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Acta Mathematicae Applicatae Sinica 2011年第3期27卷 481-494页

作者： ji-ming Yang Yanping Chen College of Science Hunan Institute of Engineering Xiangtan 411104 China School of Mathematical Sciences South China Normal University Guangzhou 510631 China

A combined mixed finite element and discontinuous Galerkin method for a compressible miscible displacement problem which includes molecular diffusion and dispersion in porous media is investigated. That is to say, the mixed finite element method with Raviart-Thomas space is applied to the flow equation, and the transport one is solved by the symmetric interior penalty discontinuous Galerkin （SIPG） approximation. Based on projection interpolations and induction hypotheses, a superconvergence estimate is obtained. During the analysis, an extension of the Darcy velocity along the Gauss line is also used in the evaluation of the coefficients in the Galerkin procedure for the concentration.

关键词： superconvergence mixed finite element discontinuous Galerkin compressible

Comparison of paleoclimatic characteristics between monsoon and westerly areas,China

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Chinese Science Bulletin 2001年第S1期46卷 119-124页

作者： Wei Ye fang ji Zhejiang Normal Univ Coll Life & Environm Sci Jinhua 321004 Peoples R China

For past decades there have been many studies on the climate features during the last interglacial and glacial periods. A comparison between the loess record of western China with that of monsoon areas shows some regional differences. ( i) Generally, the climate of the Yili region since the late Pleistocene was dry, with fluctuations. Late Pleistocene climate change in the study area can be divided into 5 stages, corresponding to 5 marine isotopic stages (MIS 1-MISS), (ii) Evidence from grain size composition, magnetic susceptibility, carbonate content, pollen assemblage and geochemistry shows that the climate during the last glacial period was instable. During MIS4 the westerly winds were strong and the humidity was relatively high. Compared with the early stage, MIS2 was dry. In MIS3, westerly winds were relatively weak; pedogenesis prevailed, forming paleo-sols. (iii) In contrast to the Loess Plateau the deposition rate of dust at the early stage was higher than at the late stage of the last galical

关键词： paleoclimatic characteristics monsoon area western China.

Using Tip Gaps on Tandem Diffuser to Broaden the Operation Range of a Centrifugal Compressor

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Journal of Thermal Science 2021年第3期30卷 999-1009页

作者： fang Junyi ji Chunjun LI Chunyang SUN Qi School of Power Engineering Dalian University of TechnologyDalian 116024China Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China

Gaps in compressors are generally unfavorable because they lead to energy ***,gaps on diffuser blades can broaden the operation range of a *** broaden the operation range of a centrifugal compressor with a tandem diffuser,gaps with different sections and widths on the diffuser blades were examined to determine their influence on the compressor *** results show that the compressor’s surge margin increased from 33.28% to 49.2% for a 2.5%tip gap ratio,while its stability margin increased from 44% to 60.5%.However,pressure ratio and efficiency losses of 1.16% and 1.14%,respectively,were *** widths less than 5%of the height of the diffuser blade are adequate for broadening the operation range,whereas gap ratios greater than 5%cause more energy loss without broadening the operation range *** can also reduce the Mach number in the diffuser blade channels and can be influenced by the impeller-tip ***,diffuser gaps on the shroud side yield better performance than those on the hub *** experiment was conducted to investigate the reliability of the calculation and conclusions in this study,and the results proved that the conclusions are valid for different types of centrifugal compressors.

关键词： centrifugal compressor tandem diffuser tip gap flow operation range surge choke

The Assessment of Ocean Wave Energy Along the Coasts of Taiwan

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China Ocean Engineering 2012年第3期26卷 413-430页

作者： LIN Yu-Hsien fang ming-Chung Fishing Boat & Mar.Eng.Research Center National Cheng-Kung University Dept.of Systems & Naval Mechatronic Eng. National Cheng-Kung University

The wave energy resource around the coasts of Taiwan is investigated with wave buoy data covering a 3-year period （2007-2009）. Eleven study sites within the region bounded by the 21.5^°N-25.5°N latitudes and 118°E-122°E longitudes are selected for analysis. The monthly moving-average filter is used to obtain the low-frequency trend based on the available hourly data. After quantifying the wave power and annual wave energy, the substantial resource is the result of Penghu buoy station, which is at the northeastern side of Penghu Island in the Taiwan Strait. it is investigated that the Penghu sea area is determined to be the optimal place for wave energy production according to its abundant resource of northeasterly monsoon waves, sheltering of the Taiwan Island, operation and maintenance in terms of seasonal conditions, and constructability of wave power devices.

关键词： ocean wave energy wave energy converter wave climate Taiwan Strait monsoon waves

Efficiency of Profinite Rigidity of Triangle Groups

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Acta Mathematica Sinica,English Series 2022年第10期38卷 1939-1948页

作者： ji ming MA Zi Xi WANG School of Mathematical Sciences Fudan UniversityShanghai 200433P.R.China

It is already known that finitely-generated Fuchsian groups are profinitely rigid among all lattices of connected Lie groups by the result of Bridson,Conder and *** the triangle groups are distinguished among themselves by their finite *** focus on the question about quantifying the size of a quotient which separates two triangle groups and give an explicit upper bound.

关键词： Triangle groups profinite completion finite quotients

A Convenient ＂Turn On-off＂ Phosphorescent Nanosensor for Detection of Biotin Based on Quantum Dots/CTAB

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Chemical Research in Chinese Universities 2016年第6期32卷 917-923页

作者： fang Xiaoxing ZHENG ji YAN Guiqin School of Life Science Shanxi Normal University Linfen 041000 P. R. China

A switchable room-temperature phosphorescence（RTP） nanosensor based on an MPA-capped Mn-dopedZnS QDs/CTAB composite system（MPA=3-mercaptopropionic acid; CTAB=cetyltrimethyl ammonium bromide;QDs=quantum dots） was established for the detection of biotin. The phosphorescence intensity of QDs/CTAB couldbe regularly quenched with the increase of biotin. Under optimal conditions, this method yielded two linear ranges of2-20 μg/L and 20-140 μg/L with respective correlation coefficients of 0.993 and 0.990, as well as a detection limitof 0.93 μg/L. Therefore, the analytical potential of the proposed nanosensor was evaluated by detecting biotin inurine and biotin tablets. This approach yielded satisfactory results because of the effective elimination of backgroundfluorescence and light scattering from the sample matrix. This approach provides a practical method for biotin detec-tion.

关键词： Biotin Nanosensor Quantum dot Room-temperature phosphorescence

INFLUENCE OF MOLECULAR STRUCTURES OF SECONDARY AMINE TERMINATED POLY(ESTER-AMINE)S ON THE CURING PERFORMANCE WITH EPOXY RESIN

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Chinese Journal of Polymer Science 2007年第6期25卷 545-553页

作者： Li-ming Tang ji Feng Yu Wang Advanced Materials Laboratory Department of Chemical Engineering Tsinghua University Beijing 100084 China

Five secondary amine terminated poly（ester-amine）s （defined as PEA） with controlled molecular structures were synthesized through reacting excessive piperazine with phthalicdiglycol diacrylate （PDDA） and 1,1,1-trimethylolpropane triacrylate （TMPTA） at a constant secondary amine/acrylate group ratio of 1.5/1 and at different PDDA/TMPTA molar ratios. Both IR and ^1H-NMR spectra indicated that all acrylate groups were consumed in the reaction, based on which the structural parameters were calculated from the ^1H-NMR spectra. With decreasing PDDA/TMPTA ratio, the content of secondary amine, degree of branching, molecular weight, Tg and Td increased accordingly. These polymers were further used as both crosslinkers and flexibilizers for a linear epoxy resin E51 to form cured films under ambient condition. The gel content, relative hardness and Tg of the resulting films increased as PEA molecules changed from linear to highly branching structures. Due to the flexibility of PEA molecules, all the films possessed excellent mechanical performance.

关键词： Poly(ester-amine) Molecular structure Epoxy resin Cured film.

Effect of mechanical vibration process parameters on the cement plugs properties for abandoned wells

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Petroleum Science 2023年第4期20卷 2428-2441页

作者： Hang-ming Liu Yang-Ye He ji-fang Wan Lin Chen Xian-Zhong Yi Yuan-Hua Zhou Yu-Xian He Xiang-Gui ming Lu Ren Cooperative Innovation Center of Unconventional Oil and Gas Yangtze University(Ministry of Education&Hubei Province)WuhanHubei430100China School of Mechanical Engineering Yangtze UniversityJingzhouHubei434023China CNPC Engineering Technology R&D Company Limited Beijing102206China College of Safety and Ocean Engineering China University of Petroleum-BeijingBeijing102249China Engineering Technology Research Institute CNPC Bohai Drilling Engineering Co.Ltd.Tianjin300457China

A high-quality plug of the abandoned wellbore is considered an essential technical aspect of the oil and gas well abandonment technology system. This paper presents a method of active mechanical excitation to enhance the quality of wellbore plug barriers. An indoor simulation platform is developed, and the effects of different combinations of vibration frequency, amplitude and duration on the properties of the wellbore plug cement material are investigated. It is observed that the optimal combination of excitation parameters occurs at a vibration frequency of 15 Hz, a vibration time of 6 min, and a vibration amplitude of 3 mm. Compared with the condition without the vibration process, the cementing strength, compressive strength, and tensile strength of wellbore cement plug with the optimal mechanical vibration process could increase by 51%, 38% and 20%, respectively, while the porosity decreases by 5%. As determined by scanning electron microscopy of the set cement's microstructure, mechanical vibration effectively eliminates internal porosity and improves the set cement's density. The optimal excitation parameters obtained from the test can guide the design of the vibration plugging tool. The designed vibration plugging tool is simulated in the near field. The cement plug cementation quality tester tests the vibrating and non-vibrating samples, and the cementation ratio is calculated. The test results show that the average cementation ratio of vibrating samples is 0.89375, and that of non-vibrating samples is 0.70625, and the cementation quality is improved by 27%. It is concluded that it not only provides essential data for the design of mechanical vibration plug apparatus, on-site vibration plugs, and the development of operational specifications for vibration plugs, but also provides solid engineering guidance.

关键词： Plugging and abandonment Cement plug Vibration Mechanical properties Microstructure

Unstable Surface Modes in Finite Chain Computations:Deficiency of Reflection Coefficient Approach

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Communications in Computational Physics 2010年第6期8卷 143-158页

作者： Shaoqiang Tang ming fang Center for Applied Physics and Technology and LTCSCollege of EngineeringPeking UniversityBeijing 100871China

In this paper,we investigate the stability for a finite harmonic lattice under a certain class of boundary conditions.A rigorous eigenvalue study clarifies that the invalidity of Fourier modes as the basis results in the deficiency of standard reflection coefficient approach for stability *** a certain parameter range,unstable surface modes exist in the form of exponential decay in space,and exponential growth in *** approximate eigen-polynomial is proposed to ease the stability ***,the eigenvalues with small positive real part quantitatively explain the long time instability in wave propagation *** results verify the analysis.

关键词： Unstable surface mode reflection coefficient finite chain

Study on Evaluation Method of Failure Pressure for Pipeline with Axially Adjacent Defects

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China Ocean Engineering 2023年第4期37卷 598-612页

作者： SUN ming-ming fang Hong-yuan DU Xue-ming WANG Wen-hua LI Xin School of Water Conservancy and Transportation Zhengzhou UniversityZhengzhou 450001China National Local Joint Engineering Laboratory of Major Infrastructure Testing and Rehabilitation Technology Zhengzhou 450001China Collaborative Innovation Center of Water Conservancy and Transportation Infrastructure Safety Zhengzhou 450001China Yellow River Laboratory Zhengzhou UniversityZhengzhou 450001China State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China School of Hydraulic Engineering Faculty of Infrastructure EngineeringDalian University of TechnologyDalian 116024China

The interaction between axially adjacent defects is more significant than that between circumferentially aligned ***,the existing failure pressure assessment methods cannot accurately predict the failure pressure of axial adjacent *** the paper,the finite element model is adopted to analyze the influence of defect size,distribution mode and spacing between adjacent defects on failure pressure.A new failure pressure evaluation method is proposed by establishing the effective depth calculation model of corrosion colony with different distribution *** burst test of X52 pipeline is carried out to verify the applicability of the *** shows that the results of new method are consistent with the test results of pipeline with various defects and steel grades.

关键词： steel pipeline effective depth axially adjacent defects burst test evaluation method