Showing papers by "Purdue University published in 1988"

Variable structure control of nonlinear multivariable systems: a tutorial

Abstract: The design of variable-structure control (VSC) systems for a class of multivariable, nonlinear, time-varying systems is presented. Using the Utkin-Drazenovic method of equivalent control and generalized Lyapunov stability concepts, the VSC design is described in a unified manner. Complications that arise due to multiple inputs are examined, and several approaches useful in overcoming them are developed. Recent developments are investigated, as is the kinship of VSC and the deterministic approach to the control of uncertain systems. All points are illustrated by numerical examples. The recent literature on VSC applications is surveyed. >

Entrepreneurs' Perceived Chances for Success

Abstract: Explores the expectations of entrepreneurs in newlyestablished businesses regarding their own chances of success and theirpredictionsregarding the chances for success of others with similarstartup ideas, in one of the first such studies. Past research suggests that,at best, fewer than 50% of firms survive for more than five years with a givenowner/manager. Based on this past research, three hypotheses are posited:entrepreneurs will perceive their odds of success at less than or equal to 50%,entrepreneurs' prediction of others' success will not differ significantly fromtheir prediction of their own success, and entrepreneurs' expectations ofsuccess will be related to a number of personal factors including theirbusiness experience, prior ownership, and educational level. Data were gathered from surveys sent in 1985 to members of the NationalFederation of Independent Business (NFIB) who reported that they had openedtheir own businesses in the United States. Of those responding, 2994entrepreneurs were selected from the original sample. Findings did not support any of the three original hypotheses of cautiousoptimism (as prior research predicted). In fact, the results show thatentrepreneurs' perceptions of their own odds for success display a noteworthydegree of optimism. In addition, entrepreneurs believe their own odds ofsuccess to be greater than other new business owners with similar ideas.Furthermore, an analysis of the predicted factors for success showed aremarkable lack of relationship between an entrepreneur's belief of their ownpotential and the objective predictors. In fact, those who were poorly preparedseemed just as optimistic as those who were well prepared. One implication isthat business founders should seek advice from more objective outsiders.(SFL)

Progress in understanding jointing over the past century

Abstract: Joints are the most common result of brittle fracture of rock in the Earth's crust. They control the physiography of many spectacular landforms and play an important role in the transport of fluids. In its first century, the Geological Society of America Bulletin has published a significant number of papers on joints and jointing. One hundred years ago, there were lively debates in the literature about the origin of joints, and detailed descriptions of joints near the turn of the century catalogued most geometric features that we recognize on joints today. In the 1920s, theories relating joint orientation to the tectonic stress field and to other geologic structures led to a proliferation of data on the strike and dip of joints in different regions. The gathering of orientation data dominated work on joints for the next 50 yr. In the 1960s, key papers re-established the need to document surface textures, determine age relations, and measure relative displacements across joints in order to interpret their origins. At about this time, fundamental relationships from the fields of continuum and fracture mechanics were first used to understand the process of jointing. In the past two decades, we have witnessed an effort to use field data to interpret the kinematics of jointing and to understand the initiation, propagation, interaction, and termination of joints. Theoretical methods have been developed to study the evolution of joint sets and the mechanical response of a jointed rock mass to tectonic loading. Although many interesting problems remain to be explored, a sound conceptual and theoretical framework is now available to guide research into the next century.

Handbook of Numerical Heat Transfer

Abstract: A comprehensive presentation is given of virtually all numerical methods that are suitable for the analysis of the various heat transverse and fluid flow problems that occur in research, practice, and university instruction. After reviewing basic methodologies, the following topics are covered: finite difference and finite element methods for parabolic, elliptic, and hyperbolic systems; a comparative appraisal of finite difference versus finite element methods; integral and integrodifferential systems; perturbation methods; Monte Carlo methods; finite analytic methods; moving boundary problems; inverse problems; graphical display methods; grid generation methods; and programing methods for supercomputers.

Internetworking with TCP/IP: principles, protocols, and architecture

Abstract: From the Publisher: The third edition of this all-time best-selling book is still the reference for anyone who wants to work with the TCP/IP protocol suite. TCP/IP and ATM are two of the most important networking technologies. This is the first book that shows how to use the two technologies together.

A family of human CCAAT-box-binding proteins active in transcription and DNA replication: cloning and expression of multiple cDNAs

Abstract: The CTF/NF-I group of cellular DNA binding proteins recognizes the sequence GCCAAT and is implicated in eukaryotic transcription as well as DNA replication. Molecular analysis of human CTF/NF-I complementary DNA clones reveals multiple messenger RNA species containing alternative coding regions, apparently as a result of differential splicing. Expression and functional analysis establish that individual gene products can bind to GCCAAT recognition sites and serve both as promoter-selective transcriptional activators and as initiation factors for DNA replication.

Scanning tunneling microscopy and atomic force microscopy: application to biology and technology

Abstract: The scanning tunneling microscope (STM) and the atomic force microscope (AFM) are scanning probe microscopes capable of resolving surface detail down to the atomic level. The potential of these microscopes for revealing subtle details of structure is illustrated by atomic resolution images including graphite, an organic conductor, an insulating layered compound, and individual adsorbed oxygen atoms on a semiconductor. Application of the STM for imaging biological materials directly has been hampered by the poor electron conductivity of most biological samples. The use of thin conductive metal coatings and replicas has made it possible to image some biological samples, as indicated by recently obtained images of a recA-DNA complex, a phospholipid bilayer, and an enzyme crystal. The potential of the AFM, which does not require a conductive sample, is shown with molecular resolution images of a nonconducting organic monolayer and an amino acid crystal that reveals individual methyl groups on the ends of the amino acids. Applications of these new microscopes to technology are demonstrated with images of an optical disk stamper, a diffraction grating, a thin-film magnetic recording head, and a diamond cutting tool. The STM has even been used to improve the quality of diffraction gratings and magnetic recording heads.

Performance differences among strategic group members

Abstract: Whether and why members of the same strategic group would experience different performance results has received little attention in previous research. These questions are addressed in this paper. First, conventional theory on the relationship between firm performance and strategic group membership is reviewed. Then a theory is developed as to how historical differences among strategic group members may result in performance differences. An empirical analysis of risk and return relationships is conducted, centered on the nature of environmental change characterizing the industry. The empirical setting throughout is the U.S. pharmaceutical industry over the period 1963–82.

Nodal sets of eigenfunctions on Riemannian manifolds.

Abstract: Soit M n une variete connexe compacte a metrique Riemannienne C ∞ . Soit Δ le laplacien de M. Soit F une fonction propre reelle de Δ de valeur propre λ. On demontre que la fonction propre F s'annule au plus a l'ordre c(λ) 1/2 pour tout point dans M

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.

Flight dynamics of aeroelastic vehicles

Abstract: The nonlinear equations of motion for an elastic airplane are developed from first principles. Lagrange's equation and the Principle of Virtual Work are used to generate the equations of motion, and aerodynamic strip theory is then employed to obtain closed-form integral expressions for the generalized forces. The inertial coupling is minimized by appropriate choice of the body-reference axes and by making use of free vibration modes of the body. The mean axes conditions are discussed, a form that is useful for direct application is developed, and the rigid-body degrees of freedom governed by these equations are defined relative to this body-reference axis. In addition, particular attention is paid to the simplifying assumptions used during the development of the equations of motion. Since closed-form, analytic expressions are obtained for the generalized aerodynamic forces, insight can be gained into the effects of parameter variations that is not easily obtained from numerical models. An example is also presented in which the modeling method is applied to a generic elastic aircraft, and the model is used to parametrically address the effects of flexibility. The importance of residualizing elastic modes in forming an equivalent rigid model is illustrated, but as vehicle flexibility is increased, even modal residualization is shown to yield a poor model.

Structural instability and relaxation in liquid and glassy phases near the fragile liquid limit

Abstract: We consider two sorts of structural instability of glassy substances, each of which may be released by a relaxation process with its own characteristic relaxation time, and specific kinetic features. The first of these is the instability against relaxation out of the amorphous state into the crystalline state, while the second is the instability against relaxation within the amorphous state itself. The latter may often involve relaxation out of a homogeneous amorphous phase into a two-phase amorphous structure, but we will not specifically consider this liquid-liquid phase separation process here. In most glasses, the former (which is no more than the characteristic nucleation time) is much longer than the latter time. However, there are important classes of glasses, for instance the metallic glasses, in which the former is in fact the shorter time, a fact which is responsible for the inability to observe the glass transition phenomenon in such substances. In this paper we will be considering the relation between these two times and the specific kinetics of each. The nucleation time has been the subject of theoretical developments over a number of decades, and details will be omitted in order to concentrate on experimental studies of this phenomenon. We will described briefly the recently developed DSC techniques for determining the classical time-temperature-transformation curves for a variety of supercooled liquids, and the relation of these to the nucleation curves. The relaxation process within the amorphous state, which can be observed for cases where the nucleation time is relatively long, has a number of features which currently lack a complete explanation. In most cases the relaxation process is non-Arrhenius in its temperature dependence, nonexponential in its time dependence, and nonlinear in its structural state dependence. Some examples taken from glasses at the “fragile” edge of the deduced viscosity-temperature pattern for glassforming liquids are dealt with in detail, and the distinction between shear stress relaxation and thermodynamic stress relaxation is made. The possibility that near T g the latter relaxation time remains Vogel-Fulcher in form with T 0 ≡ T K (the Kauzmann temperature), in contrast with the common observations for (the decoupled) shear relaxation, is raised. Strong support for this notion is found in the current “specific heat spectroscopy” results of Nagel and co-workers. Microscopic relaxation processes, as observed using spectroscopic probes and neutron scattering techniques, are reviewed, and the difference in non-exponentiality from macroscopic relaxation are examined in the light of current theories. Finally, secondary relaxations in ionic and molecular glasses, and their relation to the fastest of all glassy state relaxation processes, the tunnelling modes (TLS), are briefly considered.

Pharmaceutical and Medical Aspects of Bioadhesive Systems for Drug Administration

Abstract: Bioadhesion could lead to the solution of bioavailability problems resulting from a too short stay of the pharmaceutical dosage form at the absorption or activity level of the active ingredient. Bioadhesion stages are: intimate contact resulting from a good wetting of the bioadhesion surface and the swelling of the bioadhesive polymer, then penetration of the bioadhesive into the crevice of the tissue surface or interpenetration of bioadhesive chains with those of the mucus, and finally low chemical bonds. date, the most important bioadhesive polymers are polycarbophil a Carbopol 934. Methods of studying bioadhesion are described as well as the existing bioadhesive dosage forms.

Structured Interviewing: Raising the Psychometric Properties of the Employment Interview.

Abstract: A highly structured employment interviewing technique is proposed, which includes the following steps: (1) develop questions based on a job analysis, (2) ask the same questions of each candidate, (3) anchor the rating scales for scoring answers with examples and illustrations, (4) have an interview panel record and rate answers, (5) consistently administer the process to all candidates, and (6) give special attention to job relatedness, fairness, and documentation in accordance with testing guidelines. Examination of psychometric properties for hiring entry-level production employees (n= 149) reveals high interrater reliability (r= .88) and predictive validity (uncorrected r= .34, corrected r= .56), as well as evidence for test fairness and utility. The levels of these properties are comparable to those of a comparison battery of typical employment tests, and correlations with the tests suggest that the interview has a strong cognitive aptitude component. Potential explanations for the effectiveness of this structured interviewing technique are discussed.

Natural astringency in foodstuffs--a molecular interpretation.

Abstract: The structures of plant polyphenols (vegetable tannins) are briefly reviewed. Their interactions with proteins, polysaccharides, and the alkaloid caffeine are discussed at the molecular level, and these fundamental properties are related to the quality of astringency that polyphenols possess. The various ways in which astringency may be modified and ultimately lost are outlined in relation to the aging of red wines, the formation of nonbiological hazes in beers and lagers, and the ripening of fruit.

Cybernetics and Dependence: Reframing the Control Concept

Abstract: Control is defined as the cybernetic regulation of iterative activity within dependence relationships. This framework is used to examine critical aspects of control and its initiation. Two quasi-control responses, dependence reduction and dependence restructuring, are proposed and discussed. Implications of the framework for research and managerial practice are discussed.

Poverty orderings and welfare dominance

Abstract: This paper examines the partial orderings of discrete distributions derived from various poverty indices and sets of welfare functions. The poverty ordering with respect to some index P is the ordering obtained when P ranks consistently over a range of admissible poverty lines. The poverty orderings derived from the headcount ratio, the per-capita income gap and another “distribution-sensitive” index are characterized in some detail when the poverty standard is allowed to take any positive value, and these orderings are shown to coincide with the natural interpretation of first, second and third degree “welfare dominance”, respectively. Additional results are then obtained for the situation in which the admissible poverty lines cannot exceed some finite upper bound.

Intracellular Compartmentation of Ions in Salt Adapted Tobacco Cells

Abstract: Na+ and Cl− are the principal solutes utilized for osmotic adjustment in cells of Nicotiana tabacum L. var Wisconsin 38 (tobacco) adapted to NaCl, accumulating to levels of 472 and 386 millimolar, respectively, in cells adapted to 428 millimolar NaCl. X-ray microanalysis of unetched frozen-hydrated cells adapted to salt indicated that Na+ and Cl− were compartmentalized in the vacuole, at concentrations of 780 and 624 millimolar, respectively, while cytoplasmic concentrations of the ions were maintained at 96 millimolar. The morphometric differences which existed between unadapted and salt adapted cells, (cytoplasmic volume of 22 and 45% of the cell, respectively), facilitated containment of the excited volume of the x-ray signal in the cytoplasm of the adapted cells. Confirmation of ion compartmentation in salt adapted cells was obtained based on kinetic analyses of 22Na+ and 36Cl− efflux from cells in steady state. These data provide evidence that ion compartmentation is a component of salt adaptation of glycophyte cells.

Comparison of two-sensor tracking methods based on state vector fusion and measurement fusion

Abstract: There are two approaches to the two-sensor track-fusion problem. Y Bar-Shalom and L. Campo (ibid., vol.AES-22, 803-5, Nov. 1986) presented the state vector fusion method, which combines state vectors from the two sensors to form a new estimate while taking into account the correlated process noise. The measurement fusion method or data compression of D. Willner et al. (1976) combines the measurements from the two sensors first and then uses this fused measurement to estimate the state vector. The two methods are compared and an example shows the amount of improvement in the uncertainty of the resulting estimate of the state vector with the measurement fusion method. >

Drug/Polymer Matrix Swelling and Dissolution

Abstract: The swelling and dissolution behavior of pharmaceutical systems containing a drug and a polymer can be analyzed by a mathematical model which predicts the drug released and the gel layer thickness as a function of time It is possible to approximate the values of several of the physicochemical parameters of this model in order to obtain an order-of-magnitude analysis of the tablet dissolution process Selected experimental results of tablet dissolution and drug release are analyzed and conclusions are made about the importance of the drug and polymer content and solubility in the release behavior

Stabilized mixed methods for the Stokes problem

Abstract: The solution of the Stokes problem is approximated by three stabilized mixed methods, one due to Hughes, Balestra, and Franca and the other two being variants of this procedure. In each case the bilinear form associated with the saddle-point problem of the standard mixed formulation is modified to become coercive over the finite element space. Error estimates are derived for each procedure.

Model-independent constraints on possible modifications of Newtonian gravity.

Abstract: New model-independent constraints on possible modifications of Newtonian gravity over solar-system distance scales are presented, and their implications discussed. The constraints arise from the analysis of various planetary astrometric data sets. The results of the model-independent analysis are then applied to set limits on a variation in the l/r-squared behavior of gravity, on possible Yukawa-type interactions with ranges of the order of planetary distance scales, and on a deviation from Newtonian gravity of the type discussed by Milgrom (1983).