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On the validity of the Boltzmann–BGK model through relaxation evaluation

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Acta Mechanica Sinica 2014年第2期30卷 133-143页

作者： quan-hua Sun Chun-Pei Cai Wei Gao State Key Laboratory of High Temperature Gas Dynamics Institute of MechanicsChinese Academy of Sciences Department of Mechanical and Aerospace Engineering New Mexico State University

The Boltzmann-Bhatnagar-Gross-Krook（BGK）model is investigated for its validity regarding the collision term approximation through relaxation evaluation. The evaluation is based on theoretical analysis and numerical comparison between the BGK and direct simulation Monte Carlo（DSMC） results for three specifically designed relaxation problems. In these problems, one or half component of the velocity distribution is characterized by another Maxwellian distribution with a different temperature. It is analyzed that the relaxation time in the BGK model is unequal to the molecular mean collision time. Relaxation of component distribution fails to involve enough contribution from other component distributions, which makes the BGK model unable to capture details of velocity distribution, especially when discontinuity exists in distribution. The BGK model,however, predicts satisfactory results including fluxes during relaxation when the temperature difference is small. Particularly, the model-induced error in the BGK model increases with the temperature difference, thus the model is more reliable for low-speed rarefied flows than for hypersonic flows.

关键词： BGK model Boltzmann equation Validity evaluation DSMC method Time relaxation

Impedance Characterization of the Film Formation Process at the Graphite Anodes

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Chinese Chemical Letters 2000年第10期11卷 915-918页

作者： Bo hua DENG Yong Fang LI hua quan YANG Center for Molecular Science Institute of ChemistryChinese Academy of SciencesBeijing 100080 Department of Chemistry Peking UniversityBeijing 100875

In this paper, the formation mechanism of the passive SEI film at the natural graphite anodes was investigated with tilt: electrochemical impedance spectroscopy (EIS). A characteristic semicircle was observed in the lower frequency range of the EIS spectrum for the irreversible charge process (lithium intercalation) at ca. 0.75V, 0.40V and 0.20V.

关键词： electrochemical impedance spectroscopy surface film graphite anodes Li-ion battery

Onc*-Normal Subgroups in Finite Groups

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Acta Mathematica Sinica,English Series 2012年第3期28卷 623-630页

作者： hua quan WEI Wei Ping GU Hong Fei PAN School of Mathematics Science Guangxi Teachers Education University School of Mathematics and Computer Science Xinyang Normal University

A subgroup H of a finitegroup G is called a c＊-normal subgroup of G if there exists a

关键词： c*-Normal S-quasinormally embedded p-nilpotent p-supersolvable

Sensitivity of key factors and uncertainties in health risk assessment of benzene pollutant

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Journal of Environmental Sciences 2007年第10期19卷 1272-1280页

作者： LIU Zhi-quan ZHANG Ying-hua LI Guang-he ZHANG Xu Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China

Predicting long-term potential human health risks from contaminants in the multimedia environment requires the use of models. However, there is uncertainty associated with these predictions of many parameters which can be represented by ranges or probability distributions rather than single value. Based on a case study with information from an actual site contaminated with benzene, this study describes the application of MMSOILS model to predict health risk and distributions of those predictions generated using Monte Carlo techniques. A sensitivity analysis was performed to evaluate which of the random variables are most important in producing the predicted distributions of health risks. The sensitivity analysis shows that the predicted distributions can be accurately reproduced using a small subset of the random variables. The practical implication of this analysis is the ability to distinguish between important versus unimportant random variables in terms of their sensitivity to selected endpoints. This directly translates into a reduction in data collection and modeling effort. It was demonstrated that how correlation coefficient could be used to evaluate contributions to overall uncertainty from each parameter. The integrated uncertainty analysis shows that although drinking groundwater risk is similar with inhalation air risk, uncertainties of total risk come dominantly from drinking groundwater route. Most percent of the variance of total risk comes from four random variables.

关键词： Monte Carlo sensitivity uncertainty MMSOILS models risk assessment

Laser-Manipulating Macroscopic quantum States of a Bose-Einstein Condensate Held in a Kronig-Penny Potential

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Communications in Theoretical Physics 2009年第7期52卷 68-74页

作者： ZHU Qian-quan HAI Wen-hua DENG Hai-Ming Department of Physics Hunan Normal University Changsha 410081 China

We investigate the boundary vaJue problem （BVP） of a quasi-one-dimensional Gross-Pitaevskii equation with the Kronig-Penney potential （KPP） of period d, which governs a repulsive Bose-Einstein condensate. Under the zero and periodic boundary conditions, we show how to determine n exact stationary eigenstates {Rn} corresponding to different chemical potentials {μn} from the known solutions of the system. The n-th eigenstate P~ is the Jacobian elliptic function with period 2din for n = 1,2,…, and with zero points containing the potential barrier positions. So Rn is differentiable at any spatial point and R2 describes n complete wave-packets in each period of the KPP. It is revealed that one can use a laser pulse modeled by a 5 potential at site xi to manipulate the transitions from the states of {Rn} with zero Point x≠xi to the states of {Rn＇} with zero Point x= Xi. The results suggest an experimental scheme for applying BEC to test the BVP and to observe the macroscopic quantum transitions.

关键词： Bose-Einstein Condenstate Kronig-Penney potential boundary value problem laser-manipulating macroscopic quantum state

Field Application of Mulberry Straw Arch in Ecological Bank Revetment

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Journal of Renewable Materials 2022年第10期10卷 2607-2621页

作者： Xiaojuan Yu Chao Liu quan hua Xiaohui Wang Yongbin Li Geotechnical Research Institute Yancheng Institute of TechnologyYancheng224051China Yancheng City Channel Management Office Yancheng Transportation BureauYancheng224051China

With the growing level of awareness and increasing demand for environmental protection,timber pile revetments with significant ecological effects have experienced increasingly wide application in *** current timber pile revetment system has two problems:continuous dense piles have high construction costs and require large timber consumptions,while the discrete pile-bamboo fence systems have poor retaining *** these problems,an original revetment structure form is proposed:a discrete pile-mulberry straw arch *** investigate the mechanical properties of the mulberry straw,some mechanical tests are conducted on mulberry straw and its arch *** is found that the average compressive strength of mulberry straw is 2.30 MPa,the bending strength is 20.08 MPa and the shear strength is 2.99 MPa;considering the structural characteristics of arches,mulberry straw arches have a high bending strength,which affords immense potential for their application in revetment ***,by doing field study of the discrete timber pile-mulberry straw arch structure for bank revetment,it is found that the arch height of the mulberry straw arch changes 1.4–1.6 cm after 489 d *** soil settlement before the straw arch is 0.13–0.18 cm and the settlement of the pile is 0.66–0.72 *** with bamboo fence structure,the cost of using mulberry straw arch structure as revetment material can save up to 27.07%.Therefore,the discrete timber pile-mulberry straw arch has a rational and stable structure that provides effective support for protecting the riverbank and the toe of gentle slopes and effectively prevents the collapse of bank slopes in the *** new revetment structure proposed in this paper has signifi-cant ecological and economic effects,is easy to construct and feasible for standard production,and consequently has great application potential.

关键词： Mulberry straw arch ecological bank revetment field test

A Criterion for Subnormality of Subgroups in Finite Groups

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Acta Mathematica Sinica,English Series 2012年第8期28卷 1575-1580页

作者： hua quan WEI Hong Fei PAN Shu Qin DONG Xu SUN College of Mathematics and Information Sciences Guangxi University School of Mathematics Science Guangxi Teacher's Education University

Based on Wielandt＇s criterion for subnormality of subgroups in finite groups, we study 2-maximal subgroups of finite groups and present another subnormality criterion in finite solvable groups.

关键词： Finite group solvable group maximal subgroup subnormal subgroup semidirect

Tracking with nonlinear measurement model by coordinate rotation transformation

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Science China(Technological Sciences) 2014年第12期57卷 2396-2406页

作者： ZENG Tao LI Chun Xia LIU quan hua CHEN Xin Liang School of Information and Electronics Beijing Institute of Technology

A new filtering method is proposed to accurately estimate target state via decreasing the nonlinearity between radar polar measurements(or spherical measurements in three-dimensional(3D) radar) and target position in Cartesian coordinate. The degree of linearity is quantified here by utilizing correlation coefficient and Taylor series expansion. With the proposed method, the original measurements are converted from polar or spherical coordinate to a carefully chosen Cartesian coordinate system that is obtained by coordinate rotation transformation to maximize the linearity degree of the conversion function from polar/spherical to Cartesian coordinate. Then the target state is filtered along each axis of the chosen Cartesian coordinate. This method is compared with extended Kalman filter(EKF), Converted Measurement Kalman filter(CMKF), unscented Kalman filter(UKF) as well as Decoupled Converted Measurement Kalman filter(DECMKF). This new method provides highly accurate position and velocity with consistent estimation.

关键词： target tracking Kalman filtering nonlinear filtering decoupled nonlinearity

Changes in particulate and mineral-associated organic carbon with land use in contrasting soils

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Pedosphere 2023年第3期33卷 421-435页

作者： Sabina YEASMIN Balwant SINGH Cliff T.JOHNSTON quan hua Donald L.SPARKS Sydney Institute of Agriculture School of Life and Environmental SciencesThe University of SydneySydney NSW 2006(Australia) Department of Agronomy Bangladesh Agricultural UniversityMymensingh-2202(Bangladesh) Crop Soil and Environmental SciencesPurdue UniversityWest Lafayette IN 47907(USA) Australian Nuclear Science and Technology Organisation Locked Bag 2001Kirrawee DC NSW 2232(Australia) Department of Plant and Soil Sciences University of DelawareNewark DE 19716(USA)

Soil organic carbon(SOC)is the largest terrestrial carbon(C)stock,and the capacity of soils to preserve organic C(OC)varies with many factors,including land use,soil type,and soil *** investigated the effect of land use change on soil particulate organic matter(POM)and mineral-associated organic matter(MOM).Surface(0–10 cm)and subsurface(60–70 cm)samples were collected from paired sites(native and cropped)of four contrasting *** soils were separated into POM and MOM fractions,which were analyzed for mineralogy,OC,nitrogen,isotopic signatures,*** POM fractions of surface soils were relatively unaffected by land use change,possibly because of the continuous input of crop residues,whereas the POM fractions in corresponding subsurface soils lost more *** surface soils,MOM fractions dominated by the oxides of iron and aluminum(oxide-OM)lost more OC than those dominated by phyllosilicates and quartz,which was attributed to diverse organic matter(OM)input and the extent of OC saturation limit of *** contrast,oxide-OM fractions were less affected than the other two MOM fractions in the subsurface soils,possibly due to OC protection via organo-mineral *** deviations in isotopic signature(linked with vegetation)across the fractions suggested that fresh crop residues constituted the bulk of OM in surface soils(supported by greater14C).Increased isotopic signatures and lower14C in subsurface MOM fractions suggested the association of more microbially processed,aged OC with oxide-OM fractions than with the other MOM *** results reveal that the quantity and quality of OC after land use change is influenced by the nature of C input in surface soils and by mineral-organic association in subsurface soils.

关键词： land use change microbial decomposition organic carbon saturation organo-mineral association soil organic matter