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20世纪50年代中国科学院数学研究所数论讨论班与中国解析数论的发展
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作者 邹大海 魏蕾 《自然科学史研究》 CSCD 北大核心 2023年第2期131-150,共20页
20世纪50年代,中国科学院数学研究所数论组举办讨论班训练青年研究人员。经过四五年的系统训练,培养了一支数论研究队伍,他们在解析数论尤其是哥德巴赫猜想研究上连续取得了具有国际影响的重要成就。文章考察了从1953年至1958年数学研... 20世纪50年代,中国科学院数学研究所数论组举办讨论班训练青年研究人员。经过四五年的系统训练,培养了一支数论研究队伍,他们在解析数论尤其是哥德巴赫猜想研究上连续取得了具有国际影响的重要成就。文章考察了从1953年至1958年数学研究所数论小组的组建、学习和研究情况,探究了华罗庚领导下的数论讨论班的研究活动和学术生态,分析了华罗庚如何通过讨论班这一研习形式进行人才培养,揭示了我国解析数论研究取得重大突破的一些关键因素。 展开更多
关键词 解析数论 讨论班 华罗庚 越民义 王元 陈景润
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THERMOHYDRODYNAMIC LUBRICATION ANALYSIS ON EQUILIBRIUM POSITION AND DYNAMIC COEFFICIENT OF JOURNAL BEARING 被引量:1
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作者 李元生 于明 +1 位作者 敖良波 岳珠峰 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2012年第3期227-236,共10页
The finite element method (FEM) is introduced to calculate the oil film pressure and temperature distribution of a journal bearing. The perturbation is performed directly on the finite element equation. Consequently... The finite element method (FEM) is introduced to calculate the oil film pressure and temperature distribution of a journal bearing. The perturbation is performed directly on the finite element equation. Consequently, the Jacobian matrices of the oil film forces are concisely obtained. The equilibrium position of the bearing with a given static load is found by the Newton-Raphson method. As byproducts, dynamic coefficients are obtained simultaneously without any extra computing time. From the numerical results, it is concluded that the effects of film temperature on stiffness coefficients are bigger than those on damping coefficients. With the increase of rotational speed, the load capacity and the stiffness coefficients of the journal bearing are increased when the eccentricity is small, while decreased when the eccentricity is big. 展开更多
关键词 thermohydrodynamic lubrication thermal effect finite element analysis journal bearing
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对完善吨煤工资包干办法的一点看法
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作者 梁永泉 《煤炭经济研究》 1985年第11期37-38,共2页
吨煤工资包干是适合煤炭企业特点、提高煤炭企业经济效益和劳动生产率的好办法。但目前有一些问题需要进行探讨和研究解决。本文拟就如何保证职工的工资增长幅度与生产发展速度保持一个合理的关系,作到工资成本的比重随着产量的增加而... 吨煤工资包干是适合煤炭企业特点、提高煤炭企业经济效益和劳动生产率的好办法。但目前有一些问题需要进行探讨和研究解决。本文拟就如何保证职工的工资增长幅度与生产发展速度保持一个合理的关系,作到工资成本的比重随着产量的增加而逐年降低,谈一些粗浅的看法。 展开更多
关键词 企业经济效益 原煤产量 变动成本 单位成本 产品成本 成木 元略 分营 元润
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持刀毁桔园,坐牢又赔钱
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作者 向洋 《林业与生态》 1994年第6期6-6,共1页
关键词 桔园 世界银行贷款 犯罪行为 元润
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今年国内企业500强
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《品牌与标准化》 2011年第19期33-37,共5页
关键词 股份有限公司 股份公司 国内企业 元润 公司名称 公司的商号
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Leaching of Copper and Zinc in a Garden Soil Receiving Poultry and Livestock Manures from Intensive Farming 被引量:5
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作者 HAO Xiu-Zhen ZHOU Dong-Mei +1 位作者 CHEN Huai-Man DONG Yuan-Hua 《Pedosphere》 SCIE CAS CSCD 2008年第1期69-76,共8页
The leaching characteristics of a garden soil may be greatly affected by application of poultry and livestock manures from intensive farming. Packed soil columns of a garden soil (CK) and the soils after respectivel... The leaching characteristics of a garden soil may be greatly affected by application of poultry and livestock manures from intensive farming. Packed soil columns of a garden soil (CK) and the soils after respectively receiving 2% pig manure (PM), chicken manure (CM), and commercial organic manure (OM) were leached with 0.05 mol L^-1 Ca(NO3)2 and 0.01 mol L 1 EDTA solutions. The leachate EC (electric conductivity) values gradually increased at the beginning and then reached a stable value when the soil columns were leached with 0.05 mol L^-1 Ca(NO3)2 solution. The leachate EC values showed a peak-shape when leached with 0.01 mol L^-1 EDTA solution. In all the soil columns, the pH values of the leachates decreased with increase of displacement volumes when the Ca(NO3)2 solution was used. The total amounts of Cu and Zn eluted from the four soil columns were significantly correlated with the extracted soil Cu and Zn concentrations by 1.0 mol L^-1 NH4NO3, but were not correlated with the leachate dissolved organic carbon (DOC) contents. The Zn concentration in the leachate of the PM-treated soil column with 0.05 mol L^-1 Ca(NO3)2 solution was above the Quality Standard III for Ground Water of China (GB/T 14848-93, Zn 〈 1.0 mg L^-1). When compared with 0.05 mol L^-1 Ca(NO3)2, the EDTA solution significantly accelerated Cu and Zn elutions in the manure-treated columns. This suggested that applying poultry and livestock manures from intensive farming to farmland might pose a threat to the groundwater quality. 展开更多
关键词 COPPER garden soil LEACHING MANURES ZINC
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An elasto-plastic constitutive model incorporating strain softening and dilatancy for interface thin-layer element and its verification 被引量:1
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作者 彭凯 朱俊高 +2 位作者 冯树荣 王荣 刘汉龙 《Journal of Central South University》 SCIE EI CAS 2012年第7期1988-1998,共11页
The mechanical behaviors of the interface between coarse-grained soil and concrete were investigated by simple shear tests under condition of mixed soil slurry (bentonite mixed with cement grout).For comparison,the in... The mechanical behaviors of the interface between coarse-grained soil and concrete were investigated by simple shear tests under condition of mixed soil slurry (bentonite mixed with cement grout).For comparison,the interfaces both without slurry and with bentonite slurry were analyzed.The experimental results show that different slurries exert much influence on the strength and deformation of soil/structure interface.Under mixed soil slurry,strain softening and shear dilatation are observed,while shear dilatation appears under the small normal stress of the interface without slurry,and shear contraction is significant under the condition of the bentonite slurry.The thickness of the interface was determined by analyzing the disturbed height of the sample with both simple shear test and particle flow code (PFC).An elasto-plastic constitutive model incorporating strain softening and dilatancy for thin layer element of interface was formulated in the framework of generalized potential theory.The relation curves of shear stress and shear strain,as well as the relation curves of normal strain and shear strain,were fitted by a piecewise function composed by hyperbolic functions and resembling normal functions.The entire model parameters can be identified by tests.The new model is verified by comparing the measured data of indoor cut-off wall model tests with the predictions from finite element method (FEM).The FEM results indicate that the stress of wall calculated by using Goodman element is too large,and the maximum deviation between the test data and prediction is about 45%.While the prediction from the proposed model is close to the measured data,and the error is generally less than 10%. 展开更多
关键词 simple shear test mixed soil slurry DILATANCY particle flow code generalized potential theory constitutive model FEM
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EFFECTS OF MANUFACTURING ERRORS ON GAS LUBRICATED JOURNAL BEARING WITH COMPLIANT SURFACE 被引量:1
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作者 董卫华 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 1995年第1期39-44,共6页
A theoretical study has been performed to investigate the influence of manufacturing errors on the bearing housing of a gas lubricated journal bearing with compliant surface I in particular on the bearing load capacit... A theoretical study has been performed to investigate the influence of manufacturing errors on the bearing housing of a gas lubricated journal bearing with compliant surface I in particular on the bearing load capacity. A gas film thickness distribution is presented, in which errors o f both circumferential and axial bearing housing are considered. The influence of the errors on bearing performance is compared between rigid and compliant surface bearings. It was shown that the compliant surface bearings are less sensitive to the manufacturing errors than the rigid surface bearings. Thelefore, the cost of compliant surface bearing could be reduced by setting a larger manufacturing error tolerance. 展开更多
关键词 hydrodynamic gas-lubricated bearings finite element analysis journal bearings compliant bearings load-carrying capacity
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Investigation on tribological behaviors of neodymium dialkyldithiophosphate 被引量:3
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作者 田言 任南琪 +2 位作者 冯玉杰 孙丽欣 蔡伟民 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2004年第1期34-37,共4页
Neodymium dialkylthiophosphate (NdDDP) with alkyls of isopropyl and isooctyl were synthesized by exchanged reaction respectively. The structures of the two NdDDPs were determined using IR and XRD. Properties of anti... Neodymium dialkylthiophosphate (NdDDP) with alkyls of isopropyl and isooctyl were synthesized by exchanged reaction respectively. The structures of the two NdDDPs were determined using IR and XRD. Properties of anti-wear and friction-reducing of the two additives were investigated with four ball experiment and the commercial anti-wear additive ZDDP was selected as control. The elemental analysis of the wear scars after 10 s friction at low stress were investigated by EDXA (Energy Dispersion Analysis of X-ray). Primary results showed that the NdDDPs possess better lubrication ability than ZDDP. This might mainly be contributed to the formation of a boundary film containing Nd2O3, FeS and sulphate, phosphate, organo-sulfide, etc., and a neodymium-rich diffused layer which changes the crystal structure of the surface of friction materials. 展开更多
关键词 rare earths neodymium dialkyldithiophosphate anti-wear and friction-reducing additives boundary lubricating film
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Study on Preparation and Engine Bench Test of Friction-Reducing and Repairing Additive to Lubricating Oils
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作者 ShiPeijing QiaoYulin XuBinshi MaShining 《China Petroleum Processing & Petrochemical Technology》 SCIE CAS 2003年第4期57-62,共6页
A new kind of friction-reducing and repairing additive containing nano-scale copper and rare earth compounds were prepared by means of synthesis and compounding methods. The performance of the said additive was invest... A new kind of friction-reducing and repairing additive containing nano-scale copper and rare earth compounds were prepared by means of synthesis and compounding methods. The performance of the said additive was investigated by engine bench test, and was compared to the performance of similar domestic and imported additives. The deterioration of lube oils containing additives over different time intervals was studied by means of plasma spectrometry and mass spectrometry, and the effect of additive package on engine power was also studied. Test results have revealed that the synthetic additive package can provide good anti-wear performance to the tribo-pairs. In particular, after 300 hour application of the said additive package the connection rod shaft and copper sleeve showed 'zero wear' to achieve the in situ dynamic repairing of tribo-pairs. Application of the said synthetic additive can effectively improve the engine power performance and extend the engine service life. 展开更多
关键词 rare earths ADDITIVE COPPER wear test
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Application of Developed Grid-GA Distributed Hydrologic Model in Semi-Humid and Semi-Arid Basin 被引量:5
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作者 王莉莉 李致家 包红军 《Transactions of Tianjin University》 EI CAS 2010年第3期209-215,共7页
A grid and Green-Ampt based (Grid-GA)distributed hydrologic physical model was developed for flood simulation and forecasting in semi-humid and semi-arid basin. Based on topographical information of each grid cell e... A grid and Green-Ampt based (Grid-GA)distributed hydrologic physical model was developed for flood simulation and forecasting in semi-humid and semi-arid basin. Based on topographical information of each grid cell extracted fi'om the digital elevation model (DEM) and Green-Ampt infiltration method, the Grid-GA model takes into consideration the redistribution of water content, and consists of vegetation and root interception, evapotranspiration, runoff generation via the excess infiltration mechanism, runoff concentration, and flow routing. The downslope redis- tribution of soil moisture is explicitly calculated on a grid basis, and water exchange among grids within runoff routing along the river drainage networks is taken into consideration. The proposed model and Xin'anjiang model were ap- plied to the upper Lushi basin in the Luohe River, a tributary of the Yellow River, with an area of 4 716 km2 for flood simulation. Results show that both models perform well in flood simulation and can be used for flood forecasting in semi-humid and semi-arid region. 展开更多
关键词 distributed hydrologic model digital elevation model (DEM) Green-Ampt REDISTRIBUTION excess infil- tration mechanism semi-humid and semi-arid basin
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冬日密语
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《城色》 2007年第3期65-65,共1页
是不是一到冬天就把自己包裹起来,一切问题都等来年再说?小如把保养脸面的热情拿出三分之一,对自己的身体好一点。
关键词 三分之一 元润 元典
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Effects of the radial force on the static contact properties and sealing performance of a radial lip seal 被引量:11
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作者 JIA XiaoHong GUO Fei +3 位作者 HUANG Le WANG LongKe GAO Zhi WANG YuMing 《Science China(Technological Sciences)》 SCIE EI CAS 2014年第6期1175-1182,共8页
The radial force is a critical factor to determine the sealing performance of radial lip seals.The effects of radial force produced by garter spring and interference on the static contact properties and sealing perfor... The radial force is a critical factor to determine the sealing performance of radial lip seals.The effects of radial force produced by garter spring and interference on the static contact properties and sealing performance of a radial lip seal are investigated by numerical simulations and experiments.Finite-element analysis and mixed elastohydrodynamic lubrication simulation are used.Radial force,contact width,temperature in the sealing zone,the reverse pumping rate and friction torque are measured.A critical value of interference for a cost-effectively designed radial lip seal is found.Spring force is required to compensate the decrease of the radial force because of the interference and used as a possible way to obtain intelligent control of sealing performance.The quantitative results gotten in this study could provide guide for the seal design and improvement. 展开更多
关键词 lip seal radial force static contact properties pumping rate friction torque
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