Optical, electrical and thermoelectric power studies of Al-Sb thin film bilayer structure

The III-V semiconductors are of great importance due to their applications in various electro-optic devices. The Al-Sb thin film was deposited on glass substrate by thermal evaporation method at a pressure of 10^-5 torr. The samples were annealed for 3 h at different constant temperatures in a vacuum chamber at a pressure of 10^-5 torr. The electrical resistance vs temperature studies show phase transformation from metallic to semiconducting. The observed positive thermoelectric power indicates that Al-Sb thin films arep-type in nature. The Rutherford back scattering analysis and optical band gap measurements also indicate that the inter-diffusion concentration varies with temperature.     

MOSFET substrate current model for circuit simulation

A simple, accurate MOSFET substrate current model suitable for a circuit simulator is presented. The effect of substrate bias on substrate current is modeled without introducing additional parameters. The accuracy of this model is demonstrated by its ability to fit the experimental data for both standard and LDD devices with average errors of less than 6%. The new model is compared with the substrate current models reported in the literature. In addition, the temperature dependence of the substrate current in the range of 0-120°C is also modeled. The new model has been implemented in a circuit-level hot-electron reliability simulator, and the results obtained from simulation of an inverter circuit are presented     

Design sensitivity analysis of non-linear buckling load

This paper describes three procedures for calculating design derivatives of the non-linear critical load. Constraints on the critical load arise naturally in optimal design of structures having non-linear behavior. The incremental procedures used for non-linear analysis can fail before reaching the final load level due to buckling or collapse of the structure. Therefore, load carrying capability of the structure must be improved before optimal design process can proceed further. This requires design derivatives of the critical load factor. A very simple and effective procedure among the three derived, is selected. It uses most of the information already calculated during analysis and sensitivity analysis of other constraints. Design sensitivity analysis is verified using two known examples. Several other structures are optimized to show effectiveness of the procedure. The sensitivity analysis can be combined with another constraints to optimize structures with more general requirements.This research was initiated under a project sponsored by the National Science Foundations, USA, Grant No. CEE82-13851     

Pressure dependence of burning rate of nitrophenolformaldehyde composite propellants

Polymers of o-, m-, and p-nitrophenols with formaldehyde were used as fuel binders in composite propellants based on NH₄ClO₄ and KClO₄ oxidizers. A study of the burning rate in nitrogen has revealed the occurrence of a breakpoint at about 3–5 atm in the burning rate-pressure curves of all six types of composite propellants that contained nitro-substituted phenolic resins as fuel binders.     

Scheduling in a Semi-Ordered Flow-shop Without Intermediate Queues

The problem of finding a minimum makespan permutation schedule in a deterministic flow-shop without intermediate queues is equivalent to the shortest distance routing traveling salesman problem. If the task system is semi-ordered, the associated distance matrix of the corresponding traveling salesman problem is found to exhibit some peculiar characteristics. Consequently, we are able to derive some important results which help us to eliminate permutations in the search of the minimum makespan permutation schedule. The most important result is that the optimal permutation schedule is pyramidal. An algorithm, having quadratic worst-case complexity in terms of the number of partial schedules explicitly enumerated, has been presented. Some particular cases of the semi-ordered flow-shop are also discussed.     

An investigation of the origin of the main electron trap in GaAs

The origin of the main electron trap (0.83 eV) in GaAs is investigated by creating conditions to favour the formation of Ga-vacancy-oxygen complex in the material. Two specific schemes have been used, (1) Liquid phase epitaxial (LPE) growth of the material at high temperatures (≈1000°C) with oxygen doping and (2) Electron bombardment of LPE material and subsequent annealing. The traps have been characterised by transient capacitance technique. The results show that the main electron trap cannot be produced by either of the schemes thereby implying that a complex involving Ga-vacancy and oxygen may not be responsible for the trap.