摘要：
模块化多电平换流器（Modular Multilevel Converters,MMC）具有维护方便，易扩容等优点，在柔性直流输电（High Voltage Direct Current,HVDC）、电网谐波治理等领域得到广泛应用。但其子模块中的分散电容，在实际使用中会产生谐波环流，影响了模块电容电压波动，降低换流器的安全裕度和经济性。文章首先介绍了MMC组成结构；然后通过建立桥臂瞬时功率方程，分析环流产生机理，并得出桥臂环流中存在二次谐波分量的结论，通过控制直流侧电压与桥臂等效输出电压之间的差值，调节环流中的谐波分量，进而将现阶段国内、外环流抑制方法分为间接环流抑制方法与直接环流抑制方法，并对环流的利用也做了相关阐述。最后对环流抑制存在的问题进行总结与展望。
作者机构：
[刘康; 李彬; 苏盛] Hunan Key Laboratory of Smart Grid Operation and Control, Changsha University of Science and Technology, Changsha;410114, China;[刘鑫] Marketing Service Center of State Grid Hunan Electric Power Company (Metering Center), Changsha;[张蓬鹤; 薛阳] China Electric Power Research Institute Co., Ltd., Beijing;100180, China
通讯机构：
[Su, S.] H;Hunan Key Laboratory of Smart Grid Operation and Control, China
作者机构：
[Xu, Jun; Zheng, Kaihong; Pan, Fusheng] Guangdong Acad Sci, Inst New Mat, Guangzhou 510650, Peoples R China.;[Xu, Jun; Zhang, Weiwen] South China Univ Technol, Natl Engn Res Ctr Near Net Shape Forming Metall M, Guangzhou 510641, Peoples R China.;[Jiang, Bin; Pan, Fusheng] Chongqing Univ, Coll Mat Sci & Engn, State Key Lab Mech Transmiss, Chongqing 400044, Peoples R China.;[Zhao, Jun] Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413002, Peoples R China.;[Xu, Jun] Chang Xing St 363, Guangzhou, Peoples R China.
通讯机构：
[Xu, J ] C;[Jiang, B ] S;Sha Zheng St 174, Chongqing, Peoples R China.;Chang Xing St 363, Guangzhou, Peoples R China.
作者机构：
[Zhao, Jun] Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413002, Peoples R China.;[Jiang, Bin; Yuan, Ming; Huang, Guangsheng; Pan, Fusheng] Chongqing Univ, Coll Mat Sci & Engn, State Key Lab Mech Transmission, Chongqing 400044, Peoples R China.;[Wang, Qinghang] Yangzhou Univ, Sch Mech Engn, Yangzhou 225127, Jiangsu, Peoples R China.;[Chai, Yanfu] Shaoxing Univ, Sch Mech & Elect Engn, Shaoxing 312000, Peoples R China.
通讯机构：
[Bin Jiang] S;State Key Laboratory of Mechanical Transmissions, College of Materials Science and Engineering, Chongqing University, Chongqing, China
摘要：
Li addition is verified to be an effective method to increase the room temperature ductility and formability of Mg alloys. In the present study, the microstructure, texture, and tensile properties of the extruded Mg-1Zn-xLi (wt%, x = 0, 1, 3, 5) alloy sheets were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). It was found that Li addition resulted in the grain coarsening and the development of new transverse direction (TD)-tilting and 〈
$$10\bar{1}0$$
〉 parallel to extrusion direction textures, which was related to the improved dynamic recrystallization and the increased prismatic slip during extrusion. The Mg-1Zn−5Li sheet showed the weakest texture, which contained both basal and TD-tilting oriented grains. No additional phase was formed with Li addition. The yield strength of Mg-1Zn-xLi sheets gradually decreased with increasing Li content, which was mainly related to the grain coarsening and texture weakening. In addition, the ductility of the Mg-1Zn-xLi sheet was remarkably enhanced by Li addition. The elongation of the Mg-1Zn-5Li sheet was 30.3% along the TD, which was three times than that of Mg-1Zn sheet. Microstructural analysis implied that this significant ductility enhancement was associated with the improvement activation of prismatic and basal slips during the tensile tests. This study may provide insights into the development of high-ductility, low-density Mg-Zn-Li based alloys.
作者机构：
[Zhai, Haowei; Xia, Hongbo] School of Mechanical Engineering, Yangzhou University, Yangzhou 225127, China;[Liu, Lintao; Jiang, Bin; Pan, Fusheng] National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China;[Zhao, Jun] School of Mechanical and Electrical Engineering, Hunan City University, Yiyang 413002, China;[Chen, Daolun] Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON M5B 2K3, Canada;[Wang, Qinghang] School of Mechanical Engineering, Yangzhou University, Yangzhou 225127, China<&wdkj&>National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China
通讯机构：
[Qinghang Wang] S;[Bin Jiang] N;National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China<&wdkj&>School of Mechanical Engineering, Yangzhou University, Yangzhou 225127, China<&wdkj&>National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China
摘要：
Designing and developing the Mg alloys with low cost and high performance is of the great significance. Novel Mg-1Bi-xMn (x = 0, 1 and 2 wt.%) extruded alloys, in this work, were fabricated at different extrusion temperatures (220, 250 and 300 °C). The effects of extrusion temperature and Mn addition on the microstructures and mechanical properties of extruded alloys at room temperature were investigated. The results showed that decreasing the extrusion temperature could refine the average grain size, weaken the basal fiber texture intensity and improve the microstructural homogeneity of extruded alloys. When the Mn element was added to the Mg-1Bi alloy, the average grain size further reduced. Simultaneously, the number fraction of low angle grain boundaries (LAGBs) increased, along with the occurrence of regions without dynamic recrystallization (unDRX). The combined effects of grain refinement and coarse unDRXed structure made the textures of the extruded Mg-1Bi-xMn alloys never obviously change. Besides few large size un-dissolved second phases, fine Mg3Bi2 and α-Mn phases were precipitated in the extruded Mg-1Bi-xMn alloys and partial nano-scale α-Mn particles pined at grain boundaries (GBs) to effectively impede the migration of GBs for grain refinement. Microstructural variations determined the extruded Mg-1Bi-2Mn alloy to exhibit the highest yield strength of ∼ 319.2 MPa with the appropriate elongation-to-failure of ∼ 13% at the extrusion temperature of 220 °C, and they enabled the extruded Mg-1Bi-1Mn alloy to show the highest elongation-to-failure of ∼ 26% without the obvious loss of yield strength of ∼ 252.1 MPa.
作者机构：
[魏文; 戴双凤] School of Economics and Management, Changsha University of Science and Technology, Changsha;410076, China;School of Economics and Management, Hunan University of Science and Technology, Yueyang;414000, China;[姜飞; 陈磊] School of Electrical and Information Engineering, Changsha University of Science and Technology, Changsha
摘要：
The influence of Mn content on the microstructure, tensile properties and strain-hardening behaviors of extruded Mg-1Gd-0.5Zn-xMn (x=0, 0.3 and 1, wt.%) alloy sheets was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). The results show that the completely recrystallized grain structure and the extrusion direction (ED)-titling texture are observed in all the extruded sheets. The mean grain size and weakened ED-titling texture of the extruded sheets are gradually reduced with increasing Mn content. This is primarily associated with the formation of new fine a-Mn particles by Mn addition. Tensile properties show that the addition of Mn also leads to the improvement of yield strengths, ultimate tensile strengths and elongations of the extruded Mg-1Gd-0.5Zn-xMn sheets, which is mainly due to the fine grains and alpha-Mn particles. In addition, the Mg-1Gd-0.5Zn-1Mn sheet has the lowest strain-hardening exponent and the best hardening capacity among all prepared Mg-1Gd-0.5Zn-xMn sheets.
摘要：
目的应用动态信号分析法评估无创正压通气(NPPV)时不同吸气努力对肺力学模型呼吸力学参数测算的影响。方法选择ASL5000机械模拟肺模拟体重为65~70 kg的半卧位健康成年人、慢性阻塞性肺疾病和急性呼吸窘迫综合征患者。吸气压力(P_(mus))分别为0、5.0、10.0和15.0 cm H_(2)O。Respironics V60呼吸机以自主/时间控制模式运行,呼气末正压为5.0 cm H_(2)O,调整P_(mus)使呼吸机输出潮气量为7.0 mL/kg,后备通气频率为10次/min。收集系统泄漏量为25~28 L/min时的通气参数变化并计算呼吸力学参数系统顺应性(C_(rs))和气道阻力(Raw)。结果随着P_(mus)增大,三种肺力学模型的驱动压(DP)逐渐减小;P_(mus)超过10.0 cm H_(2)O后健康成年人模型的呼出潮气量显著超过7.0 mL/kg,DP降至1.0 cm H_(2)O。高水平P_(mus)时C_(rs)呈过高测算,而Raw测算值显著降低。低水平P_(mus)时慢性阻塞性肺疾病和急性呼吸窘迫综合征模型的呼气阻力(R_(exp))和C_(rs)测算误差≤10%,不同P_(mus)水平时吸气阻力(Rinsp)测算值均显著低于预设值(P<0.01)。结论通过应用动态信号分析法,可实现NPPV时在不阻断自主呼吸条件下连续监测C_(rs)和Raw(尤其是R_(exp)),过强的P_(mus)会导致呼吸力学测算误差增大。
作者机构：
[陈长青; 阳同光] College of Mechanical and Electrical Engineering, Hunan City University, Yiyang;413000, China;Hunan Key Laboratory of Energy Perception and Edge Computing in Smart City, Yiyang;[陈长青; 阳同光] 413000, China<&wdkj&>Hunan Key Laboratory of Energy Perception and Edge Computing in Smart City, Yiyang;[陈长青; 阳同光] 413000, China
关键词：
柔性负荷;合同策略;削峰填谷;时序互补;光伏消纳
摘要：
具有"虚拟储能"作用的柔性负荷能够从时空上改变原有负荷分布,降低峰谷差,然而现有规划并未对其进行深入研究。为此,通过构建柔性负荷响应模型,并提出优先将高峰时段柔性负荷转移至光伏出力高峰期的合同策略,进而提高光伏利用率。其次,构建计及柔性负荷的储能和光伏协调规划模型,以便充分发挥柔性负荷"削峰填谷"及光储时序互补作用。最后,通过对10k V 37节点实际配电网进行仿真。结果表明,从经济角度分析,柔性负荷相比储能更具优势,能有效降低储能容量配置和提高光伏消纳能力。
通讯机构：
[Keju JI] J;Jiangsu Provincial Key Laboratory of Bionic Functional Materials, College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
摘要：
Bionic adhesives with tip-expanded microstructural arrays have attracted considerable interest owing to their high adhesive performance at low preloads. Their mainstream manufacturing method is molding. Due to most molds are made of silicon or silicon-based soft templates, and have poor wear resistant or vulnerability to high temperature, limiting their use in large-scale manufacturing. Nickel is widely used as an embossing mold in the micro/nano-imprint industrial process owing to its good mechanical properties. However, the processing of metal molds for the fabrication of tip-expanded microstructural arrays is extremely challenging. In this study, using electrodeposition techniques, the shape of the micropores is modified to obtain end-controlled pores. The effect of the non-uniformity of the electric field on the microporous morphology in the electrodeposition process is systematically investigated. Furthermore, the mechanism of non-uniformity evolution of the microporous morphology is revealed. The optimized microporous metal array is used as a mold to investigate the cavity evolution laws of the elastic cushions under pre-load during the manufacturing process. As a result, typical bionic adhesives with tip-expansion are obtained. Moreover, corresponding adhesion mechanics are analyzed. The results show that electrochemical modifications have broad application prospects in the fabrication of tip-expanded microstructures, providing a new method for the large-scale fabrication of bionic adhesives based on metal molds.
作者机构：
[袁越阳; 马小林] School of Mechanical and Electrical Engineering, Hunan City University, Yiyang;Hunan;413099, China;[孙建国] Suzhou Curative Medical Technical Company, Suzhou;Jiangsu
摘要：
目的观察经口鼻面罩实施压力支持通气(PSV)时不同压力支持(PS)水平对肺力学模型呼吸力学特性参数测算准确性的影响。方法使用ASL5000肺模拟器模拟慢性阻塞性肺疾病患者,设置系统顺应性(C_(rs))为50 mL/cm H_2O,气道阻力(R_(aw))为20 cm H_2O/(L·s),吸气时间为1.6 s,呼吸频率为15次/min。Respironics V60呼吸机以S/T模式运行,呼气末正压为5 cm H_2O,PS水平分别为5、10、15、20和25 cm H_2O,后备通气频率为10次/min。收集在系统泄漏量为25~28 L/min时的通气参数变化并采用新型动态法测算C_(rs)以及吸气和呼气阻力(R_(insp)和R_(exp))。结果PS为5、10和20 cm H_2O时,潮气量(V_T)分别为(281.45±4.26)、(456.81±1.91)和(747.45±3.22)mL(P<0.01);PS为25 cm H_2O时出现明显人机不同步现象,呼吸机无法提供同步通气。PS为5 cm H_2O时吸呼切换流量比(CC)仅为(15.62±3.11)%,PS增至20 cm H_2O时CC增高至(24.50±0.77)%(P<0.01)。 PS<20 cm H_2O时始终存在吸呼过早切换,但随着PS水平的增高过早切换逐渐减轻,PS为20 cm H_2O时出现延迟切换,切换延迟时间为(33.60±15.91)ms(P<0.01)。PS为10 cm H_2O时C_(rs)的测算值为(46.19±1.57)mL/cm H_2O,与模拟肺设置值接近;高水平PS时C_(rs)测算值逐渐减小。PS≥15 cm H_2O后,R_(insp)和R_(exp)的测算值接近模拟肺设置值。结论新型动态法技术可在无创通气状态、不阻断患者自主呼吸条件下持续测算其呼吸力学特性参数。高水平PS通气时高吸气流量对测算R_(aw)有利,而C_(rs)的测算受实际V_T的影响。
