Dissertations / Theses on the topic 'Delayed electrons'
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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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Jacobi, Christoph, Norbert Jakowski, Gerhard Schmidtke, and Thomas N. Woods. "Delayed response of the global total electron content to solar EUV variations." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212283.
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The ionospheric response to solar extreme ultraviolet (EUV) variability during 2011–2014 is shown by simple proxies based on Solar Dynamics Observatory/Extreme Ultraviolet Variability Experiment solar EUV spectra. The daily proxies are compared with global mean total electron content (TEC) computed from global TEC maps derived from Global Navigation Satellite System dual frequency measurements. They describe about 74% of the intra-seasonal TEC variability. At time scales of the solar rotation up to about 40 days there is a time lag between EUV and TEC variability of about one day, with a tendency to increase for longer time scales.
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Jamal, Alden Mohammed Kais. "Robust and Resilient Control for Time Delayed Power Systems." Thesis, Southern Illinois University at Edwardsville, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1588452.
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Power system is the backbone of modern society. Traditionally, over 90% of the electrical energy is produced by power generation systems driven by steam turbines. Recently, with the development of renewable energy resources, wind energy conversion systems are the proven solutions for the next generation sustainable energy resources. Stability and performance of these power systems are the primary concerns of power system engineers. To better characterize the dynamical behaviors of power systems in practical applications, time delays in the feedback state variables, systems modeling uncertainties, and external disturbances are included in the state space model of the power system in this work. Linear matrix inequality based robust and resilient controllers satisfying the H_infinty performance objective for time delayed power systems are proposed. Fixed time delays are assumed to exist within the system state and input signals. The system model is assumed to have unstructured bounded uncertainties and L_2 type of disturbances. Furthermore, controller gain perturbations are assumed to be of additive type. The proposed control techniques have been applied to variable speed permanent magnet synchronous generator based wind energy conversion systems, and electrical power generation systems driven by steam turbine. Computer simulations conducted in MATLAB show the eectiveness of the proposed control algorithms.
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Saloga, Clinton W. "Have delayed independence and poor initial institutions been economically costly for Latin Americans?" Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/3971.
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This paper tests the hypothesis that the timing of independence in Latin
America and the institutions in place at the time of independence had a joint effect
on the developmental paths of the countries. A new variable is presented - the
interaction term between the timing of independence and initial institutions, and
then tested with Multiple OLS Regressions. The findings support the notion that
earlier independence in conjunction with better initial institutions may have had a
positive influence on long-term economic growth in Latin American countries
using data from 1990-2004.Thesis (M.A.)--Wichita State University, The W. Frank Barton School of Business, Dept. of Economics
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Lefever, Timothy W. "Effects of olanzapine on olfactory delayed matching-to-sample in rats." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-3/lefevert/timothylefever.pdf.
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Laichi, Farouk. "Performance study of the leaky least mean square adaptive algorithm with delayed adjustments." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6748.
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Adaptive filters constitute an important part of signal processing. They are widely used in many applications where signal statistics are unknown to the users. One of the most popular adaptive methods is known as the least mean-squared (LMS) algorithm. It is well known for its hardware simplicity and its cost effectiveness. However, the LMS adaptive algorithm does not operate well in non-ideal environments. Leakage in the updated equation of the LMS algorithm was proven to overcome many such problems. This algorithm is known as the leaky LMS (LLMS). The LLMS is very robust to drifting phenomena and overflow in registers; problems that occur in the digital implementation of adaptive algorithms. In many applications, an inherent delay in the feedback error path is encountered. This delay has a definite effect on the performance of the LLMS algorithm. In this thesis, we study the performance of LLMS in the presence of delay (LDLMS). This algorithm is basically the LLMS with a delay incorporated in the coefficient updated equation. A new general stability bound is derived for the LDLMS, from which bounds of convergence of LMS, LLMS, and delayed LMS(DLMS) can be obtained. Stability bounds, convergence behavior, and excess mean squared error for this new algorithm are investigated. Theoretical results are first derived and later verified by simulations. It will be shown that introducing leakage in the DLMS algorithm gives a compromise performance. Finally, examples of applications of the LDLMS algorithm are provided.
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Wang, Xuan. "Pedestrian delays at signalized intersections." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3387827.
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Jacobi, Christoph, Claudia Unglaub, Gerhard Schmidtke, Robert Schäfer, and Norbert Jakowski. "Delayed response of global ionospheric electron content to EUV variations derived from combined SolACES-SDO/EVE measurements." Universität Leipzig, 2015. https://ul.qucosa.de/id/qucosa%3A16645.
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The ionospheric response to solar EUV variability during 2011 - 2014 is shown by an EUV proxy based on primary ionization calculations using combined solar spectra from SDO/EVE and SolACES on board the ISS. The daily proxies are compared with global mean TEC analyses. At time scales of the solar rotation and longer, there is a time lag between EUV and TEC variability of about one to two days, indicating dynamical processes in the thermosphere/ionosphere systems. This lag is not seen at shorter time scales. When taking this delay into account the TEC variance at the seasonal and short-term time scale explained by EUV variations increases from 71% to 76%.Die ionosphärische Antwort auf Variationen des solaren EUV im Zeitraum 2011-2014 wird anhand eines Proxys dargestellt, welcher die primäre Ionisation auf der Basis gemessener solare EUV-Spektren beinhaltet. Die täglichen Werte werden mit Analysen des global gemittelten Gesamtelektronengehalts verglichen. Auf Zeitskalen der solaren Rotation und länger findet sich eine Zeitverzögerung zwischen der EUV-Variation und des derjenigen des Gesamtelektronengehalts von ein bis 2 Tagen, welche auf dynamische Prozesse im System Thermosphäre/Ionosphäre hinweist. Die Verzögerung ist auf kurzen Zeitskalen nicht zu sehen. Wenn diese Verzögerung berücksichtigt wird, erhöht sich die durch EUV-Variationen erklärte Varianz des Elektronengehalts von 71% auf 76%.
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Haule, Damian Daniel. "Virtuality and reality of a near-optimal time-delayed teleoperator control system based on teleprogramming paradigm." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42052.
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The teleprogramming control paradigm is suggested as a means to efficiently perform teleoperation tasks in situations where the remote and local manipulator systems are connected via a low bandwidth delayed communications link. The effects of communication delays in the order of seconds can be reduced by building a virtual reality simulated model of the remote site with which the operator can interact to receive immediate quality feedback using a Human-Machine Interface (HMI) for telepresence applications. This concept overcomes the delay by transmitting not Cartesian or joint level informations in the form of signals, but rather symbolic, error tolerant, command program segments to the remote site. Symbolic instructions are send to the remote station every time the contact state changes or every second if no change of contact state has occurred.Remote robotic systems are often very complex and difficult to operate, especially as multiple robots are integrated to accomplish difficult tasks in an unstructured or hazardous environments. In addition, training the operators is time-consuming and costly. A simulated virtual reality based system will provide a means by which operators can be trained to operate in an intuitive, and cost-effective way. Operator interaction with the remote system is at a high, task-oriented, level. Real-time state monitoring can prevent illegal robot actions and provides interactive feedback. A teleprogramming based simulator is essential for cost-effective Teleoperator Interface & Training (TIT) using supervisory control approach. An intelligent virtual interface is required which provides a rich means of presenting diagnostic and visual state information to the operator with reduced fatigue in real-time.
The Mobile Servicing System (MSS) Operations and Training Simulator (MOTS) will be used as a leading edge implementation of the teleprogramming concepts. MOTS provides high-fidelity, functional kinematic and dynamic software simulation of the MSS Space Segment in on-orbit configuration. MOTS is a real-time simulation environment of varying degrees of fidelity, along with an aggregate of software tools intended for the support of MSS space operations and training of crew and ground personnel. Primary interface to MOTS simulation models is through a Common Data Base (CDB) where telecommands are stored in a common shared memory. Hence, all telecommand data elements that are used to control the simulation modules are exported through the CDB by the Human Computer Interface (HCI) pages, hand controllers (H/C) and Display & Control (D&C) panel. Communication between simulation modules is achieved through the CDB in real-time.
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Bullard, Laura A. "The effects of the NMDA antagonist dizocilpine on an olfactory delayed match-to-sample task in rats." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-1/bullardl/laurabullard.pdf.
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Liu, Xuan. "Efficient delay-tolerant particle filtering." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95173.
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Tracking is frequently performed using multiple sensor platforms, with measurements being relayed to a fusion centre over a wireless network. This can lead to some measurements being delayed when adverse environmental conditions cause packet losses to occur. These delayed measurements are called out-of-sequence measurements (OOSMs). Simply discarding the delayed OOSMs can waste important information and lead to much poorer tracking performance. This thesis proposes a novel algorithm for delay-tolerant particle filtering that is computationally efficient and has limited memory requirements. The algorithm estimates the informativeness of the OOSMs and immediately discards uninformative measurements. More informative measurements are then processed using the storage efficient particle filter, which is relatively computationally simple. If the measurement induces a dramatic change in the current filtering distribution, the particle filter is re-run to increase the accuracy. From our simulation results, we observe that our novel algorithm only processes a relatively small portion of the OOSMs, but it performs almost as well as much more computationally-complex techniques that have larger storage requirements.Le suivi est souvent effectué à l'aide de plates-formes composées de multiples capteurs où les mesures sont retransmises à un centre de fusion via un réseau sans fil. Lorsque des conditions environnementales défavorables entraînent des pertes de paquets, la transmission de ces mesures peut être retardée. Ces dernières sont appelées mesures déclassées (OOSM). Jeter ces OOSMs peut gaspiller des informations importantes et peut affecter négativement la performance de l'algorithme de suivi. Cette thèse propose un nouvel algorithme de filtrage de particules tolérantes au délai (delay-tolerant) qui n'est pas gourmand ni en temps de calcul, ni en mémoire. L'algorithme estime la quantité d'information des OOSMs et rejette immédiatement les mesures inutiles. Les mesures contenant suffisamment d'information sont ensuite traitées à l'aide au filtre à particules. Si la mesure induit un changement radical dans la distribution de filtrage actuelle, le filtre à particules est ré exécuter pour augmenter la précision. Nos résultats de simulation indiquent que notre nouvel algorithme ne traite qu'une petite fraction des OOSMs, mais il performe presque aussi bien que de nombreuses techniques qui requièrent des calculs plus complexes et qui ont de plus importants besoins de stockage.
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Williams, Scott Lawrence. "Separation of mixed radiometric land cover temperatures in time-delayed bi-angular views using estimated fractional differential coefficients." Thesis, New Mexico State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3582404.
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A dissertation is presented concerning the separation of radiometric temperatures of sparse land covers from two views of mixed thermal and NDVI samples with a time delay between the views. The research scope is limited to a simple binary land cover of vegetation canopy and bare soil. Previous methods have been developed using simultaneous views but little work has been done on time-delayed sampling, which is the focus of this study.
The dissertation hypothesis is based on the observation that the rate of change of a mixed radiometric temperature with respect to actual fractional vegetation cover, dTm/dfa originally constructed using spatially varying vegetation covers, can also be constructed using bi-angular views of the same land parcel but with a different interpretation; that bi-angular samples provide a perceived fractional cover differential, dTm/df0 . The hypothesis is that dTm/df0 can be used for sub-pixel temperature discrimination of binary land covers and, moreover, that the separate soil and vegetation total differential coefficients dTm/df0 and dTv/df0, required in the algebraic system, can be characterized to sufficiently capture environmental influences between samples in time. To test the hypothesis, this study heuristically derives a first-order estimation of the differential coefficients, required to decompose land cover temperatures from mixed data points, for any time-delayed sampling spanning the day. Applying the estimated values on similar target days gives a high success rate for a local time span of at least a week.
This approach, once scaled up, could be used by platforms with inherent time delays, such as tandem weather satellites, to provide separate land cover temperature estimates from low-resolution sensors.
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Wang, Yujun 1968 March 4. "Delay modeling of CMOS transistor chains." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33999.
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Due to the continual development of the CMOS IC technology, there is a corresponding strong demand for faster and more accurate methods to compute the delay, which is a critical parameter in CAD tools for timing analysis. Several delay models have been developed for the basic CMOS inverter circuit. These models have also been used in some approaches to the analysis of delay in general CMOS gates. This involves the reduction of the gate to an equivalent inverter. Most gates consist of series and/or parallel combinations of MOSFET transistors. The greatest challenge in the reduction process is presented by the series-connected MOSFET structure (SCMS). In this thesis we examine existing techniques for reducing a SCMS and its input signals to an equivalent transistor with its equivalent input signal. In the process we propose some significant simplifications and improvements to these techniques.We examine, in particular, the SCMS reduction techniques presented in [5] and [6], both of which use a two-step process consisting of (i) mapping the input signals to a single equivalent one and, (ii) mapping the SCMS transistors to a single MOSFET. The authors of [6] claim that their model is superior to the simpler one used in [5]. Our analysis, based on a 0.35 micron technology, shows that the same accuracy claimed in [6] can be achieved by replacing their Step (ii) by a much simpler one based on the more empirical implementation used on [5]. We also show that the weighting coefficients used by [6] in Step (i) to compute the equivalent input signal, are functions of the input signal transition time, unlike the claim made in [6] that they are constant. We also conclude that, in the final analysis, the accuracy of our modified model as well as the one in [6] is limited by the empirical formula used to determine the equivalent input transition time.
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Ma, Min. "RC delay metrics for interconnect optimization." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81554.
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The main challenge for developing accurate and efficient delay metrics has been the prediction of delay to points on the interconnect which are relatively close to the source. Those metrics which are relatively successful in meeting this challenge require two-dimensional look-up tables and algorithm tuning, and are quite challenging to implement. The simpler explicit metrics only work well on so-called far nodes, which are characterized by all-pole frequency responses.In this thesis, we first review an existing delay metric for wires and then try to extend it to arbitrary tree networks. Thorough tests demonstrate it to be accurate and efficient for wires only. We then present an explicit delay metric for dealing with near nodes in RC interconnect, which is based on the first three moments of the impulse response. An accurate model for the delay to the internal node of a two-pole one-zero RC circuit serves as the core of the new metric. Since no simplifying assumption is made in the model, it returns excellent accuracy at the internal node in any two-node RC circuit, no matter how close the internal node is to the source. The delay at near nodes in arbitrary RC trees is then computed by order reduction to a two-pole system using the first three moments of the impulse response. A significant further improvement in accuracy is achieved by correcting for the skewness of the impulse response. In parallel, a simple explicit metric is introduced for predicting the delay to far nodes, where order reduction is not needed. This is based on the first moment of the node of interest and the second moment of the slowest node. Furthermore a simple criterion is derived for distinguishing near nodes from far nodes. Tests on RC models of wires and trees demonstrate that the combination of these two metrics is accurate within 2% for far nodes and within 5% for near nodes with delays which are as much as an order of magnitude smaller than that of the slowest node.
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Wang, Yi. "Superconducting coplanar delay lines." Thesis, University of Birmingham, 2005. http://etheses.bham.ac.uk//id/eprint/7/.
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Two 25 ns wideband HTS delay lines with a novel double-spiral meander line (DSML) structure are designed, fabricated and measured. One is based on the conventional coplanar waveguide (CPW), and the other based on a conductor-backed coplanar waveguide (CBCPW). Systematic design work is presented in this thesis on the calculations of transmission-line parameters, the selection and optimisation of delay line patterns, and the modelling of the transitions and connections at the input/output. Simulations show that the DSML structure has better transmission efficiency over a wide frequency range than the conventional double-spiral line (DSL). The bandwidth and dispersion of such a meander structure are investigated. The fabricated delay lines are first characterised as resonators with a fundamental mode at ~20 MHz. The surface resistances of the superconductors and the temperature- and power-dependent properties are investigated by measuring the Q-values of more than 1000 harmonics from 20 MHz to 20 GHz. Then, the delay lines are fully connected as they would be used in the application and measured thoroughly in both the frequency and time domain. The performance of the CBCPW delay line is the best ever demonstrated in terms of the widest resonance-free band (2 to 18 GHz), low insertion loss (0.06 dB/ns at 60 K and 10 GHz), small ripple (<1 dB up until 16 GHz), and small dispersion (< 2 ns in the variation of group delay between 2 and 18 GHz). This is the first coplanar delay line successfully demonstrated without using bonding-wires to join the in-plane grounds. The spurious reflecting elements in the DSML structure are identified by the time domain analyses. The results from this measurement are compared comprehensively with those from both resonance measurement and simulations.
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Natsheh, Ammar Nimer. "Analysis, simulation and control of chaotic behaviour and power electronic converters." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/5739.
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The thesis describes theoretical and experimental studies on the chaotic behaviour of a peak current-mode controlled boost converter, a parallel two-module peak current-mode controlled DC-DC boost converter, and a peak current-mode controlled power factor correction (PFC) boost converter. The research concentrates on converters which do not have voltage control loops, since the main interest is in the intrinsic mechanism of chaotic behaviour. These converters produce sub-harmonics of the clock frequency at certain values of the reference current I[ref] and input voltage V[in], and may behave in a chaotic manner, whereby the frequency spectrum of the inductor becomes continuous. Non-linear maps for each of the converters are derived using discrete time modelling and numerical iteration of the maps produce bifurcation diagrams which indicate the presence of subharmonics and chaotic operation. In order to check the validity of the analysis, MATLAB/SIMULINK models for the converters are developed. A comparison is made between waveforms obtained from experimental converters, with those produced by the MATLAB/SIMULINK models of the converters. The experimental and theoretical results are also compared with the bifurcation points predicted by the bifurcation diagrams. The simulated waveforms show excellent agreement, with both the experimental waveforms and the transitions predicted by the bifurcation diagrams. The thesis presents the first application of a delayed feedback control scheme for eliminating chaotic behaviour in both the DC-DC boost converter and the PFC boost converter. Experimental results and FORTRAN simulations show the effectiveness and robustness of the scheme. FORTRAN simulations are found to be in close agreement with experimental results and the bifurcation diagrams. A theoretical comparison is made between the above converters controlled using delayed feedback control and the popular slope compensation method. It is shown that delayed feedback control is a simpler scheme and has a better performance than that for slope compensation.
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Devetak, Fabrizio U. "Minimizing maximum path delay in multipath connections." Thesis, Illinois Institute of Technology, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3575344.
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Minimizing packet delay (or packet latency, as it is often called) is an important goal in modern telecommunication networks. In a network with given physical and topological characteristics, uneven distribution of traffic between nodes may result in parts of the network being underutilized while other parts may experience congestion and its related effect of higher delays, and even packet loss if buffers become overloaded. Overload results in longer queuing delays, which are a major, if not the major, source of packet delay. Internet nodes typically route based on a single best (shortest) path without taking into account link occupancy and without taking full advantage of all available network resources. So a method for improving network performance is to allow nodes to use multiple paths to route packets to a given destination. In this research project the main objective is to find the best algorithm that, applied to a multicommodity network, produces multipath flow assignments that minimize the maximum cross-network delay. The motivation for this objective is the tighter requirements for quality of service coming from real-time streaming services, such as voice and video, that restrict the maximum source-destination packet delay. An analytical approach based on Lagrange Multipliers was used, leading to an iterative algorithm that can be proved to converge to the optimal path and flow configuration. From that algorithm a simplified heuristic algorithm was derived that achieves results close to optimal. Another heuristic, but more intuitive, algorithm was also investigated and was found to also offer good results and to be computationally efficient. The two heuristic algorithms were simulated using Java programs and. as a benchmark, the single path algorithm that is commonly used in the Internet was also simulated in Java. Performance comparisons for the three types of simulations are also provided. For a more realistic evaluation, the intuitive heuristic algorithm was also simulated in the NS-3 simulation environment, an industry standard widely used in the academic world. For the NS-3 simulation a distributed routing protocol that implements the maximum delay minimization algorithms without centralized control, was designed.
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Nabavi-Lishi, Abdolreza. "Delay and current evaluation in CMOS circuits." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41166.
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An accurate and fast technique has been developed for computing the supply current as well as the delay in CMOS combinational circuits. It is based on a new analytical model of the CMOS inverter which is designed specifically to compute the maximum supply current and the delay without recourse to integration. If the current waveform is needed, integration is used only for the trailing edge. This model can be used not only to compute maximum supply current and delay in CMOS circuits, but also to detect dynamic hazards.The extension to general CMOS circuits is achieved through a collapsing method which reduces each gate to an equivalent inverter. Unlike previous attempts to solve this problem, our technique is not limited to single input transitions or to step inputs. It also takes into account the relative positions of the switching inputs in series-connected transistors.
The improvement in computation speed, for delay and maximum current in large circuits, approaches 4 orders of magnitude compared to HSPICE using the level-3 MOSFET model. For current waveforms the speed improvement approaches 3 orders of magnitude. The accuracy of computing the delay and the supply current is usually within 10% and 12%, respectively. Although the technique has been tested on static CMOS gate circuits, the extension to dynamic circuits is straightforward.
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Parameswaran, Nair Ravi Sankar. "Delay-insensitive ternary logic (DITL)." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/Parameswaran_Nair_09007dcc803bc548.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 27, 2007) Includes bibliographical references (p. 55-56).
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Beşoğul, Ercan Supervisor :. Dikmen Toker İrem. "Reasons of delays in steel construction projects : an application of a delay analysis methodology \h [Electronic resource] / \c Ercan Beşoğul, Supervisor Assoc. Prof. Dr. İrem Dikmen Toker." Ankara : METU, 2006. http://etd.lib.metu.edu.tr/upload/12607159/index.pdf.
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Pant, Pankaj. "Automated diagnosis of path delay faults in digital integrated circuits." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/13556.
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Yu, Bo. "Delay-oriented active queue management in TCP/IP networks." Thesis, Queen Mary, University of London, 2011. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1331.
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Internet-based applications and services are pervading everyday life. Moreover, the growing popularity of real-time, time-critical and mission-critical applications set new challenges to the Internet community. The requirement for reducing response time, and therefore latency control is increasingly emphasized. This thesis seeks to reduce queueing delay through active queue management. While mathematical studies and research simulations reveal that complex trade-off relationships exist among performance indices such as throughput, packet loss ratio and delay, etc., this thesis intends to find an improved active queue management algorithm which emphasizes delay control without trading much on other performance indices such as throughput and packet loss ratio. The thesis observes that in TCP/IP network, packet loss ratio is a major reflection of congestion severity or load. With a properly functioning active queue management algorithm, traffic load will in general push the feedback system to an equilibrium point in terms of packet loss ratio and throughput. On the other hand, queue length is a determinant factor on system delay performance while has only a slight influence on the equilibrium. This observation suggests the possibility of reducing delay while maintaining throughput and packet loss ratio relatively unchanged. The thesis also observes that queue length fluctuation is a reflection of both load changes and natural fluctuation in arriving bit rate. Monitoring queue length fluctuation alone cannot distinguish the difference and identify congestion status; and yet identifying this difference is crucial in finding out situations where average queue size and hence queueing delay can be properly controlled and reasonably reduced. However, many existing active queue management algorithms only monitor queue length, and their control policies are solely based on this measurement. In our studies, our novel finding is that the arriving bit rate distribution of all sources contains information which can be a better indication of congestion status and has a correlation with traffic burstiness. And this thesis develops a simple and scalable way to measure its two most important characteristics, namely the mean ii and the variance of the arriving rate distribution. The measuring mechanism is based on a Zombie List mechanism originally proposed and deployed in Stabilized RED to estimate the number of flows and identify misbehaving flows. This thesis modifies the original zombie list measuring mechanism, makes it capable of measuring additional variables. Based on these additional measurements, this thesis proposes a novel modification to the RED algorithm. It utilizes a robust adaptive mechanism to ensure that the system reaches proper equilibrium operating points in terms of packet loss ratio and queueing delay under various loads. Furthermore, it identifies different congestion status where traffic is less bursty and adapts RED parameters in order to reduce average queue size and hence queueing delay accordingly. Using ns-2 simulation platform, this thesis runs simulations of a single bottleneck link scenario which represents an important and popular application scenario such as home access network or SoHo. Simulation results indicate that there are complex trade-off relationships among throughput, packet loss ratio and delay; and in these relationships delay can be substantially reduced whereas trade-offs on throughput and packet loss ratio are negligible. Simulation results show that our proposed active queue management algorithm can identify circumstances where traffic is less bursty and actively reduce queueing delay with hardly noticeable sacrifice on throughput and packet loss ratio performances. In conclusion, our novel approach enables the application of adaptive techniques to more RED parameters including those affecting queue occupancy and hence queueing delay. The new modification to RED algorithm is a scalable approach and does not introduce additional protocol overhead. In general it brings the benefit of substantially reduced delay at the cost of limited processing overhead and negligible degradation in throughput and packet loss ratio. However, our new algorithm is only tested on responsive flows and a single bottleneck scenario. Its effectiveness on a combination of responsive and non-responsive flows as well as in more complicated network topology scenarios is left for future work.
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Davis, Michael Ryan. "Delay-based computing implementation issues in CMOS and nanotechnologies /." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0004825.
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Abouchakra, Rabih. "Delay estimation for transform domain acoustical echo cancellation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37254.pdf.
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Boudreau, Daniel. "Joint time delay estimation and adaptive filtering techniques." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70177.
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This thesis studies adaptive filters for the case in which the main input signal is not synchronized with the reference signal. The asynchrony is modelled by a time-varying delay. This delay has to be estimated and compensated. This is accomplished by designing and investigating joint delay estimation and adaptive filtering algorithms. First, joint maximum likelihood estimator is derived for input Gaussian signals. It is used to define a readily implementable joint estimator, composed of an adaptive delay element and an adaptive filter. Next, two estimation criteria are investigated with that structure. The minimum mean squared error criterion is used with a joint steepest-descent adaptive algorithm and with a joint least-mean-square adaptive algorithm. The general convergence conditions of the joint steepest-descent algorithm are derived. The joint LMS algorithm is analysed in terms of joint convergence in the mean and in the mean square. Finally, a joint recursive least squares adaptive algorithm is investigated in conjunction with the exponentially weighted least squares criterion. Experimental results are obtained for these different adaptive algorithms, in order to verify the analyses. The results show that the joint algorithms improve the performance of the conventional adaptive filtering techniques.
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Gaiotti, Serge. "Worst-case delay estimation of digital MOS circuits." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60690.
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This thesis presents accurate and efficient transistor-level delay modeling techniques for the worst-case delay estimation of digital MOS circuits. A number of timing analysis tools already rely on transistor-level delay models which use relaxation-based electrical simulation techniques to accurately model the propagation delay of MOS logic gates. For worst-case delay estimation, efficient application of relaxation-based electrical simulation techniques can be performed by using multiple-transition delay modeling methods and by minimizing the number of node equations to be solved. The worst-case delay estimates produced by accurate transistor-level delay models can be inaccurate if logic dependencies within MOS logic gates are ignored. A class of transistor-level delay estimators, which is based on the enumeration of worst-case conduction subnetworks, is introduced to handle these logic dependencies. A comparative study of multiple-transition worst-case delay estimation methods is also presented.
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Menezes, Karol Fidelis 1966. "Signal delay estimates for design of multichip assemblies." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278171.
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Signal delay estimates for high-speed interconnection nets are formulated using analytical methods. The equations are suitable for estimating delay in interconnects of printed wiring boards and multi-chip modules where the resistance of wires is small. Effects of drivers, receivers, chip interfaces and wires on delay are considered by using simple models. The wires are treated as lossless transmission lines with capacitive discontinuities modeling receiver chip interfaces. Drivers are voltage sources with series resistance. Signal delay consists of line propagation delay and delay due to the change in rise time and reflections at the discontinuities. Various commonly used net topologies are identified and wiring rules and delay predictors provided for each of them. It is shown that interconnect delay can be formulated as a non-linear function of the product of the line characteristic impedance and load capacitance. SPICE simulations are sued to validate analytical derivations.
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Wang, Michael Chih-Huei 1967. "Delay timing of Sea-of-Wire Array Logic." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/291633.
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Sea-of-Wire Array Logic has been developed to support a symbolic layout algorithm realization. A delay timing scheme is needed to direct the placement strategy of the layout. Both SPICE simulation and table lookup method are compared to verify the accuracy of delay estimation. Input waveform distortion is taken into account in the timing analysis, and correction factors are applied to increase the accuracy of delay estimation. A table lookup scheme has shown to be very accurate in comparison with SPICE value. A set of benchmark circuits have been applied to evaluate this table lookup scheme. The results obtained demonstrate a greater than 90% accuracy and five orders of magnitude increase in speed over SPICE simulation.
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Phillips, Alan Paul 1957. "Phase estimation as applied to group delay measurements." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/291934.
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This thesis addresses the problem of measuring the group delay of a network with different frequencies at its input and output ports. Three distinct methods of measuring group delay are developed and their performance compared in a Monte Carlo analysis. Also considered is the problem of second order nonlinear distortion and its effect on measuring group delay. A method is developed to identify a specific second order nonlinear structure causing distortion. A nonlinear equalizer is then developed to cancel, or equalize, the undesired second order distortion.
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Cuevas, Tello Juan Carlos. "Estimating time delays between irregularly sampled time series." Thesis, University of Birmingham, 2007. http://etheses.bham.ac.uk//id/eprint/88/.
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The time delay estimation between time series is a real-world problem in gravitational lensing, an area of astrophysics. Lensing is the most direct method of measuring the distribution of matter, which is often dark, and the accurate measurement of time delays set the scale to measure distances over cosmological scales. For our purposes, this means that we have to estimate a time delay between two or more noisy and irregularly sampled time series. Estimations have been made using statistical methods in the astrophysics literature, such as interpolation, dispersion analysis, discrete correlation function, Gaussian processes and Bayesian method, among others. Instead, this thesis proposes a kernel-based approach to estimating the time delay, which is inspired by kernel methods in the context of statistical and machine learning. Moreover, our methodology is evolved to perform model selection, regularisation and time delay estimation globally and simultaneously. Experimental results show that this approach is one of the most accurate methods for gaps (missing data) and distinct noise levels. Results on artificial and real data are shown.
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Veeramachaneni, Siva Rama Krishna. "Robust PID control using a Smith predictor for time delay systems." Diss., Wichita State University, 2013. http://hdl.handle.net/10057/10617.
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Time delays are unavoidable in many mechanical and electrical systems. The presence of delay typically imposes strict limitations on achievable feedback performance in both continuous and discrete systems. The presence of the delay complicates the design and analysis of a control system as it makes continuous systems infinite dimensional, and it significantly increases the dimensions in discrete systems. This work will propose a method to determine all PID controllers that stabilize the closed-loop system and satisfy weighted sensitivity, robust stability or robust performance constraints for stable time delay systems with a Smith predictor using the frequency response of the system. The Smith predictor works to eliminate the time delay from the characteristic equation and so improves the range of PID controllers that stabilize the system. A comparison between the range of PID controllers with and without Smith predictor is given in this work. This work also proposes a method for finding all PI-PD controllers that stabilize an unstable system with a modified version of the Smith predictor.Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science
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Baylon, Fuentes Antonio. "Ring topology of an optical phase delayed nonlinear dynamics for neuromorphic photonic computing." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2047/document.
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Aujourd'hui, la plupart des ordinateurs sont encore basés sur des concepts développés il y a plus de 60 ans par Alan Turing et John von Neumann. Cependant, ces ordinateurs numériques ont déjà commencé à atteindre certaines limites physiques via la technologie de la microélectronique au silicium (dissipation, vitesse, limites d'intégration, consommation d'énergie). Des approches alternatives, plus puissantes, plus efficaces et moins consommatrices d'énergie, constituent depuis plusieurs années un enjeu scientifique majeur. Beaucoup de ces approches s'inspirent naturellement du cerveau humain, dont les principes opérationnels sont encore loin d'être compris. Au début des années 2000, la communauté scientifique s'est aperçue qu'une modification du réseau neuronal récurrent (RNN), plus simple et maintenant appelée Reservoir Computing (RC), est parfois plus efficace pour certaines fonctionnalités, et est un nouveau paradigme de calcul qui s'inspire du cerveau. Sa structure est assez semblable aux concepts classiques de RNN, présentant généralement trois parties: une couche d'entrée pour injecter l'information dans un système dynamique non-linéaire (Write-In), une seconde couche où l'information d'entrée est projetée dans un espace de grande dimension (appelé réservoir dynamique) et une couche de sortie à partir de laquelle les informations traitées sont extraites par une fonction dite de lecture-sortie. Dans l'approche RC, la procédure d'apprentissage est effectuée uniquement dans la couche de sortie, tandis que la couche d'entrée et la couche réservoir sont fixées de manière aléatoire, ce qui constitue l'originalité principale du RC par rapport aux méthodes RNN. Cette fonctionnalité permet d'obtenir plus d'efficacité, de rapidité, de convergence d'apprentissage, et permet une mise en œuvre expérimentale. Cette thèse de doctorat a pour objectifs d'implémenter pour la première fois le RC photoniques en utilisant des dispositifs de télécommunication. Notre mise en œuvre expérimentale est basée sur un système dynamique non linéaire à retard, qui repose sur un oscillateur électro-optique (EO) avec une modulation de phase différentielle. Cet oscillateur EO a été largement étudié dans le contexte de la cryptographie optique du chaos. La dynamique présentée par de tels systèmes est en effet exploitée pour développer des comportements complexes dans un espace de phase à dimension infinie, et des analogies avec la dynamique spatio-temporelle (tels que les réseaux neuronaux) sont également trouvés dans la littérature. De telles particularités des systèmes à retard ont conforté l'idée de remplacer le RNN traditionnel (généralement difficile à concevoir technologiquement) par une architecture à retard d'EO non linéaire. Afin d'évaluer la puissance de calcul de notre approche RC, nous avons mis en œuvre deux tests de reconnaissance de chiffres parlés (tests de classification) à partir d'une base de données standard en intelligence artificielle (TI-46 et AURORA-2), et nous avons obtenu des performances très proches de l'état de l'art tout en établissant un nouvel état de l'art en ce qui concerne la vitesse de classification. Notre approche RC photonique nous a en effet permis de traiter environ 1 million de mots par seconde, améliorant la vitesse de traitement de l'information d'un facteur supérieur à ~3Nowadays most of computers are still based on concepts developed more than 60 years ago by Alan Turing and John von Neumann. However, these digital computers have already begun to reach certain physical limits of their implementation via silicon microelectronics technology (dissipation, speed, integration limits, energy consumption). Alternative approaches, more powerful, more efficient and with less consume of energy, have constituted a major scientific issue for several years. Many of these approaches naturally attempt to get inspiration for the human brain, whose operating principles are still far from being understood. In this line of research, a surprising variation of recurrent neural network (RNN), simpler, and also even sometimes more efficient for features or processing cases, has appeared in the early 2000s, now known as Reservoir Computing (RC), which is currently emerging new brain-inspired computational paradigm. Its structure is quite similar to the classical RNN computing concepts, exhibiting generally three parts: an input layer to inject the information into a nonlinear dynamical system (Write-In), a second layer where the input information is projected in a space of high dimension called dynamical reservoir and an output layer from which the processed information is extracted through a so-called Read-Out function. In RC approach the learning procedure is performed in the output layer only, while the input and reservoir layer are randomly fixed, being the main originality of RC compared to the RNN methods. This feature allows to get more efficiency, rapidity and a learning convergence, as well as to provide an experimental implementation solution. This PhD thesis is dedicated to one of the first photonic RC implementation using telecommunication devices. Our experimental implementation is based on a nonlinear delayed dynamical system, which relies on an electro-optic (EO) oscillator with a differential phase modulation. This EO oscillator was extensively studied in the context of the optical chaos cryptography. Dynamics exhibited by such systems are indeed known to develop complex behaviors in an infinite dimensional phase space, and analogies with space-time dynamics (as neural network ones are a kind of) are also found in the literature. Such peculiarities of delay systems supported the idea of replacing the traditional RNN (usually difficult to design technologically) by a nonlinear EO delay architecture. In order to evaluate the computational power of our RC approach, we implement two spoken digit recognition tests (classification tests) taken from a standard databases in artificial intelligence TI-46 and AURORA-2, obtaining results very close to state-of-the-art performances and establishing state-of-the-art in classification speed. Our photonic RC approach allowed us to process around of 1 million of words per second, improving the information processing speed by a factor ~3
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Hamoui, Anas. "Current, delay, and power analysis of submicron CMOS circuits." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0022/MQ50618.pdf.
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Hafed, Mohamed M. "CMOS inverter current and delay models incorporating interconnect effects." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0025/MQ50614.pdf.
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Farajian, Patrick. "Dynamic input rate control in queues with feedback delay." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26386.
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The signal propagation delays in a high speed, wide area telecommunication network can be orders of magnitude larger than a message transmission time. This implies that the response times associated with dynamic congestion management strategies can be long relative to the characteristic times of the queue-length processes being controlled, and that such strategies may be of limited use in controlling message loss in high speed settings. We examine the interplay between signal propagation delays and efficiency of feedback-based congestion controls in the case of a very simple network model consisting of a single multiplexor serving a remote source population. We establish, using simulations of two simple approaches described in the literature, that loss performance can be very sensitive to propagation delay, and that response times can be diminished, for given propagation delays, by applying a rate-based, or cyclic, service strategy at the multiplexor output line in place or First-In, First-Out. We develop an optimization framework for the control problem, enabling the use of Markov Decision Programming to calculate the form and performance of feedback-based controllers which are optimal in terms of the trade-off achieved between forced losses at the network boundary and congestion-induced losses in the network interior. Observing that performance can be made insensitive to signal propagation delays by means of appropriate buffer dimensioning, we develop an asymptotic analysis of the buffer requirements, applicable in the limit of large values of the delay/bandwidth product.
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Foodeei, Majid. "Low-delay speech coding at 16 kbs and below." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60717.
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Development of network quality speech coders at 16 kb/s and below is an active research area. This thesis focuses on the study of low-delay Code Excited Linear Predictive (CELP) and tree coders. A 16 kb/s stochastic tree coder based on the (M.L.) search algorithm suggested by lyengar and Kabal and a low-delay CELP coder proposed by AT&T (CCITT 16 kb/s standardization candidate) are examined. The first goal is to compare and study the performance of the two coders. Second objective is to analyze the particular characteristics which make the two coders different from one another. The final goal is the improvement of the performance of the coders, particularly with a view of bringing down the bit rate below 16 kb/s.When compared under similar conditions, the two coders showed comparable performance at 16 kb/s. Issues in backward adaptive linear prediction analysis for both near and far sample redundancy removal such as analysis methods, windowing, ill-conditioning, quantization noise effects and computational complexities are studied.
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Kim, Min-Young. "Delay induced instabilities in coupled semiconductor lasers and Mackey-Glass electronic circuits." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2722.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Physics. 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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Kadiyala, Murali Krishna. "Model and analysis of burst packet losses and packet delays in IP networks using Markov chains." Diss., Wichita State University, 2011. http://hdl.handle.net/10057/3930.
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The classic problem of communication networks such as increase in packet delays and
packet losses regains significance with the evolution of a new variety of communication
networks and networking protocols. Packet delays in wired networks like the Internet were very
well analyzed in the past. However, the packet delays in ad hoc networks were not thoroughly
studied, especially, with respect to issues like the effect of medium access control (MAC) layer
delays on the upper layer delays associated with the packet transmission process, the packet
service-time, and packet end-to-end delay. Similarly, the packet losses in wired networks were
analyzed using empirical models based on Markov chains. These models lack the ability to
describe the response of an Internet router for different packet arrival patterns. For the networks
experiencing frequent burst losses, it is very important to analyze the effect of packet interarrival
time on such losses. This calls for a set of well-defined analytical models which can help
in identifying the parameters responsible for the increase in packet delays and packet drops. Such
models also extend to devise new network protocols and mechanisms, and improve the network
throughput. This dissertation addresses the requirement of such models. The first part proposes
an analytical model to describe packet delays in ad hoc networks and highlights the effect of
MAC delays on route discovery time and node's packet service-time. The second part presents a
semi-Markov process based model to analyze the wireless LANs (WLANs) and the MAC
protocols such as the IEEE 802.11 Distributed Coordination Function (DCF) used in the IEEE
WLANs. The third part presents an empirical model to describe the burst losses in Voice over
Internet Protocol (VoIP) caused by queue overflows at the Internet routers. As an extension to
this dissertation, an analytical model describing the combined effect of packet arrival-rate, packet
service-rate, and the queue capacity on burst losses is also presented as future work.Dissertation(Ph.D.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science
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Haurani, Ammar. "Robust control of uncertain time-delay systems." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84257.
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This work addresses the problem of robust stabilization and robust Hinfinity control of uncertain time-delay systems. The time-delays are considered to be present in the states and/or the outputs, and the uncertainties in the system representation are of the parametric norm-bounded type. Both cases of actuators, with and without saturation are studied, and the state-feedback and output-feedback control designs are presented. Two methods for analysis and synthesis of controllers are used: The first is based on the transfer function, and the second on the use of functionals.In the context of the design method based on transfer functions, the problem of Hinfinity output feedback design for a class of uncertain linear continuous-time or discrete-time systems, with delayed states and/or outputs (only for the continuous-time case), and norm-bounded parametric uncertainties is considered. The objective is to design a linear output feedback controller such that, for the unknown state and output time-delays and all admissible norm-bounded parameter uncertainties, the feedback system remains robustly stable and the transfer function from the exogenous disturbances to the state-error outputs meets the prescribed Hinfinity norm upper-bound constraint. The output feedback structure does not depend on the time-delay. The conditions for the existence of the desired robust Hinfinity output feedback and the analytical expression of these controllers, are then characterized in terms of matrix Riccati-type inequalities. In the continuous-time context, both the time-invariant and the time-varying cases are treated. Finally, examples are presented to demonstrate the validity and the solvability of the proposed design methods.
Still in the same context, the state-feedback robust stabilization problem for neutral systems with time-varying delays and saturating actuators is addressed. The systems considered are continuous-time, with parametric uncertainties entering all the matrices in the system representation. The model used for the representation of actuator saturations is that of differential inclusions. A saturating control law is designed and a region of initial conditions is specified within which local asymptotic stability of the closed-loop system is ensured.
Finally, the robust output-feedback stabilization problem for state-delayed systems with time-varying delays and saturating actuators is addressed. The systems considered are again continuous-time, with parametric uncertainties entering all the matrices in the system representation. Two models are used for the representation of actuator saturations: sector modeling and differential inclusions. Saturating control laws are designed, and in the case of differential inclusions, a region of initial conditions is specified within which local asymptotic stability of the closed-loop system is ensured. (Abstract shortened by UMI.)
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Grundy, Andrew. "Congestion control framework for delay-tolerant communications." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12558/.
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Detecting and dealing with congestion in delay tolerant networks is an important and challenging problem. Current DTN forwarding algorithms typically direct traffic towards particular nodes in order to maximise delivery ratios and minimise delays, but as traffic demands increase these nodes may become unusable. This thesis proposes Café, an adaptive congestion aware framework that reduces traffic entering congesting network regions by using alternative paths and dynamically adjusting sending rates, and CafRep, a replication scheme that considers the level of congestion and the forwarding utility of an encounter when dynamically deciding the number of message copies to forward. Our framework is a fully distributed, localised, adaptive algorithm that evaluates a contact’s next-hop potential by means of a utility comparison of a number of congestion signals, in addition to that contact’s forwarding utility, both from a local and regional perspective. We extensively evaluate our work using two different applications and three real connectivity traces showing that, independent of the network inter-connectivity and mobility patterns, our framework outperforms a number of major DTN routing protocols. Our results show that both Café and CafRep consistently outperform the state-of-the-art algorithms, in the face of increasing traffic demands. Additionally, with fewer replicated messages, our framework increases success ratio and the number of delivered packets, and reduces the message delay and the number of dropped packets, while keeping node buffer availability high and congesting at a substantially lower rate, demonstrating our framework’s more efficient use of network resources.
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Spasojevic, Mina. "Nonlinear optical signal processing and tunable optical delays in silicon-on-insulator waveguides." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119660.
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The continued trend of increasing demand for large communications bandwidths is placing great strain on today's communications technology. This underlines the need for improving capacities and scalability of the existing as well as the future transmission systems. Investigating the capabilities of different modulation formats presents one way of addressing the matter. This thesis explores the optical time-division (de)multiplexing (OTDM) modulation scheme and provides a platform for building an all-optical signal processing system in silicon-on-insulator (SOI) relying on OTDM. It demonstrates successful OTDM demultiplexing and tunable optical delays both implemented in silicon nanoscale optical devices. OTDM demultiplexing is carried out by exploiting the nonlinearities in silicon waveguides. It focuses on four wave mixing (FWM) phenomenon chosen for its great potential for very high data rates resulting from its instantaneous nature, in addition to the advantage of being transparent to modulation formats. The thesis demonstrates how all-optical OTDM demultiplexing can be achieved through a two step process, generation of continuously tunable delay line followed by demultiplexing process, with both steps implemented in the same silicon waveguide. It demonstrates successful 40 Gb/s-to-10 Gb/s demultiplexing resulting in four error free demultiplexed channels.For further integration of the demultiplexing process, this thesis explores achieving tunable optical delays in silicon waveguides. It shows two approaches for implementing sidewall grating structures, serial Bragg grating arrays and the step-chirped Bragg gratings. Both approaches were fabricated and characterized and demonstrate relatively large delays (up to 65 ps) in discrete steps (from 15 ps to 32 ps) over wide bandwidths (from 35 nm to 70 nm), however they require further optimization. All-optical signal processing and optical devices presented in this thesis provide building blocks and indicate future steps that can lead toward fully integrated OTDM demultiplexer in SOI.L'augmentation incessante de la demande pour de larges bandes passantes crée de grandes tensions sur les technologies de communications existantes. Cela met en évidence le besoin d'améliorer la capacité et l'extensibilité des systèmes de transmission existants et futurs. Cette question peut être résolue, entre autres, par l'exploration des capacités de formats de modulation différents. Cette thèse examine un schéma de (dé)multiplexage optique temporel (OTDM) et présente une plateforme pour la mise en place d'un système pour le traitement de signaux exclusivement optiques sur silicium sur isolant (SOI) qui s'appuie sur le démultiplexage OTDM. Le démultiplexage OTDM et les délais optiques réglables, tous deux implémentés sur des dispositifs en silicium à l'échelle nanométrique, sont démontrés avec succès. Le démultiplexage OTDM est effectuée par l'exploitation de la non-linéarité des guides d'onde sur silicium. Cette technique emploie le phénomène de mélange à quatre ondes (FWM) choisi pour son potentiel pour les très hautes fréquences de données grâce à sa nature instantanée en plus de posséder l'avantage d'être transparent aux formats de modulation. Cette thèse démontre que le démultiplexage OTDM exclusivement optique peut être effectué en deux étapes, la production de ligne à retard ajustable en continue suivit par un procédé de démultiplexage, tous deux implémentés dans le même guide d'onde sur silicium. Un démultiplexage de 40 Gb/s à 10 Gb/s résultant en quatre canaux démultiplexés sans erreur est démontré avec succès. Pour une intégration plus poussée du procédé de démultiplexage, cette thèse examine la possibilité de créer un délai optique ajustable dans les guides d'onde sur silicium. Deux approches pour la mise en œuvre de réseaux sur les parois d'un guide d'onde sont démontrées: une série de réseaux de Bragg et des réseaux de Bragg chirpés. Les deux approches ont été fabriquées et caractérisées et démontrent des délais relativement larges (jusqu'à 65 ps) par étapes discontinues (de 15 ps à 32 ps) sur une bande passante large (de 35 nm à 70 nm). Ces approches doivent cependant être davantage optimisées. Le traitement de signaux exclusivement optique et les dispositifs optiques présentés dans cette thèse fournissent les étapes et les informations nécessaires qui pourraient mener à un démultiplexeur OTDM sur silicium complètement intégré.
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Ospanov, Asset. "DELAY DIFFERENTIAL EQUATIONS AND THEIR APPLICATION TO MICRO ELECTRO MECHANICAL SYSTEMS." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5674.
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Delay differential equations have a wide range of applications in engineering. This work is devoted to the analysis of delay Duffing equation, which plays a crucial role in modeling performance on demand Micro Electro Mechanical Systems (MEMS). We start with the stability analysis of a linear delay model. We also show that in certain cases the delay model can be efficiently approximated with a much simpler model without delay. We proceed with the analysis of a non-linear Duffing equation. This model is a significantly more complex mathematical model. For instance, the existence of a periodic solution for this equation is a highly nontrivial question, which was established by Struwe. The main result of this work is to establish the existence of a periodic solution to delay Duffing equation. The paper claimed to establish the existence of such solutions, however their argument is wrong. In this work we establish the existence of a periodic solution under the assumption that the delay is sufficiently small.
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Huo, Jiale. "On queued testing and its application to delay-insensitive systems." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19649.
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The thesis elaborates a so-called queued testing framework for input/output transition systems (IOTS) and demonstrates its applicability to delay-insensitive (DI) systems. IOTS are an appropriate model of systems with concurrent input and output, such as distributed systems and asynchronous circuits. We develop the queued testing framework based on the assumption that output of IOTS cannot be blocked. For this, a tester is separated into two independent processes: one applies stimuli and the other observes responses of a system under test through finite queues. We apply queued testing to DI systems, concurrent systems that are invariant under communication delays. As we prove, however, most DI systems are not robust, which means that not all input actions are acceptable (specified) in each state. The theorem is proved for a unified formalization of DI systems that considers a wide range of delay models: single-capacity buffers, queues, stacks, etc. To test DI systems, we extend the queued testing framework, which is originally elaborated for fully specified IOTS, to cover partially specified IOTS by preventing testers from sending unspecified input actions. Case studies in the thesis demonstrate that the extended queued testing framework is applicable to DI systems.
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VonFange, Ross. "A device for synchronous Ethernet packet delay." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1490.
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Thomas, Lee Davis. "Effects of d-amphetamine on signaled and unsignaled delays to reinforcement." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-1/thomasl/leethomas.pdf.
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Soleymani, S. M. Ali. "Design and analysis of micro-mirror based tunable optical delay line." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81571.
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Optical delay line module is an important building block for advanced communication systems such as OCDMA and OTDMA. The past decade has seen a large research and development activity in this area.In this thesis, design and performance analysis of a tunable optical delay line which employs pop-up MEMS micro-mirrors have been described. The delay paths which their lengths are in binary fashion are free-space based delay lines. Micro-mirrors operate as a switch to redirect the light through delay paths. One of the main characteristic of this design is to provide constant optical power loss for different delay times. Computer simulations have been shown to evaluate the performance of the system to different sources of misalignments.
The result of simulations suggests using correction mirrors in order to decrease the optical power loss due to misalignment. It has been also concluded that improvement of pop-up micro-mirrors as a main source of misalignment, will alleviate the performance remarkably.
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Milosavljevic, Ivana. "Power Electronics System Communications." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/31218.
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This work investigates communication issues in high-frequency power converters. A novel control communication network (Power Electronics System Network or PES Net) is proposed for modular, medium and high-power, converters. The network protocol, hardware and software are designed and implemented. The PES Net runs at 125 Mb/s over plastic optical fiber allowing converter switching frequencies in excess of 100 kHz. Communication control is implemented in a field programmable gate array device. A novel synchronization method applicable to ring networks is proposed. The effect of the communication delay on the power converter operation is studied.Master of Science
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Saad, Tarek W. "Support of delay-sensitive applications over MPLS and differentiated services enabled networks." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6218.
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The thesis proposes a framework for applying effective QoS techniques in a Diffserv MPLS network to ensure predictable levels of QoS at the network layer to delay-sensitive applications. This approach will enable network edge routers to discriminate against classes of traffic, and dynamically map it into pre-established Label Switched Paths (LSPs) that emulate classes of service (e.g. gold, silver, etc.). We investigate the several contributors of delays in a packet switched IP network in order to ensure minimal service end-to-end delay. We present a number of scenarios to prove our conclusions. Our work is first simulated on a network simulation tool, Optimized Network Engineering Tool (OPNET) [16]. The second phase of the experimental work is to realize, and evaluate our model on an MPLS test-bed of networked PCs running on Linux Operating System (OS) and connecting a number of Multimedia Streaming server/client applications. The Linux kernel is patched so it becomes Diffserv MPLS-enabled. (Abstract shortened by UMI.)
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Zhang, Dan. "Impulse noise detection techniques for retransmission to reduce delay in DSL systems." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107853.
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To protect Digital Subscriber Line (DSL) systems against impulse noise (IN), interleaving combined with Reed-Solomon (RS) coding is typically deployed in the conventional DSL standards. However, interleaving introduces a long delay. To reduce such delay in conventional DSL systems that are corrupted by IN, retransmission can be used instead of interleaving. For an effective retransmission, reliable detection of corruption due to IN is required. In this thesis, we consider three detection approaches. The first one is based on the RS decoding status since the decoder either detects the number of corrected errors or reports the failure of decoding when the errors exceed its correction capability. Retransmission is required when the transmitted codeword cannot be decoded. The second one uses the square distance method in which erasures are marked for unreliably received samples and retransmission is issued when the number of erased samples exceeds a certain threshold. Finally, the third one takes advantage of the unused tones in DSL systems in order to detect whether IN is present. For all the above approaches, we analyze the average retransmission delay and bit error rate (BER) and provide simulation results to validate the analysis. It is found that the "Decoding Status" approach can reliably indicate received signals corrupted by IN. We consider it a trustful way to correct the symbols and detect the errors since the probability of wrong decoding for the received symbol is very low. In the frequency selective fading channel and with the presence of Repetitive Electrical Impulse Noise (REIN), numerical results using different parameters such as various channel responses and IN powers show that retransmission offers a short delay while effectively avoiding transmission errors. Specifically, with the "Decoding Status" approach, the error caused by REIN can be completely avoided with the average retransmission delay of around 0.029ms and the maximum round-trip delay of 0.75ms.Pour protéger les systèmes de ligne d'abonné numérique (DSL) contre le bruit impulsif (IN), les normes conventionnelles de DSL sont typiquement déployées avec de l'entrelacement combiné au codage Reed-Solomon (RS). Cependant, l'entrelacement introduit un long retard. Afin de réduire ce retard dans les systèmes conventionnels de DSL qui sont corrompus par l'IN, une retransmission peut être utilisée au lieu de l'entrelacement. Pour une retransmission efficace, une détection fiable de l'altération causée par l'IN est nécessaire. Dans cette thèse, nous considérons trois approches de détection. La première est basée sur le statut du décodage RS puisque le décodeur détecte le nombre d'erreurs corrigées ou bien signale qu'il a échoué quand le nombre d'erreurs dépassent sa capacité de correction. Une retransmission est nécessaire quand le mot codé transmis ne peut pas être décodé. La deuxième méthode emploie la méthode des distances carrées dans laquelle les suppressions sont marquées pour les échantillons reçus non fiables et une retransmission est émise quand le nombre d'échantillons supprimés dépasse un certain seuil. Enfin, la troisième méthode est de profiter des tonalités inutilisées dans les systèmes de DSL afin de détecter si l'IN est présent. Pour toutes les approches ci-dessus, nous analysons le retard moyen et le taux d'erreur sur les bits (BER) et nous fournissons des résultats de simulation pour valider l'analyse. Il est constaté que l'approche du statut de décodage peut indiquer de manière fiable les signaux reçus corrompus par IN et nous le considérons comme une manière efficace pour corriger les symboles et pour détecter les erreurs puisque la probabilité de mauvais décodage pour le symbole reçu est très basse. Dans la voie sujette à évanouissement progressif de fréquences avec la présence de bruit électrique impulsif répétitif (REIN), les résultats numériques utilisant des paramètres différents tels que de diverses réponses de voies de transmission et de diverses puissances du IN prouvent que la retransmission offre un court retard tout en évitant efficacement les erreurs de transmission. Spécifiquement, avec l'approche du statut de décodage, l'erreur provoquée par le REIN peut complètement être évitée avec un délai de retransmission moyennant 0.029ms et un retard aller-retour maximale est de 0.75ms.
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Shallwani, Aziz. "An adaptive playout algorithm with delay spike detection for real-time VoIP /." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80143.
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As the Internet is a best-effort delivery network, audio packets may be delayed or lost en route to the receiver due to network congestion. To compensate for the variation in network delay, audio applications buffer received packets before playing them out. Basic algorithms adjust the packet playout time during periods of silence such that all packets within a talkspurt are equally delayed. Another approach is to scale individual voice packets using a dynamic time-scale modification technique based on the WSOLA algorithm.In this work, an adaptive playout algorithm based on the normalized least mean square algorithm, is improved by introducing a spike-detection mode to rapidly adjust to delay spikes. Simulations on Internet traces show that the enhanced bi-modal playout algorithm improves performance by reducing both the average delay and the loss rate as compared to the original algorithm.