Hybrid Si/SiC switches constituting a parallel connection of a lower current rated SiC MOSFET and a higher current rated Si IGBT are becoming very attractive solution for designing high frequency and high-power densit...Hybrid Si/SiC switches constituting a parallel connection of a lower current rated SiC MOSFET and a higher current rated Si IGBT are becoming very attractive solution for designing high frequency and high-power density power electronic converters.Due to the complementary nature of Si IGBT devices(smaller inverter cost and smaller conduction loss)and SiC devices(smaller switching loss and higher junction temperature capability),these novel switch device configurations enable a good tradeoff between cost and efficiency for high power converter applications.One such recent application of hybrid Si/SiC switches for efficiency-cost optimization is an Si/SiC hybrid switch based ANPC inverter proposed in Ref.[30].In Ref.[30]the topology structure,modulation strategy and the efficiency-cost benefits of the proposed ANPC inverter is presented.In this paper a precise electro-thermal power loss model for this ANPC inverter topology will be presented based on the modulation strategy of the inverter and the operating characteristics of the Si/SiC hybrid switches.The power loss model development takes into account how the current sharing between the two internal devices of the Si/SiC hybrid switches and their corresponding gate control method affects their power loss.A brief introduction to the topology structure and operation principle of the Si/SiC based ANPC inverter is first highlighted to provide context for readers and then a detailed description of the proposed electro-thermal power loss model is presented.The precision of the electro-thermal power loss model introduced in this paper is then validated using experimentally measured energy loss,device temperature and inverter efficiency data.展开更多
The classical minimization of power losses in transmission lines is dominated by artificial intelligence techniques, which do not guarantee global optimum amidst local minima. Revolutionary and evolutionary techniques...The classical minimization of power losses in transmission lines is dominated by artificial intelligence techniques, which do not guarantee global optimum amidst local minima. Revolutionary and evolutionary techniques are encumbered with sophisticated transformations, which weaken the techniques. Power loss minimization is crucial to the efficient design and operation of power transmission lines. Minimization of losses is one way to meet steady grid supply, especially at peak demand. Thus, this paper has presented a gradient technique to obtain optimal variables and values from the power loss model, which efficiently minimizes power losses by modifying the traditional power loss model that combines Ohm and Corona losses. Optimality tests showed that the unmodified model does not support the minimization of power losses on transmission lines as the Hessian matrix portrayed the maximization of power losses. However, the modified model is consistent with the gradient method of optimization, which yielded optimum variables and values from the power loss model developed in this study. The unmodified (modified) models for Bujagali-Kawanda 220 kV and Masaka West-Mbarara North 132 kV transmission lines in Uganda showed maximum power losses of 0.406 (0.391) and 0.452 (0.446) kW/km/phase respectively. These results indicate that the modified model is superior to the unmodified model in minimizing power losses in the transmission lines and should be implemented for the efficient design and operation of power transmission lines within and outside Uganda for the same transmission voltages.展开更多
With the explosive development of wireless communication and low power embedded techniques, Body Area Network (BAN) has opened up new frontiers in the race to provide real-time health monitoring. IEEE 802 has establis...With the explosive development of wireless communication and low power embedded techniques, Body Area Network (BAN) has opened up new frontiers in the race to provide real-time health monitoring. IEEE 802 has established a Task Group called IEEE 802.15.6 inNovember 2007 and aims to establish a communication standard optimized for low power, high reliability applied to medical and non-medical application for BANs. This paper overviews the path loss model and the communication scheme for implant-to-body surface channel presented by IEEE 802.15.6 standard. Comparing with the standard scheme where BCH (Bose-Chaudhuri-Hochquenghem) code is employing, we propose a new coding solution using convolutional code operating with Bit Interleaver based on the properties of implant-to-body surface channel. To analyze the performance of the two Error Correct Coding (ECC) schemes, we performed simulations in terms of Bit Error Rate (BER) and power consumption on MATLAB and FPGA platform, respectively. The simulation results proved that with appropriate constraint length, convolutional code has a better performance not only in BER, but also in minimization of resources and power consumption.展开更多
目的:分析并评价维持性血液透析病人动静脉内瘘失功的风险预测模型,以期为临床提供参考依据。方法:计算机检索Embase、the Cochrane Library、Web of Science、PubMed等英文数据库及中国知网、中国生物医学文献数据库、万方数据库等中...目的:分析并评价维持性血液透析病人动静脉内瘘失功的风险预测模型,以期为临床提供参考依据。方法:计算机检索Embase、the Cochrane Library、Web of Science、PubMed等英文数据库及中国知网、中国生物医学文献数据库、万方数据库等中文数据库中有关维持性血液透析病人动静脉内瘘失功预测模型的文献,由2名具有循证能力的研究者按照文章的纳入、排除标准提取文献,再根据预测模型研究的偏倚风险评估工具对纳入的文献进行偏倚风险及适用性评价。结果:共纳入6篇动静脉内瘘失功风险预测模型,其中回顾性队列研究3篇,前瞻性队列研究3篇;单中心研究5篇,多中心研究1篇,预测动静脉早期失功的模型3篇,预测动静脉内瘘晚期失功模型3篇。6个模型的受试者工作特征曲线下面积(AUC)均大于0.700,纳入模型中预测动静脉内瘘失功的预测因子最多的是年龄、血压、有无糖尿病、置管史、吻合的动脉静脉血管直径及病人的钙磷乘积等,6项研究使用性较好,但是均存在一定的偏倚风险。结论:维持性血液透析病人动静脉内瘘失功风险预测模型的研究尚处在发展阶段,未来临床工作者应该开发性能好、偏倚风险较低的预测模型,进行外部或内部验证,用于临床。展开更多
文摘Hybrid Si/SiC switches constituting a parallel connection of a lower current rated SiC MOSFET and a higher current rated Si IGBT are becoming very attractive solution for designing high frequency and high-power density power electronic converters.Due to the complementary nature of Si IGBT devices(smaller inverter cost and smaller conduction loss)and SiC devices(smaller switching loss and higher junction temperature capability),these novel switch device configurations enable a good tradeoff between cost and efficiency for high power converter applications.One such recent application of hybrid Si/SiC switches for efficiency-cost optimization is an Si/SiC hybrid switch based ANPC inverter proposed in Ref.[30].In Ref.[30]the topology structure,modulation strategy and the efficiency-cost benefits of the proposed ANPC inverter is presented.In this paper a precise electro-thermal power loss model for this ANPC inverter topology will be presented based on the modulation strategy of the inverter and the operating characteristics of the Si/SiC hybrid switches.The power loss model development takes into account how the current sharing between the two internal devices of the Si/SiC hybrid switches and their corresponding gate control method affects their power loss.A brief introduction to the topology structure and operation principle of the Si/SiC based ANPC inverter is first highlighted to provide context for readers and then a detailed description of the proposed electro-thermal power loss model is presented.The precision of the electro-thermal power loss model introduced in this paper is then validated using experimentally measured energy loss,device temperature and inverter efficiency data.
文摘The classical minimization of power losses in transmission lines is dominated by artificial intelligence techniques, which do not guarantee global optimum amidst local minima. Revolutionary and evolutionary techniques are encumbered with sophisticated transformations, which weaken the techniques. Power loss minimization is crucial to the efficient design and operation of power transmission lines. Minimization of losses is one way to meet steady grid supply, especially at peak demand. Thus, this paper has presented a gradient technique to obtain optimal variables and values from the power loss model, which efficiently minimizes power losses by modifying the traditional power loss model that combines Ohm and Corona losses. Optimality tests showed that the unmodified model does not support the minimization of power losses on transmission lines as the Hessian matrix portrayed the maximization of power losses. However, the modified model is consistent with the gradient method of optimization, which yielded optimum variables and values from the power loss model developed in this study. The unmodified (modified) models for Bujagali-Kawanda 220 kV and Masaka West-Mbarara North 132 kV transmission lines in Uganda showed maximum power losses of 0.406 (0.391) and 0.452 (0.446) kW/km/phase respectively. These results indicate that the modified model is superior to the unmodified model in minimizing power losses in the transmission lines and should be implemented for the efficient design and operation of power transmission lines within and outside Uganda for the same transmission voltages.
文摘With the explosive development of wireless communication and low power embedded techniques, Body Area Network (BAN) has opened up new frontiers in the race to provide real-time health monitoring. IEEE 802 has established a Task Group called IEEE 802.15.6 inNovember 2007 and aims to establish a communication standard optimized for low power, high reliability applied to medical and non-medical application for BANs. This paper overviews the path loss model and the communication scheme for implant-to-body surface channel presented by IEEE 802.15.6 standard. Comparing with the standard scheme where BCH (Bose-Chaudhuri-Hochquenghem) code is employing, we propose a new coding solution using convolutional code operating with Bit Interleaver based on the properties of implant-to-body surface channel. To analyze the performance of the two Error Correct Coding (ECC) schemes, we performed simulations in terms of Bit Error Rate (BER) and power consumption on MATLAB and FPGA platform, respectively. The simulation results proved that with appropriate constraint length, convolutional code has a better performance not only in BER, but also in minimization of resources and power consumption.
文摘目的:分析并评价维持性血液透析病人动静脉内瘘失功的风险预测模型,以期为临床提供参考依据。方法:计算机检索Embase、the Cochrane Library、Web of Science、PubMed等英文数据库及中国知网、中国生物医学文献数据库、万方数据库等中文数据库中有关维持性血液透析病人动静脉内瘘失功预测模型的文献,由2名具有循证能力的研究者按照文章的纳入、排除标准提取文献,再根据预测模型研究的偏倚风险评估工具对纳入的文献进行偏倚风险及适用性评价。结果:共纳入6篇动静脉内瘘失功风险预测模型,其中回顾性队列研究3篇,前瞻性队列研究3篇;单中心研究5篇,多中心研究1篇,预测动静脉早期失功的模型3篇,预测动静脉内瘘晚期失功模型3篇。6个模型的受试者工作特征曲线下面积(AUC)均大于0.700,纳入模型中预测动静脉内瘘失功的预测因子最多的是年龄、血压、有无糖尿病、置管史、吻合的动脉静脉血管直径及病人的钙磷乘积等,6项研究使用性较好,但是均存在一定的偏倚风险。结论:维持性血液透析病人动静脉内瘘失功风险预测模型的研究尚处在发展阶段,未来临床工作者应该开发性能好、偏倚风险较低的预测模型,进行外部或内部验证,用于临床。