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Journal of Environmental Sciences 2017年第6期29卷 240-246页

作者： lei zhang Zhihong Zou Wei Shan School of Economics and Management Beihang UniversityBeijing 100191China

Water quality forecasting is an essential part of water resource management. Spatiotemporal variations of water quality and their inherent constraints make it very complex. This study explored a data-based method for short-term water quality forecasting. Prediction of water quality indicators including dissolved oxygen, chemical oxygen demand by KMnQ and ammonia nitrogen using support vector machine was taken as inputs of the particle swarm algorithm based optimal wavelet neural network to forecast the whole status index of water quality. Gubeikou monitoring section of Miyun reservoir in Beijing, China was taken as the study case to examine effectiveness of this approach. The experiment results also revealed that the proposed model has advantages of stability and time reduction in comparison with other data-driven models including traditional BP neural network model, wavelet neural network model and Gradient Boosting Decision Tree model. It can be used as an effective approach to perform short-term comprehensive water quality prediction.

关键词： Support vector machineParticle swarm optimizationWavelet neural networkWater quality forecasting

Investigation on mechanism of phosphate removal on carbonized sludge adsorbent

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Journal of Environmental Sciences 2018年第2期30卷 335-344页

作者： lei zhang Junxin Liu Xuesong Guo Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China University of Chinese Academy of Sciences Beijing 100049 China

For the removal of phosphate（PO43-） from water, an adsorbent was prepared via carbonization of sewage sludge from a wastewater treatment plant： carbonized sludge adsorbent（CSA）. The mechanism of phosphate removal was determined after studying the structure and chemical properties of the CSA and its influence on phosphate removal. The results demonstrate that phosphate adsorption by the CSA can be fitted with the pseudo second-order kinetics and Langmuir isotherm models, indicating that the adsorption is single molecular layer adsorption dominated by chemical reaction. The active sites binding phosphate on the surface are composed of mineral particles containing Si/Ca/Al/Fe. The mineral containing Ca, calcite, is the main factor responsible for phosphate removal. The phosphate removal mechanism is a complex process including crystallization via the interaction between Ca2＋ and PO43-; formation of precipitates of Ca2＋, Al3＋, and PO43-; and adsorption of PO43-on some recalcitrant oxides composed of Si/Al/Fe.

关键词： Sewage sludge Carbonization Phosphate removal Mechanism

The Mechanical Analysis and Experimental Study of Shock Wave Effect of Electrical Discharge under Water In Filth Cleaning

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上海交通大学学报 2004年第z2期38卷 229-234页

作者： Deng Qilin zhang lei Zhou Jinjin Shanghai Jiaotong University Shanghai 200030 China Dalian University of Technology Dalian 116024 China Dalian University of Technology Dalian 116024 China

Filth adhering to metal pipes can be cleaned by shock wave generated by electrical discharge under water. The mechanism of shock wave effect of electrical discharge under water on filth cleaning is analyzed by building a mechanical model. A metal pipe coated with cement to simulate real filth is cleaned by using electrical discharge under water. The experimental results confirm the mechanical analysis and also show the technology of electrical discharge under water is an very effective method for filth cleaning.

关键词： shock wave filth cleaning effect of electrical discharge under water

Diffusion and Security Evaluation of Feistel-PG

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Chinese Journal of Electronics 2017年第4期26卷 734-739页

作者： WANG Yanfeng WU Wenling zhang lei Trusted Computing and Information Assurance Laboratory Institute of Software Graduate University of Chinese Academy of Sciences State Key Laboratory of Computer Science Institute of Software

Feistel-PG structure is a new specific Generalized Feistel structure(GFS) adopted in DBlock and LHash. Its main feature is adding a sbox-size permutation before the round function. Different choices of the permutation may affect the security property of ciphers with Feistel-PG structure but how it effects is not clear. We evaluate the values of diffusion round for all possible parameters and summarize the characteristics of optimum shuffles. The results show that one special kind of FeistelPG achieves full diffusion in less cost than the improved GFS. This advantage may attract the designers’ interests and this kind of Feistel-PG ciphers are suggested to designers. We also evaluate the security of suggested ciphers against various byte-oriented attacks, including differential cryptanalysis, linear cryptanalysis, impossible differential attack and integral attack. Some permutations with optimum diffusion but relatively weaker security are filtered out and these permutations should be avoided by designers.

关键词： Block cipher Diffusion Cryptanalysis GFS Feistel-PG

Numerical Modeling of the Compression Process of Elastic Open-cell Foams

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Chinese Journal of Aeronautics 2007年第3期20卷 215-222页

作者： zhang Jia-lei LU Zi-xing Institute of Solid Mechanics Beijing University of Aeronautics and Astronautics Beijing 100083 China

The random models of open-cell foams that can reflect the actual cell geometrical properties are constructed with the Voronoi technique. The compression process of elastic open-cell foams is simulated with the nonlinear calculation module of finite element analysis program. In order to get the general results applicable to this kind of materials, the dimensionless compressive stress is used and the stress-strain curves of foam models with different geometrical properties are obtained. Then, the influences of open-cell geometrical properties, including the shape of strut cross section, relative density and cell shape irregularity, on the compressive nonlinear mechani- cal performance are analyzed. In addition, the numerical results are compared with the predicted results of cubic staggering model. Nu- merical results indicate that the simulated results reflect the compressive process of foams quite well and the geometrical properties of cell have significant influences on the nonlinear mechanical behavior of foams.

关键词： Voronoi technique open-cell foam nonlinear compressive stress

Microstructure and Tribological Properties of Plasma Nitriding Cast CoCrMo Alloy

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Journal of Materials Science & Technology 2012年第1期28卷 60-66页

作者： Qingliang Wang Chuanhui Huan lei zhang School of Material Science and Engineering China University of Mining&TechnologyXuzhou 221116China College of Electro-mechanical Engineering Xuzhou Institute of TechnologyXuzhou 221008China

A medical cast CoCrMo alloy was coated by plasma nitriding process to enhance the wear resistance. The microstructures, phases and micro-hardness of nitrided layers were investigated by atomic force microscopy （AFM）, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and micro-hardness. Tribological prop- erties were investigated on a pin-on-disc wear tester under 25% bovine serum solutions. The experimental results showed that plasma nitriding was a promising process to produce thick, hard and wear resistant layers on the surface of CoCrMo alloy. The harder CrN and Cr2N phases formed on the plasma nitrided layer with the compact nano-crystalline structure. Compared with the untreated sample, all nitrided samples showed the lower wear rates and higher wear resistance at different applied loads and nitriding temperatures. It was concluded that the improvement of wear resistance could be ascribed to the formation of thicker and harder nitrided layers with the specific microstructures on nitrided surfaces.

关键词： CoCrMo alloy Plasma nitrlding Microstructure Tribology

Photoelectrocatalytic activity of an ordered and vertically aligned TiO2 nanorod array/BDD heterojunction electrode

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Science Bulletin 2017年第9期62卷 619-625页

作者： Yanhe Han lei zhang Yafei Wang Haimin zhang Shanqing zhang Department of Environmental Engineering Beijing Institute of Petrochemical TechnologyBeijing 102617China Key Laboratory of Materials Physics Centre for Environmental and Energy NanomaterialsAnhui Key Laboratory of Nanomaterials and NanotechnologyInstitute of SolidState PhysicsChinese Academy of SciencesHefei 230031China Griffith School of Environment Gold Coast CampusGriffith UniversityQLD 4222Australia

Rutile TiO_2 nanorod(TiNR) arrays were fabricated on a boron-doped diamond(BDD) substrate by a simple hydrothermal synthesis method. A fluorine-doped tin oxide(FTO) electrode grown with TiNR arrays was also prepared using the same technology for comparison. Field-emission scanning electron microscopy results show that oriented TiNR arrays can grow vertically on the surface of BDD and FTO electrodes. TiNR arrays grown on both electrodes had the same length(3 μm). In comparison with the TiNR/FTO electrode, the TiNR/BDD electrode demonstrated a higher photoelectrocatalytic activity for the degradation of water and organic compounds, which is mostly attributed to the formation of a p-n heterojunction between the TiNR arrays and BDD at high potential, apart from the density of TiNR. A linear relationship between the photoelectrocatalytic current and the organic concentration can be observed on both electrodes. However, the linear range between net photoelectrocatalytic current values and organic compound concentrations for the TiNR/BDD electrode are much greater than those for the TiNR/FTO electrode, which makes the TiNR/BDD electrode a versatile material for the photocatalytic degradation and sensing of organic compounds.

关键词： Rutile Ti02 nanorods One-dimensioned nanomaterials Boron-doped diamond Photoelectrocatalysis p-n heterojunction

Sinc interpolation based method for compensation of ionospheric dispersion effects on BOC signals with high subcarrier rate

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Science China(Information Sciences) 2016年第10期59卷 152-168页

作者： Hang RUAN lei zhang Teng LONG Key Laboratory of Electronic and Information Technology in Satellite Navigation (Beijing Institute of Technology) Ministry of Education School of Information and Electronics Beijing Institute of Technology

Binary Offset Carrier(BOC) signals with high subcarrier rate such as Alt BOC(15,10) and cosBOC(15,2.5) have been adopted for the next generation of Global Navigation Satellite System(GNSS) to make full use of the allocated spectrum. However, the two main lobes of the BOC signals are tremendously separated in the frequency spectrum and the group delay of the two lobes are greatly dispersed due to ionospheric dispersion. The signals will suffer extremely severe distortion caused by the group delay dispersion including waveform ripples, power losses and correlation function asymmetries. In this paper, a novel time domain sinc interpolation based ionospheric dispersion compensation method is proposed to eliminate the distortion to the BOC ***, the time domain model of BOC signal under the dispersive ionosphere is developed. Afterwards, based on the model, the two signal main lobes are aligned by sinc interpolation so that the ionospheric dispersion effects are almost mitigated. Taking Galileo E5 Alt BOC(15,10) signal as an example, the performance of the proposed method is evaluated by simulation and test. The results show that the proposed method is able to more effectively compensate the ionospheric dispersion with fewer computational loads versus existing methods.

关键词： ionospheric dispersion sinc interpolation BOC code tracking bias high subcarrier rate

Effect of C60 nanoparticles on elasticity of small unilamellar vesicles composed of DPPC bilayers

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Chinese Physics B 2020年第4期29卷 549-555页

作者： Tanlin Wei lei zhang Yong zhang School of Physics Sun Yat-Sen UniversityGuangzhou 510275China

The interaction between C60 nanoparticles and biomembranes has been of great interest in researches over the past decades due to their novel applications as well as potential *** this work,we study the deformation of the small unilamellar vesicles composed of dipalmitoylphosphatidylcholine(DPPC)lipid bilayers infiltrated with C60 nanoparticles of different molecular concentrations through coarse-grained molecular dynamics *** employing the Helfrich spontaneous curvature model,the bending modulus and the spontaneous curvature of the vesicles with C60 nanoparticles of different concentrations are obtained according to the simulation *** results show that the bending modulus and the spontaneous curvature of pure DPPC vesicle membranes are approximately 1.6×10^-19J and 1.4 nm^-1,*** of them increase linearly approximately as the C60 concentration increases from 0 to 16.3%.The density profiles of vesicles,the order of lipid packing and the diffusion characteristics of DPPC and C60 are also investigated.

关键词： lipid vesicle bending modulus C60 nanoparticles spontaneous curvature

A simultaneous space-time wavelet method for nonlinear initial boundary value problems

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Applied Mathematics and Mechanics(English Edition) 2018年第11期39卷 1547-1566页

作者： Jizeng WANG lei zhang Youhe ZHOU Key Laboratory of Mechanics on Disaster and Environment in Western China the Ministry of Education College of Civil Engineering and Mechanics Lanzhou University

A high-precision and space-time fully decoupled numerical method is developed for a class of nonlinear initial boundary value problems. It is established based on a proposed Coiflet-based approximation scheme with an adjustable high order for the functions over a bounded interval, which allows the expansion coefficients to be explicitly expressed by the function values at a series of single points. When the solution method is used, the nonlinear initial boundary value problems are first spatially discretized into a series of nonlinear initial value problems by combining the proposed wavelet approximation and the conventional Galerkin method, and a novel high-order step-by-step time integrating approach is then developed for the resulting nonlinear initial value problems with the same function approximation scheme based on the wavelet theory. The solution method is shown to have the N th-order accuracy, as long as the Coiflet with [0, 3 N-1]compact support is adopted, where N can be any positive even number. Typical examples in mechanics are considered to justify the accuracy and efficiency of the method.

关键词： nonlinear initial boundary value problem Coiflet numerical method