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Science China(Technological Sciences) 2011年第9期54卷 2404-2411页

作者： CHUN qing YUE zhi PAN JianWu Key Lab of Urban & Architectural Heritage Conservation Ministry of Education Southeast University Nanjing 210096 China Civil Engineering Department Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The seismic characteristics of four typical mortise-tenon joints of Chinese southern traditional timber frame buildings were researched, including Yanwei mortise-tenon joint （including dropping Yanwei mortise-tenon joint）, Shizigutou mortise-tenon joint, Ban mortise-tenon joint and Mantou mortise-tenon joint. Experiments on thirteen specimens were carried out. Failure modes, hysteresis curves, skeleton curves and rotational stiffness were studied. The results provided a theoretical basis for seismic research, protection and maintenance of Chinese southern traditional timber flame buildings.

关键词： Chinese southern traditional timber frame building mortise-tenon joint seismic characteristics rotational stiffness

THE NATURAL CONVECTION OF AQUIFERS WITH CONSTANT HEAT SOURCES AND ITS INFLUENCE ON TEMPERATURE FIELDS

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Journal of Hydrodynamics 2012年第4期24卷 617-627页

作者： LIU Guo-qing ZHOU zhi-fang School of Earth Science and Engineering Hohai UniversityNanjing 210098China

By combining sand tank tests with numerical simulations, this paper studies the temperature fields around constant heat sources to reveal the mechanism of the natural convection and its influence on the temperature fields in the process of energy storage. Using the ＂24-channel temperature auto acquisition system＂ developed by our research group in the tests, the temperatures are recorded at measuring points within the research area in the tests, the revised Brinkman equation and a transfer-convection balance model are used for solving the aquifer water-thermal coupling problems, and through comparison of the test results with the calcula- tion results, it is discovered that the influence ranges and the variations of the two temperature fields are consistent, which validates the mathematical model. On the basis of this, we also study the influences of the heat source positions and the boundary conditions on the temperature fields, and the results show that, under the natural convection, the heat source positions may influence the distri- bution of the temperature fields, thus affect the energy storage. For the same energy storage layer, the temperature field for the top energy storage is characterized by a smaller heat influence range and a relatively concentrated temperature distribution. However, when the heat source is at the bottom, the range of a temperature field, and the temperature is relatively dispersed, which is not favorable to heat recycle, with the same heat source position, the boundary conditions determine the size of the critical Rayleigh number, and thus have an influence on the occurrence and the strength of the natural convection, and accordingly, on the temperature fields.

关键词： porous media natural convection water-thermal coupling sand tank test numerical simulation

Singularities and accumulation of singularities ofπN scattering amplitudes

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Communications in Theoretical Physics 2022年第11期74卷 136-139页

作者： Qu-zhi Li Han-qing Zheng Department of Physics Peking University Beijing 100871China College of Physics Sichuan UniversityChengduSichuan 610065China Collaborative Innovation Center of Quantum Matter BeijingChina

It is demonstrated that for the isospin I=1/2πN scattering amplitude,T^(I=1/2)(s,t),s=(m_(N)^(2)-m_(π)^(2))^(2)/m_(N)^(2)and s=m_(N)^(2)+2m_(π)^(2)are two accumulation points of poles on the second sheet of complex s plane,and are hence accumulation of singularities of T^(I=1/2)(s,t).For T^(I=3/2)(s,t),s=(m_(N)^(2)-m_(π)^(2))^(2)/m_(N)^(2)is the accumulation point of poles on the second sheet of the complex s *** proof is valid up to all orders of chiral expansions.

关键词： dispersion relations partial wave analyticity

Responses of Runoff and Soil Erosion to Vegetation Removal and Tillage on Steep Lands

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Pedosphere 2013年第4期23卷 532-541页

作者： XU qing-Xue WANG Tian-Wei cai Chong-Fa LI Zhao-Xia SHI zhi-Hua FANG Rong-Jie College of Environmental Science and Engineering Guilin University of Technology Key Lab of Subtropical Agriculture & Environment of Ministry of Agriculture Huazhong Agricultural University

Land use and land cover change is a key driver of environmental change. To investigate the runoff and erosion responses to frequent land use change on the steep lands in the Three Gorges area, China, a rainfall simulation experiment was conducted in plots randomly selected at a Sloping Land Conversion Program site with three soil surface conditions: existing vegetation cover, vegetation removal, and freshly hoed. Simulated rainfall was applied at intensities of 60 (low), 90 (medium), and 120 mm h 1 (high) in each plot. The results indicated that vegetation removal and hoeing significantly changed runoff generation. The proportion of subsurface runoff in the total runoff decreased from 30.3% to 6.2% after vegetation removal. In the hoed plots, the subsurface runoff comprised 29.1% of the total runoff under low-intensity rainfall simulation and the proportion rapidly decreased with increasing rainfall intensity. Vegetation removal and tillage also significantly increased soil erosion. The average soil erosion rates from the vegetation removal and hoed plots were 3.0 and 10.2 times larger than that in the existing vegetation cover plots, respectively. These identified that both the runoff generation mechanism and soil erosion changed as a consequence of altering land use on steep lands. Thus, conservation practices with maximum vegetation cover and minimum tillage should be used to reduce surface runoff and soil erosion on steep lands.

关键词： runoff generation sloping land subsurface runoff surface runoff vegetation cover

Preparation of Optically Active Alkoxy-serines from Amino-amide Racemate Catalyzed by Escherichia coli Cells with Peptidase B Activity

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Chemical Research in Chinese Universities 2013年第1期29卷 95-98页

作者： WANG zhi-yuan LIU Jun-zhong XU Li-sheng ZHANG Hong-juan LIU Qian JIAO qing-cai State Key Laboratory of Pharmaceutical Biotechnology School of Life Science Nanjing University Nanjing 210093 P. R. China

Alkoxy-L-serines are useful for peptide syntheses. The demand for alkoxy-L-serines in the pharmaceutical industries continues to increase because of their multiple physiological effects. In this research, an improved method for alkoxy-L-serines synthesis is reported. A series of substrates, DL-fl-alkoxy-a-amino propionamides, was used for the synthesis of alkoxy-serines catalyzed by Escherichia coli cells with peptidase B（PepB） activity. The results show that PepB has a high resolution activity with DL-fl-alkoxy-a-amino propionamides as substrate. Reaction conditions were optimized, i.e., DL-β-methoxy-a-amino propionamide as substrate at pH=9.0, 40 ℃ and 14 h, and the optimal reaction concentration is 400 mmol/L. The results also show that divalent metal cations exhibit different effects on the PepB activity, for example, Zn2＋ and Cu2＋ can obviously inhibit the activity of PepB, whereas Co2＋, Ca2＋, Mn〉 and Mg2＋ at low concentrations can activate PepB. This research provides access to enantiomerically enriched and valuable alkoxy-L-serines from a simple amino-amide racemate.

关键词： Alkoxy-serine DL-β-Alkoxy-a-amino propionamide Enzymatic resolution Peptidase B

Oxidation damage and interfacial failure of dissimilar metal welds containing ferritic heat resistant steels

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Journal of Iron and Steel Research International 2021年第11期28卷 1439-1450页

作者： Xiao-gang Li zhi-peng cai Xin Chen Shu-qing Dong Wen-he cai Yu Zhang Shan-lin Li Ke-jian Li Shao-shi Rui Ji-luan Pan Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationBeijing 100084China State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China Collaborative Innovation Center of Advanced Nuclear Energy Technology Tsinghua UniversityBeijing 100084China China Datang Corporation Science and Technological Research Institute Thermal Power Technology Research InstituteBeijing 100040China

The ex-service steam tubes containing dissimilar metal weld(DMW)between high Cr ferritic steel T91 and austenitic stainless steel TP347H and the ex-service steam tubes containing DMW between low Cr ferritic steel G102 and austenitic stainless steel TP347H were obtained from coal-fired thermal power plants in China,and their microstructures at the nickel-based weld metal(WM)/ferritic steel interfaces and oxidation characteristics were *** operating for 15,000 h at steam temperature of 541 C and steam pressure of 17.5 MPa,a G102/TP347H DMW failed along the WM/G102 steel interface,which was a dangerous premature failure mode without obvious plastic *** interfacial failure was attributed to the interaction between oxidation and cracking along the interface,where fracture appeared to be related with the strain concentration at the *** notch along the WM/G102 steel interface was the precursor of premature interfacial failure of DMW involving *** the DMW involving high Cr ferritic steel T91,ferritic steel side could form a Cr-rich passive film during service and thus would not be further oxidized after operating for 67,000 h at steam temperature of 541 C and steam pressure of 3.5 *** was concluded that oxidation played a more important role in failure of these DMWs,and retarding the development of oxidation and avoiding the interfacial oxide notch would dramatically improve the service performance of steam tubes containing DMWs.

关键词： Dissimilar metal weld Ferritic heat resistant steel Nickel-based weld metal Oxidation Interfacial failure High-temperature service

A Memory-Saving Algorithm for Spectral Method of Three-Dimensional Homogeneous Isotropic Turbulence

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Communications in Computational Physics 2011年第5期9卷 1152-1164页

作者： qing-Dong cai Shiyi Chen LTCS and CAPT Department of Mechanics and Aerospace EngineeringCollege of EngineeringPeking UniversityBeijing 100871China Department of Mechanical Engineering The Johns Hopkins UniversityBaltimoreMaryland 21218USA

Homogeneous isotropic turbulence has been playing a key role in the research of turbulence *** the pseudo-spectral method is the most popular numerical method to simulate this type of flow fields in a periodic box,where fast Fourier transform(FFT)is mostly ***,the bottle-neck in this method is the memory of computer,which motivates us to construct a memory-saving algorithm for spectral method in present ***,more times of FFT are needed as *** the most memory-saving situation,only 6 three-dimension arrays are employed in the *** cost of computation is increased by a factor of 4,and that 38 FFTs are needed per time step instead of the previous 9 FFTs.A simulation of isotropic turbulence on 20483 grid can be implemented on a 256G distributed memory clusters through this method.

关键词： Spectral method homogeneous isotropic turbulence DNS FFT

A Novel Alkaloid from Stemona parviflora

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Chinese Chemical Letters 2003年第2期14卷 173-175页

作者： Chang qing zhi Sheng HE 等 StateKeylaboratoryofDrugResearch ShanghaiInstituteofmateriaMedicaShanghaiInstitutesforBiologicalSciencesChineseAcademyofSciencesShanghai200031 StateKeylaboratoryofDrugResearc

A novel alkaloid was isolated from the stems and leaves of Stemona parviflora Wright. Based on the spectral methods, its structure was elucidated as parvineostemonine.

关键词： Stemona parviflora perhydroazaazulene parvineostemonine.

Development of a new instrument for measurement of high temperature mechanical properties of resin-bonded sand

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China Foundry 2017年第4期14卷 286-291页

作者： Peng Wan Yuan-cai Li Hong-jiang Ling Wen-qing Wang He-yi zhi Jiang Xue State Key Laboratory of Materials Processing and Die&Mould Technology Huazhong University of Science&TechnologyWuhan 430074.China Wuxi Sanfeng Instrument Equipment Co.Ltd. Wuxi 214151JiangshuChina

The mechanical properties of resin-bonded sand mixtures at high temperatures significantly affect the quality of casting. However, the existing instruments for high-temperature performances testing mainly focus on inorganic binder-bonded sands no matter the test items or the atmospheric protection, while the instrumentss specially designed for resin-bonded sand are not yet available. A new instrument for testing the hightemperature performance of resin sand was designed including the confirmation of the testing parameters, loading, measurement and control systems, and the design of the frame shape and heating furnace. This instrument can test the compressive strength, heat tolerance time and restraining load of phenol-formaldehyde resin coated sand, self-hardened furan resin sand, and trimethylamine(TEA)-based resin bonded sand at high temperatures. The developed instrument has a high accuracy offering smaller than 0.3% deviation at a full scale in the measurement of the high temperature compressive strength and the restraining load over the range of 0-6.8 MPa and 0-2,000 N, respectively. The high temperature heat tolerance time range is 0-300 s and its measurement accuracy is ±1 s.

关键词： resin-bonded sand high temperature mechanical properties high temperature compressivestrength high temperature heat tolerance time restraining load

Wake Vortex Structure Characteristics of a Flexible Oscillating Fin

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Journal of Bionic Engineering 2008年第1期5卷 49-54页

作者： zhi-dong Wang Pei Chen Xiao-qing Zhang School of Naval Architecture and Ocean Engineering Jiangsu University of Science and Technology Zhenjiang 212003 P. R.China Det Norske Veritas 1591 Hongqiao Road Shanghai 200336 P. R. China

We compute the wake of a two-dimensional and three-dimensional flexible fin in an unsteady flow field with heaving and pitching motions using FLUENT. Deflexion mode is used for a non-uniform cantilever beam with non-uniformly distributed load. The effect of chordwise deflexion length on the characteristics of propulsion is discussed for two-dimensional flexible fin. The thrust coefficient decreases, propulsive efficiency increases and the intensity of turbulence attenuates gradually as the deflexion length increases. For a three-dimensional flexible fin, the intensity of the vortex in the plane of symmetry is higher than that in the plane at 3/4 span length of the caudal fin. But the propulsive *** achieved is not what we expected with the given deflexion mode.

关键词： flexible fin deflexion length turbulence intensity structure of flow field