Purification of cadmium by selective volatilization in vacuum in presence of oxide phase on its melt

Purification of cadmium in the presence of a thin (~0·001?mm) oxide layer on the surface of the molten metal was carried out using a simple system designed and fabricated locally. The analytical results revealed that the distillation through oxide layer gave better separation for Co, Ni, Cu, Zn, Ag, Sn, Hg and Tl, when compared to the distillation without oxide layer. This was attributed due to the impurity metal oxide phases formation on the surface of the molten metal. The influence of oxygen flow time on the distillation rate of cadmium was established. There was no excess oxygen (O) retained in the distillate after two consecutive vacuum distillations through oxide route. The experiments were conducted at the level of nearly 1·5?kg a batch to study the impurities behaviour due to upscaling. The detailed chemical analysis of 58 impurity elements in Cd in presence and absence of oxide layer was carried out by glow discharge mass spectrometry (GDMS).     

Fuzzy set theoretic approach of assigning weights to objectives in multieriteria decision making

A rational procedure is developed for ranking the multiobjectives of a vector maximum problem, thereby leading to proper assignment of weights to the objectives. To achieve this, we determine the range of each decision variable from the constraints set and transform them into the unit interval. After scaling the decision variables, we scale down the objectives also into the unit interval. Following Yager (1981), an ordering function of the objectives is determined. This ordering function value is nothing but the strength of preference inherent in the objectives. Accepting the strength of preference, we obtain the weights for the respective objectives. A numerical example is given to illustrate the procedure.     

Study of Leaching of Multimetal Sulphides Through an Interdisciplinary Approach

The leaching of a real multimetal bulk concentrate cannot often be adequately understood on the basis of published literature on simpler and often ideal systems because the process is far too complex, Moreover, the data can become ambiguous in the absence of adequate information on raw materials. Thus any process development work requires a thorough knowledge of the raw material characteristics. This paper describes the use of an interdisciplinary study for a better understanding of ammonia leaching of multimetal sulphides. The techniques employed comprise of X-ray diffraction, thermal analysis, chemical analysis and microscopy.     

Experimental Studies on the Self-Shielding Effect in Fissile Fuel Breeding Measurement in Thorium Oxide Pellets Irradiated with 14 MeV Neutrons

The 14 MeV neutrons produced in the D-T fusion reactions have the potential of breeding Uranium-233 fissile fuel from fertile material Thorium-232. In order to estimate the amount of U-233 produced, experiments are carried out by irradiating thorium dioxide pellets with neutrons produced from a 14 MeV neutron generator. The objective of the present work is to measure the reaction rates of 232 Th + 1 n → 233 Th → 233 Pa → 233 U in different pellet thicknesses to study the self-shielding effects and adopt a procedure for correction. An appropriate assembly consisting of high-density polyethylene is designed and fabricated to slow down the high-energy neutrons, in which Thorium pellets are irradiated. The amount of fissile fuel ( 233 U) produced is estimated by measuring the 312 keV gammas emitted by Protactinium-233 (half-life of 27 days). A calibrated High Purity Germanium (HPGe) detector is used to measure the gamma ray spectrum. The amount of 233 U produced by Th 232 (n, γ) is calculated using MCNP code. The self-shielding effect is evaluated by calculating the reaction rates for different foil thickness. MCNP calculation results are compared with the experimental values and appropriate correction factors are estimated for self-shielding of neutrons and absorption of gamma rays.     

Rice crop identification and area estimation using remotely-sensed data from Indian cropping patterns

Abstract

This study attempts to give an appraisal of the use of remotely-sensed data for different rice cropping patterns specific to India. Using even 80 m spatial resolution data of LANDSAT MSS in the form of false colour composites (FCCs), the rice crop was identified with an accuracy of 90 to 94 per cent from cropping patterns having more than 50 per cent of cropped area under rice. Cropping patterns having less than 50 percent of cropped area under rice and the rest of the area under multiple crops were identified with an accuracy of 75 percent. From the Indian experiences of higher spatial resolution multispcctral scanner data (3m resolution) and in the present study, it was observed that besides higher spatial resolution, acquisition of data at the critical crop windows (the periods of minimum overlap of greenness of rice with other crops) is necessary to reach 90 per cent accuracy for multiple cropping patterns.     

具有对称特征的三维模型重构技术研究

针对具有对称特征模型的逆向重构问题,首先利用ICP算法进行数据匹配并提取初始对称面,其次精确提取对称面,然后利用基于边和面的混合数据分割方法对预处理过的模型进行数据分割,最后重构得到一半的对称特征模型,再利用提取的对称平面进行镜像,得到完整的对称特征模型.此方法可快速实现模型逆向重构又能提高建模精度,应用于汽车内饰件的逆向重构中,既减少数据量,又节省运算时间,并且重构的模型及特征是关于平面完全对称的.     

Gyres off the Somali coast and western boundary currents in the Bay of Bengal during the south-west monsoon

Satellite remotely-sensed sea surface temperature (SST) data were obtained during the initial phase of the onset of the south-west monsoon in the north-western Indian Ocean for the years 1987and 1988. Large wedge-like areas of upwelled water during 1988 were observed at 5°Nand 10°N after the Somali current spinup, indicative of a two-gyre circulation in the Somali current system. Satellite infrared observations of the Bay of Bengal during the early February 1990revealed the existenceof two bands of warm water that resembled a western boundary current (WBC) along the east coast of India. A warm core eddy, with a major axis of nearly 120km, appeared at 89°E and 19°N at the end of the axis of the current. The existence of the two gyre system ofT the Somali coast and the presence or absence of the WBC in the Bay of Bengal in response to the onset of the summer monsoon has been discussed in detail.     

Technology Trends in the Extractive Metallurgy of Zirconium,Titanium, Tantalum and Niobium

The reactive and refractory metals zirconium, titanium, tantalum and niobium have been in commercial production and industrial application over the last 30 years and more. With growing experience, there has been progressive improvement in process and equipment designs in the industrial practice. There has also been a continuous drive to develop entirely new processes, and to diversify the applications of these metals. The paper reviews the present status and the emerging trends, and places the Indian work in the global perspective.     

Inter-satellite calibration linkages for the visible and near-infared channels of the Advanced Very High Resolution Radiometer on the NOAA-7, -9, and -11 spacecraft

The post-launch degradation of the visible (channel 1:≈0· 58–0·68μm) and near-infrared (channel 2: ≈ O·72–1·1 μm) channels of the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA–7, –9, and –11 Polar-orbiting Operational Environmental Satellites (POES) was estimated using the south-eastern part of the Libyan desert as a radiometrically stable calibration target. The relative annual degradation rates, in per cent, for the two channels are, respectively: 3·6 and 4·3 (NOAA–7) 5·9 and 3·5 (NOAA–9); and 1·2 and 2·0 (NOAA–11). Using the relative degradation rates thus determined, in conjunction with absolute calibrations based on congruent path aircraft/satellite radiance measurements over White Sands, New Mexico (U.S.A.), the variation in time of the absolute gain or ‘slope’ of the AVHRR on NOAA–9 was evaluated. Inter-satellite calibration linkages were established, using the AYHRR on NOAA–9 as a normalization standard. Formulae for the calculation of calibrated radiances and albedos (AYHRR usage), based on these interlinkages, are given for the three AYHRRs.     

GEOMETRIC PROGRAMMING. A NEW HYBRID ALGORITHM BASED ON LIAPUNOV CONCEPTS (MADLAP)

This article concerns the development of a simple yet very efficient heuristic procedure for optimizing the design or a reactor system employing continuous stirred tanks in series using Michaelis-Menten kinetics. The heuristic procedure employs a modified form or the well known Golden Search method to estimate the optimal number of reactors to be employed. The procedure was tested on an IBM personal computer under a wide range of values for three model parameters, namely the economy or scale factor, the scaled Michaelis-Menten constant and the desired degree of conversion to be attained. The results of this study indicated that the heuristic optimization procedure is capable of obtaining solutions that are either identical or very close to the actual optimal solutions in a very efficient manner.