1999年中国液化石油气进口再创新高

1999年对中国的能源进出口贸易来说是一个创记录的年份。液化石油气(以下简称液化气)也不例外,进口量创下了554万t的最高记录。液化气进口从10年前的不足10万t发展到550万t,标志着液化气市场的巨大变化。在中国的能源市场上,液化气是进口产品占有最大份额的品种之一,约占41％。经过10年平均每年大约20％的膨胀,中国液化气市场已经成长为仅次于美国和日本的全球第3大液化气消费国。     

预弯钢-混凝土组合连续梁桥预应力施加技术

以组合梁预应力施加的方法为基础,分析其设计所采用方法的不足之处,从而选择了更有利的预应力施加方法组织施工,取得了良好的效果。     

SWOT分析法在项目风险管理中的应用

SWOT分析是项目风险管理有效的识别技术工具,介绍SWOT分析的定义、模型以及局限性.提出了弥补这一缺陷的有效方法,SWOT分析与层次分析法相结合更加准确地描述和识别项目存在的风险,为企业进行项目战略决策和系统分析提供了依据.     

Synthesis of LaF3 superfine powder by microwave heating method

LaF3 superfine powder was synthesized from La(CH3COO)3 and NH4 F by microwave heating method,using ethanol or pure water as dispersants respectively. The results of XRD and SEM indicate that the superfine powder has high purity, regular particle shape and narrow distribution of granularity. The granularity of the best sample is in the range of 100 -200 nm. The influence of different dispersants on the crystal degree and microstructure was discussed. After the superfine powder was formed into a slice at pressure of 25 - 60 MPa, its electrochemical impedance spectroscopy was tested by electrochemical impedance spectroscopy (EIS) measurement. The result shows that the grain refining of LaF3 powder increases its ionic conductivity. Compared with traditional preparation methods of LaF3 powder, the advantages of microwave heating method were summarized.     

Effects of Ca addition on microstructure and properties of AZ63 magnesium alloy

1　INTRODUCTIONMg Alalloyshaveaverywideapplicationbecauseoftheirexcellentproperties ,lowmanufacturecost ,easymeltingtechniqueandnoexpensiveele mentscontent[1] .Oneofthiskindalloys ,AZ6 3mag nesiumalloy ,isawidelyappliedmagnesiumsacrifi cialanodewhichisusedextensivelyinundergroundandfreshwateratpresent .However ,compared withthataboard ,homesacrificialanodehassomedemer its :lowcurrentefficiencyandweakprotectionfunc tion ,soinvestigatingthehighdriving potentialandhighefficiencysacrificiala…     

RPF-AA改性纤维的制备及耐硫酸侵蚀性研究

通过对普通腈纶进行特殊预处理和改性,制备出一种具有良好抗浓酸侵蚀性的反应性高分子纤维材料,对改性纤维材料的化学(酸)稳定性、力学性能、微结构等特征性能研究表明:该纤维材料在120℃和98%浓硫酸环境条件下,经过20 min的侵蚀性处理后,其材料仍能够保持一定的力学性能和微结构,显示了突出的抗浓硫酸侵蚀性.     

剥离型酚醛树脂/蒙脱土纳米复合材料研究

用十六烷基三甲基溴化铵(CTAB)对蒙脱土进行了有机化处理,使蒙脱土由亲水性变成亲油性。采用XRD、FTIR及TEM研究了有机蒙脱土及其在酚醛树脂中的剥离行为,制备了酚醛树脂/蒙脱土纳米复合材料并测试了其层间剪切性能和烧蚀性能。实验结果表明,经CTAB处理的蒙脱土与酚醛树脂具有良好的相容性,且CTAB的含量较多时所制得的有机蒙脱土的结构较好,根据Bragg方程计算,CTAB用量超过蒙脱土量50%时,蒙脱土的片层间距由原来的1.48 nm增加到2.33 nm;有机蒙脱土用量小于5%时生成完全剥离型酚醛树脂/蒙脱土纳米复合材料;与碳布增强酚醛树脂复合材料相比,碳布增强酚醛树脂/蒙脱土纳米复合材料的力学性能和烧蚀性能均有一定的提高和改善,层间剪切强度随蒙脱土含量的增多而增大,蒙脱土用量为15%时,层间剪切强度提高了27.1%,线烧蚀率在用量为3%时降低了48.5%,质量烧蚀率变化不明显。     

接枝率和PA-6对LDPE/PA-6共混物力学性能的影响

研究了PE-g-MAH接枝物中的MAH以及PA6对PE／PA6共混物力学性能的影响。结果表明,采用质量分数为2％的MAH制备的LDPE-g-MAH,与PA6按60：40共混所得共混物的力学性能最佳。     

回收废聚苯乙烯泡沫的研究

针对目前白色污染日益严重的状况,采用桔子油溶解回收废聚苯乙烯泡沫,通过实验探讨了影响聚苯乙烯泡沫回收的因素,如PS的浓度、沉淀剂的体积、助剂的体积等,利用正交实验对回收聚苯乙烯泡沫和桔子油的最佳条件进行了探讨。该工艺不经热处理,性能不会改变,聚苯乙烯泡沫和桔子油的回收率均可达90％以上,对环境友好。     

Effect of ultrasonic power and bonding force on the bonding strength of copper ball bonds

Copper wire, serving as a cost-saving alternative to gold wire, has been used in many high-end thermosonic ball bonding applications. In this paper, the bond shear force, bond shear strength, and the ball bond diameter are adopted to evaluate the bonding quality. It is concluded that the ef/~cient ultrasonic power is needed to soften the ball to form the copper bonds with high bonding strength. However, excessive ultrasonic power would serve as a fatigue loading to weaken the bonding. Excessive or less bonding force would cause cratering in the silicon.