No description available.

In recent years the United States Navy has concentrated most of its Anti-Submarine Warfare (ASW) research and development efforts toward passive sonar. Its ability to locate enemy targets without being detected gives the passive sonar system a supreme strategic advantage over its active counterpart. One aspect of passive sonar signal processing is the time delay estimation of an underwater acoustic wavefront. From this estimation the location and velocity of the radiating source (target) can then be determined. This report compares two popular methods of estimating time delay utilizing computer simulations of each: the cross correlator and the beamformer.

Most modem techniques for high resolution processing of closely spaced signals assume either uncorrelated noise or require knowledge of the noise covariance matrix. These assumptions are often invalid in practice. Here we propose a Pseudo-Autoregressive (PAR (M, <i>p</i>) model for estimation of an arbitrary number of signals M in the presence of a <i>p</i>-th order autoregressive (AR) noise environment. We derive the Cramer-Rao Lower Bound (CRLB) for the parameters of damped exponential signals in the colored noise case. A closed-form expression for the Cramer-Rao Lower Bound for the Pseudo-Autoregressive (PAR(<i>M,p</i>) model is obtained. Some special cases are investigated, for example, the PAR(<i>M,p</i>) model for <i>p</i> = 0, i.e., the white noise case, where our results agree with previous research results. We then evaluate the Cramer-Rao Lower Bound for two possibly closely spaced signals in a colored noise environment, showing that the colored noise assumption can lead to a much lower variance bound for the exponential parameters than under the white noise assumption. An algorithmic procedure is presented for the identification of the parameters of exponential signals, measured in colored noise. Previous papers on identifying sinusoids in noise have concentrated mainly on white noise disturbances. In a practical environment however, the disturbance is usually colored; sea-clutter in a radar context, is a lowpass type noise for example. When least squares type estimates are used in the colored noise environment, this usually leads to an unacceptable bias in the estimates. We propose an identification method, named Singular Value Decomposition Bias Elimination (SVDBE), in which it is assumed that the noise can be represented well by an AR process. The parameters of this noise model are then iteratively estimated along with the exponential signal parameters, via Singular Value Decomposition (SVD) based least squares. The iteration process starts with the white noise assumption, and improves on that by allowing the parameters in the noise model to vary away from the white noise case. A high order modal decomposition is found, and the best subset of the identified modes is selected. Simulations assess the merits of the introduced SVDBE algorithm, by comparison of the estimation results with the derived Cramer-Rao Lower Bound. / Ph. D.

Measurement of traffic congestion and evaluation of highway capacity has become an important topic. Highway capacity depends on the operating speed of the traffic and the spacing of vehicles. The purpose of this thesis is two-fold: (a) to find a simple and inexpensive method which can measure both the speed and volume of traffic together, and (b) to use the analysis of the data collected in evaluating highway capacity. It is believed that the simple method developed would be able to differentiate between commercial and passenger traffic. The method used consisted of two standard pneumatic road tubes and a portable tape recorder. The clicking sounds of the traffic counters were recorded on the tape which was analyzed in the laboratory. The average speed of the traffic depends on lane density, provided all other factors such as geometric features of the roadway, traffic factors and miscellaneous conditions remain constant. At higher density, the standard deviation of velocities of vehicles drops off. Also at higher density, vehicles travel much closer for a given velocity. From headway determination of vehicles, it is possible to analyze bunching characteristics of the traffic. It was found that the traffic on the V. P. I. campus is increasing every year. Still, the roads of the campus are not running over capacity. The procedure developed in this study proved to be of sufficient accuracy to be useful in further research of traffic flow. / Master of Science

Recent trends in the computer market suggest that emerging computing platforms will be increasingly parallel and heterogeneous, in order to satisfy the user demand for improved performance and superior energy savings. Heterogeneity is a promising technology to keep growing the number of cores per chip without breaking the power wall. However, existing system software is able to cope with homogeneous architectures, but it was not designed to run on heterogeneous architectures, therefore, new system software designs are necessary. One innovative design is the multikernel OS deployed by the Barrelfish operating system (OS) which partitions hardware resources to independent kernel instances that communicate exclusively by message passing, without exploiting the shared memory available amongst different CPUs in a multicore platform. Popcorn Linux implements an extension of the multikernel OS design, called replicated-kernel OS, with the goal of providing a Linux-based single system image environment on top of multiple kernels, which can eventually run on different ISA processors. A replicated-kernel OS replicates the state of various OS sub-systems amongst kernels that cooperate using message passing to distribute or access various services uniquely available on each kernel. In this thesis, we present mechanisms to distribute signals, namespaces, inter-thread synchronizations and socket state replication. These features are built on top of the existing messaging layer, process or thread migration and address space consistency protocol to provide the application with an illusion of single system image and developers with the SMP programming environment they are most familiar with. The mechanisms developed were unit tested with micro benchmarks to validate their correctness and to measure the gained speed up or additive overhead. Real-world applications were also used to benchmark the developed mechanisms on homogeneous and on heterogeneous architectures. It is found that the contributed Popcorn synchronization mechanism exhibits overhead compared to vanilla Linux on multicore as Linux's equivalent mechanisms are tightly coupled with underlying hardware cache coherency protocol, therefore, faster than software message passing. On heterogeneous platforms, the developed mechanisms allow to transparently map each portion of the application to the processor in the platform on which the execution is faster. Optimizations are recommended to further improve the performance of the proposed synchronization mechanism. However, optimizations may force the userspace application and libraries to be rewritten in order to decouple their synchronization mechanisms of shared memory, therefore losing transparency, which is one of the primary goals of this work. / Master of Science

Thesis (Ed.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / This study was designed to investigate student understanding of fundamental concepts in the engineering course, signals and systems. The aim of this study was threefold: (1) to identify faulty reasonings students invoke in their study of signals and systems; (2) to identify the reasoning resources that explain the origin of student faulty reasonings; and (3) to identify consistencies in students' invocation of reasoning resources across different signals and systems topics. Fifty-one undergraduate students majoring in aerospace engineering at the Massachusetts Institute of Technology participated in this study. Seven oral problems were designed to test student understanding of central topics in the study of continuous-time linear, time-invariant systems. Participants were divided into seven cohorts and each cohort was interviewed on a different problem. Interview transcriptions were analyzed based from a complex systems perspectiv to identify the knowledge elements of reasoning resources that characterize student reasoning in signals and systems. [TRUNCATED] / 2999-01-02

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The debilitating social, economic and environmental ramifications of traffic congestion are experienced in large cities the world over. The optimisation of traffic signal timings at signalised road intersections attempts to mitigate the extent of these adverse effects of traffic congestion by reducing the delay time experienced by vehicles in a transport network. Today, traffic signal control schemes may be classiffied into one of two main classes, namely fixed-time traffic signal control strategies, which are typically cyclic in nature, and vehicle-actuated traffic signal control strategies, which are typically acyclic in nature. Generally, cyclic control strategies tend to lack exibility, and are unable to adapt to short-term uctuations in traffic ow rates, resulting in green times that are either too long or too short. On the other hand, acyclic control strategies tend to lack coordination between intersections, resulting in vehicles being required to stop at the majority of signalised intersections they encounter. Self-organising traffic signal control has been proposed as an attractive alternative form of control which both exhibits exibility and facilitates a global coordination between intersections as a result of localised signal switching policies. Two examples of existing self-organising traffic signal control algorithms from the literature include an algorithm proposed by Lammer and Helbing in 2008 and an algorithm proposed by Gershenson and Rosenblueth in 2012. These algorithms have been shown to outperform both optimised fixed-time traffc signal control techniques as well as state-of-the-art vehicle actuated trffic signal control techniques, in terms of reducing vehicle delay time in a transport network. A draw-back of both of these self-organising approaches, however, is that their effective operation relies on carefully selected parameter values; poorly selected parameter values may render these algorithms very ineffectual. In this dissertation, three novel self-organising traffic signal traffic control algorithms are proposed. These three algorithms assume the use of existing radar detection sensors mounted at the intersection to provide the necessary input data. The radar detection sensors are capable of detecting and tracking individual vehicles approaching an intersection, providing real-time information pertaining to their physical dimensions, velocities, and ranges from the intersection in terms of both time and distance. The three traffic signal control algorithms are free of any user-specialised parameters, and instead rely solely on the data provided by the radar detection sensors to inform their signal switching policies. The first of these traffic signal control algorithms is inspired by inventory control theory, and draws parallels between the monetary costs typically considered in inventory control models and the delay time costs associated with traffic control at signalised intersections, which the algorithm attempts to minimise. The second novel traffic control algorithm is inspired by the chemical process of osmosis in which solvent molecules move unaided from a region where they are highly concentrated, across a semi-permeable membrane, into a region of high solute molecule concentration. The algorithm models vehicles approaching an intersection as solvent molecules and the physical space available for the vehicles to occupy once they have passed through the intersection as solute molecules. Following this analogy, the intersection is considered to be the semi-permeable membrane. The third traffic control algorithm is a hybrid of the inventory and osmosis-inspired algorithms together with an intersection utilisation maximisation technique, which prevents unnecessary or prolonged underutilisation of an intersection. The three novel trafficc control algorithms, together with the algorithms of Lammer and Helbing, and of Gershenson and Rosenblueth, as well as a fixed-time control algorithm, are implemented in a purpose-built microscopic traffic simulation modelling framework. Several measures are employed to evaluate the relative performances of the algorithms. These measures include the usual mean and maximum resulting delay times incurred by vehicles and the saturation level of the roadways in the transport network, as well as three novel performance measure indicators which include the mean number of stops made by vehicles, their mean normalised delay time and the mean normalised number of stops made. The algorithms are compared in the context of a linear corridor road network topology as well as a grid road network topology under various traffic ow conditions. The overall performance of the novel hybrid traffic signal control algorithm is found to be superior for the corridor road network topology, while the performance of the osmosis-inspired algorithm is found to be superior for the grid road network topology. / AFRIKAANSE OPSOMMING:Die negatiewe sosiale, ekonomiese en omgewingsimpak van verkeersopeenhoping word in groot stede regoor die w^ereld ervaar. Die doel met die optimering van verkeersligwerkverrigting by straatkruisings is om die omvang van hierdie negatiewe impak tee te werk deur die vertraging van voertuie in 'n vervoernetwerk te verminder. Hedendaagse verkeersbeheeralgoritmes kom in een van twee hoofklasse voor, naamlik vaste-tyd beheerstrategiee, wat gewoonlik siklies van aard is, en beheerstrategiee gebaseer op voertuigopsporing, wat tipies asiklies van aard is. Oor die algemeen beskik sikliese beheerstrategiee nie oor genoegsame buigsaambeid om aan te pas by kort-termyn fluktuasies in verkeersvloei nie, wat tipies daartoe lei dat hul groentye spesifiseer wat of te lank of te kort is. Aan die ander kant is asikliese beheerstrategiee nie daartoe in staat om koordinasie tussen naasliggende straatkruisings te bewerkstellig nie, wat weer daartoe lei dat voertuie genoodsaak word om by die oorgrote meerderheid straatkruisings op hul pad te stop. Die self-organiserende beheer van verkeersligte is as 'n aantrektlike, buigsame alternatief voorgestel wat in staat is om globale koordinasie tussen naasliggende straatkruisings as gevolg van gelokaliseerde seinstrategiee te bewerkstellig. Twee voorbeelde van bestaande self-organiserende verkeersbeheeralgoritmes in die literatuur is die algoritmes wat in 2008 deur Lammer and Helbing en in 2012 deur Gershenson en Rosenblueth voorgestel is. Daar is aangetoon dat hierdie algoritmes daartoe in staat is om ge-optimeerde vaste-tyd beheerstrategiee sowel as gevorderde strategiee gebaseer op voertuigopsporing uit te stof in terme van 'n vermindering van die vertraging van voertuie in 'n vervoernetwerk. 'n Nadeel van beide hierdie self-organiserende benaderings is egter dat hul doeltreffende werkverrigting berus op versigtig-gekose parameterwaardes; willekeurige parameterwaardes mag lei na hoogs ondoeltreffende werkverrigitng van die algoritmes. Drie nuwe self-organiserende verkeersbeheeralgoritmes word in hierdie proefskrif voorgestel. Hierdie drie algoritmes maak vir hul toevoerdata staat op die beskikbaarhed van bestaande radar opsporingsensors wat by straatkruisings geinstalleer is. Die sensors is daartoe in staat om individuele voertuie wat 'n straatkruising nader, op te spoor, te volg en intydse data oor hul fisiese dimensies, snelhede, en afstande na die kruising (in terme van beide tyd en afstand) te lewer. Die drie algoritmes bevat geen gebruikers-gespesifiseerde parameters nie, en maak in plaas daarvan slegs gebruik van die sensortoevoerdata om hul beheerstrategiee te bepaal. Die eerste van hierdie verkeersbeheeralgoritmes is deur die teorie van voorraadbeheer geinspireer en maak gebruik van parallelle tussen die monet^ere kostes wat tipies in voorraadbeheermodelle voorkom en die kostes in terme van vertragingstyd wat met verkeersbeheer by straatkruisings aangegaan word, en wat deur die algoritme geminimeer word. Die tweede verkeersbeheeralgoritme is deur die chemiese proses van osmose geinspireer, waar molekules van 'n oplossingsmiddel sonder eksterne hulp vanaf 'n gebied waar hul in hoe konsentrasie voorkom, deur 'n gedeeltelik-deurlaatbare membraan beweeg na 'n gebied waarin hul ook in hoe konsentrasie, maar in opgeloste vorm voorkom. Die algoritme modelleer voertuie wat 'n straatkruising nader as die molekules van die oplossingsmiddel en die fisiese ruimte wat aan die ander kant van die kruising beskikbaar is om deur voertuie beset te word, as molekules in opgeloste vorm. In hierdie analogie word die kruising self as die gedeeltelik-deurlaatbare membraan beskou. Die derde algoritme is 'n hibriede strategie waarin elemente van die eerste twee algoritmes in samewerking met 'n tegniek vir die maksimering van straatkruisingsbenutting gekombineer word, en wat wat ten doel het om onnodige of verlengte onderbenutting van die kruising te vermy. Hierdie drie nuwe verkeersbeheeralgoritmes word, tesame met die bestaande algoritmes van Lammer en Helbing, en van Gershenson en Rosenblueth, asook 'n vaste-tyd beheeralgoritme, in 'n mikroskopiese verkeersimulasiemodelleringsraamwerk wat spesifiek vir die doel ontwerp is, geimplementeer. Verskeie maatstawwe word ingespan om die relatiewe werkverrigting van die algoritmes te evalueer. Hierdie maatstawwe sluit in die gebruiklike gemiddelde en maksimum vertragingstye van voertuie en die versadigingsvlak van strate in die vervoernetwerk, sowel as drie nuwe maatstawwe, naamlik die gemiddelde aantal stoppe deur voertuie, hul genormaliseerde vertragingstye en die gemiddelde, genormaliseerde aantal stoppe. Die algoritmes word in die kontekste van 'n line^ere topologie van opeenvolgende straatkruisings en 'n netwerktopologie van reghoekige straatblokke onder verskeie verkeersdigthede met mekaar vergelyk. Daar word bevind dat die nuwe hibriede algoritme die beste vaar in die line^ere topologie, terwyl die osmose-ge inspireerde algoritme die ander algoritmes uitstof in die straatblok-netwerktopologie.

The monitoring of traffic signal systems can be of great importance for identifying problems, self-assessment, budgeting, creating the strategy for future steps, etc. Monitoring procedure was developed through a set of dashboards with relevant signal performance and reliability measures. The dashboards were created to reflect performance and reliability of a specific signal system on a weekly or monthly level. The author used data from ATMS.now signal system central software to illustrate how similar dashboards could be developed from any central software to enable operators to promptly and efficiently monitor various parameters of traffic signals. The main outcome of the study is a pair of Excel dashboards accompanied with appropriate user manual. The dashboards represent the tool for monitoring which can be helpful in the process of evaluation for traffic signal systems. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Signal retiming, or signal optimization process, has not changed much over the last few decades. Traditional procedures rely on low-resolution data and a low-fidelity modeling approach. Such developed signal timing plans always require a fine-tuning process for deployed signal plans in field, thus questioning the very benefits of signal optimization. New trends suggest the use of high-resolution data, which are not easily available. At the same time, many improvements could be made if the traditional signal retiming process was modified to include the use of medium-resolution data and high-fidelity modeling. This study covers such an approach, where a traditional retiming procedure is modified to utilize large medium-resolution data sets, high-fidelity simulation models, and powerful stochastic optimization to develop robust signal timing plans. The study covers a 28-intersection urban corridor in Southeastern Florida. Medium-resolution data are used to identify peak-hour, Day-Of-Year (DOY) representative volumes for major seasons. Both low-fidelity and high-fidelity models are developed and calibrated with high precision to match the field signal operations. Then, by using traditional and stochastic optimization tools, signal timing plans are developed and tested in microsimulation. The findings reveal shortcomings of the traditional approach. Signal timing plans developed from medium-resolution data and high-fidelity modeling approach reduce average delay by 5%-26%. Travel times on the corridor are usually reduced by up to 10.5%, and the final solution does not transfer delay on the other neighboring streets (illustrated through latent delay), which is also decreased by 10%-49% when compared with the traditional results. In general, the novel approach has shown a great potential. The next step should be field testing and validation. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

In the case of wideband (aperiodic) signals, the classical signal and noise measures used to characterize stochastic resonance do not work because their way of distinguishing signal from noise fails. In a study published earlier (L. B. Kish, 1996), a new way of measuring and identifying noise and aperiodic (wideband) signals during strongly nonlinear transfer was introduced. The method was based on using cross-spectra between the input and the output. According to the study, in the case of linear transfer and sinusoidal signals, the method gives the same results as the classical method and in the case of aperiodic signals it gives a sensible measure. In this paper we refine the theory and present detailed simulations which validate and refine the conclusions reached in that study. As neural and ion channel signal transfer are nonlinear and aperiodic, the new method has direct applicability in membrane biology and neural science (S.M. Bezrukov and I. Vodyanoy, 1997).