Showing papers by "University of Texas at Arlington published in 2002"
TL;DR: In this article, the authors propose a comprehensive store choice model that includes three types of store environment cues (social, design, and ambient) as exogenous constructs, various store choice criteria (including shopping experience costs that heretofore have not been included in store choice models) as mediating constructs, and store patronage intentions as the endogenous construct.
Abstract: Research on how store environment cues influence consumers’ store choice decision criteria, such as perceived merchandise value and shopping experience costs, is sparse. Especially absent is research on the simultaneous impact of multiple store environment cues. The authors propose a comprehensive store choice model that includes (1) three types of store environment cues (social, design, and ambient) as exogenous constructs, (2) various store choice criteria (including shopping experience costs that heretofore have not been included in store choice models) as mediating constructs, and (3) store patronage intentions as the endogenous construct. They then empirically examine the extent to which environmental cues influence consumers’ assessments of a store on various store choice criteria and how those assessments, in turn, influence patronage intentions. The results of two different studies provide support for the model. The authors conclude by discussing the results to develop an agenda for addit...
2,088 citations
TL;DR: An on-demand distributed clustering algorithm for multi-hop packet radio networks that takes into consideration the ideal degree, transmission power, mobility, and battery power of mobile nodes, and is aimed to reduce the computation and communication costs.
Abstract: In this paper, we propose an on-demand distributed clustering algorithm for multi-hop packet radio networks. These types of networks, also known as i>ad hoc networks, are dynamic in nature due to the mobility of nodes. The association and dissociation of nodes to and from i>clusters perturb the stability of the network topology, and hence a reconfiguration of the system is often unavoidable. However, it is vital to keep the topology stable as long as possible. The i>clusterheads, form a i>dominant set in the network, determine the topology and its stability. The proposed weight-based distributed clustering algorithm takes into consideration the ideal degree, transmission power, mobility, and battery power of mobile nodes. The time required to identify the clusterheads depends on the diameter of the underlying graph. We try to keep the number of nodes in a cluster around a pre-defined threshold to facilitate the optimal operation of the medium access control (MAC) protocol. The non-periodic procedure for clusterhead election is invoked on-demand, and is aimed to reduce the computation and communication costs. The clusterheads, operating in “dual" power mode, connects the clusters which help in routing messages from a node to any other node. We observe a trade-off between the uniformity of the load handled by the clusterheads and the connectivity of the network. Simulation experiments are conducted to evaluate the performance of our algorithm in terms of the number of clusterheads, i>reaffiliation frequency, and dominant set updates. Results show that our algorithm performs better than existing ones and is also tunable to different kinds of network conditions.
1,419 citations
TL;DR: Both model-based and real trace simulation studies show that the proposed cooperative architecture results in more than 50% memory saving and substantial central processing unit (CPU) power saving for the management and update of cache entries compared with the traditional uncooperative hierarchical caching architecture.
Abstract: This paper aims at finding fundamental design principles for hierarchical Web caching. An analytical modeling technique is developed to characterize an uncooperative two-level hierarchical caching system where the least recently used (LRU) algorithm is locally run at each cache. With this modeling technique, we are able to identify a characteristic time for each cache, which plays a fundamental role in understanding the caching processes. In particular, a cache can be viewed roughly as a low-pass filter with its cutoff frequency equal to the inverse of the characteristic time. Documents with access frequencies lower than this cutoff frequency have good chances to pass through the cache without cache hits. This viewpoint enables us to take any branch of the cache tree as a tandem of low-pass filters at different cutoff frequencies, which further results in the finding of two fundamental design principles. Finally, to demonstrate how to use the principles to guide the caching algorithm design, we propose a cooperative hierarchical Web caching architecture based on these principles. Both model-based and real trace simulation studies show that the proposed cooperative architecture results in more than 50% memory saving and substantial central processing unit (CPU) power saving for the management and update of cache entries compared with the traditional uncooperative hierarchical caching architecture.
512 citations
TL;DR: For example, this paper found that agreeableness and extraversion were associated with both peer acceptance and friendship in middle school children, and that this dimension was associated with motives to maintain positive interpersonal relations.
305 citations
TL;DR: The methodology develops and applies a combination of multi-criteria efficiency models, based on game theory concepts, and linear and integer programming methods for effective supply chain design.
270 citations
TL;DR: By building and maintaining a dictionary of individual user's path updates, the proposed adaptive on-line algorithm can learn subscribers' profiles and compressibility of the variable-to-fixed length encoding of the acclaimed Lempel–Ziv family of algorithms reduces the update cost.
Abstract: The complexity of the mobility tracking problem in a cellular environment has been characterized under an information-theoretic framework. Shannon's entropy measure is identified as a basis for comparing user mobility models. By building and maintaining a dictionary of individual user's path updates (as opposed to the widely used location updates), the proposed adaptive on-line algorithm can learn subscribers' profiles. This technique evolves out of the concepts of lossless compression. The compressibility of the variable-to-fixed length encoding of the acclaimed Lempel---Ziv family of algorithms reduces the update cost, whereas their built-in predictive power can be effectively used to reduce paging cost.
227 citations
TL;DR: In this paper, the authors explore different mobility management schemes from the perspective of VoIP services, with a focus on Mobile IP and session initiation protocol, and propose a shadow registration concept to reduce the interdomain handoff (macro-mobility) delay in the VoIP service in mobile environments.
Abstract: Wireless Internet access has gained significant attention as wireless/mobile communications and networking become widespread. The voice over IP service is likely to play a key role in the convergence of IP-based Internet and mobile cellular networks. We explore different mobility management schemes from the perspective of VoIP services, with a focus on Mobile IP and session initiation protocol. After illustrating the signaling message flows in these two protocols for diverse cases of mobility management, we propose a shadow registration concept to reduce the interdomain handoff (macro-mobility) delay in the VoIP service in mobile environments. We also analytically compute and compare the delay and disruption time for exchanging signaling messages associated with the Mobile IP and SIP-based solutions.
187 citations
TL;DR: The authors found that group brainstorming could be an effective technique for generating creative ideas, using an associative memory model of idea generation in groups, which suggests that groups have the potential to generate ideas that individuals brainstorming alone are less likely to generate.
Abstract: Much literature on group brainstorming has found it to be less effective than individual brainstorming. However, a cognitive perspective suggests that group brainstorming could be an effective technique for generating creative ideas. Computer simulations of an associative memory model of idea generation in groups suggest that groups have the potential to generate ideas that individuals brainstorming alone are less likely to generate. Exchanging ideas by means of writing or computers, alternating solitary and group brainstorming, and using heterogeneous groups appear to be useful approaches for enhancing group brainstorming.
186 citations
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TL;DR: In this article, the authors provide a reality check by undoing 10 of these turbidite myths, including: 1) turbidity currents are high-velocity flows with multiple sediment-support mechanisms, and 2) flute structures are indicative only of flow erosion, not deposition.
178 citations
TL;DR: Escherichia coli zupT (ygiE), encoding a ZIP family member, mediated zinc uptake and cells expressing ZupT from a plasmid exhibited increased uptake of (65)Zn(2+).
Abstract: Escherichia coli zupT (ygiE), encoding a ZIP family member, mediated zinc uptake. Growth of cells disrupted in both zupT and the znuABC operon was inhibited by EDTA at a much lower concentration than a single mutant or the wild type. Cells expressing ZupT from a plasmid exhibited increased uptake of 65Zn2+.
177 citations
TL;DR: This article used the Compustat Industry Segment database to identify and analyze a sample of firms that begin the study period as single-segment entities and then subsequently choose to diversify.
Abstract: There is substantial evidence to suggest that the market placed a lower value on diversified firms than on specialized firms during the 1980s, yet many firms diversified anyway. This article addresses why firms diversify in the first place. We use the Compustat Industry Segment database in order to identify and analyze a sample of firms that begin the study period as single-segment entities and then subsequently choose to diversify. We find evidence to support two of three possible agency cost hypotheses. Not all reported segment changes represent true economic events. Moreover, analysis of the differences between true economic diversifiers and firms whose segment change represents a nonsubstantive reporting change suggests that inadvertent inclusion of the latter in diversification studies may bias results, especially with respect to firm liquidity and q.
TL;DR: The authors in this article pointed out that the distribution puzzle is not only faced by foreign firms, but also by Chinese firms that operate nationwide, and that there are three main forces that are changing and modernizing China's distribution and logistics system.
Abstract: Prior to the economic reform movement, China’s centrally planned, three‐tier system dominated the distribution sector. After the 1980s, this system gradually shifted away from the socialist mode to the free market mode. Today, China’s distribution system lies somewhere between these two modes. Since the reform, China’s government has been encouraging export‐oriented foreign firms’ investments in free trade zones along the coast. Foreign firms do not enjoy the same inland distribution and logistics rights as their Chinese counterparts. However, the distribution puzzle is not only faced by foreign firms, but also by Chinese firms that operate nationwide. China’s undeveloped infrastructure, government regulations, and regional protectionism fragment distribution channels throughout China. However, there are three main forces that are changing and modernizing China’s distribution and logistics system. These are the booming economy, entering the WTO and e‐commerce. The inevitable revolution of China’s distribution and logistics system is on the way.
TL;DR: It is shown here how a certain class of augmented NN, capable of approximating piecewise continuous functions, can be used for friction compensation.
Abstract: One of the most important properties of neural nets (NNs) for control purposes is the universal approximation property. Unfortunately,, this property is generally proven for continuous functions. In most real industrial control systems there are nonsmooth functions (e.g., piecewise continuous) for which approximation results in the literature are sparse. Examples include friction, deadzone, backlash, and so on. It is found that attempts to approximate piecewise continuous functions using smooth activation functions require many NN nodes and many training iterations, and still do not yield very good results. Therefore, a novel neural-network structure is given for approximation of piecewise continuous functions of the sort that appear in friction, deadzone, backlash, and other motion control actuator nonlinearities. The novel NN consists of neurons having standard sigmoid activation functions, plus some additional neurons having a special class of nonsmooth activation functions termed "jump approximation basis function." Two types of nonsmooth jump approximation basis functions are determined- a polynomial-like basis and a sigmoid-like basis. This modified NN with additional neurons having "jump approximation" activation functions can approximate any piecewise continuous function with discontinuities at a finite number of known points. Applications of the new NN structure are made to rigid-link robotic systems with friction nonlinearities. Friction is a nonlinear effect that can limit the performance of industrial control systems; it occurs in all mechanical systems and therefore is unavoidable in control systems. It can cause tracking errors, limit cycles, and other undesirable effects. Often, inexact friction compensation is used with standard adaptive techniques that require models that are linear in the unknown parameters. It is shown here how a certain class of augmented NN, capable of approximating piecewise continuous functions, can be used for friction compensation.
29 Jan 2002
TL;DR: In this paper, the authors describe the dynamics of photo-induced charge transfer and charge storage behavior in the dark in the context of Semiconductor-electrolyte interfaces.
Abstract: The sections in this article are
Introduction and Scope
Electron Energy Levels in Semiconductors and Energy Band Model
The Semiconductor–Electrolyte Interface at Equilibrium
The Equilibration Process
The Depletion Layer
Mapping of the Semiconductor Band-edge Positions Relative to Solution Redox Levels
Surface States and Other Complications
Charge Transfer Processes in the Dark
Current-potential Behavior
Dark Processes Mediated by Surface States or by Space Charge Layer Recombination
Rate-limiting Steps in Charge Transfer Processes in the Dark
Light Absorption by the Semiconductor Electrode and Carrier Collection
Light Absorption and Carrier Generation
Carrier Collection
Photocurrent-potential Behavior
Dynamics of Photoinduced Charge Transfer
Hot Carrier Transfer
Multielectron Photoprocesses
Nanocrystalline Semiconductor Films and Size Quantization
Introductory Remarks
The Nanocrystalline Film–Electrolyte Interface and Charge Storage Behavior in the Dark
Photoexcitation and Carrier Collection: Steady State Behavior
Photoexcitation and Carrier Collection: Dynamic Behavior
Size Quantization
Chemically Modified Semiconductor–Electrolyte Interfaces
Single Crystals
Nanocrystalline Semiconductor Films and Composites
Types of Photoelectrochemical Devices
Conclusion
Acknowledgments
TL;DR: It is proposed that the human IPL+STG has a top-down control role, contributing to the functions of both dorsal and ventral visual systems, and this is consistent with a role that is neither strictly "dorsal" nor "ventral".
TL;DR: In this article, the authors examined personality and cognitive assessments associated with impairments in self-regulation and found that Effortful Control is a common developmental substrate of Agreeableness and Conscientiousness.
TL;DR: In this article, the authors discuss the relationships between discrimination, harassment, and the glass ceiling, arguing that many of the factors that preclude women from occupying executive and managerial positions also foster sexual harassment.
Abstract: In this article, we discuss the relationships between discrimination, harassment, and the glass ceiling, arguing that many of the factors that preclude women from occupying executive and managerial positions also foster sexual harassment. We suggest that measures designed to increase numbers of women in higher level positions will reduce sexual harassment. We first define and discuss discrimination, harassment, and the glass ceiling, relationships between each, and relevant legislation. We next discuss the relationships between gender and sexual harassment, emphasizing the influence of gender inequality on sexual harassment. We then present recommendations for organizations seeking to reduce sexual harassment, emphasizing the role that women executives may play in such efforts and, importantly, the recursive effects of such efforts on increasing the numbers of women in higher level positions in organizations.
TL;DR: In a factorial field experiment, this paper found that despite high statistical power (n = 1,200, 1-β≥.95), none of the conventional response-rate enhancement techniques were effective.
TL;DR: In this paper, the substitutability of fixed and mobile services for telecommunications access using a large, U.S. household survey conducted over the period 2000-2001 was empirically estimated.
Abstract: We empirically estimate the substitutability of fixed and mobile services for telecommunications access using a large, U.S. household survey conducted over the period 2000-2001. Estimated cross-price elasticities confirm that second fixed line and mobile services are substitutes for one another. The extent of fixed-mobile substitution has important implications for policy toward fixed network unbundling, fixed-mobile vertical separation, and universal service.
TL;DR: The authors found that generic drug prices fall with the number of competitors, but remain above long-run marginal cost until there are eight or more competitors, and that the size and time paths of generic revenues, rents and the numbers of firms are greatly affected by measures reflecting the expected market size.
Abstract: Because of its unique institutional and regulatory features, the generic drug industry provides a useful laboratory for understanding how competition evolves within a market. We exploit these features to estimate a system of structural relationships in this industry, including the relationship between price and the number of competitors, and between drug characteristics and the entry process. Our methodology yields a number of findings regarding industry dynamic effects. We find that generic drug prices fall with the number of competitors, but remain above long-run marginal cost until there are eight or more competitors. We also find the size and time paths of generic revenues, rents and the number of firms are greatly affected by measures reflecting the expected market size. An advantage of estimating a system of structural equations is that we can determine how a change in an exogenous variable will affect the equilibrium. We exploit this property to evaluate recent policy changes toward the pharmaceutical industry.
TL;DR: The NblS protein appears to be a membrane-bound, PAS-domain-bearing, sensor histidine kinase of two-component regulatory systems in bacteria involved in the control of a number of processes critical for altering the photosynthetic apparatus in response to both HL and nutrient stress conditions.
Abstract: The HliA protein of the cyanobacterium Synechococcus elongatus PCC 7942 is a small, thylakoid-associated protein that appears to play a role in photoprotection; its transcript rapidly accumulates in response to high-intensity light (HL) and the hli gene family is required for survival of cells in high light In order to discover regulatory factors involved in HL acclimation in cyanobacteria, a screen was performed for chemically generated mutants unable to properly control expression of the hliA gene in response to HL One such mutant was identified, and complementation analysis led to the identification of the affected gene, designated nblS Based on its deduced protein sequence, NblS appears to be a membrane-bound, PAS-domain-bearing, sensor histidine kinase of two-component regulatory systems in bacteria The nblS mutant was unable to properly control light intensity-mediated expression of several other photosynthesis-related genes, including all three psbA genes and the cpcBA genes The mutant was also unable to control expression of the hliA and psbA genes in response to low-intensity blue/UV-A light, a response that may be related to the HL-mediated regulation of the genes Additionally, in response to nutrient deprivation, the nblS mutant was unable to properly control accumulation of the nblA transcript and associated degradation of the light-harvesting phycobilisomes The nblS mutant dies more rapidly than wild-type cells following exposure to HL or nutrient deprivation, likely due to its inability to properly acclimate to these stress conditions Thus, the NblS protein is involved in the control of a number of processes critical for altering the photosynthetic apparatus in response to both HL and nutrient stress conditions
17 Nov 2002
TL;DR: It is shown how genetic algorithms can be useful in enhancing the performance of clustering algorithms in mobile ad hoc networks, and the recently proposed weighted clustering algorithm (WCA) is optimized.
Abstract: We show how genetic algorithms can be useful in enhancing the performance of clustering algorithms in mobile ad hoc networks In particular, we optimize our recently proposed weighted clustering algorithm (WCA) The problem formulation along with the parameters are mapped to individual chromosomes as input to the genetic algorithmic technique Encoding the individual chromosomes is an essential part of the mapping process; each chromosome contains information about the clusterheads and the members thereof, as obtained from the original WCA The genetic algorithm then uses this information to obtain the best solution (chromosome) defined by the fitness function The proposed technique is such that each clusterhead handles the maximum possible number of mobile nodes in its cluster in order to facilitate the optimal operation of the medium access control (MAC) protocol Consequently, it results in the minimum number of clusters and hence clusterheads Simulation results exhibit improved performance of the optimized WCA than the original WCA Moreover, the loads among clusters are more evenly balanced by a factor of ten
TL;DR: In this article, the authors present a table to assist in computing the eigenvalues of a multi-dimensional, multi-layer body with real and imaginary eigenfunctions, and a procedure to place a bound on the location of each eigenvalue.
TL;DR: A localized orbital model is proposed in which low-lying acceptor orbitals on the center portion of the ligands effectively quench the Ru(II)-based MLCT emission via a mechanism that can be viewed as intramolecular electron transfer to specific subunits of the bridges.
Abstract: Two new ruthenium(II) polypyridyl dimers containing the large planar aromatic bridging ligands 9,11,20,22-tetraazatetrapyrido[3,2-a:2‘3‘-c:3‘ ‘,2‘ ‘-l:2‘ ‘‘,3‘ ‘‘-n]pentacene (tatpp) and 9,11,20,22-tetraazatetrapyrido[3,2-a:2‘3‘-c:3‘ ‘,2‘ ‘-l:2‘ ‘‘,3‘ ‘‘-n]pentacene-10,21-quinone (tatpq) have been synthesized and characterized by 1H and 13C NMR, MALDI mass spectrometry, and elemental analyses. The electronic properties (UV−vis, redox, photophysical) of these dimers are analyzed in the context of orbital calculations (PM3 level) on the bridging ligands. A localized orbital model is proposed in which low-lying acceptor orbitals on the center portion of the ligands effectively quench the Ru(II)-based MLCT emission via a mechanism that can be viewed as intramolecular electron transfer to specific subunits of the bridges.
TL;DR: In this paper, water adsorption on a periodic model with both the local density approximation (LDA) and the generalized gradient approximation (GGA) of density-functional theory is studied.
Abstract: Water adsorption on a ${\mathrm{PuO}}_{2}(110)$ surface is studied using a periodic model with both the local-density approximation (LDA) and the generalized gradient approximation (GGA) of density-functional theory. The 60 core electrons of the Pu atom are represented by a relativistic effective core potential, and scalar relativistic effects have been incorporated into the valence orbitals. Both molecular and dissociative configurations of the adsorbate ${\mathrm{H}}_{2}\mathrm{O}$ are considered at one molecular layer coverage. For molecular water adsorption, LDA calculations indicate binding only at the top site, whereas the GGA indicates no binding for any site. Dissociative adsorption is found to be energetically more favorable than molecular adsorption, in agreement with experimental observations. The effects on the geometric and electronic structures influenced by water adsorption are investigated.
TL;DR: Early diagenetic pyrite forms as a result of microbial processes in sediments, but has received little attention as a potential source of microbial fossils as mentioned in this paper, which may greatly expand our knowledge of microbial life in the sedimentary record.
Abstract: Early diagenetic pyrite forms as a result of microbial processes in sediments, but has received little attention as a potential source of microbial fossils. Sedimentary pyrite grains, Archean to Jurassic in age, were examined by scanning and transmission electron microscopy (TEM). Ion milling was essential for the preparation of electron transparent TEM samples. Most pyrite grains revealed coccoid, rod-shaped, and even filamentous features that are interpreted as microbial. Identification of microbial remains in sedimentary pyrite may greatly expand our knowledge of microbial life in the sedimentary record. Combined with geochemical characterization, the study of pyritized microbes in the geologic record may in the future enable us to interpret changes in geochemical signatures more realistically in terms of different sulfate-reducing communities. Sedimentary pyrite grains may also represent a good prospect to further our knowledge of past life on Mars.
TL;DR: In this paper, a technique to obtain quantitative estimates of the concentration of hematite and goethite in loess and paleosol samples is reported using diffuse reflectance spectroscopy.
Abstract: The long, continuous deposition of dust in the Chinese loess plateau offers a unique opportunity to study the nature of Fe oxide formation in a wide range of climatic conditions. A technique to obtain quantitative estimates of the concentration of hematite and goethite in loess and paleosol samples is reported. Experiments using diffuse reflectance spectroscopy on sets of laboratory mixed and natural loess and paleosol samples show that it is possible to obtain rapid and quantitative estimates of the absolute concentration of hematite and goethite in the Chinese loess sediments. Typical loess and paleosol samples were deferrated using the CBD procedure to produce a natural matrix material to which hematite and goethite in known weight percentages were added to produce a set of calibration standards. Spectral violet, blue, green, yellow, orange, red and brightness of standards were calculated from the reflectance data and served as independent variables for a multiple linear regression analysis. The effect of changing matrix from loess to paleosol was overcome by including a variety of different loess and paleosol samples in the regression equations. The resulting calibration equations provide estimates of wt.% hematite and goethite and have correlation coefficients >0.93. The total measured hematite and goethite concentrations exhibited consistent variations with CBD extractable iron. Tests of the equations for buffering changes in matrix composition were run with samples of varying mineralogical composition (calcite, illite, etc.) and demonstrated that the equations are well buffered for changes in matrix composition from loess to paleosol.
TL;DR: In this article, the experience of a financial services company in managing its expatriation and repatriation processes is described, and the analysis indicates that some 50 percent of people left the company following the repatriation within a few years after return.
Abstract: The paper tells us about the experience of a financial services company in managing its expatriation and repatriation processes. Data were gathered from official company sources and via in‐depth interviews with former expatriates. The analysis indicates that some 50 percent of people left the company following the repatriation within a few years after return. The experience gained by the company manifests the importance of proper management of the processes of expatriation and in particular repatriation. To attain a successful expatriation and repatriation the management should handle both processes as an integrated part of career management, since expatriation can form a crucial point in the development of a psychological contract between the employee and the company.
TL;DR: It is argued that traveling down The Road Not Taken (apologies to Frost), that is, taking into consideration mating system and patterns of gamete utilization, leads to novel and more precise predictions of the circumstances under which reinforcement should occur.
Abstract: Reinforcement, a process whereby natural selection strengthens prezygotic isolation between sympatric taxa, has gained increasing attention from evolutionary biologists over the past decade. This resurgence of interest is remarkable given that, in the 1980s, most evolutionary biologists considered reinforcement to be, at best, a process that rarely occurred in nature. Although studies of reinforcement are now an important component of speciation research, we still lack a clear understanding of when reinforcement should occur. Theoretical models have suggested that genetic architecture, population structure and the type of selection influence the action of reinforcement. Still to be considered are the consequences of variation in mating system and patterns of sperm or pollen utilization on the likelihood of reinforcement. We argue that traveling down The Road Not Taken (apologies to Frost), that is, taking into consideration mating system and patterns of gamete utilization, leads to novel and more precise predictions of the circumstances under which reinforcement should occur.