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International Journal of Ophthalmology(English edition) 2011年第6期4卷 611-615页

作者： Yao Ni Xia-Lin Liu Ming-Xing Wu Ying Lin Yu-Ying Sun chang he and Yi-Zhi Liu Zhongshan Ophthalmic Center State Key Laboratory of Ophthalmology Sun Yat-sen University Guangzhou 510060 Guangdong Province China

AIM: To quantify the changes in the lens profile with accommodation in different age groups. METHODS: The Pentacam HR system was used to obtain the images of the anterior eye segment from 23 young and 15 presbyopic emmetropic subjects in unaccommodated (with an accommodation stimulus of 0.0D) and accommodated (with an accommodation stimulus of 5.0D for the young group and 1.0D for the presbyopic group) states. The phakic crystalline lens shape, including curvature of crystalline lens and central lens thickness (CLT), and the measurements of anterior segment length (ASL), central anterior chamber depth (CACD) were investigated. The anterior chamber volume (ACV) was also measured. RESULTS: The reduction of CACD and ACV were significant in both groups after accommodation stimulus. From the profile of anterior eye segment, a significant decrease in anterior crystalline lens radii of curvature (-2.52mm) and a mean increase in CLT (0.222mm) and ASL (0.1138mm) were found in the. young group with an accommodation stimulus of 5.0D. However, no statistically significant changes of CLT, ASL, or crystalline lens radii of curvature were found in the presbyopic group. CONCLUSION: Our data showed that the shallowing of anterior chamber during accommodation was caused by the forward bulging of the anterior lens surface, rather than by anterior shifting of lens position in either young or presbyopic subjects.

关键词： accommodation crystalline lens Pentacam HR anterior eye segment

High-Order Two-Scale Asymptotic Paradigm for the Elastodynamic Homogenization of Periodic Composites

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Acta Mechanica Solida Sinica 2024年第1期37卷 124-138页

作者： Wei-Zhi Luo Mu he Liang Xia Qi-chang he State Key Laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China Laboratoire Modélisation et Simulation Multi-Echelle MSME UMR 8208 CNRSUniversite Gustave Eiffel77454 Marne-la-ValléeFrance

The classical two-scale asymptotic paradigm provides macroscopic and microscopic analyses for the elastodynamic homogenization of periodic composites based on the spatial or/and temporal variable,which offers an approximate framework for the asymptotic homogenization analysis of the motion ***,in this framework,the growing complexity of the homogenization formulation gradually becomes an obstacle as the asymptotic order *** such a context,a compact,fast,and accurate asymptotic paradigm is *** work reviews the high-order spatial two-scale asymptotic paradigm with the effective displacement field representation and optimizes the implementation by symmetrizing the tensor to be ***,the modified implementation gets rid of the excessive memory consumption required for computing the high-order tensor,which is demonstrated by representative one-and two-dimensional *** numerical results show that(1)the contrast of the material parameters between media in composites directly affects the convergence rate of the asymptotic results for the homogenization of periodic composites,(2)the convergence error of the asymptotic results mainly comes from the truncation error of the modified asymptotic homogenized motion equation,and(3)the excessive norm of the normalized wavenumber vector in the two-dimensional inclusion case may lead to a non-convergence of the asymptotic results.

关键词： Composites Homogenization Asymptotic analysis Dynamics Dispersion

Gas–liquid two-phase flow in serpentine microchannel with different wall wettability

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Chinese Journal of Chemical Engineering 2017年第7期25卷 874-881页

作者： Yunlong Zhou he chang Tianyu Qi Energy and Power Engineering College Northeast Dianli University Institute of Energy Environment and Economy Tsinghua University

Gas–liquid flow in serpentine microchannel with different surface properties exhibits drastically different flow behavior. With water and air as working fluids, the method of numerical simulation was adopted in this paper based on CLSVOF(coupled level set and volume of fluid method) multiphase model. After verifying the reasonability of the model through experiment, by changing wall properties and Re number(Rehe influences of contact angle and surface roughness on flow regime and Po number were discussed. Moreover, the difference of pressure drop between curve and straight microchannel was also calculated. Beyond that, the combined effect of curve channel and wall properties on flow resistance was analyzed. This paper finds that wall properties have great influence on gas–liquid flow in microchannels not only on flow regime but also flow characteristics. Meanwhile, the pressure drop in curve microchannels is larger than straight. It is more beneficial for fluid flowing when the straight part of microchannel is hydrophilic smooth wall and curve part is hydrophobic with large roughness.

关键词： Serpentine microchannel Computational fluid dynamics Gas-liquid flow Microfluidics

Numerical investigation of the seismic response of a UHV composite bypass switch retrofitted with wire rope isolators

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Earthquake Engineering and Engineering Vibration 2021年第1期20卷 275-290页

作者： Yang Zhenyu Xie Qiang he chang Xue Songtao Department of Civil Engineering Tongji UniversityShanghai 200092China

An ultra-high voltage(UHV)composite bypass switch(BPS)faces increasing seismic challenges when UHV projects extend to high seismic intensity *** UHV composite BPS still generates excessive stress at the bottom section although hollow composite insulators with high flexural strength are *** the standard retrofitting strategy by using stiffer supports cannot reduce stress responses,wire rope isolation is *** optimal design of isolation considers both stress and displacement responses since the slenderness and composite material of insulators contribute to significant *** results show that properly designed isolation can significantly reduce stress without excessive displacement responses.A larger radius configuration helps to improve the applicability of small stiffness isolators under high *** the isolation still cannot satisfy the requirement,smaller stiffness isolators with a larger radius,or isolators with increased loops and smaller radius,can be introduced to gain better energy dissipation capacity and effectiveness in response ***,a three-step design procedure is proposed to increase the damping force but fix the rotational stiffness of ***,the application of wire rope isolation can be extended to UHV composite BPS with a low natural frequency,but conductors with enough redundancy should be used.

关键词： UHV composite bypass switch seismic analysis seismic performance upgrading wire rope isolator

Mechatronic Design of a Synergetic Upper Limb Exoskeletal Robot and Wrench-based Assistive Control

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Journal of Bionic Engineering 2018年第2期15卷 247-259页

作者： Lei he Caihua Xiong Kai Liu Jian Huang chang he Wenbin Chen School of Mechanical Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China School of Automation Huazhong University of Science and Technology Wuhan 430074 China

Upper limb exoskeletal rehabilitation robots are required to assist patients＇ arms to perform activities of daily living according to their motion intentions. In this paper, we address two questions： how to design an exoskeletal robot which can mechanically reconstruct functional movements using only a few actuators and how to establish wrench-based assistive control. We first show that the mechanism replicating the synergic feature of the human upper limb can be designed in a recursive manner, meaning that the entire robot can be constructed from two basic mechanical units. Next, we illustrate that the assistive control for the synergetic exoskeletal robot can be transformed into an optimization problem and a Riemannian metric is proposed to generate anthropomorphic reaching movements according to contact forces and torques. Finally, experiments are carried out to verify the functionality of the proposed theory.

关键词： upper limb exoskeletal robot postural synergy wrench based assistive control

A general solution for Stokes flow and its application to the problem of a rigid plate translating in a fluid

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Acta Mechanica Sinica 2015年第1期31卷 32-44页

作者： Xiang-Yu Li Si-Cong Ren Qi-chang he School of Mechanics and Engineering Southwest Jiaotong University School of Mechanical Engineering Southwest Jiaotong University Universit'e Paris-Est Laboratoire Mod'elisation et Simulation Multi Echelle UMR 8208 CNRS 5 Boulevard Descartes77454 Marne-la-Vall'ee France

A general solution for 3D Stokes flow is given which is different from, and more compact than the exist ing ones and more compact than them in that it involves only two scalar harmonic functions. The general solution deduced is combined with the potential theory method to study the Stokes flow induced by a rigid plate of arbitrary shape trans lating along the direction normal to it in an unbounded fluid. The boundary integral equation governing this problem is derived. When the plate is elliptic, exact analytical results are obtained not only for the drag force but also for the ve locity distributions. These results include and complete the ones available for a circular plate. Numerical examples are provided to illustrate the main results for circular and ellip tic plates. In particular, the elliptic eccentricity of a plate is shown to exhibit significant influences.

关键词： Stokes flow 3D general solutions Potentialtheory method Circular plate Elliptic plate

A New Infeasible-Interior-Point Algorithm for Linear Programming over Symmetric Cones

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Acta Mathematicae Applicatae Sinica 2017年第3期33卷 771-788页

作者： chang-he LIU You-lin SHANG Ping HAN School of Mathematics and Statistics Henan University of Science and Technology College of Mathematics and System Science Shandong University of Science and Technology

In this paper we present an infeasible-interior-point algorithm, based on a new wide neighbourhood N（ t1, t2, η）, for linear programming over symmetric cones. We treat the classical Newton direction as the sum of two other directions. We prove that if these two directions are equipped with different and appropriate step sizes, then the new algorithm has a polynomial convergence for the commutative class of search directions. In particular, the complexity bound is O（r1.5 log ε-1） for the Nesterov-Todd （NT） direction, and O（r2 log ε-1） for the xs and sx directions, where r is the rank of the associated Euclidean Jordan algebra and ε 〉 0 is the required precision. If starting with a feasible point （x0, y0, s0） in N（t1, t2, η）, the complexity bound is O（ √ r log ε-1） for the NT direction, and O（r log ε-1） for the xs and sx directions. When the NT search direction is used, we get the best complexity bound of wide neighborhood interior-point algorithm for linear programming over symmetric cones.

关键词： symmetric cone Euclidean Jordan algebra interior-point methods linear programming polynomial complexity

Upper Yellow River air concentrations of organochlorine pesticides estimated from tree bark, and their relationship with socioeconomic indices

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Journal of Environmental Sciences 2014年第3期26卷 593-600页

作者： chang he Jun Jin Bailin Xiang Ying Wang Zhaohui Ma College of Life and Environmental Sciences Minzu University of China

Organochlorine pesticide （OCP） concentrations in tree bark from the upper Yellow River region were determined. Total OCP concentrations ranged from 2.7 to 82 ng/g dw, with a mean of 20 ng/g dw. Concentrations of total （E） DDTs （0.49-37 ng/g dw）, HCHs （0.55-4.5 ng/g dw）, and HCB （0.1-1.0 ng/g dw） were much higher than the other OCPs and accounted for 89% of the YOCP concentrations. p,p＇-DDT was the dominant member of the DDT pesticide group and [5-HCH was the dominant HCH isomer. The p,p＇-DDT/p,p＇-DDE and ct-HCH/y-HCH ratios suggested that there were recent DDT and y-HCH releases. OCP concentrations in the air were estimated from the tree bark, and the estimated median 3ZDDTs, EHCHs, and HCB concentrations in the air were 0.09, 0.14, and 0.024 pg/m3, respectively. The relationship between total OCP concentrations and socioeconomic and natural environment indices were assessed using multiple linear regression analysis, and a regression equation including all these factors was obtained. Population density and tertiary industry were the two dominant factors that appeared to affect OCP concentrations in the upper Yellow River region.

关键词： North-western China organohalogen willow vegetation atmosphere persistent organic pollutants (POPs)

Significant influence of doping effect on photovoltaic performance of efficient fullerene-free polymer solar cells

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Journal of Energy Chemistry 2020年第4期29卷 40-46页

作者： Qian Kang Qi Wang Cunbin An chang he Bowei Xu Jianhui Hou State Key Laboratory of Polymer Physics and Chemistry Beijing National Laboratory for Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190China

The modification mechanism of the water/alcohol cathode interlayer is one of the most complicated problems in the field of organic photovoltaics,which has not been clearly elucidated yet;this greatly restricts the further enhancement of the PCE for polymer solar ***,we clarified the different effects of PFN and its derivatives,namely,poly[(9,9-bis(3’-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN-Br) in modifying fullerene-free *** is found for the first time that doping on IT-4F by the amino group of PFN leads to the unfavorable charge accumulation,and hence,forms a dense layer of electronegative molecule due to the poor electron transport capacity of the non-fullerene acceptor *** electronegative molecular layer can block the electron transfer from the active layer to the interlayer and cause serious charge recombination at the active layer/cathode *** mechanism could be verified by the ESR measurement and electron-only *** replacing PFN with PFN-Br,the excessive doping effect between the cathode interlayer and IT-4F is eliminated,by which the charge transport and collection can be greatly *** a result,a high PCE of 13.5%was achieved in the fullerene-free PSCs.

关键词： Cathode interlayer Doping effect Electron transport Power conversion efficiency Electron-only device

Red-emission organic light-emitting diodes based on solution-processable molecules with triphenylamine core and benzothiadiazole-thiophene arms

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Science China Chemistry 2011年第4期54卷 695-698页

作者： ZHANG Jing YANG Yi he chang LI YongFang Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Organic SolidsInstitute of ChemistryChinese Academy of SciencesBeijing 100190China

We report red-emission organic light-emitting diodes (OLEDs) based on solution-processable organic molecules with triphenylamine (TPA) as core and benzothiadiazole-(4-hexyl)thiophene (BT-4HT) as ***-armed molecule B(TPA-BT-4HT) and star-shaped (tri-armed) molecule S(TPA-BT-4HT) both show pure red-emission peaked at 646 and 657 nm,*** red-emission OLED with S(TPA-BT-4HT) as the emitting layer displays a higher maximum luminance of ca.7794 cd/m2 and a maximum EL efficiency of 0.91 cd/A.

关键词： red-emission organic molecules solution processability OLEDs