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Articles 170701 - 170730 of 198032

Full-Text Articles in Engineering

Practical Hints For The Layout And Construction Of 10,000 M3 Circular Dams, Terry Babbington, J S. Addison Jan 1999

Practical Hints For The Layout And Construction Of 10,000 M3 Circular Dams, Terry Babbington, J S. Addison

Bulletins 4000 -

These notes and illustrations have been compiled to assist earthmovers in the construction of circular excavated earth tank dams, with pipe inlets. Construction techniques tend to evolve over time, so the methods described in this publication will not be definitive, but, they may improve efficiency of construction in the interim. Although the example used in these notes refers to 10,000 m3 dams, the construction techniques, using a bulldozer, described here equally apply to dams of any volume of similar design. Only dimensions will vary. earthmovers using a scarper together with a bulldozer should be able to extract useful information from …

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Analysis Of Ductile To Cleavage Transition In Part-Through Cracks Using The Cell Model Incorporating Statistics, Xiaosheng Gao, J. Faleskog, C. Fong Shih Jan 1999

Analysis Of Ductile To Cleavage Transition In Part-Through Cracks Using The Cell Model Incorporating Statistics, Xiaosheng Gao, J. Faleskog, C. Fong Shih

Mechanical Engineering Faculty Research

This paper describes an approach to study ductile/cleavage transition in ferritic steels using the methodology of a cell model for ductile tearing incorporating weakest link statistics. The model takes into account the constraint effects and puts no restriction on the extent of plastic deformation or amount of ductile tearing preceding cleavage failure. The parameters associated with the statistical model are calibrated using experimental cleavage fracture toughness data, and the effect of threshold stress on predicted cleavage fracture probability is investigated. The issue of two approaches to compute Weibull stress, the ‘history approach’ and the ‘current approach’, is also addressed. The …

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Emerald: A Low Cost Spacecraft Mission For Validating Formation Flying Technologies, Robert J. Twiggs, Jonathan How, Freddy Pranajaya, Bryan Palmintier Jan 1999

Emerald: A Low Cost Spacecraft Mission For Validating Formation Flying Technologies, Robert J. Twiggs, Jonathan How, Freddy Pranajaya, Bryan Palmintier

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs, Robert Twiggs, Jonathon How, Freddy Pranajaya, and Bryan Palmintier titled "EMERALD: A Low Cost Spacecraft Mission for Validating Formation Flying Technologies" from 1999.

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The Role Of Surface Roughness For Implant Incorporation In Bone, A. Wennerberg Jan 1999

The Role Of Surface Roughness For Implant Incorporation In Bone, A. Wennerberg

Cells and Materials

A careful topographical characterization is important for reliable interpretation of the role of implant surface roughness in bone incorporation. In this paper, the currently available measuring instruments and evaluation techniques are described and discussed first, than literature on the role of surface roughness for cell and bone tissue reactions in vitro and, with special emphasis, the in vivo studies are reviewed. Finally, the results from a series of the authors own animal studies evaluating screw-shaped implants with different surface roughnesses are summarized. The results demonstrated firmer bone fixation for blasted implants than for turned ones. A blasted surface with an …

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Wax Yield Of Grain Sorghum (Sorghum Bicolor) As Affected By Mechanical Harvesting, Threshing, And Handling Methods, K. R. Lochte-Watson, Curtis L. Weller Jan 1999

Wax Yield Of Grain Sorghum (Sorghum Bicolor) As Affected By Mechanical Harvesting, Threshing, And Handling Methods, K. R. Lochte-Watson, Curtis L. Weller

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Wax is found on the outer layer of the grain sorghum (Sorghum bicolor) kernel. Current harvesting and handling techniques cause abrasion and breakage, thereby potentially reducing wax yield from sorghum kernels. The purpose of this study was to determine wax yield of sorghum after mechanical harvesting and handling and to compare wax yield of whole and broken sorghum kernels. Combine threshing and auger conveying of grain caused abrasion and breakage, which reduced the wax yield by 5%. The monitored process in this experiment included a cleaning system which reduced the amount of broken kernels and sorghum particles, increasing …

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Belts Vs Tires, Belts Vs Belts, Tires Vs Tires, Leonard L. Bashford, Michael F. Kocher Jan 1999

Belts Vs Tires, Belts Vs Belts, Tires Vs Tires, Leonard L. Bashford, Michael F. Kocher

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Tractive performance comparisons among two different width rubber belt tracks, 46 cm (18 in.) and 81 cm (32 in.) wide, and two different size rear tires, 710/70R38 and 18.4R46, were made on two different surface conditions. The belts were tested on a Caterpillar 55 tractor equipped with the Mobil-trac™ system and the tires on a John Deere 8400 mechanical front-wheel-drive (MFWD) tractor. The performance tests were completed on two surfaces, one being a non-tilled wheat stubble field and the second, the wheat stubble field tilled approximately 23 cm (9 in.) deep with a Noble blade sweep. Performance comparisons using tractive …

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Seepage Characteristics And Hydraulic Properties Of A Feedlot Runoff Storage Pond, David B. Parker, Dean E. Eisenhauer, Dennis D. Schulte, John A. Nienaber Jan 1999

Seepage Characteristics And Hydraulic Properties Of A Feedlot Runoff Storage Pond, David B. Parker, Dean E. Eisenhauer, Dennis D. Schulte, John A. Nienaber

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Water and chemical transport were investigated beneath a 22-year-old beef feedlot runoff storage pond. Soil and sludge samples were collected from 14 borings to 6.1-m depths in a cross-section across the pond. The soils consisted of silt loam and clay loam, and the groundwater level was about 30 m beneath the land surface. Soil samples were analyzed for pH, NO3-N, NH4-N, Cl, P, K, SO4-S, TKN, and organic matter. Physical and hydraulic properties were measured on undisturbed samples of soil and sludge to compare saturated hydraulic conductivity, moisture release characteristics, and bulk density. Saturated …

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Model Updating By Adding Known Masses And Stiffnesses, Philip D. Cha, Lisette G. De Pillis Jan 1999

Model Updating By Adding Known Masses And Stiffnesses, Philip D. Cha, Lisette G. De Pillis

All HMC Faculty Publications and Research

New approaches are developed to update the analytical mass and stiffness matrices of a system. By adding known masses to the structure of interest, measuring the modes of vibration of this mass-modified system, and finally using this set of new data in conjunction with the initial modal survey, the mass matrix of the structure can be corrected. A similar approach can also be used to update the stiffness matrix of the system by attaching known stiffnesses. Manipulating the mass and stiffness correction matrices into vector forms, the connectivity information can be enforced, thereby preserving the physical configuration of the system, …

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The First Full-Scale Accelerated Pavement Test In Louisiana: Development And Findings, J.B. Metcalf, Stefan Romanoschi, Y. Li, M. Rasoulian Jan 1999

The First Full-Scale Accelerated Pavement Test In Louisiana: Development And Findings, J.B. Metcalf, Stefan Romanoschi, Y. Li, M. Rasoulian

Civil Engineering Faculty Publications - Archive

The Pavement Research Facility in Port Allen, Louisiana houses the first full-scale accelerated pavement testing experiment in the state. The purpose of the first experiment was to evaluate the historically prevalent flexible crushed stone and in-place soil cement stabilized base construction in comparison to several alternative base construction materials and construction processes for pavements designed for a semi-tropical climate. Loading is provided by an Accelerated Loading Facility (ALF) machine, the second of its type in the United States. More than six million equivalent axle loads (ESALs) were applied to the nine test lanes. Performance of the pavement structures and materials …

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Design Considerations And Thermodynamic Feasibility Study Of A Meso-Scale Refrigerator, Nabil Shovon Ashraf Jan 1999

Design Considerations And Thermodynamic Feasibility Study Of A Meso-Scale Refrigerator, Nabil Shovon Ashraf

Retrospective Theses and Dissertations

Recent advances in micro-fabrication technology have ushered a new era in miniaturization of chemical, environmental and energy systems. This foreseeable trend towards miniaturization in chemical, environmental and mechanical systems is expected to revolutionize the ways the human life is being perceived today. The high volume and mass reproducibility is seen as the striking aspect of micro-fabrication based miniature systems, offering economies far exceeding than the economies of scale obtained in large plants. The focus of this thesis work is directed at the thermodynamic feasibility and preliminary prototype design for a meso-scale refrigerator. Miniaturization to sub-centimeter domain will enable configuring these …

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Unbound Pavement Base Courses: Parallel Study Of Stiffness And Drainage Characteristics, Moussa Issa Jan 1999

Unbound Pavement Base Courses: Parallel Study Of Stiffness And Drainage Characteristics, Moussa Issa

Doctoral Dissertations

The purpose of this project was to study the effects of fines (minus #4 sieve) on permeability and stiffness characteristics of unbound base materials and to propose an optimumgradation that will satisfy these two parameters. One type of highway base material--crushed limestone--was used in the study. A total of 75 laboratory tests were conducted and distributed--25 respectively on permeability, resilient modulus and unconfined compression. The permeability test data were collected using a low-head permeameter. The resilient modulus and unconfined compression test data were collected by the mean of the MTS (Machine Testing System) with a load cell capacity of 22-kips. …

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Transition Criteria - From A Pit To A Crack, Tarun Goswami, David W. Hoeppner Jan 1999

Transition Criteria - From A Pit To A Crack, Tarun Goswami, David W. Hoeppner

Biomedical, Industrial & Human Factors Engineering Faculty Publications

A brief review of pitting, which is a localized corrosion process resulting from pitting and fatigue interaction has been conducted in this paper. The transition of a pit to a crack is a very important phenomenon occurring under PCF conditions. Various theories for transition of a pit to a crack were examined within the limits of present understanding and limitations of the models. The transition of a pit to a crack was also discussed for a variety of pit shapes utilizing the pit aspect ratios, defect size and linear elastic fracture mechanics, crack tip characterizing parameters such as Mode I …

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An Algorithm For Optimal Winner Determination In Combinatorial Auctions, Tuomas Sandholm Jan 1999

An Algorithm For Optimal Winner Determination In Combinatorial Auctions, Tuomas Sandholm

All Computer Science and Engineering Research

Combinatorial auctions, i.e. auctions where bidders can bid on combinations of items, tend to lead to more efficient allocations than traditional auctions in multi-item auctions where the agents' valuations of the items are not additive. However, determining the winners so as to maximize revenue is NP-complete. First, existing approaches for tackling this problem are reviewed: exhaustive enumeration, dynamic programming, approximation algorithms, and restricting the alloable combinations. Then we present our search algorithm for optimal winner determination. Experiments are shown on several bid distributions. The algorithm allows combinatorial auctions to scale up to significantly larger numbers of items and bids than …

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Emediator: A Next Generation Electronic Commerce Server, Tuomas Sandholm Jan 1999

Emediator: A Next Generation Electronic Commerce Server, Tuomas Sandholm

All Computer Science and Engineering Research

This paper presents eMediator, a next generation electronic commerce server that demonstrates some ways in which AI, algorithmic support, and game theoretic incentive engineering can jointly improve the efficiency of ecommerce. First, its configurable auction house includes a variety of generalized combinatorial auctions, price setting mechanism, novel bid types, mobile agents, and user support for choosing an auction type. Second, its leveled commitment contract optimizer determines the optimal contract price and decommitting penalties for a variety of leveled commitment contracting protocols, taking into account that rational agents will decommit insincerely in taking into account that rational agents will decommit insincerely …

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Revenue Equivalence Of Leveled Commitment Contracts, Tuomas Sandholm, Yunhong Zhou Jan 1999

Revenue Equivalence Of Leveled Commitment Contracts, Tuomas Sandholm, Yunhong Zhou

All Computer Science and Engineering Research

In automated negotiation systems consisting of self-interested agents, contracts have traditionally been binding. Leveled commitment contracts - i.e. contracts where each party can decommit by paying a predetermined penalty - were recently shown to improve expected social welfare even if agents decommit insincerely in Nash equilibrium. Such contracts differ based on whether agents have to declare their decommitting decisions sequentially or simultaneously, and whether or not agents have to pay the penalties if both decommit. For a given contract, these protocols lead to different decommitting thresholds and probabilities. However, this paper shows that, surprisingly, each protocol leads to the same …

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Auctions Without Common Knowledge, Sviatoslav B. Brainov, Tuomas W. Sandholm Jan 1999

Auctions Without Common Knowledge, Sviatoslav B. Brainov, Tuomas W. Sandholm

All Computer Science and Engineering Research

This paper proves that the revenue equivalence theorem ceases to hold for auctions without common knowledge about the agents' prior beliefs. That is, different auction forms yield different expected revenue. To prove this, an auction game is converted to a Bayesian decision problem with an infinite hierarchy of beliefs. A general solution for such Bayesian decision problems is proposed. The solution is a generalization of the standard Bayesian solution and coincides with it for finite belief trees and for trees representing common knowledge. It is shown how the solution generalizes the frequently used technique of backward induction for infinite belief …

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A Fine-Grained Model For Code Mobility, Cecilia Mascolo, Gian Pietro Picco, Gruia-Catalin Roman Jan 1999

A Fine-Grained Model For Code Mobility, Cecilia Mascolo, Gian Pietro Picco, Gruia-Catalin Roman

All Computer Science and Engineering Research

In this paper, we take the extreme view that every line of code is potentially mobile, i.e., may be duplicated and/or moved from one program context to another on the same host or across the network. Our motivation is to gain a better understanding of the range of constructs and issues facing the designer of a mobile code system, in a setting that is abstract and unconstrained by compilation and performance considerations traditionally associated with programming language design. Incidental to our study is an evaluatoin of the expressive power of Mobile UNITY, a notation and proof logic for mobile computing.

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Pattern Matching Techniques And Their Applications To Computational Molecular Biology - A Review, Eric C. Rouchka Jan 1999

Pattern Matching Techniques And Their Applications To Computational Molecular Biology - A Review, Eric C. Rouchka

All Computer Science and Engineering Research

Pattern matching techniques have been useful in solving many problems associated with computer science, including data compression (Chrochemore and Lecroq, 1996), data encryption (RSA Laboratories, 1993), and computer vision (Grimson and Huttenlocher, 1990). In recent years, developments in molecular biology have led to large scale sequencing of genomic DNA. Since this data is being produced in such rapid fasion, tools to analyze DNA segments are desired. The goal here is to discuss various techniques and tools for solving various pattern matching questions in computational biology, including optimal sequence alignment, multiple sequence alignment, and buidling models to describe sequence families using …

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Assembly And Analysis Of Extended Human Genomic Contig Regions, Eric C. Rouchka, David J. States Jan 1999

Assembly And Analysis Of Extended Human Genomic Contig Regions, Eric C. Rouchka, David J. States

All Computer Science and Engineering Research

The Human Genome Project (HGP) has led to the deposit of human genomic sequence in the form of sequenced clones into various databases such as the DNA Data Bank of Japan (DDBJ) (Tateno and Gojobori, 1997), the European Molecular Biology Laboratory (EMBL) Nucleotide Sequence Database (Stoesser, et. al., 1999), and GenBank (Benson, et. al., 1998). Many of these sequenced clones occur in regions where sequencing has taken place either within the same sequencing center or other centers throughout the world. The assembly of extended segments of genomic sequence by looking at overlapping end segments is desired and is currently availabel …

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The Design And Performance Of A Pluggable Protocols Framework For Object Request Broker Middleware, Fred Kuhns, Carlos O'Ryan, Douglas C. Schmidt, Jeff Parsons Jan 1999

The Design And Performance Of A Pluggable Protocols Framework For Object Request Broker Middleware, Fred Kuhns, Carlos O'Ryan, Douglas C. Schmidt, Jeff Parsons

All Computer Science and Engineering Research

To be an effective platform for performance-sensitive real-time and embedded applications, off-the-shelf OO middleware like CORBA, DCOM, and Java RMI must preserve communication-layer quality of service (QoS) properties to applications end-to-end. However, conventional OO middleware interoperability protocols, such as CORBA's GIOP/IIOP or DCOM's MS-RPC, are not well suited for applications that cannot tolerate the message footprint size, latency, and jitter associated with general-purpose messaging and transport protocols. It is essential, therefore, to develop standard plugable protocols frameworks that allow custom messaging and transport protocols to be configured flexibly and used transparently by applications. This paper provides three contributions to research …

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A Rapid Development Of Dependable Applications In Ad Hoc Mobility, Amy L. Murphy Jan 1999

A Rapid Development Of Dependable Applications In Ad Hoc Mobility, Amy L. Murphy

All Computer Science and Engineering Research

Advances in wireless communication and network computing technologies make possible new kinds of applications involving transient interactions among physical components that move across a wide range of spaces, from the confines of a room to the airspace across an ocean, and require no fixed networking infrastructure to communicate with one another. Such components may come together to form ad hoc networks for the purpose of exchanging information or in order to engage in cooperative task-oriented behaviors. Ad hoc networks are assembled, reshaped and taken apart as components move in and out of communication range; all interactions are transient; computations become …

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Terabit Burst Switching Progress Report (12/98-6-99), Jonathan S. Turner Jan 1999

Terabit Burst Switching Progress Report (12/98-6-99), Jonathan S. Turner

All Computer Science and Engineering Research

This report summarizes progress on Washington University's Terabit Burst Switching Project, supported by DARPA and Rome Air Force Laboratory. This project seeks to demonstrate the feasibility of Burst Switching, a new data communication service which can more effectively exploit the large bandwidths becoming available in WDM transmission systems, than conventional communication technologies like ATM and IP-based packet switching. Burst switching systems dynamically assign data bursts to channels in optical data links, using routing information carried in parallel control channels. The project will lead to the construction of a demonstration switch with throughput exceeding 200 Gb/s and scalable to over 10 …

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Algorithms For Optimizing Leveled Commitment Contracts, Thomas Sandholm, Sandeep Sikka, Samphel Norden Jan 1999

Algorithms For Optimizing Leveled Commitment Contracts, Thomas Sandholm, Sandeep Sikka, Samphel Norden

All Computer Science and Engineering Research

In automated negotiation systems consisting of self-interested agents, contracts have traditionally been binding. Leveled commitment contracts - i.e. contracts where each party can decommit by paying a predetermined penalty - were recently shown to improve Pareto efficiency even if agents rationally decommit in Nash equilibrium using inflated thresholds on how good their outside offers must be before they decommit. This paper operationalizes the four leveled commitment contracting protocols by presenting algorithms for using them. Algorithms are presented for computing the Nash equilibrium decomitting thresholds and decommitting probabilities given the contract price and the penalties. Existence and uniqueness of the equilibrium …

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Floor Control Protocol For Alx Video Conference Application, Ruibiao Qiu Jan 1999

Floor Control Protocol For Alx Video Conference Application, Ruibiao Qiu

All Computer Science and Engineering Research

With wide deployment of high-speed networks such as vBNS today, video-conference applications over WANs have become increasingly feasible. MMX has proven to be a good desktop video-conference devide for local ATM networks. Now, ALX has been designed to extend MMX's video conferencing capability to IP-over-ATM WANs such as vBNS. In this report, we discuss a floor control protocol for ALX video-conference applications. We first show how an "ideal" protocol should behave to meet our requirements. Then we compare three protocols based on distributed algorithms, and a protocol based on a centralized algorithm. Based on the comparison and performance analysis, we …

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Reliable Communication For Highly Mobile Agents, Amy L. Murphy, Gian Pietro Picco Jan 1999

Reliable Communication For Highly Mobile Agents, Amy L. Murphy, Gian Pietro Picco

All Computer Science and Engineering Research

The provision of a reliable communication infrastructure for mobile agents is still an open research issue. The challenge to reliability we address in this work does not come from the possibility of faults, but rather from the mere presence of mobility, which slightly complicates the problem of ensuring the delivery of information even in a fault-free network. For instance, the asynchronous nature of message passing and agent migration may cause situations where messages forever chase a mobile agent that moves frequently from one host to another. Current solutions rely on conventional technologies that either do not provide a solution for …

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Optimal Flow Aggregation, Subhash Suri, Tuomas Sandholm, Priyank Warkhede Jan 1999

Optimal Flow Aggregation, Subhash Suri, Tuomas Sandholm, Priyank Warkhede

All Computer Science and Engineering Research

Current IP routers are stateless: they forward individual packets based on the destination address contained in the packet header, but maintain no information about the application or flow to which a packet belongs. This stateless service model works well for best effort datagram delivery, but is grossly inadequate for applications that require quality of service guarantees, such as audio, video, or IP telephony. Maintaining state for each flow is expensive because the number of concurrent flows at a router can be in the hundreds of thousands. Thus, stateful solutions such as Intserv (integrated services) have not been adopted for their …

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Multiway Range Trees: Scalable Ip Lookup With Fast Updates, Subhash Suri, George Varghese, Piryank Ramesh Warkhede Jan 1999

Multiway Range Trees: Scalable Ip Lookup With Fast Updates, Subhash Suri, George Varghese, Piryank Ramesh Warkhede

All Computer Science and Engineering Research

Internet routers forward packets based on the destination address of a packet. A packet's address is matched against the destination prefixes stored in the router's forwarding table, and the packet is sent to the output interface determined by the longest matching prefix. While some existing schemes work well for IPv4 addresses, we believe that none of the current schemes scales well to IPv6, especially when fast updates are required. As the Internet evolves into a global communication medium, requiring multiple addresses per user, the switch to longer addresses (e.g. IPv6) seems inevitable despite temporary measures such as network addres translation …

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Bargaining With Deadlines, Tuomas Sandholm, Nir Vulkan Jan 1999

Bargaining With Deadlines, Tuomas Sandholm, Nir Vulkan

All Computer Science and Engineering Research

This paper analyzes automated distributive negotiation where agents have firm deadlines that are private information. The agents are allowed to make and accept offers in any order in continuous time. We show that the only sequential equilibrum outcome is the one where the agents wait until the first deadline, at which point that agent concedes everything to the other. This holds for pure and mixed strategies. So, interestingly, rational agents can never agree to a nontrivial split because offers signal enough weakness of bargaining power (early deadline) so that the recipient should never accept. Similarly, the offerer knows that it …

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Tracking Mobile Units For Dependable Message Delivery, Amy L. Murphy, Gruia-Catalin Roman, George Varghese Jan 1999

Tracking Mobile Units For Dependable Message Delivery, 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. An approach to this is to have a single home node constantly track the current location of the mobile unit and forward messages to this location. One problem with this approach is that during the update to the home agent after movement, messages are often dropped, especially in the case of frequent …

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A Proposal For A High-Performance Active Hardware Architecture, Tilman Wolf Jan 1999

A Proposal For A High-Performance Active Hardware Architecture, Tilman Wolf

All Computer Science and Engineering Research

Current research in Active Networking is focused on developing software architectures and defining funtionality of Execution Environments. While active network systems show superior functionality compared to traditional networks, they only operate at substantially lower link speeds. To increase the acceptance of Active Network in environments where link speeds of several Gb/s are common, we propose a hardware architecture that performs high-speed packet handling while providing the same flexibility as a common software system. The design exploits the independence between data streams for parallel processing. To measure the impact of different design decisions on the performance of the system, we also …

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