Same impact momentum causes different degrees of spinal cord injury

The weight-drop impact is widely used in making animal model of spinal cord injury （SCI）. But there has not yet been an appropriate unit for the quantification of the impact. In this study, we compared the degrees of the spinal cord injury caused by weight-drop impact with the same momentum but different combinations of drop weight and drop height, in order to test whether ＂momentum＂ is capable of being the unit for the quantification of weight- drop impact. Thirty adult rats were randomly allocated to three groups and were injured with 5 g-10 cm （group A）, 10g-2.5 cm （group B） and 15 g-l.ll cm （group C） impacts with the same momentum to the spinal cord, respectively. Open-field locomotor function was evaluated using the Basso-Beattie-Bresnahan （BBB） locomotor rat- ing scale. The percentage of spared tissue area （STA） at the epicenter, and 500, 1000 and 1500 gm from the epicenter was calculated using serial sections stained by hematoxylin and eosin. As a result, the behavioral recovery （BBB scores） and the STA percentage were similar in group B and group C. However, the BBB score in group A was significantly lower than that in groups B and C at the same time point post injury. The STA percentage was signifi- cantly less and the lesion/cavity length was significantlygreater in group A than in groups B and C. These suggested that the 5 g-10 cm weight-drop impact, compared with the other two impacts with different weights and heights, caused a greater damage of the spinal cord when the momentum was the same. So, these impacts with the same momentum but different weights and drop heights cause different degrees of spinal cord injury. Momentum alone is inadequate to be the unit for the qualification of weight- drop impact and to be used to predict the extent of injury.     

岩石宏观裂纹分叉的加载率效应

利用扫描电镜和光学显微镜，对静态和冲击加载条件下断裂的辉长岩试件进行了剖面观察与分析。结果发现，静态加载时断裂面的剖面上几乎看不到宏观裂纹分叉现象；但在动态加载时，普遍发现剖面上有宏观裂纹分叉现象。随着加载率提高，分叉 数量及其总长度也随之增加。基于以上实验结果，初步讨论了岩石动态断裂机理。     

论区域经济地理基本特征的描述系统——以中国经济地理为例

一段时间以来区域经济地理研究艰难地由旧思维向新思维转换,很多学者都致力于探索描述区域经济地理基本特征的思维系统与结构.提出了区域经济地理的研究对象、核心问题和集中表现是"区域发展与运行",并对这一全新概念进行了阐述与分析;随后对区域经济地理的"基本特征"进行了系统归纳,认为可以通过区域条件影响的评价、区域发展水平、区域发展过程、区域经济结构、区域差异、区域运行战略与对策等6个要素较全面地说明一个区域的经济地理基本特征,具体说明了这6维要素为何使用、在何处使用以及如何使用;同时还解释了区域经济地理基本特征描述系统的灵活应用问题.我国是一个经济地理特征十分复杂的国家,有效完成区域经济地理特征描述思维的转换,突破传统描述思维的束缚、建立新的描述思维系统,具有理论与应用的重要意义.     

棱柱杆侵彻岩土的动力学分析

首先建立了计算撞击力的刚体-流体撞击模型和计算靶体变形的法向膨胀理论。在此基础上,根据动量定理和功能守恒定律,建立了棱柱杆侵彻岩土时的动力学模型。采用龙格-库塔方法对这些非线性动力学方程进行数值求解。由这些非线性动力学方程的数值解,确定了撞击力和侵入位移,进而得到几何参数对撞击力、侵彻位移的影响曲线。通过分析棱柱杆的几何参数对撞击力和侵入位移的影响,给出了棱柱杆主要几何参数的合理范围。     

Solid-particle erosion behavior of cast alloys used in the mining industry

The erosive-wear response of five commercial ferrous-based cast alloys used for crushing was examined in this study. The micro-structures of the alloys were modified to elucidate the effect of microstructural features on wear. Erosion tests were conducted using alumi-num oxide particles (90–125 μm) at 70 m/s and a normal impact angle (90°). The worn surfaces were characterized by scanning electron mi-croscopy and 3D non-contact laser profilometry. It is found that (i) a pearlitic structure exhibiting a greater plastic deformation than both bainitic and martensitic structures shows the greatest resistance to erosive wear at normal impact and (ii) the fracture characteristics of car-bide and graphite particles plays an important role in determining the erosion wear behavior of the cast alloy matrices.     

非静压成形过程的刚塑性有限元模拟

本文针对非稳态高速成形过程，讨论了冲击载荷和体积力的计算问题，给出了一种全面考虑冲击载荷与体积力作用的刚塑性有限元方程。并且将此分析成功地应用于锻造过程中上下模具金属填充性能的比较研究。     

硬质合金端铣刀的铣削冲击

用较简单和实用的角度投影法分析了切削时的机械冲击,得出了切削时的接触类型和切入过程的接触顺序以及刀齿切入时的最佳状态切入角E_1和切出角E_2的变化,改善了刀齿的受力状态,提高硬质合金端铣刀的使用寿命。     

自动武器中机构撞击传动

该文将自动武器中的机构分解成机构单元,研究其撞击传动规律。文中分析研究了简单机构和复杂机构的撞击传动,导出了一般的二自由度机构系统撞击传动过程的线性代数方程组。该文为分析自动武器中机构撞击传动问题编制通用计算程序提供了理论依据。     

鲅鱼圈开发区污水海洋处置工程环境影响分析

分析了鲸鱼圈开发区污水海洋处置工程对海域可能造成的环境影响。