden Verzögerungen. Im ersten Teil werden diskrete Systeme in Form von diffusiven Coupled Map Lattices untersucht. Als die lokale iterierte Abbildung des betrachteten Systems wird die logistische Abbildung mit Verzögerung gewählt. In diesem Teil liegt der Fokus auf Musterbildung, Existenz von Multiattraktoren und laufenden Wellen sowie der Möglichkeit der vollen Synchronisation. Masterstabilitätsfunktion, Lyapunov Exponent und Spektrumsanalyse werden benutzt, um das dynamische Verhalten zu verstehen. Im zweiten Teil betrachten wir kontinuierliche Systeme. Hier wird die Fisher-KPP Gleichung mit Verzögerungen im Reaktionsteil untersucht. In diesem Teil liegt der Fokus auf der Existenz der Turing Instabilität. Mit Hilfe von analytischen und numerischen Berechnungen wird gezeigt, dass bei fluktuierenden Verzögerungen eine Turing Instabilität auch in 1-Komponenten-Reaktions-Diffusionsgleichungen gefunden werden kann
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Wang, Jian. "From local to global: Complex behavior of spatiotemporal systems with fluctuating delay times". Doctoral thesis, Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-133734.
Texto completoResumen
The aim of this thesis is to investigate the dynamical behaviors of spatially extended systems with fluctuating time delays. In recent years, the study of spatially extended systems and systems with fluctuating delays has experienced a fast growth. In ubiquitous natural and laboratory situations, understanding the action of time-delayed signals is a crucial for understanding the dynamical behavior of these systems. Frequently, the length of the delay is found to change with time. Spatially extended systems are widely studied in many fields, such as chemistry, ecology, and biology. Self-organization, turbulence, and related nonlinear dynamic phenomena in spatially extended systems have developed into one of the most exciting topics in modern science. The first part of this thesis considers the discrete system. Diffusively coupled map lattices with a fluctuating delay are used in the study. The uncoupled local dynamics of the considered system are represented by the delayed logistic map. In particular, the influences of diffusive coupling and fluctuating delay are studied. To observe and understand the influences, the results for the considered system are compared with coupled map lattices without delay and with a constant delay as well as with the uncoupled logistic map with fluctuating delays. Identifying different patterns, determining the existence of traveling wave solutions, and specifying the fully synchronized stable state are the focus of this part of the study. The Lyapunov exponent, the master stability function, spectrum analysis, and the structure factor are used to characterize the different states and the transitions between them. The second part examines the continuous system. The delay is introduced into the reactionterm of the Fisher-KPP equation. The focus of this part of study is the time-delay-induced Turing instability in one-component reaction-diffusion systems. Turing instability has previously only been found in multiple-component reaction-diffusion systems. However, this work demonstrates with the help of the stability exponent that fluctuating delay can result in Turing instability in one-component reaction-diffusion systems as wellZiel der vorliegenden Arbeit ist die Untersuchung der Einflüsse der zeitlich fluktuierenden Verzögerungen in räumlich ausgedehnten diffusiven Systemen. Durch den Vergleich von Systemen mit konstanter Verzögerung bzw. Systemen ohne räumliche Kopplung erhält man ein tieferes Verständnis und eine bessere Beschreibungsweise der Dynamik des räumlich ausgedehnten diffusiven Systems mit fluktuierenden Verzögerungen. Im ersten Teil werden diskrete Systeme in Form von diffusiven Coupled Map Lattices untersucht. Als die lokale iterierte Abbildung des betrachteten Systems wird die logistische Abbildung mit Verzögerung gewählt. In diesem Teil liegt der Fokus auf Musterbildung, Existenz von Multiattraktoren und laufenden Wellen sowie der Möglichkeit der vollen Synchronisation. Masterstabilitätsfunktion, Lyapunov Exponent und Spektrumsanalyse werden benutzt, um das dynamische Verhalten zu verstehen. Im zweiten Teil betrachten wir kontinuierliche Systeme. Hier wird die Fisher-KPP Gleichung mit Verzögerungen im Reaktionsteil untersucht. In diesem Teil liegt der Fokus auf der Existenz der Turing Instabilität. Mit Hilfe von analytischen und numerischen Berechnungen wird gezeigt, dass bei fluktuierenden Verzögerungen eine Turing Instabilität auch in 1-Komponenten-Reaktions-Diffusionsgleichungen gefunden werden kann
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張立茜 y Liqian Zhang. "Optimal H2 model reduction for dynamic systems". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31241372.
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Zhong, Qingchang. "Robust control of systems with delays". Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405412.
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Pietarila, Kristel M. Fales Roger. "Developing and automating time delay system stability analysis of dynamic systems using the Matrix Lambert W (MLW) function method". Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6180.
Texto completoResumen
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 16, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Roger Fales. Vita. Includes bibliographical references.