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cold extrusion deformation behavior of medium carbon steel after quenching and tempering

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中国有色金属学会会刊：英文版 2009年第S3期19卷 552-557页

作者：胡成亮赵震尹冠人袁兆峰徐祥龙 Department of Plasticity Technology Shanghai Jiao Tong University Jiangsu Sunway Precision Forging Co. Ltd.

By taking 40Cr as a specific object, cold extrusion deformation behavior of medium carbon steel after quenching and tempering was studied by experimental works. The influence of deformation extent (10%-50%), cone angle of die (90 °-120 °), hardness after quenching and tempering (HRC21-29) and lubricated condition on the forming load was analyzed. The results show that there is no central bursting and micro crack in the inner of the extruded specimen, and the forming quality is good. The double-peak phenomenon takes place at the front-end of the specimen; the double-peak index increases with deformation extent, and larger deformation can avoid the double-peak phenomenon. The deformation extent is the most important influencing factor, and the lubricated condition almost has no influence, which means that the phosphate coating plus soap process is still a proper lubrication method for cold extrusion of medium carbon steel after quenching and tempering. By investigating the microscopic structure before and after deformation, the initial equiaxed grain is elongated in the extrusion direction, and this feature is more significant at the front-end of specimen.

关键词： medium carbon steel quenching and tempering cold extrusion deformation behavior microstructure

cold metal transfer(CMT) technology-An overview

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Defence Technology（防务技术） 2018年第1期14卷 28-44页

作者： S.Selvi A.Vishvaksenan E.Rajasekar Mechanical Engineering Institute of Road and Transport Technology Automobile Engineering Institute of Road and Transport Technology

cold Metal Transfer technology has revolutionized the welding of dissimilar metals and thicker materials by producing improved weld bead aesthetics with controlled metal deposition and low heat-input. In this study, the process, weld combinations, laser-CMT hybrid welding and applications of CMT welding are critically reviewed. Microstructure and other weld characteristics have been discussed at length for various base metal combinations. Particularly, the welding of aluminium and steel with better results has been possible with CMT Welding. The results reviewed in this article indicate that the CMT-Laser hybrid welding is more preferable to Laser or Laser hybrid welding. CMT welding has found applications in automobile industries, defence sectors and power plants as a method of additive manufacturing.

关键词： cold metal transfer [CMT]Welding Laser-CMT welding Additive manufacturing Composite joint Metal inert gas[MIG] Metal active gas[MAG]

cold acclimation improves photosynthesis by regulating the ascorbate–glutathione cycle in chloroplasts of Kandelia obovata

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Journal of Forestry Research 2019年第3期30卷 755-765页

作者： Weicheng Liu Chunfang Zheng Jinong Chen Jianbiao Qiu Zhixing Huang Qi Wang Yong Ye Zhejiang Key Laboratory of Exploitation and Preservation of Coastal Bio-resource Zhejiang Mariculture Research Institute325005 WenzhouPeople’s Republic of China College of Life and Environmental Science Wenzhou University325035 WenzhouPeople’s Republic of China Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem College of the Environment and EcologyXiamen University361005 XiamenPeople’s Republic of China

As the most northerly mangrove species in China, Kandelia obovata may undergo extreme cold event stress. Enhancing the cold tolerance of this species is crucial to its successful afforestation. This study aimed to determine the resistance of K. obovata seedlings to low temperature stress by cold acclimation and to explain the mechanisms for alleviating cold injury. To understand these mechanisms, seedlings that were acclimatized and not acclimatized were exposed to 5℃/- 2℃(day/night)for 48 *** showed that low temperature stress reduced leaf photosynthesis of non-acclimatized seedlings by inducing oxidative stress and structural damage to chloroplasts. These phenomena were shown by increasing levels of malondialdehyde (MDA), O2-and H2O2, as well as decreasing enzyme activities in the ascorbate–glutathione (AsA-GSH) cycle. However, cold-acclimatized seedlings had improved photosynthetic rates and efficiency of photosystem II (PSII) under low temperature stress. Compared with non-acclimatized seedlings, leaves of coldacclimatized seedlings under low temperature stress for 48 h exhibited higher anti-oxidative enzyme activities, lower levels of O2^- and H2O2, less damage to chloroplast structure, and removed 33.7% of MDA at low temperature stress for 48 h. The data indicate that cold acclimation enhances photosynthetic capacity by effectively regulating activation in the PSII electron transport and the AsA–GSH cycle to scavenge excess ROS in chloroplasts, while the latter is more important.

关键词： Ascorbate–glutathione cycle cold acclimation Kandelia obovata Photosynthesis

Winter Arctic warming and its linkage with midlatitude atmospheric circulation and associated cold extremes: The key role of meridional potential vorticity gradient

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Science China Earth Sciences 2019年第9期62卷 1329-1339页

作者： Muyuan LI Dehai LUO CAS Key Laboratory of Regional Climate-Environment for Temperate East Asia Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China University of Chinese Academy of Sciences Beijing 100049 China

The surface air temperature over the Eurasian continent has exhibited a significant cooling trend in recent decades(1990–2013), which has occurred simultaneously with Arctic warming and Arctic sea ice loss. While many studies demonstrated that midlatitude cold extremes are linked to Arctic warming and Arctic sea ice loss, some studies suggest that they are *** causal relationship between midlatitude cold extremes and Arctic change is uncertain, and it is thus an unsolved and difficult issue. It has been widely recognized that the severity and location of midlatitude cold extremes are closely related to the persistence, location and movement of blocking systems. It might be possible that the Arctic sea ice decline or the Arctic’s warming influences midlatitude cold extremes by changing the blocking system. This paper reviews the recent research advances on the linkages between the blocking system and Arctic warming. The nonlinear multiscale interaction model of Luo et *** that the magnitude of the meridional gradient(PVy) of the background potential vorticity(PV) is a key parameter that reflects changes in the dispersion and nonlinearity of the blocking system. It was found that Arctic warming played a role in reducing the dispersion of the blocking system and enhancing its nonlinearity by reducing the magnitude of PVy. A small PVyis a favorable background condition for increasing the duration of blocking events and producing midlatitude cold ***, because the magnitude of PVyreflects the difference between the background PVof the Arctic high latitudes and the midlatitude continent, the occurrence of midlatitude cold extremes not only depends on an anomalous background PVover Arctic high latitudes but also on its value over the midlatitudes. Thus, Arctic warming or sea ice decline is not necessary for the occurrence of midlatitude cold extremes.

关键词： Sea ice decline Arctic warming PV gradient Blocking cold extremes

The impact of cold atmospheric pressure plasma jet on seed germination and seedlings growth of fenugreek(Trigonella foenum-graecum)

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Plasma Science and Technology 2019年第10期21卷 61-72页

作者： Sahar A FADHLALMAWLA Abdel-Aleam H MOHAMED Jamal Q M ALMARASHI Tahar BOUTRAA Physics Department College of ScienceTaibah UniversityAl-Madinah Al-Munawarah 42353Saudi Arabia Physics Department Faculty of ScienceBeni-Suef UniversityBeni-Suef 52511Egypt Department of Biology College of SciencesUniversity of TaibahAl-Madinah Al-Munawarah 42353 Saudi Arabia

The effects of cold atmospheric-pressure plasma jet (CAPPJ) were investigated on germination and early seedling growth of fenugreek (Trigonella foenum-graecum L) seeds. A two-electrode argon CAPPJ system with and without an additional grounded electrode [accelerating grounded (AG) electrode] was used at different exposure times. After 16 h of observation, the germination rates increased by 4 and 7 times, without and with using an AG electrode, respectively, for 1 min of plasma exposure. An increase in shoot fresh weight was observed, especially at 10 min exposure time. A high dry weight of root and shoot at 1 min-AG exposure time was observed. The root:shoot ratio was lower in plasma-treated seedlings, compared with the control plants. The study found that the O-radical emission line (777.4 nm) enhanced 5 times, due to the presence of an AG electrode, which increased the axial electric field and led to the formation of more streamers. The three stated effects (O-radicals, enhancement of the electric field and streamers) could be the cause for the stimulation of seed germination and seedling growth parameters when using the CAPPJ. The scanning electron microscope images showed the etching of the seed surface layers, which was more pronounced when an AG electrode was applied. The results of the current study indicate that the germination rates increased due to the increase of O-radical concentration and the etching of the seed surfaces.

关键词： cold plasma fenugreek (Trigonella foenum-graecum) germination growth

Influences of the inner diameter of the solid shielding tube on the characteristics of the radio-frequency cold atmospheric plasma jet

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Plasma Science and Technology 2019年第9期21卷 82-90页

作者： Jing LI Heping LI Department of Engineering Physics Tsinghua University

Active control of the local environment of the cold atmospheric plasma(CAP) jet is of great importance in actual applications since the CAP operates in an open atmosphere with the inevitable entrainment of the surrounding cold air. In this paper, the solid shielding effects of the cylindrical quartz tubes with different inner diameters on the characteristics of the CAP jets driven by a radio-frequency(RF) power supply are studied experimentally. The experimental results show that the total length of the shielded plasma jet can be increased significantly by an appropriate combination of the quartz tube inner diameter and that of the plasma generator nozzle exit with other parameters being unchanged. This phenomenon may be qualitatively attributed to the loss of diffusion of the charged particles in the radial direction under different inner diameters of the quartz tubes. Compared with the plasma free jet, the plasma shielding jet is produced with optimized parameters including longer plasma jet length, higher concentrations of chemically reactive species, higher rotational, vibrational, and electron excitation temperatures when the inner diameters of the solid shielding tube and the generator nozzle exit are the same. A maximum plasma jet length of 52.0 cm is obtained in contrast to that of 5.0 cm of the plasma free jet in this study. The experimental results indicate that the solid shielding effect provides a new method for the active control of the local environment of the RF-CAP jet operating in an open atmosphere.

关键词： cold atmospheric plasma jet radio-frequency glow discharge solid shielding effect effect of the tube inner diameter active control of plasma jet characteristics

Collision of cold CaF molecules: Towards evaporative cooling

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Chinese Physics B 2019年第3期28卷 161-167页

作者： Yuefeng Gu Yunxia Huang Chuanliang Li Xiaohua Yang School of Science Nantong UniversityNantong 226019China Department of Physics School of Applied ScienceTaiyuan University of Science and TechnologyTaiyuan 030024China State Key Laboratory of Precision Spectroscopy East China Normal UniversityShanghai 200062China

Long range intermolecular interaction potential surface of CaF(~2∑^+) was simulated by employing the MOLPRO program and using the RCCSD(T)/def2-TZVP theory. The predicted data were further fitted to obtain the collision crosssection. The elastic collision cross-section of CaF at the temperature around 2 mK is as high as 6.5 × 10^(-9) cm^2 and the collision rate is over 4.1 × 10~6 Hz. Additionally, we found that an orientation electric field will simplify the intermolecular interaction potential function from quaternary into ternary and the collision cross-section will be raised by about three orders. All-optical evaporative cooling of cold CaF is discussed in the conclusion.

关键词： intermolecular interaction potential energy surface cold collision evaporative cooling

Influence of cold plasma treatment on insecticidal properties of wheat seeds against red flour beetles

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Plasma Science and Technology 2019年第8期21卷 97-102页

作者： S AFSHEEN U FATIMA T IQBAL M ABRAR S MUHAMMAD A SAEED M ISA M F MALIK S SHAMAS Department of Zoology Faculty of ScienceUniversity of GujratHafiz Hayat CampusGujrat50700Pakistan Department of Physics Faculty of ScienceUniversity of GujratHafiz Hayat CampusGujrat50700Pakistan3Department of PhysicsHazara University MansehraMansehra21300Pakistan4Department of PhysicsGovernment College Women UniversitySialkot51310Pakistan

For the long-term fortification of warehoused crops, the insecticidal impact of cold plasma treated wheat seeds against red flour beetles are *** this study, the gain weight loss,mortality and repellency tests of cold plasma treated seeds are investigated and statistical analysis is carried out by SPSS *** plasma treatment is carried out at 800 V for 1 and 4 *** results show that the minimum grain weight loss is observed in plasma treated seeds as compared to controlled *** is also observed that the mortality rate is minimum in the controlled seed while maximum at 4 min plasma ***, the repellent effect has a very small variation as compared to the controlled seed for Tribolium ***, plasma treatment can be considered as a practical and effective method for seed protection against red floor beetles particularly during long-term storage by controlling the insecticidal effects.

关键词： cold plasma mortality repellency grain weight loss quality stored seeds protection

Influence of low-vacuum helium cold plasma pre-treatment on the rooting and root growth of zoysiagrass(Zoysia Willd.) stolon cuttings

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Plasma Science and Technology 2019年第5期21卷 162-167页

作者： Ling LI Hailin GUO Junqin ZONG Jingbo CHEN Yi WANG Jianjian LI Dandan LI Hanliang SHAO Jianxiu LIU Jiangsu Key Laboratory for the Research and Utilization of Plant Resources Institute of BotanyJiangsu Province and Chinese Academy of SciencesNanjing 210014People's Republic of China Cha ngzhou Zhongke Changtsi Plasma Processing Apparatus Plasma Tech no logy Corporation Changzhou 213022People's Republic of China

The influence of low-vacuum helium cold plasma treatment on the rooting percentage,root growth and physiochemical properties of zoysiagrass stolon cuttings was *** stolon cuttings were pre-treated with 0,100,200,300 and 400 W of cold plasma for 15 *** cold plasma positively stimulated rooting and improved the root growth of the zoysiagrass stolon cuttings,and the 300 W treatment produced the best *** rooting percentage and root growth parameters,including the root length,total root surface area,total root volume,average root diameter,and root dry weight,significantly improved in response to the cold plasma *** addition,the water uptake and relative conductivity of the stolon cuttings increased significantly in response to the cold plasma *** results revealed that cold plasma-stimulated rooting and root growth appear to be a consequence of the improvement in permeability and water absorbing capacity of zoysiagrass stolon *** results of the present study will provide inspiration and support for the application of cold plasma in the vegetative propagation of plants.

关键词： cold plasma zoysiagrass stolon cutting rooting root growth