An Indo-Soviet experiment on anmhd generator test section at the Soviet U-02 facility

This paper summarizes the major results of the joint Indo-Soviet experiment for testing the Indianmhd generator channel section, designed and fabricated at the Bhabha Atomic Research Centre, Bombay, which was carried out at the U-02 facility in Moscow, USSR, in May 1980. The total test duration was 65 hours and included electrophysical tests and life tests under applied electric fields. The main purpose of the tests was to substantiate the physical concepts, computer codes, design features and special processing techniques involved in the development ofmhd generators for the Indian pilot plant at Tiruchirapalli. The experimental observations on the phenomena of heat transfer to the walls, gas dynamics in the channel, electrical characteristics of the generator and near-electrode processes including the analysis of arc spots correlate with the theoretical estimates based on present understanding of the physical processes occuring in similarmhd generators. The post-operational inspection of the channel section and extensive investigation of materials through microscopic analysis, chemical analysis and x-ray analysis are also reported in this paper. The joint test programme has clearly demonstrated the definite operating capability of the test section and has given sufficient information and encouragement for building better and improved channels for the future.     

Interaction of kunjin virus with octyl-D-glucoside extracted Vero cell plasma membrane

Initial experiments using whole cells have shown that there were specific and saturable interactions between kunjin (KUN) virus and receptor molecules on the Vero cell surfaces. Solubilisation of Vero cell plasma membranes with octyl-D-glucoside (OG) yielded an extract which also interacted specifically with KUN virus. This was proven using electron microscopy. When the virus-OG-extract complex was exposed onto Vero cell monolayers, no KUN virus was observed to enter into the whole cells. This would imply that there was virus-receptor interaction with the OG-extract leaving no free virus to attach to the whole cells. The attachment kinetics of KUN virus was studied further using the Scatchard analysis which indicated the involvement of more than one interactive macromolecule in the attachment event.     

Schottky barrier diodes for millimeter wave detection in a foundry CMOS process

CoSi/sub 2/-Si Schottky barrier diodes on an n-well and on a p-well/substrate are fabricated without a guard ring in a 130-nm foundry CMOS process. The nand p-type diodes with an area of 16/spl times/0.32/spl times/0.32 /spl mu/m/sup 2/ achieve cutoff frequencies of /spl sim/1.5 and /spl sim/1.2 THz at 0-V bias, respectively. These are the highest cutoff frequencies for Schottky diodes fabricated in foundry silicon processes. The leakage currents at 1.0-V reverse bias vary between 0.4 to 10 nA for the n-type diodes. The break down voltage for these diodes is around 15 V. It should be possible to use these in millimeter wave and far infrared detection.     

Optimum design of stiffened cylindrical panels with constraint on the frequency in the presence of initial stresses

This paper presents the optimum design of stiffened cylindrical panels with weight as the objective function and constraints on the frequencies in the presence of initial stresses, using unconstrained minimization techniques of non-linear mathematical programming problem. The interaction between the buckling constraints and the frequency constraints in the presence of initial stresses are included in the formulation. Loss of load carrying capacity due to imperfection and due to suddenly applied loads are included in the buckling analyses. Results for cylindrical shell are obtained by setting the panel angle to 360 degrees. The relationship between the weight of the cylinder and the panel (a segment of the cylinder) is examined.     

A Microprocessor Based Measuring Instrument for Rapid Testing of Transformer Core Material

Precise knowledge of the characteristics of core material Is essential for the design of electromagnetic devices I Ike dynamos, I nstrument transformers and relays. Conventional measurement of the core characteristics Is a tedious process as it Involves collection of voluminous data and corrections thereto. An instrument using linear compensating networks and exploiting the processing capabilities of the popular microprocessor is developed for the measurement of core characteristics such as specific iron loss and the dynamic B-H curve. The necessary corrections are Incorporated In the software so that the end result can be straightaway used in design.     

Stability of tapered cantilever columns subjected to follower forces

Accurate estimates of critical loads of tapered cantilever columns with fixed or spring hinged ends subjected to follower forces are obtained in this paper. A Galerkin finite element method is used to solve the governing differential equation with variable coefficients. The effect of the stiffness of the spring hinge on the critical load is also studied.     

Complementary Antiparallel Schottky Barrier Diode Pair in a 0.13- $mu hbox{m}$ Logic CMOS Technology

A shunt-connected complementary antiparallel diode pair (C-APDP) using n- and p-type Schottky barrier diodes (SBDs) in a 0.13-mum CMOS logic process is demonstrated. The structure eliminates the deleterious effects of parasitic capacitance to substrate and reduces the substrate resistance effects. The extrapolated cutoff frequency of C-APDP is above 470 GHz, which demonstrates the potential as a millimeter-wave frequency component. The harmonic power measurements indicate that C-APDPs can generate more than 25 dB higher third harmonic powers than n-type SBDs. The C-APDPs can be integrated with the other devices in CMOS technologies to enable generation and processing of millimeter- and submillimeter-wave signals.     

Effect of matrix content on the performance of carbon paper as an electrode for PEMFC

Porous conducting carbon fiber‐based composite paper is used as an electrode backing in the fuel cell assembly. It not only acts as a channel through which the reactant and product gases pass to and from the bipolar plate and the catalyst site but also helps in the flow of electrons. In order to perform its role efficiently, it should have sufficient strength, high electrical conductivity, and ideal porous structure. Carbon paper has been fabricated, which builds up the required composite properties. Studies have been conducted to optimize the fiber/matrix ratio in the carbon paper, while ensuring the perfect combination of porosity, mechanical strength, and electrical conductivity for an electrode in a proton electrolyte membrane fuel cells. Detail physico‐mechanical and electrochemical characterizations further ascertain that the fiber/matrix ratio plays an important role in tuning the composite properties. The polarization curve of the unit proton exchange membrane (PEM) fuel cell (with an effective electrode area 4 cm²) shows a peak power density of 916 mW/cm² for the sample with fiber/matrix ratio of 65:35, which is almost the same as the commercially available sigracet gas diffusion layer (SGL) carbon paper tested under similar conditions. Further, proportionally enlarging the electrode area to 100 cm² shows that the carbon paper not only shows almost repeatable results in a given set up but also scales up.     

Numerical analysis of reaction–diffusion effects on species mixing rates in turbulent premixed methane–air combustion

The scalar mixing time scale, a key quantity in many turbulent combustion models, is investigated for reactive scalars in premixed combustion. Direct numerical simulations (DNS) of three-dimensional, turbulent Bunsen flames with reduced methane–air chemistry have been analyzed in the thin reaction zones regime. Previous conclusions from single step chemistry DNS studies are confirmed regarding the role of dilatation and turbulence–chemistry interactions on the progress variable dissipation rate. Compared to the progress variable, the mixing rates of intermediate species is found to be several times greater. The variation of species mixing rates are explained with reference to the structure of one-dimensional premixed laminar flames. According to this analysis, mixing rates are governed by the strong gradients which are imposed by flamelet structures at high Damköhler numbers. This suggests a modeling approach to estimate the mixing rate of individual species which can be applied, for example, in transported probability density function simulations. Flame–turbulence interactions which modify the flamelet based representation are analyzed.     

Some Thermodynamic Aspects of the Oxides of Chromium

To understand Cr emissions from slag melts to a vapor phase, an assessment of the stabilities of the chromium oxides at high temperatures has been carried out. The objective of the present study is to present a set of consistent data corresponding to the thermodynamic properties of the oxides of chromium, with special reference to the emission of hexavalent chromium from slags. In the current work, critical analysis of the experimental data available and a third analysis in the case of Cr₂O₃ have been carried out. Commercial databases, Fact Sage and ThermoCalc along with NIST-JANAF Thermochemical Tables, have been used for the analysis and comparisons of the results that are presented. The significant discrepancies in the available data have been pointed out. The data from NIST-JANAF Thermochemical Tables have been found to provide a set of consistent data for the various chromium oxides. An Ellingham diagram and the equations for the ΔG° (standard Gibbs free energy change) of formation of CrO _x have been proposed. The present analysis shows that CrO₃(g) is likely to be emitted from slag melts at high oxygen partial pressures.