检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

小半径高落差曲线钢箱梁落梁控制技术

价值工程 2025年第1期44卷 115-117页

作者：王高平中铁北京工程局集团第二工程有限公司长沙410000

顶推施工中的落梁是指在连续梁顶推到位,拆除导梁,将主梁顶起,拆除顶推时的临时滑道装置,然后将主梁均匀地降落并安放在永久支座上的过程。采用顶推法施工的桥梁,落梁控制是一个影响到全桥施工控制成败的关键环节。落梁时各支座处应当... 详细信息

顶推施工中的落梁是指在连续梁顶推到位,拆除导梁,将主梁顶起,拆除顶推时的临时滑道装置,然后将主梁均匀地降落并安放在永久支座上的过程。采用顶推法施工的桥梁,落梁控制是一个影响到全桥施工控制成败的关键环节。落梁时各支座处应当同步落梁,因为此时的梁体已是连续体系,如果主梁的竖向位移出现任何偏差,即各支座处落梁不同步,都将在梁内产生附加内力。因此,针对本项目曲线钢箱梁顶推完成后具有落梁高度大的特点,开展基于落梁不同步的控制研究,探究落梁不同步的限值,提出落梁控制指标,优化落梁施工方案。

关键词：桥梁工程顶推施工落梁不同步

维普期刊数据库博看期刊

Progress of fundamental mechanism of formic acid decomposition and electrooxidation

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2022年第7期31卷 292-309,I0008页

作者： Xin Liu Timo Jacob wang gao Key Laboratory of Automobile Materials Ministry of EducationDepartment of Materials Science and Engineering Jilin UniversityChangchun 130022JilinChina Institute of Electrochemistry Ulm UniversityD-89081 UlmGermany

Formic acid(HCOOH) is considered as a promising viable fuel-cell ingredient for low temperature proton-exchange membrane fuel cells as a consequence of their high safety and energy density. As one prototype reaction, the study of HCOOH decomposition and electrooxidation is also helpful to understand the reaction mechanism of other small molecular organics. Herein, we present a comprehensive overview of HCOOH decomposition and electrooxidation in different environment conditions and analyze the reaction mechanism from both experimental and theoretical point of view. Furthermore, we discuss the known strategies for improving the performance of HCOOH decomposition and electrooxidation catalysts. Finally, this review presents a prospect for the future study of HCOOH decomposition and electrooxidation.

关键词： Electrochemical catalysis Density functional theory Formic acid Spectroelectrochemistry Fuel cell

A Prototype of a Biomimetic Mantle Jet Propeller Inspired by Cuttlefish Actuated by SMA Wires and a Theoretical Model for Its Jet Thrust

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2014年第3期11卷 412-422页

作者： Fei gao Zhenlong wang Yukui wang Yangwei wang Jian Li State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin 150001 Heilongjiang P. R. China

The cuttlefish have higher swimming speed and more maneuverability than most of the fish mainly benefiting from their unique jet propulsion mechanism, which is realized by the contraction and expansion of their flexible mantle. However it is difficult to mimic this jet propulsion mechanism using conventional electro-mechanical structures. In this paper, the musculature of the cuttlefish mantle and how the mantle flexibly contracts and expands were analyzed first. Then the Shape Memory Alloy（SMA） wires were chosen as the actuators and the soft silica gel was chosen as the body materials to develop a biomimetic mantle jet propeller. The SMA wires were embedded within the soft silica gel formed with cuttlefish mantle shape along the annular direction to mimic the circular muscles of cuttlefish mantle. The water was squeezed out the mantle cavity to form rear jets when the biomimetic mantle was contracted by SMA wires. A mechanical model and a thermal model were established to analyze the jet thrust and the jetting frequency. Theoretical analysis shows that the jet thrust is proportional to the square of the rate of change of SMA strain. Increasing the driving voltage can improve the rate of change of SMA strain, thus can improve both the jet thrust and the jetting frequency. However the j etting frequency is mainly restricted by the cooling of SMA wires. To maximize the jetting frequency, the optimal driving parameters for different driving voltage were calculated. The propulsion performance was tested and the results show that the jet thrust can increase with the driving voltage as predicted and the maximum average jet thrust is 0.14 N when the driving voltage is 25 V. The swimming test was carried out to verify the feasibility of the novel design. It is shown that the biomimetic jet propeller can swim with higher speed as the jet thrust and jetting frequency increase and the maximum speed can reach 8.76 cm·s^-1 （0.35 BL·s^-1） at a jetting frequency of 0.83 Hz.

关键词： cuttlefish biomimetic jet thrust shape memory alloy

Preparation and Characterization of MWCNTs/E44

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 Materials Science & Technology 2006年第1期22卷 117-122页

作者： Yan gao Zhenjia wang Rui wang Ji LIANG Luke wang State Key Laboratory of Tribology Department of Mechanical Engineering Tsinghua UniversityBejing 100084China

Epoxy resin was modified by multi-walled carbon nanotubes（MWCNTs）with an in situ *** composite was observed using scanning electron microscopy （SEM）and X-ray diffraction （XRD）,and its abrasive wear resistance and tensile properties were *** results show that the function groups found on the surface of MWCNTs helped to improve the resin＇s crack resistance,and the cracks were found notably reduced in the *** the resin and MWCNTs were bonded physically ,the tensile properties and wear resistance of the composite were improved notably when an optimum amount of MWCNTs were filled in Epilote-44（E44）.When 5wt pct acidified MWCNTs were filled in E44,the elastic modulus ,breaking strength and wear resistance of the composite increase to 226.7%,303.3%and 272.55%（153.29%）,respectively.

关键词： Epoxy resin Multi-walled carbon nanotubes(MWCNTs) Tensile properties Wear resistance

Collision Attack on the Full Extended MD4 and Pseudo-Preimage Attack on RIPEMD

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2013年第1期28卷 129-143页

作者： gao-Li wang School of Computer Science and Technology Donghua University Shanghai 201620 China State Key Laboratory of Information Security Institute of Information Engineering Chinese Academy of Sciences Beijing 100093 China

The cryptographic hash functions Extended MD4 and RIPEMD are double-branch hash functions, which consist of two parallel branches. Extended MD4 was proposed by Rivest in 1990, and RIPEMD was devised in the framework of the RIPE project （RACE Integrity Primitives Evaluation, 1988-1992）. On the basis of differential analysis and meet-in-the- middle attack principle, this paper proposes a collision attack on the full Extended MD4 and a pseudo-preimage attack on the full RIPEMD respectively. The collision attack on Extended MD4 holds with a complexity of 237, and a collision instance is presented. The pseudo-preimage attack on RIPEMD holds with a complexity of 21254, which optimizes the complexity order for brute-force attack. The results in this study will also be beneficial to the analysis of other double-branch hash functions such as RIPEMD-160.

关键词： collision attack preimage attack hash function Extended MD4 RIPEMD

Critical-Current Degeneration Dependence on Axial Strain of Bi-based Superconducting Multi-filamentary Composite Tapes

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2014年第4期31卷 155-158页

作者： gao Pei-Feng wang Xing-Zhe Key Laboratory of Mechanics on Western Disaster and Environment (Ministry of Education) and College of Civil Engineering and Mechanics Lanzhou University Lanzhou 730000

Superconducting materials are always severely restricted in practical engineering applications due to their carrying- current degradation under mechanical loads. Based on Ekin＇s exponential model and Weibull＇s distribution func- tion, we propose an empirical degradation model for describing the mechanical deformation influence on the critical-current of Bi-based superconducting multi-filamentary composite tapes under axial loading. The critical currents of superconducting tapes depending on the axial strain are investigated analytically. It is shown that the predictions by the developed degradation model agree with the experimental data, in the processes of axial mechanical loading and unloading on the samples. The effect of the critical tension and compression damage strains on the normalized critical currents is also discussed.

关键词： CRITICAL currents MULTIFILAMENTARY superconductors WEIBULL distribution SUPERCONDUCTING tape COMPRESSION loads

A linear complementarity model for multibody systems with frictional unilateral and bilateral constraints

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

Acta Mechanica Sinica 2011年第4期27卷 587-592页

作者： Hai-Ping gao Qi wang Shi-Min wang Li Fu Department of dynamics and control Beihang University 100191 Beijing China

The Lagrange-I equations and measure differential equations for multibody systems with unilateral and bilateral constraints are constructed. For bilateral constraints, frictional forces and their impulses contain the products of the filled-in relay function induced by Coulomb friction and the absolute values of normal constraint reactions. With the time-stepping impulse-velocity scheme, the measure differential equations are discretized. The equations of horizontal linear complementarity problems （HLCPs）, which are used to compute the impulses, are constructed by decomposing the absolute function and the filled-in relay function. These HLCP equations degenerate into equations of LCPs for frictional unilateral constraints, or HLCPs for frictional bilateral constraints. Finally, a numerical simulation for multibody systems with both unilateral and bilateral constraints is presented.

关键词： Coulomb friction Bilateral constraint Unilat-eral constraint - Horizontal linear complementarity problem(HLCP) Time-stepping impulse-velocity algorithm

Global impact of RNA splicing on transcriptome remodeling in the heart

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2012年第8期13卷 603-608页

作者： Chen gao Yibin wang Molecular Biology Institute University of California Los Angeles California 90095 USA

In the eukaryotic transcriptome, both the numbers of genes and different RNA species produced by each gene contribute to the overall complexity. These RNA species are generated by the utilization of different transcriptional initiation or termination sites, or more commonly, from different messenger RNA (mRNA) splicing events. Among the 30 000+ genes in human genome, it is estimated that more than 95% of them can generate more than one gene product via alternative RNA splicing. The protein products generated from different RNA splicing variants can have different intracellular localization, activity, or tissue-distribution. Therefore, alternative RNA splicing is an important molecular process that contributes to the overall complexity of the genome and the functional specificity and diversity among different cell types. In this review, we will discuss current efforts to unravel the full complexity of the cardiac transcriptome using a deep-sequencing approach, and highlight the potential of this technology to uncover the global impact of RNA splicing on the transcriptome during development and diseases of the heart.

关键词： Alternative RNA splicing Transcriptome,Gene regulation Heart RNA-seq

Moderate deviations and central limittheorem for small perturbationWishart processes

在线全文

学校读者我要写书评

暂无评论

Frontiers of Mathematics in China 2014年第1期9卷 1-15页

作者： Lei CHEN Fuqing gao Shaochen wang School of Mathematics and Statistics Wulhan University Wuhan 430072 China

Let X^ε be a small perturbation Wishart process with values in the set of positive definite matrices of size m, i.e., the process X^ε is the solution of stochastic differential equation with non-Lipschitz diffusion coefficient： dXt^ε = √εXt^εtdBt＇＋ dBt＇√εXt^ε ＋ ρImdt, X0 = x, where B is an rn x m matrix valued Brownian motion and B＇ denotes the transpose of the matrix B. In this paper, we prove that { （Xt^ε-Xt^0）/√εh^2（ε）,ε 〉 0} satisfies a large deviation principle, and （Xt^ε - Xt^0）/√ε converges to a Gaussian process, where h（ε） → ＋∞ and √ε h（ε） →0 as ε →0. A moderate deviation principle and a functional central limit theorem for the eigenvalue process of X^ε are also obtained by the delta method.

关键词： Large deviation moderate deviation central limit theorem Wishart vprocess eigenvalue