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A dynamic condition-based maintenance optimization model for mission-oriented system based on inverse Gaussian degradation process

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Journal of Systems Engineering and Electronics 2022年第2期33卷 474-488页

作者： li jingfeng CHEN Yunxiang CAI Zhongyi WANG Zezhou Equipment Management and UAV Engineering College Air Force Engineering UniversityXi’an 710051China

An effective maintenance policy optimization model can reduce maintenance cost and system operation risk. For mission-oriented systems, the degradation process changes dynamically and is monotonous and irreversible. Meanwhile, the risk of early failure is high. Therefore, this paper proposes a dynamic condition-based maintenance(CBM) optimization model for mission-oriented system based on inverse Gaussian(IG) degradation process. Firstly, the IG process with random drift coefficient is used to describe the degradation process and the relevant probability distributions are obtained. Secondly, the dynamic preventive maintenance threshold(DPMT) function is used to control the early failure risk of the mission-oriented system, and the influence of imperfect preventive maintenance(PM)on the degradation amount and degradation rate is analysed comprehensively. Thirdly, according to the mission availability requirement, the probability formulas of different types of renewal policies are obtained, and the CBM optimization model is constructed. Finally, a numerical example is presented to verify the proposed model. The comparison with the fixed PM threshold model and the sensitivity analysis show the effectiveness and application value of the optimization model.

关键词： inverse Gaussian(IG)process imperfect preventive maintenance(PM) mission-oriented system dynamic preventive maintenance threshold(DPMT) maintenance optimization

Processing of advanced thermoelectric materials

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Science China(Technological Sciences) 2017年第9期60卷 1347-1364页

作者： li jingfeng PAN Yu WU ChaoFeng SUN FuHua WEI TianRan State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Beijing 100084 China

Last two decades have witnessed significant progress in thermoelectric research, to which materials processing has crucial contributions. Compared with traditional zone-melting method used for fabricating bismuth telluride alloys, new powder-based processes have more freedom for manipulating nanostructnres and nanocomposites. Thermoelectric performance enhancement is realized in most thermoelectric materials by introducing fine-grained and nano-composite structures with accurately controlled compositions. This review gives a comprehensive summary on the processing aspects of thermoelectric materials with three focuses on the powder synthesis, advanced sintering process and the formation of nanostructures in bulk materials.

关键词： thermoelectrics materials processing nanostructured thermoelectric materials mechanical alloying spark plasmasintering

Development of integrated two-stage thermoelectric generators for large temperature difference

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Science China(Technological Sciences) 2019年第9期62卷 1596-1604页

作者： PEI Jun li liangliang liU DaWei ZHANG BoPing XIAO Yu li jingfeng The Beijing Municipal Key Laboratory of New Energy Materials and Technologies School of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijing 100083China State Key Laboratory of New Ceramics and Fine Processing Tsinghua UniversityBeijing 100084China Huaneng Clean Energy Research Institute Beijing 102209China School of Materials Science and Engineering Beihang UniversityBeijing 100191China

Multi-stage thermoelectric(TE) modules can withstand a large temperature difference and can be used to obtain a high conversion efficiency. In this study, two-stage PbTe/Bi2Te3 TE modules were developed with an enhanced efficiency through a comprehensive study of device structure design, module fabrication, and performance evaluation. PbTe-based AgPbmSbTem+2(abbreviated as LAST) is a typically high ZT material, while the corresponding TE module was rarely reported so far. How to utilize LAST to fabricate high efficiency TE modules therefore remains a central problem. Finite element simulation indicates that the temperature stability of the two-stage module for LAST is better than that of two-segmented module. Compared to Cu,Ni, and Ni-Fe alloys, Co-Fe alloy is an effective metallization layer for PbTe due to its low contact resistance and thin diffusion layer. By sintering a slice of Cu on TE legs, pure tinfoil can be used as a common welding method for mid-temperature TE modules. A maximum efficiency(ηmax) of 9.5% was achieved in the range of 303 to 923 K in an optimized PbTe/Bi2Te3 based two-stage module, which was almost twice that of a commercial TE module.

关键词： PbTe thermoelectric two-stage module finite element method conversion efficiency

A bulk metal/ceramic composite material with a cellular structure

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Chinese Science Bulletin 2006年第2期51卷 235-239页

作者： ZHAO Zhankui YAO Kefu li jingfeng Key Laboratory for Advanced Manufacturing by Materials Processing Technology Department of Mechanical Engineering Tsinghua Uni versity Beijing 100084 China Department of Materials Science and Engineering Changchun University of Technology Changchun 130012 China State Key Laboratory of New Ceramic and Fine Process Tsinghua University Beijing 100084 China

A bulk metal/ceramic composite material with a honeycomb-like micro-cell structure has been prepared by sintering the spherical Al90Mn9Ce1 alloy powders clad by Al2O3 nano-powder with the spark plasma sintering (SPS) technique. The as-prepared material consists of Al90Mn9Ce1 alloy cell and closed Al2O3 ceramic cell wall. The diameter of the cells is about 20―40 μm, while a thickness of the cell wall is about 1―2 μm. The ultimate compressive strength of the as-sintered materials is about 514 MPa, while its fracture strain is up to about 0.65 %. This composite material might possess good anti-corrosion, thermal endurance and other potential properties due to its unique microstructure. The result shows that the Al90Mn9Ce1/Al2O3 composite powders can be sintered by spark plasma sintering technique despite the large difference in their sintering temperature. This work offers a way of designing and preparing metal/ceramic composite material with functional property.

关键词：金属/陶瓷复合材料多孔结构制备方法火花等离子体烧结

Enhancement of thermal stability and high-temperature oxidation resistance of chromium oxide-based films by addition of rare earth element Y

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材料科学技术（英文版） 2024年第21期188卷 105-115页

作者： Bingsen Jia Wenju Xu jingfeng li Xiaohong liu li Ji Chufeng Sun Jia li Hongxuan li State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China School of Chemical Engineering Northwest Minzu UniversityLanzhou 730030China State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China School of Chemical Engineering Northwest Minzu UniversityLanzhou 730030China

Chromium oxide ceramic materials are widely used in high-temperature applications requiring high wear resistance and *** further improve the friction and wear performance and high-temperature sta-bility of chromium oxide thin films,this study attempted to dope rare earth(RE)element Y(yttrium)and deposited CrYO high-temperature self-lubricating ceramic thin films with different doping levels on the surface of IN718 alloys by using multi-arc ion plating *** deposited films were annealed at 1000 ℃ for 2 h under atmospheric conditions to analyze the changes in phase composition and thick-ness,and the friction and wear characteristics of the CrYO films were tested using a high-temperature friction and wear tester in the temperature range of 25-600 ℃.The results show that the CrYO-2 film has a dense multilayer structure,and the multilayer oxide film produces interlayer sliding under fric-tional shear,thus providing *** particular,the friction coefficients are as low as about 0.25 in the middle and high-temperature sections(400,600 ℃),which provides good high-temperature tribolog-ical *** addition,the doping of Y elements dramatically affects the formation of the oxide layer and the distribution of voids in the film,changing the diffusion process of the elements of the base ma-terial inside the film and at the film-air interface at high *** two annealing treatments,the film thickness increased from 1.81 to 2.25 μm,and the volume expansion of the films was effectively controlled compared with that of the Cr2O3 films.

关键词： CrYO film Multilayer structure High-temperature lubrication Thermal stability

Experimental study on the membrane distillation of highly mineralized mine water

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International Journal of Coal Science & Technology 2021年第5期8卷 1025-1033页

作者： Ji Qi Jiafeng Lv Wei Bian jingfeng li Shuqin liu School of Chemical and Environmental Engineering China University of Mining and TechnologyBeijing 100083China State Key Laboratory of Water Resource Protection and Utilization in Coal Mining China Energy Investment CorporationBeijing 100011China

Membrane distillation(MD)is a promising membrane separation technique used to treat industrial *** coupled with cheap heat sources,MD has significant economic ***,MD can be combined with solar energy to realize the large-scale and low-cost treatment of highly mineralized mine water in the western coalproducing region of *** this study,highly mineralized mine water from the Ningdong area of China was subjected to vacuum MD(VMD)using polyvinylidene fluoride hollow-fiber *** optimal operation parameters of VMD were determined by response surface ***,the feasibility of VMD for treating highly mineralized mine water was *** fouling behavior observed during VMD was further investigated by scanning electron microscopy with energy-dispersive X-ray spectroscopy(SEM-EDS).Under the optimal parameters(pressure=-0.08 MPa,temperature=70℃,and feed flow rate=1.5 L/min),the maximum membrane flux was 8.85 kg/(m^(2) h),and the desalination rate was 99.7%.Membrane fouling could be divided into three stages:membrane wetting,crystallization,and fouling layer *** cleaning restored the flux and salt rejection rate to 94%and 97%of the initial values,respectively;however,the cleaning interval and cleaning efficiency decreased as the VMD run time ***-EDS analysis revealed that the reduction in flux was caused by the precipitation of CaCO_(3).The findings also demonstrated that the membrane wetting could be attributed to the formation of NaCl on the cross section and outer surface of the ***,the results confirm the feasibility of MD for treating mine water and provide meaningful guidance for the industrial application of MD.

关键词： Mine water Membrane distillation Operating parameters Membrane fouling

High-temperature Electric Properties of Polycrystalline La-doped CaMnO_3 Ceramics

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Journal of Materials Science & Technology 2009年第4期25卷 535-538页

作者： Jinle Lan Yuanhua lin Ao Mei Cewen Nan Yong liu Boping Zhang jingfeng li State Key Laboratory of New Ceramics and Fine Processing Department of Materials Science and Engineering Tsinghua University Beijing 100084 China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

Polycrystalline La-doped CaMnO3 ceramics have been prepared by a solid-state sintering method. Analysis of microstructure and phase composition indicates that the addition of La can prohibit the further growth of grain, and no impurity phase appears. The results revealed that the La doping can lead to a large change of the activation energy （from 0.2：2 to 0.02 eV）, and thus result in a marked increase in electric conductivity of 2-4 orders of magnitude. The power factor can reach about 1.5×10-4 W.m-1.K-2 in a wide temperature range, which potentially make them attractive for n-type high-temperature thermoelectric materials.

关键词： CaMn03 Thermoelectric Activation energy Seebeck coefficient

Bi-lateral Trade between Sichuan and Pakistan:Current Status,Challenges and Suggestions

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Contemporary Social Sciences 2021年第1期6卷 63-79页

作者： li jingfeng Sichuan Academy of Social Sciences.

This paper analyzes the complementarities of the industrial structures of China’s Sichuan province and Pakistan and clarifies the foundations and current status of the economic and trade exchanges between the two *** Pakistan market is important for Sichuan in terms of location,market capacity,and product *** paper presents detailed suggestions for maintaining and promoting trade between Sichuan and Pakistan and highlights the practical significance and potential value that Pakistan market has for Sichuan.

关键词： CPEC Sichuan Pakistan economic cooperation

Fluoride removal from coal mining water using novel polymeric aluminum modified activated carbon prepared through mechanochemical process

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Journal of Environmental Sciences 2024年第12期146卷 226-236页

作者： Yixiang Bao Yonghui Qi Qiao li Lei Wang Zhiguo Cao Jie li Min Wu Jun Chen Haiqin Zhang Qiang Guo Binbin Jiang Jinkui Zhong jingfeng li State Key Laboratory of Water Resource Protection and Utilization in Coal Mining National Institute of Clean and Low Carbon EnergyBeijing 102209China School of Environmental and Municipal Engineering Lanzhou Jiaotong UniversityLanzhou 730070China China Coal Society Chaoyang DistrictBeijing 100013China Guoneng Shendong Coal Technology Research Institute Yulin 719315China Bulianta Coal Mine Shendong Coal Group Co.Ltd.Erdos 017209China

Defluoridation of coal mining water is of great significance for sustainable development of coal industry in western China.A novel one-step mechanochemical method was developed to prepare polymeric aluminum modified powder activated carbon(PAC)for effective fluoride removal from coal mining *** was stably loaded on the PAC through facile solid-phase reaction between polymeric aluminum(polyaluminum chloride(PACl)or polyaluminum ferric chloride(PAFC))and PAC(1:15 W/W).Fluoride adsorption on PACl and PAFC modified PAC(C-PACl and C-PAFC)all reached equilibrium within 5 min,at rate of 2.56 g mg^(-1)sec^(-1)and 1.31 g mg^(-1)sec^(-1)*** increase of binding energy of Al on C-PACl(Al–F bond:76.64 eV and Al–FOH bond:77.70 eV)relative to that of Al on C-PAFC(Al–F bond:76.52 eV)explained higher fluoride uptake capacity of *** chloride was released from C-PACl than that from C-PAFC due to its higher proportion of covalent chlorine and lower proportion of ionic *** elements mapping and atomic composition proved the stability of Al loaded on the PAC as well as the enrichment of fluoride on both CPACl and *** Bader charge,formation energy and bond length obtained from DFT computational results explained the fluoride adsorption mechanism *** carbon emission was 7.73 kg CO_(2)-eq/kg adsorbent prepared through mechanochemical process,which was as low as 1:82.3 to 1:8.07×10^(4)compared with the ones prepared by conventional hydrothermal methods.

关键词： Fluoride Adsorption Mechanochemistry Polymeric aluminum Powder activated carbon