Wind tunnel tests and CFD simulations for snow redistribution on 3D stepped flat roofs

Zhixiang Yu,Fu Zhu,Ruizhou Cao,Xiaoxiao Chen,Lei Zhao,Shichun Zhao 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.28 No.1

The accurate prediction of snow distributions under the wind action on roofs plays an important role in designing structures in civil engineering in regions with heavy snowfall. Affected by some factors such as building shapes, sizes and layouts, the snow drifting on roofs shows more three-dimensional characteristics. Thus, the research on three-dimensional snow distribution is needed. Firstly, four groups of stepped flat roofs are designed, of which the width-height ratio is 3, 4, 5 and 6. Silica sand with average radius of 0.1 mm is used to model the snow particles and then the wind tunnel test of snow drifting on stepped flat roofs is carried out. 3D scanning is used to obtain the snow distribution after the test is finished and the mean mass transport rate is calculated. Next, the wind velocity and duration is determined for numerical simulations based on similarity criteria. The adaptive-mesh method based on radial basis function (RBF) interpolation is used to simulate the dynamic change of snow phase boundary on lower roofs and then a time-marching analysis of steady snow drifting is conducted. The overall trend of numerical results are generally consistent with the wind tunnel tests and field measurements, which validate the accuracy of the numerical simulation. The combination between the wind tunnel test and CFD simulation for three-dimensional typical roofs can provide certain reference to the prediction of the distribution of snow loads on typical roofs.

Immobilization and Performance of Penicillin G Acylase on Magnetic Ni_0.7Co_0.3Fe₂O₄@SiO₂-CHO Nanocomposites

( Zhixiang Lv ),( Qingmei Yu ),( Zhou Wang ),( Ruijiang Liu ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.6

Magnetic Ni_0.7Co_0.3Fe₂O₄ nanoparticles that were prepared via the rapid combustion process were functionalized and modified to obtain magnetic Ni_0.7Co_0.3Fe2O₄@SiO₂-CHO nanocomposites, on which penicillin G acylase (PGA) was covalently immobilized. Selections of immobilization concentration and time of fixation were explored. Catalytic performance of immobilized PGA was characterized. The free PGA had greatest activity at pH 8.0 and 45 ℃ while immobilized PGA’s a ctivities p eaked at p H 7.5 and 4 5 ℃. Immobilized PGA had better thermal stability than free PGA at the range of 30-50 ℃ for different time intervals. The activity of free PGA would be 0 and that of immobilized PGA still retained some activities at 60 ℃ after 2 h. V_max and K_m of immobilized PGA were 1.55 mol/min and 0.15 mol/l, respectively. Free PGA’s V_max and K_m separately were 0.74 mol/min and 0.028 mol/l. Immobilized PGA displayed more than 50% activity after 10 successive cycles. We concluded that immobilized PGA with magnetic Ni_0.7Co_0.3Fe₂O₄@SiO₂-CHO nanocomposites could become a novel example for the immobilization of other amidohydrolases.

Modification of disused floral foam with polyethylene diamine for the removal of heavy metal ions

Yilin Yu,Jindeng Huang,Yingmin Liao,Zhixiang Lin,Xiaojia Huang 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.128 No.-

Floral foam (FF) based on phenol formaldehyde resin has been used widely for many years, but it is reusedrarely and the discarded FF is harmful to environment. Therefore, recycling of disused FF is interestingand highly required. In current study, a new strategy for reutilization of disused FF was proposed. FFwhich had been treated with NaOH solution was dipped in polyethyleneimine (PEI) solution to anchoractive amino groups on the framework of FF, and then glutaraldehyde was employed to cross-link theanchored PEI to obtain a novel adsorbent based on disused FF (PEI@FF). Due to the abundant aminogroups, the prepared adsorbent displayed satisfactory chelating ability towards heavy metal ions. Under the optimal synthesis and adsorption conditions, the PEI@FF was applied to remove Cu(II), Cd(II) and Pb(II) in environmental waters, and the removal rates varied from 91.4% to 95.6%, which weremuch higher than that achieved on unmodified FF (35–43%). Additionally, the PEI@FF exhibited goodbatch-to-batch preparation repeatability and acceptable number of cyclic utilization. The satisfactoryresults well evidence the proposed method is practicable for reutilization of discarded FF, and the presentstudy also supplies a new adsorbent for the high efficient removal of heavy metal ions.

Airflow over low-sloped gable roof buildings: Wind tunnel experiment and CFD simulations

Ruizhou Cao,Zhixiang Yu,Zhixiang Liu,Xiaoxiao Chen,Fu Zhu 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.4

In this study, the impact of roof slope on the flow characteristics over low-sloped gable roofs was investigated using steady computational fluid dynamics (CFD) simulations based on a k- SST turbulence model. A measurement database of the flow field over a scaled model of 15° was created using particle image velocimetry (PIV). Sensitivity analyses for the grid resolutions and turbulence models were performed. Among the three common Reynolds-averaged Navier-Stokes equations (RANS) models, the k- SST model exhibited a better performance, followed by the RNG model and then the realizable k- model. Next, the flow properties over the differently sloped (0° to 25°) building models were determined. It was found that the effect of roof slope on the flow characteristics was identified by changing the position and size of the separation bubbles, 15° was found to be approximately the sensitive slope at which the distribution of the separation bubbles changed significantly. Additionally, it is suggested additional attention focused on the distributions of the negative pressure on the windward surfaces (especially "5" ° and "10" ° roofs) and the possible snow redistribution on the leeward surfaces.

CFD-DEM modeling of snowdrifts on stepped flat roofs

Zhao, Lei,Yu, Zhixiang,Zhu, Fu,Qi, Xin,Zhao, Shichun Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.23 No.6

Snowdrift formation on roofs should be considered in snowy and windy areas to ensure the safety of buildings. Presently, the prediction of snowdrifts on roofs relies heavily on field measurements, wind tunnel tests and numerical simulations. In this paper, a new snowdrift modeling method by using CFD (Computational Fluid Dynamics) coupled with DEM (Discrete Element Method) is presented, including material parameters and particle size, collision parameters, particle numbers and input modes, boundary conditions of CFD, simulation time and inlet velocity, and coupling calculation process. Not only is the two-way coupling between wind and snow particles which includes the transient changes in snow surface topography, but also the cohesion and collision between snow particles are taken into account. The numerical method is applied to simulate the snowdrift on a typical stepped flat roof. The feasibility of using coupled CFD with DEM to study snowdrift is verified by comparing the simulation results with field measurement results on the snow depth distribution of the lower roof.

CFD-DEM modeling of snowdrifts on stepped flat roofs

Lei Zhao,Zhixiang Yu,Fu Zhu,Xin Qi,Shichun Zhao 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.23 No.6

Snowdrift formation on roofs should be considered in snowy and windy areas to ensure the safety of buildings. Presently, the prediction of snowdrifts on roofs relies heavily on field measurements, wind tunnel tests and numerical simulations. In this paper, a new snowdrift modeling method by using CFD (Computational Fluid Dynamics) coupled with DEM (Discrete Element Method) is presented, including material parameters and particle size, collision parameters, particle numbers and input modes, boundary conditions of CFD, simulation time and inlet velocity, and coupling calculation process. Not only is the two-way coupling between wind and snow particles which includes the transient changes in snow surface topography, but also the cohesion and collision between snow particles are taken into account. The numerical method is applied to simulate the snowdrift on a typical stepped flat roof. The feasibility of using coupled CFD with DEM to study snowdrift is verified by comparing the simulation results with field measurement results on the snow depth distribution of the lower roof.

Wind Tunnel Test of Wind Load on a Typical Cross Line High-Speed Railway Station

Lei Zhao,Zhixiang Yu,Xin Qi,Hu Xu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.10

In order to study the influence of the layout of station buildings on the wind field characteristic, wind tunnel tests of wind load on the main roof and platform canopy of the Jinan West Railway Station are presented in this paper. Four 1:250-scale rigid models of the station with different characteristics were made. Not only the wind loading of the first phase station, but also the interference effect of the extension of the second phase station, the longitudinal gap of the platform canopy and the blocking rate of the interchange corridor on wind loading of the station were studied. The results show that the station roof, especially the overhanging eave mainly subjected to wind suction. Although the longitudinal gap of the platform canopy increases the turbulence intensity, the wind pressure on the upper and lower surface of the platform canopy tend to weaken each other. The extension of the second phase station will change the wind load characteristic of the first phase station roof and platform canopy obviously. Under specific wind angle, wind loading on large area of the platform canopy will change from wind suction to wind pressure. With the increase of blocking rate of the interchange corridor, both the wind pressure and wind suction of the platform canopy will be intensified.

The improved Shark Search Approach for Crawling Large-scale Web Data

Youwei Yuan,Dou Chen,Yong Li,Dongjin Yu,Lamei Yan,Zhixiang Zhu 보안공학연구지원센터 2014 International Journal of Multimedia and Ubiquitous Vol.9 No.8

Chlorogenic acid accumulation and related gene expression in peach fruit

Yan Juan,Su Ziwen,Guo Shaolei,Zhang Minghao,Zhang Binbin,Cai Zhixiang,Shen Zhijun,Ma Ruijuan,Yu Mingliang 한국원예학회 2022 Horticulture, Environment, and Biotechnology Vol.63 No.3

To reveal the molecular mechanism in the accumulation of chlorogenic acids (CGAs) in peach (Prunus persica) fruit during growth and development, CGA contents in the flesh of the three peach cultivars ‘Ruiguang 18’, ‘Heiyoutao’, and ‘Beijingyixianhong’ were determined. The expression levels of CGA metabolism-related genes were analyzed based on transcriptome data (RNA-seq). These candidate genes were then screened and real-time fluorescent quantitative PCR (qRT-PCR) was performed to verify their expression. The results showed that the content of total CGAs, 5-O-caffeoylquinic acid and 3-O-caffeoylquinic acid, in the flesh of ‘Ruiguang 18’ exhibited a decreasing trend during fruit development, and there was a great drop at maturity stage (P < 0.05). The three contents in ‘Heiyoutao’ increased first at stage S2 (P < 0.05) and then decreased significantly (P < 0.05). In ‘Beijingyixianhong’, they stayed stable in the early stages, then total CGAs and 3-O-caffeoylquinic acid decreased significantly at the maturity stage (P < 0.05). RNA-seq transcriptome data analysis and qRT-PCR expression analysis showed that the accumulation of CGAs in fruit flesh was mainly affected by the expression of Prupe.3G100800 (PpHCT) and Prupe.3G107300 (Pp4CL), and their expression levels were highly consistent with total CGA content. Thus, we concluded that Prupe.3G100800 (PpHCT) and Prupe.3G107300 (Pp4CL) are the key genes for CGAs synthesis in peach flesh.

Identification and comparative profiling of microRNAs in wild-type Xanthoceras sorbifolia and its double flower mutant

Yan Ao,Yanwei Wang,Lei Chen,Tao Wang,Haiyan Yu,Zhixiang Zhang 한국유전학회 2012 Genes & Genomics Vol.34 No.5

MicroRNAs are small, non-coding RNAs that regulate gene expression post-transcriptionally and have crucial roles in plant biological and metabolic processes. To date, there has been no report concerning miRNAs in Xanthoceras sorbifolia, one of the most important woody energy plants for biofuel production. To study the roles of miRNAs during floral organ differentiation and development in X. sorbifolia, two small RNA libraries were constructed from the flower buds of simple flowers (wild-type) and double flowers (mutant). Each library was sequenced individually and generated over 33 million raw reads in total. Forty-three conserved miRNAs belonging to 30families and 10 novel miRNAs were identified. The expressions of a selected group of conserved and novel miRNAs were validated by qRT-PCR. Target gene prediction identified 230 target genes for most of the conserved and novel miRNAs. Fifteen miRNAs were demonstrated to be differentially ex-pressed between wild-type and mutant. This is the first study to identify conserved and novel miRNAs and profile their expression changes during floral organ differentiation and development in X. sorbifolia.