An automatically‐tuned sorting library

We present ATSL, an automatically‐tuned sorting library. ATSL generates a sorting routine optimized to the target machine for a specific data type. ATSL finds a high‐performance sorting routine by searching an algorithmic space that we have defined. The search space includes basic sorting algorithms and automatically‐generated compositions of sorting algorithms. Performance measurements are used both for ranking candidate algorithms and for characterizing the behavior of candidates in specific settings (e.g. ranges of input sizes). These characterizations allow ATSL to generate hybrid algorithms that intelligently exploit the strengths of particular algorithms, such as high speed at specific input‐size ranges. Many sorting algorithms can be tuned using numeric parameters and ATSL searches these parameter spaces to find values that yield high performance on the target machine. The building blocks from which ATSL synthesizes sorting algorithms include adaptations of many of the most effective hand‐tuned sorting routines, including several that are tuned for cache efficiency. An extensive experimental evaluation shows that ATSL generates high‐performance codes that are well tuned for the target machine and data type. The experiments were conducted on six different machines, of several architectures, and with three different compilers. The algorithms that are generated are fast; in particular, they beat the hand‐tuned building blocks and the compiler's C++ built‐in sorting routine. The algorithms that ATSL generates on different machines and using different compilers are different from each other. Copyright © 2007 John Wiley & Sons, Ltd.     

X型矩形钢管相贯节点平面内抗弯刚度研究

在分析平面内弯矩作用下节点有限元模型的局部变形特征和借鉴前人将节点强度计算的塑性铰线模型改进用来建立T型节点轴向刚度计算模型的基础上,建立用于X型矩形钢管相贯节点平面内抗弯刚度计算的6杆系模型,并利用最小势能原理确定6杆系模型中每根杆的跨度和截面宽度,在分析确定了每根杆的边界条件后推导出节点平面内抗弯刚度理论公式.通过对节点板壳有限元模型计算所得数据进行单参数分析,研究各参数对节点抗弯刚度的影响,在此基础上修正节点刚度理论公式,并利用多元回归分析技术,最终建立可用于工程计算的节点平面内抗弯初始刚度参数化公式,并通过有限元计算结果来校验其合理性.     

Functional Possibilities of SM-401 Magnetic Structuroscope

The possibilities of nondestructive testing the quality of product hardening using an SM-401 magnetic structuroscope with an H-shaped attached electromagnet are shown with references for ShKh15 and EI928 steels. Possibilities of the device for testing the quality of tempering products made from 40KhN2MA and wheel-tire steels are demonstrated.     

钢纤维形状与掺量对UHPC施工及力学特性的影响

选用四种平直及两种端钩钢纤维,研究钢纤维体积掺量、长径比、形状、同形及异形纤维混掺对超高性能混凝土(UHPC)施工及力学性能的影响.通过相关实验得到了UHPC扩展度、抗压强度、抗折强度、能量吸收、断裂能及弯曲应力-挠度曲线;基于弯曲应力-挠度曲线及改进后的规范方法计算了UHPC的弯曲韧性指标;最后,开展了最佳纤维混掺比例的研究.结果表明:纤维掺量每增加0.5％,UHPC扩展度平均降幅为2.72％,抗压强度平均增幅为5.79％.抗折强度、弯曲韧性指数和能量吸收则先增后减(临界掺量为3.5％),断裂能呈上下波动(在3％时达最低值).随着纤维长径比的增大,UHPC扩展度降低,抗压强度、抗折强度、弯曲韧性指数、能量吸收值和断裂能基本呈递增趋势.相同长径比时,端钩形纤维UHPC扩展度、弯曲韧性指数优于平直形纤维,抗压强度、抗折强度、能量吸收、断裂能低于平直形纤维.同形纤维混掺UHPC扩展度、抗压强度稍低于对应的单掺纤维,弯曲韧性、能量吸收、断裂能总体上优于单掺试件;异形纤维混掺UHPC扩展度、抗压强度稍低于单掺试件,抗折强度与单掺试件各有所长,弯曲韧性、能量吸收及断裂能绝大多数优于单掺纤维.UHPC抗折强度变异性高于其抗压强度.单掺和混掺纤维时,UHPC试件的抗压强度、抗折强度综合最优分别为173.53 MPa、44.9 MPa和160.9 MPa、55.72 MPa;纤维混掺最佳组合为18 mm平直形、16 mm端钩形,且两者混掺比例为1:1时,UHPC的综合力学性能较优.     

Magnetic quality control of hardened and tempered parts made of carbon and low-alloyed steels (review)

The physical essence of the nondestructive quality control of mediate-and high-temperature tempering of parts made of carbon and low-alloyed steels containing more than 0.3% carbon, which is performed on the basis of measurements of the secondary residual magnetic inductance (magnetization) and relaxation coercive force of a body, is considered. Examples of the inspection of the hardness of tempered parts made of a number of steels of different grades are reported.