包核为H2O2的超声造影剂研究

以双氧水为包核 ,以卵磷脂 ( PC) ,二肉豆蔻酰磷脂酰胆碱 ( DPPC) ,司盘 6 0 ( Span 6 0 ) ,吐温 6 0 ( Tween6 0 )等为膜材 ,用逆相蒸发法或超声法制备了 12种囊泡 ,其平均直径在 0 .1～ 3μm范围内 .研究了囊泡的包封率、形状以及尺寸大小随时间变化的情况 .实验结果表明采用逆相蒸发法制得的囊泡稳定性较好 ;而膜材不同 ,囊泡的稳定性也有明显的差别 .选取包封率较高的一种囊泡 ,在 37℃ ,过氧化氢酶存在下测定了 H2 O2 的释放速率 .将部分囊泡通过静脉注射到家兔体内 ,观察到其肝部位的超声波信号有明显增强     

用正电子湮没研究Fe(Ⅲ)在γ-Al2O3载体中的自发扩散

采用机械混合的方法,将Fe(NO3)3·9H2O加载于多孔γ-Al2O3载体,并利用正电子湮没寿命谱学研究其自发扩散过程.实验测量了不同Fe(Ⅲ)质量分数的样品(1.3%～4.2%)在不同温度(100～600 C)烘烤后的正电子寿命谱.实验结果表明,未烘烤时,Fe(Ⅲ)主要分布在γ-Al2O3载体颗粒表面;烘烤后,Fe(Ⅲ)向γ-Al2O3载体颗粒的内部二次孔扩散,并首先占据活性中心的位置.同时,部分Fe(Ⅲ)扩散到γ-Al2O3载体的微孔中.在烘烤温度大于400℃时,能使Fe(Ⅲ)在γ-Al2>O3载体中均匀分布.     

基于多种约束条件的维修备件库存优化方法研究

考虑了维修备件需求的随机性,以装备可用度、完好率置信度以及维修备件的保障程度为约束条件,运用概率论与数理统计方法,将维修备件保障费用达到最小值确定为目标函数,在此基础上,制定维修备件库存的最优方案,并通过示例验证了该方法的有效性和科学性.方法可以为其它相关领域解决物资库存与费用问题提供理论依据.     

A novel P-channel SOI LDMOS structure with non-depletion potential-clamped layer

A novel structure is proposed for doubling the vertical breakdown voltage of silicon-on-insulator(SOI) devices. In this new structure, the conventional buried oxide(BOX) in an SOI device is split into two sections: the source-section BOX and the drain-section BOX. A highly-doped Si layer, referred to as a non-depletion potential-clamped layer(NPCL), is positioned under and close to the two BOX sections. In the split BOXes and the Si region above the BOXes, the blocking voltage(BV) is divided into two parts by the NPCL. The voltage in the NPCL is clamped to be nearly half of the drain voltage. When the drain voltage approaches a breakdown value, the voltage sustained by the source-section BOX and the Si region under the source are nearly the same as the voltage sustained by the drain-section BOX and the Si region under the drain. The vertical BV is therefore almost doubled. The effectiveness of this new structure was verified for a P-channel SOI lateral double-diffused metal-oxide semiconductor(LDMOS) and can be applied to other high-voltage SOI devices. The simulation results show that the BV in an NPCL P-channel SOI LDMOS is improved by 55% and the specific on-resistance(Ron,sp) is reduced by 69% in comparison to the conventional structure.     

Network analysis and spatial agglomeration of China’s high-speed rail: A dual network approach

China has the largest high-speed railway(HSR) system in the world, and it has gradually reshaped the urban network.The HSR system can be represented as different types of networks in terms of the nodes and various relationships(i.e.,linkages) between them. In this paper, we first introduce a general dual network model, including a physical network(PN)and a logical network(LN) to provide a comparative analysis for China’s high-speed rail network via complex network theory. The PN represents a layout of stations and rail tracks, and forms the basis for operating all trains. The LN is a network composed of the origin and destination stations of each high-speed train and the train flows between them. China’s high-speed railway(CHSR) has different topological structures and link strengths for PN in comparison with the LN. In the study, the community detection is used to analyze China’s high-speed rail networks and several communities are found to be similar to the layout of planned urban agglomerations in China. Furthermore, the hierarchies of urban agglomerations are different from each other according to the strength of inter-regional interaction and intra-regional interaction, which are respectively related to location and spatial development strategies. Moreover, a case study of the Yangtze River Delta shows that the hub stations have different resource divisions and are major contributors to the gap between train departure and arrival flows.     

找点,从分类开始

“等腰三角形”这一节内容中,常会遇到一类找点使其构成等腰三角形的问题.在解题中常会遗漏部分点或找不出具有如此性质的点.究其原因是多方面的,但其中最为重要的一点是:同学们仍未完全学会运用“分类”的数学思想来解决问题.下面几例的解答定会对同学们有所启示。     

流动注射离子交换分离-火焰原子吸收光谱法连续测定铁的形态

研究了一种以NH4F为掩蔽剂掩蔽Fe(Ⅲ),用732型阳离子交换树脂(CSR)吸附Fe(Ⅱ),从而分离测定Fe(Ⅲ)与Fe(Ⅱ)的试验体系。设计了一套新颖的用于该体系的全自动流动注射流路,实现了Fe(Ⅲ)与Fe(Ⅱ)的连续测定。Fe(Ⅲ)和Fe(Ⅱ)的相对标准偏差(n=7)分别为3.37%和1.95%,检出限分别为0.07和0.01 mg.L-1,分析速度为25个样/h。     

低温碳化法制备高分散性纳米碳酸钙的研究

以石灰石为原料,采用低温碳化法制备了高分散性纳米碳酸钙。通过XRD、SEM、TEM等对纳米碳酸钙样品进行表征,考察了浆料比、碳化温度、CO₂通气速率、陈化时间、晶型控制剂对纳米碳酸钙粒径和分散程度的影响。研究结果表明,制备纳米碳酸钙的最佳工艺条件为：浆料比为5%,碳化温度为15℃,CO₂通气速率为200 mL/min,陈化时间2 h,并选用ZnCl₂为添加剂。在此条件下,制得晶粒尺寸为25～35 nm、分布均匀的立方体状纳米碳酸钙。结合Materials Studio对纳米碳酸钙的生长机理进行了分析,结果表明：碳酸钙的(104)和(116)2个晶面具有热力学稳定性,最终会成为顽强显露的晶面,促使生成立方体型纳米碳酸钙。     

柱状Co_3O_4催化剂的乏风催化燃烧性能（英文）

通过两步法成功合成了由纳米粒子组装成的柱状Co_3O_4。第一步是通过简单的冷凝回流法合成柱状CoC2O4·2H2O。第二步将所制备的柱状CoC2O4·2H2O在350℃下煅烧2 h,使其分解形成Co_3O_4而不破坏原始形貌。通过粉末X射线衍射(PXRD),X射线光电子能谱(XPS),氮气吸附-脱附,扫描电镜(SEM),高分辨率透射电子显微镜(HRTEM)和H2程序升温还原(H2-TPR)表征柱状Co_3O_4的物化性质。结果表明,柱状Co_3O_4对乏风甲烷燃烧的催化活性远远高于商业Co_3O_4。柱状Co_3O_4优异的催化性能可能归因于其表面较高的Co3+含量,较高的表面吸附氧和大量暴露的{111}晶面族。     

以ACF为模板制备掺氮TiO2及其光催化脱氨氮研究

本文采用溶胶-凝胶法制备了以活性炭纤维(ACF)为模板的掺氮TiO2光催化剂,利用XRD、XPS、TEM、SEM和UV-Vis等方法对催化剂进行了表征,测定了催化剂在紫外、日光照射下光催化脱氨氮的活性.ACF作模板掺氮TiO2催化剂具有介孔结构,平均粒径约为10 nm,比表面积为64.43 m2/g.紫外、可见光光催化2 h氨氮(85 mg/L)废水的氨氮去除率分别为68%和47%.结果表明,催化剂中氮的含量是影响催化剂光催化活性的重要因素.