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On the calibration and verification of Voronoi-based discontinuous deformation analysis for modeling rock fracture

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Journal of Rock mechanics and Geotechnical Engineering 2023年第8期15卷 2025-2038页

作者： Kaiyu Zhang Feng Liu Kaiwen Xia Ying Xu Peng Dong Changyi Yu College of Water Resources Science and Engineering Taiyuan University of TechnologyTaiyuan030024China State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Civil EngineeringTianjin UniversityTianjin300072China Department of Civil and mineral Engineering University of TorontoTorontoM5S 1A4Canada CCCC Tianjin Port Engineering Institute Co.Ltd.Tianjin300222China CCCC First Harbor Engineering Company Co.Ltd.Tianjin300461China

Since its introduction,discontinuous deformation analysis(DDA)has been widely used in different areas of rock *** dividing large blocks into subblocks and introducing artificial joints,DDA can be applied to rock fracture ***,parameter calibration,a fundamental issue in discontinuum methods,has not received enough attention in *** this study,the parameter calibration of DDA for intact rock is carefully *** this end,a subblock DDA with Voronoi tessellation is presented ***,a modified contact constitutive law is introduced,in which the tensile and shear meso-strengths are modified to be independent of the bond *** improvement can prevent the unjustified preferential failure of short edges.A method for imposing confining pressure is also ***,sensitivity analysis is performed to investigate the influence of the calculated parameters and meso-parameters on the mechanical properties of modeled *** on the sensitivity analysis,a unified calibration procedure is suggested for both cases with and without confining ***,the calibration procedure is applied to two examples,including a biaxial compression *** results show that the proposed Voronoi-based DDA can simulate rock fracture with and without confining pressure very well after careful parameter calibration.

关键词： Discontinuous deformation analysis(DDA) Voronoi tessellation Parameter calibration Confining pressure Rock fracture

Superpixel-based segmentation algorithm for mature citrus

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International Journal of Agricultural and Biological Engineering 2020年第4期13卷 166-171,I0001页

作者： Qinghua Yang Yiqin Chen Yi Xun Guanjun Bao Key Laboratory of E&m Ministry of Education&Zhejiang ProvinceZhejiang University of TechnologyHangzhou 310023China

With the decrease of agricultural labors and the increase in production costs,harvesting robots have become a research hotspot in recent *** guide harvesting robots to pick mature citrus more precisely under variable illumination conditions,an image segmentation algorithm based on superpixel was *** simple linear iterative clustering(SLIC)algorithm which takes similarity of adjacent pixels into account was adopted to segment the images captured under variable illumination conditions into *** color and texture features of these superpixels were extracted and fused into feature vectors as descriptors to train backpropagation neural networks(BPNN)classifier in the next *** adjacency information of superpixels was considered by calculating the global-local binary pattern(LBP)in R component images when extracting texture *** accelerate the classification process,the mean of Cr-Cb image was utilized to find superpixels of interest which were regarded as candidates of citrus *** candidates were then classified by a pre-trained BPNN model with superpixel-level accuracy of 98.77%and pixel-level accuracy of 94.96%,while the average time to segment one image was 0.4778 ***,the results indicated that a superpixel-based segmentation algorithm toward citrus images had decent light robustness as well as high accuracy that could guide harvesting robot to pick mature citrus efficiently.

关键词： superpixel image segmentation BPNN variable illumination mature citrus

INVESTIGATION OF THE LOW-CYCLE FATIGUE AND FATIGUE CRACK GROWTH BEHAVIORS OF P91 BASE mETAL AND WELD JOINTS

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Acta metallurgica Sinica(English Letters) 2004年第4期17卷 597-600页

作者： H.C.Yang Y.Tu m.m.Yu J.Zhao Dongfang Boiler (Group) ltd Zigong 643001 ChinaDongfang Boiler (Group) Ltd Zigong 643001 ChinaDongfang Boiler (Group) Ltd Zigong 643001 ChinaDepartment of Materials Engineering Dalian University of Technology Dalian 116023 China

Low cycle fatigue tests and crack growth propagations tests on P91 pipe base metal and its weld joints were conducted at three different temperatures: room temperature, 550℃ and 575℃. The strain-life was analyzed, and the changes in fatigue life behavior and fatigue growth rates with increasing temperature were discussed. The different properties of the base metal and its weld joint have been analyzed.

关键词： P91 pipe low-cycle fatigue fatigue crack growth

A novel reconfigurable variable gain amplifier for a multi-mode multi-band receiver

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Journal of Semiconductors 2010年第7期31卷 131-136页

作者：郑家杰莫太山马成炎殷明 Institute of microelectronics Chinese Academy of Sciences Hangzhou Zhongke microelectronics Co Ltd

This paper presents a novel approach for designing a reconfigurable variable gain amplifier（VGA） for the multi-mode multi-band receiver system RF front-end *** configuration,which is comprised of gain circuits,control circuit,DC offset cancellation circuit and mode switch circuit is proposed to save die area and power consumption with the function of multi-mode and multi-band through *** VGA is realized in 0.18μm CmOS technology with 1.8 V power supply voltage providing a gain tuning range from 5 to 87 dB when the control voltage varies from 0 to 1.8 *** 3 dB bandwidth is about 80 mHz for all levels of control voltage（all gains）.Also,the DC offset cancellation circuit can effectively suppress DC offset to a value of less than 40 mV at the output regardless of the *** overall power consumption is less than 3 mA,and die area is 705×100μm^2.

关键词： variable gain amplifier multi-mode multi-band reconfigurable

Aging Precipitation Behavior and mechanical Properties of Inconel 617 Superalloy

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Acta metallurgica Sinica(English Letters) 2013年第3期26卷 307-312页

作者： Yan GUO Bohan WANG Shufang HOU materials Department Xi'an Thermal Power Research Institute Co.Ltd.

Aging precipitation behavior and mechanical properties of Inconel 617 superalloy aged at 760℃ for up to 10000 h were investigated. The results showed that the precipitates of the aged alloy are m23C6 and m6C carbides and γ phase. The carbide particles precipitated both at the grain boundaries and within grains, and the γ phase particles were situated at intragranular sites in the process of aging. The carbide particles were discontinuously dispersed at grain boundaries after aging for 3000 h, while after aged for 5000 h the carbide particles are merged. The precipitates inside grains remained stable even after aging for 10000 h. The hardness was increased for the alloy aged for 300 h up to 3000 h, which was resulted primarily from the precipitation of carbides as discrete particles both at the grain boundaries and inside grains. Small quantity γ precipitates were formed inside grains, to some extent, which contributed to an enhanced hardness. However, a decrease of the hardness was observed after aging for 5000 h. A significant drop in toughness of the alloy aged for 300 h was attributed to the reduction of the bonding interface strength when carbides precipitated at grain boundaries. Thereafter, the toughness decreased slowly with the prolonged aging time. The high temperature tensile properties of the aged alloy are rather stable even aged for 300-3000 h.

关键词： Inconel 617 Superalloy Aging Precipitate mechanical properties

A novel analog/digital reconfigurable automatic gain control with a novel DC offset cancellation circuit

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Journal of Semiconductors 2011年第2期32卷 79-84页

作者：何晓丰莫太山马成炎叶甜春 Institute of microelectronics Chinese Academy of Science Hangzhou Zhongke microelectronics Co Ltd

An analog/digital reconfigurable automatic gain control （AGC） circuit with a novel DC offset cancel- lation circuit for a direct-conversion receiver is presented. The AGC is analog/digital reconfigurable in order to be compatible with different baseband chips. What＇s more, a novel DC offset cancellation （DCOC） circuit with an HPCF （high pass cutoff frequency） less than 10 kHz is proposed. The AGC is fabricated by a 0.18μm CmOS process. Under analog control mode, the AGC achieves a 70 dB dynamic range with a 3 dB-bandwidth larger than 60 mHz. Under digital control mode, through a 5-bit digital control word, the AGC shows a 64 dB gain control range by 2 dB each step with a gain error of less than 0.3 dB. The DC offset cancellation circuits can suppress the output DC offset voltage to be less than 1.5 mV, while the offset voltage of 40 mV is introduced into the input. The overall power consumption is less than 3.5 mA, and the die area is 800 ×300μm2.

关键词： automatic gain control analog/digital reconfigurable DC offset cancellation

Anisotropic alumina ceramics with isotropic optical properties

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Journal of Advanced Ceramics 2023年第1期12卷 72-81页

作者： Akio IKESUE Yan Lin AUNG World Lab.Co. Ltd.Nagoya 456-8587Japan

Excellent mechanical and isotropic optical properties are achieved simultaneously from fully dense polycrystalline advanced alumina ceramics with a hexagonal crystal structure,which are optically anisotropic.A small amount(240 ppm)of ZrO_(2) additive is used to synthesize the transparent alumina ceramics with an average grain size of 0.7µm,and locally detected optical distortion(birefringence)is extremely minimized,less than 20 nm/*** transmittance(86%)of the alumina ceramics(thickness=0.3 mm)in ultraviolet(UV)to infrared(IR)regions is similar to that of commercial c-axis sapphire single crystals produced by Czochralski(CZ)method,while the extinction ratio in the visible wavelength area is over 25 *** glass and the c-axis sapphire single crystals,the alumina ceramics can clearly display texts and images on liquid crystal display(LCD)screens.A grain boundary phase of nano-sized Al_(2)O_(3)-ZrO_(2) composition(amorphous)is formed at the grain boundary of the advanced alumina ceramics,which enhances four-point bending strength and fracture toughness(KIC)simultaneously to 921 mPa and 6.8 mPa·m^(0.5),respectively,and hence the mechanical properties are superior to those of the sapphire single crystals.

关键词： alumina anisotropy isotropy fracture toughness(KIC) optical ceramics grain boundary phase

TENSILE STRESS RELAXATION OF TURBINE BOLT STEELS AT HIGH TEmPERATURE

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Acta metallurgica Sinica(English Letters) 2004年第4期17卷 542-547页

作者： G.Q.Jia H.W.Shen Y.m.Zhu metallurgical Department. Shanghai Turbine Company ltd. Shanghai 200240 ChinaMetallurgical Department. Shanghai Turbine Company Ltd. Shanghai 200240 ChinaMetallurgical Department. Shanghai Turbine Company Ltd. Shanghai 200240 China

Stress relaxation behavior of two turbine bolt steels was evaluated by the manual-controlled tensile stress relaxation test (TSRT) at high temperature. First, feasibility and the procedure of the manual-controlled tensile stress relaxation test (TSRT) is discussed and carried out on a general creep testing machine. And then, the experimental results from such type of test were compared to the existing data provided by certain Laboratory U.K. Overall good agreement between the results of manual-controlled TSRT method and the existing data provides confidence in the use of the proposed method in practice. Finally, the experimental results of turbine bolt steels from TSRT were compared with that of bending test. It is observed that great difference exists between the results from two different type stress relaxation tests. It is therefore suggested that the results from TSRT method be adopted in turbine bolt design in engineering.

关键词： tensile stress-relaxation test bending stress-relaxation test turbine bolt steels

mathematical modeling of induction heating of discard substitution block for billet hot extrusion process

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Baosteel Technical Research 2016年第1期10卷 28-32页

作者： ZHU Hongda LEI Zuosheng GUO Jiahong ZHOU Yueming JIN Xiaoli GAO Qi Shanghai Institute of Applied m athematics and m echanics Shanghai University State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Advanced Ferromentallurgy &School of m aterials Science and Engineering Shanghai University Research Institute Baoshan Iron & Steel Co.Ltd.

A magnetic and temperature field-coupled mathematical model is proposed to calculate the induction heating process of a discard substitution block for billet hot extrusion process. The mathematical model is validated by comparing simulation results with temperature measurements recorded during physical modeling. Based on systematical analysis of calculation results, a quantitative sawtooth induction power curve was proposed to realize the aim of achieving the best distributed temperature field in the block within the shortest induction time.

关键词： induction heating discard substitution hot extrusion mathematical modeling