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Single Crystal Castability and Undercoolability of PWA1483 Superalloy

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Acta Metallurgica Sinica(English Letters) 2019年第11期32卷 1415-1420页

作者： De-Xin Ma Fu Wang jian-Zheng Guo wen-Liang xu Wedge Central South Research Institute Shenzhen 518045China State Key Laboratory for Powder Metallurgy Central South UniversityChangsha 410083China State Key Laboratory for Manufacturing System Engineering School of Mechanical EngineeringXi'an Jiaotong UniversityXi'an 710049China

Both of the single crystal(SX) castability and undercoolability of PWA1383 superalloy were investigated during the directional solidifi cation and isothermal cooling. In all the six SX parts of a casting cluster, no stray grains were found, revealing a defect-free SX structure. This excellent SX castability of the superalloy was attributed to its good undercoolability. The melting point(T_L) and the critical nucleation temperature( T_N) of the alloy were measured to be 1327 °C and 1306 °C, respectively. The statistic average of the critical nucleation undercooling Δ T_N = T_L-T_N of the alloy was determined to be about 21 K, exhibiting a relatively great capacity to be deeply cooled to a temperature below the melting point without the onset of solidifi cation.

关键词： Superalloys Crystal growth Phase transitions

Experiment-based identification of time delays in linear systems

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Acta Mechanica Sinica 2017年第2期33卷 429-439页

作者： Meng-Shi Jin Yi-Qiang Sun Han-wen Song jian xu School of Aerospace Engineering and Applied Mechanics Tongji University Shanghai 200092 China Shanghai Engineering Center for Microsatellites Shanghai 201210 China

This paper presents an identification approach to time delays in single-degree-of-freedom (SDOF) and multiple-degree-of-freedom (MDOF) systems. In an SDOF system, the impedance function of the delayed system is expressed by the system parameters, the feedback gain, and the time delay. The time delay can be treated as the 'frequency' of the difference between the impedance function of the delayed system and that of the corresponding uncontrolled system. Thus, it can be identified from the Fourier transform of the difference between the two impedance functions. In an MDOF system, the pseudo-impedance functions are defined. The relationships between the time delay and the pseudo-impedance functions of the delayed system and uncontrolled system are deduced. Similarly, the time delay can be identified from the Fourier transform of the difference between the two pseudo-impedance functions. The results of numerical examples and experimental tests show that the identification approach to keeps a relatively high accuracy.

关键词： Time-delay identification Impedance function Feedback controlled system

Time-delay identification for vibration systems with multiple feedback

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Acta Mechanica Sinica 2016年第6期32卷 1138-1148页

作者： Yi-Qiang Sun Meng-Shi Jin Han-wen Song jian xu School of Aerospace Engineering and Applied Mechanics Tongji University

An approach for time-delay identification is proposed in multiple-degree-of-freedom (MDOF) linear systems with multiple feedback. The applicability of the approach is discussed in detail. Based on the characteristics of frequency domain in feedback controlled system with multiple time-delays, this paper proposes a time-delay identification approach, which is based on the pseudo impedance function of reference point. Treating feedback time-delays as the 'frequencies' of the oscillation curve, the time-delays can be obtained from the 'frequencies' of the curve. Numerical simulation is conducted to validate the proposed approach. The application scope of the approach is discussed with regard to different forms of feedback.

关键词： Multiple time-delays Parameter identification Feedback Frequency response functions

Spatiotemporal Characteristics of Reference Evapotranspiration and Its Sensitivity Coefficients to Climate Factors in Huang-Huai-Hai Plain,China

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Journal of Integrative Agriculture 2013年第12期12卷 2280-2291页

作者： YANG jian-ying LIU Qin MEI xu-rong YAN Chang-rong JU Hui xu jian-wen Institute of Environment and Sustainable Development in Agriculture Chinese Academy of Agricultural Sciences State Engineering Laboratory of Efficient Water Use and Disaster Reduction for Crops Ministry of Agriculture Key Laboratory of Dryland Agriculture Ministry of Agriculture Key Laboratory of Agricultural Environment Ministry of Agriculture

Climate change will have important implications in water shore regions,such as Huang-Huai-Hai（3H） plain,where expected warmer and drier conditions might augment crop water *** analysis is important in understanding the relative importance of climatic variables to the variation in reference evapotranspiration（ET 0）.In this study,the 51-yr ET 0 during winter wheat and summer maize growing season were calculated from a data set of daily climate variables in 40 meteorological *** maps for key climate variables were estimated according to Kriging method and the spatial pattern of sensitivity coefficients for these key variables was *** addition,the slopes of the linear regression lines for sensitivity coefficients were *** showed that ET 0 during winter wheat growing season accounted for the largest proportion of annual ET 0,due to its long phenological days,while ET 0 was detected to decrease significantly with the magnitude of 0.5 mm yr-1in summer maize growing *** radiation is considered to be the most sensitive and primarily controlling variable for negative trend in ET 0 for summer maize season,and higher sensitive coefficient value of ET 0 to solar radiation and temperature were detected in east part and southwest part of 3H plain *** humidity was demonstrated as the most sensitive factor for ET 0 in winter wheat growing season and declining relativity humidity also primarily controlled a negative trend in ET 0,furthermore the sensitivity coefficient to relative humidity increased from west to *** eight sensitivity centrals were all found located in Shandong *** ET 0 along with its sensitivity maps under winter wheat-summer maize rotation system can be applied to predict the agricultural water demand and will assist water resources planning and management for this region.

关键词： ET 0 spatial distribution temporal trends sensitivity coefficient 3H plain

A comprehensive review of wind power based power system frequency regulation

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Frontiers in Energy 2023年第5期17卷 611-634页

作者： Zhang wen Liangzhong YAO Fan CHENG jian xu Beilin MAO Rusi CHEN School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072China Electric Power Research Institute State Grid Hubei Electric Power Co.LtdWuhan 430077China

Wind power(WP)is considered as one of the main renewable energy sources(RESs)for future low-carbon and high-cost-efficient power ***,its low inertia characteristic may threaten the system frequ-ency stability of the power system with a high penetration of WP ***,the capability of WP participating in the system frequency regulation has become a research *** this paper,the impact of WP on power system frequency stability is initially *** addition,various existing control strategies of WP participating in frequency regulation are reviewed from the wind turbine(WT)level to the wind farm(WF)level,and their perfor-mances are compared in terms of operating principles and practical *** pros and cons of each control strategy are also ***,the WP combing with energy storage system(ESS)for system frequency regulation is ***,the prospects,future challenges,and solutions of WP participating in power system frequency regulation are summarized.

关键词： frequency regulation strategies wind turbine generators grid-forming control model predictive control energy storage system

Interactions to plasm protein and application potentials of carbon nanotubes in blood-contacting medical devices

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Nano Research 2023年第11期16卷 12506-12515页

作者： Jie Meng xuechun Hu Tao wen Tao Wang jian Liu Haiyan xu Institute of Basic Medical Sciences Chinese Academy of Medical Sciences&Peking Union Medical CollegeBeijing 100005China

Carbon nanotubes(CNTs)have been largely investigated in various biomedical fields on the basis of their excellent physical properties and drug delivery ***,application capacities of CNTs in blood-contacting medical devices are given due attention though there have been increasingly accumulated experimental data showing promising ***,we collected and showed research evidence that strong interactions of CNTs to plasm proteins are attractive and valuable features holding great application potentials for medical devices and implants used in blood-contacting environments,while blood compatibility has been a big challenge faced by this kind of *** review introduces the strong and nonspecific plasm protein adsorptions of CNTs due to their high purity of carbon composition and nanostructures,followed by discussions on the implication of these interactions to blood coagulation and complement activation,aiming to sort out and provide insights into the application potentials of CNTs in blood-contacting medical devices and implants in the context of anti-thrombosis and blood purification.

关键词： carbon nanotubes non-specific adsorption cardiovascular blood purification composites coagulation

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中文机读目录外国个人责任者著录浅说

天津职业大学学报 2002年第6期11卷 62-64页

作者：王文富徐建华天津职业大学天津300402

该文对《中国机读目录格式》在实际应用中,特别是对外国个人责任者著录的方法进行了初步的探讨。并列举部分例释,供编目同仁参考。

关键词：中文机读目录外国个人责任者著录

Preparation of hollow ceramic microspheres absorbent based on self-reactive quenching technology

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Rare Metals 2015年第5期34卷 344-350页

作者： jian-jiang Wang Hong-Fei Lou Jin-Hua wen xu-Dong Cai Advanced Materials Institute Mechanical Engineering College

A1 ＋ BaO2 ＋ Fe2O3 ＋ sucrose and O2 as reaction system and feeding gas, respectively, are used to prepare hollow multiphase ceramic microspheres （HMCMs） absorbent based on self-reactive quenching technology. The morphologies, particle size distribution, hollow structure and phase compositions were characterized by scanning electron microscope （SEM）, X-ray diffraction （XRD） and size analysis. The results show that the quenching products possess high sphere-forming rate, and most of them are hollow structures. Owing to the self-burst, the particle size is between 40 and 70 μm. The phase compositions contain Al2O3, Fe3O4, Fe2O3, Ba2Fe14O22, BaO2 and BaFe4O7. The microwave absorbing tests show that the lowest reflectivity of HMCMs is -19 dB. The frequency bands less than -10 dB are from 13.0 to 15.8 GHz. The reasons for HMCMs possessing good microwave absorbing properties may be their magnetic and electrical properties as well as special hollow structure.

关键词： Self-reactive quenching technology Hollow multiphase ceramic microspheres Microwave absorbing properties

Robust time reversal processing for active detection of a small bottom target in a shallow water waveguide

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Journal of Zhejiang University-Science C(Computers and Electronics) 2010年第5期11卷 401-406页

作者： Xiang PAN jian-long LI wen xu Xian-yi GONG Institute of lnformation and Communication Engineering Zhejiang University Hangzhou 310027 China Zhejiang Provincial Key Laboratory of Information Network Technology Hangzhou 310027 China

With the spatial-temporal focusing of acoustic energy,time reversal processing(TRP) shows the potential application for active target detection in shallow *** turn the ‘potential’ into a reality,the TRP based on a model source(MS) instead of a physical probe source(PS) is *** uncertain ocean environments,the robustness of TRP is discussed for the narrowband and broadband signal *** channel transfer function matrix is first constructed in the acoustic perturbation *** a steering vector for time reversal transmission is obtained by singular value decomposition(SVD) of the *** verification of the robust TRP,the tank experiments of time reversal transmission focusing and its application for active target detection are *** experimental results have shown that the robust TRP can effectively detect and locate a small bottom target.

关键词： Robustness Time reversal processing Bottom target detection Uncertain environment Sonar