Search results

Summarizes previous research on financial analysts’ forecasts and the segmentation of international finance markets. Hypothesizes that the accuracy of earnings forecasts in a country is negatively related to the country return, and positively to the country risk. Uses 1992‐94 data from 12 countries to test this, supports the hypothesis and calls for further research.

The numerical solution of problems involving two‐dimensional flow in an infinite or a semi‐infinite channel is considered. Beyond a certain finite region, where the flow and geometry may be general, a “tail” region is assumed where the flow is potential and the channel is uniform. This situation is typical in many cases of fluid‐structure interaction and flow around obstacles in a channel. The unbounded domain is truncated by means of an artificial boundary B, which separates between the finite computational domain and the “tail.” On B, special boundary conditions are devised. In the finite computational domain, the problem is solved using a finite element scheme. Both non‐local and local artificial boundary conditions are considered on B, and their performance is compared via numerical examples.

A numerical procedure is devised for the thermal analysis of three‐dimensional large truss‐type space structures exposed to solar radiation. Truss members made of an orthotropic material with a closed thin‐walled cross‐section of arbitrary shape are considered. Three‐dimensional thermal effects are taken into account in the analysis. In the proposed method, the governing equations are first put into a weak form. Then the Galerkin finite element method is applied with respect to the axial coordinate of each truss member. The circumferential variation of the temperature is treated by a symbolically‐coded harmonic balance procedure. The interaction between the various truss members is controlled by an iterative scheme. As a numerical example which demonstrates the proposed method, the temperature distribution in a parabolic dish structure is found. The results are compared to those obtained by standard one‐ and two‐dimensional analyses.

The optimal control of the steady‐state temperature distribution in radiating panels using control heat sources is considered. The problem has important applications in the thermal control of space structures. A mathematical model leads to an elliptic nonlinear optimal control problem. A numerical optimal control method, based on finite element (FE) discretization and sequential quadratic programming (SQP), is employed. Results are presented for some specific examples.

The Kirchhoff transformation, in conjunction with the finite element method, is proposed as a tool in solving non‐linear heat conduction problems. A very simple way to obtain the inverse Kirchhoff transformation is shown, using the contour lines of the Kirchhoff variable obtained from a finite element analysis.

The interaction of a global model (GM) and a local (regional) model (LM) of heat flow is considered under the framework of so‐called “one‐way nesting”. In this framework, the GM is constructed in a large domain with coarse discretization in space and time, while the LM is set in a small subdomain with fine discretization.

The GM is solved first, and its results are then used via some boundary transfer operator (BTO) on the GM–LM interface in order to solve the LM. Past experience in various fields of application has shown that one has to be careful in the choice of BTO to be used on the GM–LM interface, since this choice affects both the stability and accuracy of the computational scheme. Here the problem is first theoretically analyzed for the linear heat equation, and stable BTOs are identified. Then numerical experiments are performed with one‐way nesting in a two‐dimensional channel for heat flow with and without radiation emission and linear reaction, using four different BTOs.

Among other conclusions, it is shown that the “negative Robin” BTO is unstable, whereas the Dirichlet, Neumann and “positive Robin” BTO are all stable. It is also shown that in terms of accuracy, the Neumann and “positive Robin” BTOs should be preferred over the Dirichlet BTO.

This study may be the first step in analyzing BTO accuracy and stability for more general atmospheric systems.

The purpose of this paper is to propose a computational model for thin layers, for problems of linear time-dependent heat conduction. The thin layer is replaced by a zero-thickness interface. The advantage of the new model is that it saves the need to construct and use a fine mesh inside the layer and in regions adjacent to it, and thus leads to a reduction in the computational effort associated with implicit or explicit finite element schemes.

Special asymptotic models have been proposed for linear heat transfer and linear elasticity, to handle thin layers. In these models the thin layer is replaced by an interface with zero thickness, and specific jump conditions are imposed on this interface in order to represent the special effect of the layer. One such asymptotic interface model is the first-order Bövik-Benveniste model. In a paper by Sussmann et al., this model was incorporated in a FE formulation for linear steady-state heat conduction problems, and was shown to yield an accurate and efficient computational scheme. Here, this work is extended to the time-dependent case.

As shown here, and demonstrated by numerical examples, the new model offers a cost-effective way of handling thin layers in linear time-dependent heat conduction problems. The hybrid asymptotic-FE scheme can be used with either implicit or explicit time stepping. Since the formulation can easily be symmetrized by one of several techniques, the lack of self-adjointness of the original formulation does not hinder an accurate and efficient solution.

Most of the literature on asymptotic models for thin layers, replacing the layer by an interface, is analytic in nature. The proposed model is presented in a computational context, fitting naturally into a finite element framework, with both implicit and explicit time stepping, while saving the need for expensive mesh construction inside the layer and in its vicinity.

The paper aims to argue that stock‐based compensation for top leaders is a very recent phenomenon that is associated with lower shareholder returns, bubbles and crashes and huge corporate scandals and that it is time to bring an end to it and find a better, more authentic approach that will enable corporations, stakeholders and the financial community to thrive.

The paper details how many executives engage in a dangerous and little‐discussed practice that comes very close to the line of illegality, one that betrays the spirit of securities laws and accounting regulation: earnings management. It concludes that far too many corporate leaders are now using their talents and corporate resources to smooth earnings, and bump up the stock price, rather than to build their companies.

The paper proposes that corporations find a way to restore the focus of the executive on the real market and on an authentic life by eliminating the use of stock‐based compensation as an incentive.

The author's remedy: top executives should be prevented from selling any stock – for any reason – while serving as a corporate leader, and indeed for several years after leaving their post.

The author calls for an end to stock‐based compensation because it is associated with lower shareholder returns, bubbles and crashes and huge corporate scandals.

Describes a new finite element scheme for the large‐scale analysis of compressible and incompressible viscous flows. The scheme is based on a combined compressible‐ incompressible Galerkin least‐squares (GLS) space‐time variational formulation. Three‐ dimensional unstructured meshes are employed, with piecewise‐constant temporal interpolation, local time‐stepping for steady flows, and linear continuous spatial interpolation in all the variables. The scheme incorporates automatic adaptive mesh refinement, with a choice of various error indicators. It is implemented on a distributed‐memory parallel computer, and includes an automatic load‐balancing procedure. Demonstrates the ability to solve both compressible and incompressible viscous flow problems using the parallel adaptive framework via numerical examples. These include Mach 3 flow over a flat plate, and a divergence‐free buoyancy‐driven flow in a cavity. The latter is a model for the steady melt flow in a Czochralski crystal growth process.