TECHNICAL AND ECONOMIC ASPECTS OF TUNNEL BLASTING ACCURACY CONTROL

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IS SEGREGATION-BY-PARTICLE-TYPE A GENERIC MECHANISM UNDERLYING FINGER FORMATION AT FRONTS OF FLOWING GRANULAR MEDIA?

The fronts of flowing granular media often manifest fingered patterns. For the case of a granular flow down an inclined plane, Pouliquen, Delour and Savage (1997) have proposed that such patterns are induced by the segregation of coarse irregularly shaped particles. Here, we consider a thin layer of a granular medium flowing within a cylinder that is rotated about its horizontal axis of symmetry. Our results show that—even when the medium is well-sieved and consists of nearly spherical grains—its leading edge may develop fingers. This suggests that, in general flow configurations, mechanisms other than segregation by particle type may be active in the instability of a straight front.     

IS SEGREGATION-BY-PARTICLE-TYPE A GENERIC MECHANISM UNDERLYING FINGER FORMATION AT FRONTS OF FLOWING GRANULAR MEDIA?

ABSTRACT

The fronts of flowing granular media often manifest fingered patterns. For the case of a granular flow down an inclined plane, Pouliquen, Delour and Savage (1997) have proposed that such patterns are induced by the segregation of coarse irregularly shaped particles. Here, we consider a thin layer of a granular medium flowing within a cylinder that is rotated about its horizontal axis of symmetry. Our results show that—even when the medium is well-sieved and consists of nearly spherical grains—its leading edge may develop fingers. This suggests that, in general flow configurations, mechanisms other than segregation by particle type may be active in the instability of a straight front.     

DEVELOPMENT OF SOFT,BAG—SHAPED TYPE Ⅱ PLASTIC SEPARATOR

<正> 铅酸蓄电池是目前使用最广泛、价格低廉、性能可靠的一种化学电源。蓄电池所用隔板的优劣,直接影响着电池的性能和使用寿命。我国目前铅酸蓄电池的生产仍然大量使用橡胶隔板,这种隔板在取代木质隔板时曾起到良好作用。但是,它的主要原料天然橡胶当前还大部分依靠进口,价格较贵、生产工艺复杂、消耗较多的能源和人力、体积大、电阻高、影响电池比能量的提高,也不能防止极群的边沿和底部短路。为了克服橡胶隔板之不足,国外相继出现了纸板浸渍隔板和微孔塑料隔板。前者价     

SOLUTION OF SOME COMBINATORIAL OPTIMIZATION PROBLEMS ENCOUNTERED IN WATER RESOURCES DEVELOPMENT†

The solution of some constrained combinatorial optimization problems encountered in the preinvestment planning of large-scale water resources systems is discussed. Mathematical structures are formulated for several problems involving the optimal selection, sequencing and timing of a set of water resources development projects which, in the aggregate, must satisfy a number of continuous time demand projections at every point in a finite planning horizon. An overview of four different solution techniques is also given. Specifically, myopic decision rules, integer programming formulations, and both implicit enumeration by branch-and-bound algorithms and dynamic programming algorithms are discussed. A computational comparison of these solution techniques on a number of real-world water resources problems of various sizes is also reported.     

A STUDY ON THE ULTIMATE FRACTURE STRENGTH AND FRACTURE BEHAVIOR OF POLYMERIC MATERIALS——Ⅱ.A KINETIC MODEL THEORY OF CREEP TENSILE STRENGTH

本文对当前蠕变持久强度的表征进行了系统总结,指出了它是高分子材料的可形变性、分子链应力集中情况和应力集中链断链滑移动力学三者统一的体现。基于这种破坏概念,推导出一种能表征半晶态、玻璃态和弹性体等聚合物的蠕变持久强度动力学模型理论和一般化断裂状态方程。当该方程引入一、二级近似条件后,该式就分别还原为准脆性状态下粘弹性蠕变断裂方程,受迫高弹性状态下蠕变断裂方程和高弹性状态下蠕变断裂方程。     

PHYSIOLOGICAL TESTING OF CARBON NANOTUBES: ARE THEY ASBESTOS-LIKE?

To determine whether carbon nanotubes can induce any significant health hazards we applied methods routinely used in the pathophysiological testing of asbestos-induced disease to show that the soot with a high content of CNTs does not induce any abnormalities of pulmonary function or measurable inflammation in guinea pigs treated with carbon nanotubes.     

PHYSIOLOGICAL TESTING OF CARBON NANOTUBES: ARE THEY ASBESTOS-LIKE?

To determine whether carbon nanotubes can induce any significant health hazards we applied methods routinely used in the pathophysiological testing of asbestos-induced disease to show that the soot with a high content of CNTs does not induce any abnormalities of pulmonary function or measurable inflammation in guinea pigs treated with carbon nanotubes.