The cutting performance of particulate reinforced me tallic matrix composites(PRMMCs) SiC p/Al in ultrasonic vibration cutting and c ommon cutting with carbide tools and PCD tools was researched in the paper. Mic rost...The cutting performance of particulate reinforced me tallic matrix composites(PRMMCs) SiC p/Al in ultrasonic vibration cutting and c ommon cutting with carbide tools and PCD tools was researched in the paper. Mic rostructure of machined surface was described, the relation between cutting para meters and surface roughness was presented, and characteristic of the surface re mained stress was also presented. Furthermore, wear regularity and abrasion resi stance ability of tools in ultrasonic vibration cutting and common cutting o f PRMMCs were discussed in detail. The test results show: (1) The surface config urations are obviously different when using different tools to machine such PRMM Cs. The surface machined with carbide tools looks luminous and orderly and there are seldom surface defects on it. The reason is that the soft basal body is apt to flow during cutting, therefore a layer of Al matrix film covers machined sur face. On the contrary, the surface machined with PCD tools looks lackluster. But the profile of machined surface is very clear. Superfine grooves, pits and blac k reinforce particulates can be seen easily without obvious Al film. (2) Because of unstable cutting process in common cutting, the surface is easy to produce s ome defects such as burrs, built-up edges and so on so that the quality of surf ace becomes very poor. Vibration cutting can reduce the influence of tearing, pl astic deformation and built-up edge in cutting and can restrain flutter so as t o make cutting process more stable. Therefore, surface roughness of vibration cu tting is better than that of common cutting. (3) There is an optimum value of fe ed rate in vibration cutting of PRMMCs due to the influence of material characte ristics. Whether feed rate is more than or less than this optimum value, surface roughness will increase. (4) According to analyzing the wear rate of tools in v ibration cutting PRMMCs, it can be concluded that abrasion resistance of tools w ill be improved remarkably when vibration cutting composites have a lower pe rcentage of reinforce particulate. If the percentage of reinforce particulate is higher, the influence on abrasion resistance of carbide tool in vibration cut ting will not be obvious. The research result indicates that vibration cutting effect has a close relation with material characteristics.展开更多
丙型肝炎病毒(hepatitis C virus,HCV)感染引起的丙型肝炎慢性率高达80%。不积极干预,大部分患者将发展为肝硬化或肝细胞癌[1]。据世界卫生组织(World Health Organization,WHO)估计[2],2019年全球大约有5800万慢性丙型肝炎(CHC)患者,...丙型肝炎病毒(hepatitis C virus,HCV)感染引起的丙型肝炎慢性率高达80%。不积极干预,大部分患者将发展为肝硬化或肝细胞癌[1]。据世界卫生组织(World Health Organization,WHO)估计[2],2019年全球大约有5800万慢性丙型肝炎(CHC)患者,每年新发感染HCV人数约为150万。据中国疾控中心报告的数据,自2012年起,我国每年新发HCV感染人数维持在20万左右。WHO提出了2030年消除病毒性肝炎公共卫生危害[3]的全球性卫生战略目标,即HCV感染诊断率>90%和治疗率>80%。根据非营利性Polaris报告的HCV感染数据[4],全球HCV感染诊断率为33%,治疗率为15%。中国HCV感染诊断率为30%,而治疗率仅为11%。就我国约1000万HCV感染患者而言,有大约700万未被发现,890万例患者未接受治疗。虽然尚无HCV疫苗预防,但可通过口服直接抗病毒药物(direct acting antivirals,DAAs)达到治愈,药物治疗治愈率均在95%以上,且治疗过程简单,仅需要口服3~6个月药物即可。至目前为止,消除HCV的治疗条件已成熟,核心问题是如何去发现HCV感染患者。在2017年,欧洲肝病学会提出了HCV微消除战略,即先将国家消除HCV感染的目标划分为较小的目标,如针对一个确定的人口或地理区域消除,即针对群体性消除[5]。根据这一概念,HCV微消除可以扩展到医院相关微消除、区域性筛查、重点特殊人群微消除等领域。当前,有很多成功的HCV微消除案例,本文对上述案例进行总结,为临床实现HCV感染消除提供参考意见。展开更多
随着能源互联网战略的深入实施,可再生能源与微电网的参与度不断攀升,系统中不确定性因素显著增加,各参与主体间的合作与竞争关系变得愈发错综复杂。从垂直和水平两个层面建立了电网、服务商及多微电网混合博弈双层电能交易体系。在垂...随着能源互联网战略的深入实施,可再生能源与微电网的参与度不断攀升,系统中不确定性因素显著增加,各参与主体间的合作与竞争关系变得愈发错综复杂。从垂直和水平两个层面建立了电网、服务商及多微电网混合博弈双层电能交易体系。在垂直层面提出主从博弈的思想,以服务商为主导者、微电网为从属者。构建不确定性问题分阶段优化的分段鲁棒优化模型,实现不确定性的差异化调度,提高鲁棒优化的灵活性。利用布尔-列和约束生成(Bool-Column and constraint generation,B-C&CG)算法求解模型,并把整个模型分为主问题和子问题:主问题优化电价不确定性问题,子问题优化源荷不确定问题。在水平层面搭建纳什谈判模型,通过交替方向乘子(alternating direction method of multipliers,ADMM)算法求解水平层面微电网之间的电能交互模型。利用分布式求解方法得出交易价格策略,再结合拉格朗日乘子法,交替优化各分部并更新乘子,得出各微电网之间的最佳交易电价。仿真结果表明,所提方案兼顾了系统的鲁棒性、经济性及灵活性,缩减了各微电网的成本并充分保护了各微网的隐私。展开更多
文摘The cutting performance of particulate reinforced me tallic matrix composites(PRMMCs) SiC p/Al in ultrasonic vibration cutting and c ommon cutting with carbide tools and PCD tools was researched in the paper. Mic rostructure of machined surface was described, the relation between cutting para meters and surface roughness was presented, and characteristic of the surface re mained stress was also presented. Furthermore, wear regularity and abrasion resi stance ability of tools in ultrasonic vibration cutting and common cutting o f PRMMCs were discussed in detail. The test results show: (1) The surface config urations are obviously different when using different tools to machine such PRMM Cs. The surface machined with carbide tools looks luminous and orderly and there are seldom surface defects on it. The reason is that the soft basal body is apt to flow during cutting, therefore a layer of Al matrix film covers machined sur face. On the contrary, the surface machined with PCD tools looks lackluster. But the profile of machined surface is very clear. Superfine grooves, pits and blac k reinforce particulates can be seen easily without obvious Al film. (2) Because of unstable cutting process in common cutting, the surface is easy to produce s ome defects such as burrs, built-up edges and so on so that the quality of surf ace becomes very poor. Vibration cutting can reduce the influence of tearing, pl astic deformation and built-up edge in cutting and can restrain flutter so as t o make cutting process more stable. Therefore, surface roughness of vibration cu tting is better than that of common cutting. (3) There is an optimum value of fe ed rate in vibration cutting of PRMMCs due to the influence of material characte ristics. Whether feed rate is more than or less than this optimum value, surface roughness will increase. (4) According to analyzing the wear rate of tools in v ibration cutting PRMMCs, it can be concluded that abrasion resistance of tools w ill be improved remarkably when vibration cutting composites have a lower pe rcentage of reinforce particulate. If the percentage of reinforce particulate is higher, the influence on abrasion resistance of carbide tool in vibration cut ting will not be obvious. The research result indicates that vibration cutting effect has a close relation with material characteristics.
文摘丙型肝炎病毒(hepatitis C virus,HCV)感染引起的丙型肝炎慢性率高达80%。不积极干预,大部分患者将发展为肝硬化或肝细胞癌[1]。据世界卫生组织(World Health Organization,WHO)估计[2],2019年全球大约有5800万慢性丙型肝炎(CHC)患者,每年新发感染HCV人数约为150万。据中国疾控中心报告的数据,自2012年起,我国每年新发HCV感染人数维持在20万左右。WHO提出了2030年消除病毒性肝炎公共卫生危害[3]的全球性卫生战略目标,即HCV感染诊断率>90%和治疗率>80%。根据非营利性Polaris报告的HCV感染数据[4],全球HCV感染诊断率为33%,治疗率为15%。中国HCV感染诊断率为30%,而治疗率仅为11%。就我国约1000万HCV感染患者而言,有大约700万未被发现,890万例患者未接受治疗。虽然尚无HCV疫苗预防,但可通过口服直接抗病毒药物(direct acting antivirals,DAAs)达到治愈,药物治疗治愈率均在95%以上,且治疗过程简单,仅需要口服3~6个月药物即可。至目前为止,消除HCV的治疗条件已成熟,核心问题是如何去发现HCV感染患者。在2017年,欧洲肝病学会提出了HCV微消除战略,即先将国家消除HCV感染的目标划分为较小的目标,如针对一个确定的人口或地理区域消除,即针对群体性消除[5]。根据这一概念,HCV微消除可以扩展到医院相关微消除、区域性筛查、重点特殊人群微消除等领域。当前,有很多成功的HCV微消除案例,本文对上述案例进行总结,为临床实现HCV感染消除提供参考意见。
文摘随着能源互联网战略的深入实施,可再生能源与微电网的参与度不断攀升,系统中不确定性因素显著增加,各参与主体间的合作与竞争关系变得愈发错综复杂。从垂直和水平两个层面建立了电网、服务商及多微电网混合博弈双层电能交易体系。在垂直层面提出主从博弈的思想,以服务商为主导者、微电网为从属者。构建不确定性问题分阶段优化的分段鲁棒优化模型,实现不确定性的差异化调度,提高鲁棒优化的灵活性。利用布尔-列和约束生成(Bool-Column and constraint generation,B-C&CG)算法求解模型,并把整个模型分为主问题和子问题:主问题优化电价不确定性问题,子问题优化源荷不确定问题。在水平层面搭建纳什谈判模型,通过交替方向乘子(alternating direction method of multipliers,ADMM)算法求解水平层面微电网之间的电能交互模型。利用分布式求解方法得出交易价格策略,再结合拉格朗日乘子法,交替优化各分部并更新乘子,得出各微电网之间的最佳交易电价。仿真结果表明,所提方案兼顾了系统的鲁棒性、经济性及灵活性,缩减了各微电网的成本并充分保护了各微网的隐私。
