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Fabrication and characterization of selective laser melting printed Ti–6Al–4V alloys subjected to heat treatment for customized implants design

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Progress in Natural Science:Materials International 2016年第6期26卷 671-677页

作者： Mengke Wang Yuwei Wu Songhe Lu Tong chen Yijiao Zhao hu chen Zhihui Tang 2nd Dental Center School and Hospital of StomatologyPeking University National Engineering Laboratory for Digital and Material Technology of Stomatology School and Hospital of StomatologyPeking University

Selective laser melting（SLM） is a promising technique capable of rapidly fabricating customized implants having desired macro- and micro-structures by using computer-aided design models. However, the SLM-based products often have non-equilibrium microstructures and partial surface defects because of the steep thermal gradients and high solidification rates that occur during the laser melting. To meet clinical requirements, a heat treatment was used to tailor the physiochemical properties, homogenize the metallic microstructures, and eliminate surface defects, expecting to improve the cytocompatibility in vitro. Compared with the as-printed Ti–6Al–4V substrate, the heat-treated substrate had a more hydrophilic, rougher and more homogeneous surface,which should promote the early cell attachment, proliferation and osseointegration. More importantly, a crystalline rutile TiO;layer formed during the heat treatment, which should greatly promote the biocompatibility and corrosion resistance of the implant. Compared to the untreated surfaces, the adhesion and proliferation of human bone mesenchymal stem cells（hBMSCs） on heat-treated substrates were significantly enhanced, implying an excellent cytocompatibility after annealing. Therefore, these findings provide an alternative to biofunctionalized SLM-based Ti–6Al–4V implants with optimized physiochemical properties and biocompatibility for orthopedic and dental applications.

关键词： Selective laser melting(SLM) Titanium alloy Heat treatment Physiochemical properties Cytocompatibility

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Microstructural Evolution of a Hypoeutectoid Pearlite Steel under Rolling-sliding Contact Loading

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Journal of Iron and Steel Research International 2016年第10期23卷 1054-1060页

作者： Qiu-han LI Chi ZHANG hu chen Hao chen Zhi-gang YANG Key Laboratory of Advanced Materials of Ministry of Education School of Materials Science and EngineeringTsinghua University

To study the microstructural evolution of pearlite steel subjected to pure rolling and rolling-sliding contact loading,a hypoeutectoid pearlite steel with composition and microstructure similar to BS11 was designed and twindisc tests of this pearlite steel were performed to simulate the wheel/rail *** a series of twin-disc tests,optical microscope（OM）observation,scanning electron microscope（SEM）observation,X-ray diffraction（XRD）,and micro-hardness tests were conducted to characterize the *** the pure rolling contact condition,a large amount of reticular cracks emerged within 60μm below the contact surface of the samples after 120 000 *** largest deformation was approximately 200μm below the contact *** the rolling-sliding contact condition,the nodularization of pearlite within 100μm below the contact surface was *** microstructure and stress-strain distribution of the area within 2mm below the contact surface were *** distribution of micro-hardness under the contact surface varied with contact *** element method（FEM）was used to simulate the stress-strain *** results of SEM,FEM,and micro-hardness tests indicated that under the pure rolling contact condition,the maximum plastic strain was approximately 200-400μm below the contact ***,under the rolling-sliding contact condition,the maximum plastic strain emerged on the contact *** the pure rolling contact condition,the distribution of micro-hardness was almost identical to that of the equivalent plastic *** the rolling-sliding contact condition,the distribution of micro-hardness was affected by the equivalent plastic strain and tangential stress.

关键词： twin-disc test rail micro-hardness plastic strain finite element method hypoeutectoid pearlite steel rolling-sliding contact

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Up/down-conversion luminescence of monoclinic Gd_(2)O_(3):Er^(3+)nanoparticles prepared by laser ablation in liquid

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Chinese Physics B 2022年第7期31卷 49-55页

作者： hua-Wei Deng Di-hu chen State Key Laboratory of Optoelectronic Materials and Technologies School of Electronics and Information TechnologySun Yat-Sen UniversityGuangzhou 510275China

Multifunctional luminescent materials are attracting attention *** this work,monoclinic Gd_(2)O_(3):Er^(3+)nanoparticles,which possess up-conversion luminescence and down-conversion luminescence properties,were successfully synthesized by laser ablation in liquid(LAL)***-conversion luminescence and down-conversion luminescence of monoclinic Gd_(2)O_(3):Er^(3+)nanoparticles were got under the excitation of 980 nm and 379 nm,*** addition,tunable luminescence was ***,the cytotoxicity of the nanoparticles is low and the fluorescence of the nanoparticles in cell is also strong *** results indicate that the Gd_(2)O_(3):Er^(3+)nanoparticles synthesized by LAL technique are promising candidates for bio-imaging or other fields that require controllable fluorescence.

关键词： Gd_(2)O_(3) nanoparticles luminescence laser ablation in liquid

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Disk-Corona Model in Active Galactic Nuclei: an Observational Test

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Chinese Journal of Astronomy and Astrophysics 2007年第3期7卷 353-363页

作者： Fang Yang chen hu Yan-Mei chen Jian-Min Wang Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 Graduate School of Chinese Academy of Sciences Beijing 100049 National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

We compiled a sample of 98 radio-quiet active galactic nuclei observed by ASCA, Chandra, XMM-Newton, INTEGRAL and Swift with the aim of testing the formation of hot corona and the magnetic shear stress operating in a disk-corona system. We found a strong correlation between the hard X-ray luminosity, bolometric luminosity LBol and Eddington luminosity LEdd, in the sense that the fraction f of hard X-ray to the bolometric luminosity is inversely proportional to the Eddington ratio. This correlation favors the shear stress tensor being of the form of trФ∝ Pgas, with which the disk-corona structure is stable.

关键词： accretion, accretion disks - galaxies active - magnetic fields

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Uniform MnO2 nanostructures supported on hierar- chically porous carbon as efficient electrocatalysts for rechargeable Li-O2 batteries

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Nano Research 2015年第1期8卷 156-164页

作者： Xiaopeng Han Fangyi cheng chengcheng chen Yuxiang hu Jun chen Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) College of Chemistry Collaborative InnovationCenter of Chemical Science and Engineering Nankai University Tianjin 300071 China

Through in situ redox deposition and growth of MnO2 nanostructures on hierarchically porous carbon （HPC）, a MnOR/HPC hybrid has been synthesized and employed as cathode catalyst for non-aqueous Li-O2 batteries. Owing to the mild synthetic conditions, MnO2 was uniformly distributed on the surface of the carbon support, without destroying the hierarchical porous nanostructure. As a result, the as-prepared MnO2/HPC nanocomposite exhibits excellent Li-O2 battery performance, including low charge overpotential, good rate capacity and long cycle stability up to 300 cycles with controlling capacity of 1,000 mAh·g^-1. A combination of the multi-scale porous network of the shell-connected carbon support and the highly dispersed MnO2 nanostructure benefits the transportation of ions, oxygen and electrons and contributes to the excellent electrode performance.

关键词： lithium-oxygen batteries manganese oxide nanocomposite catalyst oxygen electrochemistry

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Theoretical study of the nonlinear force-loading control in single-molecule stretching experiments

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Communications in Theoretical Physics 2024年第4期76卷 167-175页

作者： Xingyu Qi Zilong Guo Shimin Le hu chen Research Institute for Biomimetics and Soft Matter Fujian Provincial Key Lab for Soft Functional Materials ResearchDepartment of PhysicsXiamen UniversityXiamen 361005China Center of Biomedical Physics Wenzhou InstituteUniversity of Chinese Academy of SciencesWenzhou 325000China

Force spectrum measurements with constant loading rates are widely used in single-molecule manipulation experiments to study the mechanical stability and force response of ***-dependent transition rates can be obtained from the transition force distribution,but it is limited to the force range with non-zero force *** constant loading rate control can be realized with magnetic tweezers,the loading rate range is limited due to the slow movement of permanent ***-linear exponential and exponential squared force loading functions are more feasible in magnetic tweezers,while there is no theoretical result available for these two kinds of non-linear force loading *** this study,we solved the unfolding process of a protein following Bell's model under nonlinear exponential and exponential squared force loading functions,which offer a broader range of unfolding force distribution compared to the traditional constant loading rate ***,we derived two force loading functions,which can produce uniform unfolding force *** research contributes fundamental equations for the analysis of experimental data obtained through single-molecule manipulation under nonlinear force loading controls,paving the way for the use of nonlinear force control in magnetic tweezer experiments.

关键词： single-molecule manipulation magnetic tweezers force loading transition rates force distribution

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Dating of the topmost terrace in the Jingxian Basin,Anhui Province:an indication of the establishment of the Qingyijiang River

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Journal of Mountain Science 2017年第3期14卷 549-557页

作者： hu Chun-sheng hu chen-qi LIU Shao-chen XU Guang-lai WU Li YANG Li-hui College of Territorial Resources and Tourism Anhui Normal UniversityWuhu 241000China Anhui Key Laboratory of Natural Disaster Process and Preventing and Controlling Wuhu 241000China

On the northern fringe of Mt. huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang River, one of the longest tributaries of the lower Yangtze River, developed three staircase terraces. The topmost terrace （i.e., the T3 terrace） tread is 38 - 39 m above fiver level, and the top of the gravels is generally covered by 3 - 10.9 m of red clay deposits. Systematic magnetostratigraphy and electron spin resonance dating are used to research the timing of the establishment of the Qingyijiang River. The main results show that the topmost terrace developed no later than 900 kyr ago and that the appearance of the Qingyijiang River occurred correspondingly at least before 900 kyr ago on the northern fringe of Mt. huangshan. In view of the almost synchronous age,the establishment of the Qingyijiang River was seemingly a response to the Mid-Pleistocene Revolution when the 100 kyr cycle commenced, and the Kunlun-huanghe movement during the early- middle Pleistocene transition. In addition, the establishment of the Qingyijiang River possibly reflected the birth of the modem Yangtze River to some degree. Therefore the timing of the formation of the Yangtze River is restricted to no later than 900 kyr ago based on the appearance of the Qingyijiang River .

关键词： Qingyijiang River Topmost terrace Magnetostratigraphy Electron Spin Resonance dating Establishment timing Jingxian Basin

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Performance improvement of lithium-ion battery by pulse current

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Journal of Energy Chemistry 2020年第7期29卷 208-214,I0007页

作者： Shaoqing Zhu chen hu Ye Xu Yi Jin Jianglan Shui School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China State Key Laboratory of Operation and Control of Renewable Energy&Storage Systems China Electric Power Research InstituteBeijing 100192China School of Materials Science and Engineering Beihang UniversityBeijing 100191China

Periodically changed current is called pulse *** has been found that using the pulse current to charge/discharge lithium-ion batteries can improve the safety and cycle stability of the *** this short review,the mechanisms of pulse current improving the performance of lithium-ion batteries are summarized from four aspects:activation,warming up,fast charging and inhibition of lithium *** content may help us use the pulse current to improve the performance of lithium-ion batteries and further optimize pulse current technology.

关键词： Lithium ion battery Pulse current Activation Warming up Fast charging Lithium dendrites

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Quasar SDSS J142507.32+323137.4: dual AGNs?

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Research in Astronomy and Astrophysics 2011年第4期11卷 411-418页

作者： Zhi-Xin Peng Yan-Mei chen Qiu-Sheng Gu chen hu Department of Astronomy Nanjing University Nanjing 210093 China Key Laboratory of Modem Astronomy and Astrophysics （Nanjing University） Ministry of Education Nanjing 210093 China Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China

We analyze the optical spectrum of type 1 QSO SDSS J1425＋3231. This object is interesting since its narrow emission lines, such as [O Ⅲ]λλ4959, 5007, are double-peaked, and the line structure can be modeled well by three Gaussian components： two components for the two peaks （we refer to the peaks at low/high redshift as ＂the blue/red component＂） and another one for the line wing which has the same line center as that of the blue component, but is- 3 times broader. The separation between the blue and red components is -500km s-1 with the blue component being -2 times broader than the red one. The Hβ emission can be separated into four components： two for the double-peaked narrow line and two for the broad line which comes from the broad line regions. The black hole mass estimated from the broad Hβ emission line using the typical reverberation mapping relation is 0.85 × 108 M⊙, which is consistent with that derived from parameters of [O Ⅲ]λ 5007 of the blue component. We suggest that this QSO might be a dual AGN system; the broad Hβ emission line is mainly contributed by the primary black hole （traced by the blue component） while the broad Hβ component of the secondary black hole （traced by the red component） is hard to be separated out considering a resolution of - 2 000 for SDSS spectra or it may be totally obscured by the dusty torus.

关键词： galaxie active -- galaxies individual (SDSS J142507.32+323137.4)-- quasars emission lines

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Impossible differential cryptanalysis of advanced encryption standard

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Science in China(Series F) 2007年第3期50卷 342-350页

作者： chen Jie hu YuPu ZHANG YueYu Key Laboratory of Computer Networks & Information Security Ministry of Education Xidian UniversityXi'an 710071 China

Impossible differential cryptanalysis is a method recovering secret key, which gets rid of the keys that satisfy impossible differential relations. This paper concentrates on the impossible differential cryptanalysis of Advanced Encryption Standard （AES） and presents two methods for impossible differential cryptanalysis of 7-round AES-192 and 8-round AES-256 combined with time-memory trade-off by exploiting weaknesses in their key schedule. This attack on the reduced to 7-round AES-192 requires about 294.5 chosen plaintexts, demands 2129 words of memory, and performs 2157 7-round AES-192 encryptions. Furthermore, this attack on the reduced to 8-round AES-256 requires about 2^101 chosen plaintexts, demands 2^201 words of memory, and performs 2^228 8-round AES-256 encryptions.

关键词： block cipher impossible differential cryptanalysis advanced encryption standard cryptanalysis

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