Showing papers by "Missouri University of Science and Technology published in 1997"

Adaptive critic designs

Abstract: We discuss a variety of adaptive critic designs (ACDs) for neurocontrol These are suitable for learning in noisy, nonlinear, and nonstationary environments They have common roots as generalizations of dynamic programming for neural reinforcement learning approaches Our discussion of these origins leads to an explanation of three design families: heuristic dynamic programming, dual heuristic programming, and globalized dual heuristic programming (GDHP) The main emphasis is on DHP and GDHP as advanced ACDs We suggest two new modifications of the original GDHP design that are currently the only working implementations of GDHP They promise to be useful for many engineering applications in the areas of optimization and optimal control Based on one of these modifications, we present a unified approach to all ACDs This leads to a generalized training procedure for ACDs

Review of Mechanics of Shape Memory Alloy Structures

Abstract: This article presents a review of constitutive theories, mechanics, and structural applications of shape memory alloys. Although these materials possess a number of unique features, this review is concerned with the shape memory effect and superelasticity, since they are most often discussed in the context of possible applications. The article begins with a discussion of these effects and a reference to a number of studies elucidating the properties of shape memory alloys. In the next section, a number of constitutive theories are listed and some recent theories are discussed in detail. The work related to numerous technological problems that arise in the process of manufacturing shape memory alloy structures is considered. Structural problems of shape memory structures, such as buckling, vibration, acoustic control, etc are discussed. The work related to development and design of shape memory sensors and actuators is also reviewed. Finally, some applications of shape memory alloy actuators, particularly those in the aerospace and medical fields, are considered. This review article contains 195 references.

Properties and Structure of Sodium-iron Phosphate Glasses

Abstract: Selected properties of phosphate glasses, containing from 14 to 43 mol% Fe2O3 and up to 13 mol% Na2O, have been measured. With increasing Fe2O3 and Na2O content, the density and dilatometric softening temperature increased, whereas, the thermal expansion coefficient and dissolution rate in water or saline at 90°C decreased. Glasses containing more than 25 mol% Fe2O3 had an exceedingly good chemical durability. Their dissolution rate at 90°C in distilled water or in saline solution was up to 100 times lower than that of window glass. Mossbauer and X-ray photoelectron spectroscopy indicate that iron(II) and iron(III) were both present in the glasses and the chemical durability improved with increasing iron(III) concentration. The outstanding chemical durability of these glasses was attributed to the replacement of POP bonds by more chemically resistant POFe(II) and POFe(III) bonds.

Information retrieval on the World Wide Web

Abstract: Effective search and retrieval are enabling technologies for realizing the full potential of the Web. The authors examine relevant issues, including methods for representing document content. They also compare available search tools and suggest methods for improving retrieval effectiveness.

Structural features of iron phosphate glasses

Abstract: The structures and valence states of iron ions in several iron phosphate glasses with batch compositions similar to 40Fe2O3-60P2O5 (mol%) have been investigated using Mossbauer spectroscopy, X-ray absorption fine-structure spectroscopy (XAFS), X-ray photoelectron spectroscopy (XPS), differential thermal (DTA) and thermo-gravimetric (TGA) analysis and X-ray and neutron diffraction. Mossbauer spectra show that a redox equilibria corresponding to an Fe(II)/[Fe(II) + Fe(III)] ratio of 0.2–0.4 is reached under processing conditions described in this paper. Even though the valence state of iron ions in the glass appears to be insensitive to the oxygen content in the melting atmosphere, the Fe(II) content can be increased within the observed range of redox equilibria by increasing the partial pressure of a reducing gas in the melting atmosphere. Large amounts of Fe(II), Fe(II)/[Fe(II) + Fe(III)] ≥ 0.4, appear to be detrimental to the glass-forming ability of the iron phosphate melts. The local structure of the iron phosphate glasses appears to be related to the short range structure of crystalline Fe3(P2O7)2 which consists of a network of (Fe3O12)−16 clusters. These clusters consist of one iron(II) ion and two iron(III) ions in sixfold coordination with near-neighbor oxygen ions. The (Fe3O12)−16 clusters are interconnected via (P2O7)−4 groups. Compared to other phosphate glasses, the proposed structure for iron phosphate glasses contain a smaller number of POP bonds, a feature which is believed to be responsible for the unusually good chemical durability of iron phosphate glasses.

Mathematical Modelling of the Primary and Secondary Drying Stages of Bulk Solution Freeze-Drying in Trays: Parameter Estimation and Model Discrimination by Comparison of Theoretical Results With Experimental Data

Abstract: A mathematical model was constructed and solved in order to describe quantitatively the dynamic behavior of the primary and secondary drying stages of the freeze-drying of pharmaceuticals in trays. The theoretical results were compared with the experimental data of the freeze-drying of skim milk, and the agreement between the experimental data and the theoretical results is good. Detailed model calculations have indicated that the contribution of the removal of hound (unfrozen) water to the total mass flux of the water removed during primary drying, is not significant. For this reason, it was found that one could not

Modified discrete ordinates solution of radiative transfer in two-dimensional rectangular enclosures

Abstract: A modified discrete ordinates solution is developed for radiative transfer in a two-dimensional rectangular enclosure which contains an absorbing, emitting and isotropically scattering medium. Uniform and non-uniform diffuse loadings on the top boundary are considered. The intensity is broken into direct and diffuse components. The direct component is determined analytically, and the diffuse transport equation is solved numerically by conventional discrete ordinates procedure. Results are presented for various aspect ratios, media extinction properties, and loading parameters. The standard discrete ordinates solution exhibits anomalies in the flux leaving the bottom which are attributed to ‘ray-effects’. Large errors are observed when the aspect ratio is small. Numerical results obtained using the modified discrete ordinates scheme compare well with benchmark solutions and show no anomalies in the bottom flux.

Capillary electrophoretic enantioseparations using macrocyclic antibiotics as chiral selectors

Abstract: Macrocyclic antibiotics are the newest class of chiral selector used in capillary electrophoresis (CE) enantioseparations. Two basic types of compounds have proven to produce useful enantioseparations. They are the ansa compounds and the glycopeptides. The ansa compounds best resolve basic or cationic racemates while the glycopeptides best resolve acidic or anionic analytes. The structure and use of these chiral selectors are discussed. The factors affecting separation and the separation mechanism are considered as well.

Application of conducting polymers in corrosion protection

Abstract: The use of oxides, such as chromates, is highly effective in corrosion protection. Scientists are looking at alternative materials to replace environmentally hazardous materials, e.g., chromates. One of the group of materials identified as corrosion inhibiting are intrinsically conducting polymers. This paper focuses on the use of ICPs as a possible corrosion inhibitive substance. This paper also reviews literature on the research of different groups on the use of polyaniline and other conducting polymers as corrosion inhibitors. Intrinsically conducting polymers, especially poly-aniline, are being studied with great interest. Studies indicate that they have the potential of replacing some of the currently available materials.

Observation of upper tropospheric sulfur dioxide‐ and acetone‐pollution: Potential implications for hydroxyl radicaland aerosol formation

Abstract: Aircraft-based measurements of sulfur dioxide, acetone, carbon dioxide, and condensation nuclei (CN) were made over the north-eastern Atlantic at upper tropospheric altitudes, around 9000 m. On October 14, 1993, strong SO2- and acetone-pollution (both up to 3 ppbv) were observed, which were accompanied by a CO2-enhancement of up to 6 ppmv, and large CN-concentrations of up to about 1500 cm−3 (for radii ≥ 6 nm). CN, excess CO2, and to a lesser degree also acetone, were positively correlated with SO2. Air mass trajectory analyses indicate, that most of the air masses encountered by our aircraft originated from the polluted planetary boundary layer of the North-Eastern U. S. approximately 4–5 days prior to our measurements, and that polluted boundary layer air experienced fast vertical transport to the upper troposphere as well as horizontal transport across the Atlantic. From our data we conclude, that in the polluted air mass around 9000 m altitude HOx-formation, photochemical SO2-conversion to gaseous H2SO4, and eventually also CN-formation by homogeneous bimolecular (H2SO4-H2O) nucleation may have taken place with enhanced efficiency.

Thrust Losses in Hypersonic Engines Part 1: Methodology

Abstract: Expressions for the thrust losses of a scramjet engine are developed in terms of irreversible entropy increases and the degree of incomplete combustion. A method is developed that allows the calculation of the lost engine thrust or thrust potential caused by different loss mechanisms within a given e owe eld. This method allows the performance-based assessment of the trade between mixing enhancement and resultant increased e ow losses in scramjet combustors. An engine effectiveness parameter for use in optimization of engine components is dee ned in terms of thrust losses.

Adaptive Shape Control of Composite Beams with Piezoelectric Actuators

Abstract: This paper deals with adaptive shape control of laminated composite beams with integrated piezoelectric actuators. The mathematical model is based on a higher order shear deformation theory and accounts for lateral strains. A constrained optimization algorithm has been implemented to calculate the optimal open loop actuator voltages which minimize the error function. A closed loop feedback system is developed to maintain the desired shape even in the presence of quasistatically varying unknown loads. A computationally efficient finite element code is developed for performing the numerical calculations. The effect of stacking sequence and boundary conditions on the actuator voltages for both open loop and closed loop systems is examined. It is observed that the adapted shape achieved by using a full sensor feedback and partial sensor feedback are nearly the same. Thus position sensors at all locations are not required for closed loop shape control.

Ionization of Helium in the Attosecond Equivalent Light Pulse of 1 GeV/Nucleon U{sup 92+} Projectiles

Abstract: Single and double ionization of helium by 1GeV/nucleon U{sup 92+} impact was explored in a kinematically complete experiment. The relativistic ion generates a subattosecond (10{sup {minus}18} s ) superintense (I{gt}10{sup 19} W/cm {sup 2} ) electromagnetic pulse, which is interpreted as a field of equivalent photons (Weizs{umlt a}cker-Williams method). Cross sections, the emission characteristics of ions and electrons as well as momentum balances, are quantitatively discussed in terms of photoionization of the atom in this broadband, ultrashort virtual photon field. {copyright} {ital 1997} {ital The American Physical Society}

L.E.O.: The Incredible Story of the World's First Business Computer

Abstract: From the Publisher: This book takes you behind the scenes at the creation of the world's first business computer - the precursor to every computer in every office around the world. It places you in the midst of a dynamic group of creative people - visionaries who were the first to recognize the potential and harness the power of computing for business purposes. Written by the real-life participants in these exciting events, it "depicts the scene frankly, warts and all," as David Caminer, the pioneering team leader, writes in his preface. LEO reveals the strange and remarkable tale of how Lyons - a venerable tea-and-cake company - bred, incubated, and hatched that history-making business computer. In 1951, less than 2 years after the project was initiated, LEO went on-line as the world's first business computer. A forerunner to the IBM mainframes, LEO was the first computer to run a payroll, the first to perform inventories, and the first to track product distribution - as well as the first to calculate the blending of fine, flavorful, and cost-effective cups of tea.

New approaches to nesting rectangular patterns

Abstract: In this study, two approaches are explored for the solution of the rectangular stock cutting problem: neuro-optimization, which integrates artificial neural networks and optimization methods; and genetic neuro-nesting, which combines artificial neural networks and genetic algorithms. In the first approach, an artificial neural network architecture is used to generate rectangular pattern configurations, to be used by the optimization model, with an acceptable scrap. Rectangular patterns of different sizes are selected as input to the network to generate the location and rotation of each pattern after they are combined. A mathematical programming model is used to determine the nesting of different sizes of rectangular patterns to meet the demand for rectangular blanks for a given planning horizon. The test data used in this study is generated randomly from a specific normal distribution. The average scrap percentage obtained is within acceptable limits. In the second approach, a genetic algorithm is used to generate sequences of the input patterns to be allocated on a finite width with infinite-length material. Each gene represents the sequence in which the patterns are to be allocated using the allocation algorithm developed. The scrap percentage of each allocation is used as an evaluation criterion for each gene for determining the best allocation while considering successive generations. The allocation algorithm uses the sliding method integrated with an artificial neural network based on the adaptive resonance theory (ART1) paradigm to allocate the patterns according to the sequence generated by the genetic algorithm. It slides an incoming pattern next to the allocated ones and keeps all scrap areas produced, which can be utilized in allocating a new pattern through the ART1 network. If there is a possible match with an incoming pattern and one of the scrap areas, the neural network selects the best match area and assigns the pattern. Both approaches gave satisfactory results. The second approach generated nests having packing densities in the range 95–97%. Improvement in packing densities was possible at the expense of excessive computational time. Parallel implementation of this unconventional approach could well bring a quick and satisfactory solution to this classical problem.

Evaluation of Performance Loss Methods for High-Speed Engines and Engine Components

Abstract: A comparative study of high-speed engine performance assessment techniques based on exergy (available work) and thrust potential (thrust availability) is summarized. Simple one-dimensional  owŽ elds utilizing Rayleigh heat addition and friction are used to demonstrate the inability of conventional exergy techniques to predict engine component performance, aid in component design, or accurately assess  ow losses. The thrust-based method yields useful information in all of these categories for these  ows. The conventional deŽ nition of exergy includes work that is inherently unavailable to an aerospace Brayton engine. An engine-based exergy is developed that accurately accounts for this inherently unavailable work; performance parameters based on this quantity yield design and loss information identical to the thrustbased method.

A backward Monte Carlo study of the multiple scattering of a polarized laser beam

Abstract: A backward Monte Carlo estimator is developed to describe the multiple scattering of a polarized, narrow light beam by a plane-parallel medium. The case of a right circularly polarized beam is analyzed in this paper. Results indicate that the diffuse light field is partially polarized even at significant optical radii from the incident light beam. The degree of polarization of the diffuse light field is dependent on the optical thickness of the medium and the size parameter of the scatterers.

Modelling Fracture in Laminated Architectural Glass Subject to Low Velocity Impact

Abstract: Standard finite element wave propagation codes are useful for determining stresses caused by colliding bodies; however, their applicability to brittle materials is limited because an accurate treatment of the fracture process is difficult to model. This paper presents a method that allows traditional wave propagation codes to model low velocity, small missile impact in laminated architectural glass such as that which occurs in severe windstorms. Specifically, a method is developed to model typical fractures that occur when laminated glass is impacted by windborne debris. Computational results of concern to architectural glazing designers are presented.

Thrust losses in hypersonic engines part 2 : applications

Abstract: The methodology developed in Part 1 of this investigation (Riggins, D. W., McClinton, C. R., and Vitt, P. H., ‘‘Thrust Losses in Hypersonic Engines Part 1: Methodology,’’ Journal of Propulsion and Power, Vol. 13, No. 2, 1997, pp. 281 – 287) for the identiŽ cation and evaluation of the thrust losses in a scramjet engine is applied to one-dimensional scramjet engine  ows with coupled loss mechanisms. Thrust and thrust potential losses are related directly to increases in irreversible entropy caused by friction, heat transfer, mixing, nonequilibrium reaction, and shocks. This method is extended to enable the evaluation of thrust losses in multidimensional  ows. The fundamental relationship between performance assessment utilizing multidimensional  owŽ elds and cycle analysis performance prediction is shown and discussed.

Modeling and retrieving images by content

Abstract: A content-based image retrieval system (CBIR) is required to effectively utilize information from image databases. Content-based retrieval is characterized by the ability of the system to retrieve relevant images based on their visual and semantic contents rather than by using atomic attributes or keywords assigned to them. In this paper, we provide a taxonomy for approaches to image retrieval and describe their characteristics and limitations. We examined a number of image database applications to discover their retrieval requirements and to structure the requirements from a domain-independent perspective. This study enabled us to provide a taxonomy for image attributes and to propose a number of generic query operators. These operators are adequate to realize CBIR in a number of diverse applications. We propose a novel system architecture for CBIR that supports the generic query operators. The architecture is structured in a way to enable applications to inherit only those query operators that are useful in the domain. We have developed a partial prototype implementation of this architecture. The versatility and effectiveness of the architecture is demonstrated by configuring the prototype implementation for two image retrieval applications: realtors information system and face retrieval system. The first application is for real estate marketing and the other is for law enforcement and criminal investigation.

Numerical Simulations of Full-Scale Corroded Pipe Tests With Combined Loading

Abstract: The ANSI/ASME B31G guideline has been useful to pipeline operators in assessing the integrity of corroded line pipe. Because large safety margins have had to be incorporated, the guidelines can be excessively conservative, which in turn can force costly repairs and replacements that may not actually be necessary. On the other hand, because the current guidelines consider only pressure loading and neglect bending and axial compression, they could give nonconservative failure predictions when combined loading exists. Therefore, a study was initiated to develop a theoretically sound methodology for assessing the integrity of corroded line pipe subjected to combined loading. A key step in the successful application of this methodology is the development of sophisticated three-dimensional finite element procedure that can accurately simulate full-scale pipe tests under conditions of combined loading. This paper describes thirteen full-scale failure tests on artificially corroded pipes subjected to simultaneous internal pressure, bending, and longitudinal compression and presents a detailed account of the finite element analysis procedure that was developed to simulate these tests numerically. Additional finite element analyses that were conducted to investigate the effect of key parameters on failure, and to expand the corroded pipe failure database, are also discussed.