硼酸使掺铁铝酸锂发光增强的现象

在硼酸存在下合成了掺铁铝酸锂荧光体,研究了在不同温度下硼酸加入量对荧光体发光强度的影响,并通过X射线粉末衍射和粒度分析,初步探讨了发光增加的原因。     

美国COMSTAC/AST卫星发射市场预测

隶属于美国联邦航空管理委员会（FAA）的美国商业航天运输咨询委员会（COMSTAC）和商业航天运输管理协会（AST）在每年的5-6月份都对未来10年的商业卫星发射市场进行预测。2001年该委员会对商业同步轨道（GEO）和非同步轨道（NGEO）的卫星需求和发射需求都进行了预测。     

二维地震过障碍观测系统模式及其参数设计

在二维地震勘探中,为了避免因地表障碍物使地震反射剖面出现间断现象,需要改变观测系统设计,跨越障碍物(江河、城镇等),以保证反射同相轴能连续追踪对比。在以往地震勘探中,有时因过障碍观测系统设计不合理,不但增加勘探费用,而且影响采集质量。因此只有科学合理地设计过障碍观测系统模式和参数,才能保证地震测线顺利通过障碍物,得到较好的障碍物下方的地震资料并降低勘探成本。为此本文在调查和研究大量野外实际的过障碍观测系统的基础上,总结归纳成三大类过障碍观测系统模式,并分析其特点和应用范围。采用图解法,推导出主要模式的跨越宽度、最小炮检距及最大炮检距等参数公式。采用这套过障碍观测模式不仅可以得到和障碍区两侧等质量的地震资料,而且可以有效地降低勘探成本。     

Selective oxidation of alcohols using octahedral molecular sieves: influence of synthesis method and property–activity relations

Manganese oxides having a tunnel structure (OMS-2) have been utilized as selective catalysts for alcohol oxidation. In this study manganese oxide catalysts were synthesized in different media and modified by exchanging the tunnel cation by H⁺, using acid treatment or exchanging with NH₄⁺ followed by thermolysis. Various alcohol oxidations were performed using these catalysts to ascertain the influence of synthesis method on their activity. A correlation is made between lattice oxygen instability and activity of the catalysts, which indicates involvement of the lattice oxygen in the mechanism. The exchange of the tunnel cation with the smaller H⁺ ions leads to weakening of the Mn–O bond, as verified by temperature programmed desorption (TPD) results. Only the chemisorbed oxygen on the surface (O⁻) and the lattice oxygen in the layers close to the surface is involved in the oxygen transfer during the reaction.     

己二酸二乙酯合成新工艺的研究

本文以离子交换树脂作为液固相酯化反应的催化剂 ,甲苯作为带水剂 ,合成己二酸二乙酯。应用本法 ,酯化反应产率高达 78%。同时对影响产率的诸因素进行了考察 ,其最佳反应条件为 :酸醇摩尔比 1∶4 ,催化剂用量为酸质量的 2 5 % ,反应时间为 10小时 ,反应温度 86～ 87℃ ,催化剂重复使用 4次 ,未出现活性明显下降 ,此工艺操作简单 ,反应条件温和 ,产率高 ,具有显著的工业应用价值。     

一个面积和功耗优化且适用于10/100 Base-T以太网的CMOS时钟恢复电路

提出了一个新的用于10 / 10 0 Base- T以太网中面积和功耗优化的时钟恢复电路.它采用双环路的结构,加快了锁相环路的捕获和跟踪速度;采用复用的方式,通过选择信号控制电路可分别在10 Mbps或10 0 Mbps模式下独立工作且能方便地实现模式间的互换,与采用两个独立的CDR电路相比节省了一半的面积;同时,电路中采用一般的延迟单元来取代DL L,并能保证环路性能不随工艺温度等条件引起的延迟单元、延迟时间的变化而变化,从而节省了功耗.Hspice模拟结果显示,在Vdd=2 .5 V时,10 0 Mbps模式下电路的功耗约为75 m W,稳态相差为0 .3 ns;10 Mbps模式时电路功耗为5 8m W     

Novel aspects of the microstructure of PP/PA blends prepared by reactive compounding as studied by microhardness

The microhardness of injection-moulded i-polypropylene/polyamide (iPP/PA) blends prepared by reactive compounding was determined. The formulation rules and processing technology for the preparation of these alloys was reported previously. iPP/PA compositions between 100/0 and 50/50 using functionalized PP with various degrees of mainchain grafting, were investigated. It is shown that the deviation of microhardness from the additivity law of the single components is mainly due to a decrease in the crystallinity of the iPP phase. The results are discussed in the light of the microstructural variations as revealed by X-ray diffraction methods.     

(Nb,Ti)C的制备方法对(Nb,Ti)C-35Ni金属陶瓷的微观结构及性能的影响

用自蔓燃高温合成（SHS）技术及电弧熔融法制备的（Nb，Ti）C固溶体作基体，制备（Nb，Ti）C－35Ni金属陶瓷。结果表明用电弧熔融法制备的（Nb，Ti）C为基的试样具较优的室温力学性能（σ＝1630MPa，KIC＝18．0MPa），其陶瓷颗粒均匀分行粘结相之中并是包裹结构；而用SHS法制备的（Nb，Ti）C为基的试样其力学性能相对较差，其陶瓷颗粒无包裹结构．