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Showing papers by "Missouri University of Science and Technology published in 1998"


Journal ArticleDOI
TL;DR: Based on extensive computer simulations of a 3D disorder model that includes such correlations, this article presented a new formula for analyzing experiments that accurately describes transport in disordered organic materials. But their model neglects spatial correlations due to chargedipole interactions, even though such correlations have been shown to explain the universal electric field dependence observed in these systems.
Abstract: The transport of photoinjected charges in disordered organic films is often interpreted using a formula based on a Gaussian disorder model (GDM) that neglects spatial correlations due to chargedipole interactions, even though such correlations have recently been shown to explain the universal electric field dependence observed in these systems. Based on extensive computer simulations of a 3D disorder model that includes such correlations, we present a new formula for analyzing experiments that accurately describes transport in these materials. [S0031-9007(98)07626-1]

581 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a review of the current research on shear strengthening with FRP and propose design algorithms to compute the contribution of FRP to the shear capacity of RC flexural members.
Abstract: Fiber reinforced polymer (FRP) materials are continuing to show great promise for use in strengthening reinforced concrete (RC) structures. These materials are an excellent option for use as external reinforcing because of their light weight, resistance to corrosion, and high strength. Externally bonded FRP sheets have been used to increase moment capacity of flexural members and to improve confinement in compression members. Investigations into the use of externally bonded FRP sheets for use in shear strengthening have also been conducted and have shown this to be a viable strengthening method. The objective of this study is to review the current research on shear strengthening with FRP and propose design algorithms to compute the contribution of FRP to the shear capacity of RC flexural members. Methods for computing the shear capacity based on the stress level to cause tensile fracture of the FRP sheet (which may be less than ultimate due to stress concentrations) and based on delamination of the sheet from the concrete surface are presented. Areas which have the potential for further development are also discussed.

570 citations


Journal ArticleDOI
TL;DR: In this article, a simulated high level waste, whose major components were 54.6 wt% Na2O, 14.9 wt%, P2O5 and 8.3 wt%), was successfully vitrified into iron phosphate wasteforms whose chemical durability was equivalent to that of borosilicate glass wasteforms.
Abstract: Up to 40 wt% of a simulated high level waste, whose major components were 54.6 wt% Na2O, 14.9 wt% P2O5 and 8.3 wt% Fe2O3, was successfully vitrified into iron phosphate wasteforms whose chemical durability was equivalent to that of borosilicate glass wasteforms. Because of their high fluidity, the iron phosphate wasteforms could be melted in as little as 30 min at temperatures between 1015°C and 1200°C. The addition of 3–7 wt% CaF2 to the batch decreased the melting time and temperature, by as much as 100°C, and improved the chemical durability, especially for crystallized iron phosphate wasteforms. Iron phosphate wasteforms are concluded to be a practical alternative for vitrifying those nuclear wastes not well suited for borosilicate glasses.

324 citations


01 Jan 1998
TL;DR: In this article, the use of numerical elastic buckling solutions for the entire member, investigated as an alternative to current practice, was found that a "direct strength" approach is a reliable alternative.
Abstract: Current design of cold-formed steel members is unduly complicated. Part of this complication arises from the need to perform elastic buckling calculations by hand. Also, complications occur in determining the effective width and resulting effective properties of members. Further, as cross-sections become more optimized (e.g., through the introduction of longitudinal stiffeners) both the elastic buckling and effective width calculations become markedly more complex. In order to investigate alternatives to current design a large amount of experimental data on flexural members of varying geometry is collected. The use of numerical elastic buckling solutions for the entire member, is investigated as an alternative to current practice. Employing strength curves on the entire member, similar to the effective width strength curves for an element, it is found that a "direct strength" approach is a reliable alternative to current design. Such an approach leads to complete flexibility in cross-section geometry, thus greatly increasing the ability to optimize cold-formed steel members. Conservative limitations of the direct strength approach are also addressed.

283 citations


Journal ArticleDOI
TL;DR: In vivo evidence is provided supporting the hypothesis that lead induces oxidative stress in RBCs, which is reversible by treatment with a thiol antioxidant (NAC), as well as a chelating agent (succimer).

245 citations


Journal ArticleDOI
TL;DR: In this paper, the negative impedance instability of the DC link was examined and a readily implemented albeit nonlinear control strategy was proposed to mitigate this potential problem. But, the proposed strategy is not suitable for a large number of applications, such as locomotives and ships.
Abstract: Induction motor based electric propulsion systems can be used in a wide variety of applications including locomotives, hybrid electric vehicles, and ships. Field oriented control of these drives is attractive since it allows the torque to be tightly and nearly instantaneously controlled. However, such systems can be prone to negative impedance instability of the DC link. This paper examines this type of instability and sets forth a readily implemented albeit nonlinear control strategy to mitigate this potential problem.

181 citations


Journal ArticleDOI
TL;DR: The ristocetin A CSP appeared to be complimentary to other glycopeptide CSPs (i.e., vancomycin and teicoplanin).

155 citations


Journal ArticleDOI
TL;DR: The origin of NOx in the upper troposphere over the central United States was examined using aircraft observations obtained during the SUCCESS campaign in April-May of 1996 as mentioned in this paper.
Abstract: The origin of NOx in the upper troposphere over the central United States is examined using aircraft observations obtained during the SUCCESS campaign in April–May of 1996 Correlations between NOy (sum of NOx and its oxidation products) and CO at 8–12 km altitude indicate that NOx originates primarily from convective transport of polluted boundary layer air Lightning and aircraft emissions appear to be only minor sources of NOx Chemical steady state model calculations constrained by local observations of NO underestimate the measured NOx/NOy concentration ratio at 8–12 km altitude by a factor of two on average The magnitude of the underestimate is correlated with concentrations of condensation nuclei, which we take as a proxy for the age of air in the upper troposphere We conclude that the NOx/NOy ratio is maintained above chemical steady state by frequent convective injections of fresh NOx from the polluted boundary layer and by the long lifetime of NOx in the upper troposphere (5–10 days) In contrast to previous studies, we find no evidence for fast heterogeneous recycling from HNO3 to NOx in the upper troposphere

151 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that during their combustion, halogenated flame retardants can produce dibenzop-dioxins and dibenzo-furans.
Abstract: Plastic materials have been associated with electric and electronic applications since the early days of the electrical industry. Plastics can amount up to 30% of the scrap mass. Generally, they contains flame retardants such as halogenated compounds which can lead to the formation of different toxic products. Recycling, incineration and landfilling are the current methods used to treat these plastics. They also can be used as combustibles in some metallurgical processes. However, during their combustion, halogenated flame retardants can produce dibenzop-dioxins and dibenzo-furans.

144 citations


Journal ArticleDOI
TL;DR: It is found that heat input control that runs the process close to the melting and scorch temperature constraints yields faster drying times, and more uniform distributions of temperature and concentration of bound water at the end of the secondary drying stage.
Abstract: A rigorous unsteady state and spatially multidimensional model is presented and solved to describe the dynamic behavior of the primary and secondary drying stages of the lyophilization of a pharmaceutical product in vials for different operational policies. The results in this work strongly motivate the aggressive control of freeze drying and it is found that heat input control that runs the process close to the melting and scorch temperature constraints yields (i) faster drying times, and (ii) more uniform distributions of temperature and concentration of bound water at the end of the secondary drying stage.

141 citations


Journal ArticleDOI
TL;DR: The isocratic retention of enantiomers of beta-methyl amino acids was studied on a teicoplanin-containing chiral stationary phase at different temperatures and at different mobile phase compositions, using the reversed-phase mode to promote an understanding of the thermodynamic driving forces for retention.

Journal ArticleDOI
TL;DR: In this paper, the toxicity of nicotine enantiomers as well as their ability to induce oxidative stress in an in vitro model using Chinese hamster ovary (CHO) cells.


Journal ArticleDOI
TL;DR: A glycopeptide antibiotic, teicoplanin, was used as chiral stationary phase for the high-performance liquid chromatographic (HPLC) separation of enantiomers of more than 30 unnatural amino acids.

Journal ArticleDOI
TL;DR: In this article, a pore network model is constructed to represent the porous structure in a column packed with porous chromatographic particles and the results show that the intraparticle interstitial velocity and pore diffusivity increase significantly as the value of the pore connectivity, nT, increases.

Journal ArticleDOI
TL;DR: Zhou et al. as discussed by the authors proposed a method for Chinese Acad Sci, Inst Met Res, 72 Wenhua Rd, Shenyang 110015, Peoples R China, USA.

Journal ArticleDOI
TL;DR: The use of this CSP and the optimization of separations on it are discussed, and avoparcin appears to be a useful addition to this family of CSPs.

Journal ArticleDOI
TL;DR: The effect of three aliovalent cations, Nb 5+, La 3+ and Co 2+, on the grain growth kinetics of nearly fully dense BaTiO 3 (Ba/Ti atomic ratio = 1.001) was measured in O 2 at 1300 °C and for dopant concentrations of up to 1.25 atomic per cent (at%).
Abstract: The effect of three aliovalent cations, Nb 5+ , La 3+ and Co 2+ , on the grain growth kinetics of nearly fully dense BaTiO 3 (Ba/Ti atomic ratio = 1.001) was measured in O 2 at 1300 °C and for dopant concentrations of up to 1.25 atomic per cent (at%). For the donor cation Nb 5+ , the boundary mobility initially increased with cation concentration but then decreased markedly above a doping threshold of 0.3–0.5 at%. The boundary mobility of the BaTiO 3 doped with the acceptor cation Co 2+ decreased monotonically with dopant concentration. At a cation concentration of 0.75 at%, the boundary mobility was reduced by a factor of approximately 25, 10 and 50 times by Nb 5+ , La 3+ and Co 2+ , respectively. A major role of the dopants is seen to be their ability to influence the boundary mobility. The effects of the dopants on the boundary mobility are discussed in terms of the defect chemistry and the space-charge concept.

Journal ArticleDOI
TL;DR: In this paper, the phase composition and resistivity of the films can be controlled by varying the applied current density, and the resistivity can be varied over ten orders of magnitude.
Abstract: Layered nanostructures of copper metal and cuprous oxide are electrodeposited from alkaline solutions of Cu(II) lactate at room temperature. No subsequent heat treatment is necessary to effect crystallization. The electrode potential spontaneously oscillates during constant-current deposition. At a fixed current density the oscillation period decreases as either the pH or temperature is increased. The oscillations are periodic in stirred solution, but show period doubling and evidence of quasi-periodic or chaotic behavior in unstirred solution. The phase composition and resistivity of the films can be controlled by varying the applied current density. The resistivity of the films can be varied over ten orders of magnitude. Scanning electron microscopy shows that the films are layered.

Journal ArticleDOI
TL;DR: In this article, it was shown that the exponential dichotomy of a strongly continuous evolution family on a Banach space is equivalent to the existence and uniqueness of continuous bounded mild solutions of the corresponding inhomogeneous equation.
Abstract: We prove that the exponential dichotomy of a strongly continuous evolution family on a Banach space is equivalent to the existence and uniqueness of continuous bounded mild solutions of the corresponding inhomogeneous equation. This result addresses nonautonomous abstract Cauchy problems with unbounded coefficients. The technique used involves evolution semigroups. Some applications are given to evolution families on scales of Banach spaces arising in center manifolds theory.

Journal ArticleDOI
TL;DR: Laser-induced polymer surface modification is an emerging technique for imparting functional species to polymer surfaces as discussed by the authors, which has several benefits over other surface modification methods and new applications are being explored.
Abstract: Laser-induced polymer surface modification is an emerging technique for imparting functional species to polymer surfaces. Laser technology, the important criteria in selecting an appropriate laser system and the principle of laser-assisted polymer surface modification are briefly discussed. Laser treatments have several benefits over other surface modification methods and new applications are being explored. Recent technological advances in laser surface modification and current applications of this technique pertaining to commonly used food packaging polymers are presented with state-of-the-art examples. Finally, the future applications of laser surface modified polymers in food packaging are examined and additional research requirements identified.

Journal ArticleDOI
TL;DR: In this paper, the authors presented an economic analysis of three hydrogen liquefaction systems with an associated cost comparison, taking into account the energy cost, operation and maintenance, and fixed charges on capital investment.

Journal ArticleDOI
28 Sep 1998-Talanta
TL;DR: It is shown that partitioning interactions and hydrogen bonding interactions between the hydroxyl groups of the stationary phase and those of the sugars are the two possible mechanisms responsible for sugar retention.

Journal ArticleDOI
TL;DR: A specific three-body complex involving simultaneous, dual inclusion complex formation can be used to explain both the enhanced and diminished enantioselectivities observed when 18-crown-6 is added to the run buffer.

Journal ArticleDOI
TL;DR: In this article, the effect of bath temperature, bath pH and current density on the compositon, grain size, surface texture and surface morphology of the electrodeposited polycrystalline copper (I) oxide films were investigated.
Abstract: Polycrystalline copper (I) oxide films were deposited on stainless steel substrate by galvanostatic electrodeposition method and were characterized by Xray diffraction and scanning electron microscopy. The effect of bath temperature, bath pH and current density on the compositon, grain size, surface texture and surface morphology of the electrodeposited films were investigated. The films deposited at low bath pH (less than or equal to 7) consisted of copper (I) oxide and metallic copper; while the films deposited at bath pH between 8 and 12 and bath temperature of 60 degrees C were pure copper (I) oxide. The preferred orientation of the copper (I) oxide films depended on the relative growth rate of (111) and (200) faces and could be controlled by adjusting the bath pH and/or the cathodic current density. (100)-oriented copper (1) oxide films could be deposited at pH=9 and current densities in the range of 0.25-1 mA/cm(2) while (111)-oriented films could be prepared at pH=12 or at pH=9 using the current densities between 1.5-2.5 mA/cm(2). Computer simulated crystallite shapes showed that the crystal shape changed from octahedral for (100)-oriented film to trucated pyramids and cubs for (111)-oriented film. And they were approved by scanning electron microscopy.

Journal ArticleDOI
TL;DR: In this article, a Pareto GA is proposed to locate the optimal set of a multi-objective optimization problem, where the fitness of each individual is defined according to its non-nominal property.
Abstract: Genetic algorithms (GAs) have the characteristic of maintaining a population of solutions and can search in a parallel manner for many nondominated solutions. These features coincide with the requirement of seeking a Pareto optimal set in a multiobjective (multicriteria, vector) optimization problem. The rationale for multiobjective optimization via GAs is that at each generation, the fitness of each individual is defined according to its nondominated property. Because nondominated individuals are assigned the highest fitness values, the convergence of a population will go to the nondominated zone: the Pareto optimal set. Based on this concept, a Pareto GA, whose goal is to locate the Pareto optimal set of a multiobjective optimization problem, is developed. In this GA, to avoid missing Pareto optimal points during evolutionary processes, a new concept called Pareto-set filter is adopted. At each generation, the points of rank 1 are put into the filter and undergo a nondominated check. In addition, a niche technique is provided to prevent genetic drift in population evolution. This technique sets a replacement rule for reproduction procedures. For a constrained optimization problem, a revised penalty function method is introduced to transfer a constrained problem into a nonconstralned one. The transferred function of a point contains information on a point's status (feasible or infeasible), position in a search region, and distance to the Pareto optimal set Two multiobjective optimization examples, a 25-bar space truss optimal design (objectives: structural weight and virtual work, constraints: stresses) and a four-bar pyramid truss with control system (objectives: structural weight and control effort, constraints: closed-loop frequencies) are provided to demonstrate analysis procedures of the proposed Pareto GA.

Journal ArticleDOI
TL;DR: The enantiomeric composition of nicotine in 18 smokeless tobaccos, 3 strains of tobacco leaf, 8 pharmaceutical products, and 4 commercial reagents was determined and it appears that (R)-(+)-nicotine may be considered one of the five most common alkaloids in tobacco products.

Journal ArticleDOI
TL;DR: In this article, the results of a study of the structure and electrical properties of nanocrystalline SrCe0 95Yb0 05O3 proton conducting thin films are presented.
Abstract: The results of a study of the structure and electrical properties of nanocrystalline SrCe0 95Yb0 05O3 proton conducting thin films are presented. The relationship between the electrical transport and hydrogen partial pressure has been determined and correlated with microstructure. Nanostructured SrCe0.95Yb0.05O3 films possess greatly enhanced conductivity due to interfacial effects related to the influence of surfaces and grain boundaries. The opportunity to use these films for gas sensors is discussed and their characteristics are presented.

Journal ArticleDOI
TL;DR: In this paper, the authors compared the seismic and radar data and using the geotechnical data as ground truth, they associated the deepest coherent event in the USAF Groundwater Remediation Field Laboratory located at Dover Air Force Base, Dover, Delaware.
Abstract: In 1995 and 1996, researchers associated with the US Air Force’s Phillips and Armstrong Laboratories took part in an extensive geophysical site characterization of the Groundwater Remediation Field Laboratory located at Dover Air Force Base, Dover, Delaware. This field experiment offered an opportunity to compare shallow‐reflection profiling using seismic compressional sources and low‐frequency ground‐penetrating radar to image a shallow, unconfined aquifer. The main target within the aquifer was the sand‐clay interface defining the top of the underlying aquitard at 10 to 14 m depth. Although the water table in a well near the site was 8 m deep, cone penetration geotechnical data taken across the field do not reveal a distinct water table. Instead, cone penetration tests show a gradual change in electrical properties that we interpret as a thick zone of partial saturation. Comparing the seismic and radar data and using the geotechnical data as ground truth, we have associated the deepest coherent event in...

Journal ArticleDOI
TL;DR: In this article, a finite element code has been developed for the prediction of the radiated acoustic field from the aft fan duct of a turbofan engine, which is modelled based on the assumption that the steady flow in and around the nacelle is irrotational.