压力容器标准椭圆封头拼接焊缝射线探伤工艺的改进措施

为了满足生产需要对椭圆封头拼接焊缝射线探伤工艺进行改进。并取得了满意效果。     

Effects of Background Plasma on Free Electron Laser with Planar Wiggler

Dispersion equation of planar-wiggler free-electron laser with background plasma is derived using linear fluid theory. The characteristic of this plasma FEL is analyzed in detail. It is shown that reasonable background plasma density tends to improve FEL growth rate. We also find there exits a critical plasma density for FEL operating. When the background plasma density is higher than critical density, the FEL can no longer be excited.     

Process conditions for separating fatty acid esters by supercritical CO2

The solubilities of ethyl palmitate, ethyl oleate, ethyl eicosapentaenoate (EPA) and ethyl docosahexaenoate (DHA) in supercritical carbon dioxide were determined by a continuous flow method. The solubilities of fatty acid ethyl esters increased with pressure and decreased as the temperature was increased. An empirical equation, similar to Chrastil's equation, was used to describe the relationship between solute solubility and the density of carbon dioxide. The empirical equation was further used to qualitatively estimate the separation efficiency of isolating EPA and DHA ethyl esters from fatty acid esters. The operating conditions yielding high solubility gave fast extraction rate but resulted in low separation efficiency. Experiments were conducted to separate ethyl EPA and ethyl DHA from a model mixture containing four fatty acid ethyl esters and from esterified squid visceral oil. The experimental data compared closely with the calculated values.     

Characterization of the ntrBC genes of Azospirillum brasilense Sp7: their involvement in the regulation of nitrogenase synthesis and activity

The in vitro effect of citric acid application on periodontally involved root surfaces was investigated using scanning electron microscopy. Teeth were selected following specific criteria. The specimens were prepared for observation, and the features of the root surface were studied. The results demonstrated that a 3-minute application of citric acid (pH = 1.0) to the root surface after scaling and root planing demineralized the outer root surface, opened the dentinal tubules, and exposed collagen fibers. Scaling and root planing alone left the surface with a smear layer, scattered islands of cementum, and no collagen fibers or exposed dentinal tubules.     

Monoalkyl Esters of Isoalkylphosphonic Acid as Extractants in Rare Earth Separation

Four monoalkyl esters of isoalkylphosphonic acids have been studied for the chromatographic separation ofrare earths (RE).The relationship between distribution ratios and acid concentration of the eluants forsamarium and ytterbium has been explored.The characteristics of these extractants loaded onto macroreticularpoly (methyl methacrylate) resin beads for the separation of lanthanum,cerium,praseodymium and neodymiumhave been compared.Among the extractants studied,mono(1-methylheptyl) ester of isooctylphosphonic acidwas found to be the best for RE separation.The acidity for separation is lower than any known P-containingextractants for the same purpose.For instance,with 1.73 mol·L~(-1) nitric acid as eluent,thulium,ytterbium andlutetium can be separated quantitatively.The extractant-loaded resins possess high column efficiency with goodkinetic characteristics.The extraction mechanism was also explored.     

高等植物氨基酸生物效应的研究进展

本文对氨基酸营养条件下植物体内硝酸盐含量变化及其机理,土施植物激素前体色氨酸和蛋氨酸对高等植物生长和化学组成的影响。氨基酸和氨基酸肥料对植物产量和品质的影响作了综述。     

油田热采注汽管道在线检测技术现状

稠油热采注汽管道由于长期在高温、高压下运行,极易发生各种损伤,如腐蚀、裂纹、材料退化等,极易造成管道承压能力降低,发生失效事故。如何检测出潜在危险性缺陷,判断注汽管道能否继续使用,是保证注汽管道安全运行的关键问题。探讨了高温压力管道在线检测技术发展现状及其应用范围。     

石油价格机制改革之对策

文章在阐述我国石油价格形成机制的演变过程的基础上,针对我国目前石油定价机制所导致的诸如石油价格变动滞后以及由此带来的市场信号失灵等问题思考了相应的改革对策,提出了调整政府价格管理职能、建立平等竞争的市场规则、完善稳定油价的调控体系以及加快建立石油战略储备等7个方面的建议。     

女人一生的避孕攻略——不同时期的避孕法则

女性自初潮开始到绝经的过程中，有30多年的时间需要避孕。如何在这样漫长的时间里安全避孕。是每位女性维护自身健康必不可少的一项措施。有人说：“怀孕是生命力的表现，如果我们不用避孕了，那一定不是老了就是病了。”因此。避孕对于女性来说，是一件甜蜜而又麻烦的事。如果因意外怀孕而不得不采取人工流产。不仅会给女性带来心灵上无法抚平的伤害，还可能由此引发不孕、感染以及妇科肿瘤等不良后果。因此了解各种避孕节育方法的有效性、优缺点，将有助于女性在人生的不同阶段，选择那些有效、安全、适合自己的避孕节育方法，降低避孕失败的风险。[编者按]     

柳钢35t转炉方坯连铸机系统优化措施

介绍柳钢35t转炉方坯连铸机系统优化措施，通过优化使生产稳定性提高，铸坯质量得到改善，提高各项经济技术指标。