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Experimental investigation of the effect of flow turbulence and sediment transport patterns on the adsorption of cadmium ions onto sediment particles

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Journal of Environmental Sciences 2007年第6期19卷 696-703页

作者： HUAng Sui-liang ng Chiu-on guo qi-zh.ng Numerical Simulation Group for Water Environment College of Environmental Science and Engineering Nankai University Tianjin 300071 China Deptartment of Mechanical Engineering The University of Hong Kong Pokfulam Road Hong Kong Department of Civil and Environmental Engineering Rutgers State University of New Jersey 623 Bowser Road Piscataway NJ 08854 USA

The mechanism of flow turbulence, sediment supply conditions, and sediment transport patterns that affect the adsorption of cadmium ions onto sediment particles in natural waters are experimentally simulated and studied both in batch reactors and in a turbulence simulation tank. By changing the agitation conditions, the sediment transport in batch reactors can be categorized into bottom sediment-dominated sediment and suspended sediment-dominated sediment. It is found that the adsorption rate of bottom sediment is much less than that of suspended sediment, but the sediment transport pattern does not affect the final （equilibrium） concentration of dissolved cadmium. This result indicates that the parameters of an adsorption isotherm are the same regardless of the sediment transport pattern. In the turbulence simulation tank, the turbulence is generated by harmonic grid-stirred motions, and the turbulence intensity is quantified in terms of eddy diffusivity, which is equal to 9.84F （F is the harmonic vibration frequency） and is comparable to natural surface water conditions. When the turbulence intensity of flow is low and sediment particles stay as bottom sediment, the adsorption rate is significantly low, and the adsorption quantity compared with that of suspended sediment is negligible in the 6 h duration of the experiment. This result greatly favors the simplification of the numerical modeling of heavy metal pollutant transformation in natural rivers. When the turbulence intensity is high but bottom sediment persists, the rate and extent of descent of the dissolved cadmium concentration in the tank noticeably increase, and the time that is required to reach adsorption equilibrium also increases considerably due to the continuous exchange that occurs between the suspended sediment and the bottom sediment. A comparison of the results of the experiments in the batch reactor and those in the turbulence simulation tank reveals that the adsorption ability of the sedimen

关键词： water flow sediment transport pollutant interactions turbulence, adsorption

Three-dimensional numerical analysis of plant-soil hydraulic interactions on pore water pressure of vegetated slope under different rainfall patterns

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第9期16卷 3696-3706页

作者： Haowen guo Charles Wang Wai ng qi zh.ng Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyHong KongChina

Understanding the pore water pressure distribution in unsaturated soil is crucial in predicting shallow landslides triggered by rainfall,mainly when dealing with different temporal patterns of rainfall ***,the hydrological response of vegetated slopes,especially three-dimensional(3D)slopes covered with shrubs,under different rainfall patterns remains unclear and requires further *** address this issue,this study adopts a novel 3D numerical model for simulating hydraulic interactions between the root system of the shrub and the surrounding *** series of numerical parametric studies are conducted to investigate the influences of slope inclination,rainfall pattern and rainfall *** rainfall patterns(advanced,bimodal,delayed,and uniform)and two rainfall durations(4-h intense and 168-h mild rainfall)are considered to study the hydrological response of the *** computed results show that 17%higher transpiration-induced suction is found for a steeper slope,which remains even after a short,intense rainfall with a 100-year return *** extreme rainfalls with advanced(PA),bimodal(PB)and uniform(PU)rainfall patterns need to be considered for the short rainfall duration(4 h),while the delayed(PD)and uniform(PU)rainfall patterns are highly recommended for long rainfall durations(168 h).The presence of plants can improve slope stability markedly under extreme rainfall with a short duration(4 h).For the long duration(168 h),the benefit of the plant in preserving pore-water pressure(PWP)and slope stability may not be sufficient.

关键词： Root-soil interactions Rainfall patterns Slope stability Three-dimensional(3D)

Maintaining moderate levels of hypochlorous acid promotes neural stem cell proliferation and differentiation in the recovery phase of stroke

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Neural Regeneration Research 2025年第3期20卷 845-857页

作者： Lin-Yan Huang Yi-De zh.ng Jie Chen Hai-Di Fan Wan Wang Bin Wang Ju-Yun Ma Peng-Peng Li Hai-Wei Pu Xin-Yian guo Jian-Gang Shen Su-Hua qi School of Medical Technology Xuzhou Key Laboratory of Laboratory DiagnosticsXuzhou Medical UniversityXuzhouJiangsu ProvinceChina School of Pharmacy Xuzhou Medical UniversityXuzhouJiangsu ProvinceChina Department of Laboratory Medicine Branch Hospital of Huai’an First People’s HospitalHuai’anJiangsu ProvinceChina Department of Laboratory Medicine the Affiliated Hospital of Xuzhou Medical UniversityXuzhouJiangsu ProvinceChina School of Chinese Medicine The University of Hong KongHong Kong Special Administrative RegionChina

It has been shown clinically that continuous removal of ischemia/reperfusion-induced reactive oxygen species is not conducive to the recovery of late ***,previous studies have shown that excessive increases in hypochlorous acid after stroke can cause severe damage to brain *** previous studies have found that a small amount of hypochlorous acid still exists in the later stage of stroke,but its specific role and mechanism are currently *** simulate stroke in vivo,a middle cerebral artery occlusion rat model was established,with an oxygen-glucose deprivation/reoxygenation model established in vitro to mimic *** found that in the early stage(within 24 hours)of ischemic stroke,neutrophils produced a large amount of hypochlorous acid,while in the recovery phase(10 days after stroke),microglia were activated and produced a small amount of hypochlorous ***,in acute stroke in rats,hypochlorous acid production was prevented using a hypochlorous acid scavenger,taurine,or myeloperoxidase inhibitor,4-aminobenzoic acid *** results showed that high levels of hypochlorous acid(200μM)induced neuronal apoptosis after oxygen/glucose deprivation/***,in the recovery phase of the middle cerebral artery occlusion model,a moderate level of hypochlorous acid promoted the proliferation and differentiation of neural stem cells into neurons and *** suggests that hypochlorous acid plays different roles at different phases of cerebral ischemia/reperfusion *** levels of hypochlorous acid(5 and 100μM)promoted nuclear translocation ofβ-*** transfection of single-site mutation plasmids,we found that hypochlorous acid induced chlorination of theβ-catenin tyrosine 30 residue,which promoted nuclear ***,our study indicates that maintaining low levels of hypochlorous acid plays a key role in the recovery of neurological function.

关键词： cell differentiation cerebral ischemia/reperfusion injury chlorination hypochlorous acid microglia neural stem cell neurogenesis nuclear translocation stroke β-catenin

Rotating electroosmotic flow of an Eyring fluid

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Acta Mechanica Sinica 2017年第2期33卷 295-315页

作者： Cheng qi Chiu-On ng Department of Mechanical Engineering The University of Hong Kong Hong Kong China

A perturbation analysis is presented in this paper for the electroosmotic (EO) flow of an Eyring fluid through a wide rectangular microchannel that rotates about an axis perpendicular to its own. Mildly shear-thinning rheology is assumed such that at the leading order the problem reduces to that of Newtonian EO flow in a rotating channel, while the shear thinning effect shows up in a higher-order problem. Using the relaxation time as the small ordering parameter, analytical solutions are deduced for the leading- as well as first-order problems in terms of the dimensionless Debye and rotation parameters. The velocity profiles of the Ekman-electric double layer (EDL) layer, which is the boundary layer that arises when the Ekman layer and the EDL are comparably thin, are also deduced for an Eyring fluid. It is shown that the present perturbation model can yield results that are close to the exact solutions even when the ordering parameter is as large as order unity. By this order of the relaxation time parameter, the enhancing effect on the rotating EO flow due to shear-thinning Eyring rheology can be significant.

关键词： Electroosmotic flow Eyring fluid Rotating channel

Modelling the water diversion of a sustainable cover system under humid climates

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2429-2440页

作者： Haowen guo Charles Wang Wai ng qi zh.ng Chuanxiang Qu Liwen Hu Shenzhen Research Institute of Hong Kong University of Science and Technology Shenzhen518057China Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyHong Kong SAR999077China CCCC Fourth Harbor Engineering Institute Co. LtdGuangzhou510230China

Extreme rainfall significantly threatens the safety of the landfill cover system,especially under humid *** study aims to provide design recommendations for a sustainable landfill cover system consisting of a low-permeability soil layer underlying a two-layer capillary barrier for humid ***,the numerical back-analysis was conducted for verification against a series of flume model ***,a parametric study was performed to investigate the effects of inclination angle,particle size and layer thickness on the lateral diversion length(DL)of the three-layer cover system under the 100-year return period rainfall of humid *** results show that the water lateral DL of the cover system can be greatly enhanced by increasing the inclination angle from 3°to 18°.Moreover,the bottom layer of the cover system with a coarser d10 was more susceptible to the impact of the heavy rainfall,while this can be alleviated by increasing the thickness of the bottom layer.A dimensionless number,defined as the ratio of thickness and d_(10) of the bottom layer,is proposed for designing lateral diversion of the three-layer cover system under humid *** preserve the maximum DL,it is suggested that the proposed dimensionless number should be larger than 95 and 110 for the design of rainfall events with 50-year and 100-year return periods for humid climates,respectively.

关键词： Unsaturated soil Recycling Construction waste Three-layer landfill cover Water infiltration

Three-year field study on grass growth and soil hydrological properties in biochar-amended soil

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2764-2774页

作者： Haowen guo Charles Wang Wai ng Junjun Ni qi zh.ng Yuchen Wang Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyHong KongChina School of Transportation Southeast UniversityNanjingChina

Field monitoring was conducted to investigate and quantify the long-term effects of peanut shell biochar on soil-grass interaction over three *** 10 m5 m grassed plots were constructed in completely decomposed granitic *** of them were amended,respectively,with 5%and 10%biochar contents(m^(3)/m^(3))for grass growth,while the third was without biochar *** the threeyear monitoring,plant characteristics,saturated water permeability(k_(s))of grassed soil and soil suction were *** monitored results show that the grass leaf area index(LAI)and root length density(RLD)with biochar amendment were improved by 38%and 200%,*** the grassed plot without biochar,a threshold RLD existed with a value of 1.7 cm/cm^(3),beyond which k_(s) raised *** threshold RLD increased by 52%when biochar content increased from 0%to 10%.This implies that biochar may restrict the increase in k_(s) of grassed soil due to the rise in the threshold *** presence of biochar and grass can retain over 100%higher suction after heavy rainfalls,while 54%lower peak suction under evapotranspiration(ET)compared with the non-amended *** can alleviate the negative effects on hydraulic properties caused by plant growth and reduce ET-induced excessive water loss.A 5%peanut shell biochar content is recommended for the long-term management of vegetated earthen infrastructures.

关键词： Soil-grass interaction Biochar Long-term Water infiltration Soil drying

Analysis of a landfill cover without geomembrane using varied particle sizes of recycled concrete

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第5期15卷 1263-1273页

作者： Charles Wang Wai ng Cheuk Lam ng Junjun Ni Haowen guo qi zh.ng qiang Xue Rui Chen Department of Civil and Environmental Engineering Hong Kong University of Science and TechnologyHong KongChina School of Transportation Southeast UniversityNanjingChina State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Department of Civil and Environmental Engineering Shenzhen Graduate SchoolHarbin Institute of TechnologyShenzhenChina

Previous studies have demonstrated the effectiveness of a novel three-layer landfill cover system constructed with recycled concrete aggregates(RCAs)without geomembrane in both laboratory and ***,no systematic investigation has been carried out to optimize the combination of the particle sizes for fine-grained RCAs(FRC)and coarse-grained RCAs(CRC)that can be used for the three-layer landfill cover *** aim of this paper is to assist engineers in designing the three-layer landfill cover system under a rainfall of 100-year return period in humid climate conditions using an easily controlled soil parameter D10 of *** numerical study reveals that when D10 of FRC increases from 0.05 mm to 0.16 mm,its saturated permeability increases by 10 *** a result,a larger amount of rainwater infiltrates into the cover system,causing a higher lateral diversion in both the top FRC and middle CRC *** further changes in the lateral diversion are observed when the D10 value of FRC is larger than 0.16 *** the particle sizes of FRC and CRC layers are shown to have a minor influence on the percolation under the extreme rainfall *** implies that the selection of particle sizes for the FRC and CRC layers can be based on the availability of *** it is well known that the bottom layer of the cover system should be constructed with very fine-grained soils if possible,this study provides an upper limit to the particle size that can be used in the bottom layer(D10 not larger than 0.02 mm).With this limit,the three-layer system can still minimize the water percolation to meet the design criterion(30 mm/yr)even under a 100-year return period of rainfall in humid climates.

关键词： Capillary barrier Landfill cover Particle size Recycled concrete

New materials and designs for 2D-based infrared photodetectors

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Nano Research 2023年第2期16卷 3074-3103页

作者： Huitian guo Weihong qi State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi’an 710072China Shandong Laboratory of Yantai Advanced Materials and Green Manufacturing Yantai 264006China

Infrared photodetectors have attracted much attention considering their wide civil and military ***-dimensional(2D)materials offer new opportunities for the development of costless,high-level integration and high-performance infrared *** the advent of a broad investigation of infrared photodetectors based on graphene and transition metal chalcogenides(TMDs)exhibiting unique properties in recent decades,research on the better performance of 2D-based infrared photodetectors has been extended to a larger scale,including explorations of new materials and artificial structure *** this review,after a brief background introduction,some major working mechanisms,including the photovoltaic effect,photoconductive effect,photogating effect,photothermoelectric effect and bolometric effect,are briefly ***,the discussion mainly focuses on the recent progress of three categories of 2D materials beyond graphene and *** transition metal dichalcogenides,black phosphorus and arsenic black phosphorous and 2D ternary compounds are great examples of explorations of mid-wavelength or even long-wavelength 2D infrared ***,four types of rational structure designs,including type-II band alignments,photogating-enhanced designs,surface plasmon designs and ferroelectric-enhanced designs,are discussed to further enhance the performance via diverse mechanisms,which involve the narrower-bandgap-induced interlayer exciton transition,gate modulation by trapped carriers,surface plasmon polaritons and ferroelectric polarization in ***,applications including imaging,flexible devices and on-chip integration for 2D-based infrared photodetectors are ***,a summary of the state-of-the-art research status and personal discussion on the challenges are delivered.

关键词： two-dimensional(2D)materials infrared photodetectors noble transition metal dichalcogenides black phosphorus layered ternary compounds structure designs

Experimental study on the relation between the water content of surface soil and the acoustic wave

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Acta Seismologica Sinica(English Edition) 2001年第5期14卷 571-576页

作者： guo Zi-qi 1. Institute of Remote Sensing Application Chinese Academy of Sciences 100101 Beijing China 2. Institute of Geophysics China Seismological Bureau 100081 Beijing China

In order to investigate the relation between the water content changing of surface soil and micro-quake recorded before earthquakes, we carried out a simulation experiment in laboratory. Its purpose is to explore whether the acoustic wave generated by micro-fracturing before earthquake are able to change water content of surface soil, so as to understand the relation between thermal anomaly in the remote sensing image got from the seismogenic area and the coming earthquake. The result of the experiment shows that when the acoustic wave enters into the surface soil the water content here increases on the background of decreasing due to natural evaporation. In the meantime, temperature here decreases.

关键词： acoustic wave remote sensing water content in soil micro-fracturing