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Nonlinear dynamics and failure wind velocity analysis of urban trees
Xiaoqiu Ai,Yingyao Cheng,Yong-Bo Peng 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.22 No.1
With an aim to assess the wind damage to urban trees in more realistic conditions, the nonlinear dynamics of structured trees subjected to strong winds with different levels is investigated in the present paper. For the logical treatment of dynamical behavior of trees, material nonlinearities of green wood associated with tree biomechanics and geometric nonlinearity of tree configuration are included. Applying simulated fluctuating wind velocity to the numerical model, the dynamical behavior of the structured tree is explored. A comparative study against the linear dynamics analysis usually involved in the previous researches is carried out. The failure wind velocity of urban trees is then defined, whereby the failure percentages of the tree components are exposed. Numerical investigations reveal that the nonlinear dynamics analysis of urban trees results in a more accurate solution of wind-induced response than the classical linear dynamics analysis, where the nonlinear effect of the tree behavior gives rise to be strengthened as increasing of the levels of wind velocity, i.e., the amplitude of 10-min mean wind velocity. The study of relationship between the failure percentage and the failure wind velocity provides a new perspective towards the vulnerability assessment of urban trees likely to fail due to wind actions, which is potential to link with the practical engineering.
Nonlinear dynamics and failure wind velocity analysis of urban trees
Ai, Xiaoqiu,Cheng, Yingyao,Peng, Yongbo Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.22 No.1
With an aim to assess the wind damage to urban trees in more realistic conditions, the nonlinear dynamics of structured trees subjected to strong winds with different levels is investigated in the present paper. For the logical treatment of dynamical behavior of trees, material nonlinearities of green wood associated with tree biomechanics and geometric nonlinearity of tree configuration are included. Applying simulated fluctuating wind velocity to the numerical model, the dynamical behavior of the structured tree is explored. A comparative study against the linear dynamics analysis usually involved in the previous researches is carried out. The failure wind velocity of urban trees is then defined, whereby the failure percentages of the tree components are exposed. Numerical investigations reveal that the nonlinear dynamics analysis of urban trees results in a more accurate solution of wind-induced response than the classical linear dynamics analysis, where the nonlinear effect of the tree behavior gives rise to be strengthened as increasing of the levels of wind velocity, i.e., the amplitude of 10-min mean wind velocity. The study of relationship between the failure percentage and the failure wind velocity provides a new perspective towards the vulnerability assessment of urban trees likely to fail due to wind actions, which is potential to link with the practical engineering.
Esterification of free fatty acids in a rotor-stator spinning disc reactor
Yubin Wang,Xiaoqiu Tao,Jun Li,Siqi Zhang,Yang Jin,Ming Chen 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.8
Fatty acid methyl esters (FAMEs) were produced by the esterification of free fatty acids (FFA) with methanol, and sulfuric acid as the catalyst in a rotor-stator spinning disc reactor (RSSDR). The RSSDR, which shows excellent mixing efficiency and fast phase separation, was used as a novel continuous-flow esterification reactor. The influence of the variables (e.g., rotational speed, volume flow rate, rotor-stator distance, methanol-FFA molar ratio, catalyst dosage, and temperature) on esterification conversion () and productivity of FAMEs (PFAME) were investigated. It was found that the experimental parameters have a great impact on the and PFAME in the RSSDR system, due to the effect of micromixing intensity and residence time distribution. Furthermore, to compare with other traditional esterification reactors, the values of , PFAME, and PFAME per unit reactor volume (PFAME/VR) in the RSSDR were also employed to assess the performance for the production of FAMEs. It shows that the maximum values of PFAME, and PFAME/VR attained were 0.14mol/min and 3.06×102 mol/(mL min), respectively. Therefore, the RSSDR is proven to be an effective esterification reactor with high esterification conversion in comparison to conventional esterification reactors.
Field measurement and CFD simulation of wind pressures on rectangular attic
Yongbo Peng,Weijie Zhao,Xiaoqiu Ai 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.6
Wind pressure is a critical argument for the wind-resistant design of structures. The attempt, however, to explore the wind pressure field on buildings still encounters challenges though a large body of researches utilizing wind tunnel tests and wind field simulations were carried out, due to the difficulty in logical treatments on the scale effect and the modeling error. The full-scale measurement has not yet received sufficient attention. By performing a field measurement, the present paper systematically addresses wind pressures on the rectangular attic of a double-tower building. The spatial and temporal correlations among wind speed and wind pressures at measured points are discussed. In order to better understand the wind pressure distribution on the attic facades and its relationship against the approaching flow, a full-scale CFD simulation on the similar rectangular attic is conducted as well. Comparative studies between wind pressure coefficients and those provided in wind-load codes are carried out. It is revealed that in the case of wind attack angle being zero, the wind pressure coefficient of the cross-wind facades exposes remarkable variations along both horizontal and vertical directions; while the wind pressure coefficient of the windward facade remains stable along horizontal direction but exposes remarkable variations along vertical direction. The pattern of wind pressure coefficients, however, is not properly described in the existing wind-load codes.
Wind-induced fragility assessment of urban trees with structural uncertainties
Yongbo Peng,Zhiheng Wang,Xiaoqiu Ai 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.26 No.1
Wind damage of urban trees arises to be a serious issue especially in the typhoon-prone areas. As a family of tree species widely-planted in Southeast China, the structural behaviors of Plane tree is investigated. In order to accommodate the complexities of tree morphology, a fractal theory based finite element modeling method is proposed. On-site measurement of Plane trees is performed for physical definition of structural parameters. It is revealed that modal frequencies of Plane trees distribute in a manner of grouped dense-frequencies; bending is the main mode of structural failure. In conjunction with the probability density evolution method, the fragility assessment of urban trees subjected to wind excitations is then proceeded. Numerical results indicate that small-size segments such as secondary branches feature a relatively higher failure risk in a low wind level, and a relatively lower failure risk in a high wind level owing to windward shrinks. Besides, the trunk of Plane tree is the segment most likely to be damaged than other segments in case of high winds. The failure position tends to occur at the connection between trunk and primary branches, where the logical protections and reinforcement measures can be implemented for mitigating the wind damage.
Liu, Yulan,Han, Jie,Huang, Jingjing,Wang, Xiaoqiu,Wang, Fenglai,Wang, Junjun Asian Australasian Association of Animal Productio 2009 Animal Bioscience Vol.22 No.12
This study was conducted to determine whether L-arginine (Arg) supplementation could improve intestinal function in weaned pigs after an Escherichia coli lipopolysaccharide (LPS) challenge. Treatments included: i) non-challenged control (CONTR, pigs fed a control diet and injected with sterile saline); ii) LPS-challenged control (LPS, pigs fed the same control diet and challenged by injection with Escherichia coli LPS); iii) LPS+0.5% Arg (pigs fed a 0.5% Arg diet and challenged with LPS); and iv) LPS+1.0% Arg (pigs fed a 1.0% Arg diet and challenged with LPS). On d 16, pigs were administrated with LPS or sterile saline. D-xylose was orally administrated at 2 h following LPS challenge, and blood samples were collected at 3 h following LPS challenge. At 6 h post-challenge, pigs were sacrificed and intestinal mucosa samples were collected. Supplementation of Arg attenuated LPS-induced damage in gut digestive and barrier functions, as indicated by an increase in ileal lactase activity, and duodenal and ileal diamine oxidase activities (p<0.05). Arg administration also prevented the increase of jejunal malondialdehyde content and the decrease of ileal superoxide dismutase activity by LPS challenge (p<0.05). Furthermore, the jejunal nitric oxide level and inducible nitric oxide synthase activity were also improved after Arg supplementation (p<0.05). These results indicate that Arg supplementation has beneficial effects in alleviating the impairment of gut function induced by LPS challenge.
Lin, Yan,Wang, Junjun,Wang, Xiaoqiu,Wu, Weizong,Lai, Changhua Asian Australasian Association of Animal Productio 2013 Animal Bioscience Vol.26 No.3
This experiment was conducted to evaluate the development of T cells in intrauterine growth retarded (IUGR) piglets at different gestational stages, and tentatively explore the relationship between T cells development and the Notch signaling pathway. A total of 18 crossbred (Landrace${\times}$Large white) primiparous sows were mated at similar weights and estruses and euthanized at d 60, 90 and 110 of gestation with six replicates for each time point. One IUGR and one normal fetus were picked from each litter. The T-cell subsets, mRNA expression of Delta-like1, Delta-like4, Jagged1, and Notch2 genes in the thymus were investigated. Compared to normal piglets, $CD3^+CD4^-CD8^+$ cells in IUGR fetuses at d 90 was 0.13% lower (p<0.05). At d 110 of gestation $CD8^+$ T cells in IUGR fetuses was 0.19% lower (p<0.05). The percentage of $CD8^+$ T cells was 3.14% lower (p<0.05) of the total T cells in IUGR pigs at d 60. The abundance of Notch2 and Delta-like4 mRNA at d 110 was 20.93% higher and 0.77% (p<0.05) lower, and Delta-like1 mRNA at d 90 was 0.19% (p<0.05) higher compared to normal pigs. These results suggested that normal fetuses had a greater proportion of T-cell subsets at earlier gestation periods, and the Notch signaling pathway was likely partially responsible for these differences to some degree.
Wind-induced fragility assessment of urban trees with structural uncertainties
Peng, Yongbo,Wang, Zhiheng,Ai, Xiaoqiu Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.26 No.1
Wind damage of urban trees arises to be a serious issue especially in the typhoon-prone areas. As a family of tree species widely-planted in Southeast China, the structural behaviors of Plane tree is investigated. In order to accommodate the complexities of tree morphology, a fractal theory based finite element modeling method is proposed. On-site measurement of Plane trees is performed for physical definition of structural parameters. It is revealed that modal frequencies of Plane trees distribute in a manner of grouped dense-frequencies; bending is the main mode of structural failure. In conjunction with the probability density evolution method, the fragility assessment of urban trees subjected to wind excitations is then proceeded. Numerical results indicate that small-size segments such as secondary branches feature a relatively higher failure risk in a low wind level, and a relatively lower failure risk in a high wind level owing to windward shrinks. Besides, the trunk of Plane tree is the segment most likely to be damaged than other segments in case of high winds. The failure position tends to occur at the connection between trunk and primary branches, where the logical protections and reinforcement measures can be implemented for mitigating the wind damage.
Research on Data Heterogeneity in Enterprise Information Integration
Ruizhen Duan,Zhongwen Wang,Mingshan Chi,Xiaoqiu Xu 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.3
In view of the problem of data heterogeneity in enterprise application integration, we proposed a solution, which is based on XML, WSDL and Web Service technology to achieve the elimination of data heterogeneity, which can reduce the complexity of the system, and has certain significance for the information communication between enterprises and enterprises.
Qiuliang Cai,Lei Tong,Jingjing Zhang,Jie Zheng,Mengmeng He,Jiamei Lin,Xiaoqiu Chen,Hang Xiao 대한환경공학회 2019 Environmental Engineering Research Vol.24 No.4
Air pollution has attracted ever-increasing attention because of its substantial influence on air quality and human health. To better understand the characteristics of long-range transported pollution, the single particle chemical composition and size were investigated by the single particle aerosol mass spectrometry in Fuzhou, China from 17th to 22nd January, 2016. The results showed that the haze was mainly caused by the transport of cold air mass under higher wind speed (10 m·s<SUP>-1</SUP>) from the Yangtze River Delta region to Fuzhou. The number concentration elevated from 1,000 to 4,500 #·h<SUP>-1</SUP>, and the composition of mobile source and secondary aerosol increased from 24.3% to 30.9% and from 16.0% to 22.5%, respectively. Then, the haze was eliminated by the clean air mass from the sea as indicated by a sharp decrease of particle number concentration from 4,500 to 1,000 #·h<SUP>-1</SUP>. The composition of secondary aerosol and mobile sources decreased from 29.3% to 23.5% and from 30.9% to 23.1%, respectively. The particles with the size ranging from 0.5 to 1.5 ㎛ were mainly in the accumulation mode. The stationary source, mobile source, and secondary aerosol contributed to over 70% of the potential sources. These results will help to understand the physical and chemical characteristics of long- range transported pollutants.