Engineering Commons^™

Thread Transparency In Information Flow Middleware, Rainer Koster, Andrew P. Black, Jie Huang, Jonathan Walpole, Calton Pu

Computer Science Faculty Publications and Presentations

Existing middleware is based on control-flow centric interaction models such as remote method invocations, poorly matching the structure of applications that process continuous information flows. Difficulties cultiesin building this kind of application on conventional platforms include flow-specific concurrency and timing requirements, necessitating explicit management of threads, synchronization, and timing by the application programmer. We propose Infopipes as a high-level abstraction for information flows, and we are developing a middleware framework that supports this abstraction. Infopipes transparently handle complexities associated with control flow and multi-threading. From high-level configuration descriptions the platform determines what parts of a pipeline require separate threads or …

Information Domain Modeling Of Emergent Phenomena, Ron Fulbright

Theses and Dissertations

Study in fields such as distributed artificial intelligence (DAI), decentralized artificial intelligence (DzAI), parallel artificial intelligence (PAl), multiagent systems (MAS), computer supported cooperative work (CSCW), artificial life (AL), and complex adaptive systems (CAS) is concerned with the cooperation, coordination, communication, and coherence of multiple agents working together to achieve a common goal. The notion that the ability of a collective can exceed the sum of the individuals is a fundamental concept and a generally accepted truth. However, no general theoretical explanation exists as to why this could or should be the case. This dissertation explores such an explanation by considering …

Trusted Autonomy, Michael N. Huhns, Duncan A. Buell

Faculty Publications

We describe how agents are the right building blocks for constructing trustworthy systems. Robust software and trusted autonomy represent the future for agent technology and software engineering.

Weaving A Computing Fabric, Michael N. Huhns, Larry M. Stevens, John W. Keele, Jim E. Wray, Warren M. Snelling, Greg P. Harhay, Randy R. Bradley

Faculty Publications

As sources of information relevant to a particular domain proliferate, we need a methodology for locating, aggregating, relating, fusing, reconciling, and presenting information to users. Interoperability thus must occur not only among the information, but also among the different software applications that process it. Given the large number of potential sources and applications, interoperability becomes an extremely large problem for which manual solutions are impractical. A combination of software agents and ontologies can supply the necessary methodology for interoperability.

Agents As Web Services, Michael N. Huhns

Faculty Publications

Web services are extremely flexible. Most advantageously, a developer of Web services need not know who or what will use the services being provided. The paper discusses current standards for Web services, directory services and the Semantic Web. It considers how agents extend Web services in several important ways.

Robust Software, Michael N. Huhns, Vance T. Holderfield

Faculty Publications

Agents offer a convenient level of granularity at which to add redundancy a key factor in developing robust software. Blindly adding code introduces more errors, makes the system more complex, and renders it harder to understand. However, adding more code can make software better, if it is added in the right way. As this article describes, the key concepts appear to be redundancy and the appropriate granularity.

Agent Societies: Magnitude And Duration, Michael N. Huhns

Faculty Publications

If you only need agents to search the Web for cheap CDs, scalability is not an issue. The Web can support numerous agents if each acts independently. In short order, however, billions of embedded agents that sense their environment and interact with us and other agents will fill our world, making the human environment friendlier and more efficient. These agents will need not only scalable infrastructures and communication services, but also scalable social services encompassing ethics and laws. Research projects are under way around the world to develop and deploy such services. The author takes a look at the critical …

Self-Assembly Of Spatially Separated Silicon Structures By Si Heteroepitaxy On Ni Disilicide, Elena A. Guliants, Chunhai Ji, Wayne A. Anderson

Electrical and Computer Engineering Faculty Publications

A nonlithographic approach to produce self-assembled spatially separated Si structures for nanoelectronic applications was developed, employing the metal-induced silicon growth. Densely packed Si whiskers, 500–800 nm thick and up to 2500 nm long, were obtained by magnetron sputtering of Si on a 25 nm thick Ni prelayer at 575 °C. The nucleation of the NiSi2 compound at the Ni–Si interface followed by the Si heteroepitaxy on the lattice-matched NiSi2 is suggested to be the driving force for the whisker formation.

Designing Human-Centered Distributed Information Systems, Jiagie Zhang, Vimla L. Patel, Kathy A. Johnson, Jane Malin, Jack W. Smith

Faculty, Staff and Student Publications

Many computer systems are designed according to engineering and technology principles and are typically difficult to learn and use. The fields of human-computer interaction, interface design, and human factors have made significant contributions to ease of use and are primarily concerned with the interfaces between systems and users, not with the structures that are often more fundamental for designing truly human-centered systems. The emerging paradigm of human-centered computing (HCC)-which has taken many forms-offers a new look at system design. HCC requires more than merely designing an artificial agent to supplement a human agent. The dynamic interactions in a distributed system …

Femtosecond Laser Utilization Methods And Apparatus And Method For Producing Nanoparticles, Dennis R. Alexander

Department of Electrical and Computer Engineering: Faculty Publications

The present invention teaches various femtosecond machining and drilling apparatus and processes for fabricating tools and the like from both traditional and non-traditional materials. Also described are novel tools such as scalpels, and nozzles fabricated from the apparatus and processes of the present invention. Likewise, the present invention may be utilized in both a novel propulsion system and the production of materials formed from nanometer sized particles and the like.

Making Agents Secure On The Semantic Web, Csilla Farkas, Michael N. Huhns

Faculty Publications

Agents were designed to collaborate and share information. While highly desirable for interoperability, this feature is scary from the security perspective. Illegal inferences, supported by semantic Web technology and ontologies, might enable users to access unauthorized information. In addition to semantic associations and replicated data with different sensitivity, malicious agents could also exploit statistical inferences. Although each agent in a system might behave in a desired and secure way, their combined knowledge could be used to disclose sensitive data. The research community must therefore develop and implement techniques that allow control over released data. To answer the questions related to …

Advances In Space Radiation Shielding Codes, John W. Wilson, Ram K. Tripathi, Garry D. Qualls, Francis A. Cucinotta, Richard E. Prael, John W. Norbury, John H. Heinbockel, John Tweed, Giovanni De Angelis

Mathematics & Statistics Faculty Publications

Early space radiation shield code development relied on Monte Carlo methods and made important contributions to the space program. Monte Carlo methods have resorted to restricted one-dimensional problems leading to imperfect representation of appropriate boundary conditions. Even so, intensive computational requirements resulted and shield evaluation was made near the end of the design process. Resolving shielding issues usually had a negative impact on the design. Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from …

Design And Evaluation Of Processes For Fuel Fabrication, Georg F. Mauer

Fuels Campaign (TRP)

One of the primary concerns in selecting a fuel matrix for actinide-bearing fuels, such as those for transmutation systems, is fuel fabrication. Fuel fabrication technologies for the fabrication and re-fabrication processes must meet several technical considerations, such as minimizing secondary radioactive waste streams, economic viability, reasonable capital outlay, and must be easy to maintain over the transmuter core life cycle. Additionally, the fuel type chosen must be easily manufactured in a remote environment. The volatile behavior of americium during thermal processing further complicates these goals. Currently, the national program is investigating a number of candidate fuel matrices: metallic, ceramic, dispersion, …

New Oscillator Topologies Using Inverting Second-Generation Current Conveyors, Ali̇ Toker, Hakan Kuntman, Oğüzhan Çi̇çekoğlu, Mehmet Di̇şçi̇gi̇l

Turkish Journal of Electrical Engineering and Computer Sciences

In this work, new oscillator topologies based on a recently introduced active element, namely inverting second-generation current conveyor, are presented. This recently introduced unity gain based active element is suitable for integrated circuit realization and can easily be implemented with CMOS technology. Considering this fact, basic oscillator topologies employing a single, two and three conveyors are proposed. Several oscillator circuits based on these topologies are obtained. Expressions for oscillation conditions and frequencies are derived both for ideal and non-ideal cases. Some of them are single frequency and the others are variable frequency oscillators. The oscillators employing two and three active …

A Personel Note, Leopold B. Felsen

Turkish Journal of Electrical Engineering and Computer Sciences

No abstract provided.

Iterative Solution Of Field Problems With A Varying Physical Parameter, Anton G. Tijhuis, Martijn C. Van Beurden, A. Peter M. Zwamborn

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper, linear field problems with a varying physical parameter are solved with the conjugate-gradient FFT method and a dedicated extrapolation procedure for generating the initial estimate. The scheme is formulated and illustrated for two simple example problems. The importance of the choice of the stop criterion and the step size are demonstrated for the case of a straight thin-wire segment. A brief summary is given of the applications that have appeared in the open literature until now, and actual three-dimensional scattering problems for a rectangular conducting plate and an inhomogeneous, dispersive dielectric body are discussed. Finally, the case …

Network--Oriented Modeling Of Radiating Electromagnetic Structures, Peter Russer

Turkish Journal of Electrical Engineering and Computer Sciences

The application of network-oriented modeling for radiating electromagnetic structures is investigated. Network methods are applied to the field problem using the segmentation technique and by specifying canonical Foster representations as compact models of reciprocal linear lossless electromagnetic structures. Connection between different subdomains is obtained via connection circuits exhibiting only ideal transformers. In the case of radiating structures, the complete structure is embedded into a sphere and the field outside the sphere is expanded into orthogonal spherical TM- and TE- waves. For each radiation mode a Cauer canonic circuit representation is given.

Novel Time Domain Radiowave Propagators For Wireless Communication Systems, Funda Akleman, M. O. Özyalçin, Levent Sevgi̇

Turkish Journal of Electrical Engineering and Computer Sciences

In this study, novel time domain wave propagators are used in path loss calculations for macro and micro cell coverage planning in wireless communication systems. Both Transmission Line Matrix (TLM) and Finite-Difference Time-Domain (FDTD) based propagators, which were introduced recently and validated and verified on different canonical propagation scenarios, are used for this purpose. Examples are chosen both in rural and urban areas, where two propagators are compared with each other. Excellent agreement between the results obtained via two propagators is presented. The results presented here are very encouraging and these propagators are shown to be powerful tools for not …

Floquet Wave Diffraction Theory For Tapered Planar Strip Array Green's Function, F. Capolino, F. Mariottini, S. Maci, L. B. Felsen

Turkish Journal of Electrical Engineering and Computer Sciences

This paper deals with the derivation and physical interpretation of a uniform high frequency representation of the Green's function for a planar phased array of dipoles. The asymptotic representation is based on Floquet wave edge diffraction theory herein extended to accommodate slowly varying tapered amplitude illumination with possible inclusion of dipole amplitudes that tend to zero at the edge. The phased array is assumed to be infinite with uniform amplitude excitation in the z-direction but finite and amplitude-tapered in the x-direction. This geometry permits study of diffraction phenomena occurring at the tapered edge of a rectangular array when the observation …

An Exact Line Integral Representation Of The Po Radiation Integral From A Flat Perfectly Conducting Surfaces Illuminated By Elementary Electric Or Magnetic Dipoles, Matteo Albani, Stefano Maci

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper, a line integral representation for the PO radiation integral from a flat perfectly conducting surface, illuminated by an arbitrary oriented elementary either electric or magnetic dipole, is presented. No restriction is imposed on the position of the source and of the observation point. The main application of this result is the acceleration of the numerical PO integration for electrically large surfaces. The formulation is based on the application of the equivalence principle to a projecting surface which allows the analytical evaluation in closed form of one of the two-fold surface integral which define the radiated field at …

Modal Predicates And Coequations, Alexander Kurz, Jiří Rosický

Engineering Faculty Articles and Research

We show how coalgebras can be presented by operations and equations. This is a special case of Linton’s approach to algebras over a general base category X, namely where X is taken as the dual of sets. Since the resulting equations generalise coalgebraic coequations to situations without cofree coalgebras, we call them coequations. We prove a general co-Birkhoff theorem describing covarieties of coalgebras by means of coequations. We argue that the resulting coequational logic generalises modal logic.

A Power Scheduling Software Package For Planetary Habitats, Gary W. Huband

College of Graduate Studies: Theses & Dissertations (1964–2006)

Mankind has established a permanent presence in space with the International Space Station. The next step is building habitats on the Moon or Mars. However, these habitats will have to be nearly self-sustaining because replenishment from Earth will be costly. Power for life support and other electrical devices will be limited and must be monitored and allocated. This thesis develops the framework for power scheduling software to perform these tasks.

The software includes a graphical user interface (GUI) to allow the user to interact with the power schedule, a database and server, and a simulation for the effects of device …

Boundary Effects On Multiplication Noise In Thin Heterostructure Avalanche Photodiodes: Theory And Experiment [Al/Sub 0.6/Ga/Sub 0.4/As/Gaas], Majeed M. Hayat, Oh-Hyun Kwon, Shuling Wang, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

The history-dependent recurrence theory for multiplication noise in avalanche photodiodes (APDs), developed by Hayat et al., is generalized to include inter-layer boundary effects in heterostructure APDs with multilayer multiplication regions. These boundary effects include the initial energy of injected carriers as well as bandgap-transition effects within a multilayer multiplication region. It is shown that the excess noise factor can be significantly reduced if the avalanche process is initiated with an energetic carrier, in which case the initial energy serves to reduce the initial dead space associated with the injected carrier. An excess noise factor reduction up to 40% below the …

Maximum-Likelihood Image Estimation Using Photon-Correlated Beams, Majeed M. Hayat, Muhammad Sajjad Abdullah, Adel Joobeur, Bahaa E.A. Saleh

Electrical and Computer Engineering Faculty Research and Publications

A theory is presented addressing the fundamental limits of image estimation in a setup that uses two photon-correlated beams. These beams have the property that their photon arrivals, as a point process, are ideally synchronized in time and space. The true image represents the spatial distribution of the optical transmittance (or reflectance) of an object. In this setup, one beam is used to probe the image while the other is used as a reference providing additional information on the actual number of photons impinging on the object. This additional information is exploited to reduce the effect of quantum noise associated …

Gain-Bandwidth Characteristics Of Thin Avalanche Photodiodes, Majeed M. Hayat, Oh-Hyun Kwon, Yi Pan, Paul P. Sotirelis, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

The frequency-response characteristics of avalanche photodiodes (APDs) with thin multiplication layers are investigated by means of a recurrence technique that incorporates the history dependence of ionization coefficients. In addition, to characterize the autocorrelation function of the impulse response, new recurrence equations are derived and solved using a parallel computer. The mean frequency response and the gain-bandwidth product are computed and a simple model for the dependence of the gain-bandwidth product on the multiplication-layer width is set forth for GaAs, InP, Al/sub 0.2/Ga/sub 0.8/As, and In/sub 0.52/Al/sub 0.48/As APDs. It is shown that the dead-space effect leads to a reduction (up …

An Algebraic Algorithm For Nonuniformity Correction In Focal-Plane Arrays, Bradley M. Ratliff, Majeed M. Hayat, Russell C. Hardie

Electrical and Computer Engineering Faculty Research and Publications

A scene-based algorithm is developed to compensate for bias nonuniformity in focal-plane arrays. Nonuniformity can be extremely problematic, especially for mid- to far-infrared imaging systems. The technique is based on use of estimates of interframe subpixel shifts in an image sequence, in conjunction with a linear-interpolation model for the motion, to extract information on the bias nonuniformity algebraically. The performance of the proposed algorithm is analyzed by using real infrared and simulated data. One advantage of this technique is its simplicity; it requires relatively few frames to generate an effective correction matrix, thereby permitting the execution of frequent on-the-fly nonuniformity …

Object Persistence And Availability In Digital Libraries, Michael L. Nelson, B. Danette Allen

Computer Science Faculty Publications

We have studied object persistence and availability of 1,000 digital library (DL) objects. Twenty World Wide Web accessible DLs were chosen and from each DL, 50 objects were chosen at random. A script checked the availability of each object three times a week for just over 1 year for a total of 161 data samples. During this time span, we found 31 objects (3% of the total) that appear to no longer be available: 24 from PubMed Central, 5 from IDEAS, 1 from CogPrints, and 1 from ETD.

A Scalable Architecture For Harvest-Based Digital Libraries, Xiaoming Liu, Tim Brody, Stevan Harnard, Les Carr, Kurt Maly, Mohammad Zubair, Michael L. Nelson

Computer Science Faculty Publications

This article discusses the requirements of current and emerging applications based on the Open Archives Initiative (OAI) and emphasizes the need for a common infrastructure to support them. Inspired by HTTP proxy, cache, gateway and web service concepts, a design for a scalable and reliable infrastructure that aims at satisfying these requirements is presented. Moreover, it is shown how various applications can exploit the services included in the proposed infrastructure. The article concludes by discussing the current status of several prototype implementations.

Federated Searching Interface Techniques For Heterogeneous Oai Repositories, Xiaoming Liu, Kurt Maly, Mohammad Zubair, Qiaoling Hong, Michael L. Nelson, Frances Knudson, Irma Holtkamp

Computer Science Faculty Publications

Federating repositories by harvesting heterogeneous collections with varying degrees of metadata richness poses a number of challenging issues: (1) how to address the lack of uniform control for various metadata fields in terms of building a rich unified search interface, and (2) how easily new collections and freshly harvested data in existing repositories can be incorporated into the federation supporting a unified interface? This paper focuses on the approaches taken to address these issues in Arc, an Open Archives Initiative compliant federated digital library. At present Arc contains over 1M metadata records from 75 data providers from various subject domains. …

An Exploratory Study Of Internet Data Centres In Malaysia, Huai Peng Loh, Siew Hwa Tan

Student Works (2000-2009)

The explosion of Internet in Malaysia has spurred the growth of Internet Data Centres - a combination of Internet Service Providers, Information Technology Vendor Community and Telecommunication Service Providers providing co­location and managed services. These Internet Data Centres are targeting any organisations which have an internet strategy and which plan to outsource their IT infrastructures. This report aims to shed a light on the Malaysian Internet Data Centres, which are mainly concentrated in the Klang Valley. Readers will be able to gain insight into the target markets, infrastructure owned and services offered by the Internet Data Centres concerned. The report …