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Membrane flux dynamics in the submerged ultrafiltration hybrid treatment process during particle and natural organic matter removal

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Journal of Environmental Sciences 2011年第12期23卷 1970-1976页

作者： Wei zhang Xiaojian zhang Yonghong Li Jun Wang Chao Chen Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China Beijing Special Engineering Design and Research Institute Beijing 100028 China

Particles and natural organic matter （NOM） are two major concerns in surface water, which greatly influence the membrane filtration process. The objective of this article is to investigate the efiect of particles, NOM and their interaction on the submerged ultrafiltration （UF） membrane flux under conditions of solo UF and coagulation and PAC adsorption as the pretreatment of UF. Particles, NOM and their mixture were spiked in tap water to simulate raw water. Exponential relationship, （JP/JP0 = a×exp{-k[t-（n-1）T]}）, was developed to quantify the normalized membrane flux dynamics during the filtration period and fitted the results well. In this equation, coefficient a was determined by the value of JP/JP0 at the beginning of a filtration cycle, refiecting the flux recovery after backwashing, that is, the irreversible fouling. The coefficient k refiected the trend of flux dynamics. Integrated total permeability （ΣJP） in one filtration period could be used as a quantified indicator for comparison of different hybrid membrane processes or under different scenarios. According to the results, there was an additive effect on membrane flux by NOM and particles during solo UF process. This additive fouling could be alleviated by coagulation pretreatment since particles helped the formation of flocs with coagulant, which further delayed the decrease of membrane flux and benefited flux recovery by backwashing. The addition of PAC also increased membrane flux by adsorbing NOM and improved flux recovery through backwashing.

关键词： ultrafiltration membrane flux particles natural organic matter hybrid process backwashing

Detections of Gamma-Rays from Globular Clusters ESO 452-SC11, NGC 6380, Palomar 6 and UKS 1 with Fermi-LAT

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Research in Astronomy and Astrophysics 2022年第5期22卷 176-181页

作者： Min Yuan Jiao Zheng Pengfei zhang Li zhang Department of Astronomy School of Physics and AstronomyKey Laboratory of Astroparticle Physics of Yunnan ProvinceYunnan UniversityKunming 650091China

The events from 157 globular clusters(GCs)are analyzed by using 12 yr long-term Pass 8 data from Fermi Large Area *** the 34 GCs reported in previous literatures,four additional GCs(ESO 452-SC11,NGC6380,Palomar 6 and UKS 1)in the Milky Way are detected as gamma-ray GC *** for UKS 1,these are known as the faintest GCs in long-wavelength *** data analysis has been performed for the four *** no pulsars are determined in radio and/or X-ray wavelengths so far,their gamma-ray pulsation emissions are not found,and no significant gamma-ray flux variability is *** numbers of MSPs within the four GCs are estimated based on the assumption that the MSPs within each GC emit similar amounts of *** gamma-ray results reported here could help us better understand the nature of gamma-ray emission origins for GCs.

关键词： (Galaxy:)globular clusters individual(ESO452-SC11,NGC6380,Palomar6andUKS1)

Total nitrogen and community turnover determine phosphorus use efficiency of phytoplankton along nutrient gradients in plateau lakes

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Journal of Environmental Sciences 2023年第2期124卷 699-711页

作者： Yun zhang Hucai zhang Qi Liu Lizeng Duan Qichao Zhou Institute for Ecological Research and Pollution Control of Plateau Lakes School of Ecology and Environmental SciencesYunnan UniversityKunming 650500China

Numerous studies support that biodiversity predict most to ecosystem functioning,but whether other factors display a more significant direct impact on ecosystem functioning than biodiversity remains to be *** investigated 398 samples of the phytoplankton phosphorus resource use efficiency(RUE_(P)=chlorophyll-a concentration/dissolved phosphate)across two seasons in nine plateau lakes in Yunnan Province,*** identified the main contributors to phytoplankton RUEP and analyzed their potential influences on RUEP at different lake trophic *** results showed that total nitrogen(TN)contributed the most to RUEP among the nine lakes,whereas community turnover(measured as community dissimilarity)explained the most to RUEP variation across the two ***,TN also influenced RUEP by affecting *** richness(SR),functional attribute diversity(FAD2),and dendrogram-based functional diversity(FDc)were positively correlated with RUEP in both seasons,while evenness was negatively correlated with RUEP at the end of the rainy *** also found that the effects of biodiversity and turnover on RUEP depended on the lake trophic *** and FAD2 were positively correlated with RUEP in all three trophic *** showed a negative correlation with RUEP at the eutrophic and oligotrophic levels,but a positive correlation at themesotrophic *** had a negative influence on RUEP at the eutrophic level,but a positive influence at the mesotrophic and oligotrophic ***,our results suggested that multiple factors and nutrient states need to be considered when the ecosystem functioning predictors and the biodiversityecosystem functioning relationships are investigated.

关键词： Community turnover Biodiversity Phytoplankton Resource use efficiency Taxonomic diversity Total nitrogen

Remarkable enhancement in failure stress and strain of penta-graphene via chemical functionalization

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Nano Research 2017年第11期10卷 3865-3874页

作者： Yingyan zhang Qingxiang Pei Zhendong Sha Yongwei zhang Huajian Gao School of Computing Engineering and Mathematics Western Sydney University Penrith NSW2751 Australia Institute of High Performance Computing A＊STAR Singapore 138632 Singapore International Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong University Xi'an 710049 China School of Engineering Brown University Providence Rhode Island 02912 USA

Penta-graphene （PG）,a newly proposed two-dimensional material composed entirely of carbon pentagons,is believed to possess much lower failure stress and strain than those of *** open question is whether and how these properties can be *** using molecular dynamics simulations,we examine the deformation and failure processes of PG functionalized with different functional *** reveal that complete chemical functionalization leads to remarkable increases in the failure stress and strain of PG by up to 86.6% and 82.4%,*** underlying reason for this enhancement is that the buckled pentagonal rings in pristine and partially functionalized PGs can easily transform into planar polygon rings under stretching;in contrast,complete functionalization of PG strongly stabilizes its structure and prevents such transformation,thereby significantly increasing the failure stress and *** findings suggest a possible route to enhance the mechanical properties of PG for potential applications in nanocomposites and nanodevices.

关键词： penta-graphene mechanical properties chemical functionalization molecular dynamics

Experimental and Numerical Investigation of the Unsteady Tip Leakage Flow in Axial Compressor Cascade

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Journal of Thermal Science 2013年第2期22卷 103-110页

作者： Chengqing Li Tingfeng Ke Jingxuan zhang Hongwu zhang Weiguang Huang Shanghai Advanced Research Institute Chinese Academy of Sciences

For convenience of both measurement and adjusting the clearance size and incidence, the current research is mainly conducted by experiments on an axial compressor linear cascade. The characteristics and the condition under which the unsteadiness of tip leakage flow would occur were investigated by dynamic measuring in different clearances, inlet velocities and incidences. From the experiment it is found that increasing tip clearance size or reducing rotor tip incidence can affect the strength of the tip clearance flow. Then the experimental results also indicate the tip leakage shows instability in certain conditions, and the frequency of unsteadiness is great influenced by inflow angle. The condition of occurrence of tip leakage flow unsteadiness is when the leakage flow is strong enough to reach the pressure side of the adjacent blade. The main cause of tip leakage flow unsteadiness is the tip blade loading.

关键词： axial flow compressor linear cascade tip leakage flow unsteady

Aero-engine Blade Fatigue Analysis Based on Nonlinear Continuum Damage Model Using Neural Networks

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Chinese Journal of Mechanical Engineering 2012年第2期25卷 338-345页

作者： LIN Jiewei zhang Junhong zhang Guichang NI Guangjian BI Fengrong State Key Laboratory of Engines Tianjin UniversityTianjin 300072China

Fatigue life and reliability of aero-engine blade are always of important significance to flight *** establishment of damage model is one of the key factors in blade fatigue *** linear Miner＇s sum method is not suitable for aero-engine because of its low accuracy.A back propagation neutral network（BPNN） based on the combination of Levenberg-Marquardt（LM） and finite element method（FEM） is used to describe process of nonlinear damage accumulation behavior in material and predict fatigue life of the *** tests of standard specimen made from TC4 are carried out to obtain material fatigue parameters and S-N curve.A nonlinear continuum damage model（CDM）,based on the BPNN with one hidden layer and ten neurons,is built to investigate the nonlinear damage accumulation behavior,in which the results from the tests are used as training *** with linear models and previous nonlinear models,BPNN has the lowest calculation error in full load *** has significant accuracy when the load is below 500 ***,when the load is 350 MPa,the calculation error of the BPNN is only 0.4%.The accurate model of the blade is built by using 3D coordinate measurement *** loading cycle in fatigue analysis is defined from takeoff to cruise in 10 min,and the load history is obtained from finite element analysis（FEA）.Then the fatigue life of the compressor blade is predicted by using the BPNN *** final fatigue life of the aero-engine blade is 6.55 104 cycles（10 916 h） based on the BPNN model,which is effective for the virtual design of aero-engine blade.

关键词： continuum damage model neutral network Finite Element Method aero-engine blade life prediction

Two-dimensional polymer-based nanosheets for electrochemical energy storage and conversion

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Journal of Energy Chemistry 2018年第1期27卷 99-116页

作者： Shuai Bi Chenbao Lu Wenbei zhang Feng Qiu Fan zhang School of Chemistry and Chemical Engineering State Key Laboratory of Metal Matrix CompositesShanghai Jiao Tong UniversityShanghai 200240China School of Chemical and Environmental Engineering Shanghai Institute of TechnologyShanghai 201418China

Over the past decades, two-dimensional（2D） nanomaterials possessing planar layered architecture and unique electronic structures have been being quickly developed, due to their wide potential application in the fields of chemistry, physics, and materials science. As a new family of 2D nanomaterials, 2D polymerbased nanosheets, featuring excellent characters, such as tunable framework structures, light weight, flexibility, high specific surface, and good semiconducting properties, have been emerging as one kind of promising functional materials for optoelectronics, gas separation, catalysis and sensing, etc. In this review, the recent progress in synthetic approach and characterization of 2D polymer-based nanosheets were summarized, and their current advances in electrochemical energy storage and conversion including second batteries, supercapacitors, oxygen reduction and hydrogen evolution were discussed systematically.

关键词： Two-dimensional polymer Nanosheet Nanoscale morphology Electrochemical performance Energy storage and conversion

A survey of unmanned aerial vehicle flight data anomaly detection:Technologies,applications,and future directions

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Science China(Technological Sciences) 2023年第4期66卷 901-919页

作者： YANG Lei LI ShaoBo LI ChuanJiang zhang AnSi zhang XuDong School of Mechanical Engineering Guizhou UniversityGuiyang 550025China State Key Laboratory of Public Big Data Guizhou UniversityGuiyang 550025China

Flight data anomaly detection plays an imperative role in the safety and maintenance of unmanned aerial vehicles(UAVs).It has attracted extensive attention from ***,the problems related to the difficulty in obtaining abnormal data,low model accuracy,and high calculation cost have led to severe challenges with respect to its practical ***,in this study,firstly,several UAV flight data simulation softwares are presented based on a brief presentation of the basic concepts of anomalies,the contents of UAV flight data,and the public datasets for flight data anomaly ***,anomaly detection technologies for UAV flight data are comprehensively reviewed,including knowledge-based,model-based,and data-driven ***,UAV flight data anomaly detection applications are briefly described and ***,the future trends and directions of UAV flight data anomaly detection are summarized and prospected,which aims to provide references for the following research.

关键词： unmanned aerial vehicle(UAV) flight data anomaly detection data-driven

THE HOLDER CONTINUITY OF THE LYAPUNOV EXPONENT FOR A QUASI-PERIODIC SZEGO COCYCLE

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Acta Mathematica Scientia 2024年第6期44卷 2099-2110页

作者： BEI zhang School of Mathematical Sciences Ocean University of ChinaQingdao 266100China

In this paper,I consider the Hölder continuity of the Lyapunov exponent for a quasi-periodic Szegö cocycle with weak Liouville frequency.I extend the existing results about the regularity of the Lyapunov exponent from... 详细信息

关键词： Szegöcocycle Lyapunov exponents Holder continuity orthogonal polynomials