Developing CAD techniques for preliminary architectural design

Theoretically the computer can offer the architect significant help during the preliminary design stages. To take full benefit of its capabilities it is necessary to use the computer for the design process itself. To this end, a program has been written that concentrates on ease of use so that the machine does not impede the creative process. The program works through the manipulation of design elements such as spaces and windows, not graphical ones. The result is a tool which offers improved efficiency, but is very different from current methods that use paper in preliminary design.     

Application of the MOSFET device structure in characterizing imperfection centers in indium-doped silicon

C.T. Sah has published a review article demonstrating the application of high-frequency small signal capacitance and current transients of a space charge layer. Application of such transients is a powerful technique in characterizing deep level imperfection center concentrations, energy levels, thermal and optical emission rates and thermal capture cross sections. The MOSFET device structure is particularly convenient for low temperature measurements of shallow levels where deionization occurs and the substrate becomes highly resistive, seriously limiting capacitance transient techniques. Examples are given by results on indium-doped silicon, such as employed in extrinsic IR detectors. The emission time constant of holes from the neutral indium center has been found to depend on the indium doping. Measurements on lightly doped samples yield a value for the emission rate, $\text{1}\text{e}{}_{\mathrm{p}}$, of 6.0 msec at 77°K and a thermal activation energy of 0.15 eV. Measurements on heavily doped samples yield values of $\text{1}\text{e}{}_{\mathrm{p}}$ of 20 μsec at 77°K and an activation energy of 0.117 eV. These results are consistent with the Poole-Frenkel effect describing field enhanced thermal emission of holes from the indium center. Measurements of the hole capture coefficient at 77°K yield values for c_p of 3.7 × 10^?7 cm³/sec. These measurements have been made on heavily doped samples. The capture coefficient measured is the zero field or quasi-equilibrium value. The temperature dependence of the hole capture coefficient has been found to be T^?4. Small transients in the thermal emission rate measurements have been observed. These transients have thermal activation energies of around 0.08 eV and are associated with the 0.11 eV level as reported by Hughes Research Labs after accounting for barrier lowering by the Poole-Frenkel effect.     

Low overvoltage electrocatalysts for hydrogen evolving electrodes

An electrocatalyst for hydrogen evolving cathodes has been developed for use in alkaline media. The materials employed in manufacturing the coating are relatively cheap transition metals. The results of a variety of performance tests are reported. The electrodes exhibit a low overvoltage for hydrogen evolution (70–90 mV at 70°C and 1A cm^?2 in 5 N KOH), stability to abuse (e.g. current interruption or reversal) and a long cathode life under operating conditions.     

The Determination of Low-Level Water in Transdermal Dosage Forms as Tyvek Laminates with an Evaporator Oven

An assay of water in adhesive monolithic transdermal drug dosage forms ('patches'), using lamination to Tyvek, and gaseous extraction in an evaporator oven into a Karl Fischer titrator, is described. The method is simple, linear, accurate, specific and more sensitive than alternatives.     

Modeling and analysis of effective ways for improving the reliability of second-hand products sold with warranty

Often, customers are uncertain about the performance and durability of the used/second-hand products. The warranties play an important role in reassuring the buyer. Offering the warranty implies that the dealer incurs additional costs to service any claims made by the customers. Reducing warranty costs is an issue of great interest to dealers. One way of improving the reliability and reducing the warranty servicing cost for second-hand items is through actions such as overhaul and upgrade which are carried out by the dealer or a third party. Improving actions allow the dealer to offer better warranty terms and to sell the item at a higher price. This paper deals with two effective approaches (virtual age approach and screening test approach) to decide on the reliability improvement strategies for second-hand products sold under various warranty policies (failure-free, rebate warranty, and a combination of free replacement and lump sum). A numerical example illustrates that from a dealer’s point of view, it is beneficial to carry out an improvement action only if the reduction in the warranty servicing cost is greater than the extra cost incurred due to this improvement action.     

Behaviour of welded top-seat angle connections exposed to fire

Beam-to-column connections have been found to significantly influence the structural behaviour at ambient and elevated temperatures. When steel-framed structures are exposed to fire, the load-bearing capacity is decreased and the behaviour of the joints is of particular concern. To account for the extensive applications of welded connections, eight experimental tests were carried out in this study on two different types of beam-to-column angle connections to investigate their fire resistance capacity. Failure characteristics and fracture modes of specimens were studied, and results are presented in the form of temperature–rotation curves. In addition, the influence of different parameters such as thickness of the angles, the value of the applied moment, and other geometrical and mechanical characteristics of the connections was investigated.     

Electrochemical Formation of Polypyrrole-carboxymethylcellulose Conducting Polymer Composite Films

1.IntroductionConjugated polymers such as polypyrrole(PPY),polyaniline,polythiophene and polyphenylene etc.whichexhibit significant level of electrical conductivity andhence are termed as conducting polymers,have gotversatile promising applications in the field of energystorage[1],sensors[2],electronic and optical devices[3]andso on.Many researches have been conducted to pro-duce composites or blends of conducting polymer filmswith some insulating polymers in order to overcome thedrawbacks su…     

Precise Tip Positioning of a Flexible Manipulator Using Resonant Control

A single-link flexible manipulator is fabricated to represent a typical flexible robotic arm. This flexible manipulator is modeled as an SIMO system with the motor torque as the input and the hub angle and the tip position as the outputs. The two transfer functions are identified using a frequency-domain system identification method, and the resonant modes are determined. A feedback loop around the hub angle response with a resonant controller is designed to damp the resonant modes. A high-gain integral controller is also implemented to achieve zero steady-state error in the tip position response. Experiments are performed to demonstrate the effectiveness of the proposed control scheme.     

Current scenario and potential of biodiesel production from waste cooking oil in Pakistan: An overview

Biodiesel utilization has been rapidly growing worldwide as the prime alternative to petrodiesel due to a global rise in diesel fuel demand along with hazardous emissions during its thermochemical conversion. Although, several debatable issues including feedstock availability and price, fuel and food competition, changes in land use and greenhouse gas emission have been raised by using edible as well as inedible feedstocks for the production of biodiesel. However, non-crop feedstocks could be a promising alternative. In this article, waste cooking oils have been recommended as a suitable option for biodiesel production bearing in mind the current national situation. The important factors such as the quantity of waste cooking oil produced, crude oil and vegetable oil import expenses, high-speed diesel imports, waste management issues and environmental hazards are considered. Moreover, process simulation and operating cost evaluation of an acid catalyzed biodiesel production unit are also conducted. The simulation results show that the production cost of waste cooking oil-based biodiesel is about 0.66USD·L^-1. We believe that the present overview would open new pathways and ideas for the development of biofuels from waste to energy approach in Pakistan.