注凝析油开采稠油的地质工艺

在西西伯利亚俄罗斯油田开展了注凝析油开发稠油的研究，现场实验结果表明，注入25%的凝析油，可使其混合液粘度达到原高粘油粘度的1/60，以俄罗斯油田为例，探讨了注凝析油矿场试验的可行性，预测了凝析油的用量和可能产出的油量，并对原油外输提出了一系列更换工艺设备的要求。     

世界钢材价格现状及2004年一季度预测

一、扁平材产品1.热轧板卷。目前,在美国的带钢产品中,热轧板卷市场价格是最坚挺的。在2003年7月初,生产厂曾一度努力提升热轧板卷市场价格,一直未取得成功,直到2003年8月,提价才取得部分成功。最近,美国国际钢铁集团又把其热轧板卷公布的价格每吨提升10美元,这是该集团在5周里第2次提价。美国热轧板卷生产厂报道说,目前接到的订货单比过去多得多,势头相当猛。订货单大幅度增加的原因是,钢管制造业部门和石油工业部门生产经营活动相当兴旺活跃,再加上严格坚持限产措施,从而拉动了价格上升。热轧板卷的交货时间,在某些情况下,已推迟到2004年1…     

我国钢铁工业竞争态势正在发生重大变化——国外钢铁研究机构评价报告摘编

美国世界钢动态公司认为中国(不包括港、澳、台,下同)钢铁厂面临的竞争态势正在发生重大变化,正面临威胁更大、更加多样和更难以预测的市场竞争环境。中国钢铁工业依然处在巨大的结构调整和优化阶段。美国世界钢动态公司从27个方面来评估和分析中国钢铁厂面临的新挑战或可能出现的发展局面。第一,在中国钢铁行业中商业运作获利的“旧模式”已成为过去。在2003年至2004年之前,同政府权力机构保持良好关系的实业家曾利用其权势轻而易举获取极其充足的贷款投到赢利的钢铁行业。利用这些贷款迅速建设起投资费用低的小钢铁厂或小的独立轧钢厂,并…     

基于OSEK规范的网络管理的研究与改进

首先论述了基于OSEK规范的网络管理特点并对OSEK网络管理的工作机制进行了详细分析;在基于OSEK网络管理特点和工作机制的基础上,对OSEK网络管理在以太网上的扩展、资源占有率优化和实时性提高几个方面给出了解决方案。     

基于SPW的流星余迹极低信噪比通信系统建模与仿真*

SPW具有丰富的通信库和DSP库,且具有灵活的自定义模块能力,是一种复杂通信系统建模和仿真工具.流星余迹通信是一种特殊的通信方式,在通信领域中具有特殊的重要地位.介绍了流星余迹极低信噪比通信系统原理的基础,给出了基于SPW的流星余迹极低信噪比通信系统仿真模型及仿真结果.     

In vitro comparison of hepatic metabolism of 9cis-11 trans and 10trans-12cis isomers of CLA in the rat

Hepatic metabolism of the two main isomers of CLA (9cis-11 trans, 10trans-12cisC_18∶2) was compared to that of oleic acid (representative of the main plasma FA) in 16 rats by using the in vitro method of incubated liver slices. Liver tissue samples were incubated at 37°C for 17h under an atmosphere of 95% O₂/5%CO₂ in a medium supplemented with 0.75 mM of FA mixture (representative of circulating nonesterified FA) and with 55 μM [1-¹⁴C]9cis-11 trans C_18∶2, [1-¹⁴C]10trans-12cis C_18∶2, or [1-¹⁴C]oleate. The uptake of CLA by hepatocytes was similar for both isomers (9%) and was three times higher (P<0.01) than for oleate (2.6%). The rate of CLA isomer oxidation was two times higher (49 and 40% of incorporated amounts of 9cis-11 trans and 10trans-12 cis, respectively) than that of oleate (P<0.01). Total oxidation of oleate and CLA isomers into [¹⁴CO₂] was low (2 to 7% of total oxidized FA) compared to the partial oxidation (93 to 98%) leading to the production of [¹⁴C] acid-soluble products. CLA isoemrs escaping from catabolism were both highly desaturated (26.7 and 26.8%) into conjugated 18∶3. Oleate and CLA isomers were mainly esterified into neutral lipids (30%). They were slowly secreted as parts of VLDL particles (<0.4% of FA incorporated into cells), the extent of secretion of oleate and of 10trans-12 cis being 2.2-fold higher than that of 9cis-11 trans (P<0.02). In conclusion, this study clearly showed that both CLA isomers were highly catabolized by hepatocytes, reducing their availability for peripheral tissues. Moreover, more than 25% of CLA escaping from catabolism was converted into conjugated 18∶3, the biological properties of which remain to be elucidated.     

Effects of conjugated linoleic acid isomers on the hepatic microsomal desaturation activities in vitro

The influence of individual conjugated linoleic acid (CLA) isomers on the Δ6 desaturation of linoleic and α-linolenic acids and on the Δ9 desaturation of stearic acid was investigated in vitro, using rat liver microsomes. The Δ6 desaturation of 18∶2n−6 was decreased from 23 to 38% when the ratio of 9cis,11trans-18∶2 to 18∶2n−6 increased from 0.5 to 2. The compound 10trans,12cis-18∶2 exhibited a similar effect only at the highest concentration. The Δ6 desaturation of α-linolenic acid was slightly affected by the presence of CLA isomers. The sole isomer to induce an inhibitory effect on the Δ9 desaturation of stearic acid was 10trans,12cis-18∶2.     

遗传算法理论及其应用研究进展

首先阐述遗传算法的原理和求解问题的一般过程;然后讨论了近年来从遗传算子、控制参数等方面对遗传算法的改进,并对遗传算法在计算机科学与人工智能、自动控制以及组合优化等领域的应用进行陈述;最后评述了遗传算法未来的研究方向和主要研究内容。