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The Microstructure and Thermal Conductivity of Aluminum Nitride Ceramics Sintered at high Pressure with CaC_(2)

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Chinese Physics Letters 2012年第5期29卷 74-76页

作者： LI Xiao-Lei WANG Li-Ying school of Material Science and Engineering Henan Polytechnic UniversityJiaozuo 454010

Aluminum nitride (AIN) ceramics are sintered by high-pressure technology at 5 GPa/30min/1500-1800℃,using aluminum nitride powder produced by direct nitriding methods and CaC_(2) (3wt%) powder as the starting material and sintering additive,*** sample sintered at 1800℃ shows relatively high density (99.09%) and thermal conductivity (113.7 W/(m.K).XRD patterns indicate that there are no obvious impurity phases in the sintered AIN *** of the microstruct ure by SEM shows that the AlN powder grows into full crystal grains with uniform size,the crystal particles are in a regular hexagonal structure,and the grain boundary phases are clean without gas *** results suggest that AIN ceramics sintered with CaC_(2) can achieve the desired microstructure and high thermal conductivity.

关键词： ceramics powder Microstructure

Experimental study on rotary longitudinal-torsional ultrasonic machining of unidirectional CFRP

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Chinese Journal of Aeronautics 2024年第11期37卷 517-534页

作者： Ziqiang ZHANG Feng JIAO Yuanxiao LI Xue WANG Ying NIU Jinglin TONG school of Mechanical and Power Engineering Henan Polytechnic UniversityJiaozuo 454003China

Addressing the challenges of high grinding temperature,poor hole quality,and tool rod blocking in core drilling of carbon fiber reinforced plastics(CFRP),this study investigates the material removal characteristic of rotary longitudinal-torsional ultrasonic machining(RLTUM)of CFRP based on the Hertz contact *** study also conducts relevant experiments to compare and analyze the grinding force,grinding temperature,hole wall quality,exit quality,and tool wear in ordinary core drilling(OCD),rotary ultrasonic machining(RUM),and RLTUM of *** results demonstrate that RLTUM significantly reduces the grinding force,grinding temperature,hole exit damage and improves the surface smoothness of the CFRP hole *** utilizing intermittent cutting in circumferential direction for torsional vibration,RLTUM enables automatic removal of rod chips while restraining tool chip adhesion and reducing heat generation as well as tool ***,RLTUM shows great potential for enhancing the quality of holemaking in CFRP.

关键词： Carbon fiber reinforced plastics(CFRP) Rotary longitudinal-torsional ultrasonic machining Grinding force Grinding temperature Hole quality Tool wear

Synthesis of Mo_(2)C MXene with high electrochemical performance by alkali hydrothermal etching

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Journal of Advanced Ceramics 2023年第10期12卷 1889-1901页

作者： Yitong Guo Xin Zhang Sen Jin Qixun Xia Yukai Chang Libo Wang Aiguo Zhou school of Materials Science and Engineering Henan Polytechnic UniversityJiaozuo 454003China

Two-dimensional MXenes are generally prepared by the etching of acid *** as-synthesized MXenes are terminated by acid group anions(F^(–),Cl^(–),etc.),which affect the electrochemical performance of ***,we report a novel method to prepare Mo_(2)C MXene from Mo_(2)Ga_(2)C by the hydrothermal etching of alkali *** pure Mo_(2)C MXene was successfully synthesized by the etching of NaOH,while the etchings of LiOH and KOH were *** concentration of NaOH,temperature,and time strongly affect the purity of as-prepared *** Mo_(2)C MXene could be synthesized by the etching of 20 M NaOH at 180 for 24 ***℃intercalation by hexadecyl trimethyl ammonium bromide at 90 for 96 h,few℃-layer Mo_(2)C MXene was *** Mo_(2)C MXene made by NaOH etching after intercalation exhibited excellent performance as anode of lithium-ion battery,compared with general Mo_(2)C MXene made by HF etching and the Mo_(2)C MXene reported in *** final discharge specific capacity was 266.73 mAh·g^(−1)at 0.8 A·g^(−1),which is 52%higher than that Mo_(2)C made by HF etching(175.77 mAh·g^(−1)).This is because Mo_(2)C MXene made by NaOH etching has lager specific surface area,lower resistance,and pure O/OH termination without acid anion *** is the first report to make Mo_(2)C MXene by alkali etching and the samples made by this method exhibited significantly better electrochemical performance than the samples made by general HF etching.

关键词： MXene NaOH etching two-dimensional materials lithium-ion battery

Feature Selection by Merging Sequential Bidirectional Search into Relevance Vector Machine in Condition Monitoring

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Chinese Journal of Mechanical Engineering 2015年第6期28卷 1248-1253页

作者： ZHANG Kui DONG Yu BALL Andrew school of Economics & Management Wuhan Polytechnic University school of Information Engineering Communication University of China school of Computing & Engineering University of Huddersfield

For more accurate fault detection and diagnosis, there is an increasing trend to use a large number of sensors and to collect data at high frequency. This inevitably produces large-scale data and causes difficulties in fault classification. Actually, the classification methods are simply intractable when applied to high-dimensional condition monitoring data. In order to solve the problem, engineers have to resort to complicated feature extraction methods to reduce the dimensionality of data. However, the features transformed by the methods cannot be understood by the engineers due to a loss of the original engineering meaning. In this paper, other forms of dimensionality reduction technique（feature selection methods） are employed to identify machinery condition, based only on frequency spectrum data. Feature selection methods are usually divided into three main types： filter, wrapper and embedded methods. Most studies are mainly focused on the first two types, whilst the development and application of the embedded feature selection methods are very limited. This paper attempts to explore a novel embedded method. The method is formed by merging a sequential bidirectional search algorithm into scale parameters tuning within a kernel function in the relevance vector machine. To demonstrate the potential for applying the method to machinery fault diagnosis, the method is implemented to rolling bearing experimental data. The results obtained by using the method are consistent with the theoretical interpretation, proving that this algorithm has important engineering significance in revealing the correlation between the faults and relevant frequency features. The proposed method is a theoretical extension of relevance vector machine, and provides an effective solution to detect the fault-related frequency components with high efficiency.

关键词： feature selection relevance vector machine sequential bidirectional search fault diagnosis

AViscosity-Splitting Method for the Navier-Stokes/ Darcy Problem

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Advances in Applied Mathematics and Mechanics 2020年第1期12卷 251-277页

作者： Yunxia Wang Xuefeng Han Zhiyong Si school of Materials Science and Engineering Henan Polytechnic UniversityJiaozuoHenan 454003China Henan Joint International Research Laboratory for high Performance Metallic Material and Their Numerical Simulation Henan Polytechnic UniversityJiaozuoHenan 454003China school of Mathematics and Information Science Henan Polytechnic UniversityJiaozuoHenan 454003China school of Mathematics and Computational Science Xiangtan UniversityXiangtanHunan 411105China

In this report,we give a viscosity splitting method for the Navier-Stokes/Darcy *** this method,the Navier-Stokes/Darcy equation is solved in three *** the first step,an explicit/implicit formulation is used to solve the nonlinear *** introduce an artificial diffusion term qDu in our scheme whose purpose is to enlarge the time stepping and enhance numerical stability,especially for small viscosity parameter n,by choosing suitable parameter *** the second step,we solve the Stokes equation for velocity and *** the third step,we solve the Darcy equation for the piezometric head in the porous media *** use the numerical solutions at last time level to give the interface condition to decouple the Navier-Stokes equation and the Darcy’s *** stability analysis,under some condition △t≤k0,k0>0,is *** error estimates prove our method has an optimal convergence ***,some numerical results are presented to show the performance of our algorithm.

关键词： Navier-Stokes/Darcy equations fractional step method viscosity-splitting method,stability analysis optimal error analysis

high Strength, Ductility and Superplasticity Mg-6Zn-1Y-0.6Ce-0.6Zr Alloy Prepared by Rapid Solidification and Reciprocating Extrusion

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Journal of Wuhan University of Technology(Materials Science) 2017年第3期32卷 661-665页

作者：杨文朋郭学锋 REN Fang school of Materials Science and Engineering Henan Polytechnic University Jiaozuo 45000 China school of Economics and Management Henan Polytechnic University Jiaozuo 454000 China

high strength, ductility, and superplasticity Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr（wt%） alloy was prepared by sequentially applying rapid solidification, extrusion, and reciprocating extrusion（REX）. The microstructure of the alloy after 2-pass REX consisted of fine grains smaller than 0.7 μm and nanometer strengthening particles. The refined grains resulted from recrystallization during which the nanometer particles played an important role in restrain grain growth. The mechanical properties of the material were investigated at room and elevated temperatures. high tensile yield strength of 336 MPa and elongation of 27% were obtained at room temperature. At elevated temperatures, the highest elongation of 270% was obtained at 250 ℃ and an initial strain rate of 3.3×10^-3 s^-1, and LTS and HSRS were achieved. The high strength, ductility, and superplasticity were attributed to the refined unique microstructure.

关键词： magnesium alloy rapid solidification reciprocating extrusion superplasticity

Research of Copper Foam Prepared by Forming-Knitting and Infiltration

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Journal of Donghua University(English Edition) 2013年第1期30卷 68-71页

作者：薛涛张保宏孟家光 school of Textile and Material Xi'an Polytechnic University

Using forming-knitting technology and organic materials, copper foam with high porosity (>80%) and open-pore structure was successfully prepared. According to the method of immersion, the technical characteristics of metal paste performance and influence factors of sinter process were discussed. The pore morphology and compressibility of copper foam were detected simultaneously, and the structural property of copper foam prepared by the process of once-infiltrating was compared with the one of copper foam prepared by the process of twice-infiltrating. The results show that pH value of metal paste has a large influence on rheological properties of slurry. By twice-infiltrating process, the microstructure of copper foam was altered. In case of the porosity dropping indistinctly, the compression stress of copper foam platform was raised from 0.5 MPa to 1 Mpa which was of great significance to improve the energy absorption capacity of the material.

关键词： forming-knitting copper foam sintering infiltration porosity

Design of Micropipette System with high Precision for Small Enzyme Immunoassay Analyzer

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Journal of Shanghai Jiaotong university(Science) 2019年第5期24卷 605-615页

作者： SHANG Zhiwu ZHOU Xiangping LI Cheng ZHOU Xinyu school of Mechanical Engineering Tianjin Polytechnic University of China

A small auto micropipette system is developed to improve the reliability and accuracy of the automatic enzyme immunoassay analyzer’s microscale pipetting system. A sophisticated injection mechanism is designed by the means of dislocation parallel distribution of the screw and injector piston rod. It possesses the function of pipetting, taking and removing the pipette tips. In the control system, STM32 controller is used, controlling the single-axis S-type acceleration/deceleration algorithm and multi-threaded coordinated motion. The acceleration/deceleration curves are analyzed and optimized by using the method of segmentation;a minimum injection rate of 1 μL and a step rate of 0.05 μL are realized. The method of digital image processing is used to detect the amount of pipetting in micro-pipetting quantitatively. The liquid area is extracted by background contrast method, and the liquid volume in the tip is obtained by combining the geometric characteristics of the disposable tip, when the pipetting capacity is not qualified to carry out specific guidance on the pipetting system, and avoid the blocking needle, bubble and other abnormal pipetting phenomenon on the impact of pipetting accuracy. The experimental results show that the combination of the automatic sampling system and the image flow detection system can effectively improve the precision and reliability of the micro-pipetting system. Finally, the injection accuracy of the system at the test points with 10, 50 and 100 μL liquid volumes reaches 1.8%, 1.28% and 1.15%respectively.

关键词： enzyme immunoassay analyzer micropipette image processing motion control error compensation

Hypervelocity impact induced shock acoustic emission waves for quantitative damage evaluation using in situ miniaturized piezoelectric sensor network

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Chinese Journal of Aeronautics 2019年第5期32卷 1059-1070页

作者： Menglong LIU Qiang WANG Qingming ZHANG Renrong LONG Fangsen CUI Zhongqing SU Institute of high Performance Computing A*STAR (Agency for Science Technology and Research) school of Automation Nanjing University of Posts and Telecommunications State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Institute of high Performance Computing (A*STAR Agency for Science Technology and Research) Department of Mechanical Engineering The Hong Kong Polytechnic University

Manmade debris and natural meteoroids, travelling in the Low Earth Orbit at a speed of several kilometers per second, pose a severe safety concern to the spacecraft in service through the HyperVelocity Impact(HVI). To address this issue, an investigation of shock Acoustic Emission(AE) waves induced by HVI to a downscaled two-layer Whipple shielding structure is performed,to realize a quantitative damage evaluation. Firstly a hybrid numerical model integrating smoothparticle hydrodynamics and finite element is built to obtain the wave response. The projectiles, with various impact velocities and directions, are modelled to impact the shielding structure with different thicknesses. Then experimental validation is carried out with built-in miniaturized piezoelectric sensors to in situ sense the HVI-induced AE waves. A quantitative agreement is obtained between numerical and experimental results, demonstrating the correctness of the hybrid model and facilitating the explanation of obtained AE signals in experiment. Based on the understanding of HVI-induced wave components, assessment of the damage severity, i.e., whether the outer shielding layer is perforated or not, is performed using the energy ratio between the regions of ‘‘high frequency" and ‘‘low frequency" in the acquired AE signals. Lastly, the direct-arrival fundamentalsymmetric wave mode is isolated from each sensing signal to be input into an enhanced delay-andsum algorithm, which visualizes HVI spots accurately and instantaneously with different sensor network configuration. All these works demonstrate the potential of quantitative, in situ, and real time HVI monitoring using miniaturized piezoelectric sensor network.

关键词： Acoustic Emission(AE) Damage detection Hypervelocity impact Piezoelectric sensor Whipple shielding assembly