Showing papers by "Carnegie Mellon University published in 1970"
TL;DR: In this paper, the main Hall-effect mechanism was shown to be the main mechanism for the dc Hall effect for Fe, Ni, and their alloys above 100 K, while asymmetric scattering dominates below 100 K.
Abstract: The center of mass of a wave packet undergoes a discontinuous and finite sideways displacement on scattering by a central potential, in the presence of spin-orbit interaction. This is the main Hall-effect mechanism (${\ensuremath{\rho}}_{H}\ensuremath{\propto}{\ensuremath{\rho}}^{2}$) for Fe, Ni, and their alloys above 100 K, while asymmetric scattering dominates below 100 K. Displacement $\ensuremath{\Delta}y$ per actual collision is calculated by partial waves. In the case of Born expansion, the leading term of $\ensuremath{\Delta}y or \frac{{\ensuremath{\rho}}_{H}}{{\ensuremath{\rho}}^{2}}$ is of zero order in the scattering potential. The magnitude is predicted correctly ($\ensuremath{\Delta}y\ensuremath{\approx}{10}^{\ensuremath{-}10}\ensuremath{-}{10}^{\ensuremath{-}11}$ m) when using the effective spin-orbit Hamiltonian derived by Fivaz from spin-orbit interband mixing. The calculation of ${\ensuremath{\rho}}_{H}$ is extended to arbitrary ${\ensuremath{\omega}}_{c}\ensuremath{\tau}$ for compensated and un-compensated metals. Other nonclassical physical mechanisms proposed by Karplus and Luttinger and by Doniach and by Fivaz are spurious for the dc Hall effect.
992 citations
TL;DR: In this article, a mathematical model of one aggregative mechanism, the electoral process, is conceptualized as a multidimensional model of spatial competition in which competition consists of candidates affecting turnout and the electorate's perception of each candidate's positions, and in which the social choice is a policy package which the victorious candidate advocates.
Abstract: The fundamental process of politics is the aggregation of citizens' preferences into a collective—a social—choice. We develop, interpret, and explain non-technically in this expository essay the definitions, assumptions, and theorems of a mathematical model of one aggregative mechanism—the electoral process. This mechanism is conceptualized here as a multidimensional model of spatial competition in which competition consists of candidates affecting turnout and the electorate's perception of each candidate's positions, and in which the social choice is a policy package which the victorious candidate advocates.This approach, inaugurated by Downs's An Economic Theory of Democracy, and falling under the general rubric “spatial models of party competition,” has been scrutinized, criticized, and reformulated. To clarify the accomplishments of this formulation we identify and discuss in section 2 the general democratic problem of ascertaining a social preference. We review critically in section 3 the definitions and assumptions of our model. We consider in sections 4 and 5 the logic of a competitive electoral equilibrium. We assume in section 4 that the electorate's preferences can be summarized and represented by a single function; the analysis in section 5 pertains to competition between two organizational structures or two opposed ideologies (i.e., when two functions are required to summarize and represent the electorate's preference). Finally, we suggest in section 6 a conceptualization of electoral processes which facilitates extending and empirically testing our model.
627 citations
TL;DR: The thermodynamics of critical points in multicomponent systems, more generally systems with more than two independent variables (including binary fluid mixtures, the helium $\ensuremath{\lambda}$ transition, order-disorder transitions in alloys, and antiferromagnetism) are discussed from a unified geometrical point of view, in analogy with one component (liquid-vapor and simple-ferromagnetic) systems as mentioned in this paper.
Abstract: The thermodynamics of critical points in multicomponent systems, more generally systems with more than two independent variables (including binary fluid mixtures, the helium $\ensuremath{\lambda}$ transition, order-disorder transitions in alloys, and antiferromagnetism) are discussed from a unified geometrical point of view, in analogy with one-component (liquid-vapor and simple-ferromagnetic) systems. It is shown that, from a few simple postulates, the qualitative behavior near the critical point of quantities such as compressibilities, susceptibilities, and heat capacities, with different choices of the variables held fixed, can be easily predicted. A number of seemingly exceptional cases (such as critical azeotropy), which arise when critical or coexistence surfaces bear an "accidental" geometrical relationship with the thermodynamic coordinate axes, are explained in terms of the same postulates. The predicted results are compared with several theoretical models and experimental data for a variety of systems.
570 citations
TL;DR: This model contains as special cases a number of previously suggested models, including the structural balance model of Cartwright and Harary, Davis's clustering model, and the ranked-clusters model of Davis and Leinhardt.
Abstract: The authors focus on developing standardized measures for models of structure in interpersonal relations. A theorem is presented which yields expectations and variances for measures based on triads. Random models for these measures are discussed and the procedure is carried out for a model of a partial order. This model contains as special cases a number of previously suggested models, including the structural balance model of Cartwright and Harary, Davis's clustering model, and the ranked-clusters model of Davis and Leinhardt. In an illustrative exmaple, eight sociograms are analyzed and the general model is compared with the special case of ranked clusters.
494 citations
TL;DR: The present investigation demonstrates that subjects in a typical forced-compliance experiment are not only unable to recall their premanipulation attitudes correctly, but they actually perceive their postmanipulated attitudes to be identical to their pre manipulating attitudes.
Abstract: A controversy has arisen over the "interpersonal simulations" used by Bern to support his contention that his self-perception theory accounts for cognitive dissonance phenomena. Specifically, the critics challenge the implication of his analysis that the premanipulation attitudes of subjects in dissonance experiments are not salient in their postmanipulation phenomenology. The present investigation answers this challenge by demonstrating that subjects in a typical forced-compliance experiment are not only unable to recall their premanipulation attitudes correctly, but they actually perceive their postmanipulation attitudes to be identical to their premanipulation attitudes. Accordingly, they do not perceive any attitude "change." The epistemological aspects of the interpersonal simulation methodology are also discussed.
314 citations
TL;DR: The two-fluid critical mixing point in this article occurs at the intersection of three lines of critical points, in a suitable variable space, and a free energy function is proposed which removes certain discrepancies between classical (Landau) theory and experimental thermodynamic measurements.
Abstract: The two-fluid critical mixing point in ${\mathrm{He}}^{3}$ - ${\mathrm{He}}^{4}$ differs from ordinary critical points in that it occurs at the intersection of three lines of critical points, in a suitable variable space. A free-energy function is proposed which removes certain discrepancies between classical (Landau) theory and experimental thermodynamic measurements. Certain solid-state transitions (e.g., the metamagnetic-antiferromagnetic transition in Fe${\mathrm{Cl}}_{2}$) are thermodynamic analogs of critical mixing in ${\mathrm{He}}^{3}$ - ${\mathrm{He}}^{4}$.
272 citations
TL;DR: Examples are presented of several types of experimental toxicological studies where invalid conclusions would be reached by the improper consideration of the number of independent sampling units, N.
245 citations
TL;DR: The chemisorption of H2 and of O2 on Pt particles, supported on alumina, was studied in this article, where the particle size distributions from the micrographs were consistent with the 1:1 = H Pt stoichiometry, however, even at high dispersions where H Pt (total) was near unity, the error introduced probably cannot exceed 16.7%.
223 citations
TL;DR: In this paper, a study is made of a dynamic inventory model with stochastic lead times, in which it is assumed that orders do not cross in time and that the arrival probabilities are independent of the number and size of outstanding orders.
Abstract: A study is made of a dynamic inventory model with stochastic lead times. A probability model is developed for the arrival of outstanding orders in which it is assumed that orders do not cross in time and that the arrival probabilities are independent of the number and size of outstanding orders. With these assumptions, it is shown that the sequential multidimensional minimization problem normally associated with the random lead time model can be reduced to a sequence of one-dimensional minimizations. The minimizations are a function of a variable representing the sum of stock on hand plus all outstanding orders. Optimal ordering policies are characterized under the assumptions of convex expected holding and shortage costs, a linear ordering cost and a fixed setup cost greater than or equal to zero paid when the order is placed. These policies are shown to be quite similar to those obtained with deterministic lead times but some differences in the behavior of the single-period critical numbers when the setup cost is zero are noted.
215 citations
TL;DR: In this article, the importance of micellar catalysis in relation to mechanistic physical organic and bio-organic chemistry is discussed, to enable to design meaningful experiments in the area, and to guide one through the abundant literature of surfactants and solubilization.
Abstract: Publisher Summary This chapter reviews the importance of micellar catalysis in relation to mechanistic physical–organic and bio-organic chemistry, to enable to design meaningful experiments in the area, and to guide one through the abundant literature of surfactants and solubilization. Although solubilization by surface active agents has found considerable utility in pharmaceutical and industrial processes, the attention is primarily focussed on the mechanistic aspects of micellar catalyzed organic reactions. The subject is in its rapidly growing infancy, and is scattered and involves interdisciplinary collaboration among colloid, electro, structural, biological, pharmaceutical and organic chemists. The effects of many charged macromolecules, such as polymers, on ionic reactions can be qualitatively predicted on the basis of simple electrostatic considerations analogous to those involved in Hartley's rule.
TL;DR: Procedures are developed which permit a problem-solving program employing heuristics in production rule form to learn to improve its performance by evaluating and modifying existingHeuristics and hypothesizing new ones, either during an explicit training process or during normal program operation.
TL;DR: In this paper, a locally most powerful test is developed for the hypothesis that a slope coefficient in a linear time series model is stable, against the alternative that the slope shifts exactly once somewhere in the series.
Abstract: A locally most powerful test is developed for the hypothesis that a slope coefficient in a linear time series model is stable, against the alternative that the slope shifts exactly once somewhere in the series. Analysis of the procedure using artificial data indicates good power characteristics even when the ratio of the shift size to the error variance is moderate—especially if the shift does not occur very near either end of the series. Power also depends on the pattern of the independent variables and on whether the error variance is known or must be estimated using the residuals about the regression line.
TL;DR: In this paper, the authors investigated the effects of role overload and role underload on individuals' behavior, attitudes, and physiology, and found that role overload is stressful to the overloaded persons and that the effects are most severely experienced by individuals with specific personality constellations.
TL;DR: In this article, the authors argue that the distinction between candidates who maximise votes and candidates who maximize plurality should be disentangled, and that candidates that maximize votes are more likely to win than those that maximize plurality.
Abstract: Spatial models of party competition constitute a recent and incrementally developing literature which seeks to explore the relationships between citizens' decisions and candidates' strategies. Despite the mathematical and deductive rigor of this approach, it is only now that political scientists can begin to see the incorporation of those considerations which less formal analyses identify as salient, and perhaps crucial, features of election contests. One such consideration concerns the candidates' objectives. Specifically, spatial analysis often confuses the distinction between candidates who maximize votes and candidates who maximize plurality. Downs and Garvey, for example, assume explicitly that candidates maximize votes, though plurality maximization is clearly the assumption which Garvey actually employs, while Downs frequently assumes that vote maximization, plurality maximization, and the goal of winning are equivalent. Downs, nevertheless, attempts to disentangle these objectives, observing that plurality maximization is the appropriate objective for candidates in a single-member district, while vote maximization is appropriate in proportional representation systems with many parties. All subsequent spatial analysis research, however, assumes either implicitly or explicitly that candidates maximize plurality. If Downs is correct, therefore, this research may not be relevant for a general understanding of electoral competition in diverse constitutional or historical circumstances. The question then is whether those strategies that maximize votes differ from those strategies that maximize plurality.
01 Jan 1970
TL;DR: In this article, a theoretical analysis of the effects of an external field on the rheological properties of a dilute suspension of spherical particles containing embedded dipoles is presented, and the dynamical theory is applied to a diverse variety of fluid motions including Couette flow, two-dimensional Poiseuille flow and the flow arising from the translation of a macroscopic sphere through the suspension.
Abstract: A theoretical analysis is presented of the effects of an external field on the rheological properties of a dilute suspension of spherical particles containing embedded dipoles. These permanent dipoles may be gravitational, magnetic, or electrical in nature. Rotary Brownian motion is assumed negligible. Free rotation of the suspended particles resulting from the shear is hindered by the action of the field. This gives rise to a system of body couples and, hence, to a state of antisymmetric stress. In particular, the suspension is non-Newtonian and displays shear-thinning. The dynamical theory is applied to a diverse variety of fluid motions including Couette flow, two- and three-dimensional Poiseuille flows, and the flow arising from the translation of a macroscopic sphere through the suspension. The apparent viscosity is shown to vary with the orientation of the viscometer relative to the direction of the external field.
TL;DR: In this paper, it was shown that the duality of geometric programs is not affected by a "duality gap" and that the maximum of the dual geometric program is equal to the minimum of the primal geometric program.
Abstract: A geometric program concerns minimizing a function subject to constraint functions, all functions being of posynomial form. In this paper the posynomial functions are condensed to monomial form by the use of the inequality reducing a weighted arithmetic mean to a weighted geometric mean. The geometric mean is a monomial and by a logarithmic transformation it becomes a linear function. This observation shows that the condensed program is equivalent to a linear program. Moreover by suitable choice of the weights it is found that the minimum of the condensed program is the same as the minimum of the original programs. This fact together with the duality theorem of linear programming proves that the maximum of the dual geometric program is equal to the minimum of the primal geometric program. With this result as a basis a new approach to the duality properties of geometric programs is carried through. In particular it is shown that a “duality gap” cannot occur in geometric programming.
TL;DR: It is concluded that this study adds further evidence that aggression is not a unitary phenomenon and that different manipulations differentially affect different kinds of aggression.
TL;DR: In this article, it has been shown that the structure of cold water seems likely to consist, for the most part, of hydrogen-bonded, four-coordinated, framework regions with interstitial monomers occupying some fraction of the cavities the framework encloses.
Abstract: The train of thought pursued in this article has led to the conclusion that the structure of cold water seems likely to consist, for the most part, of hydrogen-bonded, four-coordinated, framework regions, with interstitial monomers occupying some fraction of the cavities the framework encloses. The precise geometry of the framework has not been specified, but some evidence suggests that it is rather regular at low temperatures and becomes more random as the water gets warmer. These conclusions, meager as they are in comparison with what we shall eventually need to know about water, are still "subject to change without notice." Such a change would, for instance, be made necessary by the discrediting either of the data or of the interpretations on which the model is based. The discovery of new facts, or of new meanings in old facts, which were clearly in conflict with the model, would also make it necessary to modify, if not to abandon, it. Even this would be progress, however, for it would be another product of the method of drawing upon data from diverse sources and would be a further step toward the progressively more comprehensive model to which this method will lead and the progressively greater confidence we will be able to place in our conclusions.
TL;DR: In the previous chapter we illustrated some of the ways that Bayesian analysis can be used in duopoly theory as mentioned in this paper, which is characterized by the fact that an infinite number of models can be generated by assuming different values for the conjectural variations term (Cohen and Cyert 1975; Kamien and Schwartz 1983).
Abstract: In the previous chapter we illustrated some of the ways that Bayesian analysis can be used in duopoly theory. Duopoly and oligopoly theory is characterized by the fact that an infinite number of models can be generated by assuming different values for the conjectural variations term (Cohen and Cyert 1975; Kamien and Schwartz 1983). No general solution exists and there is no basis, either empirical or theoretical, for preferring one of the models over the other.
TL;DR: The results suggest that a sliding filament mechanism operates in smooth muscle as well as in striated muscle and the suggestion that thick filaments aggregate prior to contraction and disaggregate during relaxation is promoted by these observations.
Abstract: Ordered arrays of thin filaments (65 A diameter) along with other apparently random arrangements of thin and thick filaments (100–200 A diameter) are observed in contracted guinea pig taenia coli rapidly fixed in glutaraldehyde. The thin-filament arrays vary from a few to more than 100 filaments in each array. The arrays are scattered among isolated thin and thick filaments. Some arrays are regular such as hexagonal; other arrays tend to be circular. However, few examples of rosettes with regular arrangements of thin filaments surrounding thick filaments are seen. Optical transforms of electron micrographs of thin-filament arrays give a nearest-neighbor spacing of the thin filaments in agreement with the "actin" filament spacing from x-ray diffraction experiments. Many thick filaments are closely associated with thin-filament arrays. Some thick filaments are hollow circles, although triangular shapes are also found. Thin-filament arrays and thick filaments extend into the cell for distances of at least a micron. Partially relaxed taenia coli shows thin-filament arrays but few thick filaments. The suggestion that thick filaments aggregate prior to contraction and disaggregate during relaxation is promoted by these observations. The results suggest that a sliding filament mechanism operates in smooth muscle as well as in striated muscle.
TL;DR: In this paper, the catalytic properties of C2H4 and C3H6 were investigated over silica-supported Pt, Pd, Ir, Ru, Ru and Rh.
TL;DR: It is shown that canonical forms do not exist for sufficiently rich classes of mathematical expressions, but with the aid of a nmnber- theoretic conjecture, a large subclass of the negative classes is shown to possess a canonical form.
Abstract: This paper deals with the simplification problem of symbolic mathematics. The notion of canonical form is defined and presented as a well-defined alternative to the concept of simplified form. Following Richardson it is shown that canonical forms do not exist for sufficiently rich classes of mathematical expressions. However, with the aid of a nmnber- theoretic conjecture, a large subclass of the negative classes is shown to possess a canonical form.
TL;DR: The purpose of this work is to demonstrate the usefulness of the diffusion theory approach to the optics of blood and to present information concerning the dependence of the scattering and absorption parameters for blood on the pertinent variables such as hemoglobin concentration, hematocrit, and optical wavelength.
Abstract: The results of calculations which use diffusion equations for photons to calculate optical transmission and backscattering by whole blood will be compared with a variety of published data. The purpose of this work is to demonstrate the usefulness of the diffusion theory approach to the optics of blood and to present information concerning the dependence of the scattering and absorption parameters for blood on the pertinent variables such as hemoglobin concentration, hematocrit, and optical wavelength.
Abstract: (1970). A Benefit-Cost Analysis of Auto Safety Features. Applied Economics: Vol. 2, No. 4, pp. 265-275.
TL;DR: The representational requirements for this problem area are defined and compared with current computer graphic languages, and four alternative data structures that allow automated space planning are described and compared.
Abstract: Problems involving the arrangement of objects in two- or three-space where the objective function primarily consists of derivatives of the distance between objects or their arrangement are called space planning problems. The representational requirements for this problem area are defined and compared with current computer graphic languages. Four alternative data structures that allow automated space planning are described and compared.
TL;DR: In this paper, a method for measuring grain boundary mobilities under the influence of a known driving force has been devised wherein hyperbola-like shapes are generated by capillary forces acting on a boundary originally subtending an acute angle α with a free surface.
TL;DR: In this article, the authors used hyperbola-like shapes generated by capillary forces acting on a boundary originally subtending an acute angle with a free surface to study the tilt boundary of NaCl bicrystals.
TL;DR: In this article, a diffusion model based on the simultaneous interdiffusion and reaction between alternate slabs of reactants is used to simulate the data of Vassilatos and Toor after slab sizes are chosen to fit the conversion data for very rapid reactions in a stoichiometric mixture.
Abstract: A diffusion model based on the simultaneous interdiffusion and reaction between alternate slabs of reactants is used to simulate the data of Vassilatos and Toor After slab sizes are chosen to fit the conversion data for very rapid reactions in a stoichiometric mixture, reasonably good predictions are obtained of the effect of stoichiometry and reaction velocity constant on conversion The results are close to the predictions of Kattan and Adler's stochastic mixing model, and the similar behavior of these disparate models implies that conversion is insensitive to the details of the mixing