Showing papers by "Georgia Institute of Technology published in 1988"

Integer and Combinatorial Optimization

Abstract: FOUNDATIONS. The Scope of Integer and Combinatorial Optimization. Linear Programming. Graphs and Networks. Polyhedral Theory. Computational Complexity. Polynomial-Time Algorithms for Linear Programming. Integer Lattices. GENERAL INTEGER PROGRAMMING. The Theory of Valid Inequalities. Strong Valid Inequalities and Facets for Structured Integer Programs. Duality and Relaxation. General Algorithms. Special-Purpose Algorithms. Applications of Special- Purpose Algorithms. COMBINATORIAL OPTIMIZATION. Integral Polyhedra. Matching. Matroid and Submodular Function Optimization. References. Indexes.

Fractals Everywhere

Abstract: Focusing on how fractal geometry can be used to model real objects in the physical world, this up-to-date edition featurestwo 16-page full-color inserts, problems and tools emphasizing fractal applications, and an answers section. A bonus CD of an IFS Generator provides an excellent software tool for designing iterated function systems codes and fractal images.

Self-generated validity and other effects of measurement on belief, attitude, intention, and behavior.

Abstract: Drawing from recent developments in social cognition, cognitive psychology, and behavioral decision theory, we analyzed when and how the act of measuring beliefs, attitudes, intentions, and behaviors affects observed correlations among them. Belief, attitude, or intention can be created by measurement if the measured constructs do not already exist in long-term memory. The responses thus created can have directive effects on answers to other questions that follow in the survey. But even when counterparts to the beliefs, attitudes, and intentions measured already exist in memory, the structure of the survey researcher's questionnaire can affect observed correlations among them. The respondent may use retrieved answers to earlier survey questions as inputs to response generation to later questions. We present a simple theory predicting that an earlier response will be used as a basis for another, subsequent response if the former is accessible and if it is perceived to be more diagnostic than other accessible inputs. We outline the factors that determine both the perceived diagnosticity of a potential input, the likelihood that it will be retrieved, and the likelihood that some alternative (and potentially more diagnostic) inputs will be retrieved. This article examines the effects of measurement operations on revealed correlations among survey measures of belief, attitude, intention, and behavior. The potential reactivity of measurement has long been of concern in psychology. Methodologists (e.g., Campbell & Stanley, 1966; Cook & Campbell, 1979; Runkel & McGrath, 1972) warn of measurement-induced distortions relating to social desirability, evaluation apprehension, and sensitization to experimental treatments. Although it is true that the problem of reactivity of measurement affects work in both the social and physical sciences, in the physical sciences, measurement effects are expressed in terms of substantive theory. For instance, Heisenberg's uncertainty principle links basic

Physics at Surfaces

Abstract: Physics at Surfaces is a unique graduate-level introduction to the physics and chemical physics of solid surfaces, and atoms and molecules that interact with solid surfaces. A subject of keen scientific inquiry since the last century, surface physics emerged as an independent discipline only in the late 1960s as a result of the development of ultra-high vacuum technology and high speed digital computers. With these tools, reliable experimental measurements and theoretical calculations could at last be compared. Progress in the last decade has been truly striking. This volume provides a synthesis of the entire field of surface physics from the perspective of a modern condensed matter physicist with a healthy interest in chemical physics. The exposition intertwines experiment and theory whenever possible, although there is little detailed discussion of technique. This much-needed text will be invaluable to graduate students and researchers in condensed matter physics, physical chemistry and materials science working in, or taking graduate courses in, surface science.

Creativity syndrome: Integration, application, and innovation.

Abstract: Apres une definition du concept de creativite est effectuee une revue de la litterature consacree au developpement de l'innovation dans la reussite professionnelle, mettant l'accent sur l'integration et la reorganisation des structures cognitives

The role of biogenic hydrocarbons in urban photochemical smog: Atlanta as a case study.

Abstract: The effects of natural hydrocarbons must be considered in order to develop a reliable plan for reducing ozone in the urban atmosphere. Trees can emit significant quantities of hydrocarbons to metropolitan areas such as Atlanta, and model calculations indicate that these natural emissions can significantly affect urban ozone levels. By neglecting these compounds, previous investigators may have overestimated the effectiveness of an ozone abatement strategy based on reducing anthropogenic hydrocarbons.

The influence of organization structure on the utility of an entrepreneurial top management style

Abstract: This study examined the influence of organization structure on the relationship between top management's entrepreneurial orientation and financial performance. Moderated regression analysis was used to analyse data collected from 80 business organizations. the findings suggest that an entrepreneurial top management style has a positive effect on the performance of organically-structured firms and a negative effect on the performance of mechanistically-structured firms.

Observation of stochastic resonance in a ring laser.

Abstract: We report the first observation of stochastic resonance in an optical device, the bidirectional ring laser. The experiment exploits a new technique to modulate periodically the asymmetry between the two counter-rotating lasing modes. The measurements verify that the addition of injected noise can lead to an improved signal-to-noise ratio (relative to that observed with no externally injected noise).

Volatility persistence and stock valuations: Some empirical evidence using garch

Abstract: SUMMARY In this paper issues of volatility persistence and the changing risk premium in the stock market are investigated using the GARCH estimation technique. We get a point estimate of the index of relative risk aversion of 4.5 and confirm the existence of changing equity premiums in the US during 1962-1985. The persistence of shocks to the stock return volatility is so high that the data cannot reject a non-stationary volatility process specification. The results of this paper are consistent with Malkiel and Pindyck's hypothesis that it is the unforseen rise ini the investment uncertainty during 1974 that causes the market to plunge.

A singular perturbation approach to control of lightweight flexible manipulators

Abstract: The control of lightweight flexible manipulators is the focus of this work. Theflexible manipulator dynamics is derived on the basis of a Lagrangian-assumed modes method. The full-order flexible dynamic system does not allow the deter mination of a nonlinear feedback control as for rigid manipu lators, since there are not as many control inputs as output variables. This drawback is overcome by a model order reduction, based on a singular perturbation strategy, where the fast state variables are the elastic forces and their time derivatives.A composite control is adopted. First, a slow control is designed for the slow subsystem, which is shown to be the model of the equivalent rigid-link manipulator. Then a fast control is designed to stabilize the fast subsystem around the equilibrium trajectory set up by the slow subsystem under the effect of the slow control.The one-link flexible-arm prototype in the Flexible Auto mation Laboratory at Georgia Institute of Technology is chosen for developing a case study...

Kinematic analysis of a three degrees of freedom in-parallel actuated manipulator

Abstract: The dynamic analysis of a three-degrees-of-freedom in-parallel actuated manipulator is presented. The equations of motion have been formulated in joint-space using the Lagrangian approach. The analysis provides the solution to predict the forces required to actuate the links so that the manipulator follows a predetermined trajectory. A dynamic simulation program illustrates the influence of the link dynamics on the actuating force required. An example of tracing a helical path is chosen to illustrate the dynamic simulation and to show that the Cartesian position of the moving platform may be controlled at a sacrifice of orientation freedoms. The dynamic analysis provides a basis for future theoretical research to develop the control scheme, for experimental research to estimate the inertia parameters, and for design optimization of the prototype manipulator. >

Least-squares estimation of distribution functions in johnson's translation system

Abstract: To summarize a set of data by a distribution function in Johnson's translation system, we use a least-squares approach to parameter estimation wherein we seek to minimize the distance between the vector of "uniformized" oeder statistics and the corresponding vector of expected values. We use the software package FITTRI to apply this technique to three problems arising respectively in medicine, applied statistics, and civil engineering. Compared to traditional methods of distribution fitting based on moment matching, percentile matchingL 1 estimation, and L ⌆ estimation, the least-squares technique is seen to yield fits of similar accuracy and to converge more rapidly and reliably to a set of acceptable parametre estimates.

The application of a homogeneous half-space model in the analysis of endothelial cell micropipette measurements.

Abstract: Experimental studies have shown that endothelial cells which have been exposed to shear stress maintain a flattened and elongated shape after detachment. Their mechanical properties, which are studied using the micropipette experiments, are influenced by the level as well as the duration of the shear stress. In the present paper, we analyze these mechanical properties with the aid of two mathematical models suggested by the micropipette technique and by the geometry peculiar to these cells in their detached post-exposure state. The two models differ in their treatment of the contact zone between the cell and the micropipette. The main results are expressions for an effective Young's modulus for the cells, which are used in conjunction with the micropipette data to determine an effective Young's modulus for bovine endothelial cells, and to discuss the dependence of this modulus upon exposure to shear stress.

Photobioreactor design: Mixing, carbon utilization, and oxygen accumulation

Abstract: Photobioreactor design and operation are discussed in terms of mixing, carbon utilization, and the accumulation of photosynthetically produced oxygen. The open raceway pond is the primary type of reactor considered; however small diameter (1-5 cm) horizontal glass tubular reactors are compared to ponds in several respects. These are representative of the diversity in photobioreactor design: low capital cost, open systems and high capital cost, closed systems. Two 100-m(2) raceways were operated to provide input data and to validate analytical results. With a planktonic Chlorella sp., no significant difference in productivity was noted between one pond mixed at 30 cm/s and another mixed from 1 to 30 cm/s. Thus, power consumption or CO(2) outgassing limits maximal mixing velocities. Mixing power inputs measured in 100-m(2) ponds agreed fairly well with those calculated by the use of Manning's equation. A typically configured tubular reactor flowing full (1 cm diameter, 30 cm/s) consumes 10 times as much energy as a typical pond (20 cm deep flowing at 20 cm/s). Tubular reactors that flow only partially full would be limited by large hydraulic head losses to very short sections (as little as 2 m length at 30 cm/s flow) or very low flow velocities. Open ponds have greater CO(2) storage capacity than tubular reactors because of their greater culture volume per square meter (100-300 L/m(2) vs. 8-40 L/m(2) for 1-5-cm tubes). However, after recarbonation, open ponds tend to desorb CO(2) to the atmosphere. Thus ponds must be operated at higher pH and lower alkalinity than would be possible with tubular reactors if cost of carbon is a constraint. The mass transfer coefficient, K(L), for CO(2) release through the surface of a 100-m(2) pond was determined to be 0.10 m/h. Oxygen buildup would be a serious problem with any enclosed reactor, especially small-diameter tubes. At maximal rates of photosynthesis, a 1-cm tubular reactor would accumulate 8-10 mg O(2)/L/min. This may result in concentrations of oxygen reaching 100 mg/L, even with very frequent gas exchange. In an open pond, dissolved oxygen rises much more slowly as a consequence of the much greater volume per unit surface area and the outgassing of oxygen to the atmosphere. The maximum concentration of dissolved oxygen is typically 25-40 mg/L. The major advantage of enclosed reactors lies in the potential for aseptic operation, a product value which justifies the expense. For most products of algal mass cultivation, open ponds are the only feasible photobioreactor design capable of meeting the economic and operating requirements of such systems, provided desirable species can be maintained.

Underwater Sound as a Biological Stimulus

Abstract: Of all the sensory stimuli discussed in this volume, only sound allows longrange transmission of information underwater. This is a consequence of the extraordinarily low attenuation of sound in water and the ability of sound speed gradients in the ocean to channel sound so that it can propagate without interaction with the surface or bottom.

Ingratiatory Behaviors in Organizational Settings

Abstract: Social psychological research and work in the areas of upward influence, organizational politics, and impression management document the use of ingratiatory behaviors for the purpose of altering (shaping) positively the evaluations or attributions of relevant others. We examine four aspects of the ingratiation process. First, we define and distinguish ingratiation from other related, but not identical, constructs. Second, we present a dynamic model of the process and review the literature on which the model is based. Third, we present issues for future research that follow directly from the model. Finally, we summarize the important theoretical and practical issues raised by our review.

Crafting a Compiler

Abstract: Clear description of algorithms and clean design of compiler components. Crafting a Compiler presents a practical approach to compiler construction with thorough coverage of the material and examples that clearly illustrate the concepts in the book. Unlike other texts on the market, Fischer/Cytron/LeBlanc uses object-oriented design patterns and incorporates an algorithmic exposition with modern software practices. An ideal reference and tutorial. MARKET: Software engineers, systems analysts, software architects

Precursory seismic quiescence

Abstract: Seventeen cases of precursory seismic quiescence to mainshocks with magnitudes fromM L=4.7 toM S=8.0 are summarized. The amount of rate decrease ranges from 45% to 90%. The significance of these changes varies between 90% and 99.99%. The assumption that the background rate is approximately constant is fulfilled in most crustal volumes studied. All quiescence anomalies seem to have abrupt beginnings, and the rate during the anomalous period is fairly constant. The duration of the precursors ranges from 15 to 75 months, and it is not clear what factors determine that time. At least three successful predictions have been based on seismic quiescence. These cases have shown that mainshocks can be predicted based on quiescence, but they have also shown that the interpretation of the data in real time is difficult and nonunique. If a false alarm is defined as a period of quiescence with a significance level larger than a precursory quiescence in the same tectonic area, then we estimate, based on searches in four areas, that the false alarm rate may be on the order of 50%. Failure to predict may be expected in perhaps 50% of mainshocks, even in carefully monitored areas. Quiescence cannot be used as a precursor in tectonic environments with low seismic activity. Most characteristics of the phenomenon are still poorly defined, but data exist which probably permit at least a doubling of the presently available data on case histories.

Phase locking of Josephson-junction series arrays

Abstract: We report the results of a stability analysis of coherent oscillations in series arrays of Josephson junctions shunted by a common load. The analysis has found the parameter values for which the coherent, in-phase solution is stable and gives a quantitative measure of the stability. We find that arbitrarily large, dc-biased, arrays of Josephson junctions will phase lock most strongly when the capacitance parameter ${\ensuremath{\beta}}_{c}$\ensuremath{\approxeq}1 and the bias current is about the same as the critical current of the individual junctions. We use bifurcation theory to discuss the role that symmetry plays in determining the form and the stability of these oscillations. Simulations with up to 100 junctions confirm the results of the stability analysis. Arrays of nearly identical junctions are also discussed.

Advanced Engineering Dynamics

Abstract: This text offers a clear and refreshing exposition of the dynamics of mechanical systems from an engineering perspective. Basic concepts are thoroughly covered, then applied in a systematic manner to solve problems in mechanical systems that have recognisable applications to engineering practice. All theoretical discussions are accompanied by numerous illustrative examples, and each chapter offers a wealth of homework problems. The treatment of the kinematics of particles and rigid bodies is extensive. In this new edition, the author has revised and reorganized sections to enhance understanding of physical principles, and he has modified and added examples, as well as homework problems. The new edition also contains a thorough development of computational methods for solving the differential equations of motion for constrained systems.

Using the nematode Caenorhabditis elegans to predict mammalian acute lethality to metallic salts.

Abstract: The acute lethality of the salts of eight metals--HgCl2, BeSO4.4H2O, Al(NO3)3.9H2O, CuCl2.2H2O, ZnCl2, Pb(NO3)2, CdCl2, and Sr(NO3)2--was determined using a type of free-living nematode, Caenorhabditis elegans. The LC50 values were compared to the published mammalian oral LD50 values for salts of the same metals. Within this set of chemicals, C. elegans was found to be a predictor of mammalian acute lethality, generating LC50 values parallel to the rat and mouse LD50 values. The total expenses for this testing are about 10% of the cost for mammalian acute lethality testing. The method is considered to have great promise, but further study is needed.

Influence of preparation conditions on the composition of type B carbonated hydroxyapatite and on the localization of the carbonate ions.

Abstract: It is shown how certain aspects of the composition and structure of carbonated apatites depend strictly on preparation conditions, for example, excess of phosphate or calcium ions in the reaction medium, CO3 2− concentration, pH, ammonia added or not. Depending on those conditions, either one or the other of the two proposed mechanisms of introduction of carbonate ions into the B sites is dominant. The mechanisms are (1) replacement of a phosphate ion by a carbonate ion with the formation of three vacancies, one in a phosphate oxygen site and one each in the neigh-boring Ca2+ and OH− sites; and (2) replacement of a phosphate ion by a carbonate accompanied by a hydroxyl ion. Whether mechanism (1) is observed to dominate over mechanism (2), or vice versa, is accounted for by the relative concentrations of the various ions in the reaction medium. The number of vacancies is decreased by the presence of either, or both, excess calcium ions or ammonia in the reaction medium. A structural-chemical mechanism is advanced for the view that, with the smallest CO3 2− content, the A sites are favored but with increasing carbonate content the B sites become favored and the A-site content becomes less than it is when the total carbonate content is less.

Comment: Organizations Do Not Cognize

Abstract: The article presents a commentary on the paper “Conceptualizing and measuring organizational and psychological climate: Pitfalls in multilevel research,” by W. H. Glick. The authors note that Glick's paper contains some inconsistencies. They explain that it is difficult to understand how Glick defined organizational climate (OC) as a nonpsychological, organizational variable that is different from a shared assignment of psychological meaning. The authors contend that methodological discussion and decisions should follow questions such as whether it makes sense to aggregate a psychological variable to a situational level of analysis.

On the Controllability and Observability of Hybrid Systems

Abstract: This paper considers a special class of hybrid systems, whose state space is a cross-product space of an Euclidean space and a finite-state space. Such models may be used to represent systems subject to known abrupt parameter variations, such as commutated networks. They may also be used to approximate some types of time-varying systems. The paper investigates controllability, observability, and stability of hybrid systems. In particular, it derives a necessary and sufficient algebraic condition, a simple algebraic criterion, and a computationally simple algebraic sufficient test for controllability and observability. Moreover, it provides a simple sufficient stability condition.