InGaN based light-emitting diodes （LEDs） with dip-shaped quantum wells and conventional rectangular quantum ~lls are numerically investigated by using the APSYS simulation software. It is found that the structure wi...InGaN based light-emitting diodes （LEDs） with dip-shaped quantum wells and conventional rectangular quantum ~lls are numerically investigated by using the APSYS simulation software. It is found that the structure with dip- aped quantum wells shows improved light output power, lower current leakage and less efficiency droop. Based on Lmerical simulation and analysis, these improvements on the electrical and the optical characteristics are attributed ainly to the alleviation of the electrostatic field in dip-shaped InGaN/GaN multiple quantum wells （MQWs）.展开更多
Carrier transport via the V-shaped pits （V-pits） in InGaN/GaN multiple-quantum-well （MQW） solar cells is numer- ically investigated. By simulations, it is found that the V-pits can act as effective escape paths fo...Carrier transport via the V-shaped pits （V-pits） in InGaN/GaN multiple-quantum-well （MQW） solar cells is numer- ically investigated. By simulations, it is found that the V-pits can act as effective escape paths for the photo-generated carriers. Due to the thin barrier thickness and low indium composition of the MQW on V-pit sidewall, the carriers entered the sidewall QWs can easily escape and contribute to the photocurrent. This forms a parallel escape route for the carries generated in the fiat quantum wells. As the barrier thickness of the fiat MQW increases, more carriers would transport via the V-pits. Furthermore, it is found that the V-pits may reduce the recombination losses of carriers due to their screening effect to the dislocations. These discoveries are not only helpful for understanding the carrier transport mechanism in the InGaN/GaN MQW, but also important in design of the structure of solar cells.展开更多
A growing number of multidisciplinary studies have reported the beneficial effects of physical activities towards the development of overall well-being and the reduction of chronic illnesses. Physical inactivity is a ...A growing number of multidisciplinary studies have reported the beneficial effects of physical activities towards the development of overall well-being and the reduction of chronic illnesses. Physical inactivity is a serious worldwide problem and is considered the key lifestyle factor that negatively influences health and function of individuals. Here we propose that growth kinetics of body and mind and associated disproportionate physical activity may have considerable effects on the increased physical and mental illnesses and premature death rates currently observed in mid to late adulthood people. Children and young adults, being in exponential growth phase and self-motivated to engage in physical activity, possess more cognition, resilience, and mind-body-emotion-spirit integration. In contrast, as our body transitions into adulthood, there is a decline in the growth of body and mind. Furthermore, in this period, adults experience the increased stressors of career and financial demands, time pressure, and family responsibilities. The decline in growth combined with prolonged stress appears to result in reduced cognition, resilience, and mind-body-emotion-spirit integration, leading to sedentary and other faulty lifestyles, which could further lead to a predisposition to maladaptive behaviours and various chronic diseases at a later stage. In agreement with this, currently more than two thirds of the adult population across the world are physically inactive and are failing to perform the daily recommended guidelines of moderate to vigorous exercise. As negative changes and faulty lifestyles begin to occur during and after adulthood transition, creating awareness in people between 29 to 35 years of age about mindful exercise should be considered a national priority. This would allow adults to achieve overall well-being, and increased productivity and life expectancy, reducing health care-associated economic burden placed on the nation.展开更多
我国煤层渗透率低且地质条件复杂,采用常规油气储层改造的开发方式难度大、技术适应性差。近年来,基于应力释放的煤层气改造新方法“煤层气水平井水力喷射造穴”很好地解决了这一技术瓶颈问题,但是造穴卸压—增渗的作用机制及其主控地...我国煤层渗透率低且地质条件复杂,采用常规油气储层改造的开发方式难度大、技术适应性差。近年来,基于应力释放的煤层气改造新方法“煤层气水平井水力喷射造穴”很好地解决了这一技术瓶颈问题,但是造穴卸压—增渗的作用机制及其主控地质因素尚不明晰。为此,考虑了煤岩层理和天然裂隙的影响,采用有限元—离散元耦合方法(Finite-Discrete Element Method,FDEM)建立了煤层气水平井扇形洞穴完井数值模型,探究了造穴后岩体的应力演化历程和储层的卸压—增渗机制,并对比分析了不同储层参数(孔隙压缩系数、储层强度、弱面强度和地应力场)对应力释放的影响规律。研究结果表明:(1)围岩演化过程为造穴后岩体收缩,储层发生应力重构,围岩强度逐渐降低,岩体内部发生新生裂隙萌生和原生裂隙扩展,形成开挖损伤区和应力释放区;(2)参数敏感性分析表明孔隙压缩系数是决定造穴完井储层适应性的关键,弱面强度、储层强度和地应力场分布决定了围岩的应力演化模式和裂缝扩展形态;(3)造穴卸压后储层增渗机制为穴周裂缝提升导流能力,储层应力释放提升基质渗透率。结论认为,模型首次综合考虑了地层特点、造穴过程和煤岩裂隙的影响,研究结果揭示了煤层造穴后的应力演化过程及其卸压、增渗作用机制,深化了对煤层气水平井洞穴完井增产机理的认识,对我国煤层储层改造具有重要的工程参考价值。展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50602018)the Science and Technology Program of Guangdong Province of China (Grant Nos. 2010B090400456, 2009B011100003, and 2010A081002002)the Scienceand Technology Program of Guangzhou City, China (Grant No. 2010U1-D00191)
文摘InGaN based light-emitting diodes （LEDs） with dip-shaped quantum wells and conventional rectangular quantum ~lls are numerically investigated by using the APSYS simulation software. It is found that the structure with dip- aped quantum wells shows improved light output power, lower current leakage and less efficiency droop. Based on Lmerical simulation and analysis, these improvements on the electrical and the optical characteristics are attributed ainly to the alleviation of the electrostatic field in dip-shaped InGaN/GaN multiple quantum wells （MQWs）.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61564007 and 11364034)the Sci-Tech Support Plan of Jiangxi Province,China(Grant No.20141BBE50035)
文摘Carrier transport via the V-shaped pits （V-pits） in InGaN/GaN multiple-quantum-well （MQW） solar cells is numer- ically investigated. By simulations, it is found that the V-pits can act as effective escape paths for the photo-generated carriers. Due to the thin barrier thickness and low indium composition of the MQW on V-pit sidewall, the carriers entered the sidewall QWs can easily escape and contribute to the photocurrent. This forms a parallel escape route for the carries generated in the fiat quantum wells. As the barrier thickness of the fiat MQW increases, more carriers would transport via the V-pits. Furthermore, it is found that the V-pits may reduce the recombination losses of carriers due to their screening effect to the dislocations. These discoveries are not only helpful for understanding the carrier transport mechanism in the InGaN/GaN MQW, but also important in design of the structure of solar cells.
文摘A growing number of multidisciplinary studies have reported the beneficial effects of physical activities towards the development of overall well-being and the reduction of chronic illnesses. Physical inactivity is a serious worldwide problem and is considered the key lifestyle factor that negatively influences health and function of individuals. Here we propose that growth kinetics of body and mind and associated disproportionate physical activity may have considerable effects on the increased physical and mental illnesses and premature death rates currently observed in mid to late adulthood people. Children and young adults, being in exponential growth phase and self-motivated to engage in physical activity, possess more cognition, resilience, and mind-body-emotion-spirit integration. In contrast, as our body transitions into adulthood, there is a decline in the growth of body and mind. Furthermore, in this period, adults experience the increased stressors of career and financial demands, time pressure, and family responsibilities. The decline in growth combined with prolonged stress appears to result in reduced cognition, resilience, and mind-body-emotion-spirit integration, leading to sedentary and other faulty lifestyles, which could further lead to a predisposition to maladaptive behaviours and various chronic diseases at a later stage. In agreement with this, currently more than two thirds of the adult population across the world are physically inactive and are failing to perform the daily recommended guidelines of moderate to vigorous exercise. As negative changes and faulty lifestyles begin to occur during and after adulthood transition, creating awareness in people between 29 to 35 years of age about mindful exercise should be considered a national priority. This would allow adults to achieve overall well-being, and increased productivity and life expectancy, reducing health care-associated economic burden placed on the nation.
文摘我国煤层渗透率低且地质条件复杂,采用常规油气储层改造的开发方式难度大、技术适应性差。近年来,基于应力释放的煤层气改造新方法“煤层气水平井水力喷射造穴”很好地解决了这一技术瓶颈问题,但是造穴卸压—增渗的作用机制及其主控地质因素尚不明晰。为此,考虑了煤岩层理和天然裂隙的影响,采用有限元—离散元耦合方法(Finite-Discrete Element Method,FDEM)建立了煤层气水平井扇形洞穴完井数值模型,探究了造穴后岩体的应力演化历程和储层的卸压—增渗机制,并对比分析了不同储层参数(孔隙压缩系数、储层强度、弱面强度和地应力场)对应力释放的影响规律。研究结果表明:(1)围岩演化过程为造穴后岩体收缩,储层发生应力重构,围岩强度逐渐降低,岩体内部发生新生裂隙萌生和原生裂隙扩展,形成开挖损伤区和应力释放区;(2)参数敏感性分析表明孔隙压缩系数是决定造穴完井储层适应性的关键,弱面强度、储层强度和地应力场分布决定了围岩的应力演化模式和裂缝扩展形态;(3)造穴卸压后储层增渗机制为穴周裂缝提升导流能力,储层应力释放提升基质渗透率。结论认为,模型首次综合考虑了地层特点、造穴过程和煤岩裂隙的影响,研究结果揭示了煤层造穴后的应力演化过程及其卸压、增渗作用机制,深化了对煤层气水平井洞穴完井增产机理的认识,对我国煤层储层改造具有重要的工程参考价值。
