检索结果-南通市图书馆

Optimization of the process for preparing Al-doped ZnO thin films by sol-gel method

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2009年第1期52卷 88-94页

作者： chen JianLin chen Ding chen zhenhua College of Materials Science and Engineering Hunan UniversityChangsha 410082China

Transparent and conducting Al-doped ZnO thin films with c-axis-preferred orientation were prepared on glass substrate via sol-gel route. The physical and chemical changes during thermal treatment were analyzed by TG-DSC spectra and the crystallization quality was characterized by XRD patterns. The optimized preheating and post-heating temperatures were determined at ～420°C and ～530°C, respectively. From thermodynamic and kinetics views, we investigated the mechanism of orientation growth with (002) plane parallel to the substrates. The surface morphologies of the films, post-heated at 420°C, 450°C, 530°C and 550°C, respectively, were observed by SEM micrographs. The film post-heated at 530°C shows a homogenous dense microstructure and exhibits the minimum sheet resistance of 140 Ω/Sq. The visible optical transmittance of all the films is beyond 90%. In addition, the annealing treatment in vacuum can contribute greatly to the electrical conductivity.

关键词： transparent conducting oxide sol-gel method zinc oxide aluminum thin films

Removal of hexavalent chromium from contaminated waters by ultrasound-assisted aqueous solution ball milling

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2017年第2期29卷 276-283页

作者： Lin chen zhenhua chen Ding chen Wei Xiong College of Materials Science and Engineering Hunan UniversityChangsha 410082China

Batch mode experiments were conducted to study the removal of hexavalent chromium（Cr（Ⅵ）） from aqueous solutions using ultrasound-assisted aqueous solution ball *** results show that the reduction rate of Cr（Ⅵ） by ultrasound-assisted aqueous solution ball milling was significantly faster than that by ball milling or ultrasound treatment alone,and an initial Cr（Ⅵ） concentration of 166 mg/L could be decreased to 0.35 mg/L at 120 *** decisive factors, including initial concentration of Cr（Ⅵ）, p H value, ultrasonic frequency and filling gas, were studied. It was found that the optimal ultrasonic frequency for ultrasound-assisted aqueous solution ball milling device was 20 k Hz, and the rate of Cr（Ⅵ）reduction as a function of filling gas followed the order： Ar 〉 air 〉 N2〉 O2. Samples were characterized by X-ray diffraction, fluorescence measurements, atomic absorption and the diphenylcarbazide colorimetric method. The Cr（Ⅵ） transformed into a precipitate that could be removed from the contaminated water, after which the water could be reused.

关键词： Cr(VI) Ultrasound wave Ball milling Hydroxyl radicals

Vector Dominance with Threshold Searchable Encryption (VDTSE) for the Internet of Things

在线全文

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第6期79卷 4763-4779页

作者： Jingjing Nie zhenhua chen College of Safety Science and Engineering Xi’an University of Science and TechnologyXi’an710054China College of Computer Science and Technology Xi’an University of Science and TechnologyXi’an710054China

The Internet of Medical Things(IoMT)is an application of the Internet of Things(IoT)in the medical *** is a cutting-edge technique that connects medical sensors and their applications to healthcare systems,which is essential in smart ***,Personal Health Records(PHRs)are normally kept in public cloud servers controlled by IoMT service providers,so privacy and security incidents may be ***,Searchable Encryption(SE),which can be used to execute queries on encrypted data,can address the issue ***,most existing SE schemes cannot solve the vector dominance threshold *** response to this,we present a SE scheme called Vector Dominance with Threshold Searchable Encryption(VDTSE)in this *** use a Lagrangian polynomial technique and convert the vector dominance threshold problem into a constraint that the number of two equal-length vectors’corresponding bits excluding wildcards is not less than a threshold ***,we solve the problem using the proposed technique modified in Hidden Vector Encryption(HVE).This technique makes the trapdoor size linear to the number of attributes and thus much smaller than that of other similar SE schemes.A rigorous experimental analysis of a specific application for privacy-preserving diabetes demonstrates the feasibility of the proposed VDTSE scheme.

关键词： Internet of Things(IoT) Internet of Medical Things(IoMT) vector dominance with threshold searchable encryption(VDTSE) threshold comparison electronic healthcare

Effect of Cryogenic Treatment on Deformation Behavior of As-cast AZ91 Mg Alloy

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2012年第6期25卷 931-936页

作者： LIU Junwei LI Guifa chen Ding chen zhenhua College of Materials Science and Engineering Nanchang Hangkong University Nanchang 330063 China College of Materials Science and Engineering Hunan University Changsha 410082 China

The as-cast AZ91 Mg alloy samples were cryogenic treated with different time. Otherwise, optical microscope （OM）, mechanical test, resistance test and XRD analysis were used to research the microstructure evolution and physical variation of the samples before and after cryogenic treatment （CT）. Due to CT, the structure of as-cast AZ91 Mg alloy was changed from disordered solid solution to ordered solid solution. Firstly, the appearance of ordered solid solution leads to the improvement of peak stress after CT, because of ordered strengthening. Secondly, resistance and crystallographic lattice constant of the samples reduce obviously. Otherwise, the frame-type twinning which is created from matrix in the cryogenic environment could hinder the twin growth and cause the ordered strengthening.

关键词： magnesium alloys cryogenic treatment ordered solution twinning microstructure

Adjoint Method for an Inverse Problem of CCPF Model

在线全文

学校读者我要写书评

暂无评论

Chinese Annals of Mathematics,Series B 2014年第3期35卷 337-354页

作者： zhenhua chen Kaiqi AN Yuan LIU Wenbin chen School of Mathematical Sciences Fudan University School of Mathematical Sciences Fudan University Corresponding author.School of Mathematical Sciences Fudan University

The problem for determining the exchange rate function of 2D CCPF model by measurements on the partial boundary is considered and solved as one PDE-constraint optimization problem. The optimal variant is the minimum of a cost functional that quantifies the difference between the measurements and the exact solutions. Gradientbased algorithm is used to solve this optimization problem. At each step, the derivative of the cost functional with respect to the exchange rate function is calculated and only one forward solution and one adjoint solution are needed. One method based on the adjoint equation is developed and implemented. Numerical examples show the efficiency of the adjoint method.

关键词： Adjoint method Inverse problem CCPF model PDE-constraintoptimization

Preparation and characteriza-tion of CoFe_2O_4/SiO_2 nanocomposites

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2006年第20期51卷 2529-2534页

作者： HUANG Xianghui chen zhenhua College of Materials Science and Engineering Hunan University Changsha 410082 China

CoFe_2O_4/SiO_2 nanocomposites 被一个大音阶的第五音胶化过程准备了，从 tetraethylorthosilicate 和金属性的硝酸盐开始。composites 的形成机制被微分扫描热量测定，红外线的光谱学，传播电子显微镜学， X 光检查衍射和拉曼光谱学... 详细信息

CoFe_2O_4/SiO_2 nanocomposites 被一个大音阶的第五音胶化过程准备了，从 tetraethylorthosilicate 和金属性的硝酸盐开始。composites 的形成机制被微分扫描热量测定，红外线的光谱学，传播电子显微镜学， X 光检查衍射和拉曼光谱学描绘。磁性用一个颤动的样品磁强计被测量。在低温度获得的 xerogel 是非结晶的，这被发现。在 400 deg C 的热处理导致了部分形成 ofCoFe_2O_4 簇。在进一步增加退火的温度到 800 deg C 以后，有约 17 nm 的直径的 CoFe_2O_4nanocrystals 能在硅石矩阵被驱散。CoFe_2O_4 簇的形成伴有在金属离子之间的相互作用的硅石网络和包围硅石网络的重新整理。当退火的温度被提起到时，在粒子和矩阵之间的相互作用将被削弱或甚至消失象 800 deg C 一样高。强制的地和 composites 的磁化的密度将随退火的温度的增加增加。

关键词： CoFe204/SiO2 纳米复合材料溶胶-凝胶磁性能

A new algorithm for inactive orbital optimization in valence bond theory

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2009年第11期52卷 1879-1884页

作者： chen zhenhua ZHANG QianEr WU Wei State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of ChemistryCollege of Chemistry and Chemical EngineeringXiamen UniversityXiamen 361005China

This paper presents an efficient algorithm for energy gradients in valence bond self-consistent field(VBSCF) method with non-orthogonal *** frozen core approximation method is extended to the case of non-orthogonal *** expressions for the total energy and its gradients are presented by introducing auxiliary orbitals,where inactive orbitals are orthogonal,while active orbitals are non-orthogonal themselves but orthogonal to inactive *** is shown that our new algorithm has a low scaling of(Na+1)m4,where Na and m are the numbers of the active orbitals and basis functions,respectively,and is more efficient than the existing VBSCF algorithms.

关键词： valence bond theory non-orthogonal orbitals gradient

Soil Phosphorus Composition and Phosphatase Activities along Altitudes of Alpine Tundra in Changbai Mountains,China

在线全文

学校读者我要写书评

暂无评论

Chinese Geographical Science 2016年第1期26卷 90-98页

作者： YANG Xiaozhu WEI Kai chen zhenhua chen Lijun State Key Laboratory of Forest and Soil Ecology Institute of Applied EcologyChinese Academy of SciencesShenyang 110164China University of Chinese Academy of Sciences Beijing 100049China

Alpine tundra ecosystems have specific vegetation and environmental conditions that may affect soil phosphorus （P） composition and phosphatase activities. However, these effects are poody understood. This study used NaOH-EDTA extraction and solution ^31P nuclear magnetic resonance （NMR） spectroscopy to determine soil P composition and phosphatase activities, including acid phosphomonoesterase （AcP）, phosphodiesterase （PD） and inorganic pyrophosphatase （IPP）, in the alpine tundra of the Changbai Mountains at seven different altitudinal gradients （i.e., 2000 m, 2100 m, 2200 m, 2300 m, 2400 m, 2500 m, and 2600 m）. The results show that total P （TP）, organic P （OP）, OP/TP, NaOH-EDTA extracted P and AcP, PD, and IPP activities over the altitude range of 2500-2600 m are significantly lower than those below 2400 m. The dominant extracted form of P is OP （73%0-83%） with a large proportion of monoesters （65%0-72%）, whereas inorganic P is present in lower proportions （17%-27%）. The activity of AcP is significantly positively correlated with the contents of soil OP, total carbon （TC）, total nitrogen （TN）, and TP （P 〈 0.05）, indicating that the AcP is a more sensitive index for responding P nutrient storage than PD and IPP. Soil properties, P composition, and phosphatase activities decrease with increased altitude and soil pH. Our results indicate that the distribution of soil P composition and phosphatase activities along altitude and AcP may play an important role in P hydrolysis as well as have the potential to be an indicator of soil quality.

关键词： alpine tundra ecosystem altitude phosphatase activity phosphorus (P) composition solution ^31p nuclear magnetic resonance (NMR) spectroscopy

FORMATION LAW OF PHASES IN ULTRAFINE POWDERS OF Al-Cu ALLOY PREPARED BY GAS EVAPORATION PROCESS

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 1999年第2期9卷 128-133页

作者： Yan, Hongge chen, zhenhua Hu, Xiang Huang, Peiyun Central South Univ of Technology Changsha China

１ＩＮＴＲＯＤＵＣＴＩＯＮＵｌｔｒａｆｉｎｅｐｏｗｄｅｒｓｗｉｔｈａｐａｒｔｉｃｌｅｓｉｚｅｌｅｓｔｈａｎ１００ｎｍｈａｖｅｅｘｃｅｌｅｎｔｐｒｏｐｅｒｔｉｅｓｉｎｃｏｎｔｒａｓｔｔｏｃｏａｒｓｅｇｒａｉｎｍａｔｅｒ... 详细信息

１ＩＮＴＲＯＤＵＣＴＩＯＮＵｌｔｒａｆｉｎｅｐｏｗｄｅｒｓｗｉｔｈａｐａｒｔｉｃｌｅｓｉｚｅｌｅｓｔｈａｎ１００ｎｍｈａｖｅｅｘｃｅｌｅｎｔｐｒｏｐｅｒｔｉｅｓｉｎｃｏｎｔｒａｓｔｔｏｃｏａｒｓｅｇｒａｉｎｍａｔｅｒｉａｌｓ［１，２］ａｎｄｈａｖｅｗ...

关键词： gas evaporationvapor condensationultrafine powdersalloy powder