反胶束萃取氨基酸的研究

综述了反胶束萃取氨基酸的研究进展,包括反胶束萃取氨基酸机理及应用.其机理为:氨基酸以带电离子状态进入反胶束的"水池" 内或微胶团球粒的界面分子膜层内而被分离,氨基酸离子与形成反胶团的表面活性剂离子间的静电作用越强,氨基酸的萃取率越高,水溶液中盐浓度越大,氨基酸萃取率越低.由2-乙基己基琥珀酸酯磺酸钠(AOT)阴离子表面活性剂和三辛基甲基氯化铵(TOMAC)季铵盐阳离子表面活性剂形成的反胶束适用于低盐浓度的氨基酸料液,如从发酵液中萃取分离苯丙氨酸,二 (2-乙基己基)磷酸铵表面活性剂形成的反胶束可用于从高盐浓度的胱氨酸母液中萃取分离出精氨酸.介绍了反应条件对反胶束萃取氨基酸的影响.     

紫外光固化酚醛树脂的制备及在涂附磨具中的应用

本文通过丙稀酸与环氧酚醛树脂开环反应,制备出能紫外光固化的酚醛树脂结合剂,研究了制备该树脂的合适工艺条件为:催化剂N,N-二甲基苯胺的用量为体系总质量的1%,反应温度为80±5℃,反应时间为5~7h;用这种可紫外光固化的酚醛树脂制作的涂附磨具试样,不仅固化速度快,仅需4~5m in即可固化完全,而且磨削比是常规热固化试样的3倍多,使用性能大大提高。     

Influence of polymerization conditions on the structure and properties of polyethylene/polypropylene in‐reactor alloy synthesized in the gas phase with a spherical Ziegler–Natta catalyst

A spherical TiCl₄/MgCl₂‐based catalyst was used in the synthesis of in‐reactor polyethylene/polypropylene alloys by polyethylene homopolymerization and subsequent homopolymerization of propylene in the gas phase. Different conditions in the ethylene homopolymerization stage, such as monomer pressure and polymerization temperature, were investigated, and their influences on the structure and properties of in‐reactor alloys were studied. Raising the polymerization temperature is the most effective way of speeding up polymerization and regulating the ethylene content of polyethylene (PE)/polypropylene (PP) alloys, but it will cause a greater increase in the PE‐b‐PP block copolymer fraction (named fraction D) than in the fraction of PP‐block‐PE in which the PP segments have low or medium isotacticity (named fraction A). Although changing ethylene monomer pressure could influence the ethylene content of PE/PP alloys slightly, it is an effective way of regulating the structural distribution. Reducing the monomer pressure will evidently increase fractions A and D. The mechanical properties of the alloys, including impact strength and flexural modulus, can be regulated in a broad range with changes in polymerization conditions. These properties are highly dependent on the amount, distribution, and chain structure of fractions A and D. The impact strength is affected by both fraction A and fraction D in a complicated way, whereas the flexural modulus is mainly determined by the amount of fraction A. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2136–2143, 2006     

WC-Co硬质合金的相转变

用高温 X射线衍射装置对低碳 WC- 2 0 Co合金混合料进行了从室温到130 0℃连续升温过程的动态相转变研究。结果表明 ,以低碳 WC粉为原料的 WC- Co系合金在真空烧结升温过程中是通过钨和碳原子的扩散作用消耗原料中的游离态钴和WC(90 0℃以下是 W2 C和单质钨 )进行的脱碳型不平衡相转变。除 90 0℃以下由原料中的 W2 C(和单质钨 )及游离态钴生成η1 相外 ,10 0 0℃以上升温过程中生成的高温相η化合物和金属间化合物与原料中固有的 W2 C(和单质钨 )含量无关 ,也与钴的同素异构相变无关。烧结降温期间高温相通过增碳作用平衡转变成游离态钴和 WC,室温合金中的η1 相含量完全取决于原料中 W2 C(和单质钨 )的含量     

六自由度微动平台旋转自由度的设计

介绍六自由度微动平台的原理、结构;对旋转自由度的实现进行了设计;同时对旋转自由度的调整精度进行了分析。这种形式的六自由度微动平台具有系统简单,可操作性强,实时监控调节,性价比高等优势。     

基于软模法制备1-3型压电复合材料及高频医用超声换能器

高频医用超声成像技术因其高空间分辨率而被广泛应用于人体组织的精细结构观察,其中高频超声换能器的核心材料是1-3型压电复合材料。采用软模板法直接烧结了锆钛酸铅(PZT)压电微柱阵列,进而制备PZT/环氧1-3型压电复合材料,并对其进行了微观结构观察和电学性能表征。材料微观结构完整,机电耦合系数达到0.64。采用此复合材料制备了中心频率为20 MHz的高频超声换能器。采用脉冲回波法对换能器进行了性能和声场测试,并利用其对人体皮肤进行了超声成像,换能器的插入损耗、带宽分别为13.1 dB和84.2%。结果表明,软模法制备的1-3型压电复合材料能使高频超声换能器兼具低插入损耗和大带宽,这为高性能高频医用超声换能器提供了一种低成本、高效率的商业化制备方法。     

Ultraprecise 3D Printed Graphene Aerogel Microlattices on Tape for Micro Sensors and E-Skin

3D printed graphene aerogels hold promise for flexible sensing fields due to their flexibility, low density, conductivity, and piezo-resistivity. However, low printing accuracy/fidelity and stochastic porous networks have hindered both sensing performance and device miniaturization. Here, printable graphene oxide (GO) inks are formulated through modulating oxygen functional groups, which allows printing of self-standing 3D graphene oxide aerogel microlattice (GOAL) with an ultra-high printing resolution of 70 µm. The reduced GOAL (RGOAL) is then stuck onto the adhesive tape as a facile and large-scale strategy to adapt their functionalities into target applications. Benefiting from the printing resolution of 70 µm, RGOAL tape shows better performance and data readability when used as micro sensors and robot e-skin. By adjusting the molecular structure of GO, the research realizes regulation of rheological properties of GO hydrogel and the 3D printing of lightweight and ultra-precision RGOAL, improves the sensing accuracy of graphene aerogel electronic devices and realizes the device miniaturization, expanding the application of graphene aerogel devices to a broader field such as micro robots, which is beyond the reach of previous reports.     

高速铁路的GSM-R无线传播模型校正

为了提高在铁路沿线复杂地形环境下的Hata模型准确度,在研究GSM-R系统中的电波传播预测Hata模型的基础上,提出了一种对Hata传播模型的校正方法。结合郑西实测线路数据对市郊、平原和山区三种地形环境下进行校正,得到了不同地形下的Hata校正模型。通过对校正前后模型的误差对比,校正后的Hata传播模型准确度有显著提高。     

自适应模糊粒子群算法求解IT服务优化选择问题

为了解决IT服务选择问题,提出了一种基于自适应模糊粒子群算法的IT服务优化选择方法。首先,针对业务流程对IT服务的需求,建立了以响应时间、执行费用、可靠性、可用度为目标的IT服务优化选择模型。然后,设计了求解模型的粒子群优化算法,应用模糊推理规则,自适应调整粒子进化过程中的自身学习因子和全局学习因子,以提高粒子收敛速度和全局搜索能力,从而获取了满足业务流程QoS约束的较优IT服务单元。最后以算例验证了模型及算法的可行性和有效性。     

反求工程图像采集系统的设计

随着RP行业的迅速发展,反求工程在快速成型制造系统中的作用日益重要。图像采集系统的设计是反求工程设计的核心部分。该文对反求工程的产生、发展现状与它在快速成型制造中的重要作用做了简要介绍,并着重对反求工程中图像采集系统的测量原理及其软、硬件设计进行了详细全面的论述。