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Understanding the microscopic moisture migration in pore space using DEM simulation

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第2期7卷 171-177页

作者： yuan Guo xiong(Bill) yu Department of Civil Engineering Case Western Reserve University

The deformation of soil skeleton and migration of pore fluid are the major factors relevant to the triggeringof and damages by liquefaction. The influence of pore fluid migration during earthquake has beendemonstrated from recent model experiments and field case studies. Most of the current liquefactionassessment models are based on testing of isotropic liquefiable materials. However the recent NewZealand earthquake shows much severer damages than those predicted by existing models. A fundamentalcause has been contributed to the embedded layers of low permeability silts. The existence ofthese silt layers inhibits water migration under seismic loads, which accelerated liquefaction and causeda much larger settlement than that predicted by existing theories. This study intends to understand theprocess of moisture migration in the pore space of sand using discrete element method （DEM） *** were conducted on consolidated undrained triaxial testing of sand where a cylindersample of sand was built and subjected to a constant confining pressure and axial loading. The porositydistribution was monitored during the axial loading process. The spatial distribution of porosity changewas determined, which had a direct relationship with the distribution of excess pore water pressure. Thenon-uniform distribution of excess pore water pressure causes moisture migration. From this, themigration of pore water during the loading process can be estimated. The results of DEM simulationshow a few important observations：（1） External forces are mainly carried and transmitted by the particlechains of the soil sample; （2） Porosity distribution during loading is not uniform due to nonhomogeneoussoil fabric （i.e. the initial particle arrangement and existence of particle chains）; （3）Excess pore water pressure develops differently at different loading stages. At the early stage of loading,zones with a high initial porosity feature higher porosity changes under the influence of e

关键词： Moisture migration Consolidated undrained triaxial test Particle chains Porosity distribution Pore water pressure

Towards safe and comfortable high-speed transportation infrastructure

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第11期13卷 799-801页

作者： Ren-peng CHEN xiong (Bill) yu MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Department of Civil EngineeringZhejiang UniversityHangzhou 310058China Department of Civil Engineering Case Western Reserve UniversityClevelandOhio 44106USA

In the past decades,we have witnessed the rapid development of high-speed transportation infrastructure,such as high-speed railways,urban subways,expressways,and airfields *** a major effort in transportation infrastructure development,China plans to build 20 000 km of high-speed rail network by the year of 2020 with design speed up to 500 km/*** such a fast pace,ensuring the safe and comfortable high-speed transportation presents major technical challenges to the design,construction,and maintenance of high performance infrastructure.

关键词：交通基础设施建设舒适安全高速铁路城市地铁高速公路交通运输铁路网络

Expression and immunoreactivity of HCV/HBV epitopes

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World Journal of Gastroenterology 2005年第41期11卷 6440-6444页

作者： Xin-yu xiong Xiao Liu yuan-Ding Chen Institute of Medical Biology Chinese Academy of Medical Sciences and Peking Union Medical College Kunming 650118 Yunnan Province China

AIM： To develop the epitope-based vaccines to prevent Hepatitis C virus （HCV）/Hepatitis B virus （HBV） infections. METHODS： The HCV core epitopes C1 STNPKPQRKTKRNTNRRPQD （residuals aa2-21） and C2 VKFPGGGQIVGGVYLLPRR （residuals aa22-40）, envelope epitope E GHRMAWDMMMNWSP （residuals aa315-328） and HBsAg epitope S CTTPAQGNSMFPSCCCTKPTDGNC （residuals aa124-147） were displayed in five different sites of the flock house virus capsid protein as a vector, and expressed in E. coli cells （pET-3 system）. Immunoreactivity of the epitopes with anti-HCV and anti-HBV antibodies in the serum from hepatitis C and hepatitis B patients were determined. RESULTS： The expressed chimedc protein carrying the HCV epitopes C1, C2, E （two times）, L3C1-I2E-L1C2- L2E could react with anti-HCV antibodies. The expressed chimeric protein carrying the HBV epitopes S, I3S could react with anti-HBs antibodies. The expressed chimeric proteins carrying the HCV epitopes C1, C2, E plus HBV epitope S, L3C1-I2E-L1C2-L2E-I3S could react with anti- HCV and anti-HBs antibodies. CONCLUSION： These epitopes have highly specific and sensitive immunoreaction and are useful in the development of epitope-based vaccines.

关键词： HCV HBV Epitope-based vaccine Recombinant Xmmunoreactivity

Spindown of magnetars:quantum vacuum friction?

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Research in Astronomy and Astrophysics 2016年第1期16卷 73-78页

作者： Xue-yu xiong Chun-yuan Gao Ren-Xin Xu School of Physics and State Key Laboratory of Nuclear Physics and Technology Peking University

Magnetars are proposed to be peculiar neutron stars which could power their X-ray radiation by super-strong magnetic fields as high as 〉 10^（14） ***,no direct evidence for such strong fields has been obtained till now,and the recent discovery of low magnetic field magnetars even indicates that some more efficient radiation mechanism than magnetic dipole radiation should be *** this paper,quantum vacuum friction（QVF） is suggested to be a direct consequence of super-strong surface fields,therefore the magnetar model could then be tested further through QVF *** high surface magnetic field of a pulsar interacting with the quantum vacuum results in a significantly high spindown rate（P）.It is found that a QVF dominates the energy loss of pulsars when the pulsar＇s rotation period and its first derivative satisfy the relationship P^3P 〉 0.63 ×10^（-16）ξ^（-4） s^2,whereξ is the ratio of the surface magnetic field over the dipole magnetic *** the ＂QVF ＋ magnetodipole＂ joint braking scenario,the spindown behavior of magnetars should be quite different from that in the pure magnetodipole *** are expecting these results could be tested by magnetar candidates,especially low magnetic field cases,in the future.

关键词： ulsars: general -- radiation: dynamics -- stars: magnetars -- stars: neutron

Thermodynamically controllable synthesis of ZIF-8 exposing different facets and their applications in single atom catalytic oxygen reduction reactions

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Nano Research 2023年第7期16卷 9618-9624页

作者： Runze Ma Qiheng Li Jun Yan yu Tao Shouyao Hu Donghao Liu Jiaxin Gong yu xiong College of Chemistry and Chemical Engineering Central South UniversityChangsha 410083China Beijing Advanced Innovation Center for Materials Genome Engineering Institute of Solid State ChemistryUniversity of Science and Technology BeijingBeijing 100083China

The development of thermodynamically controllable synthetic strategy to manipulate the morphology of ZIF-8 without capping agent is essential to help understanding their facet effect and the structure-activity relationship of single atom catalysts derived from ***,we prepared ZIF-8 with different morphologies(cube,truncated rhombododecahedral and rhombododecahedral)and thus area ratio of exposed{100},{110}facets by a thermodynamically controllable synthetic *** the reaction proceeds under room temperature(30℃),the assembling of ZIF-8 followed an area-reducing layered growth mode,while switched to an integral layered growth mode at lower temperature-40℃.Moreover,this strategy also works to obtain ZIF-8 encapsulated with metal precursors(Fe(acac)_(3),Cu(acac)_(2)and Co(acac)_(2)).Single Fe atom anchored on nitrogen doped carbon catalysts(SA-Fe/CN)derived from Fe-ZIF-8 retain their original morphologies and the unsaturated surface-active sites on{100}facet,which further displays different catalytic performance towards oxygen reduction reaction(ORR).This work not only reveals the different growth pattern of ZIF-8,but also points out a new direction for designing and synthesizing MOFs with different morphology rationally.

关键词： ZIF-8 facet effect single atom catalyst oxygen reduction reaction

Determining axial dispersion coefficients of pilot-scale annular pulsed disc and doughnut columns

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Chinese Journal of Chemical Engineering 2020年第6期28卷 1504-1513页

作者： xiong yu Han Zhou Qiang Zheng Shan Jing Wenjie Lan Shaowei Li Institute of Nuclear and New Energy Technology Tsinghua UniversityBeijing 100084China State Key Laboratory of Heavy Oil Processing China University of Petroleum(Beijing)Beijing 102249China State Key Laboratory of Chemical Engineering Tsinghua UniversityBeijing 100084China

In this study,a computational fluid dynamics(CFD)method was adopted to calculate axial dispersion coefficients of annular pulsed disc and doughnut columns(APDDCs).Passive tracer was uniformly injected by pulse input at the continuous phase inlet,and its concentration governing equation was solved in liquid–liquidtwo-phase flow *** residence time distributions(RTDs)were obtained using the surface monitoring *** adopted RTD–CFD method was verified by comparing the axial dispersion coefficient between simulation and experimental results in the ***,in pilot-scale APDDCs,the axial dispersion coefficients predicted by the CFD–RTD method were approximately three times larger than experimental results determined by the steady-state concentration profile *** experimental method was demonstrated to be insensitive to the variation of the axial dispersion *** CFD–RTD method was more recommended to determine the axial dispersion *** was found that the axial dispersion coefficient increased with an increase in pulsation intensity,column diameter,and plate spacing,but was little affected by the throughput.

关键词： Axial dispersion Computational fluid dynamics Residence time distribution Annular-pulsed disc and doughnut column

Effect of stress paths on failure mechanism and progressive damage of hard-brittle rock

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Journal of Mountain Science 2021年第9期18卷 2486-2502页

作者： CHEN Zi-quan HE Chuan HU xiong-yu MA Chun-chi Key Laboratory of Transportation Tunnel Engineering Ministry of EducationSouthwest Jiaotong UniversityChengdu 610031China Key Laboratory of Engineering Structures of Heavy Haul Railway Ministry of EducationCentral South UniversityChangsha 410075China State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu 610059China

During deep buried hard-brittle rock tunnel excavation,the surrounding rock experiences a complicated stress path and stress adjustment *** the adjusted stress exceeds the ultimate bearing capacity of rockmass,a rock failure mode defined as stress-cracking type will *** order to investigate the effect of stress paths on failure mechanism and progressive damage of deep-buried rockmass,the cyclic loading-unloading,loading-unloading,uniaxial,conventional and unloading triaxial compression tests on samples of hard-brittle sandstone were *** to the experimental results,increase in the confining pressure was beneficial to improve the mechanical parameters of rock,but it will reduce the brittle failure *** with conventional triaxial compression,the sandstone under unloading state had more remarkable stress drop and unstable failure ***,it was found that the energy dissipation and energy release in the whole process of rock deformation were the internal power of driven rock progressive *** the increase of confining pressure,the energy hardening and energy accumulation features of rock were weakened,while the progressive damage evolution characteristics could be *** unloading state,more energy could be converted into elastic energy in the energy softening phase(σeb-σP),so that the prepeak damage rate of rock was lower than that of conventional triaxial compression ***,the energy dissipation rate of rock after peak strength decreased linearly with the increase of confining pressure under conventional triaxial compression state,while in unloading state it showed the opposite law.

关键词： Hard-brittle rock Stress path Confining pressure Failure mechanism Progressive damage

A non-destructive method to measure the thermal properties of frozen soils during phase transition

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第2期7卷 155-162页

作者： Bin Zhang Chanjuan Han xiong(Bill) yu Michael Baker International 100 Airside Drive Moon Township PA 15108 USA Department of Civil Engineering Case Western Reserve University

Frozen soils cover about 40% of the land surface on the earth and are responsible for the global energybalances affecting the climate. Measurement of the thermal properties of frozen soils during phasetransition is important for analyzing the thermal transport process. Due to the involvement of phasetransition, the thermal properties of frozen soils are rather complex. This paper introduces the uses of amultifunctional instrument that integrates time domain reflectometry （TDR） sensor and thermal pulsetechnology （TPT） to measure the thermal properties of soil during phase transition. With this method,the extent of phase transition （freezing/thawing） was measured with the TDR module; and the correspondingthermal properties were measured with the TPT module. Therefore, the variation of thermalproperties with the extent of freezing/thawing can be obtained. Wet soils were used to demonstrate theperformance of this measurement method. The performance of individual modules was first validatedwith designed experiments. The new sensor was then used to monitor the properties of soils duringfreezingethawing process, from which the freezing/thawing degree and thermal properties weresimultaneously measured. The results are consistent with documented trends of thermal propertiesvariations. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

关键词： Frozen soil Phase change materials Thermal conductivity Heat capacity Sensor fusion

Characteristics of Heat Flux Through Slag Film of Mold Slag Used for High Al-TRIP Steel Casting

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Journal of Iron and Steel Research International 2010年第5期17卷 11-16页

作者： yu xiong WEN Guang-hua TANG Ping YANG Bo School of Materials Science and Engineering Chongqing University Chongqing 400044 China

Due to the high content of the Al-TRIP steel, Al reacts with SiO2 in the mold slag during the casting process, which results in the increase of ωAl2O3 /ωSiO2 ratio and the Al2O3 content, respectively; the characteristic of heat transfer through the slag film is then changed, which influences the smooth operation of the continuous casting process. The heat flux simulator of mold slag film was used to study the change tendency of the heat flux density through slag film and the results were discussed; at the same time, the characteristics of the crystals in the No. 15 mold slag were determined by BSE and XRD. The results obtained show that heat flux density decreases with the increase of ωAl2O3 /ωSiO2 ratio. Heat flux density increases with the increase of Li2O and/or B2O3 content in the mold slag which contains 30 % of Al2 O3. Compared with the heat flux density of common slag of peritectic steel, a suitable mold slag containing 4% of B2O3 and 4% of Li2O is designed. The heat flux density is 0. 645 MW/m^2 when ωAl2O3 /ωSiO2 = 1. 46. Under this experimental condition, the CaF2 crystals precipitate in the mold slag used for Al-TRIP steel.

关键词： TRIP steel heat flux density ωAl2O3 /ωSiO2 ratio Li2O B2O3