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Mechanical property and thermal shock behavior of tungsten-yttria-stabilized zirconia cermet fabricated by spark plasma sintering

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Tungsten 2024年第1期6卷 134-140页

作者： Lin-Chao Zhang Ke Jing Rui Liu Zhuo-Ming Xie jun-feng yang Gang Li Xian-Ping Wang Xue-Bang Wu Qian-feng Fang Chang-Song Liu Key Laboratory of Materials Physics Institute of Solid State PhysicsHFIPSChinese Academy of SciencesHefei 230031China University of Science and Technology of China Hefei 230026China Science and Technology on Reactor Fuel and Materials Laboratory Nuclear Power Institute of ChinaChengdu 610041China

The cermet fuels have been considered as a potential key component for the nuclear thermal propulsion,and the homogeneity of the fuel particles in the metal matrix plays a crucial role in stabilizing the structure at extremely high *** this work,liquid paraffin was used as additive to improve the distribution of yttria-stabilized zirconia(YSZ,an appropriate surrogate for UO_(2) fuel)microspheres in the tungsten(W)matrix,and the W-YSZ cermet wafers(volume ratio 1:1)with a relative density of 97.6%were fabricated by spark plasma sintering with a specifically designed *** effects of the paraffin dosage(0-5 wt.%)on the homogeneity,microstructure,mechanical properties,and the thermal conductivity of W-YSZ cermet were *** W-YSZ sample with 2 wt.%paraffin shows the highest homogeneity and exhibits the best comprehensive properties,including the ultimate tensile strength of 132.2 MPa at 600℃,the bending strength of455 MPa and thermal conductivity of 50 W·m^(-1)·K^(-1)at room ***,the cermet could keep structurally sound after thermal shocked at a heat load of 20 MW·m^(-2).These results would be helpful for the design and optimization of the cermet fuels in the nuclear thermal propulsion.

关键词： Nuclear thermal propulsion Tungsten Cermet Liquid paraffin Thermal shock

Local Linear Convergence of an ADMM-Type Splitting Framework for Equality Constrained Optimization

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Journal of the Operations Research Society of China 2021年第2期9卷 307-319页

作者： jun-feng yang Yin Zhang Department of Mathematics Nanjing UniversityNanjing 210023China Institute for Data and Decision Analytics The Chinese University of Hong KongShenzhen 518172China

We establish local convergence results for a generic algorithmic framework for solving a wide class of equality constrained optimization *** framework is based on applying a splitting scheme to the augmented Lagrangian function that includes as a special case the well-known alternating direction method of multipliers(ADMM).Our local convergence analysis is free of the usual restrictions on ADMM-like methods,such as convexity,block separability or linearity of *** offers a much-needed theoretical justification to the widespread practice of applying ADMM-like methods to nonconvex optimization problems.

关键词： Alternating direction method of multipliers Nonlinear splitting Stationary iterations Spectral radius Local linear convergence

Effect of chromium content on microstructure and corrosion behavior of W-Cr-C coatings prepared on tungsten substrate

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Frontiers of Materials Science 2015年第1期9卷 77-84页

作者： Yan JIANG jun-feng yang Qian-feng FANG Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Sciences Hefei 230031 China

W-Cr-C coatings with different chromium contents （0-3wt.%） were fabricated on the tungsten substrates by spark plasma sintering （SPS） method from the graphite and chromium mixed powders. SEM and XRD were exploited to analyze the effect of Cr contents on the microstructure of coatings. It was found that the abnormal hollow WC grains disappeared with addition of Cr less than 2%, and the microstructures were largely refined and densified. With further increase of Cr addition, the grains changed slightly but the densificaUon was reduced. The most dense coating was achieved at I wt.% Cr. Corrosion behavior of the W-Cr-C coatings were investigated by impedance spectrum and potentiodynamic polarization tests. Results suggested that the W-1Cr-C coated W sample exhibited the lowest corrosion current density and highest corrosion potential due to the most densified microstructure, indicating that the addition of Cr at 1 wt.% was optimal for WC coating against corrosion.

关键词： W-Cr-C coating spark plasma sintering (SPS) corrosion resistance electrochemical measurement

Tribological properties of transition metal di-chalcogenide based lubricant coatings

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Frontiers of Materials Science 2012年第2期6卷 116-127页

作者： jun-feng yang Braham PARAKASH Jens HARDELL Qian-feng FANG Department of Applied Physics and Mechanical Engineering Lulea University of TechnologySE-97187 LuleaSweden Key Laboratory of Materials Physics Institute of Solid State PhysicsChinese Academy of SciencesHefei 230031China

Transition metal di-chalcogenides MX2 （X= S, Se, Te; and M = W, Mo, Nb, Ta） are one kind of solid lubricant materials that have been widely used in industry. The lubricant properties of such lubricant coatings are dependent not only on microstructure, orientation, morphology, and composition of the coatings, but also on the substrate, the interface between substrate and lubricant coatings, and the specific application environment. In this review, the effects of parameters on tribological properties of such kind of lubricant coatings were summarized. By comparing advantages and disadvantages of those coatings, the special treatments such as doping, structural modulation and post-treatment were suggested, aiming to improve the tribologicai performance under severe test conditions （e.g. high temperature, oxidizing atmosphere or humid condition）.

关键词： transition metal di-chalcogenide solid lubricant coating tribologicalproperty

Influence of service temperature on tribological characteristics of self-lubricant coatings： A review

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Frontiers of Materials Science 2013年第1期7卷 28-39页

作者： jun-feng yang Yan JIANG Jens HARDELL Braham PRAKASH Qian-feng FANG Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Sciences Hefei 230031 China Department of Applied Physics and Mechanical Engineering Lulea University of Technology SE-971 87 Lulea Sweden

Self-lubricating coatings have been widely used to reduce friction in moving machine assemblies. However, the tribological performance of these coatings is strongly dependent on the service temperature. In this paper, an extensive review pertaining to the influence of operating service temperature on tribological performance of self-lubricating coatings has been carried out. Based on the effective lubricating temperature range, the self-lubricating coatings developed in the past have been divided into three groups: low temperature lubricant coating (from −200°C to room temperature), moderate temperature lubricant coating (from room temperature to 500°C) and high temperature lubricant coating (> 500°C). Ideas concerning possible ways to extend the operating temperature range of self-lubricating coatings have been presented as follows: hybridized tribological coating, adaptive tribological coatings, and diffusion rate limited solid lubricant coating. In addition, a new self-lubricating coating formulation for potential application at a wide operating temperature range has been proposed.

关键词： temperature solid lubricant self-lubricating coating tribological property

Comparison of membrane fouling during short-term filtration of aerobic granular sludge and activated sludge

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Journal of Environmental Sciences 2007年第11期19卷 1281-1286页

作者： ZHOU jun yang feng-lin MENG Fan-gang AN Peng WANG Di School of Environmental and Biological Science and Technology Dalian University of Technology Dalian 116024 China

Aerobic granular sludge was cultivated adopting internal-circulate sequencing batch airlift reactor. The contradistinctive experiment about short-term membrane fouling between aerobic granular sludge system and activated sludge system were investigated. The membrane foulants was also characterized by Fourier transform infrared （FTIR） spectroscopy technique. The results showed that the aerobic granular sludge had excellent denitrification ability; the removal efficiency of TN could reach 90%. The aerobic granular sludge could alleviate membrane fouling effectively. The steady membrane flux of aerobic granular sludge was twice as much as that of activated sludge system. In addition, it was found that the aerobic granular sludge could result in severe membrane pore-blocking, however, the activated sludge could cause severe cake fouling. The major components of the foulants were identified as comprising of proteins and polysaccharide materials.

关键词： membrane bioreactor membrane fouling pore-blocking cake layer resistance aerobic granular sludge

Nogo-A expression dynamically varies after spinal cord injury

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Neural Regeneration Research 2015年第2期10卷 225-229页

作者： Jian-wei Wang jun-feng yang Yong Ma Zhen Hua yang Guo Xiao-lin Gu Ya-feng Zhang Wuxi Hospital of Traditional Chinese Medicine Institute of Orthopedics and Traumatology of Nanjing University of Chinese Medicine Nanjing University of Chinese Medicine

The mechanism involved in neural regeneration after spinal cord injury is unclear. The my-elin-derived protein Nogo-A, which is speciifc to the central nervous system, has been identiifed to negatively affect the cytoskeleton and growth program of axotomized neurons. Studies have shown that Nogo-A exerts immediate and chronic inhibitory effects on neurite *** vivo, inhibitors of Nogo-A have been shown to lead to a marked enhancement of regenerative axon extension. We established a spinal cord injury model in rats using a free-falling weight drop device to subsequently investigate Nogo-A expression. Nogo-A mRNA and protein expression and immunoreactivity were detected in spinal cord tissue using real-time quantitative PCR, immu-nohistochemistry and western blot analysis. At 24 hours after spinal cord injury, Nogo-A protein and mRNA expression was low in the injured group compared with control and sham-operated groups. The levels then continued to drop further and were at their lowest at 3 days, rapidly rose to a peak after 7 days, and then gradually declined again after 14 days. These changes were observed at both the mRNA and protein level. The transient decrease observed early after injury followed by high levels for a few days indicates Nogo-A expression is time dependent. This may contribute to the lack of regeneration in the central nervous system after spinal cord injury. The dynamic varia-tion of Nogo-A should be taken into account in the treatment of spinal cord injury.

关键词： nerve regeneration spinal cord injury contusion Nogo-A axon growth immunohisto-chemistry fluorescent quantitative PCR neural regeneration

Recent Advances in Deciphering the Mechanisms and Biological Functions of DNA Demethylation

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Chinese Journal of Chemistry 2024年第6期42卷 645-651页

作者： yang feng Sheng-jun Chen Bi-feng Yuan Key Laboratory of Aquatic Product Processing Ministry of Agriculture and Rural AffairsNational R&D Center for Aquatic Product ProcessingSouth China Sea Fisheries Research InstituteChinese Academy of Fishery SciencesGuangzhouGuangdong510300 China School of Public Health Research Center of Public HealthRenmin Hospital of Wuhan UniversityWuhan UniversityWuhanHubei430071 China

5-Methylcytosine (5mC) is a dynamic and reversible epigenetic modification in genomic DNA of higher *** has been well-established that the demethylation of 5mC occurs through the ten-eleven translocation (TET)-mediated oxidation of 5mC followed by thymine DNA glycosylase (TDG)-initiated base excision repair (BER).Recent findings also have identified an alternative pathway of DNA *** this pathway,TET enzymes directly oxidize 5mC to form 5-formylcytosine (5fC) or 5-carboxylcytosine (5caC).These modified bases can undergo direct deformylation or decarboxylation,***,DNA demethylation can also occur through the deamination of 5mC and 5hmC,resulting in the production of thymine and 5-hydroxymethyluracil (5hmU),*** DNA demethylation pathways possess critical functional implications and roles in biological *** Recent Advances article will focus on the studies of mechanisms and biological functions of DNA demethylation,shedding light on the reversible nature of the epigenetic modification of 5mC.

关键词： Epigenetics DNA DNA methylation 5-Methylcytosine Demethylation Mechanisms Biological functions C—C bond cleavage Mass spectrometry

Off-pump coronary artery bypass grafting using a bilateral internal mammary artery Y graft

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Journal of Geriatric Cardiology 2012年第3期9卷 247-251页

作者： Cheng-Xiong Gu jun-feng yang Hong-Chao Zhang Hua Wei Ling-Ke Li Department of Cardiac Surgery Capital Medical University Beijing Anzhen Hospital Beijing 100029 China Department of Cardiacvascular Surgery Airfore General Hospital Beijing 100142 China

Objective To evaluate the outcome of off-pump coronary artery bypass grafting （OPCABG） using a bilateral internal mammary artery （BIMA） Y configuration graft to achieve total arterial myocardial revascularization. Methods From October 2002 to December 2008, 208 patients （196 males and 12 females） underwent OPCABG using a BIMA Y configuration graft. The average age of the patients was 56.5 ± 11.3 years, with an age range of 33-78 years. A total of 167 （80.2%） cases had triple-vessel disease. Left main stem disease was found in 33 （15.9%） cases, and double-vessel disease was found in 8 （3.9%） cases. The semi-skeletonization technique was used to harvest the two internal mammary arteries （IMAs）, and then the free right internal mammary artery was connected end-to-side to the left internal mammary artery （LIMA） in situ to complete the Y configuration graft. Off-pump and sequential anastomosis methods were used to perform coronary artery bypass surgery in all patients. Graft patency was assessed intm-operatively with the HT311 transit time flowmeter. Results A total of 728 distal anastomoses were performed in 208 patients, with the average being 3.5± 1.3 per person. No one died or experienced recurrent angina within 30 days after the operation. Conclusions OPCABG using the BIMA Y graft was safe and effective to achieve total arterial revascularization. This method avoids surgical operation on the ascending aorta and other incisions.

关键词： Bilateral internal mammary arteries Coronary artery bypass grafting Internal mammary artery Off-pump