检索结果-南通市图书馆

Quantitative reorientation behaviors of macro-twin interfaces in shape-memory alloy under compression stimulus in situ TEM

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2022年第12期107卷 243-251页

作者： Bin Chen Chaoshuai Guan yong li Chong Yang Junwei Zhang Gang liu lingwei li yong Peng School of Materials and Energy Electron Microscopy Centre of Lanzhou University and Key Laboratory of Magnetism and Magnetic Materials of the Ministry of EducationLanzhou UniversityLanzhou 730000China Key Laboratory of Novel Materials for Sensor of Zhejiang Province Institute of Advanced Magnetic MaterialsHangzhou Dianzi UniversityHangzhou 310012China School of Materials Science and Engineering Xi’an Jiaotong UniversityXi’an 710000China

Twinning stress is known to be a critical factor for the actuating performance of magnetic shape memory alloys because of the harmful deterioration of their magnetic field-induced strain ***,the intrinsic origin of the high twinning stress is still in *** this work,we firstly fill this gap by precisely probing the reorientation behaviors of A-C and A-B two common macro-twin interfaces under the stimulus of uniaxial compression in-situ transmission electron *** grain boundary is proved to be the main reason for large twinning *** twinning stress of the A-C and A-B type interfaces quantitatively are~0.69 and 1.27 MPa within the plate *** A-C type interface evidently has smaller twinning stress and larger deformation variable than the A-B *** the action of compression,not only the orientations of the crystals have changed,but also the roles of the major and minor lamellae have changed for both interfaces due to the movements of twinning *** insitu and quasi in-situ electron diffraction data,the reorientation process is clearly and intuitively shown by the stereographic *** models and the theory of dislocation motion are proposed to phenomenologically clarify the intrinsic *** work is believed to not only provide a deeper understanding of the deformation mechanism of magnetic shape memory alloys under uniaxial compression testing,but also discover that compression training is not the mechanical training way to decrease the twinning stress of non-modulated martensite in single crystal shape memory alloys.

关键词： Magnetic shape memory alloys Non-modulated martensite Reorientation behavior Twinning stress In-situ TEM

Flow-accelerated corrosion behavior of 13Cr stainless steel in a wet gas environment containing CO_2

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2018年第7期25卷 779-787页

作者： yong li Min-dong Chen Jian-kuan li Long-fei Song Xin Zhang Zhi-yong liu Corrosion and Protection Centre Key Laboratory for Corrosion and Protection（MOE）National Environmental Corrosion Platform（NECP）University of Science and Technology BeijingBeijing 100083China Nuclear and Radiation Safety Center Ministry of Environmental Protection of P.R.ChinaBeijing 100082China

This work investigated the flow-accelerated corrosion （FAC） behavior of 13Cr in a wet CO2-containing environment at different flowing gas velocities mid impinging mlgles, with the natural-gas pipeline environment simulated by a self-assembled impingement jet sys- tem. Surface molphology determination, electrochemical measurements, mid hydromechaziics numerical analysis were cmlied out to study the FAC behavior. The results demonstrate that pitting corrosion was the primary mode of corrosion in 13Cr stainless steel. High-flow-rate gas destroyed the passive film mid decreased the pitting potential, resulting in more serious corrosion. The corrosion degree witk various im- pact mlgles showed the following order： 90~ 〉 60~ 〉 45~. The shear force and the electrolyte from the flowing gas were concluded to be the determinm^t factors of FAC, whereas the shear force was the main factor responsible for destroying the passive film.

关键词： flow-accelerated corrosion jet loop flowing velocity impact magle C02

Numerical Modelling of Wash Waves Generated by Ships Moving over An Uneven Bottom

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2023年第1期37卷 145-153页

作者： li Ming-xin YUAN Zhi-ming BAI Xu li yong-zheng CHENG yong TAO Long-bin School of Naval Architecture and Ocean Engineering Jiangsu University of Science and TechnologyZhenjiang 212100China Department of Naval Architecture Ocean and Marine EngineeringUniversity of StrathclydeGlasgow G11XQUK

Unsteady wash waves generated by a ship with constant speed moving across an uneven bottom topography are investigated by numerical simulations based on a Mixed Euler–Lagrange(MEL) method. The transition is accomplished by the ship traveling from the depth h1 into the depth h2 via a step bottom. A small tsunami would be created after this transition. However, the unsteady wave-making resistance induced by this new phenomenon has not been well documented by literature. Therefore, the main purpose of the present study is to quantify the effects of an uneven bottom on the unsteady wash waves and wave-making resistance acting on the ship. An upwind differential scheme is commonly used in the Euler method to deal with the convection terms under free-surface condition to prevent waves in the upstream. Evidently, it cannot be applied to the present problem due to upstream waves generated by the ship would be dampened by the upwind scheme. The central differential scheme provides more accurate results,but it is not unconditionally stable. An MEL method is therefore employed to investigate the upstream wave generated by the ship moving over the uneven bottom. Simulation results show that the hydrodynamic interaction between the ship and the uneven bottom could initiate an upstream tsunami, as well as unsteady wave-making resistance on *** unsteady wave-making resistance oscillates periodically, and the amplitude and period of the oscillations are highly dependent on speed and water depth.

关键词： uneven bottom upstream wave unsteady wave resistance numerical simulation periodic oscillation

Transient Dynamics of light Propagation in A-Atom EIT Medium

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2005年第2X期44卷 356-364页

作者： li yong liU Xu-Feng Institute of Theoretical Physics the Chinese Academy of Sciences Beijing 100080 China Interdisciplinary Center of Theoretical Studies the Chinese Academy of Sciences Beijing 100080 China Department of Mathematics Peking University Beijing 100871 China

We investigate the transient phenomenon or property of the propagationof an optical probe field in a medium consisting of many A-type three-level atoms coupled to this probe field and a classical driven field. We observe a hidden symmetry and obtain an exact solution for this light propagation problem by means of the spectral generating method. This solution enlightens us to propose a practical protocol implementing the quantum memory robust for quantum decoherence in a crystal. As a transient dynamic process this solution also manifests an exotic result that a wave-packet of light will split into three packets propagating at different group velocities. It is argued that "super-luminal group velocity" and "sub-luminal group velocity" can be observed simultaneously in the same system. This interesting phenomenon is expected to be demonstrated experimentally.

关键词： electromagnetically induced transparency group velocity collective excitation polariton

Broadband impedance modulation via non-local acoustic metamaterials

在线全文

学校读者我要写书评

暂无评论

National Science Review 2022年第8期9卷 47-54页

作者： Zhiling Zhou Sibo Huang Dongting li Jie Zhu yong li Institute of Acoustics School of Physics Science and EngineeringTongji University Department of Mechanical Engineering The Hong Kong Polytechnic University The Hong Kong Polytechnic University Shenzhen Research Institute

Causality of linear time-invariant systems inherently defines the wave-matter interaction process in wave physics. This principle imposes strict constraints on the interfacial response of materials on various physical platforms. A typical consequence is that a delicate balance has to be struck between the conflicting bandwidth and geometric thickness when constructing a medium with desired impedance, which makes it challenging to realize broadband impedance modulation with compact structures. In pursuit of improvement, the over-damped recipe and the reduced excessive response recipe are creatively presented in this work. As a proof-of-concept demonstration, we construct a metamaterial with intensive mode density that supports strong non-locality over a frequency band from 320 Hz to 6400 Hz. Under the guidelines of the over-damped recipe and the reduced excessive response recipe, the metamaterial realizes impedance matching to air and exhibits broadband near-perfect absorption without evident impedance oscillation and absorption dips in the working frequency band. We further present a dual-functional design capable of frequency-selective absorption and reflection by concentrating the resonance modes in three frequency bands. Our research reveals the significance of over-damped recipe and the strong non-local effect in broadband impedance modulation, which may open up avenues for constructing efficient artificial impedance boundaries for energy absorption and other wave manipulation.

关键词： impedance modulation acoustic absorption non-local metamaterials

Study on the Overload and Dwell-Fatigue Property of Titanium Alloy in Manned Deep Submersible

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

China Ocean Engineering 2020年第5期34卷 738-745页

作者： WANG Ke WU li li yong-zheng SUN Xiao-peng School of Naval Architecture and Ocean Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China

With the rapid development of ocean technology, the deep-sea manned submersible is regarded as a high-tech equipment for the exploration and exploitation of ocean resources. The safety of manned cabin has a decisive effect on the whole system. Ti-6 Al-4 V with the superior strength-to-weight ratio and corrosion resistance has been used for the manned cabin. The manned cabin experiences loading spectrum with different maximum stresses and different dwell time during their service life. The load sequence effects on dwell fatigue crack growth behavior of Ti-6 Al-4 V under different dwell time are investigated experimentally in this paper. The experimental results show that the crack tip plastic zone is enlarged by the dwell time and the overload retardation zone increases with dwell time under the same overload rate. A dwell fatigue crack growth model is proposed by modifying the crack tip plastic zone under the loading history with combinations of the single overload and dwell time factors are included in the modified model. Based on the experimental data, the overload retardation zone and the crack growth rates of Ti-6 Al-4 V are predicted by the modified model. A reasonable model for the load sequence effect on the dwell fatigue crack growth rates of Ti-6 Al-4 V is verified.

关键词： manned cabin dwell fatigue crack growth rate Ti-6Al-4V load sequence effect

Gnomon shadow lengths recorded in the Zhoubi Suanjing:the earliest meridian observations in China?

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2009年第12期9卷 1377-1386页

作者： yong li Xiao-Chun Sun National Astronomical Observatories Chinese： Academy of Sciences Beijing 100012 China Institute for the History of Natural Science Chinese Academy of Sciences Beijing 100010 China

The Zhoubi Suanjing, one of the most important ancient Chinese books on mathematical astronomy, was compiled about 100 BC in the Western Han dynasty （BC 206 - AD 23）. We study the gnomon shadow lengths for the 24 solar terms as recorded in the book. Special attention is paid to the so-called law of ‘cun qian li’, which says the shadow length of a gnomon of 8 chi （about 1.96 m） high will increase （or decrease） 1 cun （1/10chi） for every 10001i （roughly 400kin） the gnomon moves northward （or south- ward）. From these data, one can derive the time and location of the observations. The resuits, however, do not fit historical facts. We suggest that compilers of the Zhoubi Suanjing must have modified the original data according to the law of ‘cun qian li’. Through reversing the situation, we recovered the original data, our analysis of which reveals the best possible observation time as 564 BC and the location of observation as 35.78° N latitude. We conclude that this must be the earliest records of solar meridian observations in China. In the meantime, we give the errors of solar altitudes for the 24 solar terms. The average deviation is 5.22°, and the mean absolute deviation is 5.52°, signifying the accuracy of astronomical calculations from that time.

关键词： history and philosophy of astronomy -- solar meridian observation -- ac-curacy -- solar-terrestrial relations -- methods: statistical

Existence of Periodic Solutions for p-Laplacian Equation under the Frame of Fuoik Spectrum

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2011年第3期27卷 545-554页

作者： Wen Bin liU yong li Department of Mathematics China University of Mining and Technology Xuzhou 221008 P. R. China College of Mathematics Jilin University Changchun 130012 P. R. China

In this paper, under the frame of Fuoik spectrum, we study the existence of periodic solutions for p-Laplacian equation by asymptotic behaviors of potential function, improve some results to some extent.

关键词： p-Laplacian equation periodic solution Fuoik spectrum potential function

Micro-Newton scale variable thrust control technique and its noise problem for drag-free satellite platforms:a review

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第10期24卷 841-858页

作者： Changyi XU Wenya li Xuhui liU yong li Chao ZHANG School of Control Science and Engineering Dalian University of TechnologyDalian 116024China Beijing Institute of Control Engineering Beijing 100190China State Key Laboratory of Fluid Power&Mechatronic Systems School of Mechanical EngineeringZhejiang UniversityHangzhou 310058China

High-precision detection in fundamental space physics,such as space gravitational wave detection,high-precision earth gravity field measurement,and reference frame drag effect measurement,is the key to achieving important breakthroughs in the scientific study of fundamental space *** high-precision measurements requires high-performance satellite platforms to achieve“drag-free control”in a near“pure gravity”flight *** critical technology for drag-free control is variable thrust control at the micro-Newton *** noise is the most important technical indicator for achieving drag-free ***,there is no literature about the current status and future prospects of variable thrust control based on thrust ***,the micro-Newton variable thrust control technology and the thrust noise of the drag-free satellite platform are reviewed in this ***,the research status of micro-Newton scale variable thrust control technology and its applications to drag-free satellite platforms are ***,the noise problem is analyzed in detail and its solution is theoretically investigated in three aspects:“cross-basin flow problem,”“control problem,”and“system instability and multiple-coupled problem.”Finally,a systematic overview is presented and the corresponding suggested directions of research are *** work provides detailed understanding and support for realizing low-noise variable thrust control in the next generation of drag-free satellites.

关键词： Space physics detection Satellite platforms Drag-free control Micro-Newton scale variable thrust Thrust noise