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Two New Glycosides from Rubus amabilis

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Chinese Chemical Letters 2000年第10期11卷 897-900页

作者： Chen, XC Jia, zj Lanzhou Univ Natl Lab Appl Organ Chem Dept Chem Lanzhou 730000 Peoples R China

A pregnane glycoside and a lignan glycoside were isolated from the aerial parts of Rubus amabilis. Their structures were elucidated as 3-O-beta-D-glucopyranosyl-3 beta.15 alpha-dihydroxypregn-5-en-20-one and (-)-secoi... 详细信息

关键词： Rubus amabilis Rosaceae pregnane lignan glycoside

A New Benzofuranosesquiterpene Dimer from Ligularia Virgaurea

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Chinese Chemical Letters 1997年第4期8卷 315-316页

作者： Wang, BG Jia, zj LANZHOU UNIV DEPT CHEMNATL LAB APPL ORGAN CHEMLANZHOU 730000PEOPLES R CHINA

A new benzofuranosesquiterpene dimer, named virgaurin B, has been isolated from the roots of Ligularia virgaurea and its structure has been elucidated by spectroscopic evidence.

关键词： Chen A New Benzofuranosesquiterpene Dimer from Ligularia Virgaurea

NEOLIGNAN GLUCOSIDES FROM PEDICULARIS TORTA

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Chinese Chemical Letters 1996年第2期7卷 145-148页

作者： Wang, CZ Jia, zj LANZHOU UNIV INST ORGAN CHEMLANZHOU 730000PEOPLES R CHINA LANZHOU UNIV STATE KEY LAB APPL ORGAN CHEMLANZHOU 730000PEOPLES R CHINA

Two new neolignan glucosides, tortosides D and E were isolated from plants of Pedicularis torta. On the basis of spectral evidence, tortosides D and E were determined as (7R.8S)-dehydrodiconiferyl-9-O-beta-D-4 ''-O-methyl-glucopyranoside and (7R,8S)-5-methoxy-dihydrodehydrodiconiferyl alcohol-9'-O-beta-D-glucopyranoside, respectively.

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NEOLIGNAN GLUCOSIDES FROM PEDICULARIS LONGIFLORA

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Chinese Chemical Letters 1996年第2期7卷 141-144页

作者： Wang, CZ Jia, zj LANZHOU UNIV INST ORGAN CHEMLANZHOU 730000PEOPLES R CHINA LANZHOU UNIV STATE KEY LAB APPL ORGAN CHEMLANZHOU 730000PEOPLES R CHINA

Two new neolignan glucosides, longiflorosides A and B were isolated from whole plants of Pedicularis lungiflora. On the basis of spectral evidence, longiflorosides A and B were determined as (7R, 8S)-4-O-methyl-dehydrodiconiferyl alcohol-9'-O-beta-D-glucopyranoside and (erythro)-1-(4-O-beta-D-glucopyranosyl-3,5-dimethoxy-phenyl)-2-:2-methoxy-4-[1-(E)-propene-3-ol]-phenoxyl}-propane-1,3-diol, respectively.

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ANALYSIS ON SMALL SCALE BRIDGING IN FIBROUS MONOLITHIC CERAMICS

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Acta Mechanica Solida Sinica 1999年第3期12卷 227-238页

作者： Wu, zj Cai, QH Tsing Hua Univ Dept Mech Engn Beijing 100084 Peoples R China

Based on shear lag model of interface between fiber and matrix, a new formula that relates the crack opening displacement and bridging force in fibrous monolithic ceramics was constructed under the framework of small scale bridging. This formula was applied to predict the fracture resistance or R-curve response of a three-point bending specimen made of fibrous monolithic ceramics. A parametric investigation on the influences of fiber volume fraction, fiber radius, characteristics of constituents, BN's fracture toughness and specimen's geometry on the bridging forces and fracture resistance in Si3N4/BN composite was carried out. The upper and lower limits of the R-curve of Si3N4/BN in small scale bridging were derived. This research revealed the role played by the above parameters in the fracture toughness of fibrous monolithic ceramics.

关键词： fibrous monolithic ceramics fiber bridging R-curve fracture toughness

The rotation and the phase transition in solid C60

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Chinese Journal of Chemistry 1996年第6期14卷 481-489页

作者： Xu, zj Yan, JM CHINESE ACAD SCI INST CHEMBEIJING 100080PEOPLES R CHINA

The interaction between C-60's in solid C-60 has been calculated by (exp-6-1) potential, and the cause and the controlled factor of the high rapid rotations of C-60's were discussed. In order to describe the disordered degree of C-60 rotation, an equivalent M is introduced. The phase transitions at the similar to 260 K and at the similar to 90 K are studied from the viewpoint of C-60 rotation. The potential barriers of the ordered rotation below the similar to 260 K and the disordered rotation above the similar to 260 K have been given, and the effect of the external pressure on the temperature of phase transition has also been given.

关键词： fullerene C-60 molecular rotation phase transition

ON THE CONVERGENCE OF THE BRENT METHOD

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Journal of Computational Mathematics 1994年第1期12卷 1-20页

作者： WANG, DR HUANG, zj SHANGHAI UNIV SCI & TECHNOL DEPT MATHSHANGHAIPEOPLES R CHINA FUDAN UNIV DEPT STAT & OPERAT RESSHANGHAIPEOPLES R CHINA

In this paper, we establish the semi-local convergence theorem of the rent method with regional estimation. By an in-depth investigation in to the algorithm structure of the method, we convert the Brent method into an approximate Newton method with a special error term. Bsaed on such equivalent variation, under a similar condition of the Newton-Kantorovich theorem of the Newton method, we establish a semi-local convergence theorem of the Brent method. This theorem provides a sufficient theoretical basis for initial choices of the Brent method.

关键词： holds Choice vergence convergent elimination otherwise Brent Dennis Cornell approximate

Phase Structure Change of Mo-Si System duringMechanical Alloying

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Journal of Materials Science & Technology 1999年第5期15卷 423-426页

作者： Liu, SJ Qu, XH Liu, zj Huang, BY Cent S Univ Technol State Key Powder Met Changsha 410083 Peoples R China

The structure of Mo-15.16 Si, Mo-30 Si and Mo-36.3 Si (wt pct) elemental powder mixture during mechanical alloying was studied using electron microscopy and X-ray diffraction. It had been found that, in all the systems under study, silicon disappeared initially during mechanical alloying (MA). In the Mo-Si systems all products were in form of amorphous state after long time milling, but there were different intermediate products. MoSi2 and Mo5Si3 intermetallic compounds in the Mo-30Si and Mo-36.3Si (wt pct) were directly synthesized from elements through inter-diffussion process. The high density of defects and interface of nano-crystal lines induced by ball milling would promote the reaction process. Only in the Mo-15.16Si (wt pct) system was Mo(Si) supersaturated solid solution formed as an intermediate product. Schematic free-energy diagram of Mo-Si system based on the thermodynamics was used to analyze the difference among the intermediate state products.

关键词： Molybdenum alloys

Ice Induced Low Temperature Fatigue Crack Propagation in Offshore Structural Steel A131

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China Ocean Engineering 1998年第3期13卷 275-284页

作者： Duan, ML Gao, zj Liu, CT China Classificat Soc Beijing 100006 Peoples R China Chinese Acad Sci Inst Mech Beijing 100080 Peoples R China

To investigate the low temperature fatigue crack propagation behavior of offshore structural steel A131 under random ice loading, three ice failure modes that are commonly present in the Bohai Gulf are simulated according to the vibration stress responses induced by real ice loading. The test data are processed by a universal software FCPUSL developed on the basis of the theory of fatigue crack propagation and statistics. The fundamental parameter controlling the fatigue crack propagation induced by random ice loading is determined to be the amplitude root mean square stress intensity factor K-arm. The test results are presented on the crack propagation diagram where the crack growth rate da/dN is described as the function of K-arm. It is evident that the ice failure modes have great influence on the fatigue crack propagation behavior of the steel in ice-induced vibration. However, some of the experimental phenomena and test results are hard to be physically explained at present. The work in this paper is an initial attempt to investigate the cause of collapse of offshore structures due to ice loading.

关键词： low temperature fatigue crack propagation offshore structure steel A131 ice load random vibration