Expert process planning system with solid model interface

Artificial intelligence (AI) techniques provide various tools for use in the development of automated process planning systems. AI can be utilized for automated reasoning about the shape, features and relationship between features and for development of expert systems for creating the process plan itself. Most of the previous work on AI in process planning deals with one specific application. This paper presents an integrated hierarchical framework of a process planning system with a CAD interface. The objective of the project discussed in the paper is to integrate design with process planning using AI techniques. The development of a CAD interface is discussed with respect to automated feature recognition, determination of tool approach direction and deciding the precedence relationship between the features. Sample results from the CAD interface are presented. The expert system for the process planning module is discussed with the part representation and knowledge base and the plan generation procedure. The module uses hierarchically organized frames for both part representation and the knowledge base. Some initial results are presented from the process planner to demonstrate the current capability of the system.     

Thermal Expansion of ZrC From 120 to 300 K by an X-Ray Powder Method

Thermal expansion of ZrC, which has the NaCI type structure, was determined from, 120 to 300 K by a powder X-ray diffraction method. The lattice parameter was measured precisely using a specially designed D-shaped symmetrical back-reflection-focusing camera with the specimen hanging from a cryoflask in the vacuum chamber outside the camera on the Rowland circle. The average coefficient of linear thermal expansion of ZrC in this temperature range is 6.22 x 10^-6/K. The Zr/C ratio was 0.993.     

Entrainment phenomenon in gas–liquid two-phase flow: A review

The gas–liquid separation equipments are aimed to be designed for maximum efficiency of phase separation. In order to maximize their capacity the flow rates are required to be optimized for the capital cost of equipment. This leads to the situation where the gas phase leaves the separation interface with high velocities and carry liquid phase along with it in the form of droplets reducing the equipment efficiency. This is known as entrainment or carryover. Depending on the nature of the separation interface i.e., turbulence intensity, bubble dynamics, the size and velocity distribution of liquid fragments, droplets at the separation interface varies. This is the main source of empiricism involved in the analysis of such equipments. The mechanics of motion of the dispersed liquid phase in bulk of gas is relatively well studied. In the present paper the various experimental, analytical and numerical investigations carried out to address the issues of entrainment/carryover are carefully analyzed. Further, a critical review has been presented for bringing out a coherent theme and a current status of the subject under reference.     

COMPARATIVE PERFORMANCE OF TWO QUADRANT CHOPPERS CAPABLE OF GIVING POSITIVE CURRENT AND VOLTAGE IN EITHER DIRECTION

ABSTRACT

Three possible control approaches for a two quadrant chopper, capable of providing positive current and voltage in either direction from a fixed d.c. input, are compared in this paper. The comparative study has been carried out for two types of loads -(a) Highly inductive load (ripple free current) and (b) Motor load The performance at the input as well as the load terminals is analysed and the results are presented in terms of normalised values. The boundaries between continuous and discontinuous conduction are also drawn to facilitate an estimation of filter inductance.     

Technical note Evaluation of Rajas than desertic terrain,India, for logistic support in oil exploration using Landsat Thematic Mapper data

Abstract

The desertic terrain of Rajaslhan, India, has been evaluated to work out the logistics relevant to planning a hydrocarbon exploration programme. The digitally enhanced, high-resolution Landsat-5 Thematic Mapper (TM) and SPOT data has helped in identifying various aeolian landforms. Sand dunes are most conspicuous. On the basis of sand-dune abundance, their amplitude, wavelength and direction, three land systems have been identified in the area. The gcomor-phic information extracted from the aforesaid satellite data has been used to assess each land sysem for its feasibility for seismic profiling, drill-site construction and groundwater location.     

Potentiality of Landsat,SPOT and IRS satellite imagery,for recognition of salt affected soils in Indian Arid Zone

Landsat, SPOT and IRS data, black and white and false colour composite (FCC) imagery of the summer (April, May), rainfed crop season (October) and winter irrigated crop season (January, February) of Indian Arid Zone were interpreted for recognition or three types of salt affected soils, viz. (1) natural salt affected; slight, moderate and severe, (2) saline soils due to saline water irrigation, (3) sodic soils due to high residual sodium carbonate (RSC) water irrigation. These were field checked and supported by analytical data. The Landsat-MSS band 4 could only provide the overall extent of salinity. The moderate and severe natural salt affected soils were identified by Landsat-MSS band 2, Landsat-MSS and TM, IRS LISS-I and LISS-II and SPOT HRV2 data for April and January. But the differentiation between the saline and sodic soils was possible only by the use of multi-date imagery (October and January) and the clue provided by the cropping pattern. The potentiality of remote sensing data products for identification of the types and degree of salt affected soils is discussed.     

New two-quadrant chopper with simultaneous control

A two-quadrant chopper circuit equipped with an improved commutation scheme and capable of giving variable positive voltage and current in either direction is described. Saturable reactors are used to support the direct bus voltage during the commutation interval. This commutation scheme has the advantages of low trapped energy, self-healing capability, low cost, etc. This chopper circuit has been designed, fabricated and tested on a 2·2 kW, 220 V separately excited DC motor. Theoretical deductions and their experimental verification are presented in the normalized form.     

Technical Note Study of desertification process in Aravalli environment using remote ensing techniques

The Aravalli environment in the vicinity of the Thar Desert in Rajasthan, India presents a clear picture of environmental degradation. This paper presents the study of the phenomenon occurring between the years 1975-1988. The approach adopted here uses remote sensing as a tool for the study of desertification using data from Landsat and IRS -1A (Indian Remote Sensing Satellite). First the satellite imagery of the area is interpreted using visual interpretation techniques. Next, some distinct features from this analysis are identified and are verified with the ground-truth collected by visiting the study area site. Finally, digitial image processing has been carried out using an Earth Resources Data Analysis System (ERDAS) to quantify the temporal changes. A rigorous data analysis yields the extent of the environmental degradation which appears to be quite alarming. Severe depletion in the area under the water and vegetation covers and accordingly an increase in the saline and aeolinous areas have been observed.     

Modelling effect of magnetic field on material removal in dry electrical discharge machining

One of the reasons for increased material removal rate in magnetic field assisted dry electrical discharge machining(EDM) is confinement of plasma due to Lorentz forces.This paper presents a mathematical model to evaluate the effect of external magnetic field on crater depth and diameter in single-and multiple-discharge EDM process.The model incorporates three main effects of the magnetic field,which include plasma confinement,mean free path reduction and pulsating magnetic field effects.Upon the application of an external magnetic field,Lorentz forces that are developed across the plasma column confine the plasma column.Also,the magnetic field reduces the mean free path of electrons due to an increase in the plasma pressure and cycloidal path taken by the electrons between the electrodes.As the mean free path of electrons reduces,more ionization occurs in plasma column and eventually an increase in the current density at the inter-electrode gap occurs.The model results for crater depth and its diameter in single discharge dry EDM process show an error of 9%-10%over the respective experimental values.     

Microscopic and macroscopic magnetic properties of MgAl<Subscript>x</Subscript>Cr<Subscript>x</Subscript>Fe<Subscript>2 − 2x</Subscript>O<Subscript>4</Subscript> spinel ferrite system

In order to study the effect of co-substitution of Al^{3 +} and Cr^{3 +} for Fe³⁺ in MgFe₂O₄ on its structural and magnetic properties, the spinel system MgAl _x Cr_xFe_{2 ? 2x}O₄ (x = 0.0–0.8) has been characterized by X-ray diffraction, high field magnetization, low field a.c. susceptibility and ⁵⁷Fe Mössbauer spectroscopy measurements. Contrary to the earlier reports, about 50% of Al^{3 +} is found to occupy the tetrahedral sites. The system exhibits canted spin structure and a central paramagnetic doublet was found superimposed on the magnetic sextet in the Mössbauer spectra (0.5 > x > 0.2). Thermal variation of a.c. susceptibility exhibits normal ferrimagnetic behaviour.