多孔氧化铝模板催化制备定向碳纳米管阵列

Well-aligned open-ended multi-walled carbon nanotube (MWCNT) arrays were prepared via chemical vapor deposition (CVD) method in porous anodic aluminum oxide (AAO) templates without depositing any transition metals as catalyst. Effects of the CVD temperature and heat treatment were studied in detail.Well-aligned open-ended MWCNT arrays were obtained at the CVD temperature above 600 ℃; when CVD temperature is reduced to around 550 ℃, CNTs, CNFs and other structures existed at the same time; no CNTs or carbon nanofibres (CNFs) could be found as the CVD temperature is below 500 ℃, and only amorphous carbon in the porous AAO template was found. Experimental results showed that the AAO template is catalytic during the CVD process, and it has the following two effects: to catalyze thermal decomposition of acetylene and to catalyze conversion of carbon decomposed from acetylene into CNTs or CNFs. Heat treatment could improve the graphitization degree, but it might also introduce new defects.     

一种小型化超宽带单极子短波天线设计

短波天线不仅要求超宽带(3～30 MHz),并且由于存在尺寸庞大的难题,对天线的小型化和结构简洁有苛刻要求.提出了一种金属线结构的新型单极子短波天线,结构简洁,通过分形辐射振子和T型馈电结构获得超宽工作频带和小型化性能,同时还能够调整天线姿态实现全向或定向辐射,以及一定程度上改变天线波束指向仰角.为验证设计的有效性,加...     

新型阶梯变掺杂SiC漂移阶跃恢复二极管

漂移阶跃恢复二极管(DSRD)一般应用于超宽带脉冲信号源,可以将纳秒级高压脉冲换向负载,这对于输出脉冲的上升前沿有很高的要求.文章提出了一种具有基区变掺杂的新型宽禁带材料漂移阶跃恢复二极管,将传统的基区掺杂变为阶梯式的浓度分布,基区内形成由浓度差导致的内建电场,该内建电场在DSRD放电回路反向泵浦阶段调节载流子分布,并...     

Effect of surface oxygen vacancy defects on the performance of ZnO quantum dots ultraviolet photodetector

The slower response speed is the main problem in the application of ZnO quantum dots (QDs) photodetector, which has been commonly attributed to the presence of excess oxygen vacancy defects and oxygen adsorption/desorption processes. However, the detailed mechanism is still not very clear. Herein, the properties of ZnO QDs and their photodetectors with different amounts of oxygen vacancy (V_O) defects controlled by hydrogen peroxide (H₂O₂) solution treatment have been investigated. After H₂O₂ solution treatment, V_O concentration of ZnO QDs decreased. The H₂O₂ solution-treated device has a higher photocurrent and a lower dark current. Meanwhile, with the increase in V_O concentration of ZnO QDs, the response speed of the device has been improved due to the increase of oxygen adsorption/desorption rate. More interestingly, the response speed of the device became less sensitive to temperature and oxygen concentration with the increase of V_O defects. The findings in this work clarify that the surface V_O defects of ZnO QDs could enhance the photoresponse speed, which is helpful for sensor designing.     

改进遗传算法应用于超低副瓣天线阵的综合设计

提出了一种改进的遗传算法.在同一代中对各个个体采用不重复交叉和不重复变异的策略和分别在交叉和变异后采用精英保留的策略,并改进了自适应规则.将该算法应用于实现线阵超低副瓣方向图.将各个天线单元的电流幅度和单元间距作为参量进行优化.给出了线阵天线单元在不同单元个数和不同间距条件下的优化结果.结果表明,该改进的遗传算法能够优化实现低于-40dB的超低副瓣,优于已有文献中遗传算法对天线阵副瓣的综合设计结果.     

车载红外图像的行人检测与跟踪技术

针对车载红外图像的特点,采用基于区域估计的帧差法实现车载红外图像中的行人检测,再通过行人的几何特征和运动速率特征进行行人的识别,最后运用轮廓矩匹配算法进行行人的跟踪。实验结果表明所采用的方法具有较好的行人检测及跟踪效果。     

基于多层介质覆盖层的高增益Fabry-Perot天线设计

提出一种由不同厚度和不同面积的多层介质板叠加制作多层介质覆盖层,代替传统单层介质覆盖层,提高Fabry-Perot(F–P)谐振腔天线增益和口径效率的设计方法。以工作频点5.8 GHz的F–P谐振腔天线设计为例,采用微带贴片天线作为馈源,由多层厚度分别为1 mm,1 mm和1.5 mm,直径分别为160 mm,130 mm和120 mm,相对介电常数为16的聚四氟乙烯介质板叠加制作该天线覆盖层。天线样品的测试结果与设计仿真结果吻合良好。与传统单层介质覆盖层相比,该多层介质覆盖层将工作频率5.8 GHz处天线增益由18.2 dBi提高到19.1 dBi,相应口径效率由70.02%增加到86.14%,天线|S11|<-10 dB阻抗带宽和3 dB增益带宽略有提高,分别达到8.19%和11.90%。     

连续氢化物发生端视ICP-AES法测定水中痕量硒和汞

报道了用自制的在线氢化物连续发生装置,应用端视ICP-AES法测定水中痕量硒和汞。不需要专用氢化物发生装置,分析成本低。在完成非氢化法测定或氢化法测定时不需拆卸或安装。方法简便、快速。测定水中硒和汞的测定,其检出限分别为2×10-4和1×10-4mg·L-1。     

丙烯酸β-羧乙酯-苯乙烯共聚物缩合异烟肼的合成及其水解释放研究

<正> 大分子载体药物是精细高分子合成的一个重要研究领域,作为药物载体的大分子骨架需有良好的生物相容性及控制释放能力。本文采用具有较长柔性侧支链的丙烯酸β-羧乙酯(APA)-苯乙烯(St)共聚物作载体,并通过羧基与抗结核药物异烟肼反应,制备出毒性较低并能控制释放的大分子载体异烟肼药物。     

新型1,2,3-三唑类化合物的合成及抗菌构效关系

根据活性基团拼接原理, 以4-取代-苯胺为原料, 经重氮化、 关环和缩合反应合成了17个化合物1-(4-取代苯基)-5-取代苯基亚氨基-4-取代-1,2,3-三唑(7a~7c和13a~13d)和1-(4-取代苯基)-5-取代苄基氨基-4-取代-1,2,3-三唑(5a~5c, 10a~10c和14a~14d), 其中化合物5a~5c, 7b, 7c, 10a, 10c, 13b~13d和14b~14c为新化合物, 对所制备化合物的结构进行了表征. 生物活性测试结果表明, 所有化合物均表现出一定的抑菌活性, 对大肠杆菌的抑菌活性均优于氟康唑; 化合物7a和10c对金黄色葡萄球菌的抑制活性明显优于氟康唑; 而化合物13a和13d则对白色念球菌表现出良好的抑制活性, 与三氯生相当.