Research on stability of the accumulated rock-soil body of reservoir bank under rainfall condition

The shear strength parameters property of rock-soil aggregates in embankment slope of reservoir, that is, the relationship between cohesion and gravel content, between friction angle and gravel content, and the relationship between cohesion and water content, between friction angle and water content, is studied based on the direct shear test results, the shear strength change law of the rock-soil aggregates is given, and the unsaturated shear strength formulation of rock-soil aggregates that could consider suction and saturation degree influence is put forward in this paper, through which the sliding or failure physical mechanism of this type of slope under the condition of rainfall infiltration is studied. Also the 3D unsteady saturated-unsaturated seepage field and its FEM resolving mode are established based on the analysis of the slope rainfall infiltration process. Case study with this method indicates that the minimum safety factor of the accumulated rock-soil aggregates dose not arrive at the moment of rainfall cessation, but appears several hours after the rainfall cessation, this phenomenon is in accordance with the practical slope engineering’s failure process and could explain appropriately the slope failure caused by rainfall infiltration. Research results in this paper have an important reference value for the research on stability of the accumulated rock-soil aggregates in embankment slope of reservoir, and can enrich the stability analysis method and relevant theory of reservoir embankment slope. Supported by the National Natural Science Foundation of China (Grant Nos. 50539010, 50539110, 50809025, 50539030-1-3), National Science and Technology Support Plan of China (Grant Nos. 2006BAC14B03, 2008BAB29B06, 2008BAB29B03), Opening Fund of Geotechnical Mechanic and Engineering Key Laboratory of the Ministry of Water Recourses of China (Grant No. G07-03), Science and Technology Support Project of China Hydropower Engineering Consulting Group Co. (Grant No. CHC-KJ-2007-02), Special Scientific Research Fund of Doctor Subjects of Colleges and Universities: Research on Diagnosis Method of Concrete Dam Crack Transferring     

Rock fracture under anti-plane shear (Mode III) loading

Anti-plane punch-through shear test and anti-plane four-point bending test are used to study the crack initiation and propagation under anti-plane shear (Mode III) loading. The tensile and shear stresses at the crack tip are calcualted by finite element method. The results show that under Mode III loading the maximum principal stress σ₁ at crack tip is smaller or a little larger than the maximum shear stress τ_max. Since the tensile strength of brittle rock is much lower than its shear strength, σ₁ is easy to reach its critical value before τ_max reaches its critical value and thus results in Mode I fracture. The fracture trajectory is helicoid and the normal direction of tangential plane with the fractured helicoid is along the predicted direction of the maximum principal stress at the notch tip. It is further proved that Mode I instead of Mode III fracture occurs in brittle rock under Mode III loading. The fracture mode depending on the fracture mechanism must be distinguished from the loading form. Foundation item: Project (50374073) supported by the National Natural Science Foundation of China; project (2002032256) supported by the Postdoctor Science Foundation of China     

Influences of rainfall infiltration on stability of accumulation slope by in-situ monitoring test

In order to improve the understanding of the fundamental mechanism of rainfall infiltration induced landslides in accumulation slope and to clarify some important characteristics of slope performance, artificial rainfall simulation tests and field synthetic monitoring were carried out on a typical accumulation slope of Shangrui Freeway in Guizhou Province, China. The monitoring results show that the most accumulation landslides caused by rainfall infiltration are shallow relaxation failure, whose deformation zone lies within the top 0–4 m soil layer. The deformation of slope gradually reduces from the surface, where the greatest deformation lies in, to the deep part of slope. The average percentage of infiltration during the first 2 h is 86%, and then it reduces gradually with time because of the increase of the surface runoff. The average percentage of infiltration drop to a relatively stable value (50%) after 6 h. Rainfall infiltration causes obvious increase of pore-water pressure, which may result in a reduction of shear strength due to a decrease in effective stress and wetting-induced softening. The double-effect of rainfall infiltration is the main reason of rainfall infiltration induced landslides in accumulation slope. Foundation item: Project(50678175) supported by the National Natural Science Foundation of China     

含锯齿状结构面的岩质边坡稳定性拟动力分析

为了研究含有锯齿状结构面的岩质边坡稳定性，结合锯齿状结构面的剪切强度经验公式，综合考虑结构面参数、锚固效应、地震作用以及地下水位深度等因素的影响，基于改进的拟动力法推导了加锚结构面边坡抗滑稳定性安全系数计算式，并分析了岩石边坡稳定性的影响因素，结果表明：锯齿状结构面的抗剪强度与起伏角呈线性关系，随着起伏角的增大而增大；随着地震系数、滑动面倾角、水位深度、边坡倾角以及土体重度的增加，边坡稳定性降低，随着内摩擦角的增大而提高；锚固力越大，岩体的抗剪强度增大，边坡抗滑稳定性提高，但是锚固角的增大对边坡的稳定性起着负面效应。     

Automatic brush-plating technology for component remanufacturing

An automatic brush-plating system was developed for component remanufacturing. With this system, Ni/nano-alumina composite coatings from an electrolyte containing 20 g/L nano-alumina particles were prepared. Microstructure, surface morphology, microhardness and wear resistance of automatically plated coating and manually plated coatings were investigated comparatively. The results show that the automatically plated coatings are relatively dense and uniform and have lower friction coefficient of 0.089 under lubricant condition, when compared with manually plated coatings with friction coefficient of 0.14. Foundation item: Project(50235030) supported by the National Natural Science Foundation of China; Project(G1999065009) supported by the National Basic Research Program of China     

Strength of copolymer grouting material based on orthogonal experiment

Using the orthogonal experimental design method involving three factors and three levels, the flexural strength and the compressive strength of copolymer grouting material were studied with different compositions of water-cement ratio (mass fraction of water to cement), epoxy resin content, and waterborne epoxy curing agent content. By orthogonal range and variance analysis, the orders of three factors to influence the strength, the significance levels of different factors, and the optimized compound ratio scheme of copolymer grouting material mixture at different curing ages were determined. An empirical relationship among the strength of copolymer grouting material, the water-cement ratio, the epoxy resin content, and the waterborne epoxy curing agent content was established by multivariate regression analysis. The results indicate that water-cement ratio is the most principal and significant influencing factor on the strength. Epoxy resin content and waterborne epoxy curing agent content also have a significant influence on the strength. But epoxy resin content has a greater influence on the 7-day and 28-day flexural strength, and waterborne epoxy curing agent content has a greater influence on the 3-day flexural strength and the compressive strength. The copolymer grouting material with water-cement ratio of 0.4, epoxy resin content of 8% (mass fraction) and waterborne epoxy curing agent content of 2% (mass fraction) is the best one for repairing of cement concrete pavement. The flexural strength and the compressive strength have good correlation, and the ratio of compressive strength to flexural strength is between 1.0 and 3.3. Foundation item: Projects(40728003, 40772180, 40802064) supported by the National Natural Science Foundation of China; Project (07JJ4012) supported by the Hunan Provincial Natural Science Foundation of China; Project(20080430680) supported by China Postdoctoral Science Foundation; Project(B308) supported by Shanghai Leading Academic Discipline Project     

Wet friction performance of C/C-SiC composites prepared by new processing route

C/C-SiC composites with SiC island distribution were prepared via a new processing route. The fabrication process mainly included silicon infiltration by ultrasonic vibration, chemical vapor deposition (CVD), siliconizing, liquid phase impregnation and carbonization. The wear and friction properties were tested by an MM-1000 wet friction machine. The results show that SiC phases are mainly distributed between carbon fibers and pyrocarbons as well as among the pryocarbons. The dynamic friction coefficient of the composites decreases gradually from 0.126 to 0.088 with the increase of the surface pressure from 0.5 to 2.5 MPa at the same rotary speed. Furthermore, under the constant surface pressure, the dynamic friction coefficient increases from 0.114 to 0.126 with the increase of the rotary speed from 1 500 to 2 500 r/min. However, the coefficient decreases to 0.104 when the rotary speed exceeds 4 500 r/min. During the friction process, the friction coefficient of C/C-SiC composite is between 0.088 and 0.126, and the wear value is zero after 300 times brake testing. Foundation item: Project(2006CB600901) supported by the Major State Basic Research and Development Program of China; Project(0991015) supported by Guangxi Science Found, China; Project(200808MS083) supported by Guangxi Education Department Found     

First-principles lattice stability of Fe, Ru and Os

Lattice constants, total energies and densities of states of transition metals Fe, Ru and Os with BCC, FCC and HCP structures were calculated by the GGA+PBE functional and the ultrasoft pseudo-potential plane wave method, and compared with those of the first-principles projector augmented wave (PAW) method, CALPHAD method and experimental data. The results show that the lattice stability of this work is ΔG ^BCC-HCP>ΔG ^FCC-HCP>0, agreeing well with those of PAW method in the first-principles and CALPHAD method except for BCC-Fe. And the densities of state of HCP-Ru and Os have an obvious character of stable phase, agreeing completely with the results of the total energy calculations. Further analyses of atomic population show that the transition rate of electrons from s to p state for HCP, FCC and BCC crystals increases from Fe to Os, and a stronger cohesion, a higher cohesive energy or a more stable lattice between atoms of heavier metals are formed. Foundation item: Project(20070533118) supported by the Doctoral Discipline Foundation of Ministry of Education of China; Projects(50471058, 50271085) supported by the National Natural Science Foundation of China; Project supported by the Postdoctoral Foundation of Central South University, China     

Dynamic services selection algorithm in Web services composition supporting cross-enterprises collaboration

Based on the deficiency of time convergence and variability of Web services selection for services composition supporting cross-enterprises collaboration, an algorithm QCDSS (QoS constraints of dynamic Web services selection) to resolve dynamic Web services selection with QoS global optimal path, was proposed. The essence of the algorithm was that the problem of dynamic Web services selection with QoS global optimal path was transformed into a multi-objective services composition optimization problem with QoS constraints. The operations of the cross and mutation in genetic algorithm were brought into PSOA (particle swarm optimization algorithm), forming an improved algorithm (IPSOA) to solve the QoS global optimal problem. Theoretical analysis and experimental results indicate that the algorithm can better satisfy the time convergence requirement for Web services composition supporting cross-enterprises collaboration than the traditional algorithms. Foundation item: Project(70631004) supported by the Key Project of the National Natural Science Foundation of China; Project(20080440988) supported by the Postdoctoral Science Foundation of China; Project(09JJ4030) supported by the Natural Science Foundation of Hunan Province, China; Project supported by the Postdoctoral Science Foundation of Central South University, China     

草本植物加固边坡的力学原理

草本植物根系使边坡土体浅层成为土体和根系的复合材料,它通过根土摩擦作用和根的抗拉作用,增强了根系土层的整体抗剪强度,但至今人们对草本植物根系对边坡岩土体的作用及效应的研究仍很少,亟待深入。通过对草本植物根系加固边坡的力学原理进行了全面的分析,不但提出了根土作用的力学模型,而且对边坡增加的抗剪强度和增加的边坡稳定性系数进行了定量计算。从而为草本植物生态护坡提供了理论依据。     

Application of empirical mode decomposition based energy ratio to vortex flowmeter state diagnosis

To improve the measurement performance, a method for diagnosing the state of vortex flowmeter under various flow conditions was presented. The raw sensor signal of the vortex flowmeter was adaptively decomposed into intrinsic mode functions using the empirical mode decomposition approach. Based on the empirical mode decomposition results, the energy of each intrinsic mode function was extracted, and the vortex energy ratio was proposed to analyze how the perturbation in the flow affected the measurement performance of the vortex flowmeter. The relationship between the vortex energy ratio of the signal and the flow condition was established. The results show that the vortex energy ratio is sensitive to the flow condition and ideal for the characterization of the vortex flowmeter signal. Moreover, the vortex energy ratio under normal flow condition is greater than 80%, which can be adopted as an indicator to diagnose the state of a vortex flowmeter. Foundation item: Project(200801346) supported by the China Postdoctoral Science Foundation; Project(2008RS4022) supported by the Hunan Postdoctoral Scientific Program; Project(2008) supported by the Postdoctoral Science Foundation of Central South University     

Electron bandstructure of kaolinite and its mechanism of flotation using dodecylamine as collector

The bulk electronic structure of kaolinite (001) plane was studied with quantum mechanical calculations. The CASTEP parameterization of ultrasoft pseudopotentials without core corrections was used to optimize the structure of kaolinite bulk and slab models. The results show that Fermi energy of kaolinite (001) plane is 3.05 eV, and the band gap is 4.52 eV. The partial density of states (PDOS) of kaolinite (001) plane indicates that Al—O and Si—O bonds on the mineral surface are highly polar. The oxygen atoms of hydroxyl groups in surface layer are capable of forming hydrogen bond with the head group of cationic collectors. The properties of dodecylamine (DDA) cation were also calculated by density function theory (DFT) method at B3LYP/6-31G (d) level for illuminating the flotation processes of kaolinite. Besides the electrostatic attraction, the mechanism between kaolinite and DDA is found to be hydrogen bonds under acidic condition. Foundation item: Project(2005CB623701) supported by the Major State Basic Research and Development Program of China; Project(50874118) supported by the National Nature Science Foundation of China; Project(2007B52) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China     

黄土基岩接触面滑坡滑带土物理力学特性及微观结构

滑带土抗剪强度取值及微观结构特性对于边坡稳定及防治具有重要意义。以陕西延安地区二庄科滑坡为研究对象,通过剪切试验、扫描电镜及X射线衍射仪等,对典型黄土基岩接触面滑坡滑带土物理力学特性及微观结构进行研究;通过剪切试验得到不同含水率、不同干密度条件下滑带土的抗剪强度参数及其与含水率、干密度之间的相关性函数;通过研究其微观结构及矿物成分,分析了不同干密度、不同垂直压力条件下的土样微观结构。结果表明:随着含水率的减小和干密度的增加,土样的抗剪强度参数均有所提高;黏聚力与含水率呈负指数关系,内摩擦角与含水率呈负线性关系,黏聚力、内摩擦角分别与干密度呈正线性关系;随着垂直压力的增大,孔隙离散指数增大,颗粒离散指数、孔隙(颗粒)平均形态系数、孔隙(颗粒)定向概率熵及孔隙(颗粒)定向分维数均减小;随着干密度的增大,颗粒定向概率熵及颗粒定向分维数均增大。     

Characteristics of magnetic memory signals for medium carbon steel under static tensile conditions

To test the magnetic signals leaked from the surface of specimens during loading, the experiments of the static tensile of medium carbon 45^# steel were carried out. The results show that the magnetic field strength values rapidly vary when the load began, and the curves of the magnetic field strength change from irregularity to regularity with the increase of the load. Furthermore, by comparing with the state of on-line testing, it is found that the magnetic signals of out-of-line testing has more practicability. In the course of loading, though the dots of passing zero of the magnetic field strength continually changed their positions and quantities, the last rupture places were always approached by the dots of passing zero since the elastic loading phase. Some certain relations should exist between external stress and changing of magnetic signals inside the material, and correlative explanation is made based on dislocation theory and the mechanism of magnetic domain action, which provides the basis for further research of magnetic memory. Foundation item: Project(50235030) supported by the National Natural Science Foundation of China     

Strength and elastic properties of sandstone under different testing conditions

A laboratory experimental program performed on Wuhan sandstones was presented under monotonic loading, partial cyclic loading during loading path and sine wave cyclic loading with different strain rates to compare uniaxial compression strength and elastic properties （elastic modulus and Poisson ratio） under different conditions and influence of pore fluid on them. When the loading strain rates are 10^-5, 10^-4 and 10^-3/s, uniaxial compression strengths of dry sandstones are 82.3, 126.6 and 141.6 MPa, respectively, and that of water saturated sandstones are 70.5, 108.3 and 124.1 MPa, respectively. The above results show that the uniaxial compression strength increases with the increase of strain rate, however, variation of softening coefficient is insignificant. Under monotonic loading condition, tangent modulus increases with an increment of stress （strain） to a maximum value at a certain stress level, beyond which it starts to decline. Under the partial cyclic loading during loading path condition, unloading or reloading modulus is larger than loading modulus, and unloading and reloading moduli are almost constants with respect to stress level, especially unloading modulus. Under the sine wave cyclic loading condition, tangent modulus and Poisson ratio display asymmetric ‘X＇ shape with various strain, and the average unloading modulus is larger than the average loading modulus.     

Microstructure and wear resistance of electro-thermal explosion sprayed stellite coating used for remanufacturing

Electro-thermal explosion directional spraying was used to prepare the stellite coating on substrate of the AISI 1045 steel. The morphologies of cross-section and worn scar, porosity, distribution of elements, micro-hardness and wear resistance of the coating were determined by means of SEM, EDAX, micro-hardness tester and sliding wear tester. Because of the compact construction, good bonding and high hardness, the coating is characterized by good wear resistance. The results show that the mainly failure mode of the stellite coating is micro-plowing. Foundation item: Project(2003AA331130) supported by Hi-tech Research and Development Program of China; Project(50235030) supported by the National Natural Science Foundation of China     

A novel scale-free network model based on clique growth

A novel scale-free network model based on clique (complete subgraph of random size) growth and preferential attachment was proposed. The simulations of this model were carried out. And the necessity of two evolving mechanisms of the model was verified. According to the mean-field theory, the degree distribution of this model was analyzed and computed. The degree distribution function of vertices of the generating network P(d) is 2m ² m ₁⁻³ (d − m ₁ + 1)⁻³, where m and m ₁ denote the number of the new adding edges and the vertex number of the cliques respectively, d is the degree of the vertex, while one of cliques P(k) is 2m ² k ⁻³, where k is the degree of the clique. The simulated and analytical results show that both the degree distributions of vertices and cliques follow the scale-free power-law distribution. The scale-free property of this model disappears in the absence of any one of the evolving mechanisms. Moreover, the randomicity of this model increases with the increment of the vertex number of the cliques. Foundation item: Projects(60504027, 60573123) supported by the National Natural Science Foundation of China; Project(20060401037) supported by the National Postdoctor Science Foundation of China; Project(X106866) supported by the Natural Science Foundation of Zhejiang Province, China     

Study on mechanical properties of warm compacted iron-base materials

Mechanical properties of the warm compacted iron-base powder metallurgy materials were compared with those of conventional cold compacted materials. Factors such as compaction temperature, lubricant concentration and lubricant′s property were studied. A lubricant for warm compaction powder metallurgy was developed. An iron-based powder metallurgy material with a green density of 7.31 g/cm3 (a relative density of 92.5%) can be obtained by pressing the powder at 700 MPa and 175 ℃. The sintered materials have a density of 7.2 g/cm3, an elongation of 2.1% and a tensile strength of 751 MPa compared to 546 MPa using conventional cold compaction with the same lubricant and 655 MPa using warm compaction with other lubricant. Compact density and mechanical properties were influenced strongly by the compacting temperature. Although the best quality compacts can be obtained at 175 ℃, warm compaction within 165 to 185 ℃ can give high density compacts. Evidence shows that compact density depends on the friction coefficient of the lubricant.     

Synthesis and photophysical and electrochemical properties of new cyclometalated platinum complex containing oxadiazole ligand

A new cyclometalated platinum complex containing 2, 5-bis（naphthalene-1-yl）-1,3,4-oxadiazole ligand was synthesized and characterized. The UV-Vis absorptions and photoluminescent properties of the ligand and its platinum complex were investigated A characteristic metal-ligand charge transfer absorption peak at 439 nm in the UV spectrum and a strong emission peak at 625 nm in the photoluminescence spectrum were observed for this complex in dichloromethane. Cyclic voltammtry （CV） analysis shows that the EHOMO （energy level of the highest occupied molecular orbital） and ELUMO （energy level of the lowest unoccupied molecular orbital） of the platinum complex are about -5.69 and -3.25 eV, respectively, indicating that the oxadiazole-based platinum complex has a potential application in electrophosphorescent devices used as a red-emitting material.     

Delay-independent decentralized H ∞ control for multi-channel discrete-time systems with uncertainties

A robust decentralized H∞ control problem was considered for uncertain multi-channel discrete-time systems with time-delay. The uncertainties were assumed to be time-invariant, norm-bounded, and exist in the system, the time-delay and the output matrices. Dynamic output feedback was focused on. A sufficient condition for the multi-channel uncertain discrete time-delay system to be robustly stabilizable with a specified disturbance attenuation level was derived based on the theorem of Lyapunov stability theory. By setting the Lyapunov matrix as block diagonal appropriately according to the desired order of the controller, the problem was reduced to a linear matrix inequality （LMI） which is sufficient to existence condition but much more tractable. An example was given to show the efficiency of this method.