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Fatigue small crack growth threshold determination of a high-Nb TiAl alloy at different temperatures by in-situ observation

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International Journal of Minerals,Metallurgy and Materials 2013年第12期20卷 1192-1197页

作者： Min Zhang Xi-ping Song Long Yu Hong-liang Li Ze-hui Jiao Hui-chen Yu State key laboratory for Advanced Metals and Materials University of Science and Technology Beijing testing Research Center for Aeronautical Materials Beijing Institute of Aeronautical Materials

The purpose of this paper is to estimate the fatigue crack growth threshold of a high-Nb TiAl alloy at the different temperatures based on scanning electron microscopy （SEM） in-situ observation. The results indicated that the fatigue crack growth threshold △Kth of a nearly lamellar high-Nb TiAl alloy with 8% Nb content at room temperature and 750℃ was determined as 12.89 MPa.m^1/2 and 8.69 MPa.m^1/2, respectively. The effect of the elevated temperature on the fatigue crack growth threshold cannot be ignored. At the same time, the early stage of fatigue crack propagation exhibited multicrack initiation and bridge-link behavior.

关键词： titanium aluminum alloys niobium fatigue crack propagation high temperature testing

Design rules for dense and rapid Lissajous scanning

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Microsystems & Nanoengineering 2020年第1期6卷 158-164页

作者： Junya Wang Gaofei Zhang Zheng You Department of Precision instrument Tsinghua UniversityBeijingChina State key laboratory of Precision testing Technology and instruments Tsinghua University10084 BeijingChina Information Engineering University ZhengzhouChina

Lissajous microscanners are very popular in compact laser-scanning applications,such as solid-state light detection and ranging(LIDAR),owing to their high-quality factor and low power *** the Lissajous scanner driven by a two-axis micro-electro-mechanical system scanning mirror(MEMS-SM),the design theory is insufficient to meet the temporal and spatial resolution at the same *** this paper,the greatest common divisor of the two-axis driving frequency is used as the temporal resolution,the concept of the fill factor(FF)is used to describe the spatial resolution of the scanner,and a general algorithm for calculating the FF is *** with the characteristics of the Lissajous trajectory,three design rules of the general Lissajous scanner are proposed,and the design theory of the Lissajous scanner enabling MEMS LIDAR is *** results show that the proposed design rules can effectively meet the LIDAR design requirements.

关键词： scanner LIDAR scanning

High-order soliton generation in dispersion flattened fiber

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Chinese Optics Letters 2006年第6期4卷 318-319页

作者：贾东方谈斌王肇颖葛春风杨天新倪文俊李世忱 key laboratory of Opto-Electronics Information and Technical science of Ministry of Education College of Precision instrument and Optoelectronics Engineering Tianjin University

By using the amplified 10-GHz, 5.5-ps sech^2 pulses with high quality and chirp-free from regeneratively mode-locked fiber laser （RMLFL） as the soliton source, 2 -5 order optical soliton phenomena are observed successfully in a 4.28-km dispersion flattened fiber. The experimental results agree well with the theoretical calculation.

关键词： Calculations Dispersions Fiber lasers Laser pulses

A high-power high-stability Q-switched green laser with intracavity frequency doubling using a diode-pumped composite ceramic Nd:YAG laser

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Chinese Physics B 2012年第9期21卷 315-320页

作者：王与烨徐德刚刘长明王卫鹏姚建铨 Institute of Laser and Optoelectronics College of Precision Instrument and Optoelectronics EngineeringTianjin University key laboratory of Optoelectronics Information science and Technology Tianjin UniversityMinistry of Education

We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd：YAG in a straight piano-concave cavity. The temperature distribution in composite ceramic Nd：YAG crystal is numerically analyzed and compared with that of conventional Nd：YAG crystal. By using a composite ceramic Nd：YAG rod and a type-II high gray track resistance KTP （HGTR-KTP） crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd：YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.

关键词： high-average-power green laser high stability composite ceramic Nd:YAG rod

Optical properties of ytterbium-doped tandem-pumped fiber oscillator

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Chinese Physics B 2014年第1期23卷 239-244页

作者：郝金坪闰平肖起榕李丹巩马理 Center for Photonics and Electronics State Key Laboratory of Tribology Department of Precision Instrument Tsinghua University Beijing 100084 China science and Technology on Solid State Laser laboratory Beijing 100015 China

With the rapid development of ytterbium-doped fiber lasers, some obtrusive limitations on power scaling appeared. In order to avoid these problems, a scheme called tandem pumping is introduced into the fiber laser field. In this paper, the optical properties of an ytterbium-doped tandem-pumped fiber oscillator are presented. According to the oscillator profile, the proper gain fiber type and pump wavelength range are picked out, under the comprehensive consideration of laser conversion efficiency and beam quality. In addition, the photodarkening performances of tandem pumping lasers and conventional ones are compared based on practical application, with all possible impact parameters taken into account. Moreover, an all-fibered tandem-pumped oscillator centered at 1079.5 nm is built, in the way of clad pumping by a 1030-nm fiber laser. The laser power of the oscillator reaches 7 W, with an opto-optic efficiency of 82.4%.

关键词： ytterbium-doped fiber laser tandem-pumped fiber oscillator premium pump wavelength photo-darkening performances

Time-dependent diffusion magnetic resonance imaging:measurement,modeling,and applications

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Journal of Zhejiang University-science A(Applied Physics & Engineering) 2024年第10期25卷 765-787页

作者： Ruicheng BA Liyi KANG Dan WU key laboratory for Biomedical Engineering of Ministry of Education Department of Biomedical EngineeringCollege of Biomedical Engineering&Instrument ScienceZhejiang UniversityHangzhou 310027China

Increasingly,attention is being directed towards time-dependent diffusion magnetic resonance imaging(TDDMRI),a method that reveals time-related changes in the diffusional behavior of water molecules in biological tissues,thereby enabling us to probe related microstructure *** ongoing improvements in hardware and advanced pulse sequences,significant progress has been made in applying TDDMRI to clinical *** development of accurate mathematical models and computational methods has bolstered theoretical support for TDDMRI and elevated our understanding of molecular *** this review,we introduce the concept and basic physics of TDDMRI,and then focus on the measurement strategies and modeling approaches in short-and long-diffusion-time ***,we discuss the challenges in this field,including the requirement for efficient scanning and data processing technologies,the development of more precise models depicting time-dependent molecular diffusion,and critical clinical applications.

关键词： Time-dependent diffusion Diffusion magnetic resonance imaging(dMRI) Microstructure imaging Microstructural model

Evaluation of Impact Damage Tolerance in Carbon Fabric/epoxy-matrix Composites by Electrical Resistance Measurement

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Journal of Wuhan University of Technology(Materials science) 2012年第3期27卷 484-488页

作者：李志鹏谢小林 key laboratory of Nondestructive testing (Nanchang Hangkong University) Ministry of Education

Impact damage tolerance is provided in intensity design on composites. The compression intensity of impacted composites requires more than 60% of its original intensity. The influence of impact on compressive intensity and electrical resistance of carbon fabric/epoxy-matrix composites was studied in this paper. The experimental results shows that impact can cause damage in composites, degenerate compressive intensity, and increase resistance. The electrical resistance change rate was used as an evaluation indicator of impact damage tolerance of composites. Impact damage, which results from the applying process of composites, can be identified in time by electrical resistance measurement. So, the safety performance of composites can also be improved.

关键词： carbon fabric/epoxy-matrix composites impact damage tolerance compressive intensity after impacted electrical resistance measurement

Quantitative analysis of the tribological properties of phosphate glass at the nano- and macro-scales

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Friction 2021年第5期9卷 1138-1149页

作者： Huimin QI Wen HU Hongtu HE Yafeng ZHANG Chenfei SONG Jiaxin YU key laboratory of testing Technology for Manufacturing Process in Ministry of Education State Key Laboratory of Environment-friendly Energy MaterialsSouthwest University of Science and TechnologyMianyang 621010China National United Engineering laboratory for Advanced Bearing Tribology Henan University of Science and TechnologyLuoyang 471023China

Processing(grinding,polishing)of phosphate laser(PL)glass involves material removal at two vastly different(spatial)*** this study,the nano‐and macro‐tribological properties of PL glass are investigated by rubbing the glass against a SiO_(2) counter‐surface in both dry and humid *** results indicate that the friction of the PL glass/SiO_(2) pair has opposing trends at the nano‐and *** the nanoscale,the friction coefficient(COF)in humid air is much higher than in dry air,which is attributed to the capillary effect of the absorbed water‐film at the *** the macroscale,on the other hand,the COF in humid air is lower than in dry air,because the water‐related mechanochemical wear makes the worn surface less susceptible to *** removal for PL glass is better facilitated by humid air than by dry air at both scales,because the stress‐enhanced hydrolysis accelerates the material‐removal process in ***,the material‐removal is more sensitive to contact pressure at the macroscale,because stronger mechanical‐interaction occurs during material removal at the macroscale with the multi asperity contact *** the macroscale,the material removal is more sensitive to contact pressure in humid air compared to dry *** almost all mechanical energy is used to remove material in humid air,and most of the mechanical energy is used to produce cracks in PL glass in dry *** results of this study can help optimize the multi‐scale surface processing of optical glasses.

关键词： phosphate glass friction wear water hydrolysis tribochemistry

Tunable single emitter-cavity coupling strength through waveguide-assisted energy quantum transfer

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Light(science & Applications) 2024年第9期13卷 1779-1788页

作者： Yuan Liu Hongwei Zhou Linhan Lin Hong-Bo Sun Department of Precision instrument State Key Laboratory of Precision Measurement Technology and InstrumentsTsinghua UniversityBeijing 100084China State key laboratory of Integrated Optoelectronics College of Electronic Science and EngineeringJilin UniversityChangchun 130012China

The emitter-cavity strong coupling manifests crucial significance for exploiting quantum technology,especially in the scale of individual ***,due to the small light-matter interaction cross-section,the single emitter-cavity strong coupling has been limited by its harsh requirement on the quality factor of the cavity and the local density of optical ***,we present a strategy termed waveguide-assisted energy quantum transfer(WEQT)to improve the single emitter-cavity coupling strength by extending the interaction *** ancillary emitters are optically linked by a waveguide,providing an indirect coupling channel to transfer the energy quantum between target emitter and *** enhancement factor of coupling strength eg=g>10 can be easily achieved,which dramatically release the rigorous design of *** an extension of concept,we further show that the ancillae can be used as controlling bits for a photon gate,opening up new degrees of freedom in quantum manipulation.

关键词： quantum coupling transfer