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Transition of electrical conductivity in carbon nanotube/silver particle composite buckypapers

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Particuology 2014年第6期12卷 15-21页

作者： fenghua Su Menghe Miao School of Mechanical and Automotive Engineering South China University of Technology CSIRO Materials Science and Engineering P.O.Box 21BelmontVictoria 3216Australia

The electrical conductivity of carbon nanotube buckypapers can be dramatically increased by incorporation of silver particles contained in a commercial silver *** methods,co-dispersion during the production of buckypaper and surface coating on a preformed buckypaper,were used to prepare composite *** two types of composite buckypapers exhibited very different electrical conductivity *** composite buckypapers prepared by the surface coating method showed a distinct step transition in electrical conductivity at 3 vol%silver content,leading to a 15-fold improvement at 6%silver *** composite buckypapers prepared by the co-dispersion method showed a gradual change in electrical conductivity with increasing silver particle content,resulting in a five-fold improvement at12%silver *** and sectional morphologies of the two types of composite buckypapers were examined and related to their electrical conductivity profiles.

关键词： Carbon nanotubes Buckypaper Electrical conductivity

Characterization of arsenate adsorption on amorphous Al gels with Keggin structure by Fourier transformed infrared spectroscopy and MAS ^(27)Al NMR

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Chinese Journal Of Geochemistry 2009年第1期28卷 61-69页

作者： ZHAO fenghua Department of Resource and Earth Science China University of Mining and Technology Beijing 100083 China

Fourier transformed infrared spectrometry (FTIR) and 27Al Magic Angle spinning (MAS) nuclear magnetic resonance spectroscopy were employed to characterize arsenate adsorption on amorphous Al gels with Keggin structure at pH =4–10. These studies have proven that: the surface complex species of arsenate show significant differences under acidic and alkaline conditions, which was deduced based on the As-O stretching vibration bands located respectively at 774 and 870 cm-1; poorly crystalline Al13 (or Al)-arsenate precipitation could be easily formed under acid medium condition and high loading level, which was supported by comparing the As-O vibration (at ≈732 cm-1) of precipitation to adsorbed Al gels; arsenate (AsO43-) adsorption has no effect on the Keggin structure of Al gels with basicity (R) =2.6 and 3.0, even at high loading level, as evidenced by the signal at ≈63×10-6 of magic angle spinning (MAS)-27Al NMR. The adsorption envelope was determined by conventional batch experiments.

关键词： RTIR 稳定性地球化学元素

Multi-Robot Cooperative Localization:Time-Varying Unobservable Subspace Analysis and Consistent Algorithm Design

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Journal of Systems Science & Complexity 2024年第5期37卷 1937-1955页

作者： HAO Ning HE fenghua YAO Yu School of Astronautics Harbin Institute of TechnologyHarbin 150000China

This paper investigates the problem of cooperative localization(CL)for a multi-robot system(MRS)under dynamic measurement topology,which involves a group of robots collectively estimating their poses with respect to a common reference frame using ego-motion measurements and robot-to-robot relative *** authors provide a theoretical analysis of the time-varying unobservable subspace and propose a consistent cooperative localization ***,the authors introduce the relative measurement graph(RMG)to represent the relative pose measurements obtained by the MRS at each ***,the authors derive the local observability matrix over a time *** equivalent relationship is established between the local observability matrix and the spectral matrices of the ***,the authors present a method for constructing the unobservable subspace based on the RMG under different topology *** on this analysis,the authors design a consistent cooperative localization algorithm that satisfies the constraints of the time-varying unobservable *** analytical optimal solution is derived for the constrained optimization *** Carlo numerical simulations are conducted to demonstrate the consistency and accuracy of the proposed method.

关键词： Consistency cooperative localization multi-robot system null space relative measurement graph time-varying unobservable subspace

Lubricating performances of graphene oxide and onion-like carbon as water-based lubricant additives for smooth and sand-blasted steel discs

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Friction 2020年第1期8卷 47-57页

作者： fenghua SU Guofu CHEN Ping HUANG School of Mechanical and Automotive Engineering South China University of TechnologyGuangzhou 510641China

Graphene oxide(GO)nanosheets and onion‐like carbon(OLC)nanoparticles were synthesized from natural graphite powder and candle soot,respectively,and characterized by transmission electron microscopy and Raman *** lubricating performances of GO and OLC as lubricant additives in water were comparatively evaluated using a ball‐on‐disc *** effects of sand blasting of a steel disc on its morphology and tribological property were *** results show that the two nanomaterials,GO and OLC,when used as lubricant additives in water effectively reduce the friction and wear of the sliding discs,which is independent of the disc surface *** applying heavy loads,it is observed that GO exhibits superior friction‐reducing and anti‐wear abilities compared to those of OLC—a trace amount of GO can achieve a lubricating ability equivalent to that of an abundant amount of ***,it is observed that sand blasting cannot improve the wear resistance of the treated steel disc,even though the hardness of the disc increased after the *** possible anti‐wear and friction‐reducing mechanisms of the GO and OLC as lubricant additives in water are discussed based on results for the wear surfaces obtained by scanning electron microscopy,Raman spectroscopy,and X‐ray photoelectron spectroscopy。

关键词： graphene oxide onion‐like carbon lubricant additive friction and wear

Shape Memory Epoxy Resin and Its Composites:From Materials to Applications

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Research 2022年第2期2022卷 345-369页

作者： Lan Luo fenghua Zhang Jinsong Leng Centre for Composite Materials and Structures Harbin Institute of Technology(HIT)Harbin 150080China

Shape memory polymers(SMPs)have historically attracted attention for their unique stimulation-responsive and variable stifness and have made notable progress in acrospace,civil industry,and other *** particular,epoxy resin(EP)has great potential due to its excellent mechanical properties,fatigue resistance,and radiation ***,we focus on the molecular design and network construction of shape memory epoxy resins(SMEPs)to provide opportunities for performance and functional *** and high-performance SMEPs are introduced in detail,including multiple SMEPs,two-way SMEPs,outstanding toughness,and termperature ***,emerging applications of SMEP's and their composites in aerospace,four-dimensional printing,and self-healing are *** on this,we point out the challenges ahead and how SMEPs can integrate performance and versatility to meet the needs of technological development.

关键词： composites printing resins

Regional Difference in Social Capital and Its Impact on Regional Economic Growth in China

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Chinese Geographical Science 2010年第5期20卷 442-449页

作者： Pan fenghua HE Canfei Department of Urban and Economic Geography College of Urban and Environmental Science Peking University Beijing 100871 China

Social capital has played an increasingly important role in regional *** is a country with high stocks of social *** several different indicators of social capital,this study tries to research the regional disparities in social capital and the influence of social capital on economic growth of China in *** social capital with indicators of associations,charities and blood donation rates,this study finds significant regional disparities in social capital at provincial level in *** indicators for social capital are highly correlated with regional economic *** analysis shows that social capital has a significant and positive effect on a long-term provincial economic *** relationship exists after controlling policy,macro location factors,and per capita GDP in the initial *** empirical findings indicate that institutions,culture and social relations are critical for regional development in ***,the creation and support of social capital should be paid more attention to when making regional policy.

关键词： social capital trust economic growth transaction cost

Control Design for Harmonic Disturbance Rejection for Robot Manipulators with Bounded Inputs

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Chinese Journal of Mechanical Engineering 2011年第2期24卷 248-256页

作者： YAO Yu WANG Xiaochen HE fenghua Control and Simulation Center Harbin Institute of Technology Harbin 150080 China

Currently most of control methods are of one degree of freedom（1-DOF） control structure for the robot systems which are affected by unmeasurable harmonic disturbances,at the same time in order to obtain perfect disturbance attenuation level,the controller gain must be *** practice,however,for robotic actuators,there are physical constraints that limit the amplitude of the available *** paper considers the problem of tracking control under input constraints for robot manipulators which are affected by unmeasurable harmonic disturbances.A new control scheme is proposed for the problem,which is composed of a parameter-dependent nonlinear observer and a tracking *** parameter-dependent nonlinear observer,designed based on the internal model principle,can achieve an estimation and compensation of a class of harmonic disturbances with unknown *** tracking controller,designed via adaptive control techniques,can make the systems asymptotically track the desired *** the control design,the continuous piecewise differentiable increasing function is used to limit control input amplitude,such that the control input saturation is *** Lyapunov stability of closed loop systems is *** validate proposed control scheme,simulation results are provided for a two link horizontal robot *** simulation results show that the proposed control scheme ensures asymptotic tracking in presence of an uncertain external disturbance acting on the *** important feature of the methodology consists of the fact that the designed controller is of 2-DOF control structure,namely,it has the ability to overcome the conflict between controller gain and robustness against external disturbances in the traditional 1 -DOF control structure framework.

关键词： tracking control of robot harmonic disturbance rejection internal model principle input constraint adaptive control

Blind reconstruction of convolutional code based on segmented Walsh-Hadamard transform

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Journal of Systems Engineering and Electronics 2014年第5期25卷 748-754页

作者： fenghua Wang Hui Xie Zhitao Huang College of Electronic Science and Engineering National University of Defense Technology Department of Electronic and Optics Engineering Ordance Engineering College

Walsh-Hadamard transform （WriT） can solve linear error equations on Field F2, and the method can be used to recover the parameters of convolutional code. However, solving the equations with many unknowns needs enormous computer memory which limits the application of WriT. In order to solve this problem, a method based on segmented WriT is proposed in this paper. The coefficient vector of high dimension is reshaped and two vectors of lower dimension are obtained. Then the WriT is operated and the requirement for computer memory is much reduced. The code rate and the constraint length of convolutional code are detected from the Walsh spectrum. And the check vector is recovered from the peak position. The validity of the method is verified by the simulation result, and the performance is proved to be optimal.

关键词： convolutional code blind reconstruction Walsh-Hadamard transform (WriT) tinear error equation.

Blind reconstruction of linear scrambler

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Journal of Systems Engineering and Electronics 2014年第4期25卷 560-565页

作者： Hui Xie fenghua Wang Zhitao Huang Department of Electronic and Optics Engineering Ordance Engineering College College of Electronic Science and Engineering National University of Defense Technology

An algorithm based on eigenanalysis technique and Walsh-Hadamard transform （WriT） is proposed. The algorithm contains two steps. Firstly, the received sequence is divided into temporal windows, and a covariance matrix is computed. The linear feedback shift register （LFSR） sequence is reconstructed from the first eigenvector of this matrix. Secondly, equations according to the recovered LFSR sequence are constructed, and the Walsh spectrum corresponding to the equations is computed. The feedback polynomial of LFSR is estimated from the Walsh spectrum. The validity of the algorithm is verified by the simulation result. Finally, case studies are presented to illustrate the performance of the blind reconstruction method.

关键词： scrambler linear feedback shift register (LFSR) reconstruction eigenanalysis Walsh-Hadamard transform.