Westinghouse Electric

About: Westinghouse Electric is a company organization based out in Cranberry Township, Pennsylvania, United States. It is known for research contribution in the topics: Brake & Circuit breaker. The organization has 27959 authors who have published 38036 publications receiving 523387 citations.

Instability of Cylindrical Voids in Alumina

Abstract: It is shown from experimental observation that cylindrical voids in polycrystalline alumina are unstable. When isothermally annealed, they undergo various configurational changes, in accordance with the theoretical prediction, prior to an ultimate breakup into rows of spherical voids. The breakup occurs by ovulation, if the aspect ratio is appropriate. If the required aspect ratio is not met, cylindrical voids are directly transformed into spherical voids by spheroidization. The predominant mechanism for void breakup on thermal anneal confirms a model for surface-diffusion-control material transport. The estimated surface-diffusion coefficients at the experimental annealing temperatures agree, within an order of magnitude, with the values reported in the literature.

Control engineering applications of V. I. Zubov's construction procedure for Lyapunov functions

Abstract: The determination of a stability domain of a control system, the motion of which is described by nonlinear differential equations, is often the object of intensive experimental and theoretical attack. This paper, partly tutorial and partly a presentation of new results, describes a method for obtaining a solution to this problem proposed recently by the Russian mathematician, V. I. Zubov. The tutorial part outlines the fundamental principles of V. I. Zubov's procedure for constructing Lyapunov functions for non-linear systems. If the construction problem can be solved, it leads to a Lyapunov function which uniquely defines the exact boundary of the stability region. For the application of the method, several simple examples are treated in which the exact stability region is found in analytic closed form. Since the construction procedure requires the solution of a linear partial differential equation, there are many cases for which an exact analytic solution is not possible. In some of these cases, however, it is possible to construct an approximate series solution which is always at least as good as the usual quadratic form Lyapunov function. The series construction procedure has been programmed (in IBM 7070 FORTRAN language) for a broad class of differential equations of the second order. A simple example solved by the digital computer program is described.

Deterministic, probabilistic and subjective modeling system

Abstract: A modeling system that arranges the model in a hierarchical structure of communicating and independently executing object modules controlled by an overall supervisor. Each object represents a component or a system and includes an object controller which communicates with other object modules, an object error checker and an object model. The objects communicate through a database accessible by all objects. The structure of the object module and the hierarchical structure itself are standardized allowing new components or systems to be added by adding a standard object module which includes an object model that is unique to the object being modeled. The controller for an object causes subobjects upon which the object model depends for data to be executed prior to execution of the object model. Such bottom up model traversal insures that models do not execute until all needed data is available. The error check module checks the controller and model modules to make sure they are executing properly. The object model includes a deterministic equation based component aging model, a statistical based component aging model and expert rules that combine the deterministic and statistical model with the knowledge of experts to determine the current state of the object and make recommendations concerning future actions concerning the object. A maintenance module is also included along side the supervisor that allows maintenance actions for the objects to be taken into consideration.

High temperature erosion resistant, abradable thermal barrier composite coating

Abstract: A composite thermal barrier coating system includes a honeycomb metallic structure (2) filled with high thermal expansion ceramic hollow spheres (6) in a phosphate bonded matrix. The composite thermal barrier coating system may be manufactured to thicknesses (T) in excess of current thermal barrier coating systems, thereby imparting greater thermal protection. Superior erosion resistance and abrasion properties are also achieved. The composite thermal barrier coating is useful on combustion turbine components such as ring seal segments, vane segment shrouds, transitions and combustors.