检索结果-南通市图书馆

aging structures in the presence of incomplete deterioration information

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2016年第9期17卷 677-688页

作者： Cao wang quan-wang li Long PANG A-ruing ZOU Department of Civil Engineering Tsinghua University Beijing 100084 China School of Civil Engineering The University of Sydney Sydney 2006 Australia

The performance of an aging structure is commonly evaluated under the framework of reliability analysis, where the uncertainties associated with the structural resistance and loads should be taken into account. In practical engineering, the probability distribution of resistance deterioration is often inaccessible due to the limits of available data, although the statistical parameters such as mean value and standard deviation can be obtained by fitting or empirical judgments. As a result, an error of structural reliability may be introduced when an arbitrary probabilistic distribution is assumed for the resistance deterioration. With this regard, in this paper, the amount of reliability error posed by different choices of deterioration distribution is investigated, and a novel approach is proposed to evaluate the averaged structural reliability under incomplete deterioration information, which does not rely on the probabilistic weight of the candidate deterioration models. The reliability for an illustrative structure is computed parametrically for varying probabilistic models of deterioration and different resistance conditions, through which the reliability associated with different deterioration models is compared, and the application of the proposed method is illustrated.

关键词： Time-dependent reliability Deterioration model Error quantification Averaged reliability Structural safety

Research,Development,and Production of V-N Microalloyed High Strength Rebars for Building in China

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2008年第2期15卷 81-86页

作者： YANG Cai-fu wang quan-li Central Iron and Steel Research Institute Beijing 100081 China Capital Iron and Steel Group Company Beijing 100041 China

The research,production,and application of V-N microalloyed high strength rebars in China were *** nitrogen in vanadium-containing rebars promotes the precipitation of fine V（C,N）particles,and markedly improves the precipitation strengthening effectiveness of ***,vanadium added to V-N microalloyed rebars can be reduced by 40% compared to the same strength level of vanadium-containing rebars.

关键词： high strength reinforced bar V-N microalloying precipitation strengthening

A convenient microwave-assisted synthesis of cinchona alkaloid-derived ligands

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2008年第12期19卷 1440-1444页

作者： Hai Bo wang Ping An wang quan Jun wang Xiao li Sun lin lin Jing Department of Chemistry School of Pharmacy Fourth Military Medical University Xi＇an 710032 China

An efficient synthesis of cinchona alkaloid-derived ligands based on solvent-free microwave-assisted reaction was described. The coupling of 1,4-dichlorophthalazine or 3,6-dichloropyridazine with quinine, cinchonine or cinchonidine provide bis-or monocinchona alkaloid-derived ligands in moderate to good yields （52-89%） within 15 min under optimum microwave conditions.

关键词： Cinchona alkaloids Solvent-free microwave synthesis AD reaction

Vertical ionization energies of halogen anions in solution

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2010年第6期53卷 1316-1321页

作者： CHENG XueMin,ZHU quan,wang XingJian,li YunKui & li XiangYuan College of Chemical Engineering,Sichuan University,Chengdu 610065,China College of Chemical Engineering Sichuan University Chengdu China

Based on the constrained equilibrium state theory,the nonequilibrium solvation energy is derived in the framework of the continuum *** formula for spectral shift and vertical ionization energy are deduced for a single sphere cavity with the point charge *** new model is adopted to investigate the vertical ionization for halogen atomic and molecular anions X(X = Cl,Br,I,Cl2,Br2,I2) in aqueous *** to the calculation using the CCSD-t/aug-cc-pVQZ method in vacuum,our final estimated vertical ionization energies in solution are very close to the experimental observations,while the traditional nonequilibrium solvation theory overestimates these vertical ionization energies.

关键词： vertical ionization energy spectral shift constrained equilibrium state

Rheological Behaviors of Polymers with Nanoparticles Tethered at Each End

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2024年第3期42卷 400-406,I0009页

作者： Song-Qi Zhang Wen-Qing wang Jia-Ping lin li-quan wang Shanghai Key Laboratory of Advanced Polymeric Materials Key Laboratory for Ultrafine Materials of Ministry of EducationSchool of Materials Science and EngineeringEast China University of Science and TechnologyShanghai 200237China

The polymer with nanoparticles tethered at each end is a unique model for unraveling the effect of chain ends on the polymer dynamics. We investigated the rheological behavior of this kind of polymer by using nonequilibrium molecular dynamics simulation. The effect of polymer lengths and nanoparticle radii on the complex moduli and viscosity was examined. The dependence of complex moduli on the frequency becomes less pronounced as the polymer is short or the nanoparticle is large. The shear thinning behavior was revealed for these systems, and the scaling exponent of complex viscosity with respect to the frequency was found to change from-1/2 to-3/4 as the polymer shortens or the nanoparticle enlarges. The rheological behavior was further explained by analyzing the mean square distance of nanoparticles. The simulation results were compared with the existing experimental finding, showing an agreement. The work provides information for understanding the chain end effect on polymer rheology.

关键词： Polymer rheology Modulus Viscosity Molecular dynamics

Elective percutaneous intervention for unprotected left main coronary artery stenosis complicated with left anterior descending artery chronic total occlusive lesions

在线全文

学校读者我要写书评

暂无评论

Chinese Medical Journal 2010年第7期123卷 816-821页

作者： YANG Gui-tang HAN Ya-ling JING quan-min wang Shou-li li Yi MA Ying-yan wang Geng LUAN Bo wang Xiao-zeng wang Bin wang Zu-lu wang Dong-mei Department of Cardiology Shenyang Northern HospitalShenyang Liaoning 110840 China

Background The patients with unprotected left main coronary artery （ULMCA） stenosis and chronic total occlusion （CTO） lesions at the left anterior descending （LAD） artery are often recommended for bypass surgery. However, some of these patients are deemed inoperable or are at high risk for surgery. In this study, we explored strategies and evaluated the efficacy of percutaneous coronary intervention for the treatment of ULMCA stenosis complicated by LAD CTO. Methods From November 2001 to July 2009, 78 patients with ULMCA stenosis and LAD CTO lesions were selectively treated with stenting. Six patients （7.7%） refused surgery due to their young age （S40 years）, and the other 72 patients （92.3%） were unsuitable for surgery. Reasons for poor surgical candidacy included advanced age （〉80 years）, chronic obstructive pulmonary, unsuitable distal target vessels for bypass, EuroSCORE ≥6, and so on. Four different strategies were applied based on the degree of left main stenosis and the ostial diameter and involvement of the left circumflex. Results Total procedural success was achieved in 94.9%, there were no deaths or thromboses. Five patients （6.4%） experienced non-Q-wave myocardial infarction in hospital. At long-term follow-up （（52±28） months）, there were 3 cardiac deaths （3.8%） and 4 （5.1%） nonfatal myocardial infarctions. Angiographic follow-up was performed in 50 patients （64.1%）, and target vessel revascularizations were required in 10 patients （12.8%）, among which 4 nonfatal myocardial infarction patients included. The rate of major adverse cardiac events was 16.7% （13/78）.Conclusions This study indicates that percutaneous intervention can be performed safely in high risk surgical patients with ULMCA and LAD CTO lesions based on individual therapeutic strategies. It may be feasible to apply this technique in selected patients mentioned above.

关键词： percutaneous coronary intervention chronic total occlusion left main coronary artery disease strategy

Thermal fatigue and wear of compacted graphite iron brake discs with various thermomechanical properties

在线全文

学校读者我要写书评

暂无评论

China Foundry 2024年第3期21卷 248-256页

作者： Gui-quan wang Zhuo Xu Zhong-li liu Xiang Chen Yan-xiang li School of Nuclear Equipment and Nuclear Engineering Yantai UniversityYantai 264005ShandongChina School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationBeijing 100084China

The increase in payload capacity of trucks has heightened the demand for cost-effective yet high performance brake *** this work,the thermal fatigue and wear of compacted graphite iron brake discs were investigated,aiming to provide an experimental foundation for achieving a balance between their thermal and mechanical *** graphite iron brake discs with different tensile strengths,macrohardnesses,specific heat capacities and thermal diffusion coefficients were produced by changing the proportion and strength of *** peak temperature,pressure load and friction coefficient of compacted graphite iron brake discs were analyzed through inertia friction *** morphology of thermal cracks and 3D profiles of the worn surfaces were also *** is found that the thermal fatigue of compacted graphite iron discs is determined by their thermal properties.A compacted graphite iron with the highest specific heat capacity and thermal diffusion coefficient exhibits optimal thermal fatigue *** of the matrix at low temperatures significantly weakens the function of alloy strengthening in hindering the propagation of thermal *** the reduced hardness,increasing the ferrite proportion can mitigate wear loss resulting from low disc temperatures and the absence of abrasive wear.

关键词： compacted graphite iron brake disc thermomechanical properties thermal fatigue wear

Effect of Mo and cold forging deformation on strength and ductility of cobalt-based alloy L605

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2024年第7期31卷 1811-1823页

作者： Zhong-lin wang Zhi-hua Gong quan li Han-sheng Bao School of Materials and Metallurgy Inner Mongolia University of Science and TechnologyBaotou 014017Inner MongoliaChina Institute of Special Steels Central Iron and Steel Research Institute Co.Ltd.Beijing 100081China

Mo element was added to cobalt-based alloy L605,and cold forging deformation was *** effects of the addition and cold forging deformation on the microstructure and mechanical properties of the alloy were studied by thermodynamic calculation,electron backscatter diffraction,transmission electron microscopy,and X-ray *** stacking fault energy(SFE)of the alloy decreased after the addition,and the formation of stacking faults and intersections were promoted to improve the strength and *** tensile strength of the alloy with Mo increased from 1190 to 1702 MPa after 24%cold deformation,producing significant work *** strengthening mechanism is strain-induced martensitic transformation(SIMT)and deformation *** alloy,combined with Mo and after 24%deformation,had both high strength and ductility in comparison with the original cobalt-based alloy *** is attributed to the lower SFE which caused the increase in stacking fault *** the tensile process,theε-hcp phase was easily generated at the stacking fault to reduce the stress concentration and increase the *** SIMT by adjusting the density of stacking faults can improve the mechanical properties of cobalt-based ***ε-hcp phase,the interaction between deformation twins and dislocations,and the interaction between e-hcp phases during cold forging deformation caused local stress concentration,lowering ductility and toughness.

关键词： Cobalt-based alloy-Stacking fault energy Strain-induced martensitic transformation Deformation twin Cold forging deformation

Preliminary Study on Spatial Variability and Distribution of Soil Available Microelements in Pinggu County, Beijing, China

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Agricultural Sciences in China 2008年第10期7卷 1235-1244页

作者： wang Shu-ying YU Tong-quan wang Jian-li YANG liu YANG Kai LU Ping New Technological Laboratory in Agriculture Application in Beijing Beijing University of Agriculture Beijing 102206 RR.China

The objectives of this study were to explore the spatial distribution of soil available microelements and to provide a firm foundation for scientifically formulated fertilizer. 1 076 soil samples were collected from Pinggu County of Beijing, China, and the contents of available Cu, Zn, Fe, and Mn in topsoil （0-20 cm） and subsoil （20-40 cm） were analyzed respectively. Descriptive statistics and geostatistics were used to analyze the data. The mean values of topsoil available Cu, Zn, Fe, and Mn were 1.96, 2.51, 17.32, and 10.91 mg kg^-1, respectively, which were at medium or at slightly above medium level. The topsoil content of the soil available microelements was more than that of subsoil. The result of semivariance analysis showed that the topsoil available Fe and Mn were spatially correlated at a larger distance of 21.6 and 45.3 km, and the available Cu and Zn were at a shorter distance of 3.1 and 2.9 km, respectively. The subsoil spatial correlation distances were obviously different from the topsoil, which were in the order of available Mn 〉 Cu 〉 Zn = Fe. The Kriging method was applied to calculate the unobserved points and was used to generate the contour map. The results showed that the structural factors, such as topology, soil types, and soil properties, were the main factors influencing the spatial distribution of topsoil available Fe and Mn. Topsoil available Cu and Zn contents were mainly affected by land use, and their contents in orchard and in vegetable land were greatly higher than in field. The spatial distribution of subsoil microelements was similar to that of the topsoil, which exhibited vertical distribution patterns. Fertilizer and pesticide application resulted in the higher contents of available Cu and Zn in Pinggu County. The higher content of available Zn is potentially harmful to soil environmental quality, which should be inspected.

关键词： soil available microelements semivariance spatial variability