Department of Electrical & Systems Engineering

The Department of Electrical & Systems Engineering at the University of Pennsylvania is a leader in the areas of Electroscience, Systems Science, Network Systems and Telecommunications.





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Now showing 1 - 10 of 1100
  • Publication
    Learning Environmental Models With Multi-Robot Teams Using A Dynamical Systems Approach
    (2022-01-01) Salam, Tahiya
    Robots monitoring complex, spatiotemporal phenomena require rich, meaningful representations of the environment. This thesis presents methods for representing the environment as a dynamical system with machine learning techniques. Specifically, we formulate machine learning methods that lend to data-driven modeling of the phenomena. The data-driven modeling explicitly leverages theoretical foundations of dynamical systems theory. Dynamical systems theory offers mathematical and physically interpretable intuitions about the environmental representation. The contributions presented include distributed algorithms, online adaptation, uncertainty quantification, and feature extraction to allow for the actualization of these techniques on-board robots. The environmental representations guide robot behavior in developing strategies such as optimal sensing and energy-efficient navigation. The methods and procedures provided in this thesis were verified across complex, spatiotemporal environments and on experimental robots.
  • Publication
    Athena's Prism - A Diplomatic Strategy Role Playing Simulation for Generating Ideas and Exploring Alternatives
    (2005-05-01) Silverman, Barry G; Rees, Richard L; Toth, Jozsef A; Cornwell, Jason; O'Brien, Kevin; Johns, Michael; Caplan, Marty
    Intelligence analysts must clear at least three hurdles to get good product out the door: cognitive biases, social biases and self-imposed organizational impediments. Others (e.g., Gilovich, et al., Heuer, and Kahneman and Tversky), explain the cognitive processes that can help or trip us. A less well mapped set of dangers arises in the social dynamics of communicating tasking, working with other analysts, editing and customer interaction. Finally, the mere fact of a unit's published record creates analytic inertia - an argument at rest tends to stay at rest and one in motion (i.e., ambiguous or uncertain) tends to stay in motion. (A variation of this includes groupthink.)
  • Publication
    A Discrete-Time Stochastic Model of Job Matching
    (2003-01-01) Smith, Tony E; Zenou, Yves
    In this paper, an explicit micro scenario is developed which yields a well-defined aggregate job matching function. In particular, a stochastic model of job-matching behavior is constructed in which the system steady state is shown to be approximated by an exponential-type matching function, as the population becomes large. This steady-state approximation is first derived for fixed levels of both wages and search intensities, where it is shown (without using a free-entry condition) that there exists a unique equilibrium. It is then shown that if job searchers are allowed to choose their search intensities optimally, this model is again consistent with a unique steady state. Finally, the assumption of a fixed wage is relaxed, and an optimal 'offer wage' is derived for employers.
  • Publication
    Role and Organization of Transfers in Transit Networks
    (1992) Vuchic, Vukan R; Musso, Antonio
    Passenger transfers among transit lines involve certain "resistance", because they cause some delay and require passenger orientation and walking between vehicles on different lines. Therefore it is sometimes believed that transfers are undesirable and that they should be avoided whenever possible. The fact is, however, that transit networks with many transfer opportunities offer passengers much greater selection of travel paths than networks with disconnected lines which involve no transferring. In addition, the more transferring is performed, the greater is network efficiency, because each line can be designed optimally for its physical conditions, volume and character of demand. Consequently, when transfers are planned correctly, the resistance for passengers can be easily outweighed by the benefits transfers bring with respect to line alignments, schedules and, eventually, in better services offered. Passenger transfers among lines thus represent an important element of transit travel.
  • Publication
    Multi-Modal Control of Systems with Constraints
    (2001-12-04) Koo, T. John; Pappas, George J; Sastry, Shankar
    In multi-modal control paradigm, a set of controllers of satisfactory performance have already been designed and must be used. Each controller may be designed for a different set of outputs in order to meet the given performance objectives and system constraints. When such a collection of control modes is available, an important problem is to be able to accomplish a variety of high level tasks by appropriately switching between the low-level control modes. In this paper, we propose a framework for determining the sequence of control modes that will satisfy reachability tasks. Our framework exploits the structure of output tracking controllers in order to extract a finite graph where the mode switching problem can be efficiently solved, and then implement it using the continuous controllers. Our approach is illustrated on a robot manipulator example, where we determine the mode switching logic that achieves the given reachability task.
  • Publication
    AntiECN Marking: A Marking Scheme for High Bandwidth Delay Connections
    (2003-05-11) Kunniyur, Srisankar S
    In this paper we describe a simple scheme that uses feedback from underutilized high capacity links to allow a TCP connection to aggressively increase its sending rate. The feedback is in the form of a single bit in the packet header and is given per packet. The scheme uses aggregate information to provide feedback and does not require the routers to maintain per flow state. We show through simulations that such a scheme allow TCP connections to efficiently utilize high capacity links without increasing the implementation complexity at the routers.
  • Publication
    Arbitrary Throughput Versus Complexity Tradeoffs in Wireless Networks Using Graph Partitioning
    (2008-11-01) Sarkar, Saswati; Ray, Saikat
    Several policies have recently been proposed for attaining the maximum throughput region, or a guaranteed fraction thereof, through dynamic link scheduling. Among these policies, the ones that attain the maximum throughput region require a computation time which is linear in the network size, and the ones that require constant or logarithmic computation time attain only certain fractions of the maximum throughput region. In contrast, in this paper we propose policies that can attain any desirable fraction of the maximum throughput region using a computation time that is largely independent of the network size. First, using a combination of graph partitioning techniques and Lyapunov arguments, we propose a simple policy for tree topologies under the primary interference model that requires each link to exchange only 1 bit information with its adjacent links and approximates the maximum throughput region using a computation time that depends only on the maximum degree of nodes and the approximation factor. Then we develop a framework for attaining arbitrary close approximations for the maximum throughput region in arbitrary networks, and use this framework to obtain any desired tradeoff between throughput guarantees and computation times for a large class of networks and interference models. Specifically, given any ∊ ≻ 0, the maximum throughput region can be approximated in these networks within a factor of 1- ∊ using a computation time that depends only on the maximum node degree and ∊.
  • Publication
    Bayesian Regularization and Nonnegative Deconvolution for Time Delay Estimation
    (2004-12-13) Lin, Yuanqing; Lee, Daniel D
    Bayesian Regularization and Nonnegative Deconvolution (BRAND) is proposed for estimating time delays of acoustic signals in reverberant environments. Sparsity of the nonnegative filter coefficients is enforced using an L1-norm regularization. A probabilistic generative model is used to simultaneously estimate the regularization parameters and filter coefficients from the signal data. Iterative update rules are derived under a Bayesian framework using the Expectation-Maximization procedure. The resulting time delay estimation algorithm is demonstrated on noisy acoustic data.
  • Publication
    Light Rail Transit Systems: A Definition and Evaluation
    (1972-10-01) Vuchic, Vukan R
    Rail transit represents a family of modes ranging from light rail to regional rapid transit systems and it can be utilized in a number of different cities and types of applications. Many European cities of medium size employ very successfully light rail mode for gradual upgrading of transit service into partially or fully separated high speed, reliable transit systems. Analysis of these cities show that with population densities and auto ownership very similar to those in the United States cities, their transit systems offer a superior service and have much better usage than our cities. Many modern features of light rail technology are not known in this country. Wider use of different rail systems, greatly increased transit financing, introduction of more qualified personnel into transit industry and improved transit planning and implementation procedures are recommended to close the gap in urban transportation between some more progressive European cities and their counterparts in this country.