截割厚度与截线距对镐型截齿破岩力学参数的影响

基于对一种砂岩的直线截割试验,研究截割厚度和截线距对镐型截齿破岩力学参数的影响。单因素回归表明:截割力、法向力与截割厚度成正比,线性拟合和幂函数拟合均能很好地描述它们之间的统计学关系;随着截割厚度的增加,法向力截割力比值呈线性减小;随着截线距的增加,截割力和法向力呈线性增加,法向力截割力比值呈幂函数减小。载荷波动性系数随着截线距与截割厚度比值的增大呈线性减小。多元线性回归表明:截割力、法向力与截割厚度和截线距之间有极强的统计学关系;载荷波动性系数与截割厚度及截线距之间存在显著的统计学关系,且与截割厚度成正比,与截线距成反比。对比发现,Evans的理论模型较Roxborouth等、Goktan的改进模型对截割力有更好的预测性能。     

Finding minimal cut sets in a fault tree

This paper presents a new method for identification of minimal cut sets in a fault tree. The (non-minimal) cut sets are found by a modification of the well-known MOCUS algorithm. These cut sets are stored in a virtual tree structure which requires far less core space than the MOCUS cut set matrix. The minimal cut sets are found by traversing this virtual tree a number of times. In the first cycle, all cut sets of order one are identified. In the next cycle, all cut sets of order two are identified and compared with the cut sets of order one to exclude non-minimal stes. This procedure is continued until all minimal cut sets are identified. The procedure is very fast. Compared to the standard MOCUS program the computer time is reduced by at least a factor of ten.     

钢筋砼烟囱爆破切口形状对切角大小和切口高度的影响

根据钢筋混凝土烟囱失稳倾倒原理,通过力学分析,建立了描述钢筋混凝土烟囱的切口形状与切角大小、切口高度之关系的数学模型。结合工程实例,详细分析了切口形状对切角大小和切口高度的影响。研究表明,在相同切角大小时,组合形切口具有最小的切口高度;同时表明,采用本文的模型所确定的最小切口高度要比实际工程中采用的偏小。     

钢筋砼烟囱爆破切口形状对切角大小和切口高度的影响

根据钢筋混凝土烟囱失稳倾倒原理,通过力学分析,建立了描述钢筋混凝土烟囱的切口形状与切角大小、切口高度之关系的数学模型。结合工程实例,详细分析了切口形状对切角大小和切口高度的影响。研究表明,在相同切角大小时,组合形切口具有最小的切口高度;同时表明,采用本文的模型所确定的最小切口高度要比实际工程中采用的偏小。     

砖烟囱爆破切口形状对切角和切口高度的影响分析

针对目前爆破理论比较落后,烟囱爆破拆除时仅仅靠经验确定爆破切角大小和切口高度的现状,从砖烟囱的爆破切口形状出发,建立了确定砖烟囱选用不同切口形状时的切角大小和切口高度的数学模型,分析了切口形状对爆破切角大小和切口高度的影响,并结合工程实例对建立的数学模型进行了分析和讨论.     

竖向切缝在高大冷却塔拆除爆破中的作用

介绍了广东省茂名市某热电厂1座123.2m高冷却塔的爆破拆除。通过竖向切缝,用以减弱塔身的整体刚性,加大其失稳条件,促使塔体倾倒和加强解体破碎效果。对冷却塔爆破切口和竖向切缝进行了爆破设计,对冷却塔的倒塌过程进行了数值模拟与结果分析。工程实践表明,切口上部的竖向切缝对冷却塔的加速倒塌、减小振动和控制爆堆范围等方面都有一定的作用。本工程提供的经验可供类似工程参考。     

SAPHIRE ‘Recover Cut Sets’ editor: a technique for automating the manipulation of PRA cut sets

The accident sequence cut sets generated for a probabilistic risk analysis generally require some manipulation to account for special modelling concerns. This paper presents a method of efficiently manipulating cut sets, specifically for the modelling concerns of (a) post-accident operator recovery actions, (b) common cause failure modelling, and (c) removal of mutually exclusive events. The method presented consists of logic rules that define a cut set search criteria and changes to be applied to the cut sets meeting the search criteria. While this method of cut set manipulation is demonstrated using the ‘Recover Cut Sets’ editor in the SAPHIRE risk assessment computer code, it is proposed that this methodology could become a standard method for cut set manipulation.     

小断面岩石巷道掏槽爆破参数优化实验

针对小断面岩石巷道掏槽爆破效率低下的技术难题,依据掏槽爆破形成槽腔为后续炮孔提供自由面。通过分析施工过程中掏槽爆破存在的问题及其影响因素,采取了控制单一变量的方法,制定9组实验方案,同时配合规范的施工方法对掏槽爆破参数进行优化,从而获得最优的掏槽爆破参数组合。通过对实验数据的比较分析,优化的掏槽爆破参数使巷道掘进的炮孔利用率提高了20%,掘进综合成本节省了27%。     

Effects of manufacturing defects on the mechanical properties of carbon fibre reinforced polyethersulphone laminates

The effects of defects on the mechanical properties of carbon fibre reinforced polyethersulphone laminates have been measured. The defects studied were cut fibre plies, omission of polymer films and local delamination produced by the inclusion of foreign matter. Of these it was found that only cut plies had a significant detrimental effect on the strength of a laminate. For specimens with two cut plies, the failure stress, tensile, flexural and compressive in the remaining continuous plies was the same as in the defect-free material, provided that the cut plies were widely separated. However the failure stresses were 15–18% lower in the continuous plies in the specimens containing two cut plies which were more closely spaced and in specimens containing four cut plies.     

小断面岩石巷道掏槽爆破参数优化实验

针对小断面岩石巷道掏槽爆破效率低下的技术难题,依据掏槽爆破形成槽腔为后续炮孔提供自由面。通过分析施工过程中掏槽爆破存在的问题及其影响因素,采取了控制单一变量的方法,制定9组实验方案,同时配合规范的施工方法对掏槽爆破参数进行优化,从而获得最优的掏槽爆破参数组合。通过对实验数据的比较分析,优化的掏槽爆破参数使巷道掘进的炮孔利用率提高了20%,掘进综合成本节省了27%。     

Cartesian Grid Method with Cut Cell in the Mold Filling Simulation

In this paper, a Cartesian grid method with cut cell has been developed to simulate mold filling of casting process. Cut cells at the cast-mold interface are generated on the Cartesian grid. With the boundary cut cells, a special treatment is necessary. That is Cartesian grid method with cut cell. A simple shape was tested and the cut cell method was compared with the traditional one on Cartesian grids. And, a developed method was applied to the real casting product simulation. Cartesian grid system causes momentum loss and unsound fluid flow patterns because of inaccurate generation of meshes. These problems have been improved by using cut cell method.     

卷烟机剔除梗签物中烟丝在线分离回用装置的设计与应用

为解决现有卷烟机剔除梗签物中烟丝集中收集方式存在的烟丝降级使用问题,设计了烟丝连续在线回用装置.烟丝在线分离回用装置设在卷烟机剔梗装置后身,通过塔式分离器实现烟梗、烟丝的一次分离,再利用旋风分离器实现烟丝、烟末的二次分离.分离出的烟丝直接落入卷烟机的回烟丝振槽内,烟丝水分和香气散失少.应用表明,该装置安装方便,适用范围广,可用于各种机型的卷烟机,能够在线回收和利用卷烟机剔除梗签物中85%以上的烟丝,显著降低卷烟机的烟丝消耗,提高企业经济效益.     

含空孔直眼掏槽爆破效果分析模型

直眼掏槽是隧道掘进深孔爆破中的关键技术 ,炮孔深度对掏槽爆破效果有重要影响。本研究通过建立槽腔内抛体运动的二相流力学模型 ,揭示了炮孔深度影响掏槽效果的物理本质 ,阐述了炮孔深度对掏槽效果的影响规律 ;为含空孔直眼掏槽爆破参数设计提供了依据。理论分析结果与工程实践相吻合。     

Magnetic-field calculation for a high-temperature superconducting cryogenic current comparator

The problem considered in this paper arises in the design of a high-temperature superconducting cryogenic current comparator (CCC). The CCC consists of two currents flowing in opposite directions inside a toroidal superconducting shield. The shield has a radial cut, necessary for the measurement of the current ratio, but causing an error in the obtained ratio. The problem of interest is the dependence of the error on the geometric parameters of the device: the major and minor radii of the shield, the cut width, the material thickness, and the location of the currents. In the first part of the paper, a toroidal shield with an infinitesimal cut is considered and analytic expressions are derived for the magnetic field and the surface-current distribution. In the second part, a cut of finite width is introduced. Since all the perturbing currents are present in the narrow region around the cut, a shield of cylindrical shape is assumed. Expressions are derived for the flux through the cut and the magnetic field around the cut. Analytical results are in good agreement with the numerical results obtained by a finite-element method. In the final part, the expression for the ratio error is derived, which shows that in order to minimize the error, currents should be concentrated around the shield axis, the major radius of the shield should be maximized and the bore radius minimized. The error depends logarithmically on the cut width.     

小爆破切口在框架结构楼房定向爆破拆除中的应用

在爆破拆除一座五层的框架结构楼房时 ,采用了小爆破切口控制楼体倾倒时的后坐。文中对采用小爆破切口时楼体的倾倒过程进行了简要分析 ,并对小爆破切口与合理延时间隔相配合的必要性进行了详细阐述。理论分析及工程实践表明 ,小爆破切口技术适用于楼高H和跨度L之比 (H/L)大于 1 5的框架结构楼房的爆破拆除 ,切口高度一般不宜大于 2m。在确定爆破切口时 ,要综合考虑爆破施工环境以及楼体高度H、跨度L、底层高h和梁柱节点强度之间的关系     

螺旋天线原油含水率测量仪的误差分析与校准

天线是射频法原油含水率测量仪的关键部件.分析采用平行天线和螺旋天线的含水率测量仪在检测原理上的差异,使用研制的螺旋天线原油含水率测量仪进行含水率重复性实验,实验数据分析表明,含水率在40％～80％时,由于原油发生相变,在该区间,含水率测量仪的线性度变差.针对上述问题设计含水率测量误差校准方法及流程,采用分段线性插值法进...     

Algorithm for finding minimal cut sets in a fault tree

This paper presents several algorithms that have been used in a computer code for fault-tree analysing by the minimal cut sets method. The main algorithm is the more efficient version of the new CARA algorithm, which finds minimal cut sets with an auxiliary dynamical structure. The presented algorithm for finding the minimal cut sets enables one to do so by defined requirements — according to the order of minimal cut sets, or to the number of minimal cut sets, or both. This algorithm is irom three to six times faster when compared with the primary version of the CARA algorithm.     

Laser cutting of fibre-reinforced polyesters

Composites of aramid, graphite and glass cloth-reinforced polyester have been cut by a laser and the morphology of the cut surfaces examined by scanning electron microscopy. The results are examined using a numerical thermal model and a mechanism for the laser-induced thermal changes observed in the composites is proposed. The thermal properties of the fibres and matrix are the principal factors which affect cutting performance. For the range of experimental parameters used in this study, the quality of the cut surfaces obtained depends on the type of composite being cut.     

Effect of Oxygen in Laser Cutting Process

Laser cutting has become an acceptable process in automated sheet metal industry. Efficiency and quality can be maintained with laser cutting. However, oxygen assisted cutting may influence the metallurgical structure of the cut edges. Consequently, in the present study, oxygen diffusion into solid substrate in the vicinity of the cut edge is considered together with the metallurgical changes at the cut surface. To achieve this, an experiment is designed and conducted to cut stainless steel workpiece with a CO₂ laser beam at different oxygen pressures. To determine the elemental distribution in the vicinity of the cut edges, Micro-Particle Induced x-Ray Emission (μ-PIXE), Nuclear Reaction Analysis (μ-NRA) and EDS are carried out. It is found that no oxygen peak is evident at the cut edge and Cr, Al and Si are enriched locally.     

云锡1360基础平台岩巷掘进掏槽爆破参数优化

针对云锡1360基础平台岩巷掘进循环进尺小、炮孔利用率低的问题,在优化掘进爆破参数的基础上,通过现场试验对比三级楔形与中心桶形混合掏槽、二级九孔与中心桶形混合掏槽、三级双空孔菱形掏槽、二级六棱柱与中心三角柱形混合掏槽的爆破效果,以掘进进尺、掏槽孔利用率,掏槽孔残孔深度、平巷轮廓成型等指标作为评价爆破参数优劣的标准。试验结果表明,在致密的大理岩和破碎且带有泥质夹层的岩石中,分别采用三级楔形与中心桶形混合掏槽(孔深3.4m)和三级双空孔菱形掏槽(孔深2.7m)能够取得良好的爆破效果。