Better to be Lucky Than Good

This paper describes various factors that are to be considered in selecting a variable speed drive and a steam turbine for any process equipment. To better illustrate the process of selecting a drive from both VFD and turbine options, two example cases were created that represented actual applications already installed and operating. The specific applications are a boiler feedwater pump (BFW) and an FD fan. It is necessary to consider and include all the costs for either type of drive system. The VFD and motor costs were obvious but the existing surplus distribution and transformer capacity, had it not been available, would have altered the economics considerably. Similarly, the cost of steam piping and lube oil supply, cooling, and filtration, which was available at the BFW pump but not at the FD fan, was not discussed but could have had significant cost impact.     

A distributed location system for the active office

Distributed systems for locating people and equipment will be at the heart of tomorrow's active offices. Computer and communications systems continue to proliferate in the office and home. Systems are varied and complex, involving wireless networks and mobile computers. However, systems are underused because the choices of control mechanisms and application interfaces are too diverse. It is therefore pertinent to consider which mechanisms might allow the user to manipulate systems in simple and ubiquitous ways, and how computers can be made more aware of the facilities in their surroundings. Knowledge of the location of people and equipment within an organization is such a mechanism. Annotating a resource database with location information allows location-based heuristics for control and interaction to be constructed. This approach is particularly attractive because location techniques can be devised that are physically unobtrusive and do not rely on explicit user action. The article describes the technology of a system for locating people and equipment, and the design of a distributed system service supporting access to that information. The application interfaces made possible by or that benefit from this facility are presented     

Coalescence of Two Viscous Cylinders by Capillarity: Part I, Theory

The creeping plane flow of two viscous cylinders coalescing under the influence of surface tension is described theoretically in a series of three articles. Part I is a theoretical overview. The physical assumptions affecting applicability of the theory are discussed. The shape as a function of time and of the initial diameter ratio D ≥ 1 is given in parametric form. For D = 1 and D ∞, the shape sequences are known exactly; for finite D > 1, a first-order differential equation is solved numerically. The time requires a quadrature. This is accurate, and easier than solving the fluid-dynamical field equations. The theory encompasses time-dependent liquid properties.     

Low-density microcellular carbon foams

A method has been developed to produce vitreous carbon foams having both low densities (0.03 to 0.10gcm^–3) and small cell sizes ( 20 m). This process involves the replication of a porous sacrificial substrate, i.e. sodium chloride. The salt is pressed initially into bars and sintered to give a structure with continuous porosity. The pores are infused with a phenolic solution, the solvent is evaporated, and the resin is pyrolysed within the salt substrate. Extraction of the salt and freeze drying lead to the final carbon foam. The substrate serves two purposes in this process: (1) it prevents shrinkage of the foam during pyrolysis, and (2) it dictates the cell size of the foam.     

A Review of the Application of Meta-Heuristic Algorithms to 2D Strip Packing Problems

This paper is a review of the approachesdeveloped to solve 2D packing problems withmeta-heuristic algorithms. As packing tasks arecombinatorial problems with very large searchspaces, the recent literature encourages theuse of meta-heuristic search methods, inparticular genetic algorithms. The objective ofthis paper is to present and categorise thesolution approaches in the literature for 2Dregular and irregular strip packing problems.The focus is hereby on the analysis of themethods involving genetic algorithms. Anoverview of the methods applying othermeta-heuristic algorithms including simulatedannealing, tabu search, and artificial neuralnetworks is also given.     

Physical limitation of the cascoded snapback NMOS ESD protection capability due to the non-uniform turn-off

The nonlinear effects and physical failure mechanism in over-voltage protection NMOS snapback structures during ESD operation have been analyzed with the use of experimental test structures as well as process and device simulations. A phenomenological explanation has been provided to account for the effect due to substrate type and the use of a so-called ESD implant. A generic design solution for the cascoded snapback NMOS structure suitable for 5-V tolerant I/O applications is proposed, one that delivers robust operation and eliminates the requirement for an additional ESD implant.     

Selection of process parameters for mass plating of discrete electronic components

The miniaturisation of electronic components coupled with requirements for high temperature lead-free soldering has forced the improvement of the termination finish of surface mount components to meet the critical demands of the electronic industry. In the present work the processing parameters necessary to plate miniature multilayer varistors (MLVs) with nickel and tin layers have been explored. The tooling selected was a ‘rotary flow-thru’ plater which achieved high volume plating with <0·5% rejects. The anode selection proved critical and Nickel S rounds only were suitable with the chosen parameters. A very tight plating distribution with nickel thickness average 2·2 µm (±0·28 µm) and tin thickness average 3·5 µm (±0·31 µm) was achievable in production size quantities. An evaluation of product by examining solder fillet heights and tombstoning in mass board mounting trials concluded that the nickel tin finish is effective for high speed soldering applications.     

Effect of transparency within a semiconductor on emissivity mapping for thermal profile measurements of a semiconductor device

The paper reports on infra-red (IR) measurements made on silicon and gallium arsenide substrates which are transparent to IR radiation. The work showed that the measured emissivity is dependent on the wafer back-face technology, for example, a gold heat-sink or epoxy attachment. The work also indicated that the measured emissivity for the thermal mapping of a device is a function of the emitted radiation from the front, back face and layer interfaces, as well as internally reflected radiation and will be dependent on the thickness of the semiconductor wafer. Experimental work has shown that the two-temperature emissivity correction method will give a very accurate value of the total surface emissivity received from the sample