Optimal design of gating systems by gradient search methods

A numerical optimization technique based on gradient-search is applied to obtain an optimal design of a typical gating system used for the gravity process to produce aluminum parts. This represents a novel application of coupling nonlinear optimization techniques with a foundry process simulator, and it is motivated by the fact that a scientifically guided search for better designs based on techniques that take into account the mathematical structure of the problem is preferred to commonly found trial-and-error approaches. The simulator applies the finite volume method and the VOF algorithm for CFD analysis. The direct gradient optimization algorithm, sequential quadratic programming (SQP), was used to solve both a 2D and a 3D gating system design problems using two design variables. The results clearly show the effectiveness of the proposed approach for finding high quality castings when compared with current industry practices.     

The Minimum PAPR Code for OFDM Systems

In this letter, a block code that minimizes the peak‐to‐average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals is proposed. It is shown that peak envelope power is invariant to cyclic shift and codeword inversion. The systematic encoding rule for the proposed code is composed of searching for a seed codeword, shifting the register elements, and determining codeword inversion. This eliminates the look‐up table for one‐to‐one correspondence between the source and the coded data. Computer simulation confirms that OFDM systems with the proposed code always have the minimum PAPR.     

Express Method for Estimation of Tensile Strength and Crack Resistance of Brittle Media

The procedure is proposed for estimating the crack resistance and tensile strength of rocks by the results of experiments on disk samples with holes. The gradient approach to the strength problem is employed in processing the experimental data.     

激光加热在Al2O3/Ti系梯度功能材料制备过程中的作用及机理

梯度功能材料是一种界面连续化的新型复合材料,本文研究了激光加热在合成Al2O3/Ti系梯度功能材料过程中的作用和机理,同时用激光大光斑加热方法制备出直径11mm厚度3mm完整的FGM试样并加以分析,以及首次采用在试样中埋设微细热电偶成功地测出了激光加热造成的温度梯度分布。     

应用图论及广义简约梯度法进行压力管网优化设计

广义简约梯度法(GRG)是非线性规划算法中最有效的算法之一，本文把图论应用于广义简约梯度法优化的过程中，使输入简便，计算简化，应用GRG算法对武汉市的汉阳管网进行了模拟优化设计，并对管段的计算管径用线性规划法进行标准化，取得了满意的结果     

多信道光纤环形网络结构分析

本文对多信道光纤环形网络结构进行了详细分析，推导出环网内平均路经长度和最大直径计算公式，并分析了最佳多信道光纤环网结构。     

利用梯度方向信息的随机Hough变换

针对随机Ｈｏｕｇｈ变换（ＲＨＴ）在处理复杂图像随机采样造成的大量无效积累提出一种改进的用于直线检测的ＲＨＴ，较发地解决了无效果累积问题，并使改进后的算法具有计算速度更快，占用内存更少以及检测性能更好等优点。     

He－Ne激光对小麦属间杂交影响的研究

１９８８～１９９２年，作者采用Ｈｅ－Ｎｅ激光辐照黑麦花粉与杂交相结合的方法，对小麦属间杂交（普通小麦×黑麦）进行了研究。属间杂交所获种子的结实率极显著高于对照，为１１３．２５～３４１．６０％。籽粒千粒重和饱满度均超过对照，差异极显著。Ｌ＿１代籽粒出苗率和植株成活率分别比对照提高５８．１８～８３．０６％，４１．３５～８７．７８％，差异均超过极显著水平。Ｌ＿１代种子、植株和穗的大多数形态特征呈中间型或似父本，其余特点象母本。在Ｌ＿１代植株中均获得了染色体自然加倍的双二倍体，即小黑麦种子。现已获得了Ｌ＿１、Ｌ＿２、Ｌ＿３和Ｌ＿４代的小黑麦后代材料。Ｈｅ－Ｎｅ激光诱变小麦属间杂交，使杂种染色体自然加倍，为小麦属间杂交育种工作提供了新的简便途径。     

Introduction to geothermal exploration on ascension island, South Atlantic Ocean

The exploration for a geothermal resource on Ascension Island utilized a strategy that initially employed geologic mapping. On the basis of this, subsurface faults were mapped using an aeromagnetic survey. The faults were then explored using electrical resistivity surveys to define areas of potential hydrothermal fluid up-welling. The results of all of these techniques were used to site temperature gradient holes. A deep geothermal exploration well was then drilled in the area with highest heat flow adjacent to a rhyolite-to-trachyte volcanic complex.     

宽线性共轭梯度算法及其在盲多用户检测中的应用

本文提出了一种宽线性共轭梯度算法，分析了算法在均值意义下的收敛性，并给出了算法稳定条件。仿真表明，新算法应用于码分多址系统多址干扰抑制时的性能优于Yin（2003）及Schober（2004）所提出的算法。