Showing papers by "National University of Singapore published in 2002"
TL;DR: This work has shown how the emission wavelength of quantum-dot nanocrystals can be continuously tuned by changing the particle size, and a single light source can be used for simultaneous excitation of all different-sized dots.
2,066 citations
TL;DR: Oligonucleotide microarrays used to analyze the pattern of genes expressed in leukemic blasts from 360 pediatric ALL patients identified each of the prognostically important leukemia subtypes, and within some genetic subgroups, expression profiles identified those patients that would eventually fail therapy.
1,937 citations
TL;DR: In this article, the authors propose a framework for the analysis of economic integration and its relation to the asymmetries of economic and social development, which is more adequate to the exigencies and consequences of globalization than has traditionally been the case in development studies.
Abstract: This article outlines a framework for the analysis of economic integration and its relation to the asymmetries of economic and social development. Consciously breaking with state-centric forms of social science, it argues for a research agenda that is more adequate to the exigencies and consequences of globalization than has traditionally been the case in 'development studies'. Drawing on earlier attempts to analyse the cross-border activities of firms, their spatial configurations and developmental consequences, the article moves beyond these by proposing the framework of the 'global production network' (GPN). It explores the conceptual elements involved in this framework in some detail and then turns to sketch a stylized example of a GPN. The article concludes with a brief indication of the benefits that could be delivered by research informed by GPN analysis.
1,809 citations
Book•
29 Jul 2002TL;DR: In this paper, Galerkin et al. defined mesh-free methods for shape function construction, including the use of mesh-less local Petrov-Galerkin methods.
Abstract: Preliminaries Physical Problems in Engineering Solid Mechanics: A Fundamental Engineering Problem Numerical Techniques: Practical Solution Tools Defining Meshfree Methods Need for Meshfree Methods The Ideas of Meshfree Methods Basic Techniques for Meshfree Methods Outline of the Book Some Notations and Default Conventions Remarks Meshfree Shape Function Construction Basic Issues for Shape Function Construction Smoothed Particle Hydrodynamics Approach Reproducing Kernel Particle Method Moving Least Squares Approximation Point Interpolation Method Radial PIM Radial PIM with Polynomial Reproduction Weighted Least Square (WLS) Approximation Polynomial PIM with Rotational Coordinate Transformation Comparison Study via Examples Compatibility Issues: An Analysis Other Methods Function Spaces for Meshfree Methods Function Spaces Useful Spaces in Weak Formulation G Spaces: Definition G1h Spaces: Basic Properties Error Estimation Concluding Remarks Strain Field Construction Why Construct Strain Field? Historical Notes How to Construct? Admissible Conditions for Constructed Strain Fields Strain Construction Techniques Concluding Remarks Weak and Weakened Weak Formulations Introduction to Strong and Weak Forms Weighted Residual Method A Weak Formulation: Galerkin A Weakened Weak Formulation: GS-Galerkin The Hu-Washizu Principle The Hellinger-Reissner Principle The Modified Hellinger-Reissner Principle Single-Field Hellinger-Reissner Principle The Principle of Minimum Complementary Energy The Principle of Minimum Potential Energy Hamilton's Principle Hamilton's Principle with Constraints Galerkin Weak Form Galerkin Weak Form with Constraints A Weakened Weak Formulation: SC-Galerkin Parameterized Mixed Weak Form Concluding Remarks Element Free Galerkin Method EFG Formulation with Lagrange Multipliers EFG with Penalty Method Summary Meshless Local Petrov-Galerkin Method MLPG Formulation MLPG for Dynamic Problems Concluding Remarks Point Interpolation Methods Node-Based Smoothed Point Interpolation Method (NS-PIM) NS-PIM Using Radial Basis Functions (NS-RPIM) Upper Bound Properties of NS-PIM and NS-RPIM Edge-Based Smoothed Point Interpolation Methods (ES-PIMs) A Combined ES/NS Point Interpolation Methods (ES/NS-PIM) Strain-Constructed Point Interpolation Method (SC-PIM) A Comparison Study Summary Meshfree Methods for Fluid Dynamics Problem Introduction Navier-Stokes Equations Smoothed Particle Hydrodynamics Method Gradient Smoothing Method (GSM) Adaptive Gradient Smoothing Method (A-GSM) A Discussion on GSM for Incompressible Flows Other Improvements on GSM Meshfree Methods for Beams PIM Shape Function for Thin Beams Strong Form Equations Weak Formulation: Galerkin Formulation A Weakened Weak Formulation: GS-Galerkin Three Models Formulation for NS-PIM for Thin Beams Formulation for Dynamic Problems Numerical Examples for Static Analysis Numerical Examples: Upper Bound Solution Numerical Examples for Free Vibration Analysis Concluding Remarks Meshfree Methods for Plates Mechanics for Plates EFG Method for Thin Plates EFG Method for Thin Composite Laminates EFG Method for Thick Plates ES-PIM for Plates Meshfree Methods for Shells EFG Method for Spatial Thin Shells EFG Method for Thick Shells ES-PIM for Thick Shells Summary Boundary Meshfree Methods RPIM Using Polynomial Basis RPIM Using Radial Function Basis Remarks Meshfree Methods Coupled with Other Methods Coupled EFG/BEM Coupled EFG and Hybrid BEM Remarks Meshfree Methods for Adaptive Analysis Triangular Mesh and Integration Cells Node Numbering: A Simple Approach Bucket Algorithm for Node Searching Relay Model for Domains with Irregular Boundaries Techniques for Adaptive Analysis Concluding Remarks MFree2D(c) Overview Techniques Used in MFree2D Preprocessing in MFree2D Postprocessing in MFree2D Index References appear at the end of each chapter.
1,768 citations
TL;DR: Analysis of the measured data shows a high correlation between the scaffold porosity and the compressive properties based on a power-law relationship.
1,635 citations
TL;DR: It is suggested that more investigations are needed, as the metal–N–H system could prove to be a promising route to reversible hydrogen storage, as this compound can also reversibly take up large amounts of hydrogen.
Abstract: The pursuit of a clean and healthy environment has stimulated much effort in the development of technologies for the utilization of hydrogen-based energy. A critical issue is the need for practical systems for hydrogen storage, a problem that remains unresolved after several decades of exploration. In this context, the possibility of storing hydrogen in advanced carbon materials has generated considerable interest. But confirmation and a mechanistic understanding of the hydrogen-storage capabilities of these materials still require much work1,2,3,4,5. Our previously published work on hydrogen uptake by alkali-doped carbon nanotubes cannot be reproduced by others6,7,8. It was realized by us and also demonstrated by Pinkerton et al.8 that most of the weight gain was due to moisture, which the alkali oxide picked up from the atmosphere. Here we describe a different material system, lithium nitride, which shows potential as a hydrogen storage medium. Lithium nitride is usually employed as an electrode, or as a starting material for the synthesis of binary or ternary nitrides9,10. Using a variety of techniques, we demonstrate that this compound can also reversibly take up large amounts of hydrogen. Although the temperature required to release the hydrogen at usable pressures is too high for practical application of the present material, we suggest that more investigations are needed, as the metal–N–H system could prove to be a promising route to reversible hydrogen storage.
1,444 citations
TL;DR: In this article, a field survey of 467 employees of four large, public organizations showed that expected associations and contribution are the major determinants of the individual's attitude toward knowledge sharing.
Abstract: Many CEOs and managers understand the importance of knowledge sharing among their employees and are eager to introduce the knowledge management paradigm in their organizations. However little is known about the determinants of the individual's knowledge sharing behavior. The purpose of this study is to develop an understanding of the factors affecting the individual's knowledge sharing behavior in the organizational context. The research model includes various constructs based on social exchange theory, self-efficacy, and theory of reasoned action. Research results from the field survey of 467 employees of four large, public organizations show that expected associations and contribution are the major determinants of the individual's attitude toward knowledge sharing. Expected rewards, believed by many as the most important motivating factor for knowledge sharing, are not significantly related to the attitude toward knowledge sharing. As expected, positive attitude toward knowledge sharing is found to lead to positive intention to share knowledge and, finally, to actual knowledge sharing behaviors.
1,180 citations
TL;DR: In this article, a multivariate generalized autoregressive conditional heteroscedasticity (MGARCH) model with time-varying correlations is proposed, which adopts the vech representation based on the conditional variances and the conditional correlations.
Abstract: In this article we propose a new multivariate generalized autoregressive conditional heteroscedasticity (MGARCH) model with time-varying correlations. We adopt the vech representation based on the conditional variances and the conditional correlations. Whereas each conditional-variance term is assumed to follow a univariate GARCH formulation, the conditional-correlation matrix is postulated to follow an autoregressive moving average type of analog. Our new model retains the intuition and interpretation of the univariate GARCH model and yet satisfies the positive-definite condition as found in the constant-correlation and Baba–Engle–Kraft–Kroner models. We report some Monte Carlo results on the finite-sample distributions of the maximum likelihood estimate of the varying-correlation MGARCH model. The new model is applied to some real data sets.
1,087 citations
TL;DR: In this paper, the contribution of l-ascorbic acid (AA) to the total antioxidant activity of fruits was investigated by using RP-HPLC, which measured the change of absorbance of the free radical solution at 414 nm in the test reaction mixture following addition of the fruit extract, as compared with AA.
1,031 citations
TL;DR: This paper aims at a systematic study of discretization methods with their history of development, effect on classification, and trade-off between speed and accuracy.
Abstract: Discrete values have important roles in data mining and knowledge discovery They are about intervals of numbers which are more concise to represent and specify, easier to use and comprehend as they are closer to a knowledge-level representation than continuous values Many studies show induction tasks can benefit from discretization: rules with discrete values are normally shorter and more understandable and discretization can lead to improved predictive accuracy Furthermore, many induction algorithms found in the literature require discrete features All these prompt researchers and practitioners to discretize continuous features before or during a machine learning or data mining task There are numerous discretization methods available in the literature It is time for us to examine these seemingly different methods for discretization and find out how different they really are, what are the key components of a discretization process, how we can improve the current level of research for new development as well as the use of existing methods This paper aims at a systematic study of discretization methods with their history of development, effect on classification, and trade-off between speed and accuracy Contributions of this paper are an abstract description summarizing existing discretization methods, a hierarchical framework to categorize the existing methods and pave the way for further development, concise discussions of representative discretization methods, extensive experiments and their analysis, and some guidelines as to how to choose a discretization method under various circumstances We also identify some issues yet to solve and future research for discretization
981 citations
TL;DR: In this article, a point interpolation meshless method is proposed based on combining radial and polynomial basis functions, which makes the implementation of essential boundary conditions much easier than the meshless methods based on the moving least-squares approximation.
Abstract: A point interpolation meshless method is proposed based on combining radial and polynomial basis functions. Involvement of radial basis functions overcomes possible singularity associated with the meshless methods based on only the polynomial basis. This non-singularity is useful in constructing well-performed shape functions. Furthermore, the interpolation function obtained passes through all scattered points in an influence domain and thus shape functions are of delta function property. This makes the implementation of essential boundary conditions much easier than the meshless methods based on the moving least-squares approximation. In addition, the partial derivatives of shape functions are easily obtained, thus improving computational efficiency. Examples on curve/surface fittings and solid mechanics problems show that the accuracy and convergence rate of the present method is high. Copyright © 2002 John Wiley & Sons, Ltd.
TL;DR: In this article, Li(Ni 1/3 Co 1/1/3 Mn 1 /3 )O 2 was prepared by mixed hydroxide method and characterised by means of X-ray diffraction, Xray photoelectron spectroscopy (XPS), cyclic voltammetry and charge-discharge cycling.
TL;DR: It is shown that human fetal and adult fibroblast feeders support prolonged undifferentiated HES cell growth of existing cell lines and are superior to cell-free matrices supplemented with human or MEF feeder–conditioned medium.
Abstract: Previous reports have demonstrated the growth of undifferentiated human embryonic stem (HES) cells on mouse embryonic fibroblast (MEF) feeders and on laminin- or Matrigel-coated plastic surfaces supplemented with MEF-conditioned medium. These xenosupport systems run the risk of cross-transfer of animal pathogens from the animal feeder, matrix, or conditioned medium to the HES cells, thus compromising later clinical application. Here we show that human fetal and adult fibroblast feeders support prolonged undifferentiated HES cell growth of existing cell lines and are superior to cell-free matrices (collagen I, human extracellular matrix, Matrigel, and laminin) supplemented with human or MEF feeder-conditioned medium. Additionally, we report the derivation and establishment of a new HES cell line in completely animal-free conditions. Like HES cells cultured on MEF feeders, the HES cells grown on human feeders had normal karyotypes, tested positive for alkaline phosphatase activity, expressed Oct-4 and cell surface markers including SSEA-3, SSEA-4, Tra 1-60, and GCTM-2, formed teratomas in severely combined immunodeficient (SCID) mice, and retained all key morphological characteristics. Human feeder#150;supported HES cells should provide a safer alternative to existing HES cell lines in therapeutic applications.
TL;DR: A new potential field method for motion planning of mobile robots in a dynamic environment where the target and the obstacles are moving is proposed and the problem of local minima is discussed.
Abstract: The potential field method is widely used for autonomous mobile robot path planning due to its elegant mathematical analysis and simplicity. However, most researches have been focused on solving the motion planning problem in a stationary environment where both targets and obstacles are stationary. This paper proposes a new potential field method for motion planning of mobile robots in a dynamic environment where the target and the obstacles are moving. Firstly, the new potential function and the corresponding virtual force are defined. Then, the problem of local minima is discussed. Finally, extensive computer simulations and hardware experiments are carried out to demonstrate the effectiveness of the dynamic motion planning schemes based on the new potential field method.
TL;DR: Retinal arteriolar narrowing is related to risk of CHD in women but not in men, supporting a more prominent microvascular role in the development of CHd in women than in men.
Abstract: ContextMicrovascular processes have been hypothesized to play a greater role
in the development of coronary heart disease (CHD) in women than in men; however,
prospective clinical data are limited.ObjectiveTo examine the association between retinal arteriolar narrowing, a marker
of microvascular damage from hypertension and inflammation, and incident CHD
in healthy middle-aged women and men.Design, Setting, and ParticipantsThe Atherosclerosis Risk in Communities Study, an ongoing prospective,
population-based cohort study in 4 US communities initiated in 1987-1989.
Retinal photographs were taken in 9648 women and men aged 51 to 72 years without
CHD at the third examination (1993-1995). To quantify retinal arteriolar narrowing,
the photographs were digitized, individual arteriolar and venular diameters
were measured, and a summary arteriole-to-venule ratio (AVR) was calculated.Main Outcome MeasureRisk of CHD associated with retinal arteriolar narrowing.ResultsDuring an average 3.5 years of follow-up, 84 women and 187 men experienced
incident CHD events. In women, after controlling for mean arterial blood pressure
averaged over the previous 6 years, diabetes, cigarette smoking, plasma lipid
levels, and other risk factors, each SD decrease in the AVR was associated
with an increased risk of any incident CHD (relative risk [RR], 1.37; 95%
confidence interval [CI], 1.08-1.72) and of acute myocardial infarction (RR,
1.50; 95% CI, 1.10-2.04). In contrast, AVR was unrelated to any incident CHD
in men (RR, 1.00; 95% CI, 0.84-1.18) or to acute myocardial infarction (RR,
1.08; 95% CI, 0.85-1.38).ConclusionRetinal arteriolar narrowing is related to risk of CHD in women but
not in men, supporting a more prominent microvascular role in the development
of CHD in women than in men. Future work is needed to confirm these findings.
TL;DR: In this paper, the authors examined the role of neutralization techniques in facilitating cyber-loafing at the workplace and found that when individuals perceived their organizations to be distributively, procedurally and interactionally unjust, they were likely to invoke the metaphor of the ledger as a neutralization technique.
Abstract: Summary Much attention has been devoted to how technological advancements have created a brave new workplace, revolutionzing the ways in which work is being carried out, and how employees can improve their productivity and efficiency However, the advent of technology has also opened up new avenues and opportunities for individuals to misbehave This study focused on cyberloafing—the act of employees using their companies’ internet access for personal purposes during work hours Cyberloafing, thus, represents a form of production deviance Using the theoretical frameworks offered by social exchange, organizational justice and neutralization, we examined the often-neglected dark side of the internet and the role that neutralization techniques play in facilitating this misbehavior at the workplace Specifically, we developed a model which suggested that when individuals perceived their organizations to be distributively, procedurally and interactionally unjust, they were likely to invoke the metaphor of the ledger as a neutralization technique to legitimize their subsequent engagement in the act of cyberloafing Data were collected with the use of an electronic questionnaire and focus group interviews from 188 working adults with access to the internet at the workplace Results of structural equation modelling provided empirical support for all of our hypotheses Implications of our findings for organizational internet policies are discussed Copyright # 2002 John Wiley & Sons, Ltd
TL;DR: A simple condition is derived in terms of an auxiliary feedback matrix for determining if a given ellipsoid is contractively invariant, which is shown to be less conservative than the existing conditions which are based on the circle criterion or the vertex analysis.
TL;DR: The equivalence of the matrices for processing, the objective functions, the optimal basis vectors, the mean-square errors, and the asymptotic connections of the three POD methods are demonstrated and proved when the methods are used to handle the POD of discrete random vectors.
TL;DR: In this paper, the authors examined the influences of a firm's intangible assets and its experience on foreign subsidiary survival and profitability using a sample of 3,080 subsidiaries of 641 Japanese firms.
Abstract: This study integrates research on the financial performance of multinational firms with research on foreign subsidiary survival. We examined the influences a firm's intangible assets and its experience have on foreign subsidiary survival and profitability using a sample of 3,080 subsidiaries of 641 Japanese firms. The results show survival and profitability have different antecedents. Host country experience has a direct effect on survival but a contingent relationship with profitability. The entry mode moderated the nature of these relationships.
TL;DR: In this article, the ability of bioadhesive polysaccharide chitosan nanoparticles to enhance intestinal absorption of insulin and increase the relative pharmacological bioavailability of insulin was investigated by monitoring the plasma glucose level of alloxan-induced diabetic rats after oral administration of various doses of insulin-loaded CS-NPs.
TL;DR: This article used a cognitive approach to examine opportunity evaluation, as the perception of opportunity is essentially a cognitive phenomenon, and found that illusion of control and belief in the law of small numbers are related to how entrepreneurs evaluate opportunities.
Abstract: Even though the entrepreneurship literature places much emphasis on opportunity recognition, little is known about how entrepreneurs actually evaluate opportunities. This study uses a cognitive approach to examine opportunity evaluation, as the perception of opportunity is essentially a cognitive phenomenon. We present a model that consists of four independent variables (overconfidence, belief in the law of small numbers, planning fallacy, and illusion of control), a mediating variable (risk perception), two control variables (demographics and risk propensity), and the dependent variable (opportunity evaluation). We find that illusion of control and belief in the law of small numbers are related to how entrepreneurs evaluate opportunities. Our results also indicate that risk perception mediates opportunity evaluation.
TL;DR: It is demonstrated that COI1 associates physically with AtCUL1, AtRbx1, and either of the Arabidopsis Skp1-like proteins ASK1 or ASK2 to assemble ubiquitin-ligase complexes, which are designated SCF(COI1), and that the axr1 and coi1 mutations display a synergistic genetic interaction in the double mutant.
Abstract: Xie and colleagues previously isolated the Arabidopsis COI1 gene that is required for response to jasmonates (JAs), which regulate root growth, pollen fertility, wound healing, and defense against insects and pathogens. In this study, we demonstrate that COI1 associates physically with AtCUL1, AtRbx1, and either of the Arabidopsis Skp1-like proteins ASK1 or ASK2 to assemble ubiquitin-ligase complexes, which we have designated SCF(COI1). COI1(E22A), a single amino acid substitution in the F-box motif of COI1, abolishes the formation of the SCF(COI1) complexes and results in loss of the JA response. AtRbx1 double-stranded RNA-mediated genetic interference reduces AtRbx1 expression and affects JA-inducible gene expression. Furthermore, we show that the AtCUL1 component of SCF(COI1) complexes is modified in planta, where mutations in AXR1 decrease the abundance of the modified AtCUL1 of SCF(COI1) and lead to a reduction in JA response. Finally, we demonstrate that the axr1 and coi1 mutations display a synergistic genetic interaction in the double mutant. These results suggest that the COI1-mediated JA response is dependent on the SCF(COI1) complexes in Arabidopsis and that the AXR1-dependent modification of the AtCUL1 subunit of SCF(COI1) complexes is important for JA signaling.
TL;DR: In this article, the authors investigate the impact of the founding-family ownership structure on the agency cost of debt and find that family ownership is common in large, publicly traded firms and is related, both statistically and economically, to lower costs of debt financing.
Abstract: We investigate the impact of founding-family ownership structure on the agency cost of debt. We find that founding-family ownership is common in large, publicly traded firms and is related, both statistically and economically, to a lower cost of debt financing. The evidence also indicates that the relation between founding-family holdings and debt costs is non-monotonic; debt costs first decrease as family ownership increases but then increase with increasing family ownership. However, irrespective of the level of family holdings, we find that family firms enjoy a lower cost of debt than non-family firms. These results are consistent with the hypothesis that continued founding-family ownership in publicly traded firms reduces the agency costs of debt. Additional analysis reveals that when a family member serves as the firm's CEO, the cost of debt financing is higher than if an outsider is CEO, but still lower than in non-family firms. Overall, the results are consistent with the idea that founding-family firms have incentive structures that result in fewer agency conflicts between equity and debt claimants, suggesting that bond investors view founding-family ownership as an organizational structure that better protects their interests.
TL;DR: In this article, the authors examined the relationship between the stock price synchronicity and analyst activity in emerging markets and found that returns on high analyst-following portfolio lead returns on low analyst following portfolio more than vice versa.
Abstract: This paper examines the relationship between the stock price synchronicity and analyst activity in emerging markets. Contrary to conventional wisdom that suggests that security analysts specialize in the production of firm-specific information, we find that the security analysts predominantly produce market-wide information. Using the R-square statistics of the market model as a measure of the synchronicity of stock price movements, we find that more analyst coverage leads to an increase in stock price synchronicity. Furthermore, after controlling for the influence of firm size on the lead-lag relation, we find that returns on high analyst-following portfolio lead returns on low analyst-following portfolio more than vice versa. We also find that the aggregate changes in the earnings forecast of high analyst-following portfolio affect the aggregate returns of the portfolio itself as well as the the low analyst-following portfolio while the aggregate changes in the earnings forecasts of low analyst-following portfolio have no predictive ability. Finally, when the forecast dispersion is high, the effect of analyst coverage on stock price synchronicity is reduced.
Proceedings Article•
08 Jul 2002TL;DR: This paper shows that the problem of identifying documents from a set of documents of a particular topic or class P and a large set M of mixed documents, and that under appropriate conditions, solutions to the constrained optimization problem will give good solution to the partially supervised classification problem.
Abstract: We investigate the following problem: Given a set of documents of a particular topic or class P , and a large set M of mixed documents that contains documents from class P and other types of documents, identify the documents from class P in M . The key feature of this problem is that there is no labeled nonP document, which makes traditional machine learning techniques inapplicable, as they all need labeled documents of both classes. We call this problem partially supervised classification. In this paper, we show that this problem can be posed as a constrained optimization problem and that under appropriate conditions, solutions to the constrained optimization problem will give good solutions to the partially supervised classification problem. We present a novel technique to solve the problem and demonstrate the effectiveness of the technique through extensive experimentation.
TL;DR: In this article, a unique blend of starch-based polymer powders (cornstarch, dextran and gelatin) was developed for the 3D printing of cylindrical scaffolds.
TL;DR: Observations indicate that RGL2 is a negative regulator of GA responses that acts specifically to control seed germination rather than stem elongation, and as R GL2 expression is imbibition inducible, RGL 2 may function as an integrator of environmental and endogenous cues to control Seed germination.
Abstract: The germination of Arabidopsis seeds is promoted by gibberellin (GA). Arabidopsis GAI, and RGA are genes encoding key GA signal-transduction components (GAI and RGA) that mediate GA regulation of stem elongation. The Arabidopsis genome contains two further genes, RGL1 and RGL2, that encode proteins (RGL1 and RGL2) that are closely related to GAI and RGA. Here, we show that RGL2 regulates seed germination in response to GA, and that RGL1, GAI, and RGA do not. In addition, we show that RGL2 transcript levels rise rapidly following seed imbibition, and then decline rapidly as germination proceeds. In situ GUS staining revealed that RGL2 expression in imbibed seeds is restricted to elongating regions of pre-emergent and recently emerged radicles. These observations indicate that RGL2 is a negative regulator of GA responses that acts specifically to control seed germination rather than stem elongation. Furthermore, as RGL2 expression is imbibition inducible, RGL2 may function as an integrator of environmental and endogenous cues to control seed germination.
TL;DR: In this article, lead adsorption on chitosan/PVA beads was found to be strongly pH-dependent and displayed a maximum uptake capacity at pH around 4 and a minimum at pH about 6.4.
Abstract: Removal of lead from aqueous solution with chitosan/PVA (poly(vinyl alcohol)) hydrogel beads was studied in batch adsorption experiments at various solution pH values (2−7.6). Lead adsorption on chitosan/PVA beads was found to be strongly pH-dependent and displayed a maximum uptake capacity at pH around 4 and a minimum at pH about 6.4. ζ-Potential study indicated that chitosan/PVA beads possessed positive ζ-potentials at pH 6.3. Hence, adsorption occurred even though the interaction between lead and chitosan/PVA beads was electrostatically repulsive at pH < 6.3. Complexation, ion exchange, and electrostatic interaction are all believed to play a role in lead adsorption on chitosan/PVA beads, but the relative importance of each of these mechanisms varies with solution pH values. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy spectra suggested that lead adsorption was mainly through interactions with the N atoms in chitosan in the pH rang...
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.
TL;DR: A reliable robust tracking controller design method is developed based on the mixed linear quadratic (LQ)//H/sub /spl infin// tracking performance index and multiobjective optimization in terms of linear matrix inequalities.
Abstract: This paper studies the reliable robust tracking controller design problem against actuator faults and control surface impairment for aircraft. First, models of actuator faults and control surface impairment are presented. Then a reliable robust tracking controller design method is developed. This method is based on the mixed linear quadratic (LQ)//H/sub /spl infin// tracking performance index and multiobjective optimization in terms of linear matrix inequalities. Flight control examples are given, and both linear and nonlinear simulations are given.