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Showing papers by "Missouri University of Science and Technology published in 2002"


Journal ArticleDOI
TL;DR: This paper seeks to reconcile and integrate two independent research efforts into a significantly evolved functional basis, and provides a mechanism for evaluating whether future revisions are needed to the functional basis and, if so, how to proceed.
Abstract: In engineering design, all products and artifacts have some intended reason behind their existence: the product or artifact function. Functional modeling provides an abstract, yet direct, method for understanding and representing an overall product or artifact function. Functional modeling also strategically guides design activities such as problem decomposition, physical modeling, product architecting, concept generation, and team organization. A formal function representation is needed to support functional modeling, and a standardized set of function-related terminology leads to repeatable and meaningful results from such a representation. We refer to this representation as a functional basis; in this paper, we seek to reconcile and integrate two independent research efforts into a significantly evolved functional basis. These efforts include research from the National Institute of Standards and Technology and two US universities, and their industrial partners. The overall approach for integrating the functional representations and the final results are presented. This approach also provides a mechanism for evaluating whether future revisions are needed to the functional basis and, if so, how to proceed. The integration process is discussed relative to differences, similarities, insights into the representations, and product validation. Based on the results, a more versatile and comprehensive design vocabulary emerges. This vocabulary will greatly enhance and expand the frontiers of research in design repositories, product architecture, design synthesis, and general product modeling.

1,104 citations


Journal ArticleDOI
TL;DR: In this paper, the authors evaluated conventional drinking water treatment processes under typical water treatment plant conditions to determine their effectiveness in the removal of seven common antibiotics: carbadox, sulfachlorpyridazine, sulfadimethoxine, sulfamerazine, sul-famethazine and trimethoprim.
Abstract: Conventional drinking water treatment processes were evaluated under typical water treatment plant conditions to determine their effectiveness in the removal of seven common antibiotics: carbadox, sulfachlorpyridazine, sulfadimethoxine, sulfamerazine, sul- famethazine, sulfathiazole, and trimethoprim. Experiments were conducted using synthetic solutions prepared by spiking both distilled/ deionized water and Missouri River water with the studied compounds. Sorption on Calgon WPH powdered activated carbon, reverse osmosis, and oxidation with chlorine and ozone under typical plant conditions were all shown to be effective in removing the studied antibiotics. Conversely, coagulation/flocculation/sedimentation with alum and iron salts, excess lime/soda ash softening, ultraviolet irra- diation at disinfection dosages, and ion exchange were all relatively ineffective methods of antibiotic removal. This study shows that the studied antibiotics could be effectively removed using processes already in use in many water treatment plants. Additional work is needed on by-product formation and the removal of other classes of antibiotics.

602 citations


Journal ArticleDOI
TL;DR: In this article, the authors give an introduction to the time scales calculus, and present various properties of the exponential function on an arbitrary time scale, and use it to solve linear dynamic equations of first order.

575 citations


Journal ArticleDOI
TL;DR: In this paper, the results of Raman scattering studies of nanocrystalline CeO 2 thin films are presented using the spatial correlation model from which the correlation length has been determined as a function of grain size.

483 citations


Journal ArticleDOI
TL;DR: Knowledge maps are node-link representations in which ideas are located in nodes and connected to other related ideas through a series of labeled links as mentioned in this paper, and they have been shown to enhance the benefits associated with scripted cooperation.
Abstract: Knowledge maps are node-link representations in which ideas are located in nodes and connected to other related ideas through a series of labeled links. The research on knowledge mapping in the last 12 years has produced a number of consistent findings. Students recall more central ideas when they learn from a knowledge map than when they learn from text and those with low verbal ability or low prior knowledge often benefit the most. The use of knowledge maps also appears to amplify the benefits associated with scripted cooperation. Learning from maps is enhanced by active processing strategies such as summarization or annotation and by designing maps according to gestalt principles of organization. Fruitful areas for future research on knowledge mapping include examining whether knowledge maps reduce cognitive load, how map learning is influenced by the structure of the information to be learned, and the possibilities for transfer. Implications for practice are briefly delineated.

433 citations


Journal ArticleDOI
TL;DR: A sequence of procedures involving finite mixture modeling and bootstrap inference is developed to address issues in studies involving many thousands of genes, including calorically restricted mice.

383 citations


Journal ArticleDOI
TL;DR: In this article, two fine-grained 7075Al alloys with a grain size of 3.8 and 7.5 μm were subjected to friction stir processing (FSP) with different processing parameters.

380 citations


Book ChapterDOI
12 Dec 2002
TL;DR: In this paper, the status of theory and research on perceptions of organizational politics has been assessed and a comprehensive review of the literature designed to convey the current state of the field with respect to theory development, testing, and validation, as well as methodological considerations, including levels of analysis issues.
Abstract: Organizational politics has intrigued academicians and practitioners for decades. Yet, serious scholarship on politics in organizations has emerged as a viable body of scientific inquiry just within the past twenty years. In general, theory and research on organizational politics has been sorted into the two categories of political behavior and its effects, and the nature of organizational politics perceptions. With few exceptions, these areas of inquiry have been treated as largely independent of one another. Whereas it is useful periodically to take stock of the current status of our knowledge base in particular areas of inquiry, we are often remiss in not engaging in such activity frequently enough. The present paper seeks to address this void by determining the status of theory and research on perceptions of organizational politics. First, we report on a comprehensive review of the literature designed to convey the current state of the field with respect to theory development, testing, and validation, as well as methodological considerations, including levels of analysis issues. Then, we propose future challenges with respect to construct expansion and validation, theory refinement, multi-level considerations, and integration with other constructs in the organizational sciences. Other issues that need to be addressed in future work are also examined in an effort to propose a revised model of politics perceptions to guide future research.

309 citations


Journal ArticleDOI
TL;DR: In this article, the authors review some of the key advances developed over the past 60 years in improving our understanding of the nature and methods of modifying and stabilizing expansive clay soils.
Abstract: Expansive clay soils—those that change significantly in volume with changes in water content—are the cause of distortions to structures that cost taxpayers several billion dollars annually in the United States. Much has been learned about their behavior over the past 60 years, and relatively successful methods have been developed to modify and stabilize them. This paper reviews some of the key advances developed over the past 60 years in improving our understanding of the nature and methods of modifying and stabilizing expansive clay soils. The state of the practice in stabilization is presented, and practical and research needs to help improve the state of the practice are discussed.

308 citations


Book
01 Jan 2002
TL;DR: 1. INTRODUCTION to BIOPRODUCTs and BIOSEPARATIONS 2. ANALYTICAL METHODs 3. CELL LYSIS and FLOCCULATION 4. FILTRATION 5. SEDIMENTATION 6. EXTRACTION 7. LIQUID CHROMATOGRAPHY and ADSORPTION 8. PRECIPITATION 9. CRYSTALLIZATION 10. DRYING 11. BIOPrOCESS
Abstract: 1. INTRODUCTION TO BIOPRODUCTS AND BIOSEPARATIONS 2. ANALYTICAL METHODS 3. CELL LYSIS AND FLOCCULATION 4. FILTRATION 5. SEDIMENTATION 6. EXTRACTION 7. LIQUID CHROMATOGRAPHY AND ADSORPTION 8. PRECIPITATION 9. CRYSTALLIZATION 10. DRYING 11. BIOPROCESS DESIGN 12. LABORATORY EXERCISES IN BIOSEPARATIONS APPENDIX A. TABLE OF UNITS AND CONSTANTS INDEX

259 citations


Journal ArticleDOI
TL;DR: In this paper, the structural behavior of reinforced concrete elements strengthened with near-surface mounted (NSM) fiber-reinforced polymer (FRP) rods is fully characterized, and bond is the first issue addressed.
Abstract: Use of near-surface mounted (NSM) fiber-reinforced polymer (FRP) rods is a promising technology for increasing flexural and shear strength of reinforced concrete (RC) members. As this technology emerges, the structural behavior of RC elements strengthened with NSM FRP rods should be fully characterized, and bond is the first issue to be addressed. Bond is of primary importance as it is the means for the transfer of stress between the concrete and the FRP reinforcement to develop composite action. This research program aimed to investigate bond between NSM FRP rods and concrete. Some of the factors expected to affect bond performance are addressed here, namely: bonded length, diameter and surface configuration of the rod, type of FRP material, and size of the groove in which the rod is embedded. Results are presented and discussed.

Journal ArticleDOI
TL;DR: In this article, a study of nanocrystalline oxide thin film processing and influence of microstructure on the electrical properties of Gd3+-doped CeO2 thin films was reported.

Journal ArticleDOI
TL;DR: In this paper, an optimal neurocontroller that replaces the conventional automatic voltage regulator (AVR) and the turbine governor for a turbogenerator connected to the power grid is presented.
Abstract: This paper presents the design of an optimal neurocontroller that replaces the conventional automatic voltage regulator (AVR) and the turbine governor for a turbogenerator connected to the power grid. The neurocontroller design uses a novel technique based on the adaptive critic designs (ACDs), specifically on heuristic dynamic programming (HDP) and dual heuristic programming (DHP). Results show that both neurocontrollers are robust, but that DHP outperforms HDP or conventional controllers, especially when the system conditions and configuration change. This paper also shows how to design optimal neurocontrollers for nonlinear systems, such as turbogenerators, without having to do continually online training of the neural networks, thus avoiding risks of instability.

Journal ArticleDOI
TL;DR: With motor execution being relatively automatic, adults were able to attend fully to the high-level processes required in mature, effective composition, and one reason that children fail to engage in such high- level processes is that motor processes deplete available attention.
Abstract: Writing a text requires the coordination of multiple high-level composition processes in working memory, including planning, language generation, and reviewing, in addition to low-level motor transcription. Here, interference in reaction time (RT) for detecting auditory probes was used to measure the attentional demands of (1) copying in longhand a prepared text (transcription), (2) composing a text and pausing handwriting for longer than 250 msec (composition), and (3) composing and currently handwriting (transcription + composition). Greater interference in the transcription + composition condition than in the transcription condition implies that high-level processes are activated concurrently with motor execution, resulting in higher attentional demands. This difference was observed for adults who wrote in standard cursive, but not for children and not for adults who used an unpracticed uppercase script. Greater interference in the composition condition than in the transcription condition implies that high-level processes demand more attention than do motor processes. This difference was observed only when adults wrote with a practiced script. With motor execution being relatively automatic, adults were able to attend fully to the high-level processes required in mature, effective composition. One reason that children fail to engage in such high-level processes is that motor processes deplete available attention.

Journal ArticleDOI
TL;DR: Cerium-based conversion coatings were formed by a spontaneous reaction between a water-based solution containing CeCl3 and aluminum alloy 7075-T6 substrates in this article.
Abstract: Cerium-based conversion coatings were formed by a spontaneous reaction between a water-based solution containing CeCl3 and aluminum alloy 7075-T6 substrates. Coating performance was evaluated in neutral salt fog according to ASTM B117. Coating microstructure and thickness were observed by scanning electron microscopy (SEM). Coating composition and the cerium oxidation state were characterized using energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) respectively. The morphology and salt fog performance of cerium conversion coatings were affected by pre-treatment of the panel prior to coating. The best pre-treatment consisted of desmutting, degreasing, and acid activation. After immersion in the coating solution for 30 s, Ce-rich deposits formed on the 7075 surface. After 5 min, coatings consisted of Ce-rich particles in a Ce-containing matrix. Immersion times of 5 min or longer produced coatings that could pass published military requirements for conversion coating performance in neutral salt fog. XPS analysis showed that the coatings contained Ce4+.

Journal ArticleDOI
TL;DR: In this paper, a minimum discrepancy approach is proposed to estimate the dimension of the partial central subspace of a SIR regression with both continuous and categorical predictors without the need of homogeneous predictor covariances across the subpopulations.
Abstract: Though partial sliced inverse regression (partial SIR: Chiaromonte et al. [2002. Sufficient dimension reduction in regressions with categorical predictors. Ann. Statist. 30, 475–497]) extended the scope of sufficient dimension reduction to regressions with both continuous and categorical predictors, its requirement of homogeneous predictor covariances across the subpopulations restricts its application in practice. When this condition fails, partial SIR may provide misleading results. In this article, we propose a new estimation method via a minimum discrepancy approach without this restriction. Our method is optimal in terms of asymptotic efficiency and its test statistic for testing the dimension of the partial central subspace always has an asymptotic chi-squared distribution. It also gives us the ability to test predictor effects. An asymptotic chi-squared test of the conditional independence hypothesis that the response is independent of a selected subset of the continuous predictors given the remaining predictors is obtained.

Journal ArticleDOI
TL;DR: In this article, a survey focused on project team leader behaviors, use of team building, and team member characteristics as predictors of project cost and schedule performance was conducted with 151 project teams in the engineering and construction industry.
Abstract: Interviews of project team members about factors that lead to high levels of team performance were used to create a survey that was given to 151 project teams in the engineering and construction industry. The survey focused on project team leader behaviors, use of team building, and team member characteristics as predictors of project cost and schedule performance. Controlling for use of industry best practices, leader behaviors were found to be significant predictors of project cost performance, while neither team building nor team member characteristics were found to be significant predictors of performance.

Journal ArticleDOI
TL;DR: In this paper, the high-energy asymptotics for Weyl-Titchmarsh matrices associated with general Dirac-type operators on half-lines and on R were explicitly determined.
Abstract: We explicitly determine the high-energy asymptotics for Weyl-Titchmarsh matrices associated with general Dirac-type operators on half-lines and on R. We also prove new local uniqueness results for Dirac-type operators in terms of exponentially small differences of Weyl-Titchmarsh matrices. As concrete applications of the asymptotic high-energy expansion we derive a trace formula for Dirac operators and use it to prove a Borg-type theorem.


Journal ArticleDOI
TL;DR: In this paper, quantitative metrics are developed that allow designers to identify products that are similar in a manner critical to the success of a design, based on the functional similarity of products.
Abstract: During the design and development of new products, design engineers use many tech- niques to generate and define new and ''good'' concepts. Inherent in this search for solutions is the conscious and unconscious reliance on prior experience and knowledge, or design-by-analogy. In this paper, a quantitative metric for design-by-analogy is devel- oped. This metric is based on the functional similarity of products. By using this product- similarity metric, designers are able to formalize and quantify design-by-analogy tech- niques during concept and layout design. The methods, as developed in this paper, allow a designer with limited experience to develop sophisticated solutions that enhance the overall design of a new product. Also, a designer's current design-by-analogy vocabulary can be extended beyond his or her immediate experience, providing access and contribu- tions to new domains by discovering different products with common functions. The simi- larity metric and its application are clarified and validated through a case study. The case study is the original design of a pickup winder. @DOI: 10.1115/1.1475317# During the design and development of new products, design engineers use many techniques to generate and define new and ''good'' concepts. Inherent in this search for solutions is the con- scious and unconscious reliance on prior experience and knowl- edge. Numerous attempts have been made to organize, qualify, and make accessible the critical design experience and knowledge needed to solve particular problems. Some of these techniques take the form of knowledge-based design, expert design systems, and design rules or design guidelines. In this paper, quantitative metrics are developed that allow designers to identify products that are similar in a manner critical to the success of a design. This focused identification allows these similar products to be reviewed within the context of the design problem at hand for configuration, concept, and embodiment information. These metrics allow for- malized design-by-analogy efforts by identifying products that have design-critical similarity. The paper is organized in the following way. First, the notion of similarity as used here is clarified. Toward the goal of finding the important product similarities, groundwork is developed to make comparisons between products. In the remainder of this paper, these notions of product similarity in the search for analogies are explored. Also, a procedure for applying these techniques to a design problem is presented. Lastly, an example application of the design-by-analogy techniques is applied to an original design case study. The paper concludes with a brief discussion of the contri- butions of the work presented here. 2 Relevant Analogies The notions of similarity and analogies based on similarity are broad. From Moody charts to the Periodic Table, organizing schemes based on similarities and differences are critical tools in engineering and science. In fluid mechanics, the comparison of different objects based on similarities in the Reynolds number, the Biot number, or other meaningful metrics for comparison, is not only common place but critical to the fundamental understanding of the relevant physics that affect the systems. Before developing a design tool based on analogy, the basis for making the compari- son is necessary. For example, based on a color comparison, a car and a watch may be similar. In fact, they also may share the similarity of manufacturing country of origin. Reviewing a watch as an exercise to find alternative ways to mix fuel and air in the car is likely a fruitless exercise. Before searching for design in- formation in existing and similar designs, the notion of similarity needs to be understood in the context of design.

Book
23 Dec 2002
TL;DR: The solution of Linear Systems Gaussian Elimination LU Factorization Condition Numbers and Error Propagation Relaxation Methods and The Power Method and QR Algorithm are presented.
Abstract: Introduction The Solution of Linear Systems Gaussian Elimination LU Factorization Condition Numbers and Error Propagation Relaxation Methods Conjugate Gradient Methods Generalized Minimal Residual Algorithm (GMRES) Systems of Nonlinear Equations Fixed Point Iteration Newton-Raphson Iteration Continuation Methods Secant Method Numerical Differentiation Power System Applications Sparse Matrix Solution Techniques Storage Methods Sparse Matrix Representation Ordering Schemes Power System Applications Numerical Integration One-Step Methods Multistep Methods Accuracy and Error Analysis Numerical Stability Analysis Stiff Systems Step-Size Selection Differential-Algebraic Equations Power System Applications Optimization Least Squares State Estimation Linear Programming Nonlinear Programming Power System Applications Eigenvalue Problems The Power Method The QR Algorithm Arnoldi Methods Singular Value Decomposition Modal Identification Power System Applications

Journal ArticleDOI
TL;DR: In this article, the effects of step height on the flow and heat transfer characteristics are investigated for incompressible laminar forced convection flow adjacent to backward facing step in rectangular ducts.

Journal ArticleDOI
TL;DR: The chemistry and biochemistry of AGE-related crosslinks such as pyrraline, pentosidine, carboxymethyllysine (CML), crosslines, imidazolidinones, and dilysine crosslinks (GOLD and MOLD), as well as their possible involvement in neurodegenerative conditions are discussed.
Abstract: Maillard reactions have been explored by food chemists for many years. It is only recently that the advanced glycation end products (AGEs), the end products of the Maillard reaction, have been detected in a wide variety of diseases such as diabetes, atherosclerosis, cataractogenesis, Parkinson disease and Alzheimer disease (AD). In this review, we discuss the chemistry and biochemistry of AGE-related crosslinks such as pyrraline, pentosidine, carboxymethyllysine (CML), crosslines, imidazolidinones, and dilysine crosslinks (GOLD and MOLD), as well as their possible involvement in neurodegenerative conditions. Pentosidine and CML are found in elevated amounts in the major lesions of the AD brain. Glycation is also implicated in the formation of the paired helical filaments (PHF), a component of the neurofibrillary tangles (NFTs). Amyloid-β peptide and proteins of the cerebrospinal fluid are also glycated in patients with AD. In order to ameliorate the effects of AGEs on AD pathology, various inhibitors of AGEs have been increasingly explored. It is hoped that understanding of the mechanism of the AGEs formation and their role in the neurodegeneration will result in vovel therapeutics for neuroprotection.

Journal ArticleDOI
TL;DR: Half-metallic ferrimagnetic materials such as Fe(3)O(4) are of interest for use in spintronic devices that exploit both the spin and charge of an electron in spin-dependent charge transport.
Abstract: Half-metallic ferrimagnetic materials such as Fe3O4 are of interest for use in spintronic devices. These devices exploit both the spin and charge of an electron in spin-dependent charge transport. Epitaxial thin films of Fe3O4 have been grown on the three low-index planes of gold by electrodeposition. On Au(110), a [110] Fe3O4 orientation that is aligned with the underlying Au(110) substrate is observed. Thin films on Au(100) grow with three different orientations: [100], [111], and [511]. On Au(111), both [111] and [511] orientations of Fe3O4 are observed. The [511] orientations are the result of twinning on {111} planes. A polarization value of approximately −40% at the Fermi level was measured by spin-polarized photoemission at room temperature for a thin film on Au(111).

Journal ArticleDOI
TL;DR: In this article, the authors compared the deformation of a high silica (93% silica and 3% zircon) and a low silica/zircon (3 vs. 24%) with a power-law deformation model and found that the high-silica deformation was dominated by reinitiated sintering and subsequent cristobalite formation.
Abstract: Dimensional changes and creep deformation of a silica/zircon (74%/24%, respectively) and a high silica (93% silica and 3% zircon) ceramic were characterized and compared. All specimens were tested with a thermal profile that consisted of a 300°C/h heating rate to 1475 or 1525°C, followed by a one-hour isothermal hold (where each specimen was compressively crept under a static stress of 2.07, 4.14, or 6.21 MPa). The specimens were cooled at a rate of 900°C/h under stress. Dimensional changes were interpreted from apparent thermal expansion behavior during heating as well as before-and-after dimensional measurements. The silica/zircon ceramic generally exhibited less total contraction than the high silica ceramic for a specific test condition even though it crept faster at all stresses and temperatures during the one-hour isothermal/isostress segment. This indicates that the total contraction for both was dominated by reinitiated sintering and subsequent cristobalite formation that occurred during the heating segment. Minimum creep rate during the one-hour isothermal/isostress segment was examined as a function of stress and temperature for both ceramics using a power-law creep model. Creep-rate stress exponents (n) and activation energies (Q) were equivalent (within 95% confidence) for both ceramics showing that their different contents of zircon (3 vs. 24%) did not affect them. Lastly, n ≈ 1.3–1.4 and Q ≈ 170 kJ/mol indicate that diffusion-assisted crystallization of cristobalite, combined with power-law sintering owing to the high concentration of porosity (28–30%) was likely the rate-limiting mechanism in the creep deformation for both ceramics.

Journal ArticleDOI
TL;DR: The local environment around iron ions in iron phosphate glasses of starting batch composition 40Fe 2 O 3 -60P 2 O 5 (mol%) melted at varying temperatures or under different melting atmospheres has been investigated using Fe-57 Mossbauer and X-ray absorption fine structure (XAFS) spectroscopies.
Abstract: The local environment around iron ions in iron phosphate glasses of starting batch composition 40Fe 2 O 3 –60P 2 O 5 (mol%) melted at varying temperatures or under different melting atmospheres has been investigated using Fe-57 Mossbauer and X-ray absorption fine structure (XAFS) spectroscopies. Mossbauer spectra indicate that all of the glasses contain both Fe(II) and Fe(III) ions. The quadrupole splitting distribution fits of Mossbauer spectra show that Fe(II) ions occupy a single site whereas Fe(III) ions occupy two distinct sites in these glasses. When melted at higher temperatures or in reducing atmospheres, the Fe(II) fraction in the glass increases at the expense of Fe(III) ions at only one of the two sites they occupy. The pre-edge feature in the XAFS data suggests that the overall disorder in the near-neighbor environment of iron ions decreases with increasing Fe(II) fraction. The XAFS results also show that the average iron–oxygen coordination is in the 4–5 range indicating that iron ions have mixed tetrahedral–octahedral coordination.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the volume dependence of the magnetic moments of Mn and Bi and found that an increase in the intra-atomic exchange splitting due to the cell volume expansion leads to a large magnetic moment for the Mn atom.
Abstract: The low-temperature phase of the MnBi alloy has a coercivity μ0Hc of 2.0 T at 400 K and exhibits a positive temperature coefficient from 0 to 400 K. In the higher temperature range it shows a much higher coercivity than that of the NdFeB magnets, which suggests that it has considerable potential as a permanent magnet for use at high temperatures. In the temperature range from 30 to 150 K, the Mn atom is found to change its spin direction from a perpendicular to a parallel orientation with respect to the c axis. The anisotropy field increases with increasing temperature which gives rise to a higher coercivity at the higher temperatures. The maximum energy product (BH)max of the magnet is 7.7 and 4.6 MG Oe at room temperature and 400 K, respectively. The electronic structure of MnBi indicates that the Mn atom possesses a magnetic moment of 3.6μB, and that the Bi atom has a magnetic moment of −0.15μB which is due to the s–d and p–d hybridization between Bi and Mn atoms. We have also investigated the volume dependence of the magnetic moments of Mn and Bi. The results indicate that an increase in the intra-atomic exchange splitting due to the cell volume expansion leads to a large magnetic moment for the Mn atom. The Mn magnetic moment attains a value of 4.6μB at a volume expansion rate of ΔV/V ≈ 100%.

Journal ArticleDOI
TL;DR: In this article, the structure of the 43.3PbO·13.7Fe 2 O 3 ·43P 2 O 5 (mol%) glass, which has a dissolution rate in aqueous solution at 90 °C of 1.26×10 −9 g/cm −2 ǫmin −1, and the same O/P ratio, 3.5, as the lead-free 40Fe 2O 3 ·60P 2O 5 glass, was investigated.
Abstract: Lead iron–phosphate glasses were investigated for use as wasteform because of their improved chemical durability. There is a controversy if lead should or should not be used in iron phosphate glasses, and on the role of Fe in the inhibition of corrosion. The structure of the 43.3PbO·13.7Fe 2 O 3 ·43P 2 O 5 (mol%) glass, which has a dissolution rate in aqueous solution at 90 °C of 1.26×10 −9 g/cm −2 min −1 , and the same O/P ratio, 3.5, as the lead-free 40Fe 2 O 3 ·60P 2 O 5 glass, was investigated. Glass samples were produced by melting batches of Fe 2 O 3 , PbO, and NH 4 H 2 PO 4 at 1100 °C for 1 h, and pouring the liquid into steel mold. Samples were annealed at 450 °C for 3 h. Some samples were crystallized by heating at 700 °C for 24 h. X-ray diffraction, Mossbauer, EPR, infrared, and Raman scattering spectroscopy were performed and compared to spectra obtained after crystallization. The crystalline phase Fe 2 Pb(P 2 O 7 ) 2 was identified after crystallization. The hyperfine parameters from the Mossbauer spectrum indicates that Fe 2+ and Fe 3+ ions are in octahedral coordination, and some of the Fe 3+ ions in the starting batch are reduced to Fe 2+ ions after melting. The infrared and Raman scattering spectra are representative of a mixture of chain-terminating Q 1 species and chain-forming Q 2 species. No Raman bands related to PO vibrations and Q 0 species were observed. From the EPR measurements it is concluded that all Fe 3+ ions are not constrained to central positions of tetrahedral and octahedral sites of the glass formers.

Journal ArticleDOI
TL;DR: Tissue analysis and determination of partitioning coefficients may provide an effective way to estimate the concentration of compounds in the transpiration stream and in the soil or groundwater in a noninvasive, extremely rapid, and cost-effective manner.
Abstract: Analysis of tree cores collected from contaminated sites has shown that concentrations of VOCs in cores are related to groundwater concentrations. However, initial research was highly qualitative. To better understand the relationship of groundwater VOC concentrations to measured VOCs in tree cores, detailed understanding of contaminant behavior in vegetation is required. Work presented here investigates the interaction, with focus on the chlorinated solvents trichloroethylene, 1,1,2,2-tetrachloroethane, and carbon tetrachloride. The sorption and desorption partitioning of these compounds between air and woody biomass were investigated. Partitioning coefficients were determined for cores of trunks of large trees and smaller stem cuttings. The internal partitioning of these compounds between the transpiration stream and the woody biomass within the tree was also determined for cores. The partitioning coefficients of the compounds between air, water, and biomass of tree cores and trunks were related to the physicochemical characteristics of contaminants, mainly the Henry's law constant and vapor pressure. These partitioning coefficients relate the contaminants' concentration in the bulk solution and analyzed headspace of vials and therefore can be utilized to quantify the fate of contaminants in natural settings and in phytoremediation systems. Tissue analysis and determination of partitioning coefficients may provide an effective way to estimate the concentration of compounds in the transpiration stream and in the soil or groundwater in a noninvasive, extremely rapid, and cost-effective manner.

Journal ArticleDOI
10 Dec 2002
TL;DR: In this article, a novel optimal neurocontroller that replaces the conventional controller (CONVC), which consists of the automatic voltage regulator and turbine governor, to control a synchronous generator in a power system using a multilayer perceptron neural network and a radial basis function neural network (RBFN).
Abstract: This paper presents a novel optimal neurocontroller that replaces the conventional controller (CONVC),which consists of the automatic voltage regulator (AVR) and turbine governor, to control a synchronous generator in a power system using a multilayer perceptron neural network (MLPN) and a radial basis function neural network (RBFN). The heuristic dynamic programming (HDP) based on the adaptive critic design (ACD) technique is used for the design of the neurocontroller. The performance of the MLPN based HDP neurocontroller (MHDPC) is compared with the RBFN based HDP neurocontroller (RHDPC) for small as well as large disturbances to a power system, and they are in turn compared with the CONVC. Simulation results are presented to show that the proposed neurocontrollers provide stable convergence with robustness, and the RHDPC outperforms the MHDPC and CONVC in terms of system damping and transient improvement.