冲淤变动型泥石流沟中物质启动 类型及机理研究(Ⅰ)

泥石流是一种高浓度的水、沙、砾混合流,是颗粒大小差异很大的固体和液体的联合运动,其中砂、砾主要按滚动及跃进状态迁移,是沟谷急剧演变的一个短历时的阶段性现象,属于典型的灾害地貌过程.基于实地考察和深入的研究。笔者分析了公路泥石流的基本特征,并分析提出了泥石流的启动条件、类型及其相应的机理.,Debris flow is a kind of high indicator compound liquid composed of water, sand and little rock, which is the movement of solid and liquid whose particles have great difference in size. In the debris flow's movement sand and little rock mainly move in rolling and leaping. Debris flow is a short stage phenomena for a short time in the course of the valley's radical evolution, and it's a typical calamity course. Based on explorations in-situ spot and deeply researches, the author analyzed the basic characters of the highways' debris flows, also proposed the debris flows' startup conditions and types.,     

从泥石流沟的岩土稳定性论冲淤变动型泥石流的物源问题——以西[ BF (昌)木(里)路平川泥石流为例

本文以极具典型的平川泥石流为例比较全面的分析 了冲淤变动型泥石流的物源问题.根据现场调研及室内岩土分析进行的研究成果显示,川西 南高山深谷地区的大型泥石流沟中的松散土体以中、粗粒段为主,其分布与地形密切相关; 位于泥石流沟中、前部位的松散土体的稳定性最差,是补给泥石流的重要物源;松散土体的 发育主要受控于地质及岩土环境,人类活动只能影响松散土体的稳定性.,The authors discuss roundly source of loose earth fo r impact-deposit debris flow to develop taking pingchuan debris flow,one of the quite typical impact-deposit debris flows in southwest sichuan province,as an example in this paper. on the basis of detailed investigations in-situ,geotechn ial testing in Lab and theory analysis,all results indicate obviously that moder ate and bulky loose earth in giant debris flow situating in southwest sichuan mo untainous area are main institute,whose tribulation are consistent with landform s.Loose earth locating in mid-forepart catchment are quite unstable,so often be comes main source of loose earth of debris flow.Formation of loose earth is cont rolled principally by geologic and geotechnical environment while human actions is the secondary factor for loose earth to form.In many times,human actions prov ide loose earth through loose earth stability.,     

冲淤变动型泥石流沟中物质启动类型及机理研究（Ⅱ）

对强度衰减启动型,冲刷切割启动型,沟槽（床）拖曳启动型等3种泥石流启动机理进行了较为深入的理论分析。     

Approach for Reliability Evaluation of Cross-Linked Polyethylene Under Combined Thermal and Vibration Stresses

Based on Wiener process model, a new approach for reliability evaluation of cross-linked polyethylene(XLPE) is proposed to improve the lifetime evaluation reliability of XLPE under multi-stressing conditions and study the failure probability distribution. In this paper, two accelerated aging tests are carried out under combined thermal and vibration conditions. The volume resistance degradation data of XLPE samples are tested with a24 h interval under the accelerated stressing conditions at(130℃, 12 m/s~2) and(150℃, 8.5 m/s~2), respectively.Nonlinear degradation data obtained from the experiment are transformed to linear intermediate-variable values using time scaling function, and then linearized degradation data are calculated and evaluated on the basis of linear Wiener process model. Considering traditional Arrhenius equation and inverse power criterion, parameters of the linear Wiener model are estimated according to the maximum likelihood function. The relationship curves on probability density and reliability are given, and the lifetime distribution of XLPE under different stressing conditions is also obtained for evaluating the reliability of XLPE insulation. Finally, the life expectancy of XLPE is 17.9 a under an allowance temperature of 90℃ and an actual vibration acceleration of 0.5 m/s~2. The approach and results in this paper may be used for reliability assessment of high-voltage multiple samples or apparatuses.     

Aerodynamic simulation of evacuated tube maglev trains with different streamlined designs

Based on the Navier-Stokes (N-S) equations of incompressible viscous fluids and the standard k-ε turbulence model with assumptions of steady state and two dimensional conditions,a simulation of the aer...     

山区公路水毁机理与抗毁结构分析 --以凉山地区为例

以凉山地区境内的公路水毁为例,对山区公路水毁发育机理进行了分析研究,并针对本地区的地形、地貌、地质构造以及气象水文条件提出了有效的路基抗毁结构.研究表明,按不良地质现象及力学机制可将该区的公路水毁分为4类：重力剪切破坏型、泥石流诱发型、河流破坏型和地基失效.这一成因研究丰富了公路水毁学的科学内涵.,Base-watering of highways is the main wasting of highway in mountainous area. This paper analyzes base-watering of highways in mountainous area, taking base-watering of highways in Liangshan area as an example. And we suggest the effective anti-destroy structure against topography, geomorphology, tectonic and hydro-meteorology of this area. The base-watering of highways of this area can be divided into four types, i. e. slide inducing, mud-rock flow inducing, river flow inducing, and foundation losing efficacy. This classification has enriched connotation of base-watering of highways.,     

Topology optimization design and strength analysis of the hoist bracket for rescue helicopters

The hoist bracket links the rescue hoist with the helicopter cabin, and its structure design greatly affects the operation convenience and safety of the hoistman and lifeguard in the rescue process with a helicopter.This paper firstly builds the force model of the hoist and bracket, and gives five kinds of typical working conditions as the design ones of the bracket. Then this paper puts forward a design process of the hoist bracket based on the topology optimization and strength analysis with the 3D modeling and finite element analysis. This design process can make the bracket’s structure lightweight by achieving the optimal material layout under the conditions of maximizing the static stiffness or minimizing the compliance of the bracket. And this improves the dynamic performance of the helicopter, and reduces the fuel consumption and cost under the strength constraints. Finally,taking the design of the hoist bracket used in a rescue helicopter as an example, this paper illustrates the proposed model and method. The analysis results show that the mass of the hoist bracket decreases by 12.5% while the static stiffness of the hoist bracket is achieved. The optimization design results meet the strength requirements of the hoist.     

Free-Surface Wave Interaction with a Very Large Floating Structure

The free-surface wave interaction with a pontoon-type very large floating structure（VLFS） is analyzed by utilizing a modal expansion method. The modal expansion method consists of separating the hydrodynamic analysis and the dynamic response analysis of the structure. In the dynamic response analysis of the structure,the deflection of the structure with various edge conditions is decomposed into vibration modes that can be arbitrarily chosen. Free-free beam model, pinned-free beam model and fixed-free beam model are three different types of edge conditions considered in this study. For each of these beam models, the detailed mathematical formulations for calculating the corresponding eigenvalues and eigenmodes have been given, and the mathematical formulations corresponding to the beam models of pinned-free beam and fixed-free beam are novel. For the hydrodynamic analysis of the structure, the boundary value problem（BVP） equations in terms of plate modes have been established, and the BVP equations corresponding to the beam models of pinned-free beam and fixedfree beam are also novel. When these BVP equations are solved numerically, the structure deflections and the wave reflection and transmission coefficients can be obtained. These calculation results point out some findings valuable for engineering design.     

A Class of Shock Solutions for the Semilinear Singularly Perturbed Boundary Value Problem

The shock solution for the semilinear singularly perturbed two-point boundary value problem was studied. Under suitable conditions and using the theory of differential inequalities, the existence and asymptotic behavior of the solution for the original boundary value problems are discussed. The uniformly effective asymptotic expansion and estimation of solution u(x, ε) were obtained.     

Theoretical studies of active power/angle sub-matrix in power flow Jacobian for power system analysis

Properties of the active power/angle sub-matrix in the power flow Jacobian for power system analysis are studied. The sub-matrix is a dominant and irreducible matrix under very general conditions of power systems, so that it is invertible. Also the necessary conditions for its singularity are given. These theoretical results can be used to clarify the ambiguous understanding of the sub-matrix in current literature, and also provide the theoretical foundations for the applications based on reduced power flow Jacobian. Numerical simulation on the IEEE 118-bus power system is used to illustrate our results.     

Dynamic Stress and Pore Pressure Around Circular Cavity in Saturated Porous Elastic Half-space Under Harmonic Plane Dilatational Waves

Dynamic stress concentration and pore pressure concentration around an infinitely long cylindrical cavity of circular cross-section subjected to harmonic plane dilatational waves in fluid-saturated porous elastic half-space were obtained by a complex function method based on potential function and multi-polar coordinate. The steady state Biot‘s dynamic field equations of porous elastic solid with a viscous liquid were uncoupled into Helmholtz equations via given potential functions. A circular cavity with large radius is used to replace the straight boundary of the saturated porous elastic half-space. The stresses and pore pressures were obtained by using complex functions in multi-polar coordinates with certain boundary conditions of the solid matrix and the fluid matrix. The approximate solutions were compared to existing numerical solutions. Then the variations of the coefficients of dynamic stress concentration and the pore pressures concentration on boundaries of the cavity were discussed with different parameter conditions. The results of the given numerical example indicate that the method used is useful and efficient to the scattering and dynamic stress concentration of plane dilatational waves in saturated porous elastic half-space.     

Optimality Conditions for Static Programming with Generalized Convexity

IntroductionIn 1980, Hanson[1]introduced the concept ofinvexity. Many authors are interested in the fur-ther generalization. Several classes of functionswere defined for purpose of weakening the limita-tions of convexity in mathematical programming.For details, the readers are advised to consultRefs.[2~8].In Ref.[2], the necessary and sufficient con-ditions for the optimality of the primal and dualproblems were given with involving the functionssatisfying these conditions called type and typ…     

Analytical solution to steady-state temperature field of two freezing pipes with different temperatures

The existing analytical formulas to calculate the temperature field distribution of artificial frozen soil walls are all based on the conditions that the surface temperatures of all freezing pipes are equivalent. In this paper, analytical solution of steady state temperature field of two freezing pipes with different temperatures is deduced based on thermal potential superposition method. The correctness of the analytical formulas is verified by comparing the temperature field distributions of the analytical formulas and those of the numerical simulations in the same conditions. And discussions are made to analyze the influence of some parameters on temperature field distribution of this condition.     

Analysis of Thermal-Fluid-Structure Coupling and Resonance Forecast for Link Butterfly Valve Under Small Opening

When the link butterfly valve operates at a small opening degree in high temperature working conditions,it is prone to the problem that the valve is stuck,the strength is insufficient and the butterfly plate is violently vibrating.This paper shows simulation experiments of both thermal-fluid-structure coupling and resonance forecast about DN600 link butterfly valve in the working conditions of 250℃ and 0.5 MPa by ANSYS software.The medium is mixed with compressed air and flue gas.Flow field characteristics of the valve and stress deformation,modal and flow-induced vibration of butterfly plate are analyzed when the valve opening is less than 30%.The results indicate that,when the valve opening is less than 30%,fluid flow is relatively smooth in front of butterfly plate,a large number of vortexes are found behind the butterfly plate,and fluid flow is greatly chaotic in this position.The equivalent maximum stress and deformation of butterfly plate are relatively large when the valve locates in openings between 10% and 30%; the intensity of the butterfly plate is enough; the axial deformation does not impact opening and closing of the valve.The butterfly plate is likely resonant when the valve opening is less than 10%.The research of this paper provides a crucial reference for flow field characteristics of link butterfly valve,an analysis of intensity and rigidity of butterfly plate,and a resonance forecast of butterfly plate when the valve works in small opening.     

Tribological behavior of polytetrafluoroethylene coatings based on LY12 substrates in the space environment

The spacecraft space radiation environment was simulated by60 Co source. The polytetrafluoroethylene(PTFE) coatings were fabricated on LY12 substrates. And the effect of gamma(γ) irradiation on the tribological behavior of PTFE coatings under vacuum conditions was investigated. Results indicate that the radiation dose has insignificant effect on the friction coefficient of PTFE coatings, and the wear of PTFE coatings reduces with the increase of gamma dose. As the gamma dose was 100 kGy, the friction coefficient of the PTFE coatings first increased with the increase of sliding velocity and then decreased, and the wear of the PTFE coatings decreased with the increase of sliding speed. As the gamma dose was 100 kGy, the friction coefficient of the PTFE coatings first decreased with the increase of load and then increased, and the wear rate of PTFE coatings increased with the increase of load. Scanning electron microscope was utilized.     

滑坡治理过程中岩土体变形场的演绎趋势分析——以西(昌)木 (里)路新烧房滑坡为例

以西(昌)木(里)路新烧房滑坡为例 ,运用FEM数值计算方法比较详尽地分析了处于天然,开挖及治理状态下滑坡体及邻近岩土 体变形场的演绎过程,明晰了滑坡所处岩土环境的变形演绎趋势及过程,与实际情况符.该 方法对于评价、分析滑坡的稳定性态及治理效果具有重要的参考借鉴作用.,Landslide is a kind of universal and serious geologi cal disaster, which usually has characters suchas high happening frequency、high destroy force and many kinds of destroy performs. In modern highway engineering ,because highway is wider and has the higher amount of transport,it has higher demand for the stability of highways slopes.In the paper,taking the XinShao fang landslide in the Highway from Xichang to Muli as example, applying mathemat ical method of calculation and analysis, the author analyse the developing tende ncy of the rock and land mass deformation in the course of harnessing landslid e. This method is feasible and the analyzing result is prototype to some extend, which have value to analyze the slopes stability and harnessing landslide.,     

Recognizing frequency characteristics of gas sensor array

A novel method based on independent component analyzing （ICA） in frequency domain to distinguish the frequency characteristics of multi-sensor system is presented. The conditions of this type of ICA are considered and each step of resolving the problem is discussed. For a two gas sensor array, the frequency characteristics including amplitude-frequency and phase-frequency are recognized by this method, and cross-sensitivity between them is also eliminated. From the principle of similarity, the recognition mean square error is no more than 0.085.     

A multi-scale point of view on the structure-property relationships of A15 superconductors

Nb3Sn and other A15 members have been widely applied in nuclear power, nuclear magnetic resonance, and high-energy particle accelerators for their high critical current density （Jc） and upper critical field （Bc2）. There have been comprehensive and intensive studies on the applications, the fundamental lattice dynamic and electronic properties, etc., of A15 superconductors. Various reviews on the preparations, structures, and properties have already been written in the last few years. Nevertheless, on account of the large amount of existing facts and views, a coherent view on the relations between the structures and properties has not appeared to unify the facts. This article sketches a multi-scale point of view on the relations between the multi- scale structures and the corresponding properties.     

Back-analysis of the response of shield tunneling by 3D finite element method

This paper presents a numerical back-analysis of the response of a shield tunnel during construction. An important issue in the construction of shallow tunnels, especially in soft ground conditions, is the surface settlement caused by shield tunneling. The tunnel test system with 10 m length, 7 m width and 6.7 m height, which was completed in China in 2009, is a research shield tunnel system. Using shield tunneling technique known as earth pressure balance (EPB) and slurry shield method, it could be excavated in a region consisting of original soft soils, such as silty clay, and different types of underlain soft soils. Based on the test results, the real-life tunnel response can be analyzed by back-analysis technique. The back-analysis technique is adapted to the three-dimensional finite element method (FEM). Parameter analyses are calibrated to study the behavior of the multi-scale diameter tunnel under various conditions. The suggested multi-scale model results show a well agreement between the prediction and the measurement.     

Experimental Investigation of the Influence of Fuel Viscosity on the Spray Characteristics of Diesel Nozzle

This paper presented an investigation of atomization characteristics including the velocity vector field and the mean droplet sizes for different percentages of DMM-diesel blended fuels using a phase doppler anemometry (PDA) analyzer system. Based on the fuel design concept, an oxygenated fuel named dimethoxy methane (DMM), which has lower viscosity, surface tension, and boiling point, was used to blend with diesel. The experiments were carried out under atmospheric conditions on a single-hole type diesel nozzle, liquid conditions comprise a temperature of 298 K under the needle valve opening pressure of 6 MPa. The results show that the sauter mean diameter (SMD) and spray cone angle of blended fuels decrease with the increase of DMM content; the axial mean velocity in the centerline increases with the increase of DMM. However, the spray behavior of blended fuel in which DMM exceeds 75% is virtually identical to that of neat DMM. The measurement also reveals the existence of an "S" shape in the radial mean velocity variations with radial distance.