Showing papers by "Georgia Institute of Technology published in 1996"
TL;DR: A theory is proposed that increased age in adulthood is associated with a decrease in the speed with which many processing operations can be executed and that this reduction in speed leads to impairments in cognitive functioning because of what are termed the limited time mechanism and the simultaneity mechanism.
Abstract: A theory is proposed to account for some of the age-related differences reported in measures of Type A or fluid cognition. The central hypothesis in the theory is that increased age in adulthood is associated with a decrease in the speed with which many processing operations can be executed and that this reduction in speed leads to impairments in cognitive functioning because of what are termed the limited time mechanism and the simultaneity mechanism. That is, cognitive performance is degraded when processing is slow because relevant operations cannot be successfully executed (limited time) and because the products of early processing may no longer be available when later processing is complete (simultaneity). Several types of evidence, such as the discovery of considerable shared age-related variance across various measures of speed and large attenuation of the age-related influences on cognitive measures after statistical control of measures of speed, are consistent with this theory.
5,094 citations
TL;DR: Tetrahedral, cubic, irregular-prismatic, icosahedral, and cubo-octahedral particle shapes were observed, whose distribution was dependent on the concentration ratio of the capping polymer material to the platinum cation.
Abstract: The shapes and sizes of platinum nanoparticles were controlled by changes in the ratio of the concentration of the capping polymer material to the concentration of the platinum cations used in the reductive synthesis of colloidal particles in solution at room temperature. Tetrahedral, cubic, irregular-prismatic, icosahedral, and cubo-octahedral particle shapes were observed, whose distribution was dependent on the concentration ratio of the capping polymer material to the platinum cation. Controlling the shape of platinum nanoparticles is potentially important in the field of catalysis.
2,305 citations
TL;DR: In this article, a multidimensional measure for Leader-Member Exchange (LMX) was developed and validated through item analysis and criterion-related validation using 249 employees representing two organizations.
Abstract: Whether Leader-Member Exchange (LMX) is a unidimensional or a multidimensional construct was assessed through the development and validation of a multidimensional measure. Item analysis involving 302 working students, followed by construct and criterion-related validation using 249 employees representing two organizations resulted in a multidimensional LMX scale. The results provided support for the affect, loyalty, and contribution dimensions identified by Dienesch and Liden (1986), as well as a fourth dimension, professional respect.
1,834 citations
24 Mar 1996
TL;DR: This work considers the problem of efficiently generating graph models that accurately reflect the topological properties of real internetworks, and proposes efficient methods for generating topologies with particular properties, including a transit-stub model that correlates well with the internet structure.
Abstract: Graphs are commonly used to model the structure of internetworks, for the study of problems ranging from routing to resource reservation. A variety of graph models are found in the literature, including regular topologies such as rings or stars, "well-known" topologies such as the original ARPAnet, and randomly generated topologies. Less common is any discussion of how closely these models correlate with real network topologies. We consider the problem of efficiently generating graph models that accurately reflect the topological properties of real internetworks. We compare the properties of graphs generated using various methods with those of real internets. We also propose efficient methods for generating topologies with particular properties, including a transit-stub model that correlates well with the internet structure. Improved models for the internetwork structure have the potential to impact the significance of simulation studies of internetworking solutions, providing a basis for the validity of the conclusions.
1,764 citations
TL;DR: In this article, the authors investigate job seekers' and new employees' subjective person-organization (P-O) fit perceptions and find that P-O fit perceptions predict both job choice intentions and work attitudes, even after controlling for the attractiveness of job attributes.
1,574 citations
TL;DR: In this paper, the authors review the literature addressing coordinated planning between two or more stages of the supply chain, placing particular emphasis on models that would lend themselves to a total supply chain model.
1,319 citations
TL;DR: In this article, a series of gold nanocrystals, passivated by self-assembled monolayers (SAMs) of straight-chain alkylthiolate molecules (RS, R) are described.
Abstract: The creation of perfect nanometer-scale crystallites (nanocrystals), identically replicated in unlimited quantities, in a state that can be manipulated and understood as pure macromolecular substances, is an ultimate challenge of modern materials research with outstanding fundamental and potential technological consequences.[’l We report on the prediction, isolation, and characterization of a series of gold nanocrystals, passivated by self-assembled monolayers (SAMs) of straight-chain alkylthiolate molecules (RS, R
1,097 citations
TL;DR: In this paper, the existence and uniqueness of optimal maps are discussed. But the uniqueness of the optimal map is not discussed. And the role of the map in finding the optimal solution is left open.
Abstract: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 1. Summary of main results . . . . . . . . . . . . . . . . . . . . . . . . 120 2. Background on optimal measures . . . . . . . . . . . . . . . . . . . 126 Part I. Strictly convex costs . . . . . . . . . . . . . . . . . . . . . . . . . . 133 3. Existence and uniqueness of optimal maps . . . . . . . . . . . . . 133 4. Characterization of the optimal map . . . . . . . . . . . . . . . . . 137 Part II. Costs which are strictly concave as a function of d i s t a n c e . . . 141 5. The role of optimal maps . . . . . . . . . . . . . . . . . . . . . . . . 141 6. Uniqueness of optimal solutions . . . . . . . . . . . . . . . . . . . . 144 Part III. Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 A. Legendre transforms and conjugate costs . . . . . . . . . . . . . . 148 B. Examples of c-concave potentials . . . . . . . . . . . . . . . . . . . 152 C. Regularity of c-concave potentials . . . . . . . . . . . . . . . . . . 154 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
939 citations
TL;DR: Fluids near their critical point have dissolving power comparable to that of liquids, are much more compressible than dilute gases, and have transport properties intermediate between gas-and liquid-like as discussed by the authors.
Abstract: Fluids near their critical point have dissolving power comparable to that of liquids, are much more compressible than dilute gases, and have transport properties intermediate between gas-and liquid-like. This unusual combination of physical properties can be advantageously exploited in environmentally benign separation and reaction processes, as well as for new kinds of materials processing.
804 citations
TL;DR: In this paper, the authors used the bending mode (ν2) of CO2 to probe polymer−CO2 interactions and observed the splitting of the band corresponding to the CO2 ν2 mode.
Abstract: Fourier transform IR spectroscopy has been used to investigate the interaction of carbon dioxide with polymers. IR transmission and attenuated total reflectance spectra were obtained for CO2 impregnated into polymer films. It has been shown that the polymers possessing electron-donating functional groups (e.g., carbonyl groups) exhibit specific interactions with CO2, most probably of Lewis acid−base nature. An unusual aspect is the use of the bending mode (ν2) of CO2 to probe polymer−CO2 interactions. The evidence of the interaction is the observation of the splitting of the band corresponding to the CO2 ν2 mode. This splitting indicates that the double degeneracy of the ν2 mode is removed due to the interaction of electron lone pairs of the carbonyl oxygen with the carbon atom of the CO2 molecule. This splitting has not been observed for polymers lacking electron-donating functional groups (e.g., poly(ethylene)). In contrast, the ν3 mode shows little if any sensitivity to this interaction, which is in ac...
803 citations
TL;DR: In this article, the authors used a sample of 62 U.S. new venture manufacturers in the computer and communications equipment industries during the late 1980s and found that higher levels of internationalization (percentage of foreign sales to total venture sales) were associated with higher relative market share two years later.
TL;DR: In this paper, the authors proposed a mobility tracking mechanism that combines a movement-based location update policy with a selective paging scheme, where each mobile terminal only keeps a counter of the number of cells visited and a location update is performed when this counter exceeds a predefined threshold value.
Abstract: This paper introduces a mobility tracking mechanism that combines a movement-based location update policy with a selective paging scheme. Movement-based location update is selected for its simplicity. It does not require each mobile terminal to store information about the arrangement and the distance relationship of all cells. In fact, each mobile terminal only keeps a counter of the number of cells visited. A location update is performed when this counter exceeds a predefined threshold value. This scheme allows the dynamic selection of the movement threshold on a per-user basis. This is desirable as different users may have very different mobility patterns. Selective paging reduces the cost for locating a mobile terminal in the expense of an increase in the paging delay. We propose a selective paging scheme which significantly decreases the location tracking cost under a small increase in the allowable paging delay. We introduce an analytical model for the proposed location tracking mechanism which captures the mobility and the incoming call arrival patterns of each mobile terminal. Analytical results are provided to demonstrate the cost-effectiveness of the proposed scheme under various parameters.
TL;DR: The pulsatile hemodynamics of the left coronary artery bifurcation was numerically simulated using the spectral element method for realistic in vivo anatomic and physiologic conditions and found the velocity profiles were found to be skewed.
Abstract: The localization of atherosclerosis in the coronary arteries may be governed by local hemodynamic features. In this study, the pulsatile hemodynamics of the left coronary artery bifurcation was numerically simulated using the spectral element method for realistic in vivo anatomic and physiologic conditions. The velocity profiles were found to be skewed in both the left anterior descending and the circumflex coronary arteries. Velocity skewing arose from the bifurcation as well as from the curvature of the artery over the myocardial surface. Arterial wall shear stress was significantly lower in the bifurcation region, including the side walls. The greatest oscillatory behavior was localized to the outer wall of the circumflex artery. The time-averaged mean wall shear stress varied from about 3 to 98 dynes/cm 2 in the left coronary artery system. The highly localized distribution of low and oscillatory shear stress along the walls strongly correlates with the focal locations of atheroma in the human left coronary artery.
15 Apr 1996
TL;DR: Some of the issues that practitioners face when using a goal-based approach to specify the requirements for a system are illustrated and some of the needs for needed future research are discussed.
Abstract: Goals are a logical mechanism for identifying, organizing and justifying software requirements. Strategies are needed for the initial identification and construction of goals. We discuss goals from the perspective of two themes: goal analysis and goal evolution. We begin with an overview of the goal-based method we have developed and summarize our experiences in applying our method to a relatively large example. We illustrate some of the issues that practitioners face when using a goal-based approach to specify the requirements for a system and close the paper with a discussion of needed future research on goal-based requirements analysis and evolution.
TL;DR: In this paper, the potential effects of attrition in longitudinal research are addressed and a procedure for assessing its effects is recommended, using data collected from a random sample of employed adults in the US regarding job satisfaction, job characteristics, demographics and mood.
Proceedings Article•
03 Dec 1996TL;DR: In an implementation of pole balancing on a complex anthropomorphic robot arm, it is demonstrated that, when facing the complexities of real signal processing, model-based reinforcement learning offers the most robustness for LQR problems.
Abstract: By now it is widely accepted that learning a task from scratch, i.e., without any prior knowledge, is a daunting undertaking. Humans, however, rarely attempt to learn from scratch. They extract initial biases as well as strategies how to approach a learning problem from instructions and/or demonstrations of other humans. For teaming control, this paper investigates how learning from demonstration can be applied in the context of reinforcement learning. We consider priming the Q-function, the value function, the policy, and the model of the task dynamics as possible areas where demonstrations can speed up learning. In general nonlinear learning problems, only model-based reinforcement learning shows significant speed-up after a demonstration, while in the special case of linear quadratic regulator (LQR) problems, all methods profit from the demonstration. In an implementation of pole balancing on a complex anthropomorphic robot arm, we demonstrate that, when facing the complexities of real signal processing, model-based reinforcement learning offers the most robustness for LQR problems. Using the suggested methods, the robot learns pole balancing in just a single trial after a 30 second long demonstration of the human instructor.
TL;DR: The data suggest that both speed and working memory are fundamental to explaining age-related changes in cognitive aging but that the relative contributions of these constructs vary as a function of the type of memory task.
Abstract: An individual-differences approach was used to examine the component processes that predict episodic long-term memory performance A total of 301 participants ages 20-90 received a 7-hr cognitive battery across 3 days Key constructs hypothesized to affect long-term memory function were assessed, including multiple measures of working memory and perceptual speed Latent-construct, structural equation modeling was used to examine the relationship of these measures and age to different types of long-term memory tasks Speed was a key construct for all 3 types of memory tasks, mediating substantial age-related variance; working memory was a fundamental construct for free and cued recall but not spatial memory The data suggest that both speed and working memory are fundamental to explaining age-related changes in cognitive aging but that the relative contributions of these constructs vary as a function of the type of memory task
TL;DR: This variation embodies the integration of the Response Surface Methodology (RSM) with the compromise Decision Support Problem (DSP) and is especially useful for design problems where there are no closed-form solutions and system performance is computationally expensive to evaluate.
Abstract: In this paper, we introduce a small variation to current approaches broadly called Taguchi Robust Design Methods. In these methods, there are two broad categories of problems associated with simultaneously minimizing performance variations and bringing the mean on target, namely, Type 1-minimizing variations in performance caused by variations in noise factors (uncontrollable parameters). Type II-minimizing variations in performance caused by variations in control factors (design variables). In this paper, we introduce a variation to the existing approaches to solve both types of problems. This variation embodies the integration of the Response Surface Methodology (RSM) with the compromise Decision Support Problem (DSP). Our approach is especially useful for design problems where there are no closed-form solutions and system performance is computationally expensive to evaluate. The design of a solar powered irrigation system is used as an example.
TL;DR: In this paper, the authors propose that hybrid organizational forms provide a way to overcome the agency problems of adverse selection and moral hazard in selecting, assimilating, and monitoring new managers.
Abstract: This study proposes that hybrid organizational forms provide a way to overcome the agency problems of adverse selection and moral hazard in selecting, assimilating, and monitoring new managers. Con...
TL;DR: It is demonstrated that shear stress can increase NO production in the absence of increased [Ca2+]i, and it is suggested that phosphorylation of ecNOS may importantly modulate its activity during the imposition of increased shear Stress.
Abstract: Endothelial cells release nitric oxide (NO) more potently in response to increased shear stress than to agonists which elevate intracellular free calcium concentration ([Ca2+]i). To determine mechanistic differences in the regulation of endothelial constitutive NO synthase (ecNOS), we measured NO production by bovine aortic endothelial cells exposed to shear stress in a laminar flow chamber or treated with Ca2+ ionophores in static culture. The kinetics of cumulative NO production varied strikingly: shear stress (25 dyne/cm2) stimulated a biphasic increase over control that was 13-fold at 60 minutes, whereas raising [Ca2+]i caused a monophasic 6-fold increase. We hypothesized that activation of a protein kinase cascade mediates the early phase of flow-dependent NO production. Immunoprecipitation of ecNOS showed a 210% increase in phosphorylation 1 minute after flow initiation, whereas there was no significant increase after Ca2+ ionophore treatment. Although ecNOS was not tyrosine-phosphorylated, the early phase of flow-dependent NO production was blocked by genistein, an inhibitor of tyrosine kinases. To determine the Ca2+ requirement for flow-dependent NO production, we measured [Ca2+]i with a novel flow-step protocol. [Ca2+]i increased with the onset of shear stress, but not after a step increase. However, the step increase in shear stress was associated with a potent biphasic increase in NO production rate and ecNOS phosphorylation. These studies demonstrate that shear stress can increase NO production in the absence of increased [Ca2+]i, and they suggest that phosphorylation of ecNOS may importantly modulate its activity during the imposition of increased shear stress.
TL;DR: MITOMAP uses the mtDNA sequence as the unifying element for bringing together information on mitochondrial genome structure and function, pathogenic mutations and their clinical characteristics, population associated variation, and gene- gene interactions.
Abstract: We have developed a comprehensive database (MITOMAP) for the human mitochondrial DNA (mtDNA), the first component of the human genome to be completely sequenced [Anderson et al. (1981) Nature 290, 457-465]. MITOMAP uses the mtDNA sequence as the unifying element for bringing together information on mitochondrial genome structure and function, pathogenic mutations and their clinical characteristics, population associated variation, and gene- gene interactions. As increasingly larger regions of the human genome are sequenced and characterized, the need for integrating such information will grow. Consequently, MITOMAP not only provides a valuable reference for the mitochondrial biologist, it may also provide a model for the development of information storage and retrieval systems for other components of the human genome.
TL;DR: In this paper, it was shown that it is the overproduction of Sup35 protein, and not the excess of SUP35 DNA or mRNA, that causes the appearance of non-Mendelian factors.
Abstract: We have previously shown that multicopy plasmids containing the complete SUP35 gene are able to induce the appearance of the non-Mendelian factor [ PSI ]. This result was later interpreted by others as a crucial piece of evidence for a model postulating that [ PSI ] is a self-modified, prion-like conformational derivative of the Sup35 protein. Here we support this interpretation by proving that it is the overproduction of Sup35 protein, and not the excess of SUP35 DNA or mRNA that causes the appearance of [ PSI ]. We also show that the “prion-inducing domain” of Sup35p is in the N-terminal region, which, like the “prion-inducing domain” of another yeast prion, Ure2p, was previously shown to be distinct from the functional domain of the protein. This suggests that such a chimeric organization may be a common pattern of some prion elements. Finally, we find that [ PSI ] factors of different efficiencies and different mitotic stabilities are induced in the same yeast strain by overproduction of the identical Sup35 protein. We suggest that the different [ PSI ]-containing derivatives are analogous to the mysterious mammalian prion strains and result from different conformational variants of Sup35p.
TL;DR: In this paper, the authors present a review of methodological issues hampering the growth of cross-cultural marketing research and organize these issues around a six-step framework which includes elements such as problem definition, the development of an approach and research design formulation.
Abstract: Notes that methodological problems are hampering the growth of cross‐cultural marketing research and presents a review of methodological issues to address these problems. Organizes these issues around a six‐step framework which includes elements such as problem definition, the development of an approach and research design formulation. Notes that the marketing research problem can be defined by comparing the phenomenon or behaviour in separate cultural contexts and eliminating the influence of the self‐reference criterion. Discusses issues in data analysis such as treatment of outliers and standardization of data. Concludes with an interpretation of results and report presentation.
TL;DR: It is shown that a current-biased series array of nonidentical Josephson junctions undergoes two transitions as a function of the spread of natural frequencies, and the system can be mapped onto an exactly solvable model introduced by Kuramoto and the transition points can be accurately predicted.
Abstract: We show that a current-biased series array of nonidentical Josephson junctions undergoes two transitions as a function of the spread of natural frequencies. One transition corresponds to the onset of partial synchronization, and the other corresponds to complete phase locking. In the limit of weak coupling and disorder, the system can be mapped onto an exactly solvable model introduced by Kuramoto and the transition points can be accurately predicted.
TL;DR: Nanotube cavities should be less chemically reactive than graphite and may serve as nanosize test tubes, and have been illustrated by monitoring the decomposition of silver nitrate within nanotubes in situ in an electron microscope, which produced chains of silver nanobeads separated by high-pressure gas pockets.
Abstract: Open carbon nanotubes were filled with molten silver nitrate by capillary forces. Only those tubes with inner diameters of 4 nanometers or more were filled, suggesting a capillarity size dependence as a result of the lowering of the nanotube-salt interface energy with increasing curvature of the nanotube walls. Nanotube cavities should also be less chemically reactive than graphite and may serve as nanosize test tubes. This property has been illustrated by monitoring the decomposition of silver nitrate within nanotubes in situ in an electron microscope, which produced chains of silver nanobeads separated by high-pressure gas pockets.
TL;DR: In this article, the authors extend the conceptual work of Anderson and Oliver (1987) and Jaworski (1988) on control in three ways: first, they account for the independent effects of the reinforcement dimension of the game.
Abstract: The authors extend the conceptual work of Anderson and Oliver (1987) and Jaworski (1988) on control in three ways. First, they account for the independent effects of the reinforcement dimension of ...
TL;DR: In this paper, the authors explore design principles for next-generation optical wide-area networks, employing wavelength-division multiplexing (WDM) and targeted to nationwide coverage, and formulate the virtual topology design problem as an optimization problem with one of two possible objective functions: (1) for a given traffic matrix, minimize the networkwide average packet delay (corresponding to a solution for present traffic demands), or (2) maximize the scale factor by which the traffic matrix can be scaled up (to provide the maximum capacity upgrade for future traffic demands).
Abstract: We explore design principles for next-generation optical wide-area networks, employing wavelength-division multiplexing (WDM) and targeted to nationwide coverage. This optical network exploits wavelength multiplexers and optical switches in routing nodes, so that an arbitrary virtual topology may be embedded on a given physical fiber network. The virtual topology, which is used as a packet-switched network and which consists of a set of all-optical "lightpaths", is set up to exploit the relative strengths of both optics and electronics-viz. packets of information are carried by the virtual topology "as far as possible" in the optical domain, but packet forwarding from lightpath to lightpath is performed via electronic switching, whenever required. We formulate the virtual topology design problem as an optimization problem with one of two possible objective functions: (1) for a given traffic matrix, minimize the network-wide average packet delay (corresponding to a solution for present traffic demands), or (2) maximize the scale factor by which the traffic matrix can be scaled up (to provide the maximum capacity upgrade for future traffic demands). Since simpler versions of this problem have been shown to be NP-hard, we resort to heuristic approaches. Specifically, we employ an iterative approach which combines "simulated annealing" (to search for a good virtual topology) and "flow deviation" (to optimally route the traffic-and possibly bifurcate its components-on the virtual topology). We do not consider the number of available wavelengths to be a constraint, i.e., we ignore the routing of lightpaths and wavelength assignment for these lightpaths. We illustrate our approaches by employing experimental traffic statistics collected from NSFNET.
TL;DR: In this article, the limitations of linear constitutive modeling and limitations of this composition of PLZT as an actuator material are examined, and the "yield" or ferroelastic switching stress is suggested as a good criteria for assessing the capability of actuator ceramics.
TL;DR: This work considers a VoD system that uses multicast delivery to service multiple customers with a single set of resources and describes a framework and mechanisms by which such interactive functions can be incorporated into a multicasts delivery VoD System.
Abstract: In typical proposals for video-on-demand (VoD) systems, customers are serviced individually by allocating and dedicating a transmission channel and a set of server resources to each customer. This approach leads to an expensive to operate, nonscalable system. We consider a VoD system that uses multicast delivery to service multiple customers with a single set of resources. The use of multicast communication requires that part of the on-demand nature of the system be sacrificed to achieve scalability and cost-effectiveness. One drawback to using multicast communication is that it complicates the provision or interactive VCR-style functions. Interactivity can be provided by either increasing the complexity of the customer set-top box (STB) or by modifying the semantics of the interactive functions to make them easier to provide. We describe a framework and mechanisms by which such interactive functions can be incorporated into a multicast delivery VoD system. Through the use of simulation, we evaluate and compare the performance of a unicast VoD system and multicast VoD systems offering various levels of interactivity.
01 Nov 1996
TL;DR: The Cyberguide project is presented, in which prototypes of a mobile context-aware tour guide that provide information to a tourist based on knowledge of position and orientation are built.
Abstract: We present the Cyberguide project, in which we are building prototypes of a mobile context-aware tour guide that provide information t,o a tourist based on knowledge of position and orientation. We describe features of existing Cyberguide prototypes and discuss research issues that have emerged in our context-aware applications development in a mobile environment.