NAG算法库在冶金过程控制建模中的应用

在介绍数学软件NAG(The Numerical Algorithms Group)的基础上,以构建过程控制模型为实例,论述了NAG在钢铁企业中的应用。使相关技术人员充分认识NAG软件在建模中的效率,进一步提高解决实际问题的能力。     

Effect of Endgrain Attack on Corrosion of 18Cr-10Ni Austenitic Stainless Steel in Simulated Dissolver Liquor

The exposed endgrain of austenitic stainless steels displays significantly inferior corrosion resistance toward the rolling direction in nitric acid solutions. Endgrain attack is often accompanied by preferential localised corrosion which produces features similar to pitting corrosion. From the viewpoint of average corrosion rate and penetration depth the effect of endgrain attack on the corrosion of 18Cr-10Ni austenitic stainless was investigated in simulated dissolver liquor under non-boiling conditions. The average corrosion rate of coupons was evaluated as a function of endgrain ratio to total surface area. In addition the effect of orientation with respect to the rolling direction was measured directly by observing the dimensional change of holes drilled into coupons. It was found that the proportion of exposed endgrain affected the coupon corrosion rate. From the hole growth measurements it was found that the average corrosion rate in the rolling direction was 2.3 mm/yr approximately 1.5 times higher than that of the vertical one on the surface. From sections the maximum extent of pitting penetration into the endgrain was estimated to be approximately 8.8 mm/yr.     

硝酸级(NAG)310L不锈钢焊接接头在含Cr~(6+)的HNO_3溶液中的耐蚀性

对硝酸级(NAG)310L不锈钢焊接接头在含氧化性离子的沸腾硝酸中进行浸泡实验及金相分析。研究表明,在不同Cr~(6+)含量的沸腾40%HNO_3中,材料的腐蚀程度主要受Cr~(6+)含量的影响。随Cr~(6+)含量的增加,母材和焊缝均出现不同程度腐蚀,但焊缝较母材腐蚀严重。Cr~(6+)含量是促进焊缝过钝化腐蚀和晶间腐蚀的主要因素。     

N-Acetyl Glucosamine Obtained from Chitin by Chitin Degrading Factors in Chitinbacter tainanesis

A novel chitin-degrading aerobe, Chitinibacter tainanensis, was isolated from a soil sample from southern Taiwan, and was proved to produce N-acetyl glucosamine (NAG). Chitin degrading factors (CDFs) were proposed to be the critical factors to degrade chitin in this work. When C. tainanensis was incubated with chitin, CDFs were induced and chitin was converted to NAG. CDFs were found to be located on the surface of C. tainanensis. N-Acetylglucosaminidase (NAGase) and endochitinase activities were found in the debris, and the activity of NAGase was much higher than that of endochitinase. The optimum pH of the enzymatic activity was about 7.0, while that of NAG production by the debris was 5.3. These results suggested that some factors in the debris, in addition to NAGase and endochitinase, were crucial for chitin degradation.     

Vertical migration of numerical routines in software and microcode

Vertical migration is a widely acknowledged technique for improving the performance of critical sections of code. Migration may be to the assembly-language level or, for machines with writable control store, into microcode. The former is easier to implement and allows a degree of portability, albeit limited, of the target routines, although performance gains may not be as great as those resulting from migration into microcode. The latter however, requires considerable programming effort and the size of available control store may well place restrictions upon the amount of code which can be migrated to this level. Given the task of improving the performance of a large software base, full migration is rarely practical, so time must be spent determining the best migration strategy for a ‘target set’ of critical routines. In this paper, we report on work to improve, by vertical migration, the performance of the bask linear algebra subroutines of the FORTRAN NAG library. We identify a number of different migration strategies based upon the availability of two migration levels and report on the performance gains achieved by applying each of these strategies; various conditions under which each strategy may be most appropriate have thus been identified. In particular, this work shows how, by careful selection of just a small number of target routines, resulting performance gains can not only be significant for each individual routine, but also for the whole software system.     

冰岛刺参岩藻糖基化硫酸软骨素对高脂饮食诱导的糖尿病小鼠肾脏的保护作用

目的：研究冰岛刺参岩藻糖基化硫酸软骨素（fucolysated chondroitin sulfate from Cucumaria frondosa,Cf-CHS）对高脂饮食诱导的糖尿病小鼠肾脏的保护作用。方法：以高脂高糖饲料饲喂诱导Ⅱ型糖尿病小鼠模型,饲喂含不同剂量Cf-CHS的高脂高糖饲料连续19 周,检测空腹血糖并收集尿液,分别检测小鼠尿液中尿糖、微量白蛋白（microalbumin,mAlb）、尿总蛋白、尿素氮（urea nitrogen,UN）、尿酸（uric acid,UA）、肌酐（creatinine,Cr）浓度和β-N-乙酰葡萄糖苷酶（N-acetyl-β-glucosaminidase,NAG）排泄率,摘取肾脏观察肾脏组织的显微结构。结果：Cf-CHS可显著降低糖尿病小鼠的尿糖、mAlb、尿总蛋白、UN、UA、Cr浓度和NAG排泄率（P＜0.01）,改善肾脏组织的显微结构。结论：Cf-CHS可显著改善糖尿病小鼠的肾脏功能。     

基于AdaGrad的自适应NAG方法及其最优个体收敛性

与梯度下降法相比,自适应梯度下降方法(AdaGrad)利用过往平方梯度的算数平均保存了历史数据的几何信息,在处理稀疏数据时获得了更紧的收敛界.另一方面,Nesterov加速梯度方法(Nesterov's accelerated gradient,NAG)在梯度下降法的基础上添加了动量运算,在求解光滑凸优化问题时具有数量...     

功能性食品添加剂 N-乙酰-D-葡糖胺的理化性质

N-乙酰-D-葡糖胺是一种具有多种生理活性和功能性质的重要氨基糖 .实验研究了NAG的一些重要理化性质和加工稳定性 ,为NAG在食品中的应用提供理论依据 .结果表明 ,NAG易溶于水 ,微溶于乙醇 ;NAG晶体在 1 2 0℃、6h下保留率大于 98% ,性质稳定 ;在 1 0 0℃、6h、pH 3 .0～8.5的条件下 ,NAG水溶液稳定性好 ,pH超过 8.5则保留率大大降低 ,并伴有颜色变化 ;NAG在牛奶杀菌条件下性质稳定 ;NAG不具有吸湿性和保湿性     

Clean galena, contaminated lead, and soft errors in memory chips

Lead (Pb) disks were exposed to a radon (Rn)-rich atmosphere and surface alpha particle emissions were detected over time. Cumulative ²¹⁰Po alpha emission increased nearly linearly with time. Conversely, cumulative emission for each of ²¹⁸Po and ²¹⁴Po was constant after one and two hours, respectively. Processing of radiation-free Pb ore (galena) in inert atmospheres was compared with processing in ambient air. Galena processed within a flux heated in a graphite crucible while exposed to an inert atmosphere, resulted in lead contaminated with ²¹⁰Po (Trial 1). A glove box was next used to prepare a baseline radiation-free flux sample in an alumina crucible that was heated in an oven with an inert atmosphere (Trials 2 and 3). Ambient air was thereafter introduced, in place of the inert atmosphere, to the radiation-free flux mixture during processing (Trial 4). Ambient air introduced Rn and its progeny (RAD) into the flux during processing so that the processed Pb contained Po isotopes. A typical coke used in lead smelting also emitted numerous alpha particles. We postulate that alpha particles from tin/lead solder bumps, a cause of computer chip memory soft errors, may originate from Rn and RAD in the ambient air and/or coke used as a reducing agent in the standard galena smelting procedure. Author’s Note: No-alpha lead (NAL) as used in this article is a misnomer. What is meant is lead in which the alpha particle (α) emission is so low that it cam not be detected with current instrumentation and t memory chips are not affected by α emission from lead solder bumps.     

距离保持水平集演化模型的快速实现算法

针对梯度下降法收敛性较差、对局部极小值比较敏感的问题,提出一种改进NAG算法,并以此替换距离保持水平集演化（DRLSE）模型中的梯度下降算法,进而得到一个基于NAG的图像快速分割算法。首先,给出初始水平集演化方程;其次,用改进NAG算法计算梯度;最后,对水平集函数进行不断更新,从而避免水平集函数陷入局部极小值。实验结果表明,与DRLSE模型中的原算法相比,所提算法迭代次数减少了约30%,CPU运行时间减少了30%以上。该算法实现简单,能够对实时性要求较高的红外图像、医学图像进行快速、有效的分割。