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Articles 67231 - 67260 of 75094

Full-Text Articles in Engineering

Doctor Of Science In Computer Information Systems, Nova Southeastern University Jan 1992

Doctor Of Science In Computer Information Systems, Nova Southeastern University

College of Engineering and Computing Course Catalogs

No abstract provided.

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Unequal Error Protection Qpsk Modulation Codes, Robert H. Morelos-Zaragoza, Shu Lin Jan 1992

Unequal Error Protection Qpsk Modulation Codes, Robert H. Morelos-Zaragoza, Shu Lin

Faculty Publications

The authors use binary linear UEP (LUEP) codes, in combination with a QPSK signal set and Gray mapping, to obtain new efficient block QPSK modulation codes with unequal minimum squared Euclidean distances. They give several examples of codes that have the same minimum squared Euclidean distance as the best QPSK modulation codes of the same rate and length. A new suboptimal two-stage soft-decision decoding is applied to LUEP QPSK modulation codes.

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Photonics In Switching, Harvard S. Hinton Jan 1992

Photonics In Switching, Harvard S. Hinton

Electrical and Computer Engineering Faculty Publications

One of the keys to the future of telecommunications companies will be their ability to provide new broadband services to both the business community and residential customers. With the new services will come the need for the equivalent of a broadband switching office. Such a system could require the capability of supporting in excess of 10000 users with broadband channel bit rates exceeding 100 Mb/s. This implies a switching fabric the aggregate bit rate of which could be greater than 1 Tb/s. Guided-wave technology and free-space technology switching fabrics are discussed. Three time-division-based switching fabrics are proposed, and two wavelength-division-based …

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Switching To Photonics, Harvard S. Hinton Jan 1992

Switching To Photonics, Harvard S. Hinton

Electrical and Computer Engineering Faculty Publications

The use of hardware that exploits the interplay of photons and electrons to switch voice, data, and video is discussed. The two directions being taken by current research-guided-wave and free-space photonics-are examined. Photonic time-slot interchanges are described. Multidivisional fabrics, based on a combination of space-division and time-division multiplexing, are considered, as is the wavelength-division-based photonic packet switch, another kind of multidimensional fabric. The use of self-electrooptic effect devices, (SEEDs) is discussed.

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All-Optical Synchronisation And Multiplication Of The Frequency Of Mode-Locked Signals, P. Phelan, Gerald Farrell, Joe Hegarty Jan 1992

All-Optical Synchronisation And Multiplication Of The Frequency Of Mode-Locked Signals, P. Phelan, Gerald Farrell, Joe Hegarty

Articles

We report all-optical synchronized multiplication by rational fractions of the modulation frequency of optical signals in self-pulsing two-section semiconductor laser diodes. The effect is based on the overlap of harmonics of the input signal with harmonics of the self-pulsation. We illustrate this new generic function with modelocked inputs rich in harmonics were fractions of 1,2, and 3 / 2 are generated, and we identify a number of applications for this effect.

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Three-Dimensional Incompressible Flow Calculations With Maccormack's Method, Robert S. Bernard, Michael L. Schneider Jan 1992

Three-Dimensional Incompressible Flow Calculations With Maccormack's Method, Robert S. Bernard, Michael L. Schneider

United States Army: Publications

MAC3D is a finite-volume computer code that uses MacCormack's method to calculate three-dimensional incompressible flow on staggered Marker-and-Cell grids. The code accepts nonuniform, nonorthogonal grids for any curvilinear domain that can be mapped onto a single rectangular block. It is applicable for free-surface flow at low Froude number, and for confined flow in general. Computed results from MAC3D are presented for laminar flow in channels with internal obstacles and curved boundaries.

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Improved Thermal Predictions In Ce-Qual-W2, Raymond S. Chapman, Thomas M. Cole Jan 1992

Improved Thermal Predictions In Ce-Qual-W2, Raymond S. Chapman, Thomas M. Cole

United States Army: Publications

Recent modifications to the transport scheme within the two-dimensional hydrodynamic and water quality model CEQUAL- W2 have resulted in a significant improvement in the prediction of temperature distributions by reducing numerical diffusion. These changes allow for a more accurate description of wind effects in the model. This paper briefly describes the modifications to CE-QUAL-W2 and presents results of two simulations both with and without the improvements to the transport algorithm.

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Release Alternatives On A 3-D Salinity Simulation, Bernard B. Hsieh Jan 1992

Release Alternatives On A 3-D Salinity Simulation, Bernard B. Hsieh

United States Army: Publications

Hydraulic structures such as darns, locks or diversion gates, in the upstream or tributary of an estuary system can control necessary freshwater discharge to meet downstream water quality standards. One of the most significant purposes of these structures is maintaining target salinity to satisfy the environment concerns, such as fishery spawning in the high-flow season and drinking water criteria in the low-flow period. In order to evaluate possible alternative regulations for the reservoir operation, a reliable three-dimensional (3-D) hydrodynamic model is required as a management tool to simulate the impact of salinity variations due to release policy changes. This paper …

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Gas Transfer In Diffused Bubble Plumes, Steven C. Wilhelms, Sandra K. Martin Jan 1992

Gas Transfer In Diffused Bubble Plumes, Steven C. Wilhelms, Sandra K. Martin

United States Army: Publications

The gas transfer in aeration systems is broken into two processes: gas transfer at the bubble interface and gas transfer at the water surface. Experiments were conducted to separate these two sources of dissolved gas. Oxygen absorption was measured in a laboratory tank with air being diffused through a porous diffuser and then with nitrogen gas being diffused. The combination of these experiments along with reformulation of the theoretical transfer equation permit separation of the gas transfer at the water surface and in the rising bubble plume. Estimates of the exchange coefficient for the plume and surface are given.

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Hydraulic Structures Versus Zebra Mussels, John J. Ingram, Andrew C. Miller Jan 1992

Hydraulic Structures Versus Zebra Mussels, John J. Ingram, Andrew C. Miller

United States Army: Publications

The United States Army Corps of Engineers (USAE) has begun a four-year research program to develop environmentally sound control strategies for zebra mussel (Dreissena polymorpha) infestations at public facilities. The USAE Waterways Experiment Station has initiated research for these facilities which include water-intake structures, navigation locks, gated dams, outlet works, pumping plants, hydropower plants, drainage structures, dredges and commercial vessels.

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Computation Of Long-Term Three-Dimensional Hydrodynamics Of New York Bight, Keu W. Kim, David J. Mark, Norman W. Scheffner, Lynn M. Bocamazo Jan 1992

Computation Of Long-Term Three-Dimensional Hydrodynamics Of New York Bight, Keu W. Kim, David J. Mark, Norman W. Scheffner, Lynn M. Bocamazo

United States Army: Publications

A time-varying three-dimensional (3D) numerical hydrodynamic model has been applied to the New York Bight to provide flow fields to a 3D water quality model. The spatial computational domain extends from Cape May, New Jersey at its south-west end and Narragansett Bay, Rhode Island, at the north-east end and seaward to the shelf-break. As illustrated below, the numerical model has more than 2500 active horizontal cells and ten vertical layers. Features of the hydrodynamic model include coupling of temperature grids to better represent geometric features, and an algebraic vertical turbulence model based upon the assumption that turbulence production and dissipation …

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Stable Channel And Environmental Design Considerations For An Urban Flood Control Project, Edward F. Sing, Daniel Pridal, Thea Lane Jan 1992

Stable Channel And Environmental Design Considerations For An Urban Flood Control Project, Edward F. Sing, Daniel Pridal, Thea Lane

United States Army: Publications

A case study will be presented of a two phase process of development of the hydraulic design of a flood control project incorporating a creek nestled within an urban greenbelt. The green belt reach consists of the existing, 5 to 15 foot wide tree-lined, low flow channel set within an approximate 100 to 150 foot wide floodway to be created by low berms. Any project features proposed for this reach would need to be environmentally and aesthetically acceptable. The design approach taken in developing the flood control and channel stabilization plan for the greenbelt reach will be presented. This approach …

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Rapid Detection Of Hydrocarbon Contamination In Ground Water And Soil, A. M. Chrestman, G. D. Comes, S. S. Kooper, P. G. Malone Jan 1992

Rapid Detection Of Hydrocarbon Contamination In Ground Water And Soil, A. M. Chrestman, G. D. Comes, S. S. Kooper, P. G. Malone

United States Army: Publications

In situ fluorometry is being developed as a method for rapidly detecting and quantifying hydrocarbon contamination in ground water and soil. The results of a fluorometry survey over a site having known fuel contamination are compared to results from a soil gas survey over the same site. The fluorometry data showed three additional contaminated areas that were not detected by soil gas measurements. Soil analyses confirmed the presence of the contaminated areas.

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Using A Numerical Model To Evaluate Dredging Options, Ronald R. Copeland Jan 1992

Using A Numerical Model To Evaluate Dredging Options, Ronald R. Copeland

United States Army: Publications

A study was conducted to address a shoaling problem in the vicinity of the Cubits Gap distributary on the lower Mississippi River. Upstream from Cubits Gap the river is relatively deep, but the channel depth decreases as it approaches the distributary, where frequent dredging is required. A one-dimensional numerical model was used to evaluate alternative dredging operations and to forecast sediment accumulation. The numerical model was also used to forecast sediment accumulation based on 30-day flow projections. This information can be used to help determine when to initiate dredging fleet mobilization.

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Environmental Engineering Options For Managing Contaminated Sediment, Norman R. Francingues. Jr. Jan 1992

Environmental Engineering Options For Managing Contaminated Sediment, Norman R. Francingues. Jr.

United States Army: Publications

Technologies that have been identified as feasible for remediating contaminated sediment and are peing considered for demonstration in the Great Lakes are presented in this paper. This review is limited to the components and technologies required for removal and management of highly contaminated sediment. Over two hundred technology process options were reviewed for effectiveness, implementability and costs. However, few of these processes have actually been applied to contaminated sediment on a full scale. Most of the technology evaluations have been conducted at the bench scale with limited data available for pilot scale assessment. Therefore, further testing and evaluation of the …

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In-Channel Sediment Basins: An Alternative To Dam-Style Debris Basins, Wendy S. Gist, Scott E. Stonestreet, Ronald R. Copeland Jan 1992

In-Channel Sediment Basins: An Alternative To Dam-Style Debris Basins, Wendy S. Gist, Scott E. Stonestreet, Ronald R. Copeland

United States Army: Publications

In-channel sediment basins were designed, in lieu of a traditional debris basin, to capture large sediment loads at the upstream end of a proposed flood control channel. A numerical model, HEC-6, was used to size the basins.

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Numerical Modeling Of Reservoir Tailrace Hydraulics For Water Quality And Habitat Analysis, Brad R. Hall, John Nestler Jan 1992

Numerical Modeling Of Reservoir Tailrace Hydraulics For Water Quality And Habitat Analysis, Brad R. Hall, John Nestler

United States Army: Publications

The Waterways Experiment Station has developed dynamic numerical hydraulic and water quality simulation models of the Missouri River reaches downstream of Fort Peck, Garrison, and Fort Randall Dams in support of Master Water Control Manual studies. The numerical modeling approach is to compute spatial and temporal variations in stage and discharge in each of these reaches using UNET, a one-dimensional dynamic flow model. Hydraulic and geometric parameters calculated by UNET are then linked with transport algorithms in the CE-QUAL-RIV1 numerical model for computing spatial and temporal variation in water temperature and dissolved oxygen in each of the modeled reaches. Parameters …

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Development Of A Comprehensive Modeling System For Remediation Of Contaminated Groundwater, Jeffrey P. Holland Jan 1992

Development Of A Comprehensive Modeling System For Remediation Of Contaminated Groundwater, Jeffrey P. Holland

United States Army: Publications

The U.S. Army Engineer Waterways Experiment Station (WES) has proposed development of a Groundwater Modeling System (GMS) for simulating groundwater flow, the transport/fate of subsurface contaminants, and the efficacy of remedial actions. The GMS is proposed to support the needs of the U.S. Army in three main areas: site characterization, contamination assessment, and evaluation of remediation alternatives. To do this, the GMS will include numerical algorithms for simulating the hydrogeologic and biogeochemical processes that must be considered when developing remediation programs for Army and other sites. An essential feature of the GMS will be user interfaces which augment model application …

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Modeling Dredged Material Disposed In Open Water, B. H. Johnson, D. N. Mccomas, D. C. Mcvan Jan 1992

Modeling Dredged Material Disposed In Open Water, B. H. Johnson, D. N. Mccomas, D. C. Mcvan

United States Army: Publications

Physical model disposal tests at a 1:50 scale have been conducted to provide guidance on numerical model developments and to provide data sets for numerical model verification. These tests have been conducted with a model split-hull barge and a multibin hopper vessel. Both stationary and moving disposals have been monitored. Results imply that the bulk behavior of the disposal material in both the descent and bottom surge phases can be approximately scaled to the prototype. Visual observations have resulted in modifications to an existing numerical model such that the disposal is represented by a series of downward convecting clouds from …

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An Acoustic Impedance Method For Subbottom Material Characterization, Richard G. Mcgee, Robert F. Ballard, Jr. Jan 1992

An Acoustic Impedance Method For Subbottom Material Characterization, Richard G. Mcgee, Robert F. Ballard, Jr.

United States Army: Publications

This paper discusses modified seismic reflection technique tailored to the characterization of bottom and subbottom materials. The application of acoustic impedance principles has resulted in the development of a method for rapidly determining the type and density of subbottom materials scheduled for dredging. Acoustic theory is discussed only in sufficient detail to enable the reader to understand basic concepts.

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Overtopping Protection Alternatives For Dams, Noel R. Oswalt Jan 1992

Overtopping Protection Alternatives For Dams, Noel R. Oswalt

United States Army: Publications

A reevaluation of design floods for dam safety within the united states showed that the need to modify dams to accommodate larger floods has greatly increased in recent years. The occurrence of larger design floods would result in overtopping of the dams at many existing reservoirs due to insufficient storage or release capacity. When the addition of storage or release capacity becomes impractical or too costly, dam owners must sometimes resort to providing overtopping protection.
An ASCE Hydraulics Division Task committee on Alternatives for Overtopping Protection for Dams was established in 1991 to inventory and evaluate modification alternatives for new, …

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A Numerical Simulation Approach To Estimating Disposal Site Stability, Norman W. Sheffner Jan 1992

A Numerical Simulation Approach To Estimating Disposal Site Stability, Norman W. Sheffner

United States Army: Publications

A systematic methodology is described for estimating the long-term response of a dredged material site to local environmental forcings. The methodology is based on the development of user-accessible data bases of wave and current time series and the subsequent application of these boundary conditions to coupled hydrodynamic, sediment transport, and bathymetry change models. The approach was developed to provide an estimate of long-term material fate for use in determining whether an existing or proposed disposal site will be dispersive or nondispersive over periods of time on the order of months to years.

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Reduced Recharge Capacity Of A Pump And Treat System, Cynthia L. Teeter, Douglas Gunnison, Norman R. Francingues, Mark E. Zappi Jan 1992

Reduced Recharge Capacity Of A Pump And Treat System, Cynthia L. Teeter, Douglas Gunnison, Norman R. Francingues, Mark E. Zappi

United States Army: Publications

The North Boundary treatment system at Rocky Mountain Arsenal (RMA), Commerce City, Colorado, involves pumping of contaminated groundwater from an unconfined aquifer from one side of a soil-bentonite (SB) slurry wall to three pulsed-bed activated carbon adsorbers and prefilter and postfilter systems. The treated water is injected into the unconfined aquifer on the other side of the slurry wall via 38 recharge wells and 15 recharge trenches, collectively referred to as the recharge system. Recharge capacity of the recharge system has declined over time, limiting the operating capacity of the system. Two probable causes for reduction of the recharge systems …

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Design Of Pneumatic Diffuser System, Steven C. Wilhelms, Charles W. Downer, Richard E. Price Jan 1992

Design Of Pneumatic Diffuser System, Steven C. Wilhelms, Charles W. Downer, Richard E. Price

United States Army: Publications

During non-generation periods, leakage through the wicket gates of a hydroturbine often results in very poor quality water (low or zero dissolved oxygen) in the tailrace of the hydropower facility. Generally, the leakage rate is relatively small, usually about 5-10 cfs per turbine. A bottom-mounted diffuser system was designed based on laboratory-measured and manufacturer-supplied specifications about the gas transfer characteristics of the bubble plume generated by an 11- inch flexible head diffuser. The design criteria and the overall effectiveness of the system were evaluated in field tests at Lake Eufaula, Oklahoma. The analysis of field data is reported herein.

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Treatment Of Contaminated Groundwater Using Chemical Oxidation, Mark E. Zappi, Beth C. Fleming, M. John Cullinane Jan 1992

Treatment Of Contaminated Groundwater Using Chemical Oxidation, Mark E. Zappi, Beth C. Fleming, M. John Cullinane

United States Army: Publications

Chemical oxidation was evaluated for treatment of a groundwater contaminated with trichloroethylene, acetone, and other organic compounds as measured by the biochemical oxygen demand (BOD) test. Results indicated that maximum contaminant removal was obtained using a combination of hydrogen peroxide, high intensity ultraviolet light, and the addition of tungsten trioxide under acidic conditions.

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Npdes Permitting For Storm Water Discharges Associated With Industrial Activity, Paul Makowski, John G. Garland Iii Jan 1992

Npdes Permitting For Storm Water Discharges Associated With Industrial Activity, Paul Makowski, John G. Garland Iii

United States Air Force: Publications

Recent changes to the National Pollutant Discharge Elimination System (NPDES) program require that storm water discharges associated with industrial activity and from municipal separate storm sewer systems serving a population of 100,000 or more be regulated under the NPDES program. These changes greatly expanded the number of industrial facilities subject to the NPDES program. An industrial facility that is subject to the regulation must apply for a storm water permit based on application requirements that were recently established. The NPDES permit application process for storm water discharges associated with industrial activity is discussed.

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Structural And Non-Structural Alternatives For Accommodating Larger Floods At Dams, Louis E. Buck Jan 1992

Structural And Non-Structural Alternatives For Accommodating Larger Floods At Dams, Louis E. Buck

United States Department of Energy: Publications

This paper provides an overview of structural and non-structural alternatives for accommodating larger floods at dams. The first two alternatives discussed, raising the height of the project and/or lowering the reservoir pool, can be used to prevent overtopping by increasing the available floodwater detention storage in the reservoir. Data gathered by an ASCE task committee survey on modifications that include increased storage by raising project height are summarized and discussed. The third alternative discussed, early warning systems, can provide a low cost alternative to structural modifications. Case studies for the warning systems at the Santee Cooper North Dam and the …

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Integrated Assessment Of Temperature Change Impacts On The Tva Reservoir And Power Supply Systems, B. A. Miller, V. Alavian, M. D. Bender, D. J. Benton, P. Ostrowski Jr., J. A. Parsly, M. C. Shiao Jan 1992

Integrated Assessment Of Temperature Change Impacts On The Tva Reservoir And Power Supply Systems, B. A. Miller, V. Alavian, M. D. Bender, D. J. Benton, P. Ostrowski Jr., J. A. Parsly, M. C. Shiao

United States Department of Energy: Publications

Power systems often depend upon reservoir operations to generate hydropower, as well as to support thermal (nuclear and fossil) power generation. Thermal power plants frequently utilize reservoirs/rivers to provide condenser cooling water, dissipate thermal waste discharges, and/or supply safety intake water for emergency cooling systems at nuclear plants. Support of power production, however, must usually be balanced against other reservoir multiple uses such as flood control, navigation, recreation, water supplies, and environmental management.

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Contaminated Sediment Transport During Floodsl, Thomas A. Fontaine Jan 1992

Contaminated Sediment Transport During Floodsl, Thomas A. Fontaine

United States Department of Energy: Publications

Over the past 48 years, operations and waste disposal activities at Oak Ridge National Laboratory have resulted in the contamination of parts of the White Oak Creek catchment. The contaminants presenting the highest risk to human health and the environment are particle reactive and are associated with the soils and sediments in the White Oak Creek drainage system. The erosion of these sediments during floods can result in the transport of contaminants both within the catchment and off-site into the Clinch River. A data collection program and a modeling investigation are being used to evaluate the probability of contaminated sediment …

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Dynamic Plug Flow Reactor Network Model For Contaminant Transport In Water Distribution Systems, James Uber, Ken Hickey, Mao Fang, Lew Rossman Jan 1992

Dynamic Plug Flow Reactor Network Model For Contaminant Transport In Water Distribution Systems, James Uber, Ken Hickey, Mao Fang, Lew Rossman

United States Environmental Protection Agency: Publications

We present a network water quality model that idealizes the distribution system as a network of ideal flow reactors, namely plug flow reactors. The plug flow reactors are linked together through an assumption of complete mixing at the network nodes. The resulting system of coupled 2-D (space - time) partial differential equations are discretized spatially using a finite difference scheme, and solved by numerical integration. The model will be evaluated with regard to its prediction capabilities, relative to previous modeling efforts.

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