Effect of additives introduced by ball milling on sintering behavior and mechanical properties of hot-pressed B4C ceramics

The ball-milling process is a usual route employed to break up agglomerates in the powder or mix the powder with additives when preparing ceramics. Although it is well known that a powder can be “contaminated” by the wear particles from the milling balls, the study dealing with how the preparation and properties of a hard material would be affected by additives just introduced by scrape of milling balls has been scarce. In the present work, sintering behavior and mechanical properties of hot-pressed B₄C with additives derived from milling balls were investigated. Polyoxymethylene, ZrO₂, Al₂O₃ and Si₃N₄ were selected as different ball materials. The results show that the sinterability of B₄C could be significantly enhanced because of the incorporation of one of these additives, i.e. ZrO₂, Al₂O₃ and Si₃N₄ (approximately 3–6 vol%). As a result of improvement in density, excellent mechanical properties of B₄C ceramics were obtained. Among them a flexural strength of B₄C added by ZrO₂ reached 630 MPa.     

铋掺杂铝硅酸盐玻璃的超宽带近红外发光性质

采用高温熔融法制备了组分为50SiO_2-xAl_2O_3-(50-x)MgO-Bi_2O_3(x=5,10,15,20,摩尔比)的铋掺杂铝硅酸盐玻璃。研究了铋掺杂铝硅酸盐玻璃超宽带近红外发光性质,探讨了玻璃基质的光学碱度对铋离子宽带发光特性的影响。结果表明:在690nm和808nm的激发下,铋掺杂铝硅酸盐玻璃的红外荧光中心分别位于1106nm和1294nm;随光学碱度的增强,铋离子的红外发光强度减弱。并对铋离子超宽带发光的机理进行了探讨,认为其红外发光源于低价的Bi~+和Bi~(2+)。     

Comparative study of colour yield of cotton knitted fabric made by torque‐free ring‐spun yarns

Torque‐free ring spinning is a new spinning technology that has produced yarns with low twist and balanced torque. In this study, a commercially torque‐free ring‐spun yarn, namely Estex yarn, with three types of cotton fibre, i.e. Pima, upland and organic cotton, were used. Cotton fabric samples were knitted with Estex yarns and conventional ring‐spun yarns. The fabric samples were then dyed with two reactive dyes, Remazol Black B and Remazol Brilliant Blue R Spec., and the fabric dyeability was measured in terms of reflectance and colour yield. Finally, the results were analysed using the statistical software package SPSS and the results revealed that fabric samples manufactured by Estex yarns could achieve a better colour yield than conventional ring‐spun fabric samples. In addition, the Pima cotton gave the best colour yield, followed by upland cotton and organic cotton.     

面向产品概念设计的知识网络模型

产品的概念设计对其最终设计结果具有重要的影响。提出了支持产品概念设计的知识网络模型,通过该模型将显性知识进行组织,以支持产品需求转换为产品功能,进而转换为产品结构的概念设计过程,并根据模型对产品参数间的隐性联系进行挖掘,使其转换为显性知识以支持重用。通过对某工业汽轮机转子通流部分设计过程的知识网络应用过程给出实例论证。     

某新型导弹发射车机械检修系统设计

介绍某新型导弹发射车机械检修系统的设计思想,重点讨论了系统硬件和软件的实现方法。系统采用无线通信方式,实现了远距离的宏观调控;采用二级模块结构形式,实现了系统的模块化,提高了系统的可扩展性和可维护性。     

Formulation, quality control and shelf life of the experimental cytostatic drug cyclopentenyl cytosine

This paper describes the formulation and quality control of an aqueous sterilized formulation of the experimental cytostatic drug cyclopentenyl cytosine (CPEC) to be used in Phase I/II clinical trials. The raw drug substance was extensively tested. A High Pressure Liquid Chromotography (HPLC) method was validated for the quality control of the formulated product. The aqueous formulation was found to be stable for at least 2 years at 2-8°C. Sterilization (15 min at 121°C) showed no influence on drug stability. The results show that CPEC can be formulated in an aqueous solution. The described HPLC method is a useful tool in the pharmaceutical quality control.     

Carbon dispersed iron-manganese catalyst for light olefin synthesis from CO hydrogenation

High performance iron-manganese catalysts dispersed with carbon to produce light olefins from CO hydrogenation were prepared by sol-gel method using citric acid as precursor. The effects of carbon content on the bulk structure, the water gas shift reaction, the chain propagation ability and the activity and selectivity of the catalysts were investigated. The results showed that the catalysts were gradually reduced during the decomposition of the precursor when calcined under pure N₂. The formation of iron-manganese mixed crystallites was favored and stabilized because of the enhanced interaction of iron and manganese with increasing carbon content. During the subsequent CO hydrogenation reaction, all the catalysts showed high activity and olefin selectivity. With increasing carbon content, the water gas shift (WGS) reaction was restrained and the chain propagation ability was inhibited. Catalysts with higher carbon content showed much lighter hydrocarbon products; however, the selectivity of CH₄ was almost unchanged. This work was presented at the 7 ^th Korea-China Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

ZrB2-SiC复相陶瓷的制备及其力学性能研究

以ZrB2和SiC粉为原料,采用Si3N4球为球磨介质,通过热压烧结制备了ZrB2-SiC复相陶瓷.并对ZrB2-SiC复相陶瓷进行了相对密度、力学性能检测和微观结构分析.结果表明:随着ZrB2球磨时间和SiC含量的增加,该复相陶瓷相对密度先增加后略有降低,ZrB2最佳球磨时间为8小时,SiC最佳含量为20vol.%.ZrB2+20vol.%SiC复相陶瓷的相对密度达到98.3%,抗弯强度达到631±4MPa,断裂韧性达到5.4±0.2 MPa·m1/2.随着球磨时间的增加,ZrB2+20vol.%SiC复相陶瓷的断裂方式由穿晶断裂向沿晶断裂转变.     

浸没式双轴旋转厌氧膜生物反应器的污泥特性研究

研究了新型浸没式双轴旋转厌氧膜生物反应器(SDRAnMBR)处理模拟啤酒废水的污泥特性.结果表明,SDRAnMBR的污泥活性高,旋转剪切力没有对厌氧颗粒污泥的性质造成破坏并具有性能良好的絮体;而且能有效减轻污泥浓度、EPS、污泥粘度,污泥颗粒粒径的变化对膜污染的影响,使之能在较高的MLSS(18～19.5 g·L-1),较高的EPS浓度(50.9～63.9 mg·gMLSS-1)、较小的污泥颗粒粒径(4.00～36.54μm)和较大的污泥粘度(6.6～7.5mPa·s-1)时稳定运行.SDRAnMBR中由膜旋转形成的三相旋转流和厌氧颗粒污泥的协同作用,使SDRAnMBR具有性能良好的活性污泥,同时强化了膜组件的抗污染性能.     

速度·活力·梦想——浅谈高速铁路客运枢纽影响下城市地区的发展策略

借鉴外国的成功经验,结合我国实际情况,寻找合适的高速铁路客运枢纽影响下城市地区发展策略,已经成为城市规划与设计研究的当务之急。该文简要分析了日本东京新宿和法国里尔两个成功案例,总结了若干发展策略,希望能引起大家进一步的关注、研究和讨论。