Showing papers by "Missouri University of Science and Technology published in 2001"

Toxic Metals and Oxidative Stress Part I: Mechanisms Involved in Me-tal induced Oxidative Damage

Abstract: Toxic metals (lead, cadmium, mercury and arsenic) are widely found in our environment. Humans are exposed to these metals from numerous sources, including contaminated air, water, soil and food. Recent studies indicate that transition metals act as catalysts in the oxidative reactions of biological macromolecules therefore the toxicities associated with these metals might be due to oxidative tissue damage. Redox-active metals, such as iron, copper and chromium, undergo redox cycling whereas redox-inactive metals, such as lead, cadmium, mercury and others deplete cells major antioxidants, particularly thiol-containing antioxidants and enzymes. Either redox-active or redox-inactive metals may cause an increase in production of reactive oxygen species (ROS) such as hydroxyl radical (HO.), superoxide radical (O2.-) or hydrogen peroxide (H2O2). Enhanced generation of ROS can overwhelm cells intrinsic antioxidant defenses, and result in a condition known as “oxidative stress”. Cells under oxidative stress display various dysfunctions due to lesions caused by ROS to lipids, proteins and DNA. Consequently, it is suggested that metal-induced oxidative stress in cells can be partially responsible for the toxic effects of heavy metals. Several studies are underway to determine the effect of antioxidant supplementation following heavy metal exposure. Data suggest that antioxidants may play an important role in abating some hazards of heavy metals. In order to prove the importance of using antioxidants in heavy metal poisoning, pertinent biochemical mechanisms for metal-induced oxidative stress should be reviewed.

Wide-band E-shaped patch antennas for wireless communications

Abstract: This paper presents a novel single-patch wide-band microstrip antenna: the E-shaped patch antenna. Two parallel slots are incorporated into the patch of a microstrip antenna to expand it bandwidth. The wide-band mechanism is explored by investigating the behavior of the currents on the patch. The slot length, width, and position are optimized to achieve a wide bandwidth. The validity of the design concept is demonstrated by two examples with 21.2% and 32.3% bandwidths. Finally, a 30.3% E-shaped patch antenna, resonating at wireless communication frequencies of 1.9 and 2.4 GHz, is designed, fabricated and measured. The radiation pattern and directivity are also presented.

Mobile Commerce: Promises, Challenges and Research Agenda

Abstract: Advances in wireless technology increase the number of mobile device users and give pace to the rapid development of e-commerce using these devices. The new type of e-commerce, conducting transactions via mobile terminals, is called mobile commerce. Due to its inherent characteristics such as ubiquity, personalization, flexibility, and dissemination, mobile commerce promises businesses unprecedented market potential, great productivity, and high profitability. This paper presents an overview of mobile commerce development by examining the enabling technologies, the impact of mobile commerce on the business world, and the implications to mobile commerce providers. The paper also provides an agenda for future research in the area.

Shear Strengthening of Reinforced Concrete Beams with Near-Surface Mounted Fiber-Reinforced Polymer Rods

Abstract: The use of near-surface-mounted (NSM) fiber-reinforced polymer (FRP) rods is a promising technology for increasing flexural and shear strength of deficient reinforced concrete (RC) members. The structural behavior of RC elements strengthened with NSM FRP rods needs to be fully characterized. In this research, 8 full-size beams were tested. Carbon FRP deformed rods were used for shear strengthening. The variables examined in the shear tests were spacing of the rods, strengthening pattern, end anchorage of the rods, and presence of internal steel shear reinforcement. In this paper, performance of the tested beams and modes of failure are presented and discussed. Test results confirm that NSM FRP rods can be used to greatly increase the shear capacity of RC elements, with efficiency that varies depending on the tested variables. Results of the experimental tests are compared with the predictions of a simple model, showing reasonable agreement.

Methods for the determination of binding constants by capillary electrophoresis

Abstract: Apparent equilibrium constants for molecular association (e.g., association constants, binding constants, dissociation constants, partition coefficients) can be determined with a variety of different capillary electrophoresis (CE) approaches. In many cases, the investigated association behavior is between a smaller molecule or ion (i.e., the solute, drug, or analyte of interest) and a larger entity (e.g., proteins, micelles, polymers, chiral selectors such as cyclodextrins, etc.). Each experimental approach has advantages and disadvantages. Frequently, it is the nature of the system being evaluated that determines the optimal experimental approach. Six different CE-based techniques for evaluating binding constants are reviewed. Examples of each method, and recent references on its use are given.

Organizational change

Abstract: It has also been suggested that I only include information related to organizational change as it relates to for-profit organizations. When I suggest that there is also relevant information which relates to social change, typically, I hear the recommendation that I should focus on one or the other but not both. This appears to be a secondary manifestation of a belief that the dynamic of organizational change is directly linked to methodology. As of yet, I have not heard a credible argument as to how the dynamic of social change differs from corporate change. The main differences appear to be related to the goals of the desired change. Even suggesting a correlation between corporate and social change appears to challenge widely and, apparently, deeply held assumptions about the nature of organizational change.

Bond of Fiber-Reinforced Polymer Laminates to Concrete

Abstract: Fiber-reinforced polymer (FRP) laminates are being successfully used for strengthening existing reinforced concrete structures. The bond of FRP reinforcement to the concrete substrate is of great importance for the effectiveness of this technique. In this research, flexural test specimens were prepared to address some of the factors expected to affect bond such as bonded length, concrete strength, number of plies (stiffness), ply width, and, to a lesser extent, surface preparation. Experimental results are presented and discussed. A linear bond stress-slip relationship, along with a simple shear model for the evaluation of the slip modulus, is used to predict the strain distribution at moderate load levels. Lastly, expressions of the peeling load and the effective bond length are provided. A design equation is proposed for calculating the effective FRP ultimate strain to be used in design to account for bond-controlled failure.

Friction Stir Processing: A New Grain Refinement Technique to Achieve High Strain Rate Superplasticity in Commercial Alloys

Abstract: Friction stir processing is a new thermo-mechanical processing technique that leads to a microstructure amenable for high strain rate superplasticity in commercial aluminum alloys. Friction stirring produces a combination of very fine grain size and high grain boundary misorientation angles. Preliminary results on a 7075 Al demonstrate high strain rate superplasticity in the temperature range of 430-510 °C. For example, an elongation of >1000 % was observed at 490 °C and 1 × 10 -2 s -1 . This demonstrates a new possibility to economically obtain a superplastic microstructure in commercial aluminum alloys. Based on these results, a three-step manufacturing process to fabricate complex shaped components can be envisaged: cast sheet or hot-pressed powder metallurgy sheet + friction stir processing + superplastic forging or forming.

Three-Body Coulomb Problem Probed by Mapping the Bethe Surface in Ionizing Ion-Atom Collisions

Abstract: The three-body Coulomb problem has been explored in kinematically complete experiments on single ionization of helium by 100 MeV/u C(6+) and 3.6 MeV/u Au(53+) impact. Low-energy electron emission ( E(e)<150 eV) as a function of the projectile deflection theta(p) (momentum transfer), i.e., the Bethe surface [15], has been mapped with Delta theta(p)+/-25 nanoradian resolution at extremely large perturbations ( 3.6 MeV/u Au(53+)) where single ionization occurs at impact parameters of typically 10 times the He K-shell radius. The experimental data are not in agreement with state-of-the-art continuum distorted wave-eikonal initial state theory.

Integration of a StatCom and Battery Energy Storage

Abstract: The integration of an energy storage system, such as battery energy storage (BESS), into a FACTS device can provide dynamic decentralized active power capabilities and much-needed flexibility for mitigating transmission level power flow problems. This paper will introduce an integrated static synchronous compensator (StatCom)/BESS for the improvement of dynamic and transient stability and transmission capability, compare the performance of the different FACTS/BESS combinations, and provide experimental verification of the proposed controls on a scaled StatCom/BESS system.

Competition for working memory among writing processes.

Abstract: Narrative, descriptive, and persuasive texts were written by college students in longhand or on a word processor. Participants concurrently detected auditory probes cuing them to retrospect about whether they were planning ideas, translating ideas into sentences, or reviewing ideas or text at the moment the probes occurred. Narrative planning and longhand motor execution presumably were heavily practiced, freeing capacity for rapid probe detection. Spare capacity was distributed equally among all 3 processes, judging from probe reaction times, when planning demands were low in the narrative condition. When motor execution demands were low in the longhand condition, however, reviewing benefited more than planning. The results indicate that planning, translating, and reviewing processes in writing compete for a common, general-purpose resource of working memory.

An approach for development of damage-free drilling of carbon fiber reinforced thermosets

Abstract: A new comprehensive approach to select cutting parameters for damage-free drilling in carbon fiber reinforced epoxy composite material is presented. The approach is based on a combination of Taguchi's experimental analysis technique and a multi-objective optimization criterion. The optimization objective includes the contributing effects of the drilling performance measures: delamination, damage width, surface roughness, and drilling thrust force. A hybrid process model based on a database of experimental results together with numerical methods for data interpolation are used to relate drilling parameters to the drilling performance measures. Case studies are presented to demonstrate the application of this method in the determination of optimum drilling conditions for damage-free drilling in BMS 8-256 composite laminate. A process map based on the results is presented as a tool for drilling process design and optimization for the investigated tool/material combination.

Characterization of FRP Rods as Near-Surface Mounted Reinforcement

Abstract: The use of near surface mounted (NSM) fiber-reinforced polymer (FRP) rods is a promising technology for increasing flexural and shear strength of deficient reinforced concrete (RC) members. As this technology emerges, the structural behavior of RC elements strengthened with NSM FRP rods needs to be fully characterized. Given the variability of material properties and groove geometry, this requires that the tensile properties of the FRP rod and the mechanics of load transfer between NSM FRP rods and concrete be investigated. Tensile and bond tests on commercially available carbon FRP deformed rods for application as NSM reinforcement were carried out using test methods that are expected to become standards in North America. Three full-size beams, one control beam and two beams strengthened in shear with NSM FRP rods, were tested. Test results are presented and compared with the predictions of a simple design approach, showing reasonable agreement.

Antioxidant effect of taurine against lead-induced oxidative stress.

Abstract: Oxidative stress is proposed as a molecular mechanism in lead toxicity, which suggests that antioxidants might play a role in the treatment of lead poisoning. The present study was designed to investigate whether taurine has a beneficial effect both on Chinese hamster ovary (CHO) cells and on Fisher 344 (F344) rats following lead exposure. Therefore, oxidative stress parameters (glutathione, malondialdehyde levels, catalase, and glucose-6-phosphate dehydrogenase [G6PD] activities) of lead-exposed CHO cells and F344 rats were determined following taurine treatment. Taurine was found to be effective in (1) increasing glutathione levels that had been diminished by lead; (2) reducing malondialdehyde levels, an end-product of lipid peroxidation; (3) decreasing catalase and erythrocyte G6PD activity, which had been increased by lead exposure; and (4) improving cell survival of CHO cells. However, taurine had no effect on blood and tissue lead levels when 1.1 g/kg/day taurine was administered to F344 rats for 7 days, following 5 weeks of lead exposure (2,000 ppm lead acetate). As a result, taurine seems to be capable of fortifying cells against lead-induced oxidative attack without decreasing lead levels. Therefore, administration of taurine, accompanied by a chelating agent, might increase its effectiveness in the treatment of lead poisoning.

Unified Modeling Language: A Complexity Analysis

Abstract: Unified Modeling Language (UML) has emerged as the software industry’s dominant modeling language It is the de facto modeling language standard for specifying, visualizing, constructing, and documenting the components of software systems Despite its prominence and status as the standard modeling language, UML has its critics Opponents argue that it is complex and difficult to learn Some question the rationale of having nine diagramming techniques in UML and the raison d’Aatre of those nine techniques in UML Others point out that UML lacks a comprehensive methodology to guide its users, which makes the language even more convoluted A few studies on UML can be found in the literature However, no study exists to provide a quantitative measure of UML complexity or to compare UML with other object oriented techniques In this research, we evaluate the complexity of UML using complexity metrics The objective is to provide a reliable and accurate quantitative measure of UML complexity A comparison of the complexity metrical values of UML with other object-oriented techniques was also carried out Our findings suggest that each diagram in UML is not distinctly more complex than techniques in other OO methods But as a whole, UML is very complex - 2-11 times more complex than other OO methods

Chemical Durability and Structure of Zinc-iron Phosphate Glasses

Abstract: The chemical durability of zinc–iron phosphate glasses with the general composition (40−x)ZnO–xFe2O3–60P2O5 has been measured. The chemical durability and density of these glasses increase with increasing Fe2O3 content. Glasses containing more than 30 mol% Fe2O3 had an excellent chemical durability. The dissolution rate (DR), calculated from the weight loss in distilled water at 90 °C for up to 32 days, was ∼ 10 −9 g / cm 2 / min which is 100 times lower than that of window glass and 300 times lower than that of a barium ferro, aluminoborate glass. The structure and valence states of the iron ions in these glasses were investigated using Mossbauer spectroscopy, X-ray diffraction, infrared spectroscopy and differential thermal analysis. X-ray diffraction indicates that the local structure of the zinc–iron phosphate is related to the short range structures of crystalline Zn2P2O7, Fe3(P2O7)2 and Fe(PO3)3. Both Fe(II) and Fe(III) ions are present in all of these glasses. The presence of an Fe–O–P related band in the infrared (IR) spectra of the glasses containing more than 30 mol% Fe2O3 is consistent with their excellent chemical durability.

Iron redox equilibrium, structure and properties of zinc iron phosphate glasses

Abstract: Iron redox equilibrium, structure and properties were investigated for 40Fe2O3–60P2O5 (mol%) glasses melted at different temperatures. The Fe2+/(Fe2++Fe3+) ratio increased from 17% to 50% as the melting temperature changed from 1150°C to 1400°C. The equilibrium constant, K, for the reaction of Fe3+ being reduced to Fe2+ varied with temperature as lnK=9.40–1.58×104/T. The Raman and infrared spectra indicated that the basic iron pyrophosphate structure of the 40Fe2O3–60P2O5 (mol%) glasses did not change as the Fe2+/(Fe2++Fe3+) ratio changed. All of the properties did not change to any major degree with increasing the melting temperature. The molar volume decreased while the density increased with increasing Fe2+/(Fe2++Fe3+) ratio. It was found by DTA and XRD that two phases, Fe3(P2O7)2 and Fe4(P2O7)3, crystallized from the glass when the glass was heated in nitrogen. The crystallization behavior suggested that the amount of the crystal, Fe3(P2O7)2, may increase with increasing Fe2+/(Fe2++Fe3+) ratio, which supported the opinion that there are some structural similarities between the iron phosphate glass and the crystalline Fe3(P2O7)2 in terms of the iron coordination number and bonding of the phosphate groups. The decrease in dc resistivity and increase in dielectric constant and dielectric loss tangent, which occurred with increasing the Fe2+/(Fe2++Fe3+) ratio, were attributed to the increase of the electronic hopping from Fe2+ ions to Fe3+ ions.

North american design guidelines for concrete reinforcement and strengthening using frp: principles, applications, and unresolved issues

Abstract: Provided is a state of the art report on the North American use of FRP (fiber reinforced polymers) composites in concrete structures. The paper discusses the many reasons for the use FRP bars as internal reinforcement in concrete members to replace conventional rebars. The established fundamental principles for design and construction have been proposed to industry by the American Concrete Industry (ACI). Remarkable attention has focused on strengthening of concrete members with externally bonded FRP laminates or near surface mounted bars. ACI is presently in the process of finalizing the design and construction principles for use in practice. FRP materials are being used in some multi million dollar projects to strengthen parking garages, multi purpose convention centers, office buildings, and silos. An additional area for using these materials in repair/upgrade, the paper discusses the question of durability in relation to application for repair and upgrade.

Comparative Analysis of Regression and Artificial Neural Network Models for Wind Turbine Power Curve Estimation

Abstract: This paper examines and compares regression and artificial neural network models used for the estimation of wind turbine power curves. First, characteristics of wind turbine power generation are investigated. Then, models for turbine power curve estimation using both regression and neural network methods are presented and compared. The parameter estimates for the regression model and training of the neural network are completed with the wind farm data, and the performances of the two models are studied. The regression model is shown to be function dependent, and the neural network model obtains its power curve estimation through learning. The neural network model is found to possess better performance than the regression model for turbine power curve estimation under complicated influence factors.

Long-term working memory in text production.

Abstract: In reading and other high-level cognitive tasks, Ericsson and Kintsch (1995) proposed that the limited capacity of short-term working memory (STWM) is supplemented by long- term working memory (LTWM) for individuals with a high degree of domain-specific knowledge. In Experiment 1, college students (N = 80) wrote persuasive and narrative texts concerning baseball; domain-specific knowledge about baseball and verbal ability was assessed. The results showed that verbal ability and domain-specific knowledge independently affected writing skill, supporting the view that literacy depends on both knowledge sources and refuting one argument raised in support of the LTWM hypothesis. Experiment 2 (N = 42) replicated this outcome and tested the prediction that a high degree of domain-specific knowledge would lessen interference on a secondary task. The data supported the interference prediction, offering evidence that LTWM plays a role in the production of text.

Dual heuristic programming excitation neurocontrol for generators in a multimachine power system

Abstract: The design of nonlinear optimal neurocontrollers that replace the conventional automatic voltage regulators for excitation control of turbogenerators in a multimachine power system is presented in this paper. The neurocontroller design is based on dual heuristic programming (DHP), a powerful adaptive critic technique. The feedback variables are completely based on local measurements from the generators. Simulations on a three-machine power system demonstrate that DHP-based neurocontrol is much more effective than the conventional proportional-integral-derivative control for improving dynamic performance and stability of the power grid under small and large disturbances. This paper also shows how to design optimal multiple neurocontrollers for nonlinear systems, such as power systems, without having to do continually online training of the neural networks, thus avoiding risks of neural network instability.

Structure of sodium phosphate glasses containing Al2O3 and/or Fe2O3. Part I

Abstract: The relationship between the composition and structure for three series of glasses: Na2O–Al2O3–P2O5 (NAP); Na2O–Al2O3–Fe2O3–P2O5 (NAFP), and Na2O–Fe2O3–P2O5 (NFP) has been studied. The structural changes in the NAP, NAFP and NFP glasses have been investigated by Raman and by Raman difference spectroscopy (RDS). The Raman spectra show that the addition of Al2O3 content to sodium phosphate glasses has a different effect on the phosphate network than the addition of Fe2O3. With increasing Fe2O3 content up to 20 mol% the structure changes from the chain-like metaphosphate to the pyrophosphate structure. The iron ions play an important role in forming P–O–Fe bonds that strengthen the cross-bonding of shorter pyrophosphate chains. On the other hand, with increasing Al2O3 content up to 20 mol%, the sodium metaphosphate is replaced by aluminium metaphosphate where Al(OP)6 units cross-link phosphate chains. The addition of Fe2O3 to Al2O3 in phosphate glasses containing both Al2O3 and Fe2O3 (NAFP series), enhances the formation of pyrophosphate units because iron ions have stronger effect on the depolymerization of metaphosphate chains if compared to the aluminium ions.

Mechanical and Structural Properties of Phosphate Glasses

Abstract: Mechanical and structural properties of sodium (NAFP) and zinc (ZAFP) iron–aluminum–phosphate bulk glass and fibers have been investigated. Young's modulus of the fibers was measured by a three-point bending method while the strength was measured by a two-point bending method. In general, the tensile strength of the ZAFP fibers (4.2–7.2 GPa) was higher than the tensile strength of the NAFP fibers (2.8–4.2 GPa). After exposing the fibers to air for 10 days, the strength decreased by 15–34%. The structure of bulk glass as well as fibers, studied by Mossbauer and IR spectroscopy, was very similar for all the compositions studied.

A numerical comparison between the multiple-scales and finite-element solution for sound propagation in lined flow ducts

Abstract: An explicit, analytical, multiple-scales solution for modal sound transmission through slowly varying ducts with mean flow and acoustic lining is tested against a numerical finite-element solution solving the same potential flow equations. The test geometry taken is representative of a high-bypass turbofan aircraft engine, with typical Mach numbers of 0.5–0.7, circumferential mode numbers m of 10–40, dimensionless wavenumbers of 10–50, and both hard and acoustically treated inlet walls of impedance Z = 2 − i. Of special interest is the presence of the spinner, which incorporates a geometrical complexity which could previously only be handled by fully numerical solutions. The results for predicted power attenuation loss show in general a very good agreement. The results for iso-pressure contour plots compare quite well in the cases where scattering into many higher radial modes can occur easily (high frequency, low angular mode), and again a very good agreement in the other cases.

Convolutions of planar harmonic convex mappings

Abstract: Ruscheweyh and Sheil-Small proved that convexity is preserved under the convolution of univalent analytic mappings in K. However, when we consider the convolution of univalent harmonic convex mappings in , this property does not hold. In fact, such convolutions may not be univalent. We establish some results concerning the convolution of univalent harmonic convex mappings provided that it is locally univalent. In particular, we show that the convolution of a right half-plane mapping in with either another right half-plane mapping or a vertical strip mapping in is convex in the direction of the real axis. Further, we give a condition under which the convolution of a vertical strip mapping in with itself will be convex in the direction of the real axis