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Showing papers by "Virginia Tech published in 1999"


Journal ArticleDOI
TL;DR: A major finding was that a destination image is formed by both stimulus factors and tourists' characteristics, which provides important implications for strategic image management and can aid in designing and implementing marketing programs for creating and enhancing tourism destination images.

2,817 citations


Journal ArticleDOI
TL;DR: In this article, an approach to the development of many-body interatomic potentials for monoatomic metals with improved accuracy and reliability is presented. But the functional form of the potentials is that of the embedded-atom method, but the interesting features are as follows: (1) the database used for the development a potential includes both experimental data and a large set of energies of different alternative crystalline structures of the material generated by ab initio calculations.
Abstract: We demonstrate an approach to the development of many-body interatomic potentials for monoatomic metals with improved accuracy and reliability. The functional form of the potentials is that of the embedded-atom method, but the interesting features are as follows: (1) The database used for the development of a potential includes both experimental data and a large set of energies of different alternative crystalline structures of the material generated by ab initio calculations. We introduce a rescaling of interatomic distances in an attempt to improve the compatibility between experimental and ab initio data. (2) The optimum parametrization of the potential for the given database is obtained by alternating the fitting and testing steps. The testing step includes a comparison between the ab initio structural energies and those predicted by the potential. This strategy allows us to achieve the best accuracy of fitting within the intrinsic limitations of the potential model. Using this approach we develop reliable interatomic potentials for Al and Ni. The potentials accurately reproduce basic equilibrium properties of these metals, the elastic constants, the phonon-dispersion curves, the vacancy formation and migration energies, the stacking fault energies, and the surface energies. They also predict the right relative stability of different alternative structures with coordination numbers ranging from 12 to 4. The potentials are expected to be easily transferable to different local environments encountered in atomistic simulations of lattice defects.

1,269 citations


Journal ArticleDOI
TL;DR: The application of discrete-event simulation modeling to health care clinics and systems of clinics (for example, hospitals, outpatient clinics, emergency departments, and pharmacies) and future directions of research and applications are discussed.
Abstract: In recent decades, health care costs have dramatically increased, while health care organisations have been under severe pressure to provide improved quality health care for their patients. Several health care administrators have used discrete-event simulation as an effective tool for allocating scarce resources to improve patient flow, while minimising health care delivery costs and increasing patient satisfaction. The rapid growth in simulation software technology has created numerous new application opportunities, including more sophisticated implementations, as well as combining optimisation and simulation for complex integrated facilities. This paper surveys the application of discrete-event simulation modeling to health care clinics and systems of clinics (for example, hospitals, outpatient clinics, emergency departments, and pharmacies). Future directions of research and applications are also discussed.

891 citations


Journal ArticleDOI
02 Sep 1999-Nature
TL;DR: In this article, a new family of stable endohedral fullerenes encapsulating trimetallic nitride clusters, ErxSc3-xN@C80 (x = 0-3), was synthesized.
Abstract: The idea1 that fullerenes might be able to encapsulate atoms and molecules has been verified by the successful synthesis of a range of endohedral fullerenes, in which metallic or non-metallic species are trapped inside the carbon cage2,3,4,5,6,7,8,9,10,11,12,13. Metal-containing endohedral fullerenes have attracted particular interest as they might exhibit unusual material properties associated with charge transfer from the metal to the carbon shell. However, current synthesis methods have typical yields of less than 0.5%, and produce multiple endohedral fullerene isomers, which makes it difficult to perform detailed studies of their properties. Here we show that the introduction of small amounts of nitrogen into an electric-arc reactor allows for the efficient production of a new family of stable endohedral fullerenes encapsulating trimetallic nitride clusters, ErxSc3-xN@C80 (x = 0–3). This ‘trimetallic nitride template’ process generates milligram quantities of product containing 3–5% Sc3N@C80, which allows us to isolate the material and determine its crystal structure, and its optical and electronic properties. We find that the Sc3N moiety is encapsulated in a highly symmetric, icosahedral C80 cage, which is stabilized as a result of charge transfer between the nitride cluster and the fullerene cage. We expect that our method will provide access to a range of small-bandgap fullerene materials, whose electronic properties can be tuned by encapsulating nitride clusters containing different metals and metal mixtures.

836 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examine the effect of the nature of information and the type of reaction of analysts to new information and conclude that underreaction is inconsistent with rationality and optimism is consistent with systematic optimism in response to information.
Abstract: A rational analysis of analyst behavior predicts that analysts immediately and without bias incorporate information into their forecasts. Several studies document analysts' tendency to systematically underreact to information. Underreaction is inconsistent with rationality. Other studies indicate that analysts systematically overreact to new information or that they are systematically optimistic. This study discriminates between these three hypotheses by examining the interaction between the nature of information and the type of reaction by analysts. The evidence indicates that analysts underreact to negative information, but overreact to positive information. These results are consistent with systematic optimism in response to information. THE LITERATURE ON FINANCIAL ANALYSTS defines the phrase "forecast inefficiency" to mean forecasts that fail to accurately incorporate new information on a timely basis and/or that are biased. These forecasts have also been described as irrational or suboptimal. Prior studies report inefficiency in analysts' forecasts, finding that they are upwardly biased and inaccurately reflect available information. Some studies conclude from this that analysts underreact to information; other studies conclude that analysts overreact. If markets treat analysts' forecasts as both rational and statistically optimal, then inefficient forecasts could have important implications for the efficiency of pricing in securities markets. In this paper, we reexamine the apparent tendency of analysts to misinterpret earnings information. The intent of this study is to discriminate between three hypotheses: (1) that analysts systematically underreact to new earnings information; (2) that analysts systematically overreact to new earnings information; and (3) that analysts are systematically optimistic in their reactions. For hypotheses (1) and (2), the direction of the misinterpretation (i.e., underor overreaction) is independent of the nature of the information received. In contrast, hypothesis (3) predicts that analysts are optimistic in interpreting

817 citations


Journal ArticleDOI
01 Oct 1999
TL;DR: A meta-analysis of 63 studies with 112 effect sizes yielded an overall mean weighted effect size of 0.46, indicating that individuals in spaced practice conditions performed significantly higher than those in massed practice conditions.
Abstract: The present review examined the relationship between conditions of massed practice and spaced practice with respect to task performance. A meta-analysis of 63 studies with 112 effect sizes yielded an overall mean weighted effect size of 0.46, indicating that individuals in spaced practice conditions performed significantly higher than those in massed practice conditions. Subsequent analyses, however, suggested that the nature of the task- being practiced, the intertrial time interval, and the interaction between these two variables significantly moderated the relationship between practice conditions and performance. In addition,, significantly higher effect sizes were found in studies with low methodological rigor as compared with those studies higher in rigor. Directions for future research and applications of the findings are discussed.

586 citations


Journal ArticleDOI
TL;DR: In this paper, the importance of terrestrial detrital inputs to secondary productivity of a headwater stream was examined, and the authors used randomized intervention analysis (RIA) to test the null hypotheses that no change in abundance or biomass of functional feeding groups or specific taxa occurred in the treatment stream relative to the reference stream.
Abstract: We examined the importance of terrestrial detrital inputs to secondary productivity of a headwater stream. Following a year of pretreatment studies on two headwater streams, we excluded terrestrial litter inputs (=treatment) to one stream while using the other as a reference. We excluded litter for 3 yr followed by 1 yr of small woody debris (≤10 cm diameter) removal and litter exclusion. Monthly benthic samples were collected from dominant mixed substrate (cobble, pebble, and sand-silt) as well as from moss-covered bedrock outcrop substrates. We used randomized intervention analysis (RIA) to test the null hypotheses that no change in abundance or biomass of functional feeding groups or specific taxa occurred in the treatment stream relative to the reference stream. Benthic organic matter was significantly lower in mixed substrate habitats of the treatment stream; however, small woody debris did not show a significant reduction prior to manual removal during year 4. At the end of the treatment period, tot...

539 citations


Journal ArticleDOI
TL;DR: The results clearly demonstrate that the MSAP technique is highly efficient for large-scale detection of cytosine methylation in the rice genome and believe that the technique can be adapted for use in other plant species.
Abstract: DNA methylation is known to play an important role in the regulation of gene expression in eukaryotes. In this study, we assessed the extent and pattern of cytosine methylation in the rice genome, using the technique of methylation-sensitive amplified polymorphism (MSAP), which is a modification of the amplified fragment length polymorphism (AFLP) method that makes use of the differential sensitivity of a pair of isoschizomers to cytosine methylation. The tissues assayed included seedlings and flag leaves of an elite rice hybrid, Shanyou 63, and the parental lines Zhenshan 97 and Minghui 63. In all, 1076 fragments, each representing a recognition site cleaved by either or both of the isoschizomers, were amplified using 16 pairs of selective primers. A total of 195 sites were found to be methylated at cytosines in one or both parents, and the two parents showed approximately the same overall degree of methylation (16.3%), as revealed by the incidence of differential digestion by the isoschizomers. Four classes of patterns were identified in a comparative assay of cytosine methylation in the parents and hybrid; increased methylation was detected in the hybrid compared to the parents at some of the recognition sites, while decreased methylation in the hybrid was detected at other sites. A small proportion of the sites was found to be differentially methylated in seedlings and flag leaves; DNA from young seedlings was methylated to a greater extent than that from flag leaves. Almost all of the methylation patterns detected by MSAP could be confirmed by Southern analysis using the isolated amplified fragments as probes. The results clearly demonstrate that the MSAP technique is highly efficient for large-scale detection of cytosine methylation in the rice genome. We believe that the technique can be adapted for use in other plant species.

494 citations


Journal ArticleDOI
TL;DR: In this paper, the authors compared US international tourists' images of four Mediterranean destinations (Turkey, Egypt, Greece, and Italy) for both visitors and nonvisitors, and found that significant differences exist in all image components between the four destination countries.
Abstract: This study compares US international pleasure travelers’ images of four Mediterranean destinations—Turkey, Egypt, Greece, and Italy—for both visitors and nonvisitors The image construct was conceptualized as having three components: cognitive, affective, and overall image MANOVA analysis indicated that significant differences exist in all image components between the four destination countries The findings revealed strengths and weaknesses of the four competing destinations and implications for positioning in the US international pleasure market as well as product development and promotion strategy for the destinations

479 citations


Proceedings ArticleDOI
01 Jul 1999
TL;DR: This paper classifies and examines these paralleling schemes, focusing on the active current-sharing approaches, and finds that some new paralleled schemes can be achieved.
Abstract: There is a fairly large number of methods for paralleling power converters. This paper classifies and examines these paralleling schemes, focusing on the active current-sharing approaches. Based on this classification, some new paralleling schemes can be achieved. Emphasis is placed on discussion and assessment of merits and limitations of these schemes. Finally, the prominent features of the dominant paralleling schemes are verified by simulation of a two-paralleled buck converter system.

424 citations


Journal ArticleDOI
TL;DR: The average respiration rate of FPOM was 1.4 mg O2 g AFDM -1 day -1 over a temperature range of 6-22 ∞C, which implies a decomposition rate of 0.00104 day 1 as discussed by the authors.
Abstract: SUMMARY 6. The average respiration rate of FPOM was 1.4 mg O2 g AFDM -1 day -1 over a temperature range of 6-22 ∞C, which implies a decomposition rate of 0.00104 day -1 . Transport distances of both corn pollen and glass beads, surrogates of natural FPOM, were short (< 10 m) except during high discharge. 7. Estimates of transport rate were substantially larger than the breakdown rates for sticks, leaves and FPOM. Thus, an organic particle on the stream bottom is more likely to be transported than broken down by biological processes, although estimates of turnover length suggest that sticks and leaves do not travel far. However, once these larger particles are converted to refractory FPOM, either by physical or biological processes, they may be transported long distances before being metabolized.

Journal ArticleDOI
TL;DR: The hypothesis that the flavonoid enzymes assemble as a macromolecular complex with contacts between multiple proteins is supported, and evidence was found for posttranslational modification of CHI.
Abstract: Flavonoids are secondary metabolites derived from phenylalanine and acetate metabolism that perform a variety of essential functions in higher plants. Studies over the past 30 years have supported a model in which flavonoid metabolism is catalyzed by an enzyme complex localized to the endoplasmic reticulum [Hrazdina, G. & Wagner, G. J. (1985) Arch. Biochem. Biophys. 237, 88–100]. To test this model further we assayed for direct interactions between several key flavonoid biosynthetic enzymes in developing Arabidopsis seedlings. Two-hybrid assays indicated that chalcone synthase, chalcone isomerase (CHI), and dihydroflavonol 4-reductase interact in an orientation-dependent manner. Affinity chromatography and immunoprecipitation assays further demonstrated interactions between chalcone synthase, CHI, and flavonol 3-hydroxylase in lysates from Arabidopsis seedlings. These results support the hypothesis that the flavonoid enzymes assemble as a macromolecular complex with contacts between multiple proteins. Evidence was also found for posttranslational modification of CHI. The importance of understanding the subcellular organization of elaborate enzyme systems is discussed in the context of metabolic engineering.

Journal ArticleDOI
TL;DR: Microinjection of anti-COP-I antibodies or expression of a GTP-restricted Arf-1 mutant does not interfere with Golgi-to-ER transport of Shiga toxin/Shiga-like toxin-1 or with the apparent recycling to the ER of GolGi-resident glycosylation enzymes, indicating the existence of at least two distinct pathways for Golgi -to- ER transport, one COP-I dependent and the other COP- I independent.
Abstract: The cytosolic coat-protein complex COP-I interacts with cytoplasmic 'retrieval' signals present in membrane proteins that cycle between the endoplasmic reticulum (ER) and the Golgi complex, and is required for both anterograde and retrograde transport in the secretory pathway. Here we study the role of COP-I in Golgi-to-ER transport of several distinct marker molecules. Microinjection of anti-COP-I antibodies inhibits retrieval of the lectin-like molecule ERGIC-53 and of the KDEL receptor from the Golgi to the ER. Transport to the ER of protein toxins, which contain a sequence that is recognized by the KDEL receptor, is also inhibited. In contrast, microinjection of anti-COP-I antibodies or expression of a GTP-restricted Arf-1 mutant does not interfere with Golgi-to-ER transport of Shiga toxin/Shiga-like toxin-1 or with the apparent recycling to the ER of Golgi-resident glycosylation enzymes. Overexpression of a GDP-restricted mutant of Rab6 blocks transport to the ER of Shiga toxin/Shiga-like toxin-1 and glycosylation enzymes, but not of ERGIC-53, the KDEL receptor or KDEL-containing toxins. These data indicate the existence of at least two distinct pathways for Golgi-to-ER transport, one COP-I dependent and the other COP-I independent. The COP-I-independent pathway is specifically regulated by Rab6 and is used by Golgi glycosylation enzymes and Shiga toxin/Shiga-like toxin-1.

Journal ArticleDOI
TL;DR: In this paper, the authors explored conceptual, methodological, and empirical issues related to the development of a financial risk-tolerance assessment instrument and proposed a 13-item risk assessment instrument.

Journal ArticleDOI
TL;DR: In this article, a measure of satisfaction with leisure travel/tourism services that is related to life satisfaction is developed, which is based on the hierarchy of life satisfaction model, and a LISREL analysis was performed to test the goodness of fit of the model.

Journal ArticleDOI
TL;DR: Based on nationwide data the authors collected on whistle-blowers and on silent observers, this paper reported that whistle-bling is more frequent in the public sector than in the private sector.
Abstract: Based on nationwide data the authors collected on whistle-blowers and on silent observers, this article reports, that (a) whistle-blowing is more frequent in the public sector than in the private; ...


Journal ArticleDOI
David R. Notter1
TL;DR: A greater understanding of the potential that these alternative mechanisms have for supporting long-term genetic improvement and of genetic relationships among global livestock populations are priorities for managing farm animal genetic diversity.
Abstract: Farm animal genetic diversity is required to meet current production needs in various environments, to allow sustained genetic improvement, and to facilitate rapid adaptation to changing breeding objectives. Production efficiency in pastoral species is closely tied to the use of diverse genetic types, but greater genetic uniformity has evolved in intensively raised species. In poultry, breeding decisions are directed by a few multinational companies and involve intense selection, the use of distinct production lines, and very large populations. In dairy cattle, the Holstein breed dominates production. Intensive sire selection is leading to relatively rapid inbreeding rates and raises questions about long-term effects of genetic drift. Key questions in management of farm animal genetic diversity involve the distribution of potentially useful quantitative trait locus alleles among global livestock breeds. Experiments with tomato, maize, and mice suggest that favorable alleles can exist in otherwise lowly productive stocks; this cryptic variation may potentially contribute to future selection response. Genetic improvement under relatively intense unidirectional selection may involve both increases in the frequency of favorable additive alleles as well as the progressive breakdown of homeostatic regulatory mechanisms established under the stabilizing selection that is characteristic of natural populations. Recombination among closely linked regulatory loci and new, potentially favorable mutations are possible sources of long-term genetic variation. A greater understanding of the potential that these alternative mechanisms have for supporting long-term genetic improvement and of genetic relationships among global livestock populations are priorities for managing farm animal genetic diversity.

Journal ArticleDOI
Malcolm Potts1
TL;DR: Drying of cells leads to damage resulting from crowding of cytoplasmic components, condensation of the nucleoid, increases in the Tm of membrane phase transitions, and imposition of stress upon cell walls, which restricts many organisms to aqueous environments, some, including many cyanobacteria, can tolerate the air-dried state for prolonged periods.
Abstract: Drying of cells leads to damage resulting from crowding of cytoplasmic components, condensation of the nucleoid, increases in the Tm of membrane phase transitions, and imposition of stress upon cell walls. Prolonged desiccation leads to oxidation of proteins, DNA and membrane components through metal-dependent Fenton reactions, while Maillard reactions generate cross-linked products between the carbonyl groups of reducing sugars and the primary amines of nucleic acids and proteins. Although such damage restricts many organisms to aqueous environments, some, including many cyanobacteria, can tolerate the air-dried state for prolonged periods. Cyanobacteria in the Tintenstrich communities of exposed rock faces, Microcoleus and Lyngbya spp. in intertidal mats, chasmoendolithic Chroococcidiopsis spp. in the rocks of hot and cold deserts, and terrestrial epilithic crusts of Tolypothrix and Nostoc are examples that show a marked capacity to withstand the removal of their cellular water. For Nostoc commune, the ...

Journal ArticleDOI
TL;DR: The joint TOA/AOA, the marginal TOA, and the marginal AOA probability density functions (PDFs) are derived for the elliptical and circular scattering models to provide insight into the properties of the spatial wireless channel.
Abstract: With the introduction of antenna array systems into wireless communication networks comes the need to better understand the spatial characteristics of the channel. Scattering models provide both angle of arrival (AOA) and time of arrival (TOA) statistics of the channel. A number of different scattering models have been proposed in the literature including elliptical and circular models. These models assume that scatterers lie within an elliptical and circular region in space, respectively. In this paper, the joint TOA/AOA, the marginal TOA, and the marginal AOA probability density functions (PDFs) are derived for the elliptical and circular scattering models. These PDFs provide insight into the properties of the spatial wireless channel.

Journal ArticleDOI
TL;DR: The structures of over 350 taxane diterpenoids are classified and presented with information on their plant source, yield, melting point, and optical activity.
Abstract: The structures of over 350 taxane diterpenoids are classified and presented with information on their plant source, yield, melting point, and optical activity. The biotransformations and biosynthesis of the taxoids are also reviewed.

Journal ArticleDOI
TL;DR: It is demonstrated that antibiotic resistance profiles in fecal streptococci can be used to reliably determine sources of fecal pollution, and water quality improvements can occur when efforts to address the identified sources are made.
Abstract: Nonpoint sources of pollution that contribute fecal bacteria to surface waters have proven difficult to identify. Knowledge of pollution sources could aid in restoration of the water quality, reduce the amounts of nutrients leaving watersheds, and reduce the danger of infectious disease resulting from exposure to contaminated waters. Patterns of antibiotic resistance in fecal streptococci were analyzed by discriminant and cluster analysis and used to identify sources of fecal pollution in a rural Virginia watershed. A database consisting of patterns from 7,058 fecal streptococcus isolates was first established from known human, livestock, and wildlife sources in Montgomery County, Va. Correct fecal streptococcus source identification averaged 87% for the entire database and ranged from 84% for deer isolates to 93% for human isolates. To field test the method and the database, a watershed improvement project (Page Brook) in Clarke County, Va., was initiated in 1996. Comparison of 892 known-source isolates from that watershed against the database resulted in an average correct classification rate of 88%. Combining all animal isolates increased correct classification rates to > or = 95% for separations between animal and human sources. Stream samples from three collection sites were highly contaminated, and fecal streptococci from these sites were classified as being predominantly from cattle (>78% of isolates), with small proportions from waterfowl, deer, and unidentified sources ( approximately 7% each). Based on these results, cattle access to the stream was restricted by installation of fencing and in-pasture watering stations. Fecal coliforms were reduced at the three sites by an average of 94%, from prefencing average populations of 15,900 per 100 ml to postfencing average populations of 960 per 100 ml. After fencing, <45% of fecal streptococcus isolates were classified as being from cattle. These results demonstrate that antibiotic resistance profiles in fecal streptococci can be used to reliably determine sources of fecal pollution, and water quality improvements can occur when efforts to address the identified sources are made.

Journal ArticleDOI
TL;DR: A standard assumption when using a control chart to monitor a process is that the observations of output are independent, but for many processes the observations are autocorrelated.
Abstract: A standard assumption when using a control chart to monitor a process is that the observations of output are independent. However, for many processes the observations are autocorrelated. This can have a significant effect on the performance of the con..

Journal ArticleDOI
TL;DR: In this paper, it was shown that with increased time of sputtering, the calculated thickness of TiO 2 and its mole fraction in the oxide film decreases faster than that due solely to thinning of the outermost layer.

Journal ArticleDOI
TL;DR: A growing body of evidence indicates that phenylpropanoid and flavonoid metabolism is catalyzed, not by free-floating "soluble" enzymes, but via one or more membrane-associated multienzyme complexes as discussed by the authors.
Abstract: A growing body of evidence indicates that phenylpropanoid and flavonoid metabolism is catalyzed, not by free-floating ‘soluble’ enzymes, but via one or more membrane-associated multienzyme complexes. This type of macromolecular organization has important implications for the overall efficiency, specificity, and regulation of these pathways. Classical biochemical studies of phenylpropanoid and flavonoid metabolism have laid a solid foundation for this model, providing evidence of the channeling of intermediates between enzyme active sites and co-localization of enzymes in cell membranes. This work is now being extended using transgenic plants to determine how the partitioning of metabolites within these pathways is controlled, as well as applying sensitive methods to define specific interactions among the individual enzymes. Information from these studies promises to provide new insights into the structuring of biosynthetic pathways within cells, which should lead to more effective means for engineering the production of plant metabolites with nutritional and agronomic importance.

Journal ArticleDOI
TL;DR: The Parade Game as discussed by the authors simulates a construction process in which resources produced by one trade are prerequisite to work performed by the next trade and illustrates that throughput will be reduced, project completion delayed, and waste increased by variations in flow.
Abstract: The Parade Game illustrates the impact work flow variability has on the performance of construction trades and their successors. The game consists of simulating a construction process in which resources produced by one trade are prerequisite to work performed by the next trade. Production-level detail, describing resources being passed from one trade to the next, illustrates that throughput will be reduced, project completion delayed, and waste increased by variations in flow. The game shows that it is possible to reduce waste and shorten project duration by reducing the variability in work flow between trades. Basic production management concepts are thus applied to construction management. They highlight two shortcomings of using the critical-path method for field-level planning: The critical-path method makes modeling the dependence of ongoing activities between trades or with operations unwieldy and it does not explicitly represent variability. The Parade Game can be played in a classroom setting eith...

Proceedings ArticleDOI
20 Dec 1999
TL;DR: This paper presents a systematic approach, testbed evaluation, for the assessment of interaction techniques for VEs, and presents two testbed experiments, covering techniques for the common VE tasks of travel and object selection/manipulation.
Abstract: As immersive virtual environment (VE) applications become more complex, it is clear that we need a firm understanding of the principles of VE interaction. In particular, designers need guidance in choosing three-dimensional interaction techniques. In this paper, we present a systematic approach, testbed evaluation, for the assessment of interaction techniques for VEs. Testbed evaluation uses formal frameworks and formal experiments with multiple independent and dependent variables in order to obtain a wide range of performance data for VE interaction techniques. We present two testbed experiments, covering techniques for the common VE tasks of travel and object selection/manipulation. The results of these experiments allow us to form general guidelines for VE interaction, and to provide an empirical basis for choosing interaction techniques in VE applications. This has been shown to produce measurable usability gains in a real-world VE application.

Journal ArticleDOI
TL;DR: This article presents a critique of conventional collaboration transparency systems, which provide the real-time shared use of legacy single-user applications, and presents an alternative approach to implementing collaboration transparency that provides many features previously seen only in collaboration-aware applicaitons.
Abstract: This article presents a critique of conventional collaboration transparency systems, also called “application-sharing” systems, which provide the real-time shared use of legacy single-user applications. We find that conventional collaboration transparency systems are inefficient in their use of network resources and lack support for key groupware principles: concurrent work, relaxed WYSIWIS, and group awareness. Next, we present an alternative approach to implementing collaboration transparency that provides many features previously seen only in collaboration-aware applicaitons. Our approach is based on a replicated architecture where selected single-user interface components are dynamically replaced by multiuser versions. The replacement occurs at run-time and is transparent to the single-user application and its developers.. As an instance of this approach, we describe its incorporation into a Java-based collaboration transparency system for serializable, Swing-based Java applications, called Flexible JAMM (Java Applets Made Multiuser). To validate that the flexible collaboration transparency system is truly an improvement over conventional systems, we conducted an empirical study of collaborators performing both tightly and loosely coupled tasks using Flexible JAMM versus a representative conventional collaboration transparency system, Microsoft NetMeeting. Completion times were significantly faster in the loosely coupled task using Flexible JAMM and were not adversely affected in the tightly coupled task. Accuracy was equivalent for both systems. Participants greatly preferred Flexible JAMM.

Journal ArticleDOI
TL;DR: In this article, a new structural health monitoring technique capable of in-service, on-line incipient damage detection has been proposed by the Center for Intelligent Material Systems and Structures, physical changes in a structure cause changes in the mechanical impedance.
Abstract: A new structural health monitoring technique capable of in-service, on-line incipient damage detection has been proposed by the Center for Intelligent Material Systems and Structures, Physical changes in a structure cause changes in the mechanical impedance. Due to the electromechanical coupling in piezoelectric materials, this change causes a change in the electrical impedance of the piezoelectric sensor. Hence, by monitoring the electrical impedance and comparing this to a baseline measurement, we can determine when structural damage has either occurred or is imminent. However, in almost all practical health monitoring applications, the structure being monitored is constantly undergoing change due to the effect of external boundary conditions. One of the important factors that leads to this change is the temperature variations. In this paper, temperature effects on the electrical impedance of piezoelectric materials and the structures have been investigated. A computer algorithm was developed which incorporates temperature compensation into our health monitoring applications. Three experimental investigations were performed successfully under the temperature varying condition, in the range of 25 to 75°C, including a bolted pipe structure, composite reinforced aluminum and precision part such as gears. It was found that, by this compensation procedure, the impedance based health monitoring tehcnique is able to detect damage in the incipient stage, even with the presence of significant temperature variation.

Journal ArticleDOI
Raymond H. Myers1
TL;DR: This paper is a reflection on where response surface methodology is at this point and what will likely be future directions.
Abstract: This paper is a reflection on where response surface methodology (RSM) is at this point and what will likely be future directions The emphasis in the last two decades on robust parameter design has brought attention to RSM as an alternative methodology