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Microstructure evolution and mechanical properties of PESR 55Cr17Mo1VN plastic die steel during quenching and tempering treatment

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Journal of Iron and Steel Research International 2021年第12期28卷 1625-1633页

作者： Cong-peng Kang Fu-bin Liu huai-bei Zheng hua-bing Li Zhou-hua Jiang Kui chen hao-yang Suo Xin-hao yu School of Metallurgy Northeastern UniversityShenyang110819LiaoningChina State Key Laboratory of Metal Material for Marine Equipment and Application Anshan114002LiaoningChina

55Cr17Mo1VN high nitrogen martensitic stainless steel is usually applied to the high-quality mold,which is largely produced by the pressurized electro slag remelting *** microstructure evolution of quenching and tempering heat treatment were investigated and an optimal heat treatment process to achieve excellent mechanical properties was found *** main precipitates in the steel included carbon-rich type M_(23)C_(6) and nitrogen-rich type M_(2)*** increasing austenitizing temperature,the equivalent diameter of the precipitates got fined,and retained austenite content increased significantly when the austenitizing temperature exceeded 1020℃.The fracture mode gradually changed from brittle fracture to ductile fracture with increasing tempering temperature from 200 to 550℃.The experimental steel tempered at 350℃ achieved a good combination of hardness(60.6 HRC)and strength(2299.2 MPa)to meet service *** M_(23)C_(6) precipitated along martensite lath boundaries and the secondary hardening phenomenon occurred when the tempering temperature was 450℃.Due to the high nitrogen content,M_(2)N precipitated from the inside of laths and matrix when tempered at 550℃.

关键词： Microstructure Mechanical property Plastic die steel Quenching Tempering Precipitate

Singularity analysis for single gimbal control moment gyroscope system using space expansion method

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Chinese Journal of Aeronautics 2018年第4期31卷 782-794页

作者： yunhua WU Feng HAN bing hua Zhiming chen Feng yu School of Astronautics Nanjing University of Aeronautics and Astronautics School of Astronautics Harbin Institute of Technology

Control Moment Gyroscope（CMG） is an effective candidate for agile satellites and large spacecraft attitude control because of its powerful torque amplification capability. The most serious situation, however, in using CMG is the inherent geometric singularity problem, where there＇s no torque output along a particular direction. Space expansion method has been proposed in this work for the singularity analysis. Based on inverse mapping transformation, an expanded Jacobian matrix which is a full rank square matrix is obtained. The singular angle sets of the 3-parallel cluster and pyramid cluster are distinguished using space expansion method. An effective hybrid steering strategy, able to deal with the elliptic singularity, is further proposed. Simulation results demonstrate the excellent performance of the proposed steering logic compared to the generalized singular robust logic and pseudo inverse logic in terms of energy consumption and torque error.

关键词： Agile spacecraft Control moment gyro Singularity analysis Space expansion method Steering strategy

Effect of melt current on multi-physical field and heat flow distribution during ESR process based on model of dynamic formation of slag skin

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Journal of Iron and Steel Research International 2023年第6期30卷 1258-1267页

作者： Fu-bin Liu Xin-hao yu hua-bing Li Zhou-hua Jiang Hong-chun Zhu Xin Geng School of Metallurgy Northeastern UniversityShenyang 110819LiaoningChina

A numerical model coupled with a multi-physical field based on dynamic formation of slag skin is *** validation by comparing the experimental and simulation results of depth of metal pool,slag skin thickness and melt rate,it is utilized to investigate the effect of melt current on the coupled multi-physical field,slag skin thickness,metal pool depth and the heat flow distribution during electroslag remelting(ESR)Inconel 625 solidification *** results showed that with the increase in the melt current,the velocities of ESR system and the temperature of metal pool increased,whereas the highest temperature of slag bath firstly decreased and then *** the increase in the melt current,the slag skin thickness,metal pool depth and melt rate ***,the characteristics of the heat flow distribution and the effect of melt current on the heat flow distribution were analysed.

关键词： Electroslag remelting Melt current Slag skin Model Multi-physical field

Improvement, Comparison, and Application of Field Measurement Methods for Grassland Vegetation Fractional Coverage

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Journal of Integrative Plant Biology 2005年第9期47卷 1074-1083页

作者： Xiao-bing LI yun-hao chen hua YANG yun-Xia ZHANG College of Resources Sciences and Technology Key Laboratory of Environmental Change and Natural Disaster of the Ministry of Education Beijing Normal University Beijing 100875 China

As one of the important vegetation parameters, vegetation fractional coverage （VFC） is more difficult to measure accurately among a good many parameters of plant communities. The temperate typical steppe in the north of China was chosen for investigation in the present study and a digital camera was used to measure herb community coverage in the field, adopting methods of ocular estimation, gridding measurement, visual interpretation, supervised classification, and information extraction of color spatial transformation to calculate the VFC of images captured by the digital camera. In addition VFC calculated by various methods was analyzed and compared VFC, enabling us to propose an effective method for measuring VFC using a digital camera. The results of the present study indicate that：（i） as two common useful and effective methods of measuring VFC with a digital camera, not only does the error of estimated values of visual estimation and supervised classification vary considerably, but the degree of automatization is very low and depends, to a great extent, on the manipulator; （ii） although the method of visual interpretation may assure the precision of the calculated VFC and enable the precision of results obtained using other methods to be determined, as far as large quantities of data are concerned, this method has the disadvantages of wasting time and energy, and the applications of this method are limited; （iii） the precision and stability of VFC calculated using the grid and node method are superior to those of visual estimation and supervised classification and inferior to those of visual interpretation, but, as for visual interpretation and supervised classification, gridding measurements are difficult to apply in practice because they are not time efficient; and （iv） in terms of the precision of calculation of the VFC, an information-extracting model based on an intensity, hue, saturation （IHS） color space-multi-component series segmentation strategy is s

关键词： color space transformation digital camera field measurement grassland vegetationfractional coverage.

Coexistence of All-Order Topological States in a Three-Dimensional Phononic Topological Crystalline Insulator

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Research 2024年第2期2023卷 511-518页

作者： hua-Shan Lai hao chen Chu-hao Xia Si-yuan yu cheng He Yan-Feng chen National Laboratory of Solid State Microstructures&Department of Materials Science and Engineering Nanjing UniversityNanjng 210093China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjng 210093China Jiangsu Key Laboratory of Artificial Functional Materials Nanjing University Nanjing 210093China

Classical-wave topological materials lacking intrinsic half-integer spins are less robust while more ***,we explore a single 3-dimensional phononic topological crystalline insulator that simultaneously exhibits a whole family of first-order quadratic surface,second-order hinge,and third-order corner states within the same *** a topological crystalline insulator hosting all-order phases originates from the different topological nature when hierarchically projected onto different facets and lower dimensions,thus free from trivial cladding *** work offers an ideal platform for either robust wave propagation or localization in on-demand dimensions and may facilitate dimension division multiplexing technology.

关键词： topological dimensions crystalline

Spacecraft formation reconfiguration trajectory planning with avoidance constraints using adaptive pigeon-inspired optimization

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Science China(Information Sciences) 2019年第7期62卷 102-107页

作者： bing hua yu huaNG yunhua WU Zhiming chen Dery NICHOLAS Microsatellite Research Center College of Aeronautics Nanjing University of Aeronautics and Astronautics

Dear editor,The autonomous formation flight of satellite clusters has been identified as a beneficial technology for many future space missions [1, 2]. The research on spacecraft formation technology has become much more important for ever-increasing space applications. However, the major challenge lies in effective formation path planning to ensure collision avoidance and fuel savings.

关键词： Spacecraft formation reconfiguration trajectory planning with avoidance constraints using adaptive pigeon-inspired optimization

Telomerase Activity and Telomerase Reverse Transcriptase Expression Induced by Selenium in Rat Hepatocytes

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Biomedical and Environmental Sciences 2009年第4期22卷 311-317页

作者： RI-AN yu hua-JIE chen LING-FEI HE bing chen XUE-MIN chen Department of Occupational and Environmental Health School of Public Health Guangdong Pharmaceutical University Guangzhou 510310 Guangdong China Department of Occupational and Environmental Health MOE Key Laboratory of Environment and Health School of Public Health Tongji Medical College Huazhong University of Science and Technology Wuhan 430030 Hubei China Department of Dental Medicine The First Affiliated Hospital of Guangdong Pharmaceutical University Guangzhou 510080 Guangdong China

Objective To investigate the effects of sodium selenite on telomerase activity, apoptosis and expression of TERT, c-myc and p53 in rat hepatocytes. Methods Selenium at doses of 2.5, 5.0, and 10 μmol/kg was given to SD rats by garage. In rat hepatocytes, telomerase activity was measured by the telomeric repeat amplification protocol （TRAP）, apoptosis was detected by flow cytometry, and expressions of telomerase reverse transcriptase （TERT）, c-myc and p53 were analyzed by reverse transcription-polymerase chain reaction （RT-PCR）. c-Myc and P53 proteins were detected by immunochemistry. Results Selenium at doses of 2.5, 5.0, and 10 μmol/kg significantly increased hepatocellular telomerase activity and induced apoptosis in a dose-dependent manner. Although selenium at doses of 2.5, 5.0, and 10 μmol/kg displayed no obvious enhancing effect on the TERT mRNA expression in rat hepatocytes （P〉0.05）, it significantly increased the c-myc mRNA and p53 mRNA expression at the dose of 10 μmol/kg （P〈0.05）. Selenium at doses of 5.0 and 10 μmol/kg obviously increased the content of P53 protein in rat hepatocytes, but only at the dose of 10 μmol/kg, it significantly promoted the value of c-Myc protein in them. Conclusion Selenium can slightly increase telomerase activity and TERT expression, and significantly induce apoptosis and over-expression of c-myc and p53 at relatively high doses. The beneficial effects of selenium on senescence and aging may be mediated by telomerase activation and expression of TERT, c-myc, and p53 in rat hepatocytes.

关键词： Selenium Telomerase Telomerase reverse transcriptase c-myc p53

The Dynamics of a Prey-dependent Consumption Model Concerning Integrated Pest Management

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Acta Mathematica Sinica,English Series 2005年第3期21卷 541-554页

作者： bing LIU yu Juan ZHANG Lan Sun chen Li hua SUN Department of Mathematics Anshan Normal University Anshan 114005 P. R. China College of Mathematics and Systems Science Xinjiang University Urumqi 830046 P. R. China Deparment of Mathematics Anshan Normal University Anshan 114005 P. R. China Dalian University of Technology Dalian 116024 P. R. China Institute of Mathematics Academy of Mathematics and Systems Science Beijing 100080 P. R. China

A mathematical model for the dynamics of a prey-dependent consumption model concerning integrated pest management is proposed and analyzed. We show that there exists a globally stable pesteradication periodic solution when the impulsive period is less than some critical values. Furthermore, the conditions for the permanence of the system are given. By using bifurcation theory, we show the existence of a nontrival periodic solution if the pest-eradication periodic solution loses its stability. When the unique positive periodic solution loses its stability, numerical simulation shows there is a characteristic sequence of bifurcations, leading to a chaotic dynamics, which implies that dynamical behaviors of prey-dependent consumption concerning integrated pest management are very complex, including period-doubling cascades, chaotic bands with periodic windows, crises, symmetry-breaking bifurcations and supertransients.

关键词： IPM strategy Prey-dependent consumption model Impulsive effect Permanence Chaos

Laparoscopic hepatectomy is superior to open procedures for hepatic hemangioma

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Hepatobiliary & Pancreatic Diseases International 2021年第2期20卷 142-146页

作者： chen Yan bing-hua Li Xi-Tai Sun De-Cai yu Department of Hepatobiliary Surgery Nanjing Drum Tower HospitalThe Affiliated Hospital of Nanjing University Medical SchoolNanjing 210008China Department of General Surgery Taikang Xianlin Drum Tower HospitalThe Affiliated Hospital of Nanjing University Medical SchoolNanjing 210046China

Background:Laparoscopic hepatectomy(LH)has become increasingly popular for liver neoplasms,but its safety and effectiveness remain *** hemangiomas are the most common benign liver neoplasm;the main approaches to hepatic hemangiomas include open hepatectomy(OH)and *** this study,we compared early outcomes between patients undergoing OH and those with ***:Patients underwent OH or LH in our hospital for hepatic hemangiomas between December 2013 and December 2017 were *** patients underwent comprehensive preoperative *** clinicopathological index and risk factors of hemangioma resection were ***:In total,41 patients underwent OH while 53 underwent *** was no significant difference in any preoperative clinical variables,including liver function,prothrombin time,or platelet *** portal occlusion time and operative time were 39.74 vs.38.35 minutes(P=0.717)and 197.20 vs.203.68 minutes(P=0.652)in the OH and LH groups,*** mortality nor significant perioperative complications were observed between the two *** LH group,two cases were converted to OH,one for an oversized tumor and the other for *** with OH patients,those with LH had less blood loss(361.69 vs.437.81 m L,P=0.024),shorter postoperative hospital stay(7.98 vs.11.07 days,P=0.001),and lower postoperative C-reactive protein(43.63 vs.58.21 mg/L,P=0.026).Conclusions:LH is superior to OH in terms of postoperative recovery and blood loss for selected patients with hepatic hemangioma.

关键词： Hepatic hemangioma Open hepatectomy Laparoscopic hepatectomy Prognosis