Exit chipping in ID sawing of silicon crystals

The processes involved in exit chipping which may occur in the internal diameter diamond sawing of silicon crystals were examined. An interpretation of chipping observations is given in terms of crack propagation as acted upon by the sawing stresses. Since the exit chips are roughly parallel to saw marks, the general locus of the crack must be determined by contact stresses although the exact locus depends on already existing subfractures located in the kerf region which are caused by more than one abrasive particle. The crack starts at either edge since these are weak areas in flexure. In the more extensive "saw fracture", the fracture plane often changes part-way across the slice to be other than parallel to the saw mark because the speed of the crack accelerates beyond the speed of the blade travel; i.e., outstrips the advance of the contact stress field. The influences of various external factors on the opening of the crack are divided into two types: factors that wedge the crack apart and those that bend the slice away from the crystal. From a consideration of these factors, conditions for minimizing exit chipping are defined

POLICY, POLITICS AND PROJECTIONS IN MEXICAN AGRICULTURE

Agribusiness,

Solar cell and I.C. aspects of ingot-to-slice mechanical processing

Intensive efforts have been put into the growth of silicon crystals to suit today's solar cell and integrated circuit requirements. Each step of processing the crystal must also receive concentrated attention to preserve the grown-in perfection and to provide a suitable device-ready wafer at reasonable cost. A comparison is made between solar cell and I.C. requirements on the mechanical processing of silicon from ingot to wafer. Specific defects are described that can ruin the slice or can possibly lead to device degradation. These include grinding cracks, saw exit chips, crow's-foot fractures, edge cracks, and handling scratches

LM landing radar test for the F mission - Project Apollo

Determining test requirements for LM landing radar for F missio

Foreword

This report provides a study and a simulation of a feasible system configuration for the implementation of a Stirling engine for electrification of rural areas in Bolivia. The aim of the review is to determine if a hybrid system combining a biomass-fired Stirling engine and photovoltaic technology may respond to a basic electricity need. An introductory literature study about the Stirling engine technology and the energy resources and characteristics of Bolivia leads to a further proposal of the selected system for rural electrification. The chosen Stirling engine for this study is a 3 kW electric output engine combined with a PV array of 0.9 kW and a battery bank with a capacity of 1200 Ah. The power demand that must be satisfied is based on a rural village in the department of Beni with an amount of 24 households. The simulation is performed in the software Homer Energy where an energy balance between the generated power and the demand can be analysed in order to optimise the power generation strategy. Two scenarios are simulated with monthly demands of 45 and 60 kWh per household. Results from the study indicate that the decision on the size of the Stirling engine must be attached to the demand that is going to satisfy in order to avoid insufficient or excessive power production. In addition, although the PV technology allows an increase on the power demand that the system can handle and makes it more flexible, its contribution is not of the same order of the Stirling engine. The described system configuration is able to attend a demand up to 55 kWh/day and a peak power of 3.8 kW. In conclusion, Stirling engines have the potential to become a good solution for rural electrification, especially when making use of CHP strategies to increase the overall efficiency of the energy generation and fulfil both the electric and thermal demands of rural populations.

Spatial Mixing of Coloring Random Graphs

We study the strong spatial mixing (decay of correlation) property of proper $q$-colorings of random graph $G(n, d/n)$ with a fixed $d$. The strong spatial mixing of coloring and related models have been extensively studied on graphs with bounded maximum degree. However, for typical classes of graphs with bounded average degree, such as $G(n, d/n)$, an easy counterexample shows that colorings do not exhibit strong spatial mixing with high probability. Nevertheless, we show that for $q\ge\alpha d+\beta$ with $\alpha>2$ and sufficiently large $\beta=O(1)$, with high probability proper $q$-colorings of random graph $G(n, d/n)$ exhibit strong spatial mixing with respect to an arbitrarily fixed vertex. This is the first strong spatial mixing result for colorings of graphs with unbounded maximum degree. Our analysis of strong spatial mixing establishes a block-wise correlation decay instead of the standard point-wise decay, which may be of interest by itself, especially for graphs with unbounded degree

Application of continuous form of dynamic programming and inaccessible state variable theory to the K-8 accelerometer

Dynamic programming and inaccessible state variable theory applied to accelerometer desig

Cleanroom software development

The 'cleanroom' software development process is a technical and organizational approach to developing software with certifiable reliability. Key ideas behind the process are well structured software specifications, randomized testing methods and the introduction of statistical controls; but the main point is to deny entry for defects during the development of software. This latter point suggests the use of the term 'cleanroom' in analogy to the defect prevention controls used in the manufacturing of high technology hardware. In the 'cleanroom', the entire software development process is embedded within a formal statistical design, in contrast to executing selected tests and appealing to the randomness of operational settings for drawing statistical inferences. Instead, random testing is introduced as a part of the statistical design itself so that when development and testing are completed, statistical inferences are made about the operation of the system

Combustion of hydrogen injected into a supersonic airstream (a guide to the HISS computer program)

A computer program based on a finite-difference, implicit numerical integration scheme is described for the prediction of hydrogen injected into a supersonic airstream at an angle ranging from normal to parallel to the airstream main flow direction. Results of calculations for flow and thermal property distributions were compared with 'cold flow data' taken by NASA/Langley and show excellent correlation. Typical results for equilibrium combustion are presented and exhibit qualitatively plausible behavior. Computer time required for a given case is approximately one minute on a CDC 7600. A discussion of the assumption of parabolic flow in the injection region is given which demonstrates that improvement in calculation in this region could be obtained by a partially-parabolic procedure which has been developed. It is concluded that the technique described provides an efficient and reliable means for analyzing hydrogen injection into supersonic airstreams and the subsequent combustion