CVD反应器传输过程的三维数学模型

提出了一个同时表示CVD过程的气体流动、温度分布和物质传输的三维数学模型。应用这个模型预报了在含有SiCl_4的氢气流中沉积出Si的锥台式反应器中的速度场、温度场和浓度场。所得的结果有助于增进对这类反应器中的传输过程的认识,模型亦可用于设计参数的最优化,诸如入口流量,锥台倾角等。     

顶吹转炉内金属液滴的产生、运动及传热的数学模型

本文开发了一个普适的顶吹转炉内金属液滴的产生、运动及传热的数学模型，在对炉内气体的流动、燃烧及传热研究的基础之上，引进液滴产生的分布函数，用概率模拟的Ｍｏｎｔｅ－Ｃａｒｌｏ方法模拟了液滴的随机产生（尺寸、位置及初速度），在Ｌａｎｇｒａｎｇｉａｎ的框架下跟踪了液滴的运动，计算了液滴的传热及温度变化，最后对所有液滴进行统计，给出了一些有实际意义的物理量（平均停留时间、平均传热量、平均上升最大高度等）的统计平均值。应用该模型计算了１８０ｔ转炉内液滴的产生、运动及传热情况，结果表明液滴在转炉内二次燃烧过程的传热中是一种重要的传热方式     

INFLUENCE OF SOME FACTORS ON FLUID FLOW IN CONTINUOUS CASTING TUNDISHES

The influence of some factors on velocity field in continuous casting tundishes has been veri-fied by means of computer simulation.These factors are tundish wall inclination;thedimensionless geometric size of tundish,the double inclined wall tundish;the dimension andlocation of weir and dam.     

氧气顶吹转炉中二次燃烧现象的数学模型

开发了包括K-ε双方程湍流模型、燃烧反应的混合分数f和湍流燃烧浓度波动g的三维湍流燃烧数学模型,并应用于氧气顶吹转炉的二次燃烧过程中,在未涉及到辐射传热、多相流动以及有限反应速率等问题的情况下,得到了氧气顶吹转炉中二次燃烧时废气的流动方式,温度分布及火焰形状等结果,还研究了氧枪的高度和二次吹氧孔的水平夹角对冶炼的影响。     

Land-use survey of Idukki District

The growing population pressure and limited availability of land necessitates proper utilization of the available land through scientific land-use planning. Realizing this fact, a project using multiband aerial photography was taken up with following objectives: identification and mapping of areas under various land uses, study of geomorphology, identification of potential groundwater areas and identification of areas requiring soil conservation and reclamation measures. The major land-use classes mapped are agriculture, forest, wasteland, water bodies and public use. These are further subclassified. Some of the important observations are the reduction in the area under forest and the existence of a large area under wasteland. Geomorphological maps prepared depict slope, relief, drainage and vegetation. With the help of structural and geomorphological maps, the technique of identifying potential groundwater areas has been demonstrated. The land-use maps have a classification accuracy of 86 per cent whereas the accuracy of slopes in geomorphological maps is 72 per cent. The locational accuracy of the land features is 50-150 m on the ground. Visual interpretation of LANDSAT images led to the identification of nine land-cover classes while digital analysis enabled identification of twelve land-cover classes. Significant changes in land cover over a decade (1973-1982) have been noticed. This information has been used for preparation of a detailed land-use plan for the Idukki District.     

Spectral response of rice crop and its relation to yield and yield attributes

Ground-based radiometric measurements were conducted on six varieties of rice crop during an entire growth cycle using a hand-held seven-band radiometer. Concomitant measurements of some of the yield attributes were also made. Spectral data were also collected on a single variety grown under 12 different fertilizer treatments. Spectral data have been correlated with leaf area index, total wet biomass, total dry biomass, plant water content and final grain, straw and total yield. The results show similar temporal spectral responses of all six varieties and a strong correlation of agronomic parameters with spectral parameters derived from the near-infrared and red radiances. Red and near-infrared radiance ratio and normalized differences were found sensitive to the N fertilizer application but not to the P and K fertilizers. Linear correlations were observed between spectral parameters and final grain, straw and total yield     

Acoustic Methods for Characterisation of Microstructures and Deformation Processes in Nimonic Alloy PE 16 and Zircaloy-2

Abstract

This paper discusses the experience of the authors in using ultrasonic attenuation and velocity measurements and acoustic emission technique for characterisation of micro-structures and deformation processes in Nimonic alloy PE 16 and Zircaloy-2. It is possible to assess the volume fraction of γ' in Nimonic alloy PE 16 using ultrasonic velocity measurements. Acoustic emission technique is useful to monitor the influence of presence of secondary phases γ' and MC independently and also their conjoint presence on tensile deformation. In Zircaloy-2. low frequency ultrasonic velocity measurements are useful for detecting presence of hard intermetallics and high frequency velocity measurements are useful for revealing the early stage dissociation of β quenched microstructure to α phase. Also, assessment of hydrogen concentration in the range 25 to1100 mg/kg in Zircaloy-2 is possible using ultrasonic velocity ratio (longitudinal to shear) obtained from the precise ultrasonic transit time measurements.     

An optimal estimation technique for increasing the accuracy of crop forecasts by combining remotely sensed and conventional forecast results.

Abstract

An optimal estimation (OE) technique has been used to increase the accuracy of crop acreage and yield estimates by combining results from remotely sensed (RS) data and conventional models. For crop acreage estimation the OE increased the accuracy of wheat acreage estimation when the first forecasts of the Directorate of Economics and Statistics (DES) were combined with state level RS estimates over the states of Haryana and Punjab in India.

To increase the accuracy of wheat yield forecasts an autoregressive (AR) model was developed. Results of AR model were optimally combined with RS-based estimates for Hisar and Karnal districts in Haryana, India. The OE results for a total of eight forecasts had a lower mean absolute per cent deviation than the forecasts using RS and AR approaches. The power of OE was further demonstrated by combining weather-based wheat yield model results for the state of Punjab (India) with first order AR model results, suggesting an increase in accuracy of forecasts by optimally combining results from two or more algorithms.     

THREE-DIMENSIONAL MATHEMATICAL MODELING OF TRANSPORT PROCESSES IN CVD REACTORS

A mathematical model to represent the fluid flow, temperature distribution and mass transferin CVD reactors has been developed. The model is used to predict the velocity, temperature,and molar concentration profiles in the tapered annulus of a reactor for silicon deposition fromSiCl_4 in H_2. Results of the investigation contribute to the understanding of the transport pro-cesses involved in such a system. The model can also be used for optimizing the designparameters, such as inlet flow rate, susceptor tilt angle, etc.     

顶吹转炉内二次燃烧初期的一个数学模型

本文在对顶吹转炉内气体流动，燃烧，传热研究的基础之上，合理耦合了炉内液滴北生，运动及传热的模型，给出了一个较全面的描述炉内燃烧与传热的数学模型。应用该模型研究了美国常用的１８０ｔ Ｂａｓｉｃ Ｏｘｙｇｅｎ Ｆｕｒｎａｃｅｓ炉内二次燃烧初期泡沫渣还未大量形成的燃烧及传热情况，得出了这一时期不同的二次氧枪设计与炉内二次燃烧率及热量传输效率之间的关系。