ZnO纳米管的制备及光学特性研究

ZnO nanotubes have been fabricated through a carbon thermal reduction deposition process. Structure characterization results show that the ZnO nanotubes have a single crystalline wurtzite hexagonal structure pref- erentially oriented in the c-axis. The diameters of ZnO nanotubes are in the range of 90-280 nm and the wall thickness is about 50-100 nm. Room-temperature photoluminescence measurements of the ZnO nanotubes exhibit an intensive ultraviolet peak at 377 nm and a broad peak centered at about 517 nm. The UV emission is caused by the near band edge emission while the green emission may be attributed to both oxygen vacancy and the surface state. Raman and cathodoluminescence spectra are also discussed. Finally, a possible growth mechanism of the ZnO nanotubes is proposed.     

除臭微生物在污水处理厂中的应用

污水处理厂中的臭气污染是城市环境污染的重要来源,除臭技术的研究与应用已经成为一个热点。微生物除臭技术以其独特的优势而广泛应用于污水处理厂的臭气处理工程中。介绍污水处理厂臭气的成分、来源及微生物除臭技术的原理,探讨各类微生物在除臭技术中的应用情况,最后概述微生物除臭技术存在的问题及其研究方向。     

微生物在烟气脱硫中的应用研究

雾霾天气与酸雨的产生与含硫燃料的燃烧密切相关,脱硫技术的研究与应用已经成为一个热点。脱硫微生物用于烟气脱硫具有廉价、低耗和无二次污染的优势,倍受环保行业的关注。介绍烟气脱硫技术的现状,综述微生物脱硫技术的原理以及微生物类群特点,探讨该技术未来的研究方向,以期为该领域的研究者提供参考。     

基于神经网络与遗传算法结合的硝化细菌发酵培养基优化(英文)

Two artificial intelligence techniques, artificial neural network and genetic algorithm, were applied to optimize the fermentation medium for improving the nitrite oxidization rate of nitrite oxidizing bacteria. Experiments were conducted with the composition of medium components obtained by genetic algorithm, and the experimental data were used to build a BP (back propagation) neural network model. The concentrations of six medium components were used as input vectors, and the nitrite oxidization rate was used as output vector of the model. The BP neural network model was used as the objective function of genetic algorithm to find the optimum medium composition for the maximum nitrite oxidization rate. The maximum nitrite oxidization rate was 0.952 g 2 NO-2-N·(g MLSS)-1·d-1 , obtained at the genetic algorithm optimized concentration of medium components (g·L-1 ): NaCl 0.58, MgSO 4 ·7H 2 O 0.14, FeSO 4 ·7H 2 O 0.141, KH 2 PO 4 0.8485, NaNO 2 2.52, and NaHCO 3 3.613. Validation experiments suggest that the experimental results are consistent with the best result predicted by the model. A scale-up experiment shows that the nitrite degraded completely after 34 h when cultured in the optimum medium, which is 10 h less than that cultured in the initial medium.     

对虾养殖水体氨氧化菌的多样性分析与硝化作用的特征

为了研究珠三角地区不同空间分布的对虾养殖水体中氨氧化菌多样性的异同与探究养殖水体中氨氧化菌的硝化作用特征,应用PCR-DGGE技术,结合非加权算术平均法(UPGMA)聚类分析和多维尺度分析(MDS)的方法,对珠三角地区7个对虾养殖场的水样中氨氧化菌的多样性进行对比分析,继而构建了模拟养殖生态系统,评估了系统中微生物的硝化能力和硝化作用特征。结果表明:在养殖水体中,氨氧化古菌的类别明显少于氨氧化细菌,各样品间相似性较低,为41%到80%,没有高相似性的聚类;模拟系统中存在连续完整的亚硝化与硝化作用。     

GaN HEMT外延材料表征技术研究进展

氮化镓(GaN)作为第三代半导体材料的典型代表,具有高击穿电场强度和高热导率等优异的物理特性,是制作高频微波器件和大功率电力电子器件的理想材料.GaN外延材料的质量决定了高电子迁移率晶体管(HEMT)的性能,不同材料特征的表征需要不同的测量工具和技术,进而呈现器件性能的优劣.综述了GaN HEMT外延材料的表征技术,详细介绍了几种表征技术的应用场景和近年来国内外的相关研究进展,简要总结了外延材料表征技术的发展趋势,为GaN HEMT外延层的材料生长和性能优化提供了反馈和指导.     

基于三角块拼接模型的等高线绘制算法

等高线是空间数据分析的重要工具,在各类工程中有着广泛的应用。借鉴分而治之的经典算法思想,提出了一种基于三角块拼接模型的等高线绘制算法。该算法首先将各个高程数据对应的离散点,按照优化组合的顺序构建为一系列独立三角块,其次在每个单独的三角块上绘制其局部等高线,最后基于独立三角块共边特性将其自动拼接成对应的整体等高线。实验结果表明,该算法不仅具有简单、高效等优点,而且处理结果较为客观、准确。     

不同热处理时间下TaC_p/Fe复合材料的组织演变

研究了不同热处理时间下碳化钽增强铁基复合材料的组织演变规律。应用XRD、SEM以及EDS等手段分析了反应层的显微结构,同时研究了反应层的动力学。实验结果表明,钽丝与灰铸铁之间的反应层为碳化钽。随着热处理时间增加,碳化钽层厚增加。当保温时间为5、7、10和15 min时,反应层厚度分别为3.81、5.59、9.32和11.44μm。经过计算,1100℃时的扩散系数为1.089×10~(-8 )cm~2/s。最后,给出了不同热处理时间下组织演变示意图,对其演变规律做了进一步解释。     

四角状氧化锌纳米结构的发光特性研究

The tetrapod ZnO nanostructures are synthesized on the Si （100） substrates using the chemical va- por deposition （CVD） method at 1000 ℃. Each nanostructure has four arms which are about 3-10 μm in length and 0.2-1.5 μm in diameter. Further analyses on structure demonstrate that the tetrapod ZnO nanostructures have single crystalline wurtzite hexagonal structure preferentially oriented in c-axis. The photoluminescence （PL） mea- surements of the tetrapod ZnO nanostructures revealed a UV peak at 382 nm corresponding to the free exciton emission, and a green peak at 523 nm arising from deep level emission. For comparative analysis, cathodolumines- cence （CL） spectra obtained from different regions of an individual tetrapod are investigated. Moreover, a possible growth mechanism of the tetrapod ZnO nanostructures is also discussed based on the experimental results.     

无位置传感器无刷直流电机助力转向系统研究

为了使汽车无位置传感器无刷直流电机助力转向系统可靠工作,需解决电机转子零初始位置信息获取和零起动两大关键技术问题。针对第一个问题,提出了先进行粗略定位,再进行精确定位,即先基于电感法原理,根据母线电流变化率的大小排序确定转子所处的扇区,再通电使转子旋转至该扇区边界线的方法;零起动时,以检测母线电流变化率差值在换区切换阀值内为换区依据。通过实验验证提出的准闭环起动方法具有转子初始位置定位效率高、快速准确的起动,能保证整个系统起动处于较为平稳的状态。