The Effects of Process Variables on the Case Depth of Laser Transformation Hardened AISI 01 Tool Steel Specimens

An investigation was carried out to study the effects of speed, nozzle gap and power input on the case depth of laser transformation hardened ASSAB DF2 (equivalent to AISI 01) tool steel specimens. The specimens, used were 5 and 10 mm thick and 10 and 25 mm in diameter. A defocussed beam from a fast axial flow C0₂ laser was used with continuous-wave power inputs of 0.4 to 0.6 kW. The traversing speeds used were 5, 10 and 15 mm/s. The nozzle gaps were 5, 10 and 15 mm which gave calculated beam diameters of 0.129, 1.174 and 2.276 mm respectively. It is found that, the case depth increases as either the specimen thickness or power input is increased, but decreases as the: traversing speed is increased. The beam diameter, however, does not seem to have a significant influence on the case depth.     

Robust regulation for nonlinear systems with gain-boundeduncertainties

In this paper we study the problem of robust output regulation for a nonlinear system in the presence of gain-bounded perturbations. The problem in question is approached as a problem of robustly stabilizing, in the presence of gain-bounded uncertainties, a suitable “augmented” plant in which the regulated output drives an appropriate “internal model” of the exosystem. Robust stabilization of the latter is achieved, in turn, by solving an appropriate problem of suboptimal disturbance attenuation     

On the controllability of a class of discrete bilinear systems

The subject of this paper is the controllability of a class of time invariant discrete bilinear systems. Bilinear systems are classified into two categories: homogeneous and inhomogeneous. Necessity as well as the sufficiency results are obtained by means of decomposing the bilinear system into a linear system and a multiplicative feedback. Byproducts of the decomposition are the notions of multiplicative feedback compensation and the multiplicative feedback with bias compensation which may prove to be alternatives for the classical linear feedback compensation.     

A Hamiltonian state space approach to anisotropic elasticity and piezoelasticity

We present a Hamiltonian state space approach for problems of anisotropic elasticity and piezoelasticity. By means of Legendre’s transformation, the basic equations of piezoelasticity are formulated into a state equation and an output equation in terms of the state vector that comprises the generalized displacement vector and the conjugate generalized traction vector as the dual variables. The Hamiltonian features and symplectic orthogonality of the system, which are essential for the solution approach using eigenfunction expansion, are delineated at length. We show that the solution to 3D problems of a prismatic body hinges upon a 2D Hamiltonian eigensystem and the eigensolution associated with the zero eigenvalue leads to the solution to the generalized plane problem naturally. Based on the formalism, the solution to a problem of piezoelasticity is no more difficult than its elastic counterpart.     

Setting the Public Fear Agenda: A Longitudinal Analysis of Network TV Crime Reporting, Public Perceptions of Crime, and FBI Crime Statistics

Public perceptions of crime as the most important problem (MIP) facing the country jumped tenfold, from 5% in March of 1992 to an unprecedented 52% in August of 1994. This study analyzed the effects of three network television news predictor variables and two FBI predictor variables to determine what statistically accounted for this "big scare". Based upon data from 1978 through 1998, results suggest that the 1994 "big scare" was more a network TV news scare than a scare based upon the real world of crime. The television news variables alone accounted for almost four times more variance in public perceptions of crime as the MIP than did actual crime rates.     

Managing Legal Issues in the Software Development Life Cycle

Technology today is being misused to propagate copyright violations. the need for awareness becomes critical when the software developer can be held directly liable for creating devices that might be used to circumvent copyright protection technology. Current software development life cycles do not take legal issues into consideration during the development of potentially controversial products. This may result in legal complications if the laws have changed by the time the product is released. This article presents a proactive method of handling legal issues. Modifications are suggested to the existing development life cycles, which can be used to ensure compliance with current legal standards. Legal reviews create a built-in resilience buffer in the product that result in a finished product better compliant with current standards and standards that can be set in the future. This avoids liability and legal issues that might arise by following the traditional approach. A cost-benefit analysis is performed that indicates the benefit of using the suggested modifications.     

A hybrid switching control strategy for nonlinear and underactuated mechanical systems

This note presents a hybrid switching control strategy for nonlinear and underactuated mechanical systems. Sufficient conditions for constructing the hybrid switching control, stability proof, and experimental results for using the hybrid switching control are given.