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Adaptations of the floral characteristics and biomass allocation patterns of Gentiana hexaphylla to the altitudinal gradient of the eastern Qinghai-Tibet Plateau

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Journal of Mountain Science 2017年第8期14卷 1563-1576页

作者： HE Jun-dong XUE Jing-yue GAO Jing WANG Jin-niu WU Yan University of Chinese Academy of Sciences Chengdu Institute of Biology Chinese Academy of Sciences

This study addressed the floral component traits and biomass allocation patterns of Gentiana hexaphylla as well as the relationships of these parameters along an elevation gradient(approximately 3700 m, 3800 m, 3900 m, and 4000 m) on the eastern Qinghai-Tibet Plateau. The plant height, floral characteristics, and biomass allocation of G. hexaphylla were measured at different altitudes after field sampling, sorting, and drying. Plant height was significantly greater at 3700 m than that at other elevations. Flower length was significantly greater at 4000 m than that at other elevations, whereas the flower length at low elevations showed no significant differences. Corolla diameter increased with altitude, although the difference was not significant between 3800 m and 3900 m. Variations in biomass accumulation, including the aboveground, photosynthetic organ, flower and belowground biomasses, showed non-linear responses to changes in altitude. The aboveground and photosynthetic organ biomasses reached their lowest values at 4000 m, whereas the belowground and flower biomassreached minimum values at 3700 m. The sexual reproductive allocation of G. hexaphylla also increased with altitude, with a maximum observed at 4000 m. These results suggest that external environmental factors and altitudinal gradients as well as the biomass accumulation and allocation of G. hexaphylla play crucial roles in plant traits and significantly affect the ability of this species to adapt to harsh environments. The decreased number of flowers observed at higher altitudes may indicate a compensatory response for the lack of pollinators at high elevations, which is also suggested by the deformed flower shapes at high altitudes. In addition, the individual plant biomass(i.e., plant size) had significantly effect on flower length and corolla diameter. Based on the organ biomass results, the optimal altitude for G. hexaphylla in the eastern Qinghai-Tibet Plateau is 3800 m, where the plant exhibits minimum propagule biomass and asexual reproduct

关键词： Biomass allocation, Reproductivestrategy Altitudinal gradient Alpine meadows Floralcharacteristics Gentiana hexaphylla

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CONVERGENCE RATE OF gradient DESCENT METHOD FOR MULTI-OBJECTIVE OPTIMIZATION

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Journal of Computational Mathematics 2019年第5期37卷 689-703页

作者： Liaoyuan Zeng Yuhong Dai Yakui Huang Institute of Computational Mathematics and Scientific/Engineering Computing State Key Labomtory of Scientific and Engineering ComputingAcademy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China School of Science Hebei University of TechnologyTianjin 300401 China

The convergence rate of the gradient descent method is considered for unconstrained multi-objective optimization problems (MOP). Under standard assumptions, we prove that the gradient descent method with constant stepsizes converges sublinearly when the objective functions are convex and the convergence rate can be strengthened to be linear if the objective functions are strongly convex. The results are also extended to the gradient descent method with the Armijo line search. Hence, we see that the gradient descent method for MOP enjoys the same convergence properties as those for scalar optimization.

关键词： Multi-objective optimization gradient descent Convergence rate.

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Perceptual gradient Similarity Deviation for Full Reference Image Quality Assessment

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Computers, Materials & Continua 2018年第9期56卷 501-515页

作者： Manyu Jin Tao Wang Zexuan Ji Xiaobo Shen School of Computer Science and Engineering Nanjing University of Science and TechnologyNanjing210094China School of Computer Science and Engineering Nanyang Technology University639798Singapore

Perceptual image quality assessment(IQA)is one of the most indispensable yet challenging problems in image processing and computer vision.It is quite necessary to develop automatic and efficient approaches that can accurately predict perceptual image quality consistently with human subjective evaluation.To further improve the prediction accuracy for the distortion of color images,in this paper,we propose a novel effective and efficient IQA model,called perceptual gradient similarity deviation(PGSD).Based on the gradient magnitude similarity,we proposed a gradient direction selection method to automatically determine the pixel-wise perceptual gradient.The luminance and chrominance channels are both took into account to characterize the quality degradation caused by intensity and color distortions.Finally,a multi-scale strategy is utilized and pooled with different weights to incorporate image details at different resolutions.Experimental results on LIVE,CSIQ and TID2013 databases demonstrate the superior performances of the proposed algorithm.

关键词： Image quality assessment full reference perceptual gradient similarity multi-scale standard deviation pooling

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Liquid droplet movement on horizontal surface with gradient surface energy

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Science China(Technological Sciences) 2006年第6期49卷 733-741页

作者： LIAO Qiang WANG Hong ZHU Xun LI Mingwei Institute of Engineering Thermophysics Chongqing University Chongqing 400044 China Institute of Engineering Thermophysics Chongqing University Chongqing 400044 China Institute of Engineering Thermophysics Chongqing University Chongqing 400044 China Institute of Engineering Thermophysics Chongqing University Chongqing 400044 China

A surface with gradient surface energy was fabricated on a silicon wafer by using the chemical vapor deposition (CVD) technology with the dodecyltrichlorosilane (C12H25Cl3Si) vapor which was adsorbed chemically on the surface of the silicon wafer to form a self-assemble monolayer (ASM) and thus a gradient profile of wettability. The microscopic contours of the gradient surface were measured with Seiko SPA400 atom force microscope (AFM). And the surface wettability profile was characterized by the sessile drop method, measuring the contact angle of fine water droplets that lay on the gradient surface, to represent the distribution of the surface energy on the surface. Using a high-speed video imaging system, the motion of water droplet on the horizontal gradient surface was visualized and the transient velocity was measured under ambient condition. The experimental results show that the liquid droplets can be driven to move from hydrophobic side to hydrophilic side on the horizontal gradient surface and the velocity of droplet can reach up to 40 mm/s. In addition, the motion of the water droplet can be generally divided into two stages: an acceleration stage and a deceleration stage. The droplet presents a squirming movement on the surface with a lower peak velocity and a larger extent of deceleration motion. And the static advancing contact angle of the droplet is obviously larger than the dynamic advancing contact angle on the gradient energy surface.

关键词： chemical vapor deposition, surface with gradient surface energy, contact angle profile, droplet motion.

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ZnO varistors with high voltage gradient and low leakage current by doping rare-earth oxide

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Science China(Technological Sciences) 2008年第6期51卷 693-701页

作者： HE JinLiang HU Jun LIN YuanHua Sate Key Lab of Power Systems Department of Electrical EngineeringTsinghua UniversityBeijing 100084China State Key Lab of New Ceramics and Fine Processing Department of Material Science and EngineeringTsinghua UniversityBeijing 100084China

The surge arrester of 1000 kV gas-insulated substation (GIS) needs ZnO varistor with high voltage gradient to effectively improve the potential distribution along ZnO varistor column inside the metal-oxide surge arresters. In this paper, the elec-trical and structural parameters of ZnO varistors are changed by doping with some rare-earth oxides, and the mechanism which leads these changes is discussed. When rare-earth oxide additives are added into ZnO varistors, the growing speed is slowed down due to the stabilization of the new spinel phases formed in the grain-boundary by rare-earth oxide additives, then the size of ZnO grains is smaller, and the voltage gradient of varistor increases obviously. By adding suitable amount of oxides of metal Co and Mn, the leakage current can be effectively decreased and the nonlinearity coefficient increased. The novel ZnO varistor samples sintered with the optimal additives have a voltage gradient of 492 V/mm, and the nonlinearity coefficient of 76, but their leakage currents are only 1 μA.

关键词： ZnO varistors rare-earth oxide U-I characteristics voltage gradient leakage current nonlinear coefficient spinel

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FEM solutions for plane stress mode-I and mode-II cracks in strain gradient plasticity

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Science China Mathematics 2000年第9期43卷 969-979页

作者：邱信明郭田福黄克智 Department of Engineering Mechanics Tsinghua University Beijing 100084 China

The strain gradient plasticity theory is used to investigate the crack-tip field in a power law hardening material. Numerical solutions are presented for plane-stress mode I and mode II cracks under small scale yielding conditions. A comparison is made with the existing asymptotic fields. It is found that the size of the dominance zone for the near-tip asymptotic field, recently obtained by Chen et al., is on the order 5% of the intrinsic material length I. Remote from the dominance zone, the computed stress field tends to be the classical HRR field. Within the plastic zone only force-stress dominated solution is found for either mode I or mode II crack.

关键词： fracture plane stress strain gradient plasticity.

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Design and development of SiC/(W,Ti)C gradient ceramic nozzle

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Science China(Technological Sciences) 2008年第1期51卷 77-84页

作者： LIU LiLi DENG JianXin WANG Yi ZHU LiNa Department of Mechanical Engineering Shandong UniversityJinan 250061China School of Mechanical and Electrical Pingyuan UniversityXinxiang 453003China School of Mechanical and Electrical Beijing Jiaotong UniversityBeijing 100045China

The idea of functionally gradient material (FGM) theory was used to design ceramic nozzle based on the erosion wear behaviors of the ceramic nozzles and the out- standing properties of FGM. The purpose is to reduce the tensile stress at the entry region of the nozzle during sand blasting processes. The design theory and methods of gradient ceramic nozzle were proposed. The physical, micromechanical, and composition distribution models of gradient ceramic nozzle were established. The optimum composition distribution of the gradient ceramic nozzle material was determined from the solution of the multi-objective optimization calculation by constructing the models of the composition distribution versus the structural in- tegrity of the compact in fabricating process. Results showed that compressive residual stresses appeared at the entry area of the gradient ceramic nozzle. The optimized component distribution exponent p is 0.5. An SiC/(W,Ti)C gradient ce- ramic nozzle material was synthesized by hot-pressing according to the design result. Results showed that the surface Vickers hardness of the FGM-1 gradient ceramic nozzle materials was greatly improved in comparison with that of the other layers.

关键词： ceramic nozzle erosion wear function gradient material stress Finite element analysis

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Evolution of chlorite composition in the Paleogene prototype basin of Jiyang Depression, Shandong, China, and its implication for paleogeothermal gradient

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Science China Earth Sciences 2007年第11期50卷 1645-1654页

作者： ZHAO Ming1, CHEN XiaoMing1, JI JunFeng1, ZHANG Zhe1 & ZHANG Yun2 1 State Key Laboratory for Mineral Deposits Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, China 2 Jiangsu Survey Institute of Engineering and Physics, Nanjing 210008, China State Key Laboratory for Mineral Deposits Research Department of Earth Sciences Nanjing University Nanjing China Jiangsu Survey Institute of Engineering and Physics Nanjing China

The Dongying Basin, Huimin Basin, and Zhanhua Basin constitute the Jiyang Depression in Shandong Province. They are major oil and gas exploring districts within the depression. Through reconstruc-tions of the paleotemperature of the three basins facilitated with the chlorite geothermometry, the thermal history of the Paleogene prototype basin in Jiyang Depression and its geologic significance were explored. This study reveals that the Si4+ component in chlorites reduces gradually as its buried depth increases, while the AlIV component increases accordingly. The chlorite type changes from sili-con-rich diabantite to silicon-poor ferroamesite and prochlorite. The prochlorite in this district only appears in the deep buried depth, high temperature, and relatively old stratigraphies; while the diaban-tite appears in the shallower buried, low temperature, and newly formed strata; the ferroamesite exists in the conditions between prochlorite and diabantite formation. The diagenetic temperatures of the chlorites in these Paleogene basins are 171―238℃ for the Dongying Basin, 160―202℃ for the Huimin Basin, and 135―180℃ for the Zhanhua Basin. The differences of the chlorite diagenetic temperatures in the three basins were controlled by the duration time of the structural depressing processes. Higher temperature indicates longer depression time. The relationship between the chlorite diagenetic temperature and its buried depth indicates that the average paleogeothermal gradient is about 38.3℃ /km in the Paleogene prototype basin of Jiyang Depression. It was higher than the present geothermal gradient (29―30℃/km). This phenomenon was attributed to the evolution of the structural dynamics in the depression basin.

关键词： Paleogene,Jiyang depression,chlorite component,chlorite geothermometry,paleotemperature,paleogeothermal gradient

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Light-induced nonhomogeneity and gradient bending in photochromic liquid crystal elastomers

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Science China(Physics,Mechanics & Astronomy) 2006年第5期49卷 553-563页

作者： JIN Lihua JIANG Xin HUO Yongzhong Department of Mechanics and Engineering Science Fudan UniversityShanghai 200433China Department of Mechanics and Engineering ScienceFudan UniversityShanghai 200433China Department of Mechanics and Engineering ScienceFudan UniversityShanghai 200433China

The recently reported opto-mechanical effect of some photochromic liquid crystal elastomers (LCEs) is studied. It is found that in such LCEs, material parameters such as the Young’s modulus and the stress-free strains will become nonhomogeneous under light irradiations. One may call them the light-induced functionally gradient materials. Analytical expressions for the dependence of the material parameters on the space varia- ble and possibly on the time variable are obtained. Exponential dependence can be derived under certain approximations. As an example, the light-induced bending of a beam is studied. Two neutral planes are found in the beam. Thus, along the thickness of the beam, there are extensions in the upper and lower parts and contractions in the middle.

关键词： opto-mechanical effect material nonhomogeneity functionally gradient materials light-induced bending

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Preparation of 2024/3003 gradient materials by semi-continuous casting using double-stream-pouring technique

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Journal of Central South University of Technology 2002年第4期9卷 229-234页

作者：李元元费劲陈维平张卫文邵明 Advanced Metallic Materials Research and Processing Technology Center South China University of Technology

The 2024/3003 aluminum gradient alloys are prepared by semi continuous casting. The influences of throttle bore diameter of embedded nozzle and temperature of internal melt on composition distribution, macrostructure, hardness are analyzed, and the stability of gradient distribution of composition, macrostructure and hardness along the axial direction of the ingot is also studied. The results show that diffe rent composition profiles can be achieved by adjusting the processing parameters; the volume fraction of inner alloy in the ingot can be increased by enlarging the throttle bore diameter and elevating the temperature of inner melt; quasi steady solidification can be realized within 20 s during cast processing, and consistent quality ingot is obtained by controlling the casting speed and liquid height of inner melt.

关键词： 2024/3003 Al alloys gradient materials semi-continuous casting

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