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Design and Verification of an Auxiliary System for high vacuum Die Casting

Chinese Journal of Mechanical Engineering 2010年第5期23卷 547-552页

作者： GE Xiaohong HUANG Hongwu LI Hui LIU Yadan School of Physics and Mechanical ＆ Electrical Engineering Xiamen University Xiamen 361005 China Institute of Material Processing and Die ＆ Mould Integrated Technology Xiamen University of Technology Xiamen 361024 China

vacuum die casting is the optimal method to produce high quality aluminum alloy *** present,there are still very few systematic studies on vacuum die casting theory and equipment *** the basis of the existing theories of the vacuum die casting pumping and venting systems,a simplified model is established in this *** model has an aggregate unit consisted of ＂vacuum pump ＋ buffer tank＂ and a cylindrical container（including the shot sleeve,cavity and exhaust channel）.The theoretical analysis is carried out between the cavity pressure and the pumping time under different volume *** auxiliary system for high vacuum die casting is designed based on the above *** system is composed of a vacuum control machine and a new vacuum stop *** machine has a human-computer control mode with ＂programmable logic controller（PLC）＋ touch screen＂ and a real-time monitoring function of vacuum degree for buffer tank and die *** vacuum stop valve with the ＂compressed gas ＋ piston rod ＋ labyrinth groove＂ structure can realize the function of whole-process vacuum *** new system shows great advantages on vacuuming the cavity with a much faster speed by making tests on an existing die casting mold and a 250 t die casting machine.A die cavity pressure less than 10 kPa can be reached within 0.8 s in the experiment and the porosity of castings can be greatly *** systematic studies on vacuum die casting theory and equipment have a great guiding significance for high vacuum die casting,and can also be applied to other high vacuum forming in related theoretical and practical research.

关键词： vacuum die casting pumping model high vacuum vacuum stop valve auxiliary system

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Best Magnetic Condition to Generate Hollow Cathode Glow Plasma in high vacuum

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Plasma Science and Technology 2014年第1期16卷 21-25页

作者：赵小令陈仕修陈堃陈柏恺 School of Electronic Information and Electrical Engineering Shanghai Jiao Tong University School of Electrical Engineering Wuhan University

Based on magnetron hollow cathode discharge, the magnetic condition of glow plasma generation in high vacuum, including both direction and magnitude of the applied mag- netic field, is theoretically derived and experimentally evaluated in this paper. Single particle orbital theory is introduced to discuss the possibilities to generate glow plasma at gas pressure under 10-2 Pa when the magnetic field direction is parallel or perpendicular or oblique to the electric field direction. A quantitative estimation criterion of magnetic induction intensity is also proposed in theory. The comparison with experiments suggests that glow plasma in high vacuum will form more easily in oblique magnetic field condition and that the criterion is accurate enough to estimate magnetic induction intensity at a certain gas pressure.

关键词： high vacuum magnetic condition glow plasma hollow cathode discharge

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Radio-frequency design and commissioning of a flexible waveguide for high-vacuum S-band applications

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Radiation Detection Technology and Methods 2020年第2期4卷 250-254页

作者： Xiang He Jian-She Cao Bing-Lin Deng Jing-Dong Liu Nan Gan Key Laboratory of Particle Acceleration Physics and Technology Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China

Purpose Flexible waveguides,which allow for greater deformation as compared to traditional hard waveguides,are highly useful for simplifying waveguide system ***,the peak powers of these waveguides have been limited to several megawatts in non-vacuum ***,a novel flexible waveguide was developed for the S-band(2856 MHz)with the aim of facilitating the interconnection of two hard *** The flexible waveguide was composed of brass,and its surface was plated with oxygen-free high-conductivity copper for brazing with stainless steel flanges in a vacuum *** connecting the stainless steel flanges together,it can be applied to a high-vacuum *** The prototype exhibited good measurement results in low-power microwave tests;the results of a 72-h vacuum leak test showed satisfactory vacuum performance as well,and no obvious surface collapse was ***-power microwave commissioning was conducted between June and July 2019;the waveguide showed a maximum average power of approximately 2.7 *** Unfortunately,the prototype was damaged after reaching that power level,which indicates the need for further optimization of the fabrication *** our experiment,it is clear that the flexible waveguide cannot be used in large accelerators because of its average power limit.

关键词： S-band Flexible waveguide high vacuum Microwave commissioning

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A practical and effective method for reducing differential reflectance spectroscopy noise

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Nanotechnology and Precision Engineering 2022年第1期5卷 49-53页

作者： Hui Qi Xing Fu State Key Laboratory of Precision Measurement Technology and Instruments Tianjin UniversityTianjin 300072China Tianjin Research Center of MicroNano Manufacturing Technology Tianjin UniversityTianjin 300072China

Differential reflectance spectroscopy(DRS)is a powerful tool to study processes during thin-film growth,especially that of transition metal dichalcogenides and organic thin *** satisfy the requirements for in situ and real-time monitoring of film growth,including spectral resolution and sensitivity at the level of monolayers and even sub-monolayers,the most challenging technical task in DRS is to reduce noise to an extremely low level so that the best possible signal-to-noise ratio can be *** this paper,we present a simplified and cost-effective DRS apparatus,with which we show that the measurement noise is mainly composed of thermal drift noise and explore the temperature-dependence of the DRS *** on the results obtained,we propose an easily realized and effective scheme aiming to reduce the *** results demonstrate that this scheme is effective in stabilizing reliable signals for a long period of several *** noise reduction is achieved,with the typical average noise of the DRS system being decreased to 0.05%over several *** improved DRS system is applied to study the growth of an organic semiconductor layer for an organic field-effect transistor *** results indicate that the apparatus proposed in this paper has potential applications in fabrication of devices on the nanoscale and even the sub-nanoscale.

关键词： Differential reflectance spectroscopy Thin-film measurement technique In situ spectroscopy high vacuum Noise reduction OFET

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The Wear Process of PTFE Coatings Under vacuum Conditions

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Journal of Harbin Institute of Technology(New Series) 2014年第1期21卷 121-124页

作者： Xing-Dong Yuan Yong Liu De-Zhuang Yang Shi-Yu He School of Materials Science and Engineering Shandong Jianzhu University Space Material and Environment Engineering Lab. Harbin Institute of Technology

The wear process of PTFE coatings sliding against GCr15-bearing steel ball under vacuum conditions was investigated,and the hardness of the PTFE coatings on both sides of wear track was measured. The experimental results showed that the friction coefficient of the PTFE coatings increases with the increase of sliding distance under different sliding velocities. And the friction coefficient of the PTFE coatings increases with the increase of sliding distance under different sliding loads. The wear rate of PTFE coatings decreases with the increase of sliding distance. And the majority of the wear produced during the whole wear process of PTFE coatings sliding against GCr-15 steel ball comes from the early period of friction. The hardness of PTFE coatings on both sides of wear track increases as the distance increases and distributes symmetrically around the wear track. Scanning electron microscope( SEM) was utilized to investigate the worn surface of PTFE coating. It was found that the worn surface of PTFE coating is characterized by sever plastic deformation and spalling of the PTFE coating. The edge of wear track is characterized by micro cracking.

关键词： sliding wear two-body abrasion polymers high vacuum

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Tribological Behavior of Polytetrafluoroethylene Coatings Based on LY12 Substrates in the Space Environment

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Journal of Shanghai Jiaotong university(Science) 2014年第5期19卷 636-640页

作者：袁兴栋刘勇杨德庄何世禹 School of Materials Science and Engineering Shandong Jianzhu University Space Material and Environment Engineering Laboratory Harbin Institute of Technology

The spacecraft space radiation environment was simulated by60 Co source. The polytetrafluoroethylene(PTFE) coatings were fabricated on LY12 substrates. And the effect of gamma(γ) irradiation on the tribological behavior of PTFE coatings under vacuum conditions was investigated. Results indicate that the radiation dose has insignificant effect on the friction coefficient of PTFE coatings, and the wear of PTFE coatings reduces with the increase of gamma dose. As the gamma dose was 100 kGy, the friction coefficient of the PTFE coatings first increased with the increase of sliding velocity and then decreased, and the wear of the PTFE coatings decreased with the increase of sliding speed. As the gamma dose was 100 kGy, the friction coefficient of the PTFE coatings first decreased with the increase of load and then increased, and the wear rate of PTFE coatings increased with the increase of load. Scanning electron microscope was utilized.

关键词： sliding wear two-body abrasion polymers high vacuum

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Effects of Environments on the Noise of Atomic Force Microscopy Cantilevers

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Journal of Harbin Institute of Technology(New Series) 2020年第4期27卷 1-7页

作者： Hongyu Ju Song Zhang Shuxun Cui School of Life Science and Engineering Key Lab of Advanced Technologies of MaterialsMinistry of EducationSouthwest Jiaotong UniversityChengdu 610031China

Thermal vibration of the cantilevers is the main source of noise in atomic force microscopy(AFM).When immersed in liquids,the dynamic behavior of the cantilevers will be significantly affected by the *** this study,the effects of environments on the noise of AFM were *** results show that the V⁃shaped cantilever exhibited very low noise in high *** noise in atmospheric environment was also *** liquid environments,the noise dramatically *** systematic noise was low and dependent on the distance between the tip and *** the velocity increased,the noise of V⁃shaped cantilever was increased in a similar *** is also found that the variation trend was more pronounced as the liquid viscosity *** noise of rectangular cantilever was lower than that of V⁃shaped cantilever in the same *** present study indicates that high vacuum is an ideal environment for single molecule force spectroscopy(SMFS)due to the lower noise and higher *** a better signal⁃to⁃noise ratio,both the cantilever velocity and liquid viscosity should be as low as *** results will be helpful when a lower noise is desired in weak force detection.

关键词： atomic force microscopy cantilever noise high vacuum viscosity

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IMPACT OF CHARGE ACCUMULATION ON SURFACE ELECTRIC FILED INTENSITY IN vacuum UNDER NANOSECOND IMPULSE VOLTAGE APPLICATION 19th

IMPACT OF CHARGE ACCUMULATION ON SURFACE ELECTRIC FILED INTE...

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The ⅪⅩ International Conference on Gas Discharges and Their Applications

作者： BO QI CHENGRONG LI JIXIN GAO DANGGUO XU SHAOYU LIU Beijing Key Laboratory of high Voltage and EMC North China Electric Power University State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University North China Electric Power Research Institute

ISBN: (纸本)9771003651221

＜正＞The present research attempts to fill the gap by studying the impact of surface charge accumulation on the electric field distribution in vacuum under the application of nanosecond impulse *** experimental platform for the testing of dielectric surface charge under nanosecond impulse voltage application in vacuum was established and the static probe method was adopted to have measured the distribution of accumulated surface charges and thus the impact of charge accumulation on the surface electric field intensity under the impulse voltage *** results indicate that surface charge accumulation leads to apparent increase in local electric field intensify on the insulator surface,endangering the dielectric properties of both vacuum and insulator surface. The present paper therefore argues not to neglect the impact of surface charge accumulation on electric field distribution when designing dielectric devices in high vacuum but to pay high attention to the selection of appropriate dielectric materials and the use of suitable shapes of electrodes.

关键词： dielectric materials probe method VOLTAGE Pulses Electric charge NANOSECOND Dielectric devices electric field distribution Shock voltage high vacuum field distribution Surface charge Surfaces vacuum Electricity

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The Characteristics of Hollow Cathode Glow Plasma with Magnet in Low Pressure

The Characteristics of Hollow Cathode Glow Plasma with Magne...

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第十六届全国等离子体科学技术会议暨第一届全国等离子体医学研讨会

作者： Xiaoling Zhao Shixiu Chen Kun Chen School of Electrical Engineering Wuhan University School of Electronic Information and Electrical Engineering Shanghai Jiao Tong University

This paper studies hollow cathode glow plasma in magnetic *** to obtain glow plasma under 10 Pa and factors affecting the size of glow plasma are investigated. The pressure of glow discharge experiment is generally 100 Pa,and that of the hollow cathode discharge about 100 *** lower pressure(1010 Pa) is required,external magnetic fields can be attached to the hollow cathode *** the start stage,drifting distance of electrons must be longer than its mean free path to cause collision ionization with glow plasma *** a hollow cathode structure with magnetic fields,electrons oscillate back and forth between two cathodes while doing cyclotron motion,increases the electrons’ actual ***,the problem that in how much of the magnetic field strength the glow plasma in low pressure will appear has not been *** theoretical derivation and experimental study,it is observed hat in 6×10 Pa,using magnet whose surface magnetic field strength is 44mT,hollow cathode glow discharge plasma is obtained. On the other hand,electrode gap and the anode aperture are two factors which have influence on the glow plasma *** the lab,each experiment of one factor changed has been carried *** show that the size of glow discharge plasma is affected by electrode gap,and comparatively the anode aperture affects a *** addition,the glow plasma size has close relation with the loop current of the glow discharge. The paper provides useful accordance to further *** can choose magnet with smaller surface magnetic field strength based on needed pressure condition, which greatly reduces the *** addition,the glow plasma size can be controlled according to the experimental needs.

关键词： high vacuum external magnetic field glow discharge plasma hollow cathode discharge

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