Penn Engineering

The School of Engineering and Applied Science, established in 1852, is composed of six academic departments and numerous interdisciplinary centers, institutes, and laboratories. At Penn Engineering, we are preparing the next generation of innovative engineers, entrepreneurs and leaders. Our unique culture of cooperation and teamwork, emphasis on research, and dedicated faculty advisors who teach as well as mentor, provide the ideal environment for the intellectual growth and development of well-rounded global citizens.

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Now showing 1 - 10 of 4570
  • Publication
    Single-walled carbon nanotubes in superacid: X-ray and calorimetric evidence for partly ordered H2SO4
    (2005-07-01) Zhou, Wei; Fischer, John E; Fischer, John E; Heiney, P. A; Fan, H.; Davis, Virginia A; Pasquali, M.; Smalley, Richard E
    Liquid anhydrous sulfuric acid forms a partly ordered structure in the presence of single-walled carbon nanotubes (SWNTs). X-ray scattering from aligned fibers immersed in acid shows the formation of molecular shells wrapped around SWNTs. Differential scanning calorimetry of SWNT-acid suspensions exhibits concentration-dependent supercooling/melting behavior, confirming that the partly ordered molecules are a new phase. We propose that charge transfer between nanotube π electrons and highly oxidizing superacid is responsible for the unique partly ordered structure.
  • Publication
    Authoring Multi-Actor Behaviors in Crowds With Diverse Personalities
    (2013-01-01) Shoulson, Alexander; Kapadia, Mubbasir; Badler, Norman I; Durupinar, Funda; Badler, Norman I
    Multi-actor simulation is critical to cinematic content creation, disaster and security simulation, and interactive entertainment. A key challenge is providing an appropriate interface for authoring high-fidelity virtual actors with featurerich control mechanisms capable of complex interactions with the environment and other actors. In this chapter, we present work that addresses the problem of behavior authoring at three levels: Individual and group interactions are conducted in an event-centric manner using parameterized behavior trees, social crowd dynamics are captured using the OCEAN personality model, and a centralized automated planner is used to enforce global narrative constraints on the scale of the entire simulation. We demonstrate the benefits and limitations of each of these approaches and propose the need for a single unifying construct capable of authoring functional, purposeful, autonomous actors which conform to a global narrative in an interactive simulation.
  • Publication
    A Reasoning Framework for Autonomous Urban Driving
    (2008-06-04) Ferguson, Dave; Likhachev, Maxim; Likhachev, Maxim; Dolan, John
    Urban driving is a demanding task for autonomous vehicles as it requires the development and integration of several challenging capabilities, including high-level route planning, interaction with other vehicles, complex maneuvers, and ultra-reliability. In this paper, we present a reasoning framework for an autonomous vehicle navigating through urban environments. Our approach combines route-level planning, context-sensitive local decision making, and sophisticated motion planning to produce safe, intelligent actions for the vehicle. We provide examples from an implementation on an autonomous passenger vehicle that has driven over 3000 autonomous kilometers and competed in, and won, the Urban Challenge.
  • Publication
    Photoacoustic effect for multiply scattered light
    (2007-09-25) Fisher, Andrew R; Schotland, John C; Schotland, John C
    We consider the photoacoustic effect for multiply scattered light in a random medium. Within the accuracy of the diffusion approximation to the radiative transport equation, we present a general analysis of the sensitivity of a photoacoustic wave to the presence of one or more small absorbing objects. Applications to tumor detection by photoacoustic imaging are suggested.
  • Publication
    Quantifying the Gap Between Embedded Control Models and Time-Triggered Implementations
    (2005-12-08) Yazarel, Hakan; Girard, Antoine; Alur, Rajeev; Alur, Rajeev
    Mapping a set of feedback control components to executable code introduces errors due to a variety of factors such as discretization, computational delays, and scheduling policies. We argue that the gap between the model and the implementation can be rigorously quantified leading to predictability if the implementation is viewed as a sequence of control blocks executed in statically allocated time slots on a time-triggered platform. For linear systems controlled by linear controllers, we show how to calculate the exact error between the model-level semantics and the execution semantics of an implementation, allowing us to compare different implementations. The calculated error of different implementations is demonstrated using simulations on illustrative examples.
  • Publication
    Structure and properties of C60@SWNT
    (2001-11-26) Russo, Richard M; Chikkannanavar, Satishkumar B; Stercel, Ferenc; Smith, Brian W; Luzzi, David E; Russo, Richard M; Chikkannanavar, Satishkumar B; Stercel, Ferenc; Luzzi, David E
    Our recent achievement of high-yield C60@SWNT synthesis facilitates characterization by various techniques, including selected area electron diffraction (SAD) and Raman spectroscopy. The obtained SAD patterns show that interior C60 molecules sit on a simple 1-D lattice having a parameter of 1.00 nm. Simulated SAD patterns and real-space measurements both support this determination and do not indicate a lattice with a more complex basis, e.g. a dimer basis. Empty and bulk-filled SWNTs (22%, 56%, and 90% yields), each subjected to identical processing steps, were examined by room temperature Raman spectroscopy. Systematic differences are seen between the spectra of filled and unfilled SWNTs, particularly with respect to the G- and RBM-bands of the nanotubes. We present a possible explanation for this behavior.
  • Publication
    NGL/LPG Extraction from Marcellus Shale Gas
    (2015-05-04) Champagne, Jocelyn; Ordonez, Freddy; Zhang, Zhiyi
    This process describes a design in which 6 million metric tons per annum of Marcellus Shale Gas is separated into its components through heat exchangers, pressure drops, and, finally, flowing through distillation columns. The goal was essentially to remove all of the methane gas as the overhead product of the heavy removal column and use the subsequent columns to fraction off heavier hydrocarbons. Heat exchangers could not remove sufficient heat from the feed prior to entering the columns and as a result, the overhead product for the heavy removal column consists of 84% by mole of methane and 15% by mole of ethane. Essentially all of the methane is being removed with the overhead product of the HRC but 85% of ethane is being removed here as well. By selling the major product (ethane) and the byproducts (propane and butane), our process design solution yields a net present value of $166.0 million, with an internal rate of return of 32.3%. The high profitability is secured in a sensitivity analysis on the ethane selling price, the total permanent investment, and the total fixed cost.
  • Publication
    Topological conditions for in-network stabilization of dynamical systems
    (2013-04-01) Pajic, Miroslav; Sundaram, Shreyas; Mangharam, Rahul; Pappas, George; Pajic, Miroslav; Sundaram, Shreyas; Mangharam, Rahul; Pappas, George
    We study the problem of stabilizing a linear system over a wireless network using a simple in-network computation method. Specifically, we study an architecture called the "Wireless Control Network'' (WCN), where each wireless node maintains a state, and periodically updates it as a linear combination of neighboring plant outputs and node states. This architecture has previously been shown to have low computational overhead and beneficial scheduling and compositionality properties. In this paper we characterize fundamental topological conditions to allow stabilization using such a scheme. To achieve this, we exploit the fact that the WCN scheme causes the network to act as a linear dynamical system, and analyze the coupling between the plant's dynamics and the dynamics of the network. We show that stabilizing control inputs can be computed in-network if the vertex connectivity of the network is larger than the geometric multiplicity of any unstable eigenvalue of the plant. This condition is analogous to the typical min-cut condition required in classical information dissemination problems. Furthermore, we specify equivalent topological conditions for stabilization over a wired (or point-to-point) network that employs network coding in a traditional way -- as a communication mechanism between the plant's sensors and decentralized controllers at the actuators.
  • Publication
    A Hierarchical Database Model for a Logic Programming Language
    (1988-03-01) Finin, Timothy; McGuire, James
    This paper presents an extended Clausal Database Model for a logic programming language. Instead of being restricted to one global database, as is the case with Prolog, we allow segmentation of the database into database units which are linked together into a semi-lattice. Each database unit defines a database view which includes clauses which have been asserted into that unit as well as clauses inherited from its ancestors higher in the lattice structure. This model supports arbitrary retraction. Retracting a clause in a database unit effectively blocks its inheritance for that unit and all of its descendants. Motivations for using this model are given. We also discuss the implementation of a Prolog meta-interpreter that uses this model. (hereafter referred to as (Phd) or Prolog Hierarchical Database) This meta-interpreter is in the spirit of Prolog and therefore has a version of assert, retract and cut.
  • Publication
    Interactive design of complex time-dependent lighting
    (1995-03-01) Dorsey, Julie; Arvo, James; Greenberg, Donald
    Visualizing complicated lighting sequences while designing large theatrical productions proves difficult. The author provides some techniques that achieve fast interaction regardless of scene and lighting complexity, even when used with costly rendering algorithms.