Wichita State University

About: Wichita State University is a education organization based out in Wichita, Kansas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 4988 authors who have published 9563 publications receiving 253824 citations. The organization is also known as: WSU & Fairmount College.

Eulerian Gaussian Beams for High Frequency Wave Propagation

Abstract: We design an Eulerian Gaussian beam summation method for solving Helmholtz equations in the high-frequency regime. The traditional Gaussian beam summation method is based on Lagrangian ray tracing and local ray-centered coordinates. We propose a new Eulerian formulation of Gaussian beam theory which adopts global Cartesian coordinates, level sets, and Liouville equations, yielding uniformly distributed Eulerian traveltimes and amplitudes in phase space simultaneously for multiple sources. The time harmonic wavefield can be constructed by summing up Gaussian beams with ingredients provided by the new Eulerian formulation. The conventional Gaussian beam summation method can be derived from the proposed method. There are three advantages of the new method: (1) We have uniform resolution of ray distribution. (2) We can obtain wavefields excited at different sources by varying only source locations in the summation formula. (3) We can obtain wavefields excited at different frequencies by varying only frequencies in the summation formula. Numerical experiments indicate that the Gaussian beam summation method yields accurate asymptotic wavefields even at caustics. The new method may be used for seismic modeling and migration.

Generalization of the collision cone approach for motion safety in 3-D environments

Abstract: Avoidance of collision between moving objects in a 3-D environment is fundamental to the problem of planning safe trajectories in dynamic environments. This problem appears in several diverse fields including robotics, air vehicles, underwater vehicles and computer animation. Most of the existing literature on collision prediction assumes objects to be modelled as spheres. While the conservative spherical bounding box is valid in many cases, in many other cases, where objects operate in close proximity, a less conservative approach, that allows objects to be modelled using analytic surfaces that closely mimic the shape of the object, is more desirable. In this paper, a collision cone approach (previously developed only for objects moving on a plane) is used to determine collision between objects, moving in 3-D space, whose shapes can be modelled by general quadric surfaces. Exact collision conditions for such quadric surfaces are obtained and used to derive dynamic inversion based avoidance strategies.

Origin of the R-ion effect on Tc in RBa2Cu3O7.

Abstract: {ital T}{sub {ital c}} and {ital dT}{sub {ital c}}/{ital dP} have been systematically measured for fully oxygenated {ital R}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} ({ital R}-123) with {ital R}=Yb, Tm, Ho, Dy, Gd, Sm, and Nd. {ital T}{sub {ital c}} has been observed to increase from 88 to 94 K with increasing radius of the {ital R} ion ({ital r}) from 0.98 to 1.12 A. Based on the lattice strains and our {ital dT}{sub {ital c}}/{ital dP} data, we have calculated {ital T}{sub {ital c}} for the series of {ital R}-123 and compared them with the measured {ital T}{sub {ital c}}. Good agreement between the experimental and the calculated results strongly suggests that the {ital R} effect on {ital T}{sub {ital c}} in {ital R}-123 originates from the strain-induced charge redistribution between the charge reservoir and the CuO{sub 2} plane.

Estimation Risk, Information, and the Conditional CAPM: Theory and Evidence

Abstract: We theoretically and empirically investigate the role of information on the cross section of stock returns and firms' cost of capital when investors face estimation risk and learn from noisy signals of uncertain quality. The resultant equilibrium is an information-dependent conditional CAPM. We find strong empirical support for the model. Innovations in market volatility, oil prices, exchange rates, and dispersion of analysts' forecasts not only help explain the cross section of stock returns, but their influence depends on the stock's systematic estimation risk. Moreover, dividend and share repurchase initiations have significant downward announcement effects on estimated betas and their standard errors. (JEL D83, D92, E22) How investors process new return-related information and how this information affects equilibrium asset prices is a central issue in finance; it is of substantial interest not only to financial economists seeking to understand the informational efficiency of security prices, but also to investment practitioners who must make investment decisions in the face of continually arriving information. In the textbook capital asset pricing model (CAPM), which assumes that the investment opportunity set is common knowledge, prices simply adjust to new information so as to fall along the new security pricing line. However, this model of information absorption (in security markets) is not satisfactory from