深孔加工钻头排屑研究及CAD设计

深入分析了深孔加工用的钻头对排屑的需求,通过受力分析,给出了钻屑的产生过程以及钻屑对钻头工作的影响.根据钻头的工作机制,结合非自由切削的基本特征,运用最小能量的原理进行了深孔钻头的设计.并对所设计的钻头进行了排屑向量的计算,得出了排屑向量关系式.最后再对其进行排屑干涉和排屑协调分析,得出了钻头主刃部分的非自由度系数设计步骤.     

An axisymmetric contact model of ultra high molecular weight polyethylene cups against metallic femoral heads for artificial hip joint replacements.

Contact mechanics of ultra high molecular weight polyethylene (UHMWPE) cups against metallic femoral heads for artificial hip joints is considered in this study. Both the experimental measurement of the contact area and the finite element prediction of the contact radius, maximum contact pressure and maximum Von Mises stress have been carried out for a wide range of contemporary artificial hip joints. Good agreement of the contact radius has been found between the experimental measurements and the finite element predictions based upon an elastic modulus of 1000 MPa and a Poisson's ratio of 0.4 for UHMWPE material under various loads up to 2.5 kN. It has been shown that the half contact angle for all the cup/head combinations considered in this study is between 40 degrees and 50 degrees under a load of 2.5 kN. The importance of this result has been discussed with respect to the anatomical position of the cup when placed in the body and the selection of a simple wear-screening test for artificial hip joints. The predicted contact radius and maximum contact pressure from the finite element model have also been compared with a simple elasticity analysis. It has been shown that the difference in the predicted contact radius between the two methods is reduced for more conforming contacts between the femoral head and the acetabular cup and smaller UHMWPE cup thickness. However, good agreement of the predicted maximum contact pressure has been found for all the combinations of the femoral head and the acetabular cup considered in this study. The importance of contact mechanics on the clinical performance of artificial hip joint replacements has also been discussed.     

计算机辅助概念设计研究现状和发展趋势

指出产品概念设计包含设计功能、原理、形状、布局和结构设计等内容,阐明计算机辅助概念设计的内涵。从工程设计、工业设计、人工智能和新技术４个角度探讨目前国内外该领域的研究发展现状,结合现代产品设计模式的发展方向,指出ＣＡＣＤ以设计创新和建模技术为核心的六大关键技术,以及ＣＡＣＤ的发展趋势。     

Co-training机器学习方法在中文组块识别中的应用

采用半指导机器学习方法co2training 实现中文组块识别。首先明确了中文组块的定义,co-training 算法的形式化定义。文中提出了基于一致性的co-training 选取方法将增益的隐马尔可夫模型(Transductive HMM) 和基于转换规则的分类器(fnTBL) 组合成一个分类体系,并与自我训练方法进行了比较,在小规模汉语树库语料和大规模未带标汉语语料上进行中文组块识别,实验结果要比单纯使用小规模的树库语料有所提高,F 值分别达到了85134 %和83141 % ,分别提高了2113 %和7121 %。     

Beam dynamics,RF measurement,and commissioning of a CW heavy ion IH-DTL

A 53.667 MHz CW(continuous-wave) heavy ion IH-DTL has been designed for the SSC-LINAC injector of HIRFL-CSR(Heavy Ions Research Facility at Lanzhou-Cooling Storage Ring). It accelerates ions with maximum mass-to-charge ratio of 7.0 from 143 to 295 ke V/u. Low-power RF measurement of the IH-DTL1 has been taken to investigate the RF performance and the quality of the electric field distribution on the beam axis.The measured Q_0 value and the shunt impedance are 10,400 and 198 MX/m, respectively. The electric field distributions on and around the beam axis were evaluated and compared with the design value. By a new approach,the dipole field component is also estimated. The beam dynamics simulation using measured field distribution was presented in this paper. Based on the dynamics analysis in both transverse and longitudinal phase space, the field distribution can meet the design requirement. Finally, the RF conditioning and very first beam commissioning on the IH-DTL1 were finished. The beam test results agree well with the simulation results; what's more, the property of the variable output beam energy about the separated functions DTL was verified.     

平塘县城2007年暴雨洪水分析

2007年7月25～26日,六洞河流域普降暴雨,六洞河水位全线上涨,26日六洞河控制站平湖站水位超历史洪水位,达到100年一遇的特大洪水,致使平塘县整个县城被淹,洪涝损失严重.本文对2007·7·26暴雨的气象成因及洪水形成过程进行分析,阐述本次暴雨、洪水的特点及变化规律,为城市防洪、工程设计提供参考依据.     

深孔梯段爆破在三门县海滨山体开采施工中的应用

在三门县海滨新城山体土石方工程时,由于工期较短、爆破强度大而采用深孔梯段爆破。根据实践经验,简要介绍在这种情况下所采取的爆破方法及参数。图3幅,表4个。