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Numerical Analysis of Two-Way Interaction between Weld-Pool and Arc for GTA Welding Process

Journal of Materials Science & Technology 2001年第1期17卷 171-172页

作者： Yongping LEI Xianghua GU Yaowu SHI Welding Research Insttute School of Mechanical EngineeringXi’an Jiaotong UniversityXi’an 710049China Beijing Polytechnic University

A mathematical model to describe the heat transfer and fluid flow in the mutually coupled weld pool and arc by an interactive free surface of the pool for a stationary gas tungsten arc welding (GTAW) is developed. The two sets of governing equations and auxiliary formulas, controlling the weld pool and plasma arc systems respectively, were solved by a finite difFerence method. A boundary-fitted coordinate system was adopted because the free surface has a curved and unknown shape during welding. The results of this work provide a fundamental basis for predicting the behavior of an integrated' weld pool and arc system from first principles.

关键词： heat transfer and fluid flow gas tungsten arc welding free surface finite difference method mathematical model coordinate system first principles plasma arc sets of

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Energy Balance and Physical Activity

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Biomedical and Environmental Sciences 2001年第1期14卷 130-136页

作者： KALLAYA KIJBOONCHOO Institute of Nutrition and Faculty of Graduate Studies

The prevalence of obesity is increasing in most parts of the world and becoming one of the major global public health problems. Although the components of energy balance have not been adequately estimated over time, available evidence suggests that the increase in obesity is the result of reduced physical activity.\;Increases in physical activity have been shown to be strongly associated with improving physical fitness and body composition, with probably a positive effect on resting metabolic rate. The Surgeon General's Report on Physical Activity and Health advocates that 30 min of regular, moderate_intensity physical activity is associated with decreases in the risk of chronic diseases and may contribute to quality of life. However, the small changes that contribute 10 min for 3 times a day for aerobic training, or one set instead of three sets of repetitions on resistance training will provide individuals with health benefits. Indeed, nutrition and physical activity should be considered an integral part of fitness and good health, and should be encouraged in all age groups, particularly early in life. The question is no longer centered around the health benefit of increasing physical activity, but rather creating self awareness and behavior changes in individuals. Hence, effective intervention programs are needed that foster long term changes in physical activity. Among various interventions, the Nutrifit program was recently conducted in Thailand and found to improve health related fitness in children. The development of more effective interventions and approaches is a major challenge in this field today.

关键词： physical activity physical fitness body composition quality of life positive effect energy balance public health instead of age groups sets of

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On a Fourth-order Eigenvalue Problem

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数学进展 2000年第1期29卷 91-93页

作者：鲁梦僧西北师范大学甘肃兰州 730070

We consider the existence of positive solutions for the equationd4y/dx4-λf(x,y(x))=0,(1)with one of the following sets of boundary value conditionsy(0)=y(1)=y'(0)=y'(1)=0,(2)y(0)=y′(1)=y'(0)=y'′(1)=0.(3)

关键词： boundary value conditions positive solutions sets of

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A Bayesian approach to matched field processing in uncertain ocean environments

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Chinese Journal of Acoustics 2008年第4期27卷 358-367页

作者： LI Jianlong PAN Xiang Department of Information Science & Electronic Engineering Zhejiang University Hangzhou 310027

An approach of Bayesian Matched Field Processing （MFP） was discussed in the uncertain ocean environment. In this approach, uncertainty knowledge is modeled and spatial and temporal data received by the array are fully used. Therefore, a mechanism for MFP is found, which well combines model-based and data-driven methods of uncertain field processing. By theoretical derivation, simulation analysis and the validation of the experimental array data at sea, we find that （1） the basic components of Bayesian matched field processors are the cor- responding sets of Bartlett matched field processor, MVDR （minimum variance distortionless response） matched field processor, etc.; （2） Bayesian MVDR/Bartlett MFP are the weighted sum of the MVDR/Bartlett MFP, where the weighted coefficients are the values of the a posteriori probability; （3） with the uncertain ocean environment, Bayesian MFP can more correctly locate the source than MVDR MFP or Bartlett MFP; （4） Bayesian MFP can better suppress sidelobes of the ambiguity surfaces.

关键词： ocean environments matched field processing Matched Field Processing weighted coefficients weighted sum methods of sets of

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