8:40 ON THE USE OF COMPACTLY SUPPORTED WAVELETS IN THE FINITE ELEMENT SOLUTION OF ELLIPTIC PROBLEMS

W. Elliott Hutchcraft*, Lee A. Harrison, and Richard K. Gordon, University of Mississippi, University, MS 38677

Typically, the finite element method requires the solution of a large matrix equation. Furthermore, as the number of basis functions is increased to achieve greater modeling accuracy, the condition number of the system matrix increases as well. If an iterative solution technique is employed, this increase in the condition number can lead to numerical instabilities, slow convergence, or even failure to converge. In recent years, there has been significant interest in attempting to circumvent these problems through the use of wavelet and wavelet-like basis functions. It has been shown mathematically that when such basis functions are used in conjunction with a simple diagonal preconditioner, the finite element matrix remains very well conditioned even when the number of basis functions becomes quite large. In this paper, our objective is to consider the practical issues involved in the use of these basis functions. Our results show that the use of wavelet and wavelet-like basis functions can lead to dramatic increases in the speed of the iterative solution technique. We will show how we have come to the conclusion that although the construction of wavelet or wavelet-like basis functions is more involved than that of the traditional basis functions, in many cases this cost is more than offset by the considerable reduction in the condition number of the system matrix.

9:00 ROCK PROPERTIES FOR GROUND MOTION PREDICTION AT YERBA BUENA ISLAND

Edgar Hardy, Mississippi State University, Mississippi State, MS 39762

Tests were done on a rock sample from Yerba Buena Island to test the rock's behavior during earthquakes. These simulation tests were done to aid in research on the prediction of strong ground motion in the Bay Bridge area of San Francisco. Tests determined that the rock sample's shear modulus (stiffness) in earthquake simulated conditions was much higher when partially saturated with water than when completely dry. In addition, the rock contained microfractures, which were dosed by the application of uniaxial stress. This research was done by the author while participating in a summer research program for undergraduates at Lawrence-Livermore National Labs.

9:20 MONITORING OF NUCLEAR RADIATION AROUND ALCORN STATE UNIVERSITY

Amin Haque*, Dainel Muhammad, and Deidre Walker, Alcorn State University, Lorman, MS 39096

The purpose of this research was to correlate levels of nuclear radiation and radioactivity in ASU environment with possible radioactive releases from Grand Gulf Nuclear Plant (GGNP) operation. Experience shows that operation of nuclear plants add radioactivity to the environment. In the Chernobyl meltdown, large quantities of potential hazardous fission products were released from the core of the reactor. Some common radionuclides which can be released during routine operations of a nuclear plant are Sr⁸⁹, Sr⁹⁰, Cs^l37, I¹³¹, Ra²²⁶, H³, C¹⁴, Mn⁵⁴, Ba/Ln¹⁴⁰, and Kr ⁸⁵ Also, corrosion products, such as Co⁵⁸, Co⁶⁰, Mn⁵⁴, Fe⁵⁴, and Cr⁵¹ are formed due to irradiation of steel materials, and these produce radiation. Nuclear radiations are hazardous to our health and a threat to our existence. The immediate detection of any release of radionuclides from a nuclear plant is very important. We used three types of survey meters, one sensitive mainly to -radiation at very low level, the second sensitive to -radiation at intermediate level, and the third sensitive mainly to and , and to less extent to -radiation. The -radiation level was found to be 5 µR/H to 11.67 µR/H, 15 µR/H to 65 µR/H and the combined , , and radiation level 15 µR/H to 29 µR/H, respectively. The normal background range is 10 to 20 µR/H. The equipment used were old and the accuracy of their calibration was uncertain.

9:40 TECHNIQUES TO IMPROVE GPS ACCURACY

John W. Lipscomb, Jr., University of Southern Mississippi, Hattiesburg, MS 39406

The Global Positioning System (GPS) is a satelite-based radionavigation system operated by the U.S. Department of Defense (DOD). The encrypted "Precise Positioning System" (PPS) is available only to the U.S. military and provides 22 meter accuracy (2 = 95%). For other GPS users, the "Standard Positioning System" (SPS) is available with an accuracy of 100 meters (2 = 95%). The SPS accuracy is insufficient for woods, fog, submerged object location, night, and other poor visibility applications. An expensive and bulky solution is a "Differential GPS Receiver" which receives position correcting signals from a known location. Because the SPS has an uncorrelated time of about 4 minutes, averaging and sampling over rather short periods can greatly improve accuracy. In the author's experiments, position averaging over 10 minutes can reduce the 2 error to 37 meters. Twelve hours of averaging can reduce the 2 error to 2 meters. Three position samples can be "optically" averaged on the GPS plot screen by choosing the center of an imaginary triangle with the three positions as vertices. Three samples taken at 5 minute intervals improve the 2 accuracy to 27 meters. Moving navigation involves two position errors; the destination error and the en route error. To navigate accurately to a known location, en route position averaging may be necessary and the GPS must be used to calculate a heading and distance to the destination.

10:00 Break

10:20 COMPUTER SIMULATION MODELING OF CELL POPULATION IN HIV IMMUNE RESPONSE

Aaron Mielke* and R.B. Pandey, University of Southern Mississippi, Hattiesburg, MS 39406

A computer simulation model is introduced to study the growth and decay of cellular population in immune response relevant to HIV. Four cell types, macrophages, helper cells, cytotoxic cells, and antigens are considered with a set of 10 cellular interactions. Cellular automata are used for the local interactions and viral mutation is considered probabilistically with the fuzzy interaction set. Variation of the population of each cell type with time is studied as a function of mutation rate. Simulation data show that increasing the mutation rate enhances the viral growth and suppresses the growth of host cells. Above a certain mutation rate, the helper cells population depletes leading to AIDS.

10:40 A NEW INSIGHT INTO THE GAMMA RAY BURST PHENOMENON

Yuan Yan*, John Patrick Lestrade, and Jing Hao, Mississippi State University, MS 39762

Possible physical causes of the Gamma Ray Burst phenomenon have attracted much attention in recent time. Our previous study suggested that a time scaling property could be present in GRB time profiles. Though earlier studies on the Fourier spectrum of GRB time profiles gave no significant results, we believe a proper Fourier analysis could give some important insight. Using long-duration GRB time profiles, we measure a parameter in the frequency domain that is consistent with the published results from the time domain. This consistency is a sign that turbulence exists in GRB sources.

11:00 THE EFFECTS OF GLASS SAMPLE TEMPERATURE ON LASER INDUCED BREAKDOWN SPECTROMETRY

John T. Rigsby III*, Chun Fu Su, Jagdish P. Singh, Fang-Yu Yueh, and Robert L. Cook, Mississippi State University, Mississippi State, MS 39762

The laser-induced breakdown spectrometry technique has been used to investigate the toxic metals elements present in all three phases of solid, liquid and gas. The technique has been employed successfully to measure various toxic metal in the off-gas streams and the elemental compositions of the vitrified glass samples at the Diagnostic Instrument and Analytic Laboratory (DIAL) in Mississippi State University. The recorded spectral line intensities of the identified elements have been used to infer the plasma temperature and the elemental concentration ratios for different samples. The effects of the sample temperatures on the observed spectral line intensities and the plasma temperatures have also been studied for the samples with various melting temperatures. Careful study of the LIBS spectra of various glass samples show that (1) the inferred plasma temperature increases while the sample temperature increases, (2) the spectral line intensities increase when the sample temperature increases, (3) the spectral line intensities decrease to a low value when the sample temperature is near the melting temperature of a certain element present in the sample, then again increase as the sample temperature increases, and (4) for molten glass, the spectral line intensities are almost independent of the sample temperature. The various results and possible explanations will be presented.

11:20 POLYMER CHAINS AT ADSORBING WALL IN AN ELECTROPHORETIC DEPOSITION

Grace M. Foo and R.B. Pandey*, National University of Singapore, Singapore, Republic of Singapore, and University of Southern Mississippi, Hattiesburg, MS 39406

Growth of polymer density in an electrodeposition model of polymer chains on an adsorbing wall is studied using a Monte Carlo simulation. Effects of the driving field (B), temperature (T), and chain length (Lc) on the density profile and wall coverage are investigated. The spatial density profile shows onset of oscillation near the wall at a characteristic field (Bc) which depends on chain length and temperature. Adsorption-to-desorption transition at the wall occurs on increasing the temperature. The conformation of the chains shows interesting crossover behavior from bulk-to-wall. This work is supported in part by a NSF-EPSCoR grant.

11:40 Poster Session

AUTOMATED TRAFFIC ACCIDENT DATA ENTRY

Velinda Calvert, Mississippi State University, Mississippi State, MS 39762

The Arkansas State Highway and Transportation Department (AHTD) needed a faster method for entering traffic accident reports into their traffic records system. The method used currently required information to be typed in by hand resulting in a lag time of about eight months. Dr. Daniel Berleant and Mrs. Sharon Johnson of the University of Arkansas Computer Systems Engineering Department created a new method for entering traffic accident reports into the records system. The method utilized a scanner, Visual BASIC^©, MicroSoft Access^©. The author was given the tasks of (1) selecting the method of converting scanned accident reports to data which could be stored in MicroSoft Access^© in a central computer and retrieved from any location in the state. (2) redesigning the forms for more effective scanning, and (3) selecting the best scanner for the job. This presentation will detail the progress made in completing the three tasks during the summer of 1998 while the author was participating in an undergraduate summer research program.

DECONVOLUTION BY EXTRAPOLATING THE MEASURED LINEWIDTHS AT FEW SLIT WIDTHS

Chandra M. Pathak¹*, S.N. Singh², R.K. Singh², and B.P. Asthana², ¹Alcorn State University, Lorman, MS 39096, and ²Banaras Hindu University, Varanasi 221005, India

A simple, convenient and precise technique of deconvoluting the Lorentzian (true) Raman linewidth, _L, from the observed Raman linewidth, (_½)_R [the FWHM (full width at half-maximum) of the Raman line in question], through polynomial fitting, was developed. The precision of this technique is a consequence of the fact that the values of _L/(_½)_R (=Y), obtained by exact numerical evaluation of the Voigt profiles for the Raman bands, was fitted to the third- and fourth-degree polynomials in S/(_½)_R (=X), S being the spectral slit width measured as the linewidth (FWHM) of a narrow spectral line recorded at the same slit setting as the Raman line. The procedure of obtaining _L, from the knowledge of S, (_½)_R and X, yields better results. Another technique of deconvolution involving the measurement of Raman linewidths of a particular Raman line for about five or six different slit widths, will be presented. The measured linewidths (_½)_R, when extrapolated to S 0, give the value of _L directly. A careful comparison with the other deconvolution techniques reveals that the method of polynomial fitting is relatively more precise than other semi-analytical deconvolution techniques, and the extrapolation technique also gives reasonably good results. The applicability of both methods was tested by taking some selected Raman lines.

1:30 AN ANIMATION DEPICTING IMAGE FORMATION

Samantha D. Shoemake* and John T. Foley, Mississippi State University, Mississippi State, MS 39762

The Optics Project (TOP) is a computer graphics system that allows the user to do interactive physics. In this presentation we will discuss TOP's Geometrical Optics module. This module simulates an image being formed as light passes through a system of lens and stops. All of the optical elements in the module may be moved and their properties (size, or focal length, or . . .) changed in order to give the user the freedom to investigate a variety of problems. We will show an animation made using TOP which will demonstrate the physics of image formation in a one lens system.

1:50 PHYSICAL MODELS FOR SURFACE RUNOFF

Amin Haque* and Asim Haque, Waterways Experiment Station, Vicksburg, MS 39180, and Tulane University, New Orleans, LA 70118

The overland flow of rainfall-excess, considered to be pulses or thin sheet of water, is described by kinematic wave equations. Applying appropriate initial and boundary conditions and surface resistance law the equations are solved analytically, giving the surface runoff profile as a function of space and time. The volumetric water flux per unit plane width is related nonlinearly to the water layer thickness. Runoff graphs were constructed for various types of surfaces of constant slope, with uniform surface texture. The effects of different parameters on overland flow were studied. The flow was assumed laminar as well as turbulent, linear and nonlinear. From the inspection of the graphs, it was found that the lower the rainfall-excess rate the longer were the starting time and peak time and the smaller the peak runoff value at any distance. We found that overland flow increased rapidly to the peak value followed by rapid decline that began at the moment the rainfall-excess ceased, and then approached zero very slowly. Our results were in good agreement with the measured results of Yu and McNown, although there was slight shifting in the time scale. This could be because overland flow is both unsteady and spatially varied process. The physical models predict and estimate infiltration and surface runoff reasonably well and can be applied under different soil conditions.

2:10 VIRTUAL MANUFACTURING

S. Kant Vajpayee, University of Southern Mississippi, Hattiesburg, MS 39406-5137

Virtual manufacturing is a new concept in the production and distribution of tangible goods. Under this concept a product is manufactured only when its customer has decided to use/consume it and has paid for it. It results in inventoryless factories and distribution centers. The concept is practical due to the ubiquity of computers and information technologies. They enable the design and production functions to be computer-simulated and tested, with no need to build any prototype. This results in shorter concept-to-market time, reduced tooling cost and material waste, and "get it right the first time." The customer enjoys a dry run of the product on his/her terminal before deciding to buy it. All this takes place virtually--hence the name. Virtual manufacturing has been called the next revolution in global manufacturing. It has begun to be applied in the manufacture of computers and associated parts, while the manufacturers of other products are getting ready to embrace it. It is likely to do to manufacturing what mechanization did to farming--fewer people producing on demand all the tangible goods needed.

2:30 DEVELOPMENT OF A PHOTOFRAGMENTATION-LASER INDUCED FLUORESCENCE (PF-LIF) SENSOR FOR THE DETECTION OF 2,4,6-TRINITROTOULENE (TNT) IN SOIL AND GROUND WATER

Tracy S. Miller*, Jagdish P. Singh, Fang-Yu Yueh, and David L. Monts, Mississippi State University, Mississippi State, MS 39762-5932

There has been an increase in the study of toxic energetic materials (EMs) in the soils surrounding defense sites. EMs such as 2,4,6-trinitrotoluene (C₆H₂CH₃(NO₂)₃ or TNT for short) can get into the soil and later into the water tables. What makes them even more dangerous is their solubility. To prevent this from happening, contaminated soil needs to be treated before migration continues. To treat this soil, methods of detecting EMs must be developed and perfected. Laser photofragmentation (PF) and subsequent nitric oxide (NO) laser-induced fluorescence (LIF) have been developed to measure the concentration of EMs, such as TNT, in soil and ground water. Gas-phase EMs photodissociate to NO₂ when exposed to radiation near 226 nm. The NO₂ then dissociates into NO that gives an intense luminescence. The EM concentration in inferred from the intensity of the NO fluorescence. A PF-LIF laser-based sensor is being developed to be used with the U.S. Army Corps of Engineers' Waterways Experiment Station's (WES) cone pentrometer. PF-LIF signals from mixtures of TNT and simulated soil were recorded. The results of studies of the temporal decay of the NO PF-LIF signal as a function of temperature, TNT concentration, and water content will be presented.

2:50 Break

3:00 A RAY TRACING ALGORITHM FOR SEISMIC TRAVELTIME CALCULATIONS AND ITS APPLICATION TO A MEASUREMENT IN SOIL

Wilfred E. McKinney¹*, Craig J. Hickey², and James M. Sabatier², ¹Rhodes College, Memphis, TN 38112, and ²University of Mississippi, University, MS 38677

The calculation of seismic velocities from measured traveltimes depend on the path travelled by the seismic wave. The flight path of a seismic wave through the ground can be treated in analogy to a light ray in optics if certain criteria are upheld. If the source/receiver configuration is such that the source is located directly above a column of receivers, zero offset, the seismic velocities are easily calculated from the traveltimes. However, if the source is offset from the column of receivers the velocity calculation is more difficult because the path travelled by the seismic wave must be determined. Variations in the ground properties cause the sound ray to refract at the boundary between layers. An algorithm was developed to calculate first arrival traveltimes between a source placed on the surface of the ground and receivers located at depth. The algorithm is used to predict traveltimes between a source at various offsets and receivers buried at depth. These travel times are compared to actual measured traveltimes. The traveltimes are in good agreement for the larger distances but poor at the shorter distances.

3:20 THE BLACK-BODY LEVEL SHIFT INTEGRAL

Henk F. Arnoldus, Mississippi State University, Mississippi State, MS 39762

An atom at finite temperature and in thermal equilibrium with its environment experiences the presence of black-body radiation. This has as effect that the lifetimes of the atomic levels diminish with increasing temperature. A second effect is that the levels shift, in a way reminiscent of the Lamb shift. With fairly standard quantum electrodynamics an expression for the level shift as a function of the temperature can be derived. The result is an integral representation of this otherwise parameter free function. Since this is a universal function, pertaining to any atom in thermal equilibrium, it becomes important to understand its behavior in detail. A complication is that the representation is a Cauchy principle value integral over a singularity of the integrand. This complicates a numerical evaluation. We show how this singularity can be transformed away. Secondly, we have derived asymptotic expansions for high and low temperatures of this function. Due to the singularity in the integrand, this is not a trivial task. We also found that our solution deviates considerably from the result obtained with the commonly used electric dipole approximation in which the dipole is coupled to the electric field, rather than to the vector potential.

3:40 RAINFALL INFILTRATION AND SURFACE RUNOFF PRODUCTION MECHANISMS

Amin Haque* and Asim Haque, Waterways Experiment Station, Vicksburg, MS 39180, and Tulane University, New Orleans, LA 70118

The objective of the study was the understanding of the physical processes involved. Infiltration rate is dependent on the soil parameters--initial soil water content, hydraulic conductivity and soil water pressure head--the variations of which are computed using Campbell's equations. The infiltration process consists of two separate phases. During the first phase the soil surface is unsaturated. The second phase commences at the time of ponding when part of the rainfall begins to form the source of surface runoff. Water infiltration process in soil is described by Richard's equation, and its solution describes the infiltration rate in terms of the soil parameters--hydraulic conductivity and sorptivity, which is related to diffusivity. Surface runoff occurs only after ponding takes place. Ponding results only when surface soil layers become saturated. Surface saturation occurs because of two distinct processes. According to Horton, surface saturation can occur when the rainfall intensity R exceeds the saturation hydraulic conductivity K_s of the soil. Also, according to Rubin, the rainfall duration must be greater than the ponding time. According to the second process (Dunne), for R<K_s, runoff is produced if the initial water table is shallow. Surface saturation results because of a rising water table. The Horton runoff is more applicable on upslope areas, whereas the Dunne runoff is appropriate on wetlands.

4:00 INTRUSION CHARACTERISTICS OF TWO AUDITORY SECONDARY TASKS

Dedrick Thomas*, Edward Harden, and Frank Tucker, Mississippi State University, Mississippi State, MS 39762

In using the secondary task method for mental workload estimation, it is important that selected secondary task minimally intrude on the performance of the primary task. In this method, individuals are required to perform multiple task which are categorized as being either a primary or secondary task. The primary task is that task for which mental workload is being measured. The secondary task is the tool used to measure the workload required in performing the primary task. The secondary task measurement method is based on the concept that individuals have a finite mental capacity. The primary task is assumed to consume the majority of the mental capacity. This study analyzed the intrusion characteristics of two secondary tasks while typing, and performing a hand-eye coordination task. Results reveal that for one of these primary tasks, intrusion was present, while it was not evident in the other.

4:20 Divisional Business Meeting

8:40 ANALYSIS OF SPATIAL PATTERNS GENERATED BY TORSIONALLY OSCILLATING SPHERES IN STRATIFIED FLUIDS

R.F. Folse, University of Southern Mississippi, Hattiesburg, MS 39406-5046

Measurements were made of cellular flow patterns observed in the secondary flow fields of torsionally oscillating spheres in density stratified fluids. Shadowgraphs recorded the cellular patterns produced by spheres, radii between 2.52 cm and 5.08 cm, torsionally oscillating in stratified fluids with buoyancy frequencies in the range 0.8 rad/s Ns 2.1 rad/s. The frequency ranged between 1.0 rad/s 13.5 rad/s and the amplitude 1 rad. The vertical size, d, and the radial position, r, for each cell was determined from shadowgraphs. A correlation of the data is found to be d/r = 0.22 (/N)² Cot(), where is the angular position on the sphere surface measured from the pole. This results in a discrepancy with theoretical predictions based on a heuristic energy argument. This research was supported by an award from Research Corporation.

9:00 THERMAL STUDIES OF BINARY MIXTURES OF THE COMPONENTS OF THE NEMATIC LIQUID CRYSTAL E7

Niekiletta Woullard*, Joe B. Whitehead, Jr., and Nicole L. Gill, University of Southern Mississippi, Hattiesburg, MS 39406

Liquid crystal materials used in the display industry and in the fabrication of PDLC materials are usually multi-component eutectic mixtures. Multi-component liquid crystal mixtures are required to achieve wide nematic operating temperatures and large optical birefringence to maximize device contrast. A eutectic mixture is one where two or more components are mixed, in a specified ratio or ratios, so that the melting temperature of the mixture is suppressed below that of the components. Eutectic mixtures exhibit single step melting; whereas, non-eutectic mixtures exhibit two stage melting. The popular liquid crystal mixture E7 which is reportedly composed of a mixture of M24 (4-hexyloxy-4 cyanobiphenyl), K15(4-pentyl-4 cyanobiphenyl 1), K21( 4-heptyl-4 -cyanobiphenyl), and T15(4-pentyl-4 -terphenyl). The four components of E7 are combined in six binary mixtures which are analyzed using scanning optical microscopy and differential scanning calorimetry to determine if they exhibit eutectic behavior. The experimental data is then compared to the theoretical predictions based on the leChatelier-Schroder-van Laar equations to determine which binary mixtures exhibit eutectic.

9:20 INTEGRATED ISO 14000 AND ISO 9000--A CASE STUDY

S. Kant Vajpayee, University of Southern Mississippi, Hattiesburg, MS 39406-5137

Since the publication of ISO 14000 U.S. companies have begun to integrate its requirements with those of ISO 9000. One such company is Rockwell International with 60,000 employees spread over 150 sites worldwide generating annual sales in excess of $10 billion. The integration--or leveraging as some people prefer to call it--is obviously not feasible until IS0 9001 certification has been obtained. In larger companies, one of the divisions takes the lead in integration, while other divisions follow. In the case of Rockwell International its automation division has been the leader. Rockwell Automation had kept pace with the advances in quality management, implementing its TQMS back in the 1970s. Since its TQMS was much like ISO 9000, seeking ISO 9000 certification proved to be the logical step. It obtained ISO 9001 certification in 1990. When ISO 14000 came into being, the company found its goals compatible with those of the company itself. During the certification for procedure-driven ISO 14001, it has discovered that ISO 14000 is likely to become a global commercial issue bigger than ISO 9000.

9:40 PROGRESS IN THE STUDY OF ¹⁵⁴Dy NUCLEAR STRUCTURE

J.P. Zhang¹*, W.C. Ma¹, P.G. Varmette¹, R.V.F. Janssens², I. Ahmad², D.J. Blumanthal², M.P. Carpenter², S.M. Fischer², T.L. Khoo², D. Nisius², T. Lauritsen², M.A. Riley³, T.B. Brown³, D.J. Hartley³, and J. Simpson⁴, ¹Mississippi State University, Mississippi State, MS 39762, ²Argonne National Laboratory, Argonne, IL 60439, ³Florida State University, Tallahassee, FL 32306, and ⁴Daresbury Laboratory, Daresbury, WA44AD, England

Two experiments were performed using Gammasphere at Lawrence Berkeley National Laboratory using the reaction of ¹²⁴Sn(36S, xn) to study light Dy isotopes, with one using a thin self-supporting target and the other using a target with Au backing. Five and higher fold coincidence -ray events were recorded. Two triple-coincidence cubes gated by ¹⁵⁴Dy transitions were constructed. Several new bands have been established. A strongly coupled high-K structure, with dipole transitions and E2 crossover transitions, was observed to extend above spin 30 .. Another rotational band was populated weakly (total intensity less than 5%) but extended up to a spin tentatively assigned as 45 . Further data analysis is in progress.

10:00 Break

10:20 GRID GENERATION USING A SPRING ANALOGY

Lelia Faye Gary¹*, John Pormann², and John Board², ¹University of Mississippi, University, MS 38677, and ²Duke University, Durham, NC 27705

In previous work by Pormann, components of a computer program were written in Matlab to produce a useful spring grid model on which simulations could be done to accurately track cardiac activity. Pormann and Gary found generic equations which Matlab could solve to generate the desired grids. Both square and triangular grid models were used to compare the accuracy of each. After running the program and analyzing the results, it was determined that we needed to manipulate variables of the function in order to increase the accuracy of the grids. In most cases our data was consistent with our hypothesis that the triangular model was more accurate. It was determined that further research was needed to determine why the results varied in some cases. [This work was supported by the National Science Foundation/Engineering Research Center for Emerging Cardiovascular Technologies.]

10:40 SELECTION OF DREDGING EQUIPMENT

T.M. Parchure, Waterways Experiment Station, Vicksburg, MS 39180

Dredging consists of removal of material from the bottom of various water bodies. Dredging of natural sediments from the ocean, estuaries and rivers is an essential requirement for keeping the Nation's navigation channels open for traffic. For instance, periodic maintenance dredging is conducted over several miles along the Mississippi river for barge and ship traffic. Storage capacity of flood control and water supply reservoirs is reduced substantially due to sediment deposition. Dredging of such reservoirs is required for re-gaining the lost storage volume which is needed for their intended efficient functioning. The third situation consists of industrial ponds and lagoons where removal of material is necessary for their continued re-use for disposal of waste products. The material to be dredged from the above mentioned areas may be classified into two main categories: natural sediments, and industrial products. The natural sediments consist of a mixture of gravel, sand, silt, clay, and organic substances. Industrial waste products may consist of tailings from mining industry, rubber globules from tire industry, pulp and fiber waste from paper industry, molasses from sugar plant, unexploded ordnance at military installations and so on. Each material has specific physical properties which must be taken into account and each site has its own specific requirements. Hence selection of dredging equipment requires expert advice, such as that from the US Army Corps of Engineers where necessary evaluation is routinely done. A dozen types of dredges (mechanical, hydraulic, hopper, cutter, portable, etc.) and eight criteria of selection (material properties, volume, removal rate, location, water depth, etc.) are described in the paper.

11:00 THERMAL STUDIES OF COMPONENT MIXTURES OF THE NEMATIC LIQUID CRYSTAL E7

Nicole L. Gill*, Joe B. Whitehead, Jr., and Niekiletta Woullard, University of Southern Mississippi, Hattiesburg, MS 39406

The eutectic behavior of ternary mixtures is investigated both theoretically and experimentally for the components of E7. The reported components are K15 (4-pentyl-4'-cyanobiphenyl), K21 (4-heptyl-4'-cyanobiphenyl), M24 (4-hexyloxy-4'-cyanobiphenyl), and T15 (4-pentyl-4'-terphenyl). Previously, the binary mixtures were examined, and exhibited eutectic behavior only when T15 was a component. The leChatelier-Schroder-van Laar equations are used to predict the eutectic temperatures and to map the melting temperatures for non-eutectic mole fractions. Experimentally, the components are mixed in different mole fractions, and the melting behavior is examined using thermal optical microscopy and differential scanning calorimetry. Finally, the experimental data is compared to the theoretical data to determine which ternary mixtures exhibit eutectic behavior.

11:20 THE IMPORTANCE OF THE ANGLE OF INCIDENCE ON THE TRANSMITTED ACOUSTIC WAVE AT AN AIR / POROUS MEDIA INTERFACE

Will Johnson¹*, Craig J. Hickey², and James M. Sabatier², ¹Rhodes College, Memphis, TN 38112, and ²University of Mississippi, University, MS 38677

When an airborne acoustic wave is incident upon an air-filled porous material it is commonly assumed that the refracted wave travels normal to the interface. The justification for such an assumption is that the observed acoustic velocities in porous materials are lower than the acoustic velocity in air. If such an assumption is weak then the predicted distance which the wave propagates in the porous material is underestimated. Measurements of velocity and attenuation based on time of flight and amplitude decay are then larger than actual. An experiment was carried out to investigate the importance of the angle of incidence. The porous sample consisted of 1 mm glass beads. A 20 kHz acoustic signal was generated by a suspended loudspeaker. The angle of the loudspeaker was varied in 10 increments from normal incidence down to near grazing. Time of flight and amplitudes of the acoustic signal were measured at various depths using a probe microphone apparatus for each angle of incidence. The data shows some variation with angle of incidence but confirmation of the actual dependence will require further measurements.

11:40 Student Awards