Showing papers by "Worcester Polytechnic Institute published in 1977"

Wald's Test as Applied to Hypotheses in Logit Analysis

Abstract: For tests of a single parameter in the binomial logit model, Wald's test is shown to behave in an aberrant manner. In particular, the test statistic decreases to zero as the distance between the parameter estimate and null value increases, and the power of the test, based on its large-sample distribution, decreases to the significance level for alternatives sufficiently far from the null value.

Theory of a two-photon laser amplifier

Abstract: We discuss the propagation of an electromagnetic pulse through an active medium prepared in a state of inversion between two levels of the same parity. Since no electric dipole transition is possible between the chosen atomic levels, we investigate the possibility of amplification of an injected signal having a carrier frequency equal to one-half the atomic-transition frequency. We show that under suitable conditions a nonlinear atomic polarization can be generated which oscillates at the same frequency as the incident electromagnetic pulse. The coupled atom-field evolution is described by the usual self-consistent approach. When atomic relaxation effects are negligible, we derive an equation describing the spatial evolution of the energy of the propagating pulse. From this equation we characterize the threshold condition for power amplification and classify the multiple steady-state solutions of the propagation problem. The evolution of the pulse envelope through the amplifier is analyzed with the help of a hybrid computer simulation. Pulse-envelope modulation and multiple-pulse formation even in the asymptotic limit of long amplifiers are displayed.

Liquid diffusion in microporous alumina pellets

Abstract: The effect of the ratio of the molecular solute diameter to the pore diameter and adsorption equilibrium on the liquid phase effective diffsivity for different hydrocarbon solutes was studied in two alumina pellets. A semiemprical correlation based on the relative dimension of the solute molecule with respect to the average pore dimension, the equilibrium partition coefficient, and the porosity is proposed for a variety of binary hydrocarbon systems. The correlation shows that the effective diffusivity is strongly influenced by both the adsorption coefficient as well as the ratio of the solute molecular size to the average pore size.

Energetical factors in power systems with nonlinear loads

Abstract: The classical definitions for the energetical determining factors in power systems are reviewed and a new model for the apparent power is suggested. — Based on the volt-ampere characteristic of the nonlinear load, an equivalent circuit, containing linear elements, can be determined. In this way, load-flow and harmonic compensation studies can be simplified.

Diffusional and thermodynamic interactions in the Cu-Ni-Zn system at 775°C

Abstract: Diffusion was investigated in both α(fcc) and β(bcc) phase regions of the Cu-Ni-Zn system at 775°C with solid-solid diffusion couples and interdiffusion coefficients were determined at several compositions. Intrinsic and interdiffusion coefficients were also estimated from available data on thermodynamic activities and tracer diffusivities for α Cu-Ni-Zn alloys; and the estimated coefficients were consistent with those experimentally determined. Large off-diagonal coefficients indicating strong interactions among the diffusing species were observed and could be appreciated in terms of the compositional dependence of the thermodynamic activities of the components.

Problem in the determination of correlation functions. II

Abstract: This Letter extends the treatment of an earlier note. This time we take into account corrections in the correlation function that must be made when both the mean slope as well as the mean reference level are not known. Again the true correlation function requires the solution of an integral equation.

Formaldehyde base catalysis by NaX zeolite

Abstract: Reactions of formaldehyde to produce formose sugars at 95°C in aqueous solutions were studied over a trickle bed of NaX Zeolite spheres. When effluent pH was in the range of 5 to 7, a rapid irreversible catalyst deactivation from an initial 50% conversion occurred. The catalyst was destroyed in less than five hours by formic acid produced by the undesired Cannizzaro reaction. Incorporation of 0.86 mol NaOH/mol HCHO at 1.21 LHSV into the combined feed to the reactor maintained the effluent pH in the range of 10 to 12. Conversion of HCHO fell only from 95 to 92% in three hours, and selectively to Cannizzaro reaction was reduced to approximately 25%.

Interdependence and innovation

Abstract: This article analyzes the relationships beyond the firm for their effects upon innovation. It is argued that as technology becomes increasingly complex close interfirm cooperation will be needed. In this study, twenty-two innovations were examined particularly focusing on the interaction between the firm and the environment. It was found that there was a significant correlation between innovation success and the firms' use of other firms. The role of government, universities, and outside inventors on innovation within the firm is also discussed.

The New Deal, Cuba, and the Rise of a Global Foreign Economic Policy

Abstract: It is generally held that the intense domestic preoccupations of the early New Deal were complemented by a cautious and reactive foreign policy that responded to a strong mood of isolationism in the country. The generalization does not apply to Cuba, where the level and extent of United States involvement actually increased during the period. This article explores the background of this increased involvement and its relationship to later periods of United States foreign policy that were actively internationalist, and seeks to show that the New Deal policy toward Cuba in the early 1930s involved precedent-setting actions that helped to form the basis for the globalist perspective of the 1940s and beyond. By the spring of 1933, economic depression and political dictatorship had brought the island of Cuba to the brink of economic collapse and social upheaval. The billion-dollar United States investment in the island was faced with ruin, and the regime of President Gerardo Machado, sustained for eight years by Wall Street loans and State

Zircaloy-4 oxidation in steam under transient oxidizing conditions

Abstract: Oxidation of Zircaloy-4 in unlimited steam has been studied under conditions simulating a loss of coolant accident (LOCA) using a specimen heating system ("Gleeble"). Simple linear ramp transients have been analyzed as well as a few postulated LOCA transients for currently operating light water nuclear power plants. Comparison is made between computer code prediction using isothermal oxidation kinetics and experimental observation with regard to the extent of oxidation. Simulation of Zircaloy oxidation assuming a stepwise isothermal model using isothermal kinetics developed by the authors is compared to experimental measurements of the extent of oxidation. This computer code, designated TRANS 1, accounts for prior oxidation present and results in agreement with experimental measurements of oxide and oxygen stabilized α-thicknesses for high heating and slow cooling rate transient profiles. However, as heating rate decreases and cooling rate increases, this model becomes increasingly conservative. Modeling, using either a series-expansion or a slope-based isothermal kinetics model, results in essentially the same prediction as TRAMS 1. A one-dimensional finite-difference moving-boundary diffusion model has been developed and found to predict accurately isothermal oxidation behavior of Zircaloy-4 in steam. This model also can be used to predict transient behavior. In addition to predicting oxide and stabilized a thicknesses, this code is capable of predicting oxygen concentration gradients in all phases present, total oxygen as the summation of oxygen present in each phase, and formation of oxygen stabilized α-incursions in the d-phase if accurate diffusion coefficients and appropriate phase equilibrium information are known.

Upper and Lower Probability Inferences Pertaining to Poisson Processes

Abstract: A general system of inference which leads to upper and lower posterior distributions has been proposed by Dempster (1966, 1968a, 1968b). This general theory of inference is applied to various estimation problems arising in Poisson processes. In particular, the emphasis is on the estimation of the parameter of the process and on the prediction of the number of future events, given the observed data. In this article, all upper and lower probability inferences are generated by random intervals

Policy and Technology: The Employed Inventor

Abstract: An important issue of modem public policy is the creation of instruments which can operate as incentives for the achievement of social goals. Organizations can be stimulated in many ways such as legal compulsion, public pressure, or self-motivated initiative. It is important for policymakers to consider which type of stimulus will produce the desired objectives.

Effect of Branch Spacing on Losses for Dividing Flow

Abstract: Since few data are available regarding the effect of branch spacing on discharge and energy loss coefficients for dividing flow, tests were conducted for a line manifold using three branches. A branch geometry typical of an actual diffuser design was used, and the branch to main pipe diameter ratio and the relative spacing between branches was varied by increments. The variation in discharge coefficient is presented as a function of the ratio of velocity head to total head, whereas loss coefficients are plotted versus relative velocity. A family of curves for each diameter ratio shows the effect of relative branch spacing. Test data indicated that the branch discharge coefficient increased and branch losses decreased with a decrease in spacing due to the change in velocity profile in the main pipe. However, the loss coefficient for flow past the branch in the main pipe increased with a decrease in spacing.

Optimum Working Time

Abstract: The familiar problem relating to the tradeoff between direct and indirect cost relative to project duration is solved in closed form. Elementary cost minimizing methods give simple algebraic expressions that optimize constraints. The following rule evolves: The optimum working time for a particular operation is when the total cost for variable overheads (time dependent) equals the total cost to mobilize and demobilize all of the crews. This least-cost solution is not altered by working overtime as a means of reducing equipment requirements. The theoretical solution is illustrated with a solved problem employing the derived formulas as well as by iteration for comparison and sensitivity. The solution to the problem of optimum working time also gives the solution to the problem of the optimum number of crews that should be employed.

Contribution to the analysis and optimization of transposed concentric conductors

Abstract: The principle of transposed tublar conductor is explained. An exact analytical solution for current distribution and skin effect ratio is developed. The optimum geometry and comparisons with nontransposed conductors are presented.

The handling characteristics of surgical sutures

Abstract: The flexural rigidity of four sizes of fourteen different types of sutures were measured using Peirce's ring loop method. The suture materials were ranked according to the lowest value of flexural rigidity. This ranking strongly correlated (r=0.93) with the ranking of handling characteristics obtained thru a survey of practicing surgeons. Thus flexural rigidity can be used as a significant criterion for quantifying the handling characteristics of surgical sutures.

A comparison principle for steady-state diffusion operators

Abstract: Publisher Summary This chapter presents a comparison principle for steady-state diffusion operators. Physical intuition suggests that an analog of the familiar linear comparison principle (inequality on the boundary and satisfaction of a differential inequality implies inequality in the interior) should remain valid even if the diffusion coefficient varies fairly arbitrarily with concentration and its gradient so long as that coefficient remains positive and thereby preserves the basic character of Fickian diffusion. The comparison principle confirms this suggestion. The operators of similar mathematical structure also occur in the Reynold's equation of gas lubrication theory and in the minimal surface problem.