Engineering Commons^™

Machining Of Composite Materials. Part I: Traditional Methods, Serge Abrate, D. A. Walton

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Composite materials are more difficult to machine than metals mainly because they are anisotropic, non-homogeneous and their reinforcing fibers are very abrasive. During machining, defects are introduced into the workpiece, and tools wear rapidly. Traditional machining techniques such as drilling or sawing can be used with proper tool design and operating conditions. A review of traditional machining methods applied to organic and metal matrix composites is presented in this article. The use of non-traditional machining methods such as waterjet, laser and ultrasonic machining will be discussed in the second part. © 1992.

Consideration Of Phase Transformations In The Study Of Shear Bands In A Dynamically Loaded Steel Block, Z. G. Zhu, R. C. Batra

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We study plane strain thermomechanical deformations of a square block made of steel and model a material defect in it by a rigid non-heat-conducting ellipsoidal inclusion located at the center of the block. The boundaries of the block are presumed to be thermally insulated, and its top and bottom surfaces compressed vertically at a prescribed rate. The loading pulse is assumed to be made up of three parts; an initial segment in which the speed increases from zero to the steady value, the steady part, and the third part in which the speed decreases gradually to zero and is maintained …

Analysis Of Shear Bands In Simple Shearing Deformations Of Nonpolar And Dipolar Viscoplastic Materials, R. C. Batra

Mechanical and Aerospace Engineering Faculty Research & Creative Works

During the past few years, we have studied numerically the initiation and growth of shear bands in nonpolar and dipolar viscoplastic materials being deformed in simple shear, and in nonpolar materials undergoing plane strain deformations. We summarize here our work for the former problem. © 1992 American Society of Mechanical Engineers.

Hydration Behavior Of Laser Dye Aerosols Of Mixed Composition Having High Critical Supersaturations, Max B. Trueblood, Donald E. Hagen, Darryl J. Alofs

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This Study Concerns Aerosol Particles of Mixed Composition. the Particles Contain a Water Insoluble Core (Polystyrene Latex), Surrounded by a Water Soluble Shell (Various Fluorescent Dyes). a Collison Nebulizer and an Electrostatic Aerosol Classifier Are Used to Prepare the Aerosol; its Critical Supersaturation Spectrum is Measured with a Diffusion Cloud Chamber. Experiments Were Done using Four Different Dyes (Disodium Fluorescein, Sulforhodamine 640, Sulforhodamine B and Rhodamine 560 Chloride) with Five Different Polystyrene Latex Sphere Sizes. the Results Indicate that a Kohler-Type Behavior is Obeyed. This Technique of Putting a Soluble Coating Onto an Insoluble Core is Found to Be a …

Smimd - A Synchronous Multiple Instruction Multiple Data Computer Architecture, Cathy C. Roberts

Computer Science Theses & Dissertations

This thesis assesses the feasibility of utilizing a hypercube interconnect topology to link a heterogeneous processor array in a very long instruction word (VLIW) computer architecture. The research focused upon the selection of a suitable arrangement of processors for the computer and the subsequent demonstration of the architecture's capability to handle simple loop iterations. Previous attempts at VLIW computer design are summarized, the new SMIMD architecture is presented, and suggestions for future research are given. The thesis concludes with results of the initial performance evaluations of the architecture design.

A Comparison Of Alphanumeric, Direct Manipulation Graphic, And Equivalent Interface Design For A Production Scheduling Task, Ann C. Fulop

Psychology Theses & Dissertations

Scheduling is an essential factor influencing the efficiency of any production system. The effectiveness of the scheduling system depends upon the interaction of the human and machine. Thus, to effectively design the interface between the human and the machine, the human factors professional must understand scheduling behavior and the information requirements of the scheduling task. The present study modeled human scheduling behavior and determined the information requirements of the scheduling task. The study also compared alphanumeric, direct manipulation graphic, and equivalent interfaces to determine which interface best supports scheduling. The results of the study show that schedulers monitor the current …

Characterizations Of Antimony Tri‐Sulfide Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.

Biological Assessment Missouri National Recreational River

United States Army Corps of Engineers, Omaha District

This is in response to your May 21, 1992, letter requesting review and concurrence on a biological assessment prepared to evaluate routine actions of Section 404 and Section 10 of the Clean Water Act along the Missouri National Recreational River. This response has been prepared in coordination with the U.S. Fish and Wildlife Service's (Service) Nebraska Fish and Wildlife Enhancement Office.

This revision of your March 6, 1991, assessment addressed many of the concerns and recommendations that we brought to your attention in our April 2, 1991, letter to Mr. Kenneth Cooper and subsequent meeting on May 6, 1991. However, …

Darcy-Weisbach Roughness Coefficients For Gravel And Cobble Surfaces, John E. Gilley, Eugene R. Kottwitz, Gary A. Wieman

Department of Agricultural and Biological Systems Engineering: Presentations and White Papers

A laboratory study is conducted to measure Darcy-Weisbach roughness coefficients for selected gravel and cobble materials. Varying rates of flow are introduced into a flume in which a given size class of gravel or cobble material is securely attached. Roughness coefficients are calculated from measurements of discharge rate and flow velocity. The laboratory data are used to develop regression equations for relating roughness coefficients to surface cover and Reynolds number. Accurate prediction of roughness coefficients for gravel and cobble surfaces will improve our ability to understand and properly model upland flow hydraulics.

Cultivators For Conservation Tillage, Robert Grisso, Paul J. Jasa, Elbert C. Dickey

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Cultivation, a proven weed control methods, should be used primarily to control weeds, rebuild ridges, or aerate poorly drained or crusted soils. Cultivating just to stir the soil usually dries the soil and can result in lower yields during drier cropping conditions. For example, cultivating during warm and windy conditions can result in ¼ to ¾ inches of soil moisture loss.

The main difference between a conservation tillage cultivator and a conventional cultivator is the ability to handle residue and penetrate the soil. By definition, conservation tillage should leave at least 30 percent of the soil surface covered with crop …

Definitions Of Tillage Systems For Corn, J. C. Siemens, Elbert C. Dickey, E. D. Threadgill

Department of Agricultural and Biological Systems Engineering: Faculty Publications

If "tillage" is defined as the mechanical manipulation of soil, it follows, then, that a "tillage system" would be the sequence of soil-manipulation operations performed in producing a crop. Today, however, such a definition is recognized as inadequate. We know, for instance, that the management of non-harvested plant tissue (i.e., residue) affects both crop production and soil erosion, and that field operations in which the soil is not tilled have a marked influence on soil condition.

Therefore, in this publication, a tillage system is the sequence of all operations involved in producing the crop, including soil manipulation, harvesting, chopping or …

Parameter Sensitivity And Optimization Predictions Of A Hydrogen/Oxygen Alkaline Fuel Cell Model, Michael C. Kimble, Ralph E. White

Faculty Publications

A mathematical model is used to predict parameter sensitivities and optimal design parameters for a hydrogen/oxygen alkaline fuel cell. A sensitivity analysis of the various transport and electrode kinetic parameters indicates which parameters have the most influence on the predicted current density and over which range of potentials these parameters affect the fuel-cell performance the most. This information can be used to decide which parameters should be optimized or determined more accurately through further modeling or experimental studies. The effect of various design parameters on the limiting current density are investigated to determine if optimal values exist for the parameters. …

The Self-Discharge Of The Niooh/Ni(Oh)2 Electrode Constant Potential Study, Z. Mao, Ralph E. White

Faculty Publications

Hydrogen oxidation currents at a NiOOH/Ni(OH)₂ electrode were measured directly at constant potentials for various hydrogen pressures and states of charge. It was found that the hydrogen oxidation current is linearly proportional to the hydrogen pressure at all electrode potentials and that the logarithm of the anodic current is a linear function of electrode potential. It was also found that hydrogen oxidation on the nickel substrate material was strongly inhibited by the presence of nickel hydroxide on the substrate surface. By comparing the currents for hydrogen oxidation and oxygen evolution on the NiOOH/Ni(OH)₂ electrode and on a nickel …

Mathematical Modeling Of Cathodic Protection Using The Boundary Element Method With A Nonlinear Polarization Curve, J. F. Fan, S. N. R Pakalapati, T. V. Nguyen, Ralph E. White, R. B. Griffin

Faculty Publications

The distributions of potential and current density around a cathodically protected pipeline in seawater were determined using the boundary element technique. A nonlinear polarization curve for a low carbon steel in artificial sea water was obtained from dc-potentiodynamic measurements and was fitted for use as the boundary condition on the pipe. The program was used to evaluate cases in which one or two aluminum sacrificial anodes are used to protect a low carbon steelpipe in seawater. The results show that the number of anodes, the sizes of the anodes, and the distance between the anodes and the cathode are of …

Hydrogen Diffusion, Solubility, And Water Uptake In Dow's Short-Side-Chain Perfluorocarbon Membranes, Yu-Min Tsou, M. C. Kimble, Ralph E. White

Faculty Publications

Hydrogen gas diffusion coefficients and solubilities as well as water uptake values are reported for Dow's short-side-chain perfluoro-sulfonic and -carboxylic membranes of different equivalent weight (EW). The diffusion coefficients and solubilities were determined with an electrochemical test cell. Hydrogen solubility decreases with increasing EW in the lower EW range and tends to level off at higher EWs for both types of membranes. Both hydrogen solubility and diffusion coefficients of a sulfonic membrane with EW higher than 800 are higher than the corresponding values of a carboxylic membrane of similar EW. An unusual maximum is observed in the diffusion coefficient-EW plot …

Reduction Of Chromium (Vi) When Solar Selective Black Chromium Is Deposited In The Presence Of Organic Additive, Branko N. Popov, Ralph E. White, D. Slavkov, Z. Koneska

Faculty Publications

Electrochemical dc methods were used to study the reduction of chromium (VI) in the presence of organic additives. It is shown that F^–, thiourea, and citric acid are essential to enable deposition of black chrome from concentrated chromic acid solutions. A new formulation of the plating bath is defined. The optimum operating conditions under which spectrally selective surface of black chrome is deposited have been determined.

Maximizing Sustainable Ground-Water Withdrawals: Comparing Accuracy And Computational Requirements For Steady-State And Transient Digital Modeling Approaches, Richard C. Peralta, R. R.A. Cantiller, Gary L. Mahon

Civil and Environmental Engineering Faculty Publications

Rigorous models for maximizing sustainable groundwater withdrawals may require more computer memory for their constraint set than is available. In some situations, alternative constraint formulations yield similar or identical answers resulting in great saving in computer memory requirements. In order to evaluate the efficiency of using alternative constraints1 maximum ground-water withdrawal pumping strategies were computed by three digital models for a hypothetical area for a five-decade period. Model A maximized steady ground-water withdrawal. Model B maximized unsteady ground-water mining. Model C maximized unsteady ground-water mining subject to a constraint that final pumping be sustainable after the end of the 50-year …

Optimal Linear/Nonlinear, Quantity/Quality Management Of Complex Multilayer Aquifers By Embedding, Ali Gharbi, Richard C. Peralta

Civil and Environmental Engineering Faculty Publications

The embedding optimization modelling approach is adapted to aid long-term groundwater quality and quantity management of complex nonlinear multilayer aquifers. Implicit block-centered finite-difference approximations of the quasi-three-dimensional unsteady flow equation, and Galerkin finite-element approximations of the twodimensional advection-dispersion transport equation are embedded as constraints in the model. Other hydrological processes are also included as constraints. Cyclical linear differencing permits representation of nonlinear transport, even when contaminant is extracted by unsteady pumping (a decision variable). Also used are nonlinear (discontinuous derivative) constraints describing drainage, stream-aquifer interflow and evapotranspiration. The use of both linear and nonlinear formulations of the entire flow and …

Nonparametric Stratigraphic Interpretation From Drill Log Data, Upmanu Lall, A. I. Ali

Reports

Near surface groundwater contamination is a widespread problem. The potential for contamination of deep aquifers in such areas depends on the vertical hydraulic gradient as well as the extent and location of interconnection between the upper and lower aquifers. In alluvial, sedimentary environment, the geologic units are typically weakly connected lenses or layers of high or low conductivity with variable size, geometry and orientation. Drill logs provide qualitative, local information on such aquifer heterogeneities. A binary (high or low conductivity) indicator function is used to describe the aquifer system. A nonparametric statistical methodology for assessing the probability that a particular …

Fate And Transport Of Tce-Petroleum Hydrocarbon Mixture At Uttr, G. Nash Quashiga, Richard C. Peralta

Civil and Environmental Engineering Faculty Publications

In 1988 a preliminary assessment (PA) study was conducted at Chemical Disposal Pit No. 4 to address several concerns of Hill Air Force Base (HAFB), the facility operators. The objectives of the PA were; i) to assess the potential for organic chemical releases to the subsurface environment, and ii) to determine the need for any immediate control measures, if the subsurface environment were threatened.

Optimizing Perennial Groundwater Yield Planning For Nonlinear Systems: Approach Comparison, Shu Takahashi, Richard C. Peralta

Civil and Environmental Engineering Faculty Publications

Four alternative simulation/optimization models useful for computing optimal sustained-yield (steady-state) groundwater pumping strategies are compared in terms of formulation, solution procedure, accuracy, and computational efficiency. The different models require different computer processing time and memory. For the aquifer tested system, if more than 10% of the cells have pumping as a decision variable, a fully linearized embedding model will require less computer memory than any other model. All the models address linear and nonlinear steady-state flow in multilayer, unconfined/confined aquifers. They also address several types of nonsmooth external flows. Newly presented are a response matrix model solving external flows described …

Best Management Practices (Bmps) To Minimize Nitrate Leaching From Irrigated Potatoes, Ahmad Yar Ranjha, Richard C. Peralta, Robert W. Hill

Civil and Environmental Engineering Faculty Publications

Numerous preliminary simulations are again performed to determine the smallest fertilizer amount, applied througii sprinkler irrigations (chemigation), that should still yield 15.3 tons of potatoes per acre. Applying only 68 lbs/ac of ammonium nitrate fertilizer in the first irrigation on June 28, should be sufficient. Again, total crop N uptake equals potential crop N uptake throughout the growing season. Except for the net income and applied fertilizer N uptake efficiency, all the other results computed by NLEAP (Figure 4 and Table 1) are very similar to results of scenario II. Applied fertilizer N uptake efficiency is the highest (91%) in …

Pluman, Decision Support System For Groundwater Contaminant Plume Simulation/Optimization Management Model, Herminio H. Suguino, Richard C. Peralta

Civil and Environmental Engineering Faculty Publications

No abstract provided.

Optimal Management Of Irrigation And Vadose Zone Pesticide Transport, M. A. Hegazy, Richard C. Peralta

Civil and Environmental Engineering Faculty Publications

A management model is developed for maximizing crop yield while avoiding unacceptable pesticide leaching. Utilized constraint equations: maintain a soil moisture volume balance, describe downward pesticide transport, and limit the amount of pesticide reaching groundwater. The reported optimization model is the first which includes unsaturated zone pesticide transport. It is designed to help prevent nonpoint-source contamination of shallow groundwater aquifers. The model computes optimal irrigation amounts for given soil, crop, chemical, and climate data and irrigation frequencies. The model is tested for different irrigation scenarios. The modeling approach is promising as a tool to aid developing environmentally sound agricultural production …

Optimal Perennial Groundwater Yield Planning For The East Shore Area, Utah, Shu Takahashi, Richard C. Peralta

Civil and Environmental Engineering Faculty Publications

Computer models are developed for computing optimal perennial groundwater withdrawal strategies for the East Shore Area of Utah's Great Salt Lake. The underlying aquifer has three confined or unconfined layers. Both embedding and response matrix (RM) approaches are tested and compared. Historically, it has been difficult to incorporate simulation of an unconfined aquifer and many external flow equations described by nonsmooth functions within linear programming models. RM models normally assume system linearity. The presented RM model overcomes this difficulty using cycling and influence coefficients generated with a modified MODFLOW model. In this groundwater flow simulation model, the above nonlinear terms …

Steel Deck Institute Design Manual For Composite Decks, Form Decks, Roof Decks, And Cellular Deck Floor Systems With Electrical Distribution, Steel Deck Institute

Steel Deck Institute (SDI) Specifications and Manuals (1939 - present)

No abstract provided.

Effect Of Magnetic And Density Fluctuations On The Propagation Of Lower Hybrid Waves In Tokamaks, George Vahala, Linda L. Vahala, Paul T. Bonoli

Electrical & Computer Engineering Faculty Publications

Lower hybrid waves have been used extensively for plasma heating, current drive, and ramp-up as well as sawteeth stabilization, The wave kinetic equation for lower hybrid wave propagation is extended to include the effects of both magnetic and density fluctuations. This integral equation is then solved by Monte Carlo procedures for a toroidal plasma. It is shown that even for magnetic/density fluctuation levels on the order of 10^-4, there are significant magnetic fluctuation effects on the wave power deposition into the plasma. This effect is quite pronounced if the magnetic fluctuation spectrum is peaked within the plasma. For …

Charge-State Equilibrium And Nonequilibrium Modeling Of The Carbon-Pellet Plasma Interaction, A. G. Elcashlan, G. A. Gerdin, L. L. Vahala, P. B. Parks

Electrical & Computer Engineering Faculty Publications

Self-consistent equilibrium and nonequilibrium charge-state models are formulated for the spherical expansion of low-Z pellet vapor as an inviscid perfect gas of constant ratio of specific heats being heated volumetrically by the incident electrons of a thermonuclear plasma. The two models are found to be in agreement in the region where the ratio of the ionization length ζ_j to pellet radius r_p is less than unity, but a single parameter, such as the magnitude of this ratio on the sonic surface, is insufficient to determine whether an equilibrium model will be valid for all regions of the ablatant …

Effect Of Fluctuations On Lower Hybrid Power Deposition And Hard X-Ray Detection, George Vahala, Linda L. Vahala, Paul T. Bonoli

Electrical & Computer Engineering Faculty Publications

The hard X-ray intensity radial profiles from lower hybrid current drive experiments are interpreted as being correlated with fluctuations in the bulk plasma. This view seems to be dictated by comparing the hard X-ray data for various n_║ with the Monte Carlo solutions of the lower hybrid wave energy deposition on plasma electrons. Information on internal magnetic fluctuations may, under certain conditions, be unfolded from a n_║ scan of the hard X-ray profiles.

Electromagnetic Wave Scattering From Magnetic Fluctuations In Tokamaks, L. L. Vahala, G. Vahala, N. Bretz

Electrical & Computer Engineering Faculty Publications

Cross sections are calculated for electromagnetic wave scattering and mode transformation from magnetic and density fluctuations in a homogeneous plasma. For the special case of scattering perpendicular to the magnetic field, density fluctuations scatter ordinary to ordinary and extraordinary to extraordinary modes-but cannot transform these modes. On the other hand, magnetic fluctuations perpendicular to the field can transform modes but cannot scatter on a single branch. For incident frequencies on the order of the electron plasma frequency or gyrofrequency, the cross sections for scattering and transformation due to field and density fluctuations have a similar value. Estimates are given for …