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Current-carrying tribological behavior of C/Cu contact pairs in extreme temperature and humidity environments for railway catenary systems

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Science China(Technological Sciences) 2024年第8期67卷 2537-2548页

作者： SHEN MingXue ji DeHui HU Qiang XIAO Li LI QiuPing State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure East China Jiaotong UniversityNanchang 330013China School of Materials Science and Engineering East China Jiaotong UniversityNanchang 330013China Institute of Applied Physics Jiangxi Academy of SciencesNanchang 330095China

Many current-carrying contact pairs, such as those found in pantograph-catenary systems, operate in open environments and are susceptible to significant external interference from temperature and humidity variations. This study investigated the evolution of the friction coefficient and contact resistance of C/Cu contact pairs under alternating temperature, humidity, and current conditions. Through experimentation, the wear rate and microtopography of the worn surface were analyzed under various constant parameters. Subsequently, the differences in tribological behavior and current-carrying characteristics of the contact pairs under these three parameters were explored. The results revealed that the decrease in temperature resulted in a significant increase in the friction coefficient of the contact pairs, carbon wear, and copper surface roughness. Additionally, the surface oxidation rate was lower at lower temperatures. Moreover, contact resistance did not consistently increase with decreasing temperature, owing to the combined action of the contact area and the oxide film. Compared with temperature, humidity fluctuations at room temperature exerted less influence on the friction coefficient and contact resistance of the contact pairs. Dry environments rendered carbon materials vulnerable to oxidation and cracking, while excessive humidity fostered abrasive wear and arcing. High-current conditions generally degraded the tribological properties of C/Cu contacts. In the absence of current, the friction coefficient was extremely high, and the copper transfer was high. Under excessive current, copper was susceptible to plowing by carbon micro-bumps and abrasive particles, resulting in a decrease in the friction coefficient. The release of lipids from the carbon surface due to temperature elevation weakened the electrical contact performance and increased the occurrence of arc erosion, thereby exacerbating carbon wear.

关键词： temperature/humidity pantograph-catenary system C/Cu wear current-carrying friction sliding electrical contact

Ni/bentonite catalysts prepared by solution combustion method for CO_2 methanation

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Chinese Journal of Chemical Engineering 2018年第11期26卷 2361-2367页

作者： Yuexiu jiang Tongxia Huang Lihui Dong Zuzeng Qin hongbing ji School of Chemistry and Chemical Engineering Guangxi Key Laboratory of Electrochemical Energy MaterialsGuangxi University School of Chemistry Sun Yat-sen University

A 20 wt% Ni/bentonite catalyst was prepared by a solution combustion synthesis (SCS), which exhibited higher activity for the CO_2methanation than that of an impregnation method (IPM), and the catalyst prepared by SCS showed a CO_2 conversion of 85% and a CH4selectivity of 100% at 300 °C, atmospheric pressure, and 3600 ml·(g cat)-1·h-1, and the catalyst exhibited stable within a 110-h reaction. The results showed higher me- tallic Ni dispersion, smaller Ni particle size, larger specific surface area and lower reduction temperature in the Ni/ bentonite prepared by SCS than that of IPM. And the Ni/bentonite prepared by the SCS moderated the interaction between NiO and bentonite.

关键词： CO2 methanation Ni/bentonite catalyst Solution combustion synthesis Impregnation method

Friction Stir Welding of Al Alloy Thin Plate by Rotational Tool without Pin

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Journal of Materials Science & Technology 2011年第7期27卷 647-652页

作者： Liguo Zhang Shude ji Guohong Luan Chunlin Dong Li Fu School of Aerospace Engineering Shenyang Aerospace University Shenyang 110136 China China FSW Center Beijing 100024 China Shenyang Aircraft Design & Research Institute Shenyang 110035 China State Key Laboratory for Manufacturing Systems Engineering Xi an Jiaotong University Xi an 710049 China

For friction stir welding （FSW）, a new idea is put forward in this paper to weld the thin plate of Al alloy by using the rotational tool without pin. The experiments of FSW are carried out by using the tools with inner-concave-flute shoulder, concentric-circles-flute shoulder and three-spiral-flute shoulder, respectively. The experimental results show that the grain size in weld nugget zone attained by the tool with three-spiral-flute shoulder is nearly the same while the grain sizes decrease with the decrease of welding velocity. The displacement of material flow in the heat-mechanical affected zone by the tool with three-spiral-flute shoulder is much larger than that by the tool with inner-concave-flute shoulder or concentric-circles–flute shoulder. The above-mentioned results are verified by numerical simulation. For the tool with three-spiral-flute shoulder, the tensile strength of FSW joint increases with the decrease of welding velocity while the value of tensile strength attained by the welding velocity of 20 mm/min and the rotation speed of 1800 r/min is about 398 MPa, which is 80% more than that of parent mental tensile strength. Those verify that the tool with three-spiral-flute shoulder can be used to join the thin plate of Al alloy.

关键词： Friction stir welding Rotational tool without pin Shoulder shape Plastic flow

Comparative plastomic analysis and insights into the phylogeny of Salvia (Lamiaceae)

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Plant Diversity 2021年第1期43卷 15-26页

作者： hong Wu Peng-Fei Ma hong-Tao Li Guo-Xiong Hu De-Zhu Li Germplasm Bank of Wild Species Kunming Institute of BotanyChinese Academy of SciencesKunmingYunnan650201China University of Chinese Academy of Sciences Beijing100049China College of Life Sciences Guizhou UniversityGuiyangGuizhou550025China

Salvia is the largest genus of Lamiaceae,with almost 1000 species,and has been divided into 11 *** ***,native to East Asia,is particularly important because of its potential medicinal ***,the interspecific relationships of this subgenus have not been resolved and the plastomes of Salvia have rarely been *** the current study,we compared plastid genome structure and organization of 19 species of Salvia(14 newly sequenced and 5 previously published).Our comparative analysis showed that all Salvia plastomes examined have a quadripartite structure typical of most angiosperms and contain an identical set of 114 unique genes(80 protein-coding genes,4 rRNA genes,and 30 tRNA genes).The plastome structure of all Salvia species is highly conserved like other Lamiaceae *** content,gene order,and GC content were highly similar in these *** inverted repeats/single copy region(IR/SC)boundaries of Salvia are highly conserved,and IR contraction only occurred in two species(Salvia mekongensis and ***).In Salvia,sequence divergence was higher in non-coding regions than in coding *** found that using large single copy(LSC)and small single copy regions(SSC)with exclusion of the rapidly evolving sites produced the highest resolution in phylogenetic analysis of Salvia,suggesting that using suitable informative sites to build trees is more conducive in phylogenetic *** study assembled a powerful matrix data set for studying the phylogeny of Salvia,resolving the interspecific relationship of Salvia *** newly sequenced plastid genomes will also enrich the plastome database of Salvia,providing the scientific basis for the development and utilization of germplasm resources of this large and important genus.

关键词： Lamiaceae Salvia subg.Glutinaria Plastome Phylogeny

Harmonic Retrieval in Colored ARMA Noise

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Wuhan University Journal of Natural Sciences 2000年第4期5卷 451-456页

作者： Li Sheng-hong Pan Li Zhu hong-wen Xue Zhi Shanghai jiaotong Univ Shanghai China

We propose a new approach to harmonic retrieval in colored ARMA noise. A suitable filter is first used to remove all the sharp power spectrum peaks of the noisy observed process, then some kinds of cross correlation is employed to identify the noise characteristics. After filtering the noisy observed process with the identified noise characteristics again, SVD-TLS method can be applied to retrieve the harmonics. The proposed approach can be used to retrieve real-valued harmonic signals in colored ARMA noise with no restrictions on the phase coupling of harmonics and the distribution of the noise. Simulation examples show its effectiveness.

关键词： ARMA process harmonic retrieval phase coupling correlation

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薰衣草精油微胶囊释放过程的红外光谱研究

光谱学与光谱分析 2017年第1期37卷 65-69页

作者：管雪丽符继红唐军新疆大学理化测试中心新疆乌鲁木齐830046

为了解薰衣草精油β-环糊精包合物的构成形式和精油随温度变化的缓释过程,利用傅里叶变换红外变换光谱(FTIR)技术,对薰衣草精油(LO)、β-环糊精(β-CD)及薰衣草精油微胶囊(LOM)进行红外光谱对比分析,同时对不同温度下精油缓释过程中微... 详细信息

为了解薰衣草精油β-环糊精包合物的构成形式和精油随温度变化的缓释过程,利用傅里叶变换红外变换光谱(FTIR)技术,对薰衣草精油(LO)、β-环糊精(β-CD)及薰衣草精油微胶囊(LOM)进行红外光谱对比分析,同时对不同温度下精油缓释过程中微胶囊红外光谱变化进行了分析,并结合主成分分析,进一步探究β-CD包埋LO后物理化学稳定性及LO释放过程。结果表明,LO包埋后其特征峰有红移现象、峰形变宽,这主要受形成分子间氢键、p-π共轭现象和β-CD空间结构影响;另外,设定温度变化范围25~95℃,温度间隔10℃,测定LOM的红外光谱,以考证β-CD包埋LO的物理化学稳定性及释放情况,分析实验结果表明,LOM中水合物分子较易失去,LOM中的精油组分物理化学性质稳定,在95℃时逸出量小于6.5%,释放缓慢;对变温红外光谱数据进行主成分分析(PCA),前二个主成分的累积方差为99.3%,通过主成分载荷分析,PC1成分可认为是β-CD特征变量,PC2成分为LO特征变量,主成分结果表明,LOM包埋精油中酯类物质的释放速度要快于醇类物质。采用红外分析方法简便快捷,全面了解包埋精油的物理化学稳定性和释放过程,为薰衣草精油微胶囊释放过程的研究提供新的理论支持。

关键词：薰衣草精油微胶囊 β-环糊精傅利叶红外光谱主成分分析释放

Strategic Priority Program on Space Science

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空间科学学报 2014年第5期34卷 505-515页

作者： WU ji SUN Lilin Certer for Spaoe Science and Appkied Research Chinese Academy of Sciences

In 1957, the launch of the first artificial satellite ushered in a new era for modern space science. The past 50 years' developments in China's space science have witnessed many major missions, and substantial progress has been achieved in space science study, exploration technology as well as experiment technology. Strategic Priority Program on Space Science was officially started in 2011. Through both self-developed space science missions and those with international cooperation,it is expected that the innovative breakthroughs will be realized, leapfrog development of related high-tech will be achieved to establish the important strategic status of space science in national development. To sum up, the implementation of the Strategic Priority Program on Space Science will definitely promote the rapid development of China's space science endeavor, making contributions to China's development and the progress of human civilization.

关键词： Strategic Priority Program on Space Science Science objectives Payload Status

Atomistic simulations of the surface severe plastic deformation-induced grain refinement in polycrystalline magnesium:The effect of processing parameters

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Journal of Magnesium and Alloys 2022年第5期10卷 1242-1255页

作者： Xiaoye Zhou Hui Fu ji-Hua Zhu Xu-Sheng Yang Guangdong Province Key Laboratory of Durability for Marine Civil Engineering School of Civil EngineeringShenzhen UniversityShenzhenGuangdong 518060China State Key Laboratory of Ultra-precision Machining Technology Advanced Manufacturing Technology Research CentreDepartment of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina hong Kong Polytechnic University Shenzhen Research Institute ShenzhenChina

Magnesium(Mg)based alloys are promising candidates for many applications,but their untreated surfaces usually have low strength and *** this study,a single point diamond turning(SPDT)technique was applied to refine the grain size and improve the mechanical properties of the surface layers of Mg-Li *** refining grains in the topmost layer to the nanometer scale(~60 nm),the surface hardness was found to be enhanced by approximately 60%.The atomic plastic deformation process during the SPDT was then studied by the real-time atomistic molecular dynamics(MD)simulations.A series of MD simulations with different combinations of parameters,including rake angle,cutting speed and cutting depth,were conducted to understand their influences on the microstructural evolution and associated plastic deformation mechanisms on the surface layer of the *** MD simulation results suggest that using increased rake angle,cutting speed and cutting depth can help to achieve better grain *** simulation results,which provide atomic-level details of the deformation mechanism,can assist the parameter design for the SPDT techniques to achieve the high-performance heterogeneous nanostructured materials.

关键词： Mg alloy Grain refinement Surface severe plastic deformation MD simulations

Quantum coherence and ground-state phase transition in a four-chain Bose–Hubbard model

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Communications in Theoretical Physics 2021年第8期73卷 182-188页

作者： ji-Guo Wang Lin-Qi Guo Ya-Fei Song Department of Mathematics and Physics Shijiazhuang TieDao UniversityShijiazhuang 050043China Institute of Applied Physics Shijiazhuang TieDao UniversityShijiazhuang 050043China

We study the quantum coherence and ground-state phase transition of a four-chain Bose–Hubbard model with the long-range interaction. In a special four-chain Bose–Hubbard model,i.e., each chain only has one optical potential, four types of the ground-state phases are discovered. The effects of the disorder, the on-site interaction and the long-range interaction on the quantum coherence are studied. For the system without the long-range interaction, the quantum coherence changes from one periodic oscillation to two periodic oscillations as the onsite interaction increases. By considering the long-range interaction, the quantum coherence goes back to one periodic oscillation again. The on-site interaction itself suppresses the quantum coherence, both the on-site interaction and long-range interaction together enhance the quantum coherence with the weak disorder. If the disorder strength is increased beyond a critical value,they start to suppress the quantum coherence. In a regular four-chain Bose–Hubbard model, i.e.,each chain has many optical potentials, the ground-state phase transitions are obtained by using the cluster Gutzwiller mean-field method. Exotic ground-state phases are found, i.e., superfluid phase, integer Mott insulator phase, supersolid phase and loophole insulator phase. The combination of the loophole insulator phase and the supersolid phase expands the lobes with the half-integer filling per site for the small ratio β = t_(‖)/t_(⊥).

关键词： Bose-Hubbard model quantum coherence ground-state phase transition