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Now showing items 33 - 44 of 44

  • Urban extent enhances extreme precipitation over the Pearl River Delta,China

    Wang, Dagang   Jiang, Peng   Wang, Guiling   Wang, Dashan  

    The relationship between urban extent and extreme precipitation over the Pearl River Delta in China is evaluated using the Tropical Rainfall Measurement Mission 3B42 precipitation product. The spatial pattern of extreme precipitation indices agrees well with that of the urban extent, with significant and positive spatial correlation between the two. The correlation is stronger for extreme indices at shorter temporal scales than for those at longer temporal scales. For example, the coefficient of correlation with the natural logarithm of urban extent is 0.42 for the maximum consecutive 5-day precipitation amount and reaches 0.74 for the maximum consecutive 3-h precipitation amount.
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  • Identification and fine-mapping of a genetic locus underlying soybean tolerance to SMV infections

    Lin, Jing   Lan, Zejun   Hou, Wenhuan   Yang, Chunyan   Wang, Dagang   Zhang, Mengchen   Zhi, Haijian  

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  • Crack initiation characteristics of ring chain of heavy-duty scraper conveyor under time-varying loads

    Wang, Dagang   Zhang, Jun   Zhu, Zhencai   Gang, Shen   Xiang, Li  

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  • Fine mapping of the R-SC8 locus and expression analysis of candidate SMV resistance genes in soybean

    Zhao, Lin   Wang, Dagang   Zhang, Hongyun   Shen, Yingchao   Yang, Yongqing   Li, Kai   Wang, Liqun   Yang, Yunhua   Zhi, Haijian  

    Soybean mosaic disease, caused by soybean mosaic virus (SMV), is one of the most broadly distributed viral diseases of soybean (Glycine max [L.] Merr.) worldwide, which decreases seed quality and causes serious losses in yields. The accession Kefeng No.1' was previously shown to carry the R-SC8 gene on chromosome 2, which confers resistance to SMV strain SC8. To fine map the R-SC8 gene, we generated larger F-2 population (2122 plants) from the cross between resistant accession Kefeng No.1' and susceptible variety Nannong 1138-2'. Using eight genomic-SSR markers including four newly developed markers, we mapped this gene to a 30.8-kb region containing two annotated genes between two markers, ZL-42 and ZL-52, on chromosome 2. The expression of genes Glyma.02G121500 and Glyma.02G121600 (encoding MADS-box proteins) was higher in Kefeng No.1' plants than that in Nannong 1138-2' plants, as determined by quantitative reverse transcription-polymerase chain reaction (QRT-PCR). These results suggest that the two genes are likely involved in conferring SMV resistance. This study willfacilitate marker-assisted selection of this gene for use in soybean breeding programmes.
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  • Charge transfer complex-doped single-walled carbon nanotubes with reduced correlations between electrical conductivity and Seebeck coefficient for flexible thermoelectric generators

    Tan, Jingjuan   Huang, Hongfeng   Wang, Dagang   Qin, Shihui   Xiao, Xu   Chen, Zhanhua   Liu, Danqing   Wang, Lei  

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  • Thermoelectric properties of Polythiophene/MWNT composites prepared by ball-milling

    Wang, Dagang   Wang, Lei   Wang, Wenxin   Bai, Xiaojun   Li, Junqin  

    Polythiophene /multi-wall carbon nanotubes (MWNT) composites were prepared by ball-mailing. The morphology and internal structure of the composites were evaluated by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD). Their thermoelectric properties, i.e., the electrical conductivity, the Seebeck coefficient and the thermal conductivity, were investigated in detail. The results showed that the MWNT were uniformly dispersed in the polymer matrix, and that increasing the electrical conductivity is the key factor for enhancing the thermoelectric figure of merit at MWNT content below 70 wt%; with MWNT content beyond 70 wt%, the decrease of Seebeck coefficient and the increase of thermal conductivity led to the decrease of the thermoelectric figure of merit of the composites. The highest ZT is 2.43x10(-4) for the 70 wt% MWNT. This study suggests a simple way to improve the thermoelectric performances of conducting polymers.
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  • Evaluation of CMPA precipitation estimate in the evolution of typhoon-related storm rainfall in Guangdong,China

    Wang, Dashan   Wang, Xianwei   Liu, Lin   Wang, Dagang   Huang, Huabing   Pan, Cuilin  

    The merged precipitation data of Climate Prediction Center Morphing Technique and gauge observations (CMPA) generated for continental China has relatively high spatial and temporal resolution (hourly and 0.1 W), while few studies have applied it to investigate the typhoon-related extreme rainfall. This study evaluates the CMPA estimate in quantifying the typhoon-related extreme rainfall using a dense rain gauge network in Guangdong Province, China. The results show that the event-total precipitation from CMPA is generally in agreement with gauges by relative bias (RB) of 2.62, 10.74 and 0.63% and correlation coefficients (CCs) of 0.76, 0.86 and 0.91 for typhoon Utor, Usagi and Linfa events, respectively. At the hourly scale, CMPA underestimates the occurrence of light rain (< 1 mm/h) and heavy rain (> 16 mm/h), while overestimates the occurrence of moderate rain. CMPA shows high probability of detection (POD =3D 0.93), relatively large false alarm ratio (FAR 0.22) and small missing ratio (0.07). CMPA captures the spatial patterns of typhoon-related rain depth, and is in agreement with the spatiotemporal evolution of hourly gauge observations by CC from 0.93 to 0.99. In addition, cautiousness should be taken when applying it in hydrologic modeling for flooding forecasting since CMPA underestimates heavy rain (> 16 mm/h).
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  • Use of high-resolution precipitation observations in quantifying the effect of urban extent on precipitation characteristics for different climate conditions over the Pearl River Delta,China

    Wang, Dashan   Wang, Dagang   Qi, Xiangyan   Liu, Lin   Wang, Xianwei  

    Few studies conduct a quantitative assessment between the urban extent and local precipitation characteristics. In this paper, high-resolution precipitation data and urban extent data are used to investigate the correlation between precipitation frequency, intensity and extremes and urban extent under different climate conditions over the Pearl River Delta, China. Analysis reveals that extreme precipitation amount (R =3D 0.45 for 1-hr maximum) and mean intensity (R =3D 0.56) are positively correlated with urban extent and that wet hours (R =3D -0.58) are negatively correlated with urban extent. The correlation coefficients between urban extent and extreme indices increase with the decrease in temporal scale of indices. The high coefficients of precipitation intensity and urban extent are mainly attributed to the precipitation under the tropical convection, and the negative coefficient of total wet hours is dominated by precipitation frequency under the Southwest monsoon. By contrast, the precipitation characteristics are less correlated with urban extent during typhoon events. Urban environments probably play a positive role in generating the short-duration heavy precipitation through enhancing deep convections induced by higher surface temperature and higher aerosol concentration.
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  • Dynamic contact characteristics between hoisting rope and friction lining in the deep coal mine

    Wang, Dagang   Wang, Dao\"ai  

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  • Effect of broken wire on bending fatigue characteristics of wire ropes

    Zhang, Dekun   Feng, Cunao   Chen, Kai   Wang, Dagang   Ni, Xiang  

    The life of damaged wire rope is difficult to judge and the damaged wire rope is prematurely replaced resulting in an enormous economic waste. This paper studies the effect of different distributions of pre-broken wires on bending fatigue behavior of wire ropes using a self-made bending fatigue test facility. The fatigue lives of wire ropes with different distributions of pre-broken wires were studied using both visual inspection and commercial non-destructive inspection technology, combined with electron microscopy. It is found that broken wires on the surface reduce the bending fatigue life of wire ropes. The broken wires increase the stress in the inner wire strands as well as the contact force between the wires. This leads to a concentration of severe wear, which accelerates the density of broken wires locally, leading to short fatigue lives especially in the case with the most concentrated number of pre-broken wires (1 x 4). After numerous wires fail by wear and fatigue, others fail by tensile overload, as evidenced microscopically by necking and ductile failure. The damage in the rope at failure defined by counting broken Wires is nearly 50% smaller than the damage value given by the commercial non-destructive damage value, based on magnetic measurements. (C) 2017 Elsevier Ltd. All, rights reserved.
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  • Fretting-fatigue behavior of steel wires in low cycle fatigue

    Wang, Dagang   Zhang, Dekun   Ge, Shirong  

    The effect of strain amplitude on fretting-fatigue behavior of steel wires in low cycle fatigue was investigated using a fretting-fatigue test rig which was capable of applying a constant normal contact load. The fretting regime was identified based on the shape of the hysteresis loop of tangential force versus displacement amplitude. The variations of the normalized tangential force with increasing cycle numbers and fretting-fatigue lives at different strain amplitudes were explored. The morphologies of fretting contact scars after fretting-fatigue tests were observed by scanning electron microscopy and optical microscopy to examine the failure mechanisms of steel wires. The acoustic emission technique was used to characterize the fretting-fatigue damage in the fretting-fatigue test. The results show that the fretting regimes are all located in mixed fretting regimes at different strain amplitudes. The increase in strain amplitude increases the normalized tangential force and decreases the fretting fatigue life. The abrasive wear, adhesive wear and fatigue wear are main wear mechanisms for all fretting-fatigue tests at different strain amplitudes. The accumulative total acoustic emission events during fretting-fatigue until fracture of the tensile steel wire decrease with increasing strain amplitude. An increase of the strain amplitude results in the accelerated crack nucleation and propagation and thereby the decreased life. (C) 2011 Elsevier Ltd. All rights reserved.
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  • Impact of sub-grid variability of precipitation and canopy water storage on hydrological processes in a coupled land-atmosphere model

    Wang, Dagang   Wang, Guiling   Anagnostou, Emmanouil N.  

    The impact of sub-grid variability of precipitation and canopy water storage is investigated by applying a new canopy interception scheme into the Community Atmosphere Model version 3 (CAM3) coupled with the Community Land Model version 3 (CLM3). Including such sub-grid variability alters the partitioning of net radiation between sensible heat flux and latent heat flux on land surface, which leads to changes in precipitation through various pathways/mechanisms. The areas with most substantial changes are Amazonia and Central Africa where convective rain is dominant and vegetation is very dense. In these areas, precipitation during December-January-February is increased by up to 2 mm/day. This increase is due to the enhanced large-scale circulation and atmospheric instability caused by including the sub-grid variability. Cloud feedback plays an important role in modifying the large-scale circulation and atmospheric instability. Turning off cloud feedback mitigates the changes in surface convergence and boundary layer height caused by inclusion of sub-grid variability of precipitation and water storage canopy, which moderate the effect on precipitation.
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