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Inverse Fluid-solid Interaction Scattering Problem Using Phased and Phaseless Far Field Data

Acta Mathematicae Applicatae Sinica 2020年第1期36卷 74-94页

作者： Xia JI yun-fei jia Xiao-dong LIU LSEC Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China Academy of Mathematics and Systems Science Chinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100190China

We consider the inverse fluid-solid interaction scattering of incident plane wave from the knowledge of the phased and phaseless far field *** the phased data,one direct sampling method for location and shape reconstruction is *** inner product is involved in the computation,which makes it very simple and fast to be *** the help of the factorization of the far field operator,we give a lower bound of the proposed indicator functional for the sampling points inside the elastic *** for the sampling points outside,we show that the indicator functional decays like the Bessel function as the points go away from the boundaries of the elastic *** also show that the proposed indicator functional continuously dependents on the far field patterns,which further implies that the novel sampling method is extremely stable with respect to data *** the phaseless data,to overcome the translation invariance,we consider the scattering of point sources *** adding a reference sound-soft obstacle into the scattering system,we show some uniqueness results with phaseless far field ***,we introduce a phase retrieval algorithm to retrieve the phased data without the additional *** novel phase retrieval algorithm can also be combined with the sampling method for phased *** also design two novel direct sampling methods using the phaseless data ***,some numerical simulations in two dimensions are conducted with noisy data,and the results further verify the effectiveness and robustness of the proposed numerical methods.

关键词： fluid-solid interaction scattering direct sampling method far field pattern phaseless phase retrieval

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Gradient Elastic–Plastic Properties of Expanded Austenite Layer in 316L Stainless Steel

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Acta Metallurgica Sinica(English Letters) 2018年第8期31卷 831-841页

作者： Yong jiang Yang Li yun-fei jia Xian-Cheng Zhang jian-Ming Gong School of Mechanical and Power Engineering Nanjing University of TechnologyNanjing 211816China Key Laboratory of Design and Manufacture of Extreme Pressure Equipment Nanjing 211816Jiangsu ProvinceChina Key Laboratory of Pressure System and Safety MOESchool of Mechanical and Power EngineeringEast China Universityof Science and TechnologyShanghai 200237China

The gradient mechanical properties, variation of stress with strain and surface cracking behavior of expanded austenite developed on 316L austenitic stainless steel were investigated by nanoindentation tests, X-ray residual stress analysis and scanning electron microscope observation in four-point bending tests. The results show that the plastic properties of the carburizing layer including true initial yield strengths and strain hardening exponents increase significantly from substrate to surface, while the true elastic modulus just improves slightly. Due to the onset of plastic flow, the residual stresses are almost equivalent to the true initial yield strengths from surface to the depth of ～10 lm. The results of four-point bending tests show that surface stress increases linearly with the increase in strain until the strain reaches～1.0%, after that the plastic yield happens. The expanded austenite surface layer is brittle, and the cracks will be created at the strain of ～1.4%.The cracking stress is about～2.4 GPa.

关键词： Low-temperature gaseous carburization Expanded austenite Nanoindentation Gradient elastic-plastic properties Four-point bending

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Microstructural Evolution, Mechanical Properties and Thermal Stability of Gradient Structured Pure Nickel

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Acta Metallurgica Sinica(English Letters) 2019年第8期32卷 951-960页

作者： Xiao Li Bo Guan yun-fei jia yun-Chang Xin Cheng-Cheng Zhang Xian-Cheng Zhang Shan-Tung Tu Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai 200237China School of Materials Science and Engineering Chongqing UniversityChongqing 400044China AECC Commercial Aircraft Engine Co.LTD Shanghai Engineering Research Center for Commercial Aircraft EngineShanghai 20110&China

The microstructural evolution of pure nickel treated by deep rolling(DR)technique with different indent depths was investigated by means of optical microscopy and transmission electron *** surface roughness,hardness and residual stress distribution along the depth from surface were ***,the DR-treated sample was annealed at temperatures from 300 to 700℃for 2 *** results reveal that dislocation movements are the fundamental mechanisms of gradient grain refinement during the DR *** increasing indent depth of the DR,the gradient microhardness on the cross section of sample significantly increases,the maximum compressive residual stress decreases,and the affecting region of residual stress *** results of thermal stability depict that the microstructure can be stable as temperature up to 300℃,and the abnormal grain growth and annealing twins are observed at 600℃.

关键词： Deep rolling Pure nickel-Microstructural evolution Mechanical properties Thermal stability

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Lamellar aspect-ratio and thickness-dependent strength-ductility synergy in pure nickel during in-situ micro-tensile loading

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Journal of Materials Science & Technology 2023年第26期157卷 89-97页

作者： Zi-Meng Wang yun-fei jia Kai-Shang Li Yong Zhang jia-Dong Cai Xian-Cheng Zhang Hiroyuki Hirakata Shan-Tung Tu Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai 200237China Department of Mechanical Engineering and Science Kyoto UniversityKyoto daigaku-katsuraNishikyo-kuKyoto 615-8540Japan

In order to overcome the trade-offbetween strength and ductility in traditional metallic materials,the gradient lamellar structure was fabricated through an ultrasound-aided deep rolling technique in pure Ni with high stacking fault energy after heat *** gradient lamellar Ni was successively di-vided into three ***-situ micro-tensile tests were performed in different regions to reveal the corresponding microscopic mechanical *** characterization techniques were adopted to explore the effects of microstructural parameters and defects on mechanical *** work demonstrates that the micro-tensile sample with small lamellar thickness and large aspect ratio possesses excellent strength and ductility when the loading direction is parallel to the long side of lamellar grain *** finding is helpful to the design of metallic material microstructure with superior com-prehensive *** one hand,the reason for high strength is that the strength increases with the decrease of lamellar thickness according to the Hall-Petch ***,initial dislocation density also participates in the strengthening *** the other hand,the deformation mechanisms include dislocation slip,grain rotation,and the effects of grain boundaries on dislocations,jointly contributing to good ductility.

关键词： Lamella In-situ micro-tensile test Strength-ductility synergy Aspect ratio Grain rotation

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Influence of grain size on the small fatigue crack initiation and propagation behaviors of a nickel-based superalloy at 650℃

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Journal of Materials Science & Technology 2019年第8期35卷 1607-1617页

作者： Xumin Zhu Congyang Gong yun-fei jia Runzi Wang Chengcheng Zhang Yao Fu Shan-Tung Tu Xian-Cheng Zhang Key Laboratory of Pressure Systems and Safety Ministry of Education School of Mechanical and Power Engineering East China University of Science and Technology Shanghai 200237 China AECC Commercial Aircraft Engine Co. LTD Shanghai Engineering Research Center for Commercial Aircraft Engine Shanghai 201108 China

GH4169 at 650℃ in atmosphere was investigated by using single edge notch tensile specimens. The number of main cracks and crack initiation mechanisms at the notch surface strongly depended on the grain size. The crack initiation life accounted for more percentages of the total fatigue life for the alloy with smaller grain size. The fatigue life generally increased with increasing crack initiation life. The small crack transited to long crack when its length reached 10 times the grain size.

关键词： Fatigue crack initiation Small crack Crack growth rate Grain size effect High temperature

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Grain-refining and strengthening mechanisms of bulk ultrafine grained CP-Ti processed by L-ECAP and MDF

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Journal of Materials Science & Technology 2021年第24期83卷 196-207页

作者： Peng-Cheng Zhao Guang-jian Yuan Run-Zi Wang Bo Guan yun-fei jia Xian-Cheng Zhang Shan-Tung Tu Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai200237China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing400044China

The microstructural evolution and mechanical properties of ultrafine-grained(UFG)CP-Ti after an innovative large-volume equal channel angular pressing(L-ECAP)and multi-directional forging(MDF)were systematically examined using monotonic tensile tests combined with transmission electron microscope(TEM)and electron backscatter diffraction(EBSD)*** refined and homogeneous microstructures were achieved after L-ECAP(8-pass and 12-pass)and MDF(2-cycle and 3-cycle),respectively,where the grain size distribution conformed to lognormal *** grain refinement of450℃L-ECAP is dominated by dynamic recrystallization(DRX)and dynamic recovery(DRV),while that of MDF is dominated by *** iron impurities promote recrystallization by pinning-induced dislocation accumulation so that DRX is prone to occur at iron segregation regions during *** monotonic tensile results show that the strain hardening rate of CP-Ti increases with the decrease of grain size,while the continuous strain hardening ability *** relationship between the average grain size and yield strength is in accordance with Hall-Petch ***,the individual strengthening mechanisms were quantitatively examined by the modified *** results indicate that the strengthening contribution of dislocation accumulation to yield strength is greater than that of grain refinement.

关键词： Equal channel angular pressing Multi-directional forging Ultrafine grain Recrystallization Strain hardening Hall-Petch relation

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Effect of thermal annealing on the microstructure, mechanical properties and residual stress relaxation of pure titanium after deep rolling treatment

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Journal of Materials Science & Technology 2019年第3期35卷 409-417页

作者： Jie Huang Kai-Ming Zhang yun-fei jia Cheng-Cheng Zhang Xian-Cheng Zhang Xian-Feng Ma Shan-Tung Tu Key Laboratory of Pressure Systems and Safety Ministry of Education School of Mechanical and Power Engineering East China University of Science and Technology AECC Commercial Aircraft Engine Co. Ltd. Shanghai Engineering Research Center for Commercial Aircraft Engine Sino-French Institute of Nuclear Engineering and Technology SunYat-Sen University

The aim of this paper was to investigate the effect of thermal annealing on the microstructure, mechanical properties, and residual stress relaxation of deep rolled pure titanium. The microstructure and mechanical properties of the surface modified layer were analyzed by metallographic microscopy, transmission electron microscope and in-situ tensile testing. The results showed that the annealed near-surface layer with fine recrystallized grains had increased ductility but decreased strength after annealing below the recrystallization temperature, where the tensile strength was still higher than that of the substrate. After annealing at the recrystallization temperature, the recrystallized near-surface layer had smaller grain size,similar tensile strength, and higher proportional limit, comparable to those of the substrate. Moreover, the residual stress relaxation showed evidently different mechanisms at three different temperature regions:low temperature(T≤ 0.2 Tm), medium temperature(T≈(0.2–0.3) Tm), and high temperature(T≥ 0.3 Tm).Furthermore, a prediction model was proposed in terms of modification of Zener-Wert-Avrami model,which showed promise in characterizing the residual stress relaxation in commercial pure Ti during deep rolling at elevated temperature.

关键词： Deep rolling Ultra-fine grain Tensile strength Microstructure Residual stress

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Mitophagy in acute central nervous system injuries:regulatory mechanisms and therapeutic potentials

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Neural Regeneration Research 2025年第9期20卷 2437-2453页

作者： Siyi Xu Junqiu jia Rui Mao Xiang Cao yun Xu Department of Neurology Nanjing Drum Tower HospitalClinical College of Jiangsu UniversityNanjingJiangsu ProvinceChina Department of Neurology Nanjing Drum Tower HospitalChinese Academy of Medical Science&Peking Union Medical CollegeNanjingJiangsu ProvinceChina Department of Neurology Nanjing Drum Tower HospitalAffiliated Hospital of Medical SchoolNanjing UniversityNanjingJiangsu ProvinceChina State Key Laboratory of Pharmaceutical Biotechnology and Institute of Translational Medicine for Brain Critical Diseases Nanjing UniversityNanjingJiangsu ProvinceChina jiangsu Key Laboratory for Molecular Medicine Medical School of Nanjing UniversityNanjingJiangsu ProvinceChina Nanjing Neurology Medical Center NanjingJiangsu ProvinceChina

Acute central nervous system injuries,including ischemic stro ke,intracerebral hemorrhage,subarachnoid hemorrhage,traumatic brain injury,and spinal co rd injury,are a major global health *** optimal therapies and improving the long-term neurological functions of patients with acute central nervous system injuries are urgent *** are susceptible to damage after acute central nervous system injury,and this leads to the release of toxic levels of reactive oxygen species,which induce cell ***,a selective form of autophagy,is crucial in eliminating redundant or damaged mitochondria during these *** evidence has highlighted the significant role of mitophagy in acute central nervous system *** this review,we provide a comprehensive overview of the process,classification,and related mechanisms of *** also highlight the recent developments in research into the role of mitophagy in various acute central nervous system injuries and drug therapies that regulate *** the final section of this review,we emphasize the potential for treating these disorders by focusing on mitophagy and suggest future research paths in this area.

关键词： autophagy intracerebral hemorrhage ischemic stroke mitochondria mitochondrial biogenesis mitochondrial quality control mitophagy spinal cord injury subarachnoid hemorrhage traumatic brain injury

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大功率发动机飞轮疲劳开裂研究

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内燃机与配件 2020年第22期 141-142页

作者：费运嘉魏顺冬重型专用车发动机安徽省重点实验室马鞍山243000 安徽华菱汽车有限公司马鞍山243061

发动机飞轮的主要功用是用来贮存作功行程的能量,用于克服进气、压缩、排气行程的阻力和其它阻力,使曲轴能均匀地旋转。飞轮在整个发动机系统中扮演着重要的角色,如果飞轮发生开裂的失效,引起发动机致命失效,并且飞轮的严重开裂失效可... 详细信息

发动机飞轮的主要功用是用来贮存作功行程的能量,用于克服进气、压缩、排气行程的阻力和其它阻力,使曲轴能均匀地旋转。飞轮在整个发动机系统中扮演着重要的角色,如果飞轮发生开裂的失效,引起发动机致命失效,并且飞轮的严重开裂失效可能会引发安全事故。我们针对大功率发动机的飞轮开裂的问题进行了全面的开裂机理分析,并根据分析结果提出了整改措施,很好的解决了飞轮开裂的问题。

关键词：飞轮应力集中开裂

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集束化护理策略对ICU患者ICU综合征的影响分析

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中西医结合心血管病电子杂志 2018年第13期6卷 145-146页

作者：王红王桂玲云佳菲解放军第252医院

目的探讨分析对ICU患者ICU综合征实施集束化护理策略的影响。方法选取2016年11月;017年11月我院收治的ICU综合征患者100例为本次研究的对象,100例患者按照入院号随机的分为对照组和研究组,每组50例,对照患者实施常规护理,研究组患者实... 详细信息

目的探讨分析对ICU患者ICU综合征实施集束化护理策略的影响。方法选取2016年11月;017年11月我院收治的ICU综合征患者100例为本次研究的对象,100例患者按照入院号随机的分为对照组和研究组,每组50例,对照患者实施常规护理,研究组患者实施集束化护理策略,在研究结束后对两组患者的护理满意度和心理状况对比分析。结果对照组ICU患者ICU综合征护理满意度比研究组低,心理状况比研究组差,差异有统计学意义（P<0.05）。结论对ICU综合征患者实施集束化护理策略,能够降低ICU综合征的发生率,提高护理满意度,具有很好的临床价值。

关键词：集束化护理策略 ICU患者 ICU综合征

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