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Curve Shortening Flow in Arbitrary Dimensional Euclidian Space

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Acta Mathematica Sinica,English Series 2005年第4期21卷 715-722页

作者： yun Yan YANG Xiao xiang JIAO School of Mathematical Sciences Peking University Beijing 100871 P. R. China Graduate School Chinese Academy of Sciences P. R. China

In this paper, curve shortening flow in Euclidian space R^n（n≥3） is studied, and S. Altschuler＇s results about flow for space curves are generalized. We prove that the curve shortening flow converges to a straight line in infinite time if the initial curve is a ramp. We also prove the planar phenomenon when the curve shortening flow blows up.

关键词： Curve shortening flow Singularity formation Blow up

Outage analysis of opportunistic multi-antenna relay selection in decode-and-forward relay networks

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The Journal of China Universities of Posts and Telecommunications 2010年第4期17卷 6-12页

作者： WANG Xiao-xiang ZHENG Zi-yun Key Laboratory of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

This article studies the closed-form expressions of outage performance for opportunistic relay under aggregate power constraint in decode-and-forward （DF） relay networks over Rayleigh fading channels, assuming that multiple antennas are available at the relay node. According to whether instantaneous signal-to-noise ratio （SNR） or average SNR can be utilized for relay selection, two opportunistic relay schemes, opportunistic multi-antenna relay selection （OMRS） and average best relay selection （ABRS） are proposed. The performances of both two schemes are evaluated by means of theoretical analysis and simulation, it is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and closely approaches the beamforming （BF） scheme known as theoretical outage-optimal. Compared with previous single-antenna opportunistic relaying （OR） scheme, OMRS brings remarkable performance improvement, which is obtained from maximum ratio combining （MRC） and beamforming techniques. It is also shown that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.

关键词： relay selection multiple antennas multiple relays decode and forward cooperative networks

Dynamic simulation and optimal control strategy for a parallel hybrid hydraulic excavator

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第5期9卷 624-632页

作者： Xiao LIN Shuang-xia pan Dong-yun WAN State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

The primary focus of this study is to investigate the control strategies of a hybrid system used in hydraulic excavators. First, the structure and evaluation target of hybrid hydraulic excavators are analyzed. Then the dynamic system model including batteries, motor and engine is built as the simulation environment to obtain control results. A so-called multi-work-point dynamic control strategy, which has both closed-loop speed PI (proportion integral) control and direct torque control, is proposed and studied in the simulation model. Simulation results indicate that the hybrid system with this strategy can meet the power demand and achieve better system stability and higher fuel efficiency.

关键词： Hybrid system Hydraulic excavator Multi-work-point dynamic control Direct torque control

Phase precipitation and corrosion properties of copper-bearing ferritic stainless steels by annealing process

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Journal of Iron and Steel Research International 2023年第11期30卷 2280-2292页

作者： Fan Wang De-ning Zou Xing-yu Yan Ying-bo Zhang Ji-xiang pan yun-xia Cheng Ran Xu Yi-cheng Jiang School of Metallurgy and Engineering Xi’an University of Architecture and TechnologyXi’an710055ShaanxiChina Shaanxi Special Equipment Inspection and Testing Institute Xi’an710048ShaanxiChina Jilin Railway Technology College Jilin132200JilinChina Stainless Steel Branch of Gansu Jiu Steel Group Hongxing Iron and Steel Co. Ltd.Jiayuguan735100GansuChina

The effects of different annealing processes on the phase precipitation behavior and corrosion properties of copper-bearing 430 ferritic stainless steel were systematically *** shape,quantity and distribution of copper-rich precipitates by different annealing processes were characterized by scanning electron microscopy,transmission electron microscopy,backscatter electron and backscatter *** pitting resistance behavior in simulated physiological saline envi-ronments(0.9 wt.%NaCl)was investigated using electrochemical workstation and X-ray photoelectron *** results showed that the copper-rich phase prepared by repeated rolling and annealing gradually changed from long needle-like to short thick rod-like and granular,whose distribution tended to be uniform and diffusive,and the number of copper-rich phases *** solution/antibacterial annealing process,the size and density of the copper-rich phase increase,resulting in a discontinuity of the passivation film on the stainless steel,which reduces the pitting resistance to some *** refinement mechanism revealed that pre-deformation brings about a modification in both precipitation mechanism and growth kinetics of epsilon copper.

关键词： 430 stainless steel Annealing Cu-rich phase Pitting corrosion Passivation film

The 2 ℃ Global Temperature Target and the Evolution of the Long-TermGoal of Addressing Climate Change-From the United Nations FrameworkConvention on Climate Change to the Paris Agreement

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Engineering 2017年第2期3卷 272-278页

作者： yun Gao xiang Gao Xiaohua Zhang Department of Sdence & Technology and Climate Change China Meteorological Administration Beijing 100081 China Energy Research Institute National Development and Reform Commission Beijing 100038 China National Center for Climate Change Strategy and International Cooperation (NCSC) Beijing 100038 China

The Paris Agreement proposed to keep the increase in global average temperature to well below 2 ℃ abovepre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 ℃ above pre-industriallevels. It was thus the first international treaty to endow the 2 ℃ global temperature target with legal *** qualitative expression of the ultimate objective in Article 2 of the United Nations Framework Conventionon Climate Change （UNFCCC） has now evolved into the numerical temperature rise target in Article 2 of theParis Agreement. Starting with the Second Assessment Report （SAR） of the Intergovernmental panel on Cli-mate Change （IPCC）, an important task for subsequent assessments has been to provide scientific informa-tion to help determine the quantified long-term goal for UNFCCC negotiation. However, due to involvementin the value judgment within the scope of non-scientific assessment, the IPCC has never scientifically af-firmed the unacceptable extent of global temperature rise. The setting of the long-term goal for addressingclimate change has been a long process, and the 2 ℃ global temperature target is the political consensuson the basis of scientific assessment. This article analyzes the evolution of the long-term global goal foraddressing climate change and its impact on scientific assessment, negotiation processes, and global low-carbon development, from aspects of the origin of the target, the series of assessments carried out by the 1PCCfocusing on Article 2 of the UNFCCC, and the promotion of the global temperature goal at the political level.

关键词： Climate change International negotiationln tergovernmental panel on Climate Change United Nations Framework Convention on Climate ChangeLong-term goal Critical vulnerability Intuitive building

Artificial muscles for wearable assistance and rehabilitation

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Frontiers of Information Technology & Electronic Engineering 2018年第11期19卷 1303-1315页

作者： Tian-yun DONG xiang-liang ZHANG Tao LIU State Key Laboratory of Fluid Power and Mechatronic Systems School of Mechanical Engineering Zhejiang University yunnan Key Laboratory of Computer Kunming University of Science and Technology

Traditional exoskeletons have made considerable contributions to people in terms of providing wearable assistance and rehabilitation. However, exoskeletons still have some disadvantages, such as being heavy, bulky, stiff, noisy, and having a fixed center of rotation that can be a burden on elders and patients with weakened muscles. Conversely, artificial muscles based on soft, smart materials possess the attributes of being lightweight, compact, highly flexible, and have mute actuation, for which they are considered to be the most similar to natural muscles. Among these materials, dielectric elastomer(DE) and polyvinyl chloride(PVC) gel exhibit considerable actuation strain, high actuation stress, high response speed, and long life span, which give them great potential for application in wearable assistance and rehabilitation. Unfortunately, there is very little research on the application of these two materials in these fields. In this review, we first introduce the working principles of the DE and PVC gel separately. Next, we summarize the DE materials and the preparation of PVC gel. Then, we review the electrodes and self-sensing systems of the two materials. Lastly, we present the initial applications of these two materials for wearable assistance and rehabilitation.

关键词： Artificial muscle Smart material Dielectric elastomers (DE) Polyvinyl chloride (PVC)gel Actuator Wearable assistance Rehabilitation

UNSTEADY INTERFACIAL WAVES DUE TO SINGULARITIES IN TWO SEMI-INFINITE INVISCID FLUIDS

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Journal of Hydrodynamics 2005年第6期17卷 730-736页

作者： LU Dong-qiang WEI Gang YOU yun-xiang The State Key Laboratory of Ocean Engineering Shanghai Jiaotong University Shanghai 200030 China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China School of Naval Architecture Ocean and Civil Engineering Shanghai Jiaotong University Shanghai200030 China

The generation of unsteady interfacial gravity waves by a singularity immersed in two semi-infinite fluids was analytically investigated in detail by the methods of integral transform and of stationary-phase analysis. The fluids were assumed to be initially stationary, immiscible, inviscid and incompressible. The disturbed flows, generated by an impulsive and oscillatory source/dipole immersed above or be neath the interface, were governed by the *** equations. The kinematic and dynamic boundary conditions on the interface were linearized for the small-amplitude waves. By means of the stationary phase analysis on the exact integral form solutions, the asymptotic representations for the interracial waves were derived for large time with a fixed distance to time ratio. The relation between a submerged singularity and a sur face pressure point was discussed. It is found that the local wavelength and the local wave period of the interracial waves are elongated in comparison with those of free-surface waves for a single fluid.

关键词： interfacial waves singularity two-fluid system asymptotic representation

Epidemiology and Rb 1 gene of retinoblastoma

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International Journal of Ophthalmology(English edition) 2011年第1期4卷 103-109页

作者： Jun yun, Bo-Rong pan Department of General Surgery Xijing Hospital Fourth Military Medical University Xi'an 710032 Shaanxi Province China Department of Anesthesiology Xijing Hospital Fourth Military Medical University Xi'an 710032 Shaanxi Province China Department of Anatomy and Editorial Office of Chinese Journal of Neuroanatomy Fourth Military Medical University Xi'an 710032 Shaanxi Province China Outpatient Department of Oncology Institute of Tumour Fourth Military Medical University Xi'an 710032 Shaanxi Province China

Retinoblastoma (Rb) is the most common eye cancer in children and it can be inherited. Rb is quite rare and originators from the neural retina with a significant genetic component in etiology, which occurs in approximately 1 in every 20 0000 births. In children with the heritable genetic form of Rb, there is a mutation on chromosome 13, called the retinoblastoma 1 (Rb1) gene. Early diagnosis and intervention is critical to the successful treatment of the Rb. The Rb1 gene is the first cloned tumor suppressor gene. As a negative regulator of the cell cycle, Rb1 gene could maintain a balance between cell growth and development through binding to transcription factors and regulating the expression of genes involved in cell proliferation and differentiation. Thus, it is involved in cell cycle, cell senescence, growth arrest, apoptosis and differentiation. We summarized the recent advances on the epidemiology and Rb1 gene of Rb in this review.

关键词： retinoblastoma epidemiology Rb1 gene structure expression function

Recent progress in Heusler-type magnetic shape memory alloys

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Rare Metals 2015年第8期34卷 527-539页

作者： Guang-Hua Yu yun-Li Xu Zhu-Hong Liu Hong-Mei Qiu Ze-Ya Zhu xiang-Ping Huang Li-Qing pan Department of Materials Physics and Chemistry University of Science and Technology Beijing College of Science China Three Gorges University Department of Physics University of Science and Technology Beijing

Magnetic shape memory alloys(MSMAs), both in condensed matter physics and in material science, are one of the most extensive research subjects. They show prompt response to the external magnetic field and give rise to large strain and have fine reversibility. The well-known example is Heusler-type MSMAs, which possess excellent multifunctional properties and have potential applications in energy transducer, actuator, sensor, microelectromechanical system, and magnetic refrigerator. In this paper, it is shown the recent progress in magnetostructural transformation, magnetic properties, shape deformation, magnetocaloric effect as well as magnetic field-induced shape memory effect in Ni–Mn–Ga, Ni Mn Z(Z = In, Sn, Sb),and Ni Co Mn Z(Z = In, Sn, Sb, Al) Heusler-type *** remaining issues and possible challenges are briefly discussed.

关键词： Heusler alloy Magnetic shape memory alloy Martensi