一维非定常对流扩散方程非均匀网格上的高精度紧致差分格式

本文在非均匀网格上给出了求解非定常对流扩散方程的一种高精度紧致差分格式,特别适合边界层和大梯度等问题的求解.从稳态对流扩散方程入手,首先,基于非均匀网格上的泰勒级数展开对空间导数项进行离散,然后对时间项采用二阶向后欧拉差分公式,从而得到一维非定常对流扩散方程在非均匀网格上的三层全隐式紧致差分格式.新格式在时间具有二阶精度,空间具有三到四阶精度,并且是无条件稳定的.最后,通过数值实验验证了本文格式的精确性,以及在处理诸如边界层和大梯度问题上的优势.     

Cahn-Hilliard方程的时间双层网格有限元方法

针对用非线性数值格式求解Cahn-Hilliard方程时由非线性迭代引起的耗时问题,本文提出了一种时间双层网格(TT-M)有限元(FE)方法.该方法分为两步:第一步,在粗的时间步长上求解非线性Cahn-Hilliard系统,其中空间离散采用有限元方法,时间离散采用Crank-Nicolson格式;第二步,在细的时间步长上求解线性系统,然后证明了该方法的稳定性和误差估计,并通过数值算例对理论部分进行验证.结果表明,与传统的Galerkin有限元方法相比,该方法可以节省计算时间,说明了该方法的有效性和可行性.     

修正的Cahn-Hilliard方程的大时间步长方法

过去的几十年中,Cahn-Hilliard方程引起了很多学者的关注.该方程最早被用来描述在温度降低时两种均匀的混合物所发生的相分离现象.随着理论的深入研究,该方程在其他方面也有广泛的应用.修正的Cahn-Hilliard方程是一个四阶非线性抛物方程,再加上该方程的小参数问题,使得该方程在求精确解时,具有一定的难度,只能利用数值方法在较小的时间步长上求解数值解,若在较大的时间步长上进行求解会造成数值解的发散.本文提出了求解修正的Cahn-Hilliard方程的大时间步长方法.所提格式在空间上采用有限元方法离散,在时间上采用一阶半隐格式进行离散,证明了一阶半离散格式的稳定性及全离散格式的误差估计.最终通过数值算例来验证理论分析的准确性及有效性.     

氧碘化学激光器组分超音速混合反应数值模拟

采用数值方法求解二维可压缩非定常N-S方程及组分连续方程,计算氧碘化学激光器中的组分超音速混合反应流场.空间离散格式为AUSM -up格式,用四步龙格-库塔方法作显式时间推进,湍流粘性系数使用k-ε两方程湍流模型进行求解.假设混合气体为热力学完全而热值非完全气体,化学反应模型采用有限速率反应模型.使用一种松弛迭代的方法来处理化学源项的刚性问题.给出了出口处碘分子的质量分数分布,数值模拟结果与文献结果符合良好.     

任意多边形上非定常扩散方程的单元中心型有限体积格式

针对二维非定常扩散方程,构造适用于任意多边形网格的单元中心型有限体积格式。采用向后欧拉格式进行时间离散,空间上在离散扩散算子时,利用网格顶点作为辅助插值点,通过求解一个欠定方程组将辅助插值点信息替换成网格单元中心点信息,最终得到只含单元中心未知量的离散格式。该格式既满足局部守恒条件,又满足线性精确准则。在几类多边形网格上进行数值实验,分别考虑扩散系数是连续和间断的情况,发现新格式均可达到二阶收敛。其数值表现显著优于算数平均加权和逆距离加权的九点格式,与双线性插值的加权方式结果相近,并且克服了双线性插值加权方式不适用于三角形网格的弊端。数值算例表明新格式求解非线性扩散方程仍然可以达到二阶收敛。     

随机动力学中FPK方程的径向基点插配点方法求解

应用径向基点插配点方法对随机动力学中的FPK方程进行了求解.所求未知函数的空间插值采用径向基点插近似,而时间导数离散采用差分格式,建立具有带宽特性的代数方程,采用逐次超松弛迭代法（SOR）有效地求解所得到的代数方程.针对线性振子和杜芬振子问题的FPK方程进行了具体的数值求解,计算结果表明了方法的有效性,尤其是散点模型的计算结果表明该方法具有比其它有网格数值方法对非规则离散模型适应性更强的优点.     

二维非线性对流扩散方程的特征混合有限元两重网格算法

本文构造了求解非线性对流扩散方程的两重网格算法,该算法首先是在步长为H的粗网格上求解一个非线性问题,再利用粗网格解得到一个线性问题并在细网格上求解一个线性问题.理论分析与数值计算表明,该算法不仅消除了数值振荡现象,还极大地提高了非线性对流扩散方程的计算效率.     

三维定常/非定常Stokes方程的维数分裂算法

本文针对三维柱形区域提出了定常/非定常Stokes方程基于一致分裂格式的维数分裂算法(DSA).文章推导了三维定常/非定常Stokes方程维数分裂方法的数值迭代格式.新算法的优势在于一系列的二维问题能够并行执行,而且数值计算中避免了三维网格的生成.大量的数值结果表明新算法既能获得最优收敛阶,而且能获得比采用四面体元求解更精确的逼近解.最后,通过采用并行求解新算法能够得到比较好的加速比和并行效率.     

三维定常/非定常Stokes方程的维数分裂算法（英文）

本文针对三维柱形区域提出了定常/非定常Stokes方程基于一致分裂格式的维数分裂算法(DSA).文章推导了三维定常/非定常Stokes方程维数分裂方法的数值迭代格式.新算法的优势在于一系列的二维问题能够并行执行,而且数值计算中避免了三维网格的生成.大量的数值结果表明新算法既能获得最优收敛阶,而且能获得比采用四面体元求解更精确的逼近解.最后,通过采用并行求解新算法能够得到比较好的加速比和并行效率.     

基于投影法求解不可压缩流的高精度紧致格式

本文建立了一种基于投影法的求解不可压缩Navier-Stokes(N-S)方程的高精度紧致差分格式。该方法时间上采用Kim和Moin二阶投影法离散,空间上采用高精度紧致格式离散,并提出了一种新的离散压力边界的紧致格式,同时对计算结果进行分析以验证该投影法的精度和格式稳定性。文中Taylor涡列数值计算结果表明,Kim和Moin投影法能使得压力场和速度场均达到时间二阶精度,且高精度紧致格式投影法也具有空间高阶精度。驱动方腔数值模拟结果显示,本文对N-S方程的离散格式具有很好的可靠性,适用于对复杂流体流动的小尺度问题的数值模拟和研究。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.