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Distribution of SiO and OH maser Stars in the Galactic Plane

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Chinese Journal of Astronomy and Astrophysics 2001年第2期1卷 144-151页

作者： bi－WeiJiang Shu－meiJia BeijingAstronomicalObservatory ChineseAcademyofSciencesBeijing100012 DepartmentofAstronomy BeijingNo

The observational results of the Nobeyama 45-m SiO maser survey and the Arecibo 305-m OH maser survey are assembled for an analysis of the distribution and kinematics of late-type stars in the Galactic plane. It is found that neither SiO maser stars nor OH maser stars show any concentration to the spiral arms, which imply that they do not belong to the arm population and quite possibly they are low-mass stars in late stage of evolution. A rotational curve is also derived for these objects and a few features which may be real are discussed and compared with those derived from planetary nebulae and AGB stars.

关键词： stars: late-type - maser - Galactic distribution - kinematics

Baseline distribution optimization and missing data completion in wavelet-based CS-Tomo SAR

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Science China(Information Sciences) 2018年第4期61卷 164-172页

作者： Hui bi Jianguo LIU bingchen ZHANG Wen HONG Science and Technology on microwave Imaging Laboratory Institute of ElectronicsChinese Academy of Sciences University of Chinese Academy of Sciences Department of Earth Science and Engineering Imperial College London

In this paper, we propose a coherence of measurement matrix-based baseline distribution optimization criterion, together with an L1 regularization missing data completion method for unobserved baselines(not belonging to the actual baseline distribution), to facilitate wavelet-based compressive sensingtomographic synthetic aperture radar imaging(CS-Tomo SAR) in forested areas. Using m actual baselines,we first estimate the optimal baseline distribution with N baselines(N > m), including N-m unobserved baselines, via the proposed coherence criterion. We then use the geometric relationship between the actual and unobserved baseline distributions to reconstruct the transformation matrix by solving an L1 regularization problem, and calculate the unobserved baseline data using the measurements of actual baselines and the estimated transformation matrix. Finally, we exploit the wavelet-based CS technique to reconstruct the elevation via the completed data of N baselines. Compared to results obtained using only the data of actual baselines, the recovered image based on the dataset obtained by our proposed method shows higher elevation recovery accuracy and better super-resolution ability. Experimental results based on simulated and real data validated the effectiveness of the proposed method.

关键词： tomographic synthetic aperture radar imaging(Tomo SAR) compressive sensing(CS) baseline distribution optimization coherence of measurement matrix

A micro-coupling for micro mechanical Systems

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Chinese Journal of mechanical Engineering 2016年第3期29卷 571-578页

作者： LI Wei ZHOU Zhixiong ZHANG bi XIAO Yunya College of mechanical and Vehicle Engineering Hunan University School of Engineering University of Connecticut

The error motions of micro mechanical systems, such as micro-spindles, increase with the increasing of the rotational speed, which not only decreases the rotational accuracy, but also promotes instability and limits the maximum operational speed. One effective way to deal with it is to use micro-flexible couplings between the drive and driven shafts so as to reduce error motions of the driven shaft. But the conventional couplings, such as diaphragm couplings, elastomeric couplings, bellows couplings, and grooved couplings, etc, cannot be directly used because of their large and complicated structures. This study presents a novel micro-coupling that consists of a flexible coupling and a shape memory alloy（SmA）-based clamp for micro mechanical systems. It is monolithic and can be directly machined from a shaft. The study performs design optimization and provides manufacturing considerations, including thermo-mechanical training of the SmA ring for the desired Two-Way-Shape-memory effect（TWSme）. A prototype micro-coupling and a prototype micro-spindle using the proposed coupling are fabricated and tested. The testing results show that the prototype micro-coupling can bear a torque of above 5 N · mm and an axial force of 8.5 N and be fitted with an SmA ring for clamping action at room temperature（15 ℃） and unclamping action below –5 ℃. At the same time, the prototype micro-coupling can work at a rotational speed of above 200 kr/min with the application to a high-speed precision micro-spindle. moreover, the radial runout error of the artifact, as a substitute for the micro-tool, is less than 3 μm while that of turbine shaft is above 7 μm. It can be concluded that the micro-coupling successfully accommodates misalignment errors of the prototype micro-spindle. This research proposes a micro-coupling which is featured with an SmA ring, and it is designed to clamp two shafts, and has smooth transmission, simple assembly, compact structure, zero-maintenance and balanced motio

关键词： coupling clamp shape memory alloy thermo-mechanical training micro-spindle

Land Suitability Assessment and Land Use Change in Fujian Province,China

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Pedosphere 2007年第4期17卷 493-504页

作者： QUAN bin ZHU He-Jian CHEN Song-Lin m. J. m. ROmKENS LI bi-Cheng Research Center of Soil and Water Conservation and Ecological Environment Chinese Academy of Sciences and Mi- nistry of Education Northwest Sci-Tech University of Agriculture and Forestry Yangling Shaanxi 712100 （China）. Key Laboratory of Subtropical Resources and Environment of Fujian Province Fujian Normal University Fuzhou 350007 （China） USDA/ARS National Sedimentation Laboratory P. O. Box 1157 Oxford MS 38655 （USA）

To present the current status of land quality and distribution and the trends in land use change, the physical suitability of cropland and forestland and the associated changes in Fujian Province were evaluated and analyzed using data obtained from geographical information systems (GIS) and remote sensing (RS).Of the total land area of Fujian Province,first class suitable cropland accounted for only 4.21%, whereas unsuitable cropland accounted for 84.78%. The percentage of first class suitable cropland in the southeastern region (5.32%) was much higher than that in the northwestern area (2.91%).Only 13.63% of the existing cropland area consisted of first class cropland and 70.08% was classified as unsuitable for *** the total land area of Fujian Province,the first class forestland comprised 55.25% and the unsuitable forestland (including third class) comprised 21.2%.The percentage of unsuitable forest area in the existing forestland was only 5.5%.From 1996 to 2001, cropland and unused land decreased significantly, whereas forestland and land used for urban and transport increased ***,the major tasks ahead will be the land development for full grain production potential,the better coordination of allocating land to different uses, and the regulation inappropriate activities that damage agricultural ecosystems.

关键词： Fujian Province GIS land evaluation land use change remote sensing

Improved method for analyzing the degradation of estrogens in water by solid-phase extraction coupled with ultra performance liquid chromatography-ultraviolet detection

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Journal of Environmental Sciences 2011年第4期23卷 693-698页

作者： minggang Zheng Ling Wang Yuandui bi Feng Liu College of Chemistry and Chemical Engineering and Environment Qingdao University Qingdao 266071 China The First Institute of Oceanography Qingdao 266101 China.

We established an improved method for the determination of four estrogens including estriol （E3）, 17β-estradiol （E2）, 17α-ethynyl- estrodiol （EE2） and estrone （E1） in water. The method consisted of solid-phase extraction （0.5 L water） and subsequent analysis of analytes by ultra-performance liquid chromatography （UPLC） with an ultraviolet detector （UVD）. Base-line separation was achieved for all studied estrogens using a column （50 mm × 2.1 mm） packed with 1.7 μm particle size stationary phase. Recovery was higher than 88% and detection limits ranged between 12.5–23.7 ng/L for the four estrogens, with the RSD ranging from 7% to 11%. The method was successfully applied to determine E2 and EE2 in simulated natural water, which found that about 70% of E2 was degraded （with a half-life of about 30 hr） within 48 hr and about 55% of EE2 was degraded （with a half-life of about 36 hr）. Low levels of E1 were found, however E3 was undetectable during the process.

关键词： estrogens base-lined separation half-life degradation

Synchrophasor measurement method Based on Cascaded Infinite Impulse Response and Dual Finite Impulse Response Filters

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Journal of modern Power Systems and Clean Energy 2024年第5期12卷 1345-1356页

作者： Boyu Zhao Hao Liu Tianshu bi Sudi Xu the State Key Laboratory of Alternate Electric Power System with Renewable Energy Sources North China Electric Power UniversityBeijing 102206China the State Grid Jiangsu Electric Power Research Institute Nanjing 210036China

High-precision synchronized measurement data with short measurement latency are required for the applications of phasor measurement units(PmUs).This paper proposes a synchrophasor measurement method based on cascaded infinite impulse response(IIR)and dual finite impulse response(FIR)filters,meeting the m-class and P-class requirements in the IEC/IEEE 60255-118-1 standard.A low-group-delay IIR filter is designed to remove out-of-band interference *** FIR filters with different center frequencies are designed to filter out the fundamental negative frequency component and obtain synchrophasor *** ratio of the amplitudes of the synchrophasor is used to calculate the frequency according to the one-to-one correspondence between the ratio of the amplitude frequency response of the FIR filters and the *** shorten the response time introduced by IIR filter,a step identification and processing method based on the rate of change of frequency(RoCoF)is proposed and *** synchrophasor is accurately compensated based on the frequency and the frequency response of the IIR and FIR filters,achieving high-precision synchrophasor and frequency estimates with short measurement *** and experiment tests demonstrate that the proposed method is superior to existing methods and can provide synchronized measurement data for m-class PmU applications with short measurement latency.

关键词： Synchrophasor measurement frequency estimation infinite impulse response filter complex bandpass filter

Hydrodynamics and solids mixing in fluidized beds with inclined-hole distributors

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Particuology 2019年第2期17卷 19-28页

作者： Alhussain Bakhurji Xiaotao bi John R. Grace Fluidization Research Centre Department of Chemical and Biological Engineering University of British Columbia Vancouver V6TJZ3 Canada

Experimental fluidization results were compared for three gas distributors with the same opening ratio but different orifice in clinations (30,45 , and 90 ). Hydrodynamic studies were con ducted with glass beads (diameter 154p.m) to evaluate the impacts of orifice inclination and static bed depth on pressure drop, pressure drop fluctuations, bed expansion, and minimum fluidization velocity. Solids residence time distributions were determined using phosphoresce nt tracer particles (mea n diameter 76 pm), activated by ultraviolet light. The bed pressure drop was higher with the inclined-hole distributors and increased with static bed height. In a shallow bed, the inclined-hole distributors gave less expansion;however, in deep beds, the orifice angle had negligible influence on bed expansion. The minimum fluidization velocity varied with static bed height for the inclined-hole distributors and was higher for steeper angles. The turnover time estimated using bubbling-bed equations matched the experimental results well for vertical mixing. Probes and ports at the walls of the fluidization column reduced the dense-phase downward velocity by up to 40%. The tangential particle velocity was highest for the 30 -hole distributor and decreased with increasing orifice angle. Tangential mixing was described by a dispersion model;the dispersion coefficient for the inclined-hole distributors was approximately twice that for the 90 -hole distributor in a shallow bed.

关键词： Swirling fluidized bed Fluidization Solids mixing Inclined-hole distributor

Extrinsic calibration of a laser displacement sensor in a non-contact coordinate measuring machine

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Chinese Journal of Aeronautics 2017年第4期30卷 1528-1537页

作者： Chao bi Jianguo FANG Kun LI Zhijun GUO Aviation Key Laboratory of Science and Technology on Precision manufacturing Technology Beijing Precsion EngineeringInstitute for Aircraft Industry Beijing 100076 China

In order to implement 3D scanning of those complicated parts such as blades in the aviation field,a non-contact optical measuring system is established in the paper,which integrates a laser displacement sensor,a probe head,the frame of a coordinate measuring machine（Cmm）,*** the output of the laser sensor directly obtained possesses the 1D length of the laser beam,it needs to determine the unit direction vector of the laser beam denoted as（l,m,n）by calibration so as to convert the 1D values into 3D coordinates of target ***,an extrinsic calibration method based on a standard sphere is proposed to accomplish this task in the *** the calibration procedure,the laser sensor moves along with the motion of the Cmm and gathers the required data on the spherical ***,both the output of the laser sensor and the grating readings of the Cmm are substituted into the constraint equation of the spherical surface,in which an over-determined nonlinear equation group containing unknown parameters is *** the purpose of solving the equation group,a method based on non-linear least squares optimization is put ***,the system after calibration is utilized to measure the diameter of a metallic sphere 10 times from different orientations to verify the calibration *** the experiment,the errors between the measured results and the true values are all smaller than 0.03 mm,which manifests the validity and practicality of the extrinsic calibration method presented in the paper.

关键词： Cmm 3D scanning Extrinsic calibration Laser displacement sensor Non-linear least squares

Additive manufacturing of Ceramic Structures by Laser Engineered Net Shaping

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Chinese Journal of mechanical Engineering 2015年第6期28卷 1117-1122页

作者： NIU Fangyong WU Dongjiang mA Guangyi ZHANG bi Key Laboratory for Precision and Non-traditional machining Technology of ministry of Education Dalian University of Technology Department of mechanical Engineering University of Connecticut

Ceramic is an important material with outstanding physical properties whereas impurities and porosities generated by traditional manufacturing methods limits its further industrial applications. In order to solve this problem, direct fabrication of Al2O3 ceramic structures is conducted by laser engineered net shaping system and pure ceramic powders. Grain refinement strengthening method by doping Zr O2 and dispersion strengthening method by doping Si C are proposed to suppress cracks in fabricating Al2O3 structure. Phase compositions, microstructures as well as mechanical properties of fabricated specimens are then analyzed. The results show that the proposed two methods are effective in suppressing cracks and structures of single-bead wall, arc and cylinder ring are successfully deposited. Stable phase of α-Al2O3 and t-Zr O2 are obtained in the fabricated specimens. micro-hardness higher than 1700 HV are also achieved for both Al2O3 and Al2O3/Zr O2, which are resulted from fine directional crystals generated by the melting-solidification process. Results presented indicate that additive manufacturing is a very attractive technique for the production of high-performance ceramic structures in a single step.

关键词： lasers net shaping alumina ceramics additive manufacturing