Effect of processing on fracture toughness of silicon carbide as determined by Vickers indentations

Several alpha-SiC materials were processed by hot isostatic pressing (HIPing) and by sintering an alpha-SiC powder containing boron and carbon. Several beta-SiC materials were processed by HIPing a beta-SiC powder with boron and carbon additions. The fracture toughnesses K(sub 1c) of these beta- and alpha-SiC materials were estimated from measurements of Vickers indentations. The three formulas used to estimate K(sub 1c) from the indentation fracture patterns resulted in three ranges of K(sub 1c) estimates. Furthermore, each formula measured the effects of processing differently. All three estimates indicated that fine-grained HIPed alpha-SiC has a higher K(sub 1c) than coarsed-grained sintered alpha-SiC. Hot isostatically pressed beta-SiC, which had an ultrafine grain structure, exhibited a K(sub 1c) comparable to that of HIPed alpha-SiC

On the selection of secondary indices in relational databases

An important problem in the physical design of databases is the selection of secondary indices. In general, this problem cannot be solved in an optimal way due to the complexity of the selection process. Often use is made of heuristics such as the well-known ADD and DROP algorithms. In this paper it will be shown that frequently used cost functions can be classified as super- or submodular functions. For these functions several mathematical properties have been derived which reduce the complexity of the index selection problem. These properties will be used to develop a tool for physical database design and also give a mathematical foundation for the success of the before-mentioned ADD and DROP algorithms

The Role of Yoga in Health and Wellness

Modern life style is posing a series challenge to human health The fast change of ever changing trends in modern life is causing physical moral mental and spiritual problems Chaos and confusion stress and tension commercialization and competition in every walk of life has lead to a situation where man is finding itself helpless regarding his personal health and hygiene An individual who comes to this earth has every right to enjoy each and every gift of nature to live freely and happily Technological advancement has resulted in reduction of physical labour and increased mental labour Tough labour in turn has resulted in psychosomatic disorders such as hyper tension diabetes insomnia acidity gastric problems etc Basically these disorders are caused due to faulty eating habits stressful working conditions lack of physical exercises and proper rest Yoga is the only possible remedy to counter these hazardous habits Practice of yogic principals and virtues are the only means wherein an individual can make his life happy and free from miseries Health and wellness is the concern of each and every person The condition of modern life offers us much less in spite of our material wealth than it did to the previous generations We suffer from the modern disease-stress stress created by selfishness competitiveness acquisitiveness and insensitivity to the destruction of our human relations and environment As a result we suffer from all sorts of physical and mental illness which evens our modern schools of medical science cannot alleviate Instead many people are turning to a far older tradition a tradition that appears to be steeped in religion and mystery but in facts are much more pragmatic in its application to our everyday lives than it would first appear Yoga should not be considered as an antiquated myth of yesterday because it has as much validity and value now as it had ever before and can offer guidance and help to the modern man There ar