Showing papers by "Hong Kong Baptist University published in 1997"

The relationship between the distribution of electronic states and the optical absorption spectrum of an amorphous semiconductor: An empirical analysis

Abstract: An elementary empirical model for the distribution of electronic states of an amorphous semiconductor is presented. Using this model, we determine the functional form of the optical absorption spectrum, focusing our analysis on the joint density of states function, which dominates the absorption spectrum over the range of photon energies we consider. Applying our optical absorption results, we then determine how the empirical measures commonly used to characterize the absorption edge of an amorphous semiconductor, such as the Tauc gap and the absorption tail breadth, are related to the parameters that characterize the underlying distribution of electronic states. We, thus, provide the experimentalist with a quantitative means of interpreting the physical significance of their optical absorption data.

Neural network applications in business: a review and analysis of the literature (1988-95)

Abstract: A survey of journal articles on neural network business applications published between 1988 and 1995 indicates that an increasing amount of neural network research is being conducted for a diverse range of business activities. The classification of literature by (1) year of publication, (2) application area, (3) problem domain, (4) decision process phase, (5) level of management, (6) level of task interdependence, (7) means of development, (8) corporate/academic interaction in development, (9) technology integration, (10) comparative study, (11) major contribution, and (12) journal provides some insights into the trends in neural networks research. The implications for neural networks developers/researchers and suggestions on future research areas are discussed.

Zinc, lead and cadmium tolerance, uptake and accumulation by Typha latifolia

Abstract: summary Zinc, lead and cadmium tolerance in four populations of Typha latifolia raised from seed collected from metal-contaminated and uncontaminated sites were investigated. Metal concentrations in natural plant populations showed that Zn, Pb and Cd in the leaves were maintained at low levels (Zn: 22–122, Pb: 4.7–40 and Cd: 0.2–0.8 μg g−1 d. wt), although concentrations of these metals in the associated soil-sediments (total concentrations of Zn: 86–3009, Pb: 26–18894 and Cd: 1.4–26 μg−1 d. wt) and in the roots (Zn: 46–946, Pb: 25–3628 and Cd: 1.0–17 μg g−1 d. wt) varied widely. Some differences were found between metal-contaminated and uncontaminated populations in terms of metal uptake under controlled conditions. Seedlings from metal-contaminated populations accumulated considerably more metals (up to nearly twice as much Zn and Pb and three times as much Cd) in roots than the uncontaminated population in a pot trial. In general, however, different populations of T. latifolia showed similar growth responses (the longest leaf elongation, the longest root elongation, shoot and root d. wt), metal uptake and indices of metal tolerance when seedlings were grown in the same metal treatment solutions or in the same metal-contaminated media under laboratory conditions. The data do not support the hypothesis that populations from metal-contaminated sites have evolved tolerance to Zn, Pb and Cd, but rather that T. latifolia shows constitutional tolerance.

Organizational Socialization: a Multidomain, Continuous Process Model

Abstract: This paper presents a model of organizational socialization (OS) as a process with four domains (spheres of activity containing multiple factors or dimensions) which evolve concurrently during one's tenure. The domains are: (1) Training; (2) Understanding (of one's job and organization); (3) Coworker Support; and (4) Future Prospects (in the employing organization). Each domain is discussed in terms of its: (a) definition and components; (b) rationale for inclusion; (c) continuous nature; (d) hypothesized correlates; and (e) relevance for HRM practitioners. Together, the domains compose a continuous-process model which provides a framework for organizing theoretical elements and for classifying the diverse variables used in OS research.

Quantum interference effects in spontaneous emission from an atom embedded in a photonic band gap structure

Abstract: The spontaneous emission from a three-level atom embedded in a photonic band gap structure is studied. Interference between two transitions leads to quasiperiodic oscillations of population between the two upper levels with large amplitudes. The spontaneous emission of the atom is characterized by three components in the radiated field: a localized part, a traveling pulse, and a $(1/\sqrt{t}{)}^{3}$ decaying part. An analytical expression for the localization distance of the localized field is obtained. The energy velocity for the traveling pulse could be close to zero. By selecting an appropriate initial superposition state, a large amount of population trapping can be achieved.

Ammonia stripping as a pretreatment for landfill leachate

Abstract: The effectiveness of ammonia stripping at different air flow rates (0, 1 and 5 L min−1) and lime dosages (0 and 10 000 mg L−1 calcium hydroxide) was investigated in aeration tanks in a laboratory as a pretreatment to remove ammoniacal-nitrogen and organic load (COD) in landfill leachate. Ammoniacal-nitrogen removal at 20°C after one day was 70% for 0 L min−1, 81% for 1 L min−1 and 90% for 5 L min−1 regardless of the origin of leachate. Ammonia loss was mainly due to desorption through water surface. The levels of phosphorus and COD were only reduced by lime precipitation, with 85% and 93% phosphorus removal and 24% and 47% COD removed for leachate from the Junk Bay Landfill (JB) and Gin Drinkers' Bay Landfill (GDB) respectively. The highly significant difference (P<0.05) of COD removal between JB and GDB might be due to the different age of the two landfills studied. Leachate quality and configuration of the treatment reactor were important factors affecting the efficiency of ammonia removal by stripping processes.

Copper and nickel uptake, accumulation and tolerance in Typha latifolia with and without iron plaque on the root surface

Abstract: summary The effects of iron plaque on the growth of Typha latifolia L. and accumulation of copper and nickel in T. latifolia were investigated under laboratory conditions in nutrient solution cultures. Seedlings with and without iron plaque on their roots were exposed to 0.05 μg ml−1 Cu and 0.10 μg ml−1 Ni solutions for 72 d. The results showed no differences in root and shoot d. wt and leaf elongation when Cu or Ni were added to the solution and in the presence or absence of plaque. However, root length was reduced by Cu and Ni, and the reduction in root length was greater in the presence of plaque. Some Cu and Ni was adsorbed on root surfaces; roots with plaque took up more Cu, but less Ni than those without. The presence of plaque did not alter Cu uptake and translocation but increased Ni uptake and translocation. Most of the Cu and Ni taken up was retained in the roots, suggesting that the root tissue rather than the root surface or plaque is the main barrier for Cu and Ni transport. The results differ from those reported for other species.

Quenching of spontaneous emission via quantum interference

Abstract: A four-level atom, driven by a coherent field, is considered. We show that under certain conditions complete quenching of spontaneous emission is possible. Hence the population inversion on some specific atomic transitions can be created using a very weak incoherent pumping. We investigate the physics of the effect using bare and dressed states. The proposed scheme may be useful, in principle, for generation of high-frequency and/or high power laser light.

The separateness‐connectedness self‐schema: Scale development and application to message construction

Abstract: Two studies were conducted to assess separateness-connectedness (SC) as a new message variable and as a new individual difference variable in advertising. Study I began the process of developing a Separateness-Connectedness scale based on a sample of 140 college students (97 Westerners and 43 non-Westerners, 81 males and 59 females) attending a midwestern university. The 9-item, 2-factor scale revealed good reliability and construct validity. The structure of the overall model was then successfully tested on a new sample by confirmatory factor analysis. In Study II an experiment assessed whether the separateness/connectedness self-schema would moderate the effect of using either a connected or a separated advertising appeal on consumers' attitude toward the ad. As predicted, a significant interaction effect was found. The results revealed that individuals with a separate self-schema preferred a separated advertising theme, and individuals with a connected self-schema preferred a connected advertising theme. Implications for advertising managers, the studies' limitations, and future research directions are also discussed. © 1997 John Wiley & Sons, Inc.

An evolutionary autonomous agents approach to image feature extraction

Abstract: This paper presents a new approach to image feature extraction which utilizes evolutionary autonomous agents. Image features are often mathematically defined in terms of the gray-level intensity at image pixels. The optimality of image feature extraction is to find all the feature pixels from the image. In the proposed approach, the autonomous agents, being distributed computational entities, operate directly in the 2-D lattice of a digital image and exhibit a number of reactive behaviors. To effectively locate the feature pixels, individual agents sense the local stimuli from their image environment by means of evaluating the gray-level intensity of locally connected pixels, and accordingly activate their behaviors. The behavioral repository of the agents consists of: 1) feature-marking at local pixels and self-reproduction of offspring agents in the neighboring regions if the local stimuli are found to satisfy feature conditions, 2) diffusion to adjacent image regions if the feature conditions are not held, or 3) death if the agents exceed their life span. As part of the behavior evolution, the directions in which the agents self-reproduce and/or diffuse are inherited from the directions of their selected high-fitness parents. Here the fitness of a parent agent is defined according to the steps that the agent takes to locate an image feature pixel.

Regression estimator in ranked set sampling

Abstract: Ranked set sampling (RSS) utilizes inexpensive auxiliary information about the ranking of the units in a sample to provide a more precise estimator of the population mean of the variable of interest Y, which is either difficult or expensive to measure. However, the ranking may not be perfect in most situations. In this paper, we assume that the ranking is done on the basis of a concomitant variable X. Regression-type RSS estimators of the population mean of Y will be proposed by utilizing this concomitant variable X in both the ranking process of the units and the estimation process when the population mean of X is known. When X has unknown mean, double sampling will be used to obtain an estimate for the population mean of X. It is found that when X and Y jointly follow a bivariate normal distribution, our proposed RSS regression estimator is more efficient than RSS and simple random sampling (SRS) naive estimators unless the correlation between X and Y is low (/rho/ < 0.4). Moreover, it is always superior to the regression estimator under SRS for all rho. When normality does not hold, this approach could still perform reasonably well as long as the shape of the distribution of the concomitant variable X is only slightly departed from symmetry. For heavily skewed distributions, a remedial measure will be suggested. An example of estimating the mean plutonium concentration in surface soil on the Nevada Test Site, Nevada, U.S.A., will be considered.

Spectrochemical Analysis of Liquids Using Laser-Induced Plasma Emissions: Effects of Laser Wavelength on Plasma Properties:

Abstract: We spectroscopically determined the temperature and electron density of the plasma plumes produced by pulsed-laser ablation of aqueous solutions containing sodium, lithium, and rubidium. With the use of a Nd:YAG laser at 532 nm and fluence of 3 J/cm2, the plasma produced was hot (low eV range) and extensively ionized, with electron density in the 1018 cm -3 range. Analyte line signals were initially masked by intense plasma continuum emissions and would only emerge briefly above the background when the plume temperature dropped below 1 eV during the course of its very rapid cooling. Since ionization was thermally induced, the intense plasma flash was inevitable. In contrast, 193-nm laser ablation at similar fluence generated plasmas of much lower ( < 1 eV) temperature but comparable electron density. Plasma continuum emissions were relatively weak, and the signal-to-background ratio was a thousand times better. Consequently, this ''cold'' plasma was ideal for sampling biologically important elements such as sodium, potassium, and calcium.

Carbon dioxide reforming of methane to syngas over SiO2-supported rhodium catalysts

Abstract: The decomposition of CH4 and CO2 as well as the reaction between CH4 and CO2 over SiO2-supported rhodium catalysts has been investigated in the temperature range of 600–800°C over a pulse reactor. The initial activities for methane decomposition and CO2 decomposition increased with the increase of rhodium loading; whereas the activity for CO formation in the CH4+CO2 reaction was almost unaffected by the rhodium loading over catalysts with rhodium loading >0.05%. Different reaction behaviors of methane reforming with CO2 were observed at 700°C and 800°C. At 700°C, CO2 conversion was higher than CH4 conversion; whereas at 800°C, CH4 conversion was higher than CO2 conversion. The bond order conservation-Morse potential (BOCMP) calculations indicate that the oxygen at on-top site can promote the dissociation of methane on the Rh(111) surface. Normal deuterium isotope effect was observed to be more noticeable on the methane conversion reaction than on the CO formation reaction, while no such effect was observed on the CO2 conversion reaction. The mechanism for CO and H2 formation in the reforming of methane with CO2 is discussed based on the results of the present work.

Spectrochemical analysis of liquids using laser-induced plasma emissions: effects of laser wavelength

Abstract: The plasma plume emissions produced by pulsed ( ~ 10 ns) laser ablation of liquid jets were monitored for spectrochemical analysis. Laser wavelengths at 532 and 193 nm were used, and sodium was the test analyte. As expected, the 532-nm laser pulse produced very intense plasma continuum emissions that masked the sodium signal for the first hundred nanoseconds, especially near the bright core of the vapor plume. Neither time-gating nor spatial masking could significantly improve the single-shot signal-to-noise ratio, since the transient nature of the emissions placed stringent demands on timing precision while the small size of the plume required accurate mask positioning-both antithetical to the inherent instability of jet ablation. In sharp contrast, the 193-nm laser pulse produced relatively dim plasma flash but intense sodium emissions, rendering it ideal for analytical applications.

Feasibility of Using Coal Ash Residues as CO-Composting Materials for Sewage Sludge

Abstract: Alkaline coal ash residues produced from a coal-fired power plant were co-composted with sewage sludge to evaluate it's effect on heavy metal availability and the biological process of composting. Coal fly ash (FA) and lagoon ash (LA) were mixed with dewatered sludge at 0, 10 and 25% w/w, and the mixtures were composted for 100 days in laboratory batch reactors. The changes in pH, electrical conductivity (EC), CO2 production, microbial population, soluble and extractable heavy metal contents were measured during the composting period. Following an initial increase, pH started to decrease from day 7 onward till the end of the composting period for all treatments. Sludge with coal fly ash amendment had a higher pH and EC than those of the control and LA-sludge composts. Increasing fly ash amendment levels resulted in a significant reduction in DTPA-extractable Cd, Cu, Zn, Mn and Pb contents of the FA-sludge composts while the reduction was less obvious in the LA-sludge composts. No significant difference in...

Quadrature Error Bounds with Applications to Lattice Rules

Abstract: Reproducing kernel Hilbert spaces are used to derive error bounds and worst-case integrands for a large family of quadrature rules. In the case of lattice rules applied to periodic integrands these error bounds resemble those previously derived in the literature. However, the theory developed here does not require periodicity and is not restricted to lattice rules. An analysis of variance (ANOVA) decomposition is employed in defining the inner product. It is shown that imbedded rules are superior when integrating functions with large high-order ANOVA effects.

Can stomatal closure caused by xylem aba explain the inhibition of leaf photosynthesis under soil drying

Abstract: Effects of leaf water deficit and increase in endogenous ABA on photosynthesis of two tropical trees, t Acacia confusa and t Leucaena leucocephala, were investigated with two soil-drying methods, i.e. half or whole root system was subjected to soil drying. Half-root drying was achieved by allowing upper layer of soil column to dry and lower layer of soil column to remain watered. Half-root drying had little effect on leaf water potential, but when compared to the well-watered control, both methods of soil drying substantially increased the ABA concentration in xylem and reduced leaf conductance in both species. There was a significant relationship between leaf conductance and xylem ABA concentrations in both species, which was comparable to the same relationship that was generated by feeding ABA to excised twigs. The rate of photosynthesis was inhibited substantially in both soil-drying treatments and in both species, but photochchemical efficiency, measured as a ratio of variable fluorescence to a peak fluorescence emission of a dark-adapted leaf (Fv/Fm), was not reduced except in the whole root-dried t L. leucocephala plants where leaf water potential was reduced to –2.5 MPa. In all the cases where photosynthesis was inhibited, there was a concomitant reduction in both leaf conductance and calculated internal CO2 concentration. After two days of rewatering, leaf water potential and xylem ABA concentration rapidly returned to pre-treatment levels, but leaf conductance and photosynthesis of both whole-root and half root dried t L. leucocephala remained inhibited substantially. Rewatering led to a full recovery of both stomatal conductance and photosynthesis in soil-dried t A. confusa, although its photosynthesis of whole-root dried plants did not recover fully but such difference was not significant statistically. These results suggest that drought-induced decline of photosynthesis was mainly a result of the stomatal factor caused by the increase of ABA concentration in the xylem sap. Non-stomatal factors, e.g. reduced photochemical activity and/or carbon metabolic activity, were species-specific and were brought about only at very low water potential.

Interactive bilevel multi-objective decision making

Abstract: From a perspective of non-linear bilevel multi-objective decision-making problem (BMDMP) of the leader-follower Stackelberg game, this paper presents a two-person bilevel multi-objective decision-making model and an interactive algorithm for solving the problem. The algorithm simplifies a BMDMP by transforming it into separate multi-objective decision-making problems at the upper- and lower-levels, thereby avoiding the difficulty associated with non-convex mathematical programming to arrive at an optimal solution. In addition, the authors put forward the satisfactoriness concept as the upper level decision maker's preference. The algorithm facilitates the interactive nature of bilevel multi-objective decision making for non-inferior solutions. Thus, the algorithm provides a way to solve BMDMP.

Generic products: who buys them and how do they perform relative to each other?

Abstract: Branding has traditionally been viewed as an essential tool for marketers to establish an identity for their products. Even products among the commodity range make use of branding to establish a position for themselves in the market. Recent times, however, have seen the emergence of unbranded or “generic” products. These products, which are usually sold at a price which is lower than their branded equivalents, are most often found in the area of low‐involvement grocery items. Previous studies of consumer perceptions suggest that while consumers see generics as being less expensive than their national branded equivalents, they are also seen as being inferior in quality. This research goes beyond comparing generic products to their national brand equivalents by comparing generic products to one another, in order to ascertain whether the “low price‐low quality” perception is more applicable to some generic products than others. A mail survey of 1,000 New Zealanders revealed that, in contrast to previous studies, generic consumers tend to be older and on a lower household income. The more standardized generics (such as rice) received more favourable ratings than the more processed generics such as coffee and shampoo, although there were significant differences in the respondents’ perceptions across different demographic groups. The results suggest that it is unwise for marketers to draw sweeping conclusions about consumer perceptions of generic products in general. Rather, each generic product, when compared with other generic products, has its own consumer perception and, therefore, each generic product requires different attention from different elements of the marketing mix.