Algorithms for a class of computer-aided design problems: A review

This paper reviews some recent results on algorithms for a class of computer aided design problems arising in control, circuit theory and steel structure design.     

Spectral tuning and linewidth narrowing of shallow-junction surface emitting GaAs LED́s through γ-ray irradiation

Alterations of device characteristics as a result of γ-ray irradiation of shallow-junction surface emitting devices are different from those of deep-junction devices with respect to LED emission intensity reduction, I-V curve, line shape, and spectral shift. In particular, much larger spectral shifts in the opposite direction-toward longer wavelengths-are reported here than those found in the literature for deep-junction devices. A qualitative model based upon photochemical doping and changes in surface band bending is proposed to explain these phenomena. Changes in surface emitting shallow-junction optical radiation source device characteristics brought about by γ-ray irradiation are desirable ones for utilization in most optical fiber communication systems. These changes include linewidth narrowing, decreased time response, and decreased material dispersion because of the emission wavelength change.     

Nondifferentiable optimization algorithm for designing control systems having singular value inequalities

It has been known for some time that many control system design requirements can be expressed as differentiable inequalities. More recently, it has been shown that important structural properties such as robustness and low noise sensitivity can be expressed as nondifferentiable inequalities involving the singular values of a system or return difference transfer function matrix. This paper presents an optimization algorithm which permits all these constraints to be considered.     

Singular perturbation theory and its application to the computation of electromagnetic fields

In the past decade the theory of singular perturbations has been well-established. The techniques developed to solve singular perturbation problems were succesfully applied to practical problems. In this paper we will give a brief survey of singular perturbation theory and discuss a possible application to the computation of electromagnetic fields.     

Synthol reactor technology development

Since Sasol introduced the Kellogg designed circulating fluidized bed (CFB) reactors at Sasol 1 in the 1950s, the commercial high-temperature Fischer–Tropsch (HTFT) process has had a dynamic ongoing development resulting, recently, in the introduction of Sasol advanced synthol (SAS) reactor operation only at Secunda, 1999. It has reached a stage now where the emphasis has shifted for developing a catalyst tailored to these reactors and current market requirements. This paper follows the development of the reactor technology since the early 1940s, highlighting the major developments and giving indications of the effect thereof on gas throughput and bulk product yields. The paper traces Sasol’s journey utilizing the sound, but unproven pilot plant scale-up of Kellogg, to a routine day to day operation and profitable commercial process by means of innovative design changes, general state-of-the-art advances and, importantly, experience!     

Computer-aided design via optimization: A review

Many design problems, including control design problems, involve infinite dimensional constraints of the form φ(z, α) ≤ 0 for all α ? $\text{A}$, where α denotes time or frequency or a parameter vector. In other design problems, tuning or trimming of certain parameters, after manufacture of the system, is permitted; the corresponding constraint is that for each α in $\text{A}$ there exists a value τ (of the tuning parameter) in a permissible set T such that φ(z, α, t) < 0. Recent algorithms for solving design problems having such constraints are summarized.