The Water-Soluble Peripheral Substituted Phthalocyanines as Corrosion Inhibitors for Copper in 0.1 N HCl: Gravimetric,Electrochemical, SEM-EDS,and Quantum Chemical Calculations

Protection of Metals and Physical Chemistry of Surfaces - Corrosion inhibition effects of water-soluble peripheral substituted cobalt, copper and zinc metallophthalocyanines (CoPc (1), CuPc (2) and...     

改进信息增益的维吾尔文特征选择方法

特征选择是维吾尔语文本分类的关键技术,对分类结果将产生直接的影响。为了提高传统信息增益在维吾尔文特征选择中的效果,在深度分析维吾尔文语种特点的基础上,提出了一种新的信息增益特征选择方法。该方法结合类词频和特征分布系数以及倒逆文档频率,对传统信息增益进行修正;引入一个备选特征分布系数来平衡类间选取的特征个数;在维吾尔文数据集上实验验证。实验结果表明,改进的算法对维吾尔文分类效果有明显的提高。     

Polymer Protected and Gel Immobilized Gold and Silver Nanoparticles in Catalysis

This mini-review is focused on preparation of polymer protected gold (AuNPs) and silver (AgNPs) nanoparticles that are immobilized on the surface of inorganic supporters and within hydrogel and/or cryogel matrices. A series of water soluble polymers such as poly(N-vinylpyrrolidone), poly(acrylic acid), branched polyethyleneimine, and amphoteric cryogel based on the copolymer of N,N-dimethylaminoethylmethacrylate and methacrylic acid poly(DMAEM-MAA) were used for reduction and stabilization of metal nanoparticles. The catalytic properties of polymer protected AuNPs and AgNPs were evaluated with respect to hydrogen peroxide decomposition, hydrogenation of 4-nitrophenol and oxidation of cyclohexane.     

基于声学特征的母语非汉语者声调研究

从提高满足少数民族普通话高自然度语音合成与高精度语音识别的实际应用需求出发,首次从实验语音学的角度对初级、中级和高级阶段的50名维吾尔族汉语学习者与10名母语为汉语普通话的说话人声调的一阶差分与时长以及相似度进行对比,并对其声调的一阶差分模式、声调时长等韵律参数进行了实验分析,得出维吾尔族学生对汉语声调的偏误情况以及与中国少数民族汉语水平等级考试(Master of Human Kinetics, MHK)成绩的关系。通过实验结果可以发现,三组维吾尔族人学习普通话的声调都有困难。两种语言的音系,语调和重音等特性影响了第二语言中的声调特性。归纳了维吾尔族学习者声调的基本声学特征,总结出了一些重要的规则和结论;为解决给汉语语音处理带来的困难,尤其是少数民族汉语的语音合成和语音识别方面的声调问题,提供了重要的参考依据。     

Development of a correlation to study parameters affecting nitrification in a domestic wastewater treatment plant

BACKGROUND: Nitrification performance of an activated sludge reactor treating weak domestic wastewater was investigated for 11 months. Ammonia nitrogen removals were investigated as a function of wastewater composition and operational conditions. Backward elimination experimental design was used to determine the influence of the most important independent variables on NH₃‐N removal efficiencies. Influent ammonia and biological oxygen demand (BOD₅) concentrations, hydraulic retention time (HRT), mixed liquid suspended solids (MLSS), temperature, pH and dissolved oxygen (DO) concentration were considered as independent variables. This study aimed to find the most important parameters to describe nitrification performance. RESULTS: The presence of nitrification was confirmed by ammonia and nitrate variations throughout the reactor; ammonia oxidizing bacteria (AOB) populations were determined using a fluorescence in situ hybridization (FISH) method. MLSS concentration, influent BOD₅ concentration and temperature were found to be the most influential factors on nitrification performance. The empirical correlation using multiple linear regressions was statistically significant and produced an adjusted coefficient of multiple determinations (R²_adj) of 92.5%. CONCLUSION: Correlation provides a good understanding of the various parameters that affect the nitrification process, and could be extended to other case studies. Using these results, operators can apply proper operational strategies to maintain nitrification in wastewater treatment plants. Copyright © 2007 Society of Chemical Industry     

Effects of physical growth conditions on the structural and optical properties of sputtered grown thin HfO2 films

HfO₂ thin films were prepared by reactive DC magnetron sputtering technique on (100) p-Si substrate. The effects of O₂/Ar ratio, substrate temperature, sputtering power on the structural properties of HfO₂ grown films were studied by Spectroscopic Ellipsometer (SE), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrum, and X-ray photoelectron spectroscopy (XPS) depth profiling techniques. The results show that the formation of a SiO_x suboxide layer at the HfO₂/Si interface is unavoidable. The HfO₂ thickness and suboxide formation are highly affected by the growth parameters such as sputtering power, O₂/Ar gas ratio during sputtering, and substrate temperature. XRD spectra show that the deposited films have (111) monoclinic phase of HfO₂, which is also supported by FTIR spectra. XPS depth profiling spectra shows that highly reactive sputtered Hf atoms consume some of the oxygen atoms from the underlying SiO₂ to form HfO₂, leaving Si-Si bonds behind.     

非汉语母语者的普通话元音和辅音感知研究

语音感知研究是语音学主要研究内容之一。为了解学习者对普通话元音和辅音的感知情况,并为汉语教学提供借鉴,拓宽言语学习模型的应用领域,减少教学的盲目性,根据第二语言习得理论模式,采用实验语音学和统计学的方法,设计辨认实验和区分实验,分别对普通话水平处于高级和初级水平的20名维吾尔族大学生元音、塞音、擦音和塞擦音的感知情况进行研究。辨认实验考察学习者对元音和辅音的感知反应时间和感知准确率。在区分实验中,计算元音对的频谱距离,辅音对的频谱距离,以及它们的时长差异,对学习者的区分能力进行分析。实验结果显示高级水平学习者的感知元音和辅音的能力明显高于初级水平学习者。学习者对发音部位靠后的元音反应时间快且感知准确率高,对于发音部位靠前的元音反应时间较慢且感知准确率低,对塞擦音的辨认准确率高,对擦音的辨认准确度最低。元音对的频谱距离和辅音对的时长差异会影响到学习者的区分能力,但辅音对的频谱距离和区分情况不存在密切联系。