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燃料电池 7

固体氧化物燃料电池 6

干细胞 3

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Genetic evidence in planar cell polarity signaling pathway in human neural tube defects

null

《医学前沿（英文）》 2014年第8卷第1期页码 68-78 doi: 10.1007/s11684-014-0308-4

摘要：

Neural tube defects (NTDs) are a group of birth anomalies having a profound physical, emotional, and financial effects on families and communities. Their etiology is complex, involving environmental and genetic factors that interact to modulate the incidence and severity of the developing phenotype. The planar cell polarity (PCP) pathway controls the process of convergent extension (CE) during gastrulation and neural tube closure and has been implicated in the pathogenesis of NTDs in animal models and human cohorts. This review summarizes the cumulative results of recent studies on PCP signaling pathway and human NTDs. These results demonstrate that PCP gene alterations contribute to the etiology of human NTDs.

关键词： planar cell polarity neural tube defects rare mutations

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Loss of liver kinase B1 causes planar polarity defects in cochlear hair cells in mice

null

《医学前沿（英文）》 2016年第10卷第4期页码 481-489 doi: 10.1007/s11684-016-0494-3

摘要：

The tumor suppressor gene liver kinase B1 (LKB1), also called STK11, encodes a serine/threonine kinase. LKB1 plays crucial roles in cell differentiation, proliferation, and polarity. In this study, LKB1 conditional knockout mice (LKB1^Pax2 CKO mice) were generated using Pax2-Cre mice to investigate the function of LKB1 in inner ear hair cells during early embryonic period. LKB1^Pax2 CKO mice died perinatally. Immunofluorescence and scanning electron microscopy revealed that stereociliary bundles in LKB1^Pax2 CKO mice were clustered and misoriented, respectively. Moreover, ectopic distribution of kinocilium bundles resulting from abnormal migration of kinocilium was observed in the mutant mice. The orientation of stereociliary bundles and the migration of kinocilia are critical indicators of planar cell polarity (PCP) of hair cells. LKB1 deficiency in LKB1^Pax2 CKO mice thus disrupted hair cell planar polarity during embryonic development. Our results suggest that LKB1 is required in PCP formation in cochlear hair cells in mice.

关键词： LKB1 stereociliary bundles kinocilium planar cell polarity hearing mice

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Numerical investigation of the chemical and electrochemical characteristics of planar solid oxide fuelcell with direct internal reforming

Yuzhang WANG, Shilie WENG, Yiwu WENG

《能源前沿（英文）》 2011年第5卷第2期页码 195-206 doi: 10.1007/s11708-011-0148-8

摘要： A fully three-dimensional mathematical model of a planar solid oxide fuel cell (SOFC) with complete direct internal steam reforming was constructed to investigate the chemical and electrochemical characteristics of the porous-electrode-supported (PES)-SOFC developed by the Central Research Institute of Electric Power Industry of Japan. The effective kinetic models developed over the Ni/YSZ anode takes into account the heat transfer and species diffusion limitations in this porous anode. The models were used to simulate the methane steam reforming processes at the co- and counter-flow patterns. The results show that the flow patterns of gas and air have certain effects on cell performance. The cell at the counter-flow has a higher output voltage and output power density at the same operating conditions. At the counter-flow, however, a high hotspot temperature is observed in the anode with a non-fixed position, even when the air inlet flow rate is increased. This is disadvantageous to the cell. Both cell voltage and power density decrease with increased air flow rate.

关键词： planar solid oxide fuel cell (SOFC) direct internal reforming chemical reaction methane electrochemical

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Static balancing of planar articulated robots

Giuseppe QUAGLIA,Zhe YIN

《机械工程前沿（英文）》 2015年第10卷第4期页码 326-343 doi: 10.1007/s11465-015-0355-9

摘要：

Static balancing for a manipulator’s weight is necessary in terms of energy saving and performance improvement. This paper proposes a method to design balancing devices for articulated robots in industry, based on robotic dynamics. Full design details for the balancing system using springs are presented from two aspects: One is the optimization for the position of the balancing system; the other is the design of the spring parameters. As examples, two feasible balancing devices are proposed, based on different robotic structures: The first solution consists of linkages and springs; the other consists of pulleys, cross mechanisms and (hydro-) pneumatic springs. Then the two solutions are compared. Pneumatic, hydro-pneumatic and mechanical springs are discussed and their parameters are decided according to the requirements of torque compensation. Numerical results show that with the proper design using the methodology presented in this paper, an articulated robot can be statically balanced perfectly in all configurations. This paper therefore provides a design method of the balancing system for other similar structures.

关键词： robotics static balancing pneumatic spring mechanical spring torque compensation

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Cusp points and assembly changing motions in the PRR-PR-PRR planar parallel manipulator

《机械工程前沿（英文）》 2023年第18卷第2期 doi: 10.1007/s11465-022-0743-x

摘要： Most parallel manipulators have multiple solutions to the direct kinematic problem. The ability to perform assembly changing motions has received the attention of a few researchers. Cusp points play an important role in the kinematic behavior. This study investigates the cusp points and assembly changing motions in a two degrees of freedom planar parallel manipulator. The direct kinematic problem of the manipulator yields a quartic polynomial equation. Each root in the equation determines the assembly configuration, and four solutions are obtained for a given set of actuated joint coordinates. By regarding the discriminant of the repeated roots of the quartic equation as an implicit function of two actuated joint coordinates, the direct kinematic singularity loci in the joint space are determined by the implicit function. Cusp points are then obtained by the intersection of a quadratic curve and a cubic curve. Two assembly changing motions by encircling different cusp points are highlighted, for each pair of solutions with the same sign of the determinants of the direct Jacobian matrices.

关键词： planar parallel manipulator assembly changing motions cusp points quartic polynomial discriminant of repeated roots

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Stability analysis of slopes with planar failure using variational calculus and numerical methods

Norly BELANDRIA, Roberto ÚCAR, Francisco M. LEÓN, Ferri HASSANI

《结构与土木工程前沿（英文）》 2020年第14卷第5期页码 1262-1273 doi: 10.1007/s11709-020-0657-9

摘要： This study investigates the technique of variational calculus applied to estimate the slope stability considering the mechanism of planar failure. The critical plane failure surface should be determined because it theoretically indicates the most unfavorable plane to be considered when stabilizing a slope to rectify the instability generated by several statistically possible planes. This generates integrals that can be solved by numerical methods, such as the Newton Cotes and the finite differences methods. Additionally, a system of nonlinear equations is obtained and solved. The surface of the critical planar failure is determined by applying the condition of transversality in mobile boundaries, for which various examples are provided. The number of slices is varied in one of the examples, while the surface of the critical planar failure is determined in the others. Results are compared using analytical methods through axis rotations. All the results obtained by considering normal stress, safety factors, and critical planar failure are nearly the same; however, in this research, a study is carried out for “ ” number of slices using programming methods. Sub-routines are important because they can be applied in slopes with different geometry, surcharge, interstitial pressure, and pseudo-static load.

关键词： slopes stability planar failure variational calculus numerical methods

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Static behavior of planar intersecting CFST connection in diagrid structure

Ling LI, Xianzhong ZHAO, Ke KE

《结构与土木工程前沿（英文）》 2011年第5卷第3期页码 355-365 doi: 10.1007/s11709-011-0125-7

摘要： Intersecting connection plays an important role in the new diagrid structural system for high-rise buildings. To investigate the static behavior of the intersecting connection of concrete-filled steel tubular (CFST) columns, a typical reduced-scale planner connection specimen is tested under monotonic axial compression. The failure modes, force mechanism and bearing capacity of intersecting CFST connections are analyzed further in the follow-up numerical simulation, considering influences of intersecting angle, elliptical plate and ring plate. Test and simulation results prove that, intersecting connection can develop fully plastic deformation and provide sufficient bearing capacity. Parametric analysis indicates that bearing capacity of planar intersecting CFST connection mainly depends on intersecting angle and thickness of elliptical plate, while the ring plate affects that little. Capacity estimation method for planar intersecting CFST connection is proposed basing on the capacity of the critical section which is located near intersecting center for a distance of steel tube radius, and the design suggestions is provided in the end of this paper.

关键词： diagrid structure concrete-filled steel tube planar intersecting connection experimental research mechanism analysis

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Polyhedral linkages obtained as assemblies of planar link groups

GÖkhan KİPER, Eres SÖYLEMEZ

《机械工程前沿（英文）》 2013年第8卷第1期页码 3-9 doi: 10.1007/s11465-013-0363-6

摘要：

The study aims to devise means of obtaining polyhedral linkages for homothetic deployment of polyhedral shapes by embedding planar link groups in faces of the polyhedral shape of interest. The questions of which polyhedral shapes may be suitable for such a purpose and what are the compatibility conditions for spatially assembling planar link groups are addressed. Homohedral and tangential polyhedral shapes are found to be suitable for the task and some examples of linkages are worked out.

关键词： polyhedral linkages homothety homohedra tangential polyhedra

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Dynamic modeling of flexible-links planar parallel robots

DU Zhaocai, YU Yueqing, ZHANG Xuping, DU Zhaocai

《机械工程前沿（英文）》 2008年第3卷第2期页码 232-237 doi: 10.1007/s11465-008-0032-3

摘要： This paper presents a finite element-based method for dynamic modeling of parallel robots with flexible links and rigid moving platform. The elastic displacements of flexible links are investigated while considering the coupling effects between links due to the structural flexibility. The kinematic constraint conditions and dynamic constraint conditions for elastic displacements are presented. Considering the effects of distributed mass, lumped mass, shearing deformation, bending deformation, tensile deformation and lateral displacements, the Kineto-Elasto dynamics (KED) theory and Lagrange formula are used to derive the dynamic equations of planar flexible-links parallel robots. The dynamic behavior of the flexible-links planar parallel robot is well illustrated through numerical simulation of a planar 3-RR parallel robot. Compared with the results of finite element software SAMCEF, the numerical simulation results show good coherence of the proposed method. The flexibility of links is demonstrated to have a significant impact on the position error and orientation error of the flexible-links planar parallel robot.

关键词： 3-RR parallel KED coupling software SAMCEF orientation

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Analysis of the dynamic stress of planar flexible-links parallel robots

DU Zhaocai, YU Yueqing, YANG Jianxin

《机械工程前沿（英文）》 2007年第2卷第2期页码 152-158 doi: 10.1007/s11465-007-0025-7

摘要： This paper presents a method for the dynamic stress analysis of planar parallel robots with flexible links and a rigid moving platform. The finite element-based dynamic model of flexible parallel robots is proposed. The relation between elastic deformations and elastic displacements of the flexible links is investigated, considering the coupling effects of elastic motion and rigid motion. The elastic deformations of links are calculated. Considering the effects of bending-shearing strain and tensile-compression strain, the dynamic stress of the links and its position are derived by using the Kineto-Elastodynamics theory and the Timoshenko beam theory. Due to the flexibility of the links, the dynamic stresses are well illustrated through numerical simulation. Compared with the results of the finite element software SAMCEF, the numerical simulation results show the good coherence and advantages of the analysis method. The dynamic stress analysis is demonstrated to have a significant impact on the analysis, design and control of flexible parallel robots.

关键词： numerical simulation Due coupling software SAMCEF flexibility

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Nongray radiation from gas and soot mixtures in planar plates based on statistical narrow-band spectral

Huaqiang CHU, Qiang CHENG, Huaichun ZHOU, Fengshan LIU

《能源前沿（英文）》 2011年第5卷第2期页码 149-158 doi: 10.1007/s11708-010-0124-8

摘要： The nongray behavior of combustion products plays an important role in various areas of engineering. Based on the statistical narrow-band (SNB) spectral model with an exponential-tailed inverse intensity distribution and the ray-tracing method, a comprehensive investigation of the influence of soot on nongray radiation from mixtures containing H O/N +soot, CO /N +soot, or H O/CO /N +soot was conducted in this paper. In combustion applications, radiation transfer is significantly enhanced by soot due to its spectrally continuous emission. The effect of soot volume fraction up to 1×10 on the source term, the narrow-band radiation intensities along a line-of-sight, and the net wall heat fluxes were investigated for a wide range of temperature. The effect of soot was significant and became increasingly drastic with the increase of soot loading.

关键词： soot combustion SNB model nongray radiation

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Understanding coupled factors that affect the modelling accuracy of typical planar compliant mechanisms

Guangbo HAO,Haiyang LI,Suzen KEMALCAN,Guimin CHEN,Jingjun YU

《机械工程前沿（英文）》 2016年第11卷第2期页码 129-134 doi: 10.1007/s11465-016-0392-z

摘要：

In order to accurately model compliant mechanism utilizing plate flexures, qualitative planar stress (Young’s modulus) and planar strain (plate modulus) assumptions are not feasible. This paper investigates a quantitative equivalent modulus using nonlinear finite element analysis (FEA) to reflect coupled factors in affecting the modelling accuracy of two typical distributed-compliance mechanisms. It has been shown that all parameters have influences on the equivalent modulus with different degrees; that the presence of large load-stiffening effect makes the equivalent modulus significantly deviate from the planar assumptions in two ideal scenarios; and that a plate modulus assumption is more reasonable for a very large out-of-plane thickness if the beam length is large.

关键词： coupling factors modelling accuracy compliant mechanisms equivalent modulus

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单自由度平面闭链机构构型方法的研究

张美麟,张晔,杨治义

《中国工程科学》 2002年第4卷第6期页码 5-8

摘要：

提出了一种关于自由度平面闭链机构的构型方法，即“平面图形构造方法”。利用这种方法进行机构结构综合的主要过程是：先根据机械功能确定运动链的组成成分；再按这些成分构造平面图；最后在平面图上进行机构的构型和变异，并将其中结构最优者转换为机构简图。

关键词：机构运动链平面图

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非平面电极双稳态电润湿显示器件研究 Regular Papers-Research Articles

Han ZHANG, Xue-lei LIANG

《信息与电子工程前沿（英文）》 2019年第20卷第9期页码 1289-1295 doi: 10.1631/FITEE.1800167

摘要：双稳态电润湿显示器仅在状态切换时耗能，在状态稳定时无耗能，是一种非常有潜力的低能耗电子纸显示技术。本文设计和实现了通过常规光刻工艺制备一种非平面电极结构的双稳态电润湿器件。该器件不仅具备视频响应速度，而且有潜力实现可控的像素灰阶。与现有平面电极结构双稳态电润湿器件相比，该新型电极结构可实现更低驱动电压和更高对比度。

关键词：双稳态电润湿；非平面；控制电极；低电压；高对比度

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Effects of humic acid fractions with different polarities on photodegradation of 2,4-D in aqueous environments

YU Chunyan, QUAN Xie, OU Xiaoxia, CHEN Shuo

《环境科学与工程前沿（英文）》 2008年第2卷第3期页码 291-296 doi: 10.1007/s11783-008-0049-1

摘要： Four fractions (A, B, C, and D) of humic acids (HAs) were separated based on the polarity from weak to strong. UV-vis absorption and Fourier transform infrared spectroscopy (FTIR) analysis show that the fractions C and D possessed more aromatic C=C content. The influences of HAs and their fractions on the photolysis were investigated by the photodegradation of 2,4-D solutions under simulated solar light irradiation. The degradation rate of 2,4-D was found to decrease in the presence of bulk HAs or their fractions especially at high HAs concentration. The fractions of strong polarity C and D retarded the degradation rate more than the fractions of weak polarity A and B. This could be attributed to the different absorption intensity of the four HAs fractions in the order of D ≥ C > A > B, and the stronger ?-? electron donor-acceptor interactions between the strong polar fractions and 2,4-D.

关键词： polarity photodegradation different absorption UV-vis absorption FTIR