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进气压力对真空发生器性能的影响
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作者 刘宝 韩威震 +1 位作者 张业明 张柯 《真空科学与技术学报》 EI CAS CSCD 北大核心 2019年第4期304-309,共6页
为研究进气压力对真空发生器性能的影响,利用Fluent软件对真空发生器内部流场进行数值模拟。仿真范围内,通过对真空口处压强、引射效率、气体沿轴线的速度与压强,以及发生器失效的讨论分析,得到如下结论:真空口封闭的瞬态条件下,对真空... 为研究进气压力对真空发生器性能的影响,利用Fluent软件对真空发生器内部流场进行数值模拟。仿真范围内,通过对真空口处压强、引射效率、气体沿轴线的速度与压强,以及发生器失效的讨论分析,得到如下结论:真空口封闭的瞬态条件下,对真空口处压强而言,进气压力存在临界值与最优值,超过临界值后真空口处压强出现周期性震荡,达到最优值时,能以最优进气压力达到高于该压力所能维持的真空度;基于等压混合假设的稳态条件下,对引射流量、引射效率而言,分别存在相应的进气压力最优值,并于对应最优值时达到最大的引射流量与引射效率。 展开更多
关键词 真空 数值仿真 进气压力 震荡 真空度
水环真空泵工作效率提升探索与应用 预览
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作者 刘洋 《电力系统装备》 2019年第15期143-144,共2页
机组运行真空关系着发电机组的安全性和经济性,特别在夏季高温时段,许多火力发电厂由于真空问题无法接带高负荷,无法为电网提供强有力的保障。真空泵作为机组真空系统重要组成部分,其运行工况,出力情况对运行真空有着至关重要的意义。... 机组运行真空关系着发电机组的安全性和经济性,特别在夏季高温时段,许多火力发电厂由于真空问题无法接带高负荷,无法为电网提供强有力的保障。真空泵作为机组真空系统重要组成部分,其运行工况,出力情况对运行真空有着至关重要的意义。本文着力研究水环式真空泵工作时影响其效率的诸多方面,通过分析改造,最终提高水环真空泵的工作效率。 展开更多
关键词 背压 真空泵 效率
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Water-based superlubricity in vacuum
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作者 Chen XIAO Jinjin LI +6 位作者 Lei CHEN Chenhui ZHANG Ningning ZHOU Tao QING Linmao QIAN Jiyang ZHANG Jianbin LUO 《摩擦(英文版)》 CSCD 2019年第2期192-198,共7页
This study achieved water‐based superlubricity with the lubrication of H3PO4 solution in vacuum(highest vacuum degree <10^–4 torr) for the first time by performing a pre‐running process in air before running in ... This study achieved water‐based superlubricity with the lubrication of H3PO4 solution in vacuum(highest vacuum degree <10^–4 torr) for the first time by performing a pre‐running process in air before running in vacuum.The stable water‐based superlubricity was sustainable in vacuum(0.02 torr) for 14 h until the test was stopped by the user for non‐experimental factor.A further analysis suggested that the superlubricity may be attributed to the phosphoric acid–water network formed in air,which can efficiently lock water molecules in the liquid lubricating film even in vacuum owing to the strong hydrogen bond interaction.Such capability to lock water is strongly affected by the strength of hydrogen bond and environmental conditions.The realization of water‐based superlubricity with H3PO4 solution in vacuum can lead to its application in space environment. 展开更多
关键词 FRICTION WATER-BASED SUPERLUBRICITY VACUUM phosphoric ACID
真空镀膜设备的简易快捷酒精检漏的有效性研究
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作者 靳朋礼 巩春志 +6 位作者 孔营 张鑫 马玉山 刘海波 何涛 岳玲 田修波 《真空》 CAS 2019年第5期69-73,共5页
由于缺乏统一规范,如何用酒精高效快速的确定漏点一直是真空镀膜企业重点关注的问题。本文通过对真空镀膜设备的喷酒精检漏的有效性开展研究,并用氦质谱检漏进行验证与标定,系统研究了气压工作范围、抽气速率、漏点结构形式三个主要影... 由于缺乏统一规范,如何用酒精高效快速的确定漏点一直是真空镀膜企业重点关注的问题。本文通过对真空镀膜设备的喷酒精检漏的有效性开展研究,并用氦质谱检漏进行验证与标定,系统研究了气压工作范围、抽气速率、漏点结构形式三个主要影响因素。得出如下结论:真空室气压低于5.0×10-3Pa时喷酒精不能够检出漏点,气压在5.0×10-3Pa~9.9×10-3Pa范围酒精检漏的气压变化趋势为先下降后上升再下降,在气压1.0×10-2Pa~9.9×10-2Pa范围里喷完酒精后,真空室内的气压变化趋势是先略微下降后上升再下降,在1.0×1010-1Pa~9.9×1010-1Pa气压范围,由于漏点尺寸大,喷酒精后,气压无下降,直接先上升后下降;相比两个分子泵,一个分子泵工作检漏时,漏点检出时间长且易漏检,所以在实际泵速较小或真空室较大的真空系统检漏时要特别注意,防止漏检。简单结构漏点喷酒精检漏用时短易检出,而结构复杂的漏点气压反应所用时间长易漏检。以上研究结果为真空生产和应用单位采用酒精高效简易检漏提供了有效指导。 展开更多
关键词 真空 检漏 酒精 氦质谱检漏仪
Improvement of quantitative analysis of molybdenum element using PLS-based approaches for laser-induced breakdown spectroscopy in various pressure environments
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作者 刘佳敏 吴鼎 +4 位作者 付彩龙 海然 于潇 孙立影 丁洪斌 《等离子体科学与技术:英文版》 SCIE EI CAS CSCD 2019年第3期140-147,共8页
An experimental setup has been designed and realized in order to optimize the characteristics of laser-induced breakdown spectroscopy system working in various pressure environments.An approach combined the normalizat... An experimental setup has been designed and realized in order to optimize the characteristics of laser-induced breakdown spectroscopy system working in various pressure environments.An approach combined the normalization methods with the partial least squares(PLS)method are developed for quantitative analysis of molybdenum(Mo)element in the multi-component alloy,which is the first wall material in the Experimental Advanced Superconducting Tokamak.In this study,the different spectral normalization methods(total spectral area normalization,background normalization,and reference line normalization)are investigated for reducing the uncertainty and improving the accuracy of spectral measurement.The results indicates that the approach of PLS based on inter-element interference is significantly better than the conventional PLS methods as well as the univariate linear methods in the various pressure for molybdenum element analysis. 展开更多
关键词 laser induced BREAKDOWN spectroscopy MOLYBDENUM VACUUM NORMALIZATION PARTIAL least SQUARES method quantitative analysis
深部煤层抽采钻孔自然发火原因分析与防治
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作者 齐庆杰 赵尤信 +1 位作者 贾新雷 周新华 《中国安全科学学报》 CAS CSCD 北大核心 2019年第1期37-42,共6页
为避免深部煤层抽采钻孔自然发火,以平煤十矿24100工作面抽采钻孔为研究对象,运用理论计算和数值模拟的方法研究抽采钻孔自然发火的原因。首先通过理论分析确定抽采钻孔封堵段周围破碎区与塑性区半径;通过数值模拟的方法,以煤自然发火... 为避免深部煤层抽采钻孔自然发火,以平煤十矿24100工作面抽采钻孔为研究对象,运用理论计算和数值模拟的方法研究抽采钻孔自然发火的原因。首先通过理论分析确定抽采钻孔封堵段周围破碎区与塑性区半径;通过数值模拟的方法,以煤自然发火最小风速为依据优化24100工作面瓦斯抽采钻孔封孔深度和抽采负压,并与24100工作面现场工程试验结果进行相互验证。结果表明:钻孔封堵段周围塑性区半径0.22 m为抽采钻孔提供了漏气通道,24100工作面抽采钻孔最佳封孔深度为17 m、抽采负压为25 kPa,可以防止抽采钻孔自燃。 展开更多
关键词 抽采钻孔自然发火 最低发火风速 应力分布 数值模拟 封孔深度 抽采负压
制动主缸密封性的研究及应用 预览
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作者 黄建霖 梁容 +1 位作者 张浩 覃跃淳 《装备制造技术》 2019年第3期58-60,共3页
使用气压和真空相互结合的方法代替传统使用制动液的方法对制动主缸的密封性进行检测,检测方法包括动态真空密封性检测、静态真空密封性检测和静态气压密封性检测,不管是补偿孔式制动主缸,还是中心阀式制动主缸,或者是柱塞式制动主缸通... 使用气压和真空相互结合的方法代替传统使用制动液的方法对制动主缸的密封性进行检测,检测方法包括动态真空密封性检测、静态真空密封性检测和静态气压密封性检测,不管是补偿孔式制动主缸,还是中心阀式制动主缸,或者是柱塞式制动主缸通过这三项检测后得到的检测效果更精准更全面,无任何后处理程序,比较适合在生产线上实际使用。 展开更多
关键词 制动主缸 密封性 真空 气压 泄漏量
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A discussion on vacuum polarization correction to the cross-section of e+e-→γ*/ψ→μ+μ-
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作者 金红豆 周利鹏 +1 位作者 张丙新 胡海明 《中国物理C:英文版》 SCIE CAS CSCD 2019年第1期24-35,共12页
Vacuum polarization is a part of the initial-state radiative correction for the cross-section of e^+e^- annihilation processes. In the energy region in the vicinity of narrow resonances J/ψ and ψ(3686), the vacuum p... Vacuum polarization is a part of the initial-state radiative correction for the cross-section of e^+e^- annihilation processes. In the energy region in the vicinity of narrow resonances J/ψ and ψ(3686), the vacuum polarization contribution from the resonant component has a significant effect on the line-shape of the lepton pair production cross-section. This paper discusses some basic concepts and describes an analytical calculation of the cross-section of e^+e^-→γ^*/ψ→μ^+μ^- considering the single and double vacuum polarization effect of the virtual photon propagator. Moreover, it presents some numerical comparisons with the traditional treatments. 展开更多
关键词 electron-positron ANNIHILATION resonance vacuum POLARIZATION CROSS-SECTION
Performance of marine clay stabilised with vacuum pressure:Based on Queensland experience 预览
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作者 Buddhima Indraratna Cholachat Rujikiatkamjorn +1 位作者 Pankaj Baral Jayantha Ameratunga 《岩石力学与岩土工程学报:英文版》 CSCD 2019年第3期598-611,共14页
Stabilising soft marine clay and estuarine soils via vacuum preloading has become very popular in Australasia over the past decades because it is a cost-effective and time-efficient approach.In recent times,new land o... Stabilising soft marine clay and estuarine soils via vacuum preloading has become very popular in Australasia over the past decades because it is a cost-effective and time-efficient approach.In recent times,new land on areas outside but adjacent to existing port amenities,the Fisherman Islands at the Port of Brisbane(POB),was reclaimed to cater for an increase in trade activities.A vacuum preloading method combined with surcharge to stabilise the deep layers of soil was used to enhance the application of prefabricated vertical drains(PVDs).This paper describes the performance of this combined surcharge fill and vacuum system under the embankment and also compares it with a surcharge loading system to demonstrate the benefits of vacuum pressure over conventional fill.The performance of this embankment is also presented in terms of field monitoring data,and the relative performance of the vacuum together with non-vacuum systems is evaluated.An analytical solution to radial consolidation with time-dependent surcharge loading and vacuum pressure is also presented in order to predict the settlement and associated excess pore water pressure(EPWP)of deposits of thick soft clay. 展开更多
关键词 Soft clay PREFABRICATED vertical drains(PVDs) Vacuum CONSOLIDATION Membrane-less SYSTEM MEMBRANE SYSTEM
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Inclusions in melting process of titanium and titanium alloys
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作者 Meng-jiang Cen Yuan Liu +2 位作者 Xiang Chen Hua-wei Zhang Yan-xiang Li 《中国铸造:英文版》 SCIE 2019年第4期223-231,共9页
This paper summarizes melting methods of titanium and titanium alloy, such as vacuum arc melting(VAR) and electron beam cold hearth melting(EBCHM), and the related inclusions formed when using these melting methods. L... This paper summarizes melting methods of titanium and titanium alloy, such as vacuum arc melting(VAR) and electron beam cold hearth melting(EBCHM), and the related inclusions formed when using these melting methods. Low-density inclusions are resulted from contamination of air, and high-density inclusions are caused by refractory elements. The formation process of inclusions was analysed. The removal mechanism of different kinds of inclusions was specified. Low-density inclusions are removed mainly by resolving. This is a comprehensive process containing reaction diffusion. The resolving rate of high-density inclusions is so low that these inclusions are mainly removed by sedimentation. The experiments and physical models of inclusions are detailed. In various melting methods, vacuum arc melting is prominent. However, this method cannot remove inclusions effectively, which usually results in repeat melting. Electron beam cold hearth melting has the best ability of removing inclusions. These results can provide instructions to researchers of titanium and titanium alloys. 展开更多
关键词 TITANIUM INCLUSIONS VACUUM ARC MELTING electron beam cold HEARTH MELTING
柠檬片真空远红外干燥特性及对品质的影响 预览
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作者 杜腾飞 赵丽娟 +1 位作者 王丹丹 李建国 《天津科技大学学报》 CAS 2019年第3期22-26,33共6页
针对新鲜柠檬片在真空远红外干燥过程中的品质变化问题,采用真空远红外干燥箱对柠檬片进行干燥,研究操作温度、操作压力对干燥特性和物料色泽的影响,比较了真空远红外干燥、热风干燥、真空冷冻干燥制备柠檬片的干燥时间、干制品的RGB强... 针对新鲜柠檬片在真空远红外干燥过程中的品质变化问题,采用真空远红外干燥箱对柠檬片进行干燥,研究操作温度、操作压力对干燥特性和物料色泽的影响,比较了真空远红外干燥、热风干燥、真空冷冻干燥制备柠檬片的干燥时间、干制品的RGB强度、维生素C保留率和复水比.结果表明:真空远红外干燥柠檬片的最佳干燥工艺参数为:干燥温度60℃,操作压力2kPa,干燥时间6h.在干燥过程中,操作温度越高,操作压力对干燥速率的影响越不明显(P>0.05);RGB强度均值总体呈下降趋势,当柠檬片含水率低于10%时,柠檬片色泽发生显著变化;真空远红外干燥所得产品的复水比、RGB强度与维生素C保留率均优于热风干燥所得产品,略低于真空冷冻干燥产品. 展开更多
关键词 柠檬片 真空 远红外 干燥 RGB 维生素C
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Optimization of a 3D bioprinting process using ultrashort peptide bioinks 预览
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作者 Zainab Khan Kowther Kahin +4 位作者 Sakandar Rauf Gustavo Ramirez-Calderon Nikolaos Papagiannis Mohammed Abdulmajid Charlotte A.E.Hauser 《国际生物打印期刊》 2019年第1期20-23,共4页
The field of three-dimensional(3D)bioprinting is rapidly emerging as an additive manufacturing method for tissue and organ fabrication.The demand for tissues and organ transplants is ever increasing,although donors ar... The field of three-dimensional(3D)bioprinting is rapidly emerging as an additive manufacturing method for tissue and organ fabrication.The demand for tissues and organ transplants is ever increasing,although donors are not as readily available.Consequently,tissue engineering is gaining much attention to alleviate this problem.The process of achieving well-structured 3D bioprinted constructs using hydrogel bioinks depends on symmetrical precision,regulated flow rates,and viability of cells.Even with the mentioned parameters optimized,the printed structures need additional refining by removing excessive liquids,as peptide hydrogel bioprints encapsulate water.However,it is challenging to eliminate the confined fluids without compromising the printing process.In this paper,we introduced a vacuum system to our 3D bioprinting robotic arm and thus optimized the printing quality for complex and refined 3D scaffolds.Moreover,the proposed vacuum system supports printing with cells.Our results show improved printing resolution which facilitates the printing of higher and more stable structures. 展开更多
关键词 Three-dimensional bioprinting ultrashort peptides BIOMATERIALS bioinks tissue engineering vacuum system
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Detection of 13.8dB squeezed vacuum states by optimizing the interference efficiency and gain of balanced homodyne detection
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作者 孙小聪 王雅君 +2 位作者 田龙 郑耀辉 彭堃墀 《中国光学快报:英文版》 SCIE EI CAS CSCD 2019年第7期83-86,共4页
Squeezed states belong to the most prominent non-classical resources.They have compelling applications in precise measurement, quantum computation, and detection.Here, we report on the direct measurement of 13.8 d B s... Squeezed states belong to the most prominent non-classical resources.They have compelling applications in precise measurement, quantum computation, and detection.Here, we report on the direct measurement of 13.8 d B squeezed vacuum states by improving the interference efficiency and gain of balanced homodyne detection.By employing an auxiliary laser beam, the homodyne visibility is increased to 99.8%.The equivalent loss of the electronic noise is reduced to 0.05% by integrating a junction field-effect transistor(JFET) buffering input and another JFET bootstrap structure in the balanced homodyne detector. 展开更多
关键词 vacuum states INTERFERENCE EFFICIENCY BALANCED HOMODYNE DETECTION
空间摆动电机固体润滑轴承寿命试验研究
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作者 徐增闯 崔维鑫 +1 位作者 刘石神 于远航 《真空科学与技术学报》 EI CAS CSCD 北大核心 2019年第4期354-359,共6页
为验证红外地球敏感器标定组件摆动电机固体润滑轴承设计寿命是否满足在轨10年的指标要求,对2套标定组件进行了地面真空寿命试验验证。寿命试验结束后对标定组件性能进行复测,并对轴承内外圈滚道、滚珠表面进行扫描电镜和能谱仪元素成... 为验证红外地球敏感器标定组件摆动电机固体润滑轴承设计寿命是否满足在轨10年的指标要求,对2套标定组件进行了地面真空寿命试验验证。寿命试验结束后对标定组件性能进行复测,并对轴承内外圈滚道、滚珠表面进行扫描电镜和能谱仪元素成分分析。测试结果表明,标定组件寿命试验期间运行正常,电机电流稳定在0.16-0.18A,摆动电机累计运行寿命超过10年。轴承显微分析结果表明,轴承内外圈滚道、滚珠表面状态良好,无明显点蚀、磨损现象产生,轴承内外圈运动副表面均含有MoS?润滑膜,表明固体润滑状态较好。标定组件寿命试验结果验证了固体润滑方式可满足摆动电机轴承10年寿命要求,可为其它采用固体润滑微小轴承的空间摆动式转动部件长寿命设计提供参考依据。 展开更多
关键词 空间摆动电机 固体润滑 真空 微小轴承 寿命试验
能源植物柳枝稷基因工程研究进展 预览
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作者 曹慧颖 张立军 +3 位作者 阮燕晔 张敖 董小妹 张馨悦 《草业科学》 CAS CSCD 2019年第2期394-401,共8页
柳枝稷(Panicum virgatum)是C4暖季草本植物。具有许多优良的农艺性状,如广泛的地理适应性,耐贫瘠,生产成本低,水利用率高,生物质产量高,易于收获,因此被认为是重要的生物能源作物。通过生物技术对柳枝稷进行遗传改良,对于充分开发柳枝... 柳枝稷(Panicum virgatum)是C4暖季草本植物。具有许多优良的农艺性状,如广泛的地理适应性,耐贫瘠,生产成本低,水利用率高,生物质产量高,易于收获,因此被认为是重要的生物能源作物。通过生物技术对柳枝稷进行遗传改良,对于充分开发柳枝稷的生物质潜能,利用柳枝稷生产生物燃料具有重要意义。本文从柳枝稷遗传转化技术及改良性状的角度综述了柳枝稷的基因工程进展,为培育优良柳枝稷新品种提供参考。 展开更多
关键词 遗传转化 基因型 真空 农杆菌 MIRNA
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Chinese Trauma Surgeon Association for management guidelines of vacuum sealing drainage application in abdominal surgeries-Update and systematic review
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作者 Yang Li Pei-Yuan Li +26 位作者 Shi-Jing Sun Yuan-Zhang Yao Zhan-Fei Li Tao Liu Fan Yang Lian-Yang Zhang Xiang-Jun Bai Jing-Shan Huo Wu-Bing He Jun Ouyang Lei Peng Ping Hu Yan-An Zhu Ping Jin Qi-Feng Shao Yan-Feng Wang Rui-Wu Dai Pei-Yang Hu Hai-Ming Chen Ge-Fei Wang Yong-Gao Wang Hong-Xu Jin Chang-Ju Zhu Qi-Yong Zhang Biao Shao Xi-Guang Sang Chang-Lin Yin 《中华创伤杂志:英文版》 CAS CSCD 2019年第1期1-11,共11页
Vacuum sealing drainage (VSD) is frequently used in abdominal surgeries. However, relevant guidelines are rare. Chin ese Trauma Surge on Associati on orga nized a committee composed of 28 experts across China in July ... Vacuum sealing drainage (VSD) is frequently used in abdominal surgeries. However, relevant guidelines are rare. Chin ese Trauma Surge on Associati on orga nized a committee composed of 28 experts across China in July 2017, aiming to provide an evidence-based recommendation for the application of VSD in abdominal surgeries.Eleven questions regarding the use of VSD in abdominal surgeries were addressed:(1) which type of materials should be respectively chosen for the intraperitoneal cavity, retroperitoneal cavity and superficial incisions?(2) Can VSD be preventively used for a high-risk abdominal incision w让h primary suture?(3) Can VSD be used in severely contaminated/infected abdominal surgical sites?(4) Can VSD be used for temporary abdominal cavity closure under some special conditions such as severe abdominal trauma, infection, liver transplantation and intra-abdominal volume increment in abdominal compartment syndrome?(5) Can VSD be used in abdominal organ inflammation, injury, or postoperative drainage?(6) Can VSD be used in the treatment of intestinal fistula and pancreatic fistula?(7) Can VSD be used in the treatment of intra-abdominal and extra-peritoneal abscess?(8) Can VSD be used in the treatment of abdominal wall wounds, wound cavity, and defects?(9) Does VSD in crease the risk of bleeding?(10) Does VSD increase the risk of intestinal wail injury?(11) Does VSD increase the risk of peritoneal adhesion? Focusing on these questions, evidence-based recommendations were given accordingly. VSD was strongly recommended regarding the questions 2-4. Weak recommendations were made regarding questions 1 and 5-11. Proper use of VSD in abdominal surgeries can lower the risk of infection in abdominal incisions with primary suture, treat severely contaminated/infected surgical sites and facilitate temporary abdominal cavity closure. 展开更多
关键词 GUIDELINE Vacuum SEALING drainage ABDOMINAL surgery
基于纳米铝热剂的MEMS固体微推力器点火实验研究
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作者 卢国权 刘旭辉 +4 位作者 魏延明 杨灵芝 陈明阳 李飞 余西龙 《推进技术》 EI CAS CSCD 北大核心 2019年第4期945-952,共8页
MEMS固体微推力器可以形成单元数量巨大的微推力器阵列,适合低成本微、纳卫星系统,是极具潜力的新型卫星推力器。为研究基于纳米铝热剂的MEMS推力器工作特性,开展了大气和真空点火实验。大气下的燃烧羽流与空气进一步燃烧,导致羽流的发... MEMS固体微推力器可以形成单元数量巨大的微推力器阵列,适合低成本微、纳卫星系统,是极具潜力的新型卫星推力器。为研究基于纳米铝热剂的MEMS推力器工作特性,开展了大气和真空点火实验。大气下的燃烧羽流与空气进一步燃烧,导致羽流的发光持续时间约数ms,远大于真空试验,过估了在真空条件下的推力器作用时间。真空试验获得了动态推力特征和有效工作时间(约250μs),估算推力器的冲量约55μN·s~80μN·s。羽流影响范围的直径约为30mm、流向约70mm,羽流颗粒的运动速度约132m/s。测试结果显示,底部点火先将推进剂挤出喷孔,而后在外部燃烧和爆炸。羽流形貌有两种特征:一种是剧烈爆炸,产生蘑菇云状气体产物;而另一种未产生气状产物。前者的冲量和有效工作时间大于后者。 展开更多
关键词 固体微推力器 纳米铝热剂 真空 动态测试 羽流
真空条件下浓度对LiCl溶液沸腾特性的影响 预览
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作者 韩晓婉 邹同华 +1 位作者 常亚飞 惠庆玲 《化工进展》 EI CAS CSCD 北大核心 2019年第S01期64-69,共6页
沸腾换热是一种高效的换热方式,为研究除湿溶液再生的沸腾换热过程,搭建真空再生沸腾特性测试实验台,对水和质量分数分别为30%、32%、34%的LiCl溶液进行实验研究,得到溶液浓度对溶液沸腾热流密度及沸腾表面传热系数的影响。结果表明,浓... 沸腾换热是一种高效的换热方式,为研究除湿溶液再生的沸腾换热过程,搭建真空再生沸腾特性测试实验台,对水和质量分数分别为30%、32%、34%的LiCl溶液进行实验研究,得到溶液浓度对溶液沸腾热流密度及沸腾表面传热系数的影响。结果表明,浓度升高,表面张力增大,汽化核心数减少;黏度增大,气泡脱离困难,使扰动量减少,溶液的热流密度降低;随着浓度的增大,表面张力增大,气泡生成及脱离阻力增大,对LiCl溶液的扰动程度降低,使溶液的沸腾传热系数减小。温差增大使壁面过热度增大,气泡生成增多,加强对溶液的扰动,使溶液的热流密度及沸腾传热系数增大。 展开更多
关键词 沸腾特性 除湿 真空 汽化核心 对流 腐蚀
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微创旋切与传统手术治疗乳腺多发良性肿块的疗效比较
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作者 殷照才 梅振宇 +6 位作者 盛勇 陈剑平 赵晚君 李琴 冯慧俊 沈忠兵 彭辉 《国际外科学杂志》 2019年第5期329-333,共5页
目的比较微创旋切与传统手术治疗乳腺多发良性肿块的临床效果。方法采用回顾性研究方法,选取2016年7月—2018年2月皖南医学院弋矶山医院收治的158 例乳腺多发良性肿块患者,均为女性;平均年龄(28.3±6.6)岁,范围19~51岁。根据手术方... 目的比较微创旋切与传统手术治疗乳腺多发良性肿块的临床效果。方法采用回顾性研究方法,选取2016年7月—2018年2月皖南医学院弋矶山医院收治的158 例乳腺多发良性肿块患者,均为女性;平均年龄(28.3±6.6)岁,范围19~51岁。根据手术方法的不同将患者分为微创组(n=122)和传统组(n=36),微创组患者采用微创旋切手术治疗,传统组患者采用传统手术治疗。比较两组患者的手术时间、切口数目、平均切口长度、累计切口长度及术后切口愈合时间,术后比较局部血肿、局部感染、乳腺畸形及局部残留发病率,并比较两组患者的满意度。正态分布的计量资料以均数±标准差(Mean±SD)表示,组间比较采用独立样本t检验;非正态分布的计量资料以中位数(四分位间距)[M(P25,P75)]表示,组间比较采用Mann-Whitney U检验;计数资料组间比较采用χ2检验或Fisher确切概率法。结果与传统组比较,微创组患者手术时间短(20.0 min 比40.0 min,Z=-8.590,P<0.001),切口少(1.0 个比2.0 个,Z=-4.423,P<0.001),平均切口长度短(3.8 mm 比35.5 mm,Z=-9.211,P<0.001),累计切口长度短(4.0 mm 比67.2 mm,Z=-9.130,P<0.001),术后切口愈合快(4.0 d 比7.0 d,Z=-9.334,P<0.001);两组患者术后局部血肿(4.1%比2.8%,χ2=0.000,P=1.000)、局部感染(0比2.8%,P=0.228)、乳腺畸形(1.6%比2.8%,χ2=0.000,P=1.000)]和局部残留发病率(0.8%比0,P=1.000)比较差异均无统计学意义;微创组患者术后满意度更高(95.1%比58.3%,P<0.001)。结论与传统手术相比,应用微创旋切手术治疗乳腺多发良性肿块具有手术时间短、切口少、切口长度短、切口愈合快及术后满意度高等多重优势,未明显增加术后并发症,值得临床推广与应用。 展开更多
关键词 乳腺肿瘤 真空 超声检查 外科手术 微创性
Experiment of Hall thruster plume effects on different ground experimental conditions
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作者 SU Yang CAI Guobiao +3 位作者 HE Bijiao SHANG Shengfei LIU Peng LIANG Wei 《航空动力学报》 EI CAS CSCD 北大核心 2019年第7期1568-1576,共9页
Reducing the influence of back-sputtering effect can effectively improve the accuracy of the measurement of the Hall thruster plume effect.Quartz crystal microbalance(QCM)was used to measure the deposition and sputter... Reducing the influence of back-sputtering effect can effectively improve the accuracy of the measurement of the Hall thruster plume effect.Quartz crystal microbalance(QCM)was used to measure the deposition and sputtering distribution of HET-40 thruster plume on two different experimental conditions:case1,using liquid nitrogen heat sinks and case 2,without using liquid nitrogen heat sinks.Meanwhile,X-ray photoelectron spectroscopy(XPS)was used to analyze the composition of the QCM surface after two experiments.The results of the two experiments showed that the sputtering rate under the condition of case 1 was slightly higher than case 2.Especially within the range of 90°to 110°relative to the thruster axis,case 1 experiment result showed sputtering effect,while case 2 experiment showed deposition effect.Through analysis of the experimental results,it can be found that using liquid nitrogen heat sink to reduce the temperature of the inner wall surface of vacuum chamber can effectively adsorb the particles sputtered by the plume and reduce the concentration of back-sputtering particles,leading to the above phenomenon. 展开更多
关键词 vacuum exhaust PLUME SPUTTERING EFFECT deposition EFFECT HALL THRUSTER HET-40
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