Shear behavior of coarse aggregates for dam construction under varied stress paths

Coarse aggregates are the major infrastructure materials of concrete-faced rock-fill dams and are consolidated to bear upper and lateral loads. With the increase of dam height, high confining pressure and complex stress states complicate the shear behavfor of coarse aggregates, and thus impede the high dam＇s proper construction, operation and maintenance. An experimental program was conducted to study the shear behavior of dam coarse aggregates using a large-scale triaxial shear apparatus. Through triaxial shear tests, the strain-stress behaviors of aggregates were observed under constant confining pressures： 300 kPa, 600 kPa 900 kPa and 1200 kPa. Shear strengths and aggregate breakage characteristics associated with high pressure shear processes are discussed. Stress path tests were conducted to observe and analyze coarse aggregate response under complex stress states. In triaxial shear tests, it was found that peak deviator stresses increase along with confining pressures, whereas the peak principal stress ratios decrease as confining pressures increase With increasing confining pressures, the dilation decreases and the contraction eventually prevails. Initial strength parameters （Poisson＇s ratio and tangent modulus） show a nonlinear relationship with confining pressures when the pressures are relatively low. Shear strength parameters decrease with increasing confining pressures. The failure envelope lines are convex curves, with clear curvature under low confining pressures. Under moderate confining pressures, dilation is offset by particle breakage. Under high confining pressures, dilation disappears.     

厂房尾水薄壁堰三维非线性有限元分析

通过对厂房尾水薄壁堰-基岩-河水（水压力）联合作用的三维有限元分析进一步了解薄壁堰结构的位移、应力分布，堆石体位移、应力应变分布情况，岩体应力状态及应力分布等，为门机浇筑设计方案及薄壁堰加固等处理提供科学的依据和数据。     

A theory of return‐seeking firms

We introduce a theory of return‐seeking firms to study the differences between this and profit‐maximising models. A return‐seeking objective takes into account the opportunity cost of each additional resource input to a firm's production as being a potential capital input choice in an alternative project. We find that firm supply curves cease to exist in perfectly competitive markets, that supply curves may slope up as well as down, that economies of scale are necessary for any production to occur and that firms always produce on a decreasing portion of their cost curve.     

椭圆曲线密码体制的应用及研究

介绍了椭圆曲线密码体制的基本应用,分析了ECC优于其他公钥系统的具体优点及其数学原理。针对椭圆曲线的研究热点,归纳出椭圆曲线选取原则以及椭圆曲线快速算法的基本原理。深入研究了椭圆曲线上双线性映射,构建了其在电子商务中应用模型,证明了该性质对ECC进一步发展的促进作用。     

建立不锈钢系列的B元素在线检验项目

本文介绍了利用ARL4460型直读光谱仪检测不锈钢中硼的含量。硼对钢材的影响很微妙,钢中加入微量的硼可显著提高钢的淬透性;而当钢中硼的含量过高时则会在材料的晶界处徧聚,从而造成材料的沿晶脆断。     

Discount curve construction with tension splines

Polynomial splines are popular in the estimation of discount bond term structures, but suffer from well-documented problems with spurious inflection points, excessive convexity, and lack of locality in the effects of input price perturbations. In this paper, we address these issues through the use of shape-preserving splines from the class of generalized tension splines. Our primary focus is on the classical hyperbolic tension spline which we derive non-parametrically from a penalized least squares criterion, but extensions to generalized tension splines—such as rational splines and exponential splines—are also covered. Our methodology allows both for best-fitting of noisy bonds and for the construction of an exact interpolatory term structure to a set of liquid instruments. We work with a local tension B-spline basis and support both fully non-parametric and user-imposed knot location strategies.     

洛川黄土的动变形和强度特紧性

本文对陕北洛川标准剖面原状黄土的动变形强度特性进行了系统的研究，得出了一系列规律性的成果．对动本构特性，动强度特性以及动变形特性等方面的问题也进行了试验研究     

危险滑带转移模式下的岩质边坡稳定性评价

在以往的岩质边坡稳定分析中,均是对单一的危险滑带进行研究,而忽略了其他次危险滑带在某一状态下变为主要危险滑带的可能。鉴于此,以牙根水电站坝址岩质边坡为例,结合该岩质边坡地质情况,建立了带有可能的滑带群边坡模型,采用大型有限元分析软件,对不同蓄水位和不同工况下每条可能滑带进行边坡稳定性计算,研究其内部滑带转移模式。结果表明：边坡的稳定性并不是只受单一的滑带控制,当外界条件发生变化时,边坡最危险滑带发生了转移。如按单一的危险滑带对边坡稳定性进行评价,往往会失真,进而导致边坡加固措施的盲目性。