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Measurement of thermal expansion coefficient of nonuniform temperature specimen

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Chinese Optics Letters 2008年第9期6卷 669-672页

作者：戴景民辛春锁何小瓦 Department of automation Measurement and Control Harbin Institute of Technology Aerospace research inst.tute of Materials and Processing Technology

A new technique is developed to measure the longitudinal thermal expansion coefficient of C/C composite material at high temperature. The measuring principle and components of the apparatus are described in detail. The calculation method is derived from the temperature dependence of the thermal expansion coefficient. The apparatus mainly consists of a high temperature environmental chamber, a power circuit of heating, two high-speed pyrometers, and a laser scanning system. A long solid specimen is resistively heated to a steady high-temperature state by a steady electrical current. The temperature profile of the specimen surface is not uniform because of the thermal conduction and radiation. The temperature profile and the total expansion are measured with a high-speed scanning pyrometer and a laser slit scanning measuring system, respectively. The thermal expansion coefficient in a wide temperature range （1000 - 3800 K） of the specimen can therefore be obtained. The perfect consistency between the present and previous results justifies the validity of this technique.

关键词： Environmental chambers Heating Pyrometers Pyrometry Scanning Speed Temperature control Thermal spraying Thermal stress

Effect of Direct Quenching on Microstructure and Mechanical Properties of a Wear-resistant Steel

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Acta Metallurgica Sinica(English Letters) 2013年第4期26卷 390-398页

作者： Hongyu SONG Shunhu ZHANG Liangyun LAN Canming LI Haitao LIU Dewen ZHAO Guodong WANG State Key Laboratory of Rolling and automation Northeastern University Technical research and Development Center Laiwu Steel Group

A wear-resistant steel was hot rolled at the same finish temperature, and subsequently treated with conventional reheat quenching and tempering process （RQ＆T） and direct quenching and tempering process （DQ＆T）, respectively. The effect of direct quenching on the microstructure and mechanical properties was investigated in detail by using optical microscope, transmission electron microscope and scanning electron microscope equipped with electron backscattered diffraction. The results showed that the microstructures of both the RQ and DQ specimens were complex constituents of lath martensite and lower bainite. Compared with the RQ specimen, the lower bainite content in DQ specimen was much higher. Furthermore, the bainite in the DQ specimen extended into and segmented the prior austenite grains, which can decrease martensite packet size. The proportion of high-angle boundary in the DQ specimen was higher than that in the RQ specimen, which may improve the impact toughness. The carbides in DQ＆_T specimen were much finer and distributed even dispersively because direct quenching can retain substantive defects which may provide more nucleation sites for carbide precipitation in the tempering process. Besides, the mechanical properties of DQ and DQ＆T specimens were superior than those subjected to RQ and RQ＆T processes, respectively.

关键词： Direct quenching Temper Lower bainite Martensite packet Mechanical properties

Micro ball-end milling of freeform titanium parts

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Advances in Manufacturing 2015年第4期3卷 263-268页

作者： Ali Mamedov Ismail Lazoglu Mechanical Engineering Department Manufacturing and Automation Research Center Koc University Istanbul 34450 Turkey

Micro machining has growing number of applications in various industries such as biomedical, automotive, aerospace, micro-sensor, micro-actuator and jewelry industries. Small-sized freeform titanium parts are frequently needed in the biomedical applications, especially in the implantations such as mini-blood pumps and mini left-ventricular assist devices, finger joint replacements and small bone implants. Most of the small-sized titanium parts with freeform geometries are machined using micro ball-end milling before polishing and other surface treatments. Decreasing the cycle time of the machining parts is important for the productivity. In order to reduce the cycle time of the roughing process in the micro ball-end milling, this paper investigates the imple- mentation of a previously developed force-based feedrate scheduling （FFS） technique on micro milling of freeform titanium parts. After briefly introducing the inst.ntaneous micro milling forces in micro ball-end milling of titanium parts with freeform surfaces, the FFS technique is implemented in the rough machining of a freeform titanium surface to demonstrate the cycle time reduction potentials via virtual micro milling simulations.

关键词： Micro milling Roughing - Feedrate scheduling - Force model - Titanium - Ti-6Al-4V

Optimization of Temperature and Force Adaptation Algorithm in Hot Strip Mill

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维普期刊数据库

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Journal of Iron and Steel research International 2014年第3期21卷 300-305页

作者： Wen PENG Zi-ying LIU Xi-lin YANG Jian-zhao CAO Dian-hua ZHANG State Key Laboratory of Rolling and automation Northeastern University Central Iron and Steel research inst.tute

Abstract： In the hot strip rolling control system, the temperature distribution and deformation resistance are the main parameters affecting prediction of rolling force. In order to improve the model prediction precision, an optimiza- tion algorithm based on objective function was put forward, in which the penalty function index was adopted. During the adaptation process, the temperature distribution and deformation resistance were taken as the optimized parame ters, and the Nelder-Mead simplex algorithm was used to search the optimal solution of the objective function. Fur thermore, the temperature adaptation and force adaptation were solved simultaneously. Application results show that the method can improve the accuracy of the rolling force model obviously, and it can meet the demand of the indus trial production and has a good application prospect.

关键词： hot strip mill adaptation temperature distribution~ force prediction~ objective function~ simplex algo-rithm

Ground substrates classification and adaptive walking through interaction dynamics for legged robots

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Journal of Harbin inst.tute of Technology(New Series) 2012年第3期19卷 100-108页

作者：邵雪松杨一平王伟 research Center of Integrated Information System Institute of AutomationChinese Academy of Sciences

Adaptive locomotion in different types of surfaces is of critical importance for legged *** knowledge of various ground substrates,especially some geological properties,plays an essential role in ensuring the legged robots'*** this paper,the interaction between the robots and the environments is investigated through interaction dynamics with the closed-loop system model,the compliant contact model,and the friction model,which unveil the influence of environment's geological characteristics for legged robots'*** proposed method to classify substrates is based on the interaction dynamics and the sensory-motor *** foot contact forces,joint position errors,and joint motor currents,which reflect body dynamics,are measured as the sensing *** train and classify the features extracted from the raw data with a multilevel weighted k-Nearest Neighbor(kNN) *** to the interaction dynamics,the strategy of adaptive walking is developed by adjusting the touchdown angles and foot trajectories while lifting up and dropping down the *** are conducted on five different substrates with quadruped robot *** comparison with other classification methods and adaptive walking between different substrates demonstrate the effectiveness of our approach.

关键词： legged robot ground substrates classification adaptive walking interaction dynamics

Free Probability Theory Based Event Detection for Power Grids Using IoT-enabled Measurements

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Journal of Modern Power Systems and Clean Energy 2024年第5期12卷 1396-1407页

作者： Hongxia Wang Bo Wang Jiaxin Zhang Chengxi Liu Hengrui Ma Hubei Engineering and Technology research Center for AC/DC IntelligentDistribution Network School of Electrical Engineering and AutomationWuhanUniversityWuhanChina School of Electrical Engi neering and automation Wuhan UniversityWuhanChina

Taking the advantage of Internet of Things(IoT)enabled measurements,this paper formulates the event detection problem as an information-plus-noise model,and detects events in power systems based on free probability theory(FPT).Using big data collected from phasor measurement units(PMUs),we construct the event detection matrix to reflect both spatial and temporal characteristics of power gird *** event detection matrix is further described as an information matrix plus a noise matrix,and the essence of event detection is to extract event information from the event detection *** associating the event detection problem with FPT,the empirical spectral distributions(ESDs)related moments of the sample covariance matrix of the information matrix are computed,to distinguish events from“noises”,including normal fluctuations,background noises,and measurement *** on central limit theory(CLT),the alarm threshold is computed using measurements collected in normal ***,with the aid of sliding window,this paper builds an event detection architecture to reflect power grid state and detect events *** studies with simulated data from Anhui,China,and real PMU data from Guangdong,China,verify the effectiveness of the proposed *** with other data-driven methods,the proposed method is more sensitive and has better adaptability to the normal fluctuations,background noises,and measurement errors in real PMU *** addition,it does not require large number of training samples as needed in the training-testing paradigm.

关键词： Big data event detection empirical spectral distribution(ESD) free probability theory(FPT) information-plus-noise model Internet of Things(IoT) phasor measurement unit(PMU)

Artificial neural network model for identifying taxi gross emitter from remote sensing data of vehicle emission

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Journal of Environmental Sciences 2007年第4期19卷 427-431页

作者： ZENG Jun GUO Hua-fang HU Yue-ming College of automation Science and Engineering South China University of Technology Guangzhou 510640 China. automation Engineering research and Manufacture Center Guangdong Academy of Sciences Guangzhou 510070 China

Vehicle emission has been the major source of air pollution in urban areas in the past two decades. This article proposes an artificial neural network model for identifying the taxi gross emitters based on the remote sensing data. After carrying out the field test in Guangzhou and analyzing various factors from the emission data, the artificial neural network modeling was proved to be an advisable method of identifying the gross emitters. On the basis of the principal component analysis and the selection of algorithm and architecture, the Back-Propagation neural network model with 8-17-1 architecture was established as the optimal approach for this purpose. It gave a percentage of hits of 93%. Our previous research result and the result from aggression analysis were compared, and they provided respectively the percentage of hits of 81.63% and 75%. This comparison demonstrates the potentiality and validity of the proposed method in the identification of taxi gross emitters.

关键词： vehicle emission remote sensing neural network principal component analysis regression analysis

New Delay-dependent Global Asymptotic Stability Condition for Hopfield Neural Networks with Time-varying Delays

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International Journal of automation and computing 2009年第4期6卷 415-419页

作者： Guang-Deng Zong Jia Liu research inst.tute of automation Qufu Normal University Qufu 273165 PRC

This paper deals with the global asymptotic stability problem for Hopfield neural networks with time-varying delays. By resorting to the integral inequality and constructing a Lyapunov-Krasovskii functional, a novel delay-dependent condition is established to guarantee the existence and global asymptotic stability of the unique equilibrium point for a given delayed Hopfield neural network. This criterion is expressed in terms of linear matrix inequalities （LMIs）, which can be easily checked by utilizing the recently developed algorithms for solving LMIs. Examples are provided to demonstrate the effectiveness and reduced conservatism of the proposed condition.

关键词： Global asymptotic stability Hopfield neural networks linear matrix inequality (LMI) time-varying delays Lyapunov-Krasovskii functional.

P-norm Regularized SVM Classifier by Non-convex Conjugate Gradient Algorithm

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P-norm Regularized SVM Classifier by Non-convex Conjugate Gr...