Personal computer-basedcamac system for data acquisition

A single board auxiliarycamac crate controller for a Z80-A based personal computer ZX-spectrum to drive thecamac crate housing multipleadc, tdc, dac and 16 I/O ports has been developed. Thecamac crate controller used in this system is of A2 type which supports multiple auxiliary crate controllers. Acamac exerciser/training software for the use ofcamac commands in process control as well as data acquisition has been developed.     

Performance ofesprit in the presence of gain and phase mismatches in sensor doublets

esprit, an acronym for Estimation of Signal Parameters via Rotational Invariance Technique, is a novel method for estimating the Directions of Arrival (doa) of plane waves using an arbitrary array of sensor doublets. However,esprit requires an identical pair of sensors in each doublet, that is the gain and phase characteristics of the sensors in a doublet have to be matched, which may be difficult to ensure in practical situations. In this paper, assuming the sources to be uncorrelated, we analyse the performance ofesprit when the gain and phase characteristics of the sensors in a doublet are not identical. It is shown that the angle estimates are unbiased and expressions are derived for the variance in the estimates ofdoa, when gain and phase mismatches exist in doublets. Computer simulation results are also presented to assert the theoretical predictions.     

X-ray spectroscopy and local structures in glasses

X-ray spectroscopy which is a combination of two techniques, namely x-ray absorption near edge structure (xanes) and extended x-ray absorption fine structure (EXAFS) analyses, is a unique technique for the study of local structures in glasses. Availability of synchrotron radiation sources has made the technique quite attractive and useful because the photon flux from synchrotrons is very intense and polarized. In this article, a brief summary ofxanes andEXAFS techniques is given along with a few applications to the study of local structures in glasses. Communication No. 323 from Solid State and Structural Chemistry Unit.     

Thermal properties of some α-amino acids in aqueous solutions

The thermal properties (thermal conductivity, thermal diffusivity, and volumetric heat capacity) of aqueous solutions of -amino acids [R-CH(NH₂)COOH]—glycine, dl-alanine, l-valine, and dl-leucine, were measured in the temperature range 20–90C using the hot-wire technique. The results show that the values of the thermal properties depend mainly on the amino acid concentration in the medium, the substituted alkyl group of the substances under investigation, and the temperatures. The mechanism of heat transfer is discussed, and the roles of both radiation and convection are taken into consideration.     

Parametric study of the electrical to thermal power conversion in an inductively coupledrf plasma torch

An inductively coupled (ic) radio-frequency (rf) stabilized argon plasma was generated in a quartz tube using a 7 MHzrf generator. The electrical and thermal powers were measured and the efficiency of energy conversion was computed. The results indicate that for a constant power input, there is an optimum argon flow rate for which maximum energy conversion efficiency occurs.     

Thetranair rectangular grid approach to solving the nonlinear full-potential equation about complex configurations

This paper describestranair, a numerical method that uses a rectangular grid to solve the nonlinear full-potential equation about general complex configurations. The grid is locally refined to resolve the high velocity gradients arising from leading edge expansions or shock waves. The grid penetrates the boundary (described by networks of quadrilateral panels) and is generated automatically. Discrete operators are constructed using the finite element method. The system of nonlinear discrete equations is solved iteratively using an orthogonal conjugate gradient method preconditioned by an exterior Poisson solver and a direct sparse solver. The primary emphasis of this work is to provide design engineers with an aerodynamics analysis tool (thetranair code) which is as accurate, reliable, economical, and flexible to use as panel methods. Results obtained by usingtranair to analyse several interesting configurations are presented. This work was supported in part bynasa (Contractnas2-12513) and theirad funds of The Boeing Company.     

Semiconductor based photoelectrochemical cells for solar energy conversion—An overview

An overview of the semiconductor based photoelectrochemical (pec) cells for solar energy conversion is presented.pec cells are of two types: photoelectrolysis cells and photovoltaic cells. The principles involved, electrode and electrode/electrolyte interface characteristics, experimental methods of investigation and energy conversion efficiency are discussed in detail. Up-to-date data on variouspec cells are also presented and discussed.     

Infrared absorption in spinel ferrites

Their spectra of a number of ferrites, MFe₂O₄, M(Mn, Fe, Co, Ni, Cu and Zn) have been studied at room temperature in the range 200–1000 cm⁻¹. In all the cases the spectrum consists of four bands, two of which have strong absorption while the other two have weak absorption and often appear as shoulders on the main band. However up to 20% of the inverse ferrite, the shoulder in the low energy side appears as a band. In this paper we have analysed the origin of the above bands.     

Recent advances in open cycle MHD electrical power generation

The report attempts to summarise the recent developments in the field ofmhd electric power generation and identify the problem areas needing further R and D efforts to achieve commercial acceptance of the process. During the last two decades there has been active interest in the development of this technology. A large volume of literature is available in published form, apart from the unpublished information of commercial value. Judging from this standpoint this report cannot be considered exhaustive. Nevertheless it integrates the scattered information in a condensed volume which would be useful in extrapolating the future trends of development while assessing the present status of the technology. To make this report self-contained and complete, the fundamental principles ofmhd power generation have also been included. Themhd project in India is fully sponsored by the Department of Science and Technology under whose auspices this report has been prepared.     

Study of a complex water resources system with screening and simulation models

The study describes a sequential iterative modelling process for a complex water resource system. Two types of analytical models are used to find a reasonably small set of possible systems optimal design alternatives for a complex river basin. These models are a linear programming deterministic continuous (lpdc) model and a linear programing deterministic discontinous (lpdd) model. Linear programing has been used with linear approximation of the nonlinear functions. A simulation program has been developed which continues screening on the basis of the information obtained from the linear programing model. The models are developed in the context of analysis of the Narmada river, a large river basin in India, for which in the first instance alternative combinations and capacities of six major dams have to be decided.     

Chemical amplification — A novel approach to ultratrace analysis

The lowest concentration that can be estimated with 100% error in chemical analysis by instrumental technique is referred to as detection limit. It is equal to the ratio of twice the background signal to the magnitude of analytical signal corresponding to a concentration of unity. Detection limit (dl) could be improved if the analytical signal alone could be selectively amplified without affecting the background. It is shown that this could be achieved by chemical amplification. Atomic amplification of two or three orders of magnitude could be obtained by combining two chemical amplifications in series. It is demonstrated that by using heteropoly acid formation as the first amplification reaction and determining molybdenum in the heteropoly acid by catalyticdc polarographic wave, a detection limit for the hetero atom of less than a ppb can be obtained. It is pointed out that the approach of selectively amplifying analytical signals by tandem chemical amplification reactions makes it possible to perform ultratrace analysis (ppb level) with classical instrumental analytical techniques which havedl at ppm level.     

Elastic properties of As-Sb-Se glasses

Results of measurement of elastic modulii on As-Sb-Se glasses are reported and their composition dependence discussed. The Young’s and the shear modulii lie in the range of 170–210 and 65–80 kb respectively. These values are typical of chalcogenide glasses. For (As, Sb)₄₀Se₆₀ glasses, the modulii increase monotonically with increasing Sb₂Se₃ content. The observed composition dependence of the modulii for the As _x Sb₁₅Se_{85 −x} glasses is examined in terms of the chemically ordered structural units in the glasses.     

Radiation-induced modification of polyurethane with hydroxyethyl methacrylate: blood compatibility

An attempt is made to develop the hydrophilic grafting of polyether urethane urea with hydroxyethyl methacrylate (hema) using⁶⁰Coγ-irradiation for achieving optimum hydrophilic/hydrophobic property needed towards blood compatibility. Contact angle method and platelet adhesion from calf’s blood are used to determine the suitability of these modified surfaces.     

On the mechanism of pairing in thebcs theory

An explanation has been offered for the mechanism of cooper pairing in thebcs theory of superconductivity on the basis of the relativistic Darwin interaction. The theory leads to an expression for critical temperature which depends on a few atomic parameters. Calculated values ofT _c for elements and alloys are in good agreement with experiment.     

Applications of scanning transmission electron microscope microanalysis in the study of materials

The dedicatedstem equipped with field emission electron source, affords opportunities for the acquisition of microchemical and microstructural data on a scale approaching the nanometer level. In this presentation, a number of applications of microchemical analysis and microdiffraction to engineering materials will be discussed, with major emphasis on high-strength low-alloy steels, steels for high formability in automotive applications, and aluminium alloys. Some advantages and limitations of the technique are noted, especially for application to analysis of electrochemically prepared thin foils, and to the analysis of extracted particles.     

International issues in remote sensing

Starting with the initial aim of reconnaissance technical developments in remote sensing have progressed sufficiently for the large-scale realisation of practical benefits. During the eighties a number of countries will have remote sensing satellite systems in operation. There are however a few technical, legal, political and economic issues that still remain unresolved. The resolution of these issues would facilitate practical applications especially in developing countries. Apart from the purely technical and economic issues such as the ability to compare data from two different satellites, the cost of the data etc one of the major hurdles in the application of this technology is the establishment of an international regime governing the activities of states in remote sensing. This is particularly important in view of the link between surveillance and remote sensing. Even though discussions have been going on for quite some time at the United Nations, the prospects of reaching agreement remain bleak. The main problems precluding agreement are national security, commercial and sovereignty concerns of the developed and developing countries. The key issues relate to the right of countries to conduct remote sensing over other countries, the right of countries collecting remote sensing data (over other countries) to distribute this data freely and the modalities of how the “sensitivity” aspects of remote sensing for surveillance and economic espionage can be reconciled with a legal regime that emphasises international cooperation. A critical analysis of existing international space law seems to indicate that there are two kinds of remote sensing—passive and active. In passive remote sensing the satellite sensor detects the sun-reflected or self-emitted radiation from objects on the ground. In active remote sensing a pulse of electromagnetic radiation is transmited from the satellite and its reflectance or scattering by objects on the earth’s surface is measured. A strict reading of existing legal principles on space seem to imply that passive sensing is legal while active sensing could be interpreted as violating the sovereignty of the sensed state. Agreement on remote sensing can be reached if a resolution or a range of resolutions can be defined to discriminate between “sensitive” and “non-sensitive” data. The only international agreement in this area between the USSR and a group of nine socialist countries uses a resolution limit of 50m. Available information on the subject seems to indicate that the range is from 25–50 m. One other aspect dealt with relates to the use of satellite data for verification of arms control measures, for crisis monitoring and the prospects of setting up an International Satellite Monitoring Agency (ISMA). It appears that the huge expense that this would entail would be justified only if theISMA can monitor the superpowers and the arms race between them.     

Advances in the acoustics of flow ducts and mufflers

This review paper deals with advances made in the last two decades in the acoustics of flow ducts for heating, ventilation and air-conditioning (hvac) systems and engine mufflers. The context, concepts, methods used and results have been highlighted. Frequency-domain one-dimensional analysis of reflective mufflers has been emphasized because of its basic importance and wide application. Finally, problems needing further research have been identified.     

Fuzzy medial axis transformation (fmat): Image representation,skeleton extraction and uncertainty management in computer vision

The problem of extraction of medial axis transformation of a gray image with reference to skeletonization, image representation and uncertainty management in a vision system has been addressed. The Fuzzy Medial Axis Transformation (fmat) of a fuzzy setf is a set of fuzzy disks whose sup isf. Unfortunately, specifying thefmat sometimes requires more storage space than specifyingf itself. The present paper describes some techniques to improve the compact representation offmat; thereby making it practically useful to an image for its skeleton extraction and compact representation, for shape analysis and template matching, for representation and retrieval, for uncertainty management in recognition and for creating new images of various poses. The algorithms involve reduction of redundancy infmat, its approximation, and reduction of the searching spaces for its computation. Computational aspects for the convenience of writing an efficient program have been described. Some applications of thefmat have also been mentioned. This work was done while SKP held annrc-nasa Senior Research Associateship at the Lyndon B Johnson Space Center, Houston, Texas.     

Utilising high throughput technologies for the determination of the reaction network of the <Emphasis Type="SmallCaps">l</Emphasis>-proline catalysed aldol reaction

The objective of this work is to facilitate the determination of a reliable reaction network for the l-proline catalysed aldol reaction using high throughput technologies (HTT). The availability of reliable reaction network is fundamental to predictive kinetic modelling including scale up, replacing a batch process with a continuous one, optimisation, thermal safety, process simulation, etc. The extent to which HTT experiments may be used to provide the necessary quantitative understanding of both physical and chemical phenomena of the system studied is assessed through a four stage development programme. For this particular system it is shown that, in conjunction with appropriate experimental designs, meaningful data streams for mechanistic/kinetic studies can be generated. The experimental data allowed a reaction network for the l-proline catalysed aldol reaction to be proposed and verified through a kinetic modelling exercise.

Integrated optoelectronics for optical interconnections and optical processing

Integrated optoelectronics using III–V compound semiconductor technology has so far shown exciting advances for application in optical telecommunication systems. New applications of this technology are in optical interconnections and signal processing systems. The technology is expected to be very effective in solving the wiring limit in data transmission within electronic systems, using the advantages of optical techniques such as high data transmission rate and high parallelism, and thus improve the performance of overall systems. Optical interconnection devices currently being developed aim both at multiplexing vast amounts of data and exhibiting flexible interconnection functions using the advantageous characteristics of light. Future research is expected to explore new techniques such as that for multiplexing and processing data in the wavelength division as well as for integrating functional devices in two-dimensions. Synergetic collaboration among materials and processing, design and fabrication, and packaging areas is extremely important and this will lead to practical optical interconnections and signal processing systems.