气控盘式辅助刹车在车载钻机中的应用分析

在对比分析了传统辅助水刹车与气控盘式辅助刹车的特性后,重点对气控盘式辅助刹车进行了数学分析,得到了该辅助刹车的制动扭矩取决于施加的气体压力,与钻具质量无关,冷却液的流量应同钻柱质量保持正比关系,可精确控制下钻速度并易于实现自动送钻功能。得出了气控盘式辅助刹车更适用于车载钻机的结论。     

Three-dimensional stability analysis of the dam foundation at Baise

It is usually difficult to determine the actual safety factors of rock masses in an ordinary two-dimensional stability analysis if the safety factors of the different cross sections in the rock mass vary significantly. In addition to the actual slope, arch dam abutment, and the actual foundation of a high building, another example is that the different cross sections of the foundation in the monolith of a gravity dam vary significantly, just like the condition at the overflow dam in the Baise project. A three-dimensional stability analysis method based on the upper-bound theorem was employed to solve this problem. The parameters used in the analysis were obtained from geomechanics tests, as well as continuity simulations of the randomly distributed joints. Two failure patterns against sliding are analyzed. One pattern is the foundation slide along deep-seated planes which were determined by calculations. The other pattern is the foundation slide along the planes across the bottom of the high steps in the foundation pit. The results indicate that a special overflow dam monolith can be considered to be safe in case of considering the three dimensional effect. However, a key wall with a depth of 5m must be constructed at the upper side of this monolith in order to ensure the safety of the foundation. Translated from Chinese Journal of Rock Mechanics and Engineering, 2006, 25(3): 533–538 [译自: 岩土力学与工程学报]     

陕西省引红济石调水工程1#支洞塌方原因分析及对策

塌方是隧洞施工过程中经常遇到的难题,本文针对引红济石工程1#支洞在施工过程中出现的两次塌方原因进行分析,总结出隧洞施工过程中避免塌方的主要方法和策略,具有普遍的借鉴意义。     

A rule-based approach for robust clump splitting

This paper presents a robust rule-based approach for the splitting of binary clumps that are formed by objects of diverse shapes and sizes. First, the deepest boundary pixels, i.e., the concavity pixels in a clump, are detected using a fast and accurate scheme. Next, concavity-based rules are applied to generate the candidate split lines that join pairs of concavity pixels. A figure of merit is used to determine the best split line from the set of candidate lines. Experimental results show that the proposed approach is robust and accurate.     

Stability of large-scale coal-fired MHD channels

Stability of large-scale coal-fired MHD channels is studied by (1) linearized stability analysis, and (2) time-dependent 1-D analysis. The channel length is 15 m with 600 electrode pairs, and the output power ranges from 220.6 MW through 258.7 MW. Linearized stability analyses show that the Faraday channels operated with fixed loading resistance are stable, whereas the two waves of u and u–a (u, a: gas and sound velocity) become unstable in the Faraday channel with fixed loading factor. Two waves of u and u–a are unstable in the diagonal channel with fixed loading current and the u + a wave becomes unstable in the diagonal channel with fixed electrode current. Time-dependent one-dimensional analyses indicate that the Faraday channels with fixed load resistance are smooth without growth of fluctuation. The diagonal channels with fixed electrode current are smooth with no fluctuation, though the linear theory indicates that the u + a wave is unstable. The diagonal channel with fixed load current suffers large disturbance along the latter half of the channel, being consistent with the linearized analysis which indicates that the u - a and u waves are unstable.     

The use of the stable isotope 44Ca in studies of calcium incorporation into dentin

The incorporation into rat incisor dentin of two calcium isotopes, the stable ⁴⁴Ca and the radioactive ⁴⁵Ca, was studied using secondary ion mass spectrometry (SIMS) stepscanning and imaging, and autoradiography, respectively. The results demonstrated a time-dependent incorporation of the calcium isotopes into the mineral phase of dentin. With the SIMS step-scanning, detecting ⁴⁴Ca, the ion yield was high in the odontoblasts 2 min after intravenous injection. After 10 min a marked increase in signal intensity was found at the dentin mineralization front. This result was consistent with those obtained by ⁴⁵Ca autoradiography; a peak of incorporation occurred 10 min after injection of the isotope. Likewise, localization of ⁴⁴Ca to the mineralization front could be demonstrated 10 min after injection by SIMS imaging. In images obtained at earlier intervals, no such increase in ion yield could be detected. The results show that the nonradioactive, stable isotope ⁴⁴Ca can be used as a marker for biomineralization in a similar way to radioactive ⁴⁵Ca.     

万安水利枢纽底孔坝段中隔墙流激振动响应分析

 研究了万安水利枢纽底孔坝段中隔墙在水流脉动壁压作用下的结构随机振动问题，进行了一种泄流工况下的隔墙结构流激振动响应统计量的理论计算，模拟计算了隔墙－水流－基础耦合系统固有频率对流激振动响应的影响，并对水流脉动壁压随机荷载作用下的结构动力可靠度进行了理论分析。     

Exact solution of elasto-plastic stresses in a metal-matrix composite beam of arbitrary orientation subjected to transverse loads

An analytical elasto-plastic stress analysis is presented for a metal-matrix composite beam of arbitrary orientation subjected to a single transverse force applied to the free end of the beam and a uniformly distributed load. The material is assumed to be perfectly plastic in the elasto-plastic solution. A composite consisting of stainless-steel-reinforced aluminum was produced for this work. Sample problems are given for various orientation angles. Elastic, elastoplastic and residual normal and shear stresses are calculated. The location of the elasto-plastic boundary of the beam is obtained according to the x coordinates of the beam.     

容错磁盘阵列的性能模型

本文以排队论为工具，建立了容错磁盘阵列的Ｍ／Ｇ／１排队模型，并在此基础上分析了ＲＡＩＤ的平均响应时间，稳定数据传输率等重要性能指标；比较了同步和异步ＲＡＩＤ的性能差异，最后提出了以吞吐率作为衡量ＲＡＩＤ性能的综合指标，并给出了确定最大吞吐率的定量。     

Characterization of CuInS2 thin films for solar cells prepared by spray pyrolysis

We have made a study of the chemical composition, the electrical, the optical and the structural properties of polycrystalline CuInS₂ thin films prepared by spray pyrolysis to be used for thin film solar cells. These films were deposited starting from aqueous solutions with different chemical compositions ([Cu]/[In] and [S]/[Cu] ratios) and at different substrate temperatures. In all cases, the material is p-type with grains preferentially oriented in the (112) direction of the sphalerite structure. The electro-optical properties show a very strong dependence on the [Cu]/[In] ratio in the solution. Films with copper excess have smaller resistivity and better crystallinity than those which are stoichiometric or have indium excess. The results obtained in this work show the possibility of having CuInS₂ thin films with a wide range of resistivity, a fact that could be important for making solar cells based on this material.