Effect of iron addition on the precipitation behavior of CoNiCr alloys containing Nb

The effect of iron addition on the precipitation behavior of Co-Ni-Cr-Nb alloys is discussed. Iron addition changes the main precipitate from orthorhombic β-Ni₃Nb (Ni₃Cb) to BCTγ″-phase which is disc shaped and precipitates on {100} matrix planes. The growth ofγ″-precipitate follows the Lifshitz-Wagner theory of diffusion controlled growth. An attempt has been made to analyze the structure ofγ″ using the electronic considerations of the Engel-Brewer theory. On continued aging, metastableγ″ transforms to a stable β-phase on {111} matrix planes. The orientation relationship of this phase is similar to that observed in other alloys. In addition to intragranular precipitation, β=phase also precipitates at the grain boundaries and grows into the grains. The transformation ofγ″ into β-phase does not affect the hardness to any significant extent.     

Temperature rise in microwave p-i-n diodes: A computer aided analysis

Results of a computer aided thermal analysis of microwave p-i-n diodes are presented in this paper. The nonlinear heat flow equations in one dimension are solved using the central finite difference method of Leibman's formulation taking into account the temperature dependence of thermal conductivity and specific heat. Results are presented showing the temperature profile inside the device as a function of microwave pulsewidth and power dissipation. The effect of a heat sink on the temperature rise is also shown. The main conclusion arrived at is that the nonlinear thermal properties lead to higher temperature rise in the device and larger thermal time constants than could be expected otherwise. The method used for calculation is applicable for other solid state devices like the TRAPATT, the fast recovery thyristor, and power transistors where similar orders of power levels are involved.     

Temperature-dependent design parameters of TRAPATT diodes

The temperature-dependent design parameters of a TRAPATT diode are presented, and are obtained from the temperature-dependent device equations. It is shown that the design parameters change rapidly with temperature.     

Variability of chlorophyll concentration in the Arabian Sea and Bay of Bengal as observed from SeaWiFS data from 1997–2000 and its interrelationship with Sea Surface Temperature (SST) derived from NOAA AVHRR

Variability of chlorophyll concentration in the Arabian Sea and Bay of Bengal has been studied using SeaWiFS eight‐day average, 9 km processed data for the period 1997–2000. The interrelationship with sea surface temperature (SST) was studied with the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) derived, best SST product. The chlorophyll pattern shows in general high concentrations during February to March in the Arabian Sea and November to December in the Bay of Bengal. Year‐to‐year variations in temperature show an inverse relation with chlorophyll, at different locations, even on a monthly basis. However, the intraannual variability in chlorophyll at different locations shows differences in the relationship with SST. The Arabian Sea showed an inverse relationship at most of the locations, while a positive relationship was observed in the northwest region during October to December and an inverse relationship during January to April. The Bay of Bengal showed positive relationships at northeast locations, whereas no definite assessment could be made for other locations due to the narrow range of chlorophyll concentration.A longer time series (～10 years) will be required to establish a more concrete relationship but definitely consistent patterns are emerging from this study. The results form an additional dimension to the criteria for partitioning the ocean, required for global productivity or biophysical coupled modelling.     

Scheme to measure quantum stokes parameters and their fluctuations and correlations

Abstract

We propose a scheme to measure quantum Stokes parameters, their fluctuations and correlations. The proposal involves measurements of intensities and intensity-intensity correlations for suitably defined modes, which can be produced by a combination of half-wave and quarter-wave plates.     

Energy dynamics and bioenergy production of Populus deltoides G-3 Marsh plantation in eastern India

The energy content of stems, branches, roots and litter was determined using an oxygen bomb calorimeter, and these data were used to estimate energy storage, net energy fixation and energy transfer within poplar (Populus deltoides G-3 Marsh) plantations of two ages at the Research Farm of Rajendra Agricultural University, Pusa, Bihar, India. Energy fixation, storage and energy released and exit from the 7-year-old plantation were 1.69, 2.11 and 1.53 times that of the 5-year-old plantation. The net energy fixation was 243.08 GJ ha^?1 year^?1 in 5-year-old and 410.57 GJ ha^?1 year^?1 in 7-year-old plantation. The energy conservation efficiency in the 7-year-old plantation was higher (1.51%) than that of the 5-year-old plantation (0.89%). The 5-year-old plantation showed lower energy accumulation ratio (2.02) resulting from less energy accumulation in components of poplar tree and greater annual turnover in terms of litter fall. The energy stored in the above-ground tree components from 2131.87 ha (5-year old) and 1002.88 ha (7-year old) or in the above-ground net annual production from 3924.15 ha (5-year old) and 2386.37 ha (7-year old) of poplar plantations is sufficient to operate a 5 MW generating station for 1 year. Above-ground biomass and net production from 1 ha of 5-year-old and 7-year-old poplar plantations is sufficient to meet the energy need of an average household in eastern India for 8.5 and 18.0 years and 4.6 and 7.6 years, respectively.     

Further remarks on sequential estimation of a scale parameter in exponential distributions with an unknown location

The sequential procedure developed by Govindarajulu and Sarkar [Sequential estimation of scale parameter in exponential distributions with unknown location. Utilitas Math.40, 161–178 (1991)] for estimating the scale parameter of an exponential distribution, when the location parameter is unknown, is further analyzed. Generalizing the results of Govindarajulu and Sarkar, the ‘asymptotic risk-efficiency’ of the sequential procedure is established for the general loss function. A simple method of obtaining the asymptotic distribution of the stopping time is given. For the case of quadratic loss function and linear cost of sampling, a much simpler proof for obtaining the second-order approximations for the risk is provided.     

The coordinating model of the ganga basin

A scheme of model studies required to analyse a complex large scale system through decomposition approach is outlined. First, the total system is proposed to be modelled to identify interlinkages of the subsystems. Then the subsystems are analysed in detail to develop response functions. Finally the optimal system functioning is obtained by modelling the entire system in terms of response functions of the components. A linear programming model is developed for modelling the total system to identify the interlinkages. Its application is demonstrated in the Greater Ganga Basin using published data. Trade-off is developed between power generation and irrigated area in various seasons. A list of symbols is given at the end of the paper.