Group codes on certain algebraic curves with many rational points

We construct a series of algebraic geometric codes using a class of curves which have many rational points. We obtain codes of lengthq ² over _q , whereq = 2q ₀ ² andq ₀ = 2 ⁿ , such that dimension + minimal distance q ² + 1 – q ₀ (q – 1). The codes are ideals in the group algebra _q [S], whereS is a Sylow-2-subgroup of orderq ² of the Suzuki-group of orderq ² (q ² + 1)(q – 1). The curves used for construction have in relation to their genera the maximal number of GF _q -rational points. This maximal number is determined by the explicit formulas of Weil and is effectively smaller than the Hasse—Weil bound.Supported by Deutsche Forschungsgemeinschaft while visiting Essen University     

一种对称非均匀细分曲面算法

为了得到能更好应用于CAD系统的细分曲面造型方法,提出一种基于B-样条的对称非均匀细分算法,其中的思想和均匀Lane-Riesenfeld节点插入算法相似。基于B-样条的节点插入算法,以Blossoming为工具,计算出细分后的新控制顶点。细分后得到的极限曲面由张量积样条曲面组成,在奇异点达到2C连续。与传统的细分曲面算法相比,该细分曲面算法具有良好的局部支撑性,大大降低了算法的复杂度,而且该算法是对称的,不用考虑定向问题。     

致密油藏直井多层缝网压裂产量递减分析

垂向多层发育的致密油藏常采用缝网压裂进行开采,从而改善储层渗透率,提高油井产量。为此建立直井多层缝网压裂不稳定渗流数学模型,压裂后各层划分为人工裂缝区、改造区和未改造区。绘制分析Blasingame产量递减典型曲线,曲线分为7个流动阶段,总裂缝长度一定时,裂缝半长短的储层流体渗流率先到达未改造区,流体渗流阻力大,Blasingame曲线靠下;总改造体积一定时,各层改造体积差异越大,Blasingame曲线越靠下。用所建立的模型,对实测生产资料进行解释,获得各层裂缝半长、改造区渗透率等相关地层参数,该模型对进行多层缝网压裂直井产量分析具有指导意义。     

Molybdate and tungstate as corrosion inhibitors for cold rolling steel in hydrochloric acid solution

The inhibition effects of molybdate and tungstate on the corrosion of cold rolling steel (CRS) in hydrochloric acid solution (0.1-0.5 M) were investigated by weight loss and electrochemistry methods. The results reveal that both molybdate and tungstate are very good inhibitors with little concentration. The adsorption of inhibitors on the CRS surface basically obeys the Langmuir adsorption isotherm equation. The effect of temperature on the corrosion behavior of CRS was also studied at 25 °C and 35 °C, the thermodynamic parameters such as adsorption heat (ΔH⁰) and adsorption free energy (ΔG⁰) were calculated. In the same conditions, a comparative study of corrosion inhibition of molybdate and tungstate indicated that molybdate was the better inhibitor in 0.1 M HCl. However, the value of percentage inhibition efficiency (IE) was dependent on the concentration of inhibitors in 0.2-0.5 M HCl. It seemed that molybdate did not have the strong inhibitive effect compared to tungstate with relatively small concentration of inhibitors, but molybdate was a better inhibitor over a wide concentration range of inhibitors. A kinetic study of cold rolling steel in uninhibited and inhibited acid was also discussed. Various parameters such as rate constant k and the kinetic parameter B were calculated for the reactions of corrosion. Polarization curves showed that both molybdate and tungstate are mixed-type inhibitors in acidic media.     

改进的代理多重签名方案*

Ji和Li提出的一种基于椭圆曲线离散对数问题的代理多重签名方案存在两个问题：a）安全性,该方案的签名验证数据中没有避免孤悬因子这一现象,因此并不满足强不可伪造性,任意一个原始签名者能伪造代理多重签名;b）效率,代理多重签名的长度和验证其签名效率与原始签名者的个数有关。对Ji-Li代理多签名方案的安全性和效率进行了分析,提出了新的、安全的基于椭圆曲线离散对数问题的代理多签名体制,提高了签名验证效率、缩短了签名长度。     

保单调插值的奇异混合三角/双曲B样条

为了使得插值曲线保单调,设计了两类新的平面参数曲线及其保单调插值算法.计算奇异混合函数,把三角/双曲多项式B样条曲线与奇异多边形通过奇异混合函数混合,无需解方程组或繁琐的迭代,得到自动插值给定平面点列且C2(或G1)连续的带形状参数的复合曲线,尤其能得到摆线、螺旋线、双曲线、悬链线等各类超越曲线.通过把插值曲线的导矢分量转化为类Bernstein多项式,并且利用Bernstein多项式非负的充要条件,得到插值曲线单调的充要条件,获得形状参数合适的取值范围. 该方法简单方便,所得参数范围保证了插值曲线保单调.     

用微型剪切试验研究WDL610焊接接头性能

采用微型剪切的试验方法对WDL610钢焊接接头进行了研究,绘制出强度梯度曲线和塑性梯度曲线,直观地显示出接头各个狭窄区域的性能和变化规律.尤其是调质钢焊接接头的软化区,其性能值和宽度严重影响接头的承载能力.     

自由曲面的测量、建模、加工一体化过程研究

本文以一个鼠标模型为例，介绍了自由曲面的测量、建模、加工一体化过程，对一体化过程的各个步骤进行了研究为实现逆向工程集成化奠定了基础。     

基于DXF文件的曲线拟合方法的设计与实现

现有的基于微机开发的数控加工系统都是人工调试完成后加载运行,为了能够依据AUTOCAD绘图系统提供的信息自动生成数控加工代码,本文对基于PMAC卡的数控加工代码生成及动态在线监测系统研制过程中遇到的问题进行了研究,重点研究了如何利用DXF文件中的参数进行曲线拟合,详细介绍了NURBS曲线算法的实现,为后续的工作打下了基础。