Engineering Commons^™

Algorithms For Message Delivery In A Micromobility Environment, Amy L. Murphy, Gruia-Catalin Roman, George Varghese

All Computer Science and Engineering Research

As computing components get smaller and people become accustomed to having computational power at their disposal at any time, mobile computing is developing as an important research area. One of the fundamental problems in mobility is maintaining connectivity through message passing as the user moves through the network. This is usually accomplished in one of two ways: search or tracking. In search, an algorithm hunts the mobile unit through the network each time a message is to be delivered, while in tracking, a specific home keeps up to date information about the current location of the mobile unit. Our paper …

The Playground Mediator: Visual Tool For Configuring And Debugging Distributed Applications, T. Paul Mccartney

All Computer Science and Engineering Research

The Mediator is a visual configuration tool for use with The Programmers' Playground distributed programming environment. With the Mediator, one can interactively launch distributed application modules, configured communication among the modules, observe communication patterns, interactively control module communication, kill running modules, and receive imported applications from a separate World Wide Web interface. This manual describes how to use the Mediator both as a stand-alone configuration tool and as a visual interface to the Playground Application Management System.

Fault-Tolerant Mobile Ip, Rajib Ghosh, George Varghese

All Computer Science and Engineering Research

We describe mechanisms to enhance the reliability and performance of Mobile IP. In Mobile IP today home agents and foreign agents are single points of failure and potential performance bottlenecks. For example, a home agent crash can lead to communication failure if the mobile is away from home. In this paper we describe new mechanisms to allow redundant home and foreign agents. Redundant agents can take over from each other in case of failure, and also split load amongst themselves. Our mechanisms are simple, transparent to existing mobile nodes, and compatible with the existing Mobile IP specification. We have implemented …

Routing Table Compression Using Binary Tree Collapse, Jonathan Turner, Qiyong Bian, Marcel Waldvogel

All Computer Science and Engineering Research

This paper describes an algorithm which can roughly halve the size of the current Internet routing tables. This algorithm is based on the radix trie representation of routing tables, which was firstly used in the BSD Unix distributions. The binary tree representation, which is a simplified case of radix tree, does well at showing the relationships among all routing table entries and provides us a way to build a collapse algorithm based on its internal structure. The binary tree collapse algorithm consists of three techniques, with the first two quite intuitive while the third is a bit more elaborate. All …

Diagnostic Screening Of Digital Mammograms Using Wavelets And Neural Networks To Extract Structure, Barry L. Kalman, Stan C. Kwasny, William R. Reinus

All Computer Science and Engineering Research

As the primary tool for detecting breast carcinoma, mammography provides visual images from which a trained radiologist can identify suspicious areas that suggest the presence of cancer. We describe an approach to image processing that reduces an image to a small number of values based on its structural characteristics using wavelets and neural networks. To illustrate its utility, we apply this methodology to the automatic screening of mammograms for mass lesions. Our results approach performance levels of trained human mammographers.

Application Development And Management In The Programmers' Playground, T. Paul Mccartney, E.F. Berkley Shands, Kenneth J. Goldman, William M. Shapiro

All Computer Science and Engineering Research

Application management refers to the process of making software applications available to end-users and providing automated mechanisms for launching and joining such applications. The Programmers' Playground is a computing environment for creating distributed applications from modular, reusable components. This paper discusses a set of tools that enable application developers to: (1) design and debug Playground distributed applications from existing "off-the-shelf" components using a visual configuration tool, (2) make new application components available on the Internet through a "launcher" service, and (3) make complete distributed applications available via a World Wide Web interface, enabling end-users to launch and join the applications …

On-Line Scheduling With Hard Deadlines, Sally A. Goldman, Jyoti Parwatikar, Subhash Suri

All Computer Science and Engineering Research

We study non-preemptive, online admission control in the hard deadline model: each job must be either serviced prior to its deadline, or be rejected. Our setting consists of a single resource that services an online sequence of jobs; each job has a length indicating the length of time for which it needs the resource, and a delay indicating the maximum time it can wait for the service to be started. The goal is to maximize total resource utilization. The jobs are non-preemptive and exclusive, meaning once a job begins, it runs to completion, and at most one job can use …

Learning From Examples With Unspecified Attribute Values, Sally A. Goldman, Stephen S. Kwek, Stephen D. Scott

All Computer Science and Engineering Research

We introduce the UAV learning model in which some of the attributes in the examples are unspecified. In our model, an example x is classified positive (resp., negative) if all possible assignments for the unspecified attributes result in a positive (resp., negative) classification. Otherwise the classificatoin given to x is "?" (for unknown). Given an example x in which some attributes are unspecified, the oracle UAV-MQ responds with the classification of x. Given a hypothesis h, the oracle UAV-EQ returns an example x (that could have unspecified attributes) for which h(x) is incorrect. We show that any class learnable in …

Agnostic Learning Of Geometric Patterns, Sally A. Goldman, Stephen S. Kwek, Stephen D. Scott

All Computer Science and Engineering Research

Goldberg, Goldman, and Scott demonstrated how the problem of recognizing a landmark from a one-dimensional visual image can be mapped to that of learning a one-dimensional geometric pattern and gave a PAC algorithm to learn that class. In this paper, we present an efficient on-line agnostic learning algorithm for learning the class of constant-dimension geometric patterns. Our algorithm can tolerate both classification and attribute noise. By working in higher dimensional spaces we can represent more features from the visual image in the geometric pattern. Our mapping of the data to a geometric pattern, and hence our learning algorithm, is applicable …

Search And Tracking Algorithms For Rapidly Moving Mobiles, Amy L. Murphy, Gruia-Catalin Roman, George Varghese

All Computer Science and Engineering Research

With the advent of wireless technology and laptops, mobility is an important area of research. A fundamental problem in this area is the delivery of messages to a moving mobile. Current solutions work correctly only for slowly moving nodes that stay in one location long enough for tracking to stabilize. In this paper we consider the problem of message delivery to rapidly moving mobile units. With these algorithms, we introduce a new method for designing algorithms based on the paradigm of considering a mobile unit as a message, and adapting traditional message passing algorithms to mobility. Our first algorithm is …

Router Plugins: A Modular And Extensible Software Framework For Modern High Performance Integrated Services Routers, Dan Decasper, Zubin Dittia, Guru Parulkar, Bernhard Plattner

All Computer Science and Engineering Research

Present day routers typically employ monolithic operating systems which are not easily upgraded and extensible. WIth the rapid rate of protocol development it is becoming increasingly important to dynamically upgrade router software in an incremental fashion. We have designed and implemented a high performance, modular, extended integrated services router software architecture in the NetBSD operating system kernel. This architecture allows code modules, called plugins, to be dynamically added and configured at run time. One of the novel features of our design is the ability to bind different plugins to individual flows; this allows for distinct plugin implementations to seamlessly coexist …

Modeling Mobile Ip In Mobile Unity, Peter J. Mccann, Gruia-Catalin Roman

All Computer Science and Engineering Research

With recent advances in wireless communication technology, mobile computing is an increasingly important area of research. A mobile system is one where independently executing components may migrate through some space during the course of the computation, and where the pattern of connectivity among the components changes as they move in and out of proximity. Mobile UNITY is a notation and proof logic for specifying and reasoning about mobile systems. In this paper it is argued that Mobile UNITY contributes to the modular development of system specifications because of the declarative fashion in which coordination among components is specified. The packet …

Tcp/Ip Implementation With Endsystem Qos, Sherlia Y. Shi, Gurudatta M. Parulkar, R. Gopalakrishnan

All Computer Science and Engineering Research

This paper presents a Real-time Upcall (RTU) [1] based TCP/IP implementation that guarantees throughput for continuous media applications and ensures low latency bounds for interactive applications. RTU is an endsystem rate-based scheduling mechanism that provides quality of service (QoS) in terms of CPU cycles, to applications. We restructured the existing NetBSD TCP/IP implementation to exploit the RTU concurrency model and to provide predictable performance. Our experimental results show that on two 200 MHz NetBSD PCs connected by a 155Mbps ATM link, the RTU based kernel TCP/IP implementation provides excellent throughput guarantees for periodic connections regardless the system or network load. …

Integrating A Constraint Mechanism With The Javabeans Model, William M. Shapiro

All Computer Science and Engineering Research

The JavaBeans component model allows users to plug together software components to create Java applications by specifying simple relationships between component events and properties. This paper describes work on augmenting the simple JavaBeans model with a multi-way constraint mechanism that allows users to graphically specify more complex multi-way contraints, resolve cyclical constraints between bean properties and graphically layout bean components. We also discuss weaknesses in the JavaBeans model and Java Abstract Windowing Toolkit (AWT) that were discovered while integrating a constraint mechanism with JavaBeans.

Terabit Burst Switching Progress Report (12/97-2/98), Jonathan S. Turner

All Computer Science and Engineering Research

This report summarizes progress on the Terabit Burst Switching Project at Washington University for the period from December 15, 1997 through March 15, 1998. Efforts during this period have concentrated on working out details of the burst switch architecture, evaluating a variety of implementation alternatives and developing the physical design of the 160 Gb/s ATM switch to allow demonstration of the burst switch within a realistic network context.

Congestion Control In Multicast Transport Protocols, Rajib Ghosh, George Varghese

All Computer Science and Engineering Research

We discuss congestion control mechanisms in multicast transport protocols and we propose TCP-M - a TCP-friendly Multicast transport protocol. TCP-M uses IP multicast to deliver data packets and acknowledgements to provide reliability. Ack implosion at the source is prevented by fusing acknowledgements at some intermediate routers. TCP-M reacts to network congestion exactly like TCP by having the sender emulate a TCP sender.

Lime: Linda Meets Mobility, Gian Pietro Picco, Amy L. Murphy, Gruia-Catalin Roman

All Computer Science and Engineering Research

LIME is a system designed to assist in the rapid development of dependable mobile applications over both wired and ad hoc networks. Mobile agents reside on mobile hosts and all communication takes place via transiently shared tuple spaces distributed across the mobile hosts. The decoupled style of computing characterizing the Linda model is extended to the mobile environment. At the application level, both agents and hosts perceive movement as a sudden change of context. The set of tuples accessible by a particular agent residing on a given host is altered transparently in response to changes in the connectivity pattern among …

Tcp Dynamic Acknowledgment Delay: Theory And Practice, Daniel R. Dooly, Sally A. Goldman, Stephen D. Scott

All Computer Science and Engineering Research

We study an on-line problem that is motivated by the networking problem of dynamically adjusting delays of acknowledgments in the Transmission Control Protocol (TCP). The theoretical problem we study is the following. There is a sequence of n packet arrival times A = and a look-ahead coefficient L. The goal is to partition A into k subsequences sigma1, sigma2, ...,sigmak (where a subsequence end is defined by an acknowledgment) that minimizes a linear combination of the cost for the number of acknowledgments sent and the cost for the additional latency introduced by delaying acknowledgments. At each arrival, an oracle provides …

Terabit Burst Switching Progress Report (6/98-9/98), Jonathan S. Turner

All Computer Science and Engineering Research

This report summarizes progress on the Terabit Burst Switching Project at Washington University for the period from June 15, 1998 through September 15, 1998.

Virtual Reality Modelling Of A Cnc Machine, Damian O'Sullivan

Theses

The increasing importance of training and upgrading skills has led to the use of new interactive technologies in the development of more effective training tools. Previous techniques for training Computer Numerical Control (CNC) machine operators, while excellent for their time, varied from brief inexpensive tutorials to expensive on the job training. A CNC machine uses a computer to perform the functions of the machine using a part program stored in the memory of the computer. This thesis describes a Virtual Reality (VR) model of a CNC milling machine, implemented within a VR environment representing a CNC workshop. Its development and …

Emission Of Excimer Radiation From Direct Current, High-Pressure Hollow Cathode Discharge, Ahmed El-Habachi, Karl H. Schoenbach

Bioelectrics Publications

A novel, nonequilibrium, high-pressure, direct current discharge, the microhollow cathode discharge, has been found to be an intense source of xenon and argon excimer radiation peaking at wavelengths of 170 and 130 nm, respectively. In argon discharges with a 100 μm diam hollow cathode, the intensity of the excimer radiation increased by a factor of 5 over the pressure range from 100 to 800 mbar. In xenon discharges, the intensity at 170 nm increased by two orders of magnitude when the pressure was raised from 250 mbar to 1 bar. Sustaining voltages were 200 V for argon and 400 V …

Generation Of Intense Excimer Radiation From High-Pressure Hollow Cathode Discharges, Ahmed El-Habachi, Karl H. Schoenbach

Bioelectrics Publications

By reducing the diameter of the cathode opening in a hollow cathode discharge geometry to values on the order of 100 μm, we were able to operate these discharges in noble gases in a direct current mode up to atmospheric pressure. High-pressure discharges in xenon were found to be strong sources of excimer radiation. Highest intensities at a wavelength of 172 nm were obtained at a pressure of 400 Torr. At this pressure, the vacuum ultraviolet (VUV) radiant power of a single discharge operating at a forward voltage of 220 V and currents exceeding 2 mA reaches values between 6% …

Mathematics, Modeling, And Modular Curriculum In Engineering Retraining Programs, Massoud Moussavi

Educational Studies Dissertations

The present study is an attempt to probe, explore, and provide an appropriate educational method for engineering retraining programs. The central concerns and implications of this study revolve around: who engineers are, how they learn, why they need to learn, and what they have to learn. The existing retraining programs also will be evaluated in order to develop a suitable retraining program for engineers.

A Study Of Transconductance Degradation In Hemt Using A Self-Consistent Boltzmann-Poisson-Schrodinger Solver, Rahim Khoie

Electrical & Computer Engineering Faculty Research

A self-consistent Boltzmann-Poisson-Schrödinger Solver is used to study the transconductance degradation in high electron mobility transistor (HEMT), which has extensively been reported by both experimental [1]-[8] and computational [9]-[ 13] researchers. As the gate voltage of a HEMT device is increased, its transconductance increases until it reaches a peak value, beyond which, the transconductance is degraded rather sharply with further increase in applied gate bias. We previously reported a two-subband self-consistent Boltzmann-Poisson- Schrödinger Solver for HEMT. [14] We further incorporated an additional self-consistency by calculating field-dependent, energy-dependent intersubband and intrasubband scattering rates due to ionized impurities and polar optical phonons.[15] …

Attitude Measurement, Mark A. Stedham, Partha P. Banerjee, Seiji Nishifuji, Shogo Tanaka

Electrical and Computer Engineering Faculty Publications

In many practical situations, it is important to determine and measure the attitude of a particular vehicle, such as a ship, an airplane, a piece of mechanical equipment such as a, crane lifter, or a spacecraft. For this reason, many attitude sensors have been developed with advanced computer and semiconductor technologies. This section first introduces the various attitude sensors with an explanation of their operating principles and then presents several methodologies for attitude measurement and determination, including ships and crane lifters, aircraft, and spacecraft applications.

A Study Of The Fundamental Operations Of A Capillary Driven Heat Transfer Device In Both Normal And Low Gravity Part 1-Liquid Slug Formation In Low Gravity, Jeffrey S. Allen, Kevin P. Hallinan, Jack Lekan

Mechanical and Aerospace Engineering Faculty Publications

Research has been conducted to observe the operation of a capillary pumped loop (CPL) in both normal and low gravity environments in order to ascertain the causes of device failure. The failures of capillary pumped heat transport devices in low gravity; specifically; evaporator dryout, are not understood and the available data for analyzing the failures is incomplete.

To observe failure in these devices an idealized experimental CPL was configured for testing in both a normal-gravity and a low-gravity environment. The experimental test loop was constructed completely of Pyrex tubing to allow for visualization of system operations. Heat was added to …

Effects Of Temperature, Water Hardness, And Recirculation On Copper Corrosion, Brian R. Weiss

Electronic Theses and Dissertations

In previous work, the effects of water quality have been shown to influence the formation of scale from copper corrosion. A general understanding of the effects of water quality on copper corrosion have been difficult to obtain because of complex interactions of water quality variables on copper corrosion in different water supply systems. The objective of this study was to examine the effects of temperature and water hardness on copper corrosion occurring in a household water supply system. The effects of recirculation were also studied in concurrence with the above water quality parameters. Electrochemical corrosion testing and corrosion by -product …

Compensation Of Processes With Time Delays, Thomas Heeg, Aidan O'Dwyer

Conference papers

Methods which allow comparisons in the use of PI and PID controller strategies for the control of first order lag plus time delay processes (FOLPD) are worthy of investigation because of the relative lack of work done in this area. In this paper, strategies for comparing performance and robustness for a PI or PID controlled FOLPD process are analysed and designed. The use of different PID controller structures for processes with time delay is also worth considering in detail. Various PID controller structures are compared by means of servo and regulator time responses, Bode plots and Nyquist plots.

Gaseous Cah Removal By Biofiltration In Presence And Absence Of A Nonionic Surfactant, J. O. Kim, Purush K. Terkonda, S. D. Lee

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The objectives of this study were to investigate the biodegradation of gaseous trichloroethylene (TCE) and tetrachloroethylene (PCE) in an activated carbon biofilter inoculated with phenol-oxidizing microorganisms and to study the effect of surfactant concentration below its critical micelle concentration (CMC) on the removal efficiency of TCE or PCE. For the enhanced biofiltration, a biodegradable nonionic surfactant was added to biofilters. The investigation was conducted using two specially built stainless steel biofilters, one for TCE and the other for PCE. The removal efficiency of gaseous TCE was 100% at a residence time of 7 min and its average inlet concentration of …

Strategies For Evaluating Software Usability, Ronan Fitzpatrick

Articles

This paper presents a usage analysis and taxonomy of methods which are used to evaluate the usability of computer systems. To accommodate the analysis and taxonomy, a matrix of strategies which can be used for effective usability evaluation is presented. Such an analysis, taxonomy and strategies support human-computer interaction (HCI) professionals who have the responsibility for ensuring computer system usability. The strategies outlined are named Virtual Engineering, Soft Modelling, Hard Review and Real World. This paper also uses a composite set of existing popular generic evaluation methods which can be used as part of these strategies. The methods used are …