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87篇 您的检索式:作者名="Weicheng Liu"
    题名 作者 年代 出处 被引量
1China’s first deep manned submersible,JIAOLONG显示文摘A deep manned submersible is indispensable to deep ocean exploration. No other equipment can bring scientists to ex-treme sea floor depths to do research in situ. Marine geology, seafloor geophysics,marine biology,and oceanic chemistry are the fields that scientists are particularly eager to study [1-6]. Chinese scientists have long dreamed of using their own submersible to probe the deep sea. China’s recent fast development of a deep manned submersible has realized that dream.Liu, Feng Cui, WeiCheng Li, XiangYang 2010Science China Earth Sciences2010,53,10:24
2A 3D bounding surface model for rockfill materials显示文摘A 3D bounding surface model is established for rockfill materials,which can be applied to appropriately predict the deformation and the stabilization of rockfill dams.Firstly,an associated plastic flow rule for rockfill materials is investigated based on the elaborate data from the large-style triaxial compression tests and the true triaxial tests.Secondly,the constitutive equations of the 3D bounding surface model are established by several steps.These steps include the bounding surface incorporating the general nonlinear strength criterion,stress-dilatancy equations,the evolution of the bounding surface and the bounding surface plasticity.Finally,the 3D bounding surface model is used to predict the mechanical behaviors of rockfill materials from the large-style triaxial compression tests and the true triaxial tests.Consequently,the proposed 3D bounding surface model can well capture such behaviors of rockfill materials as the strain hardening,the post-peak strain softening,and the volumetric strain contraction and expansion in both two-and three-dimensional stress spaces.XIAO Yang LIU HanLong ZHU JunGao SHI WeiCheng LIU MengCheng 2011Science China(Technological Sciences)2011,54,11:16
3Progress in research and application of water mist fire suppression technology显示文摘Water mist technology in fire suppression has been a subject of many investigations over the last decade. This paper introduces the concept of water mist technology and discusses its extinguishment mechanisms in comparison with other fire suppression systems briefly. A survey is made on the recent applications of water mist for (1) Class B spray and pool fires in machinery spaces, gas turbine enclosures, combat vehicles, and flammable liquid storage rooms; (2) Class A fires in residential occupancies, marine accommoda-tions and public spaces, heritage buildings and libraries; (3) Class C fires in electronic equipment and computer rooms; and (4) the fires in aircraft onboard cabin and cargo com-partments. The paper proceeds to review some new applica-tions of water mist for the Class K fires in commercial cook rooms. Use of water mist for total-ship protection as well as the fire protection of heavy goods vehicle shuttle trains is also investigated. At last, the up-to-date development of corresponding test to evaluate the capabilities and limitaions of water mist is discussed.LIU Jianghong, LIAO Guangxuan, LI Peide, FAN Weicheng & LU Qiang State Key Laboratory of fire Science, University of Science and Tech-nology of China, Hefei 230026, China Correspondence should be addressed to Liu Jianghong (e-mail: ljh@ ustc.edu.cn) 2003Chinese Science Bulletin2003,48,8:15
4Responses of root growth of Alhagi sparsifolia Shap. (Fabaceae) to different simulated groundwater depths in the southern fringe of the Taklimakan Desert, China显示文摘Alhagi sparsifolia Shap. (Fabaceae) is a spiny, perennial herb. The species grows in the salinized, arid regions in North China. This study investigated the response characteristics of the root growth and the distribution of one-year-old A. sparsifolia seedlings to different groundwater depths in controlled plots. The ecological adaptability of the root systems of A. sparsifolia seedlings was examined using the artificial digging method. Results showed that: (1) A. sparsifolia seedlings adapted to an increase in groundwater depth mainly through increasing the penetration depth and growth rate of vertical roots. The vertical roots grew rapidly when soil moisture content reached 3%-9%, but slowly when soil moisture content was 13%-20%. The vertical roots stopped growing when soil moisture content reached 30% (the critical soil moisture point). (2) The morphological plasticity of roots is an important strategy used by A. sparsifolia seedlings to obtain water and adapt to dry soil conditions. When the groundwater table was shallow, horizontal roots quickly expanded and tillering increased in order to compete for light resources, whereas when the groundwater table was deeper, vertical roots developed quickly to exploit space in the deeper soil layers. (3) The decrease in groundwater depth was probably responsible for the root distribution in the shallow soil layers. Root biomass and surface area both decreased with soil depth. One strategy of A. sparsifolia seedlings in dealing with the increase in groundwater depth is to increase root biomass in the deep soil layers. The relationship between the root growth/distribution of A. sparsifolia and the depth of groundwater table can be used as guidance for harvesting A. sparsifolia biomass and managing water resources for forage grasses. It is also of ecological significance as it reveals how desert plants adapt to arid environments.FanJiang ZENG Cong SONG HaiFeng GUO Bo LIU WeiCheng LUO DongWei GUI Stefan ARNDT DaLi GUO 2013Journal of Arid Land2013,5,2:13
5S phase-dependent interaction with DNMT1 dictates the role of UHRF1 but not UHRF2 in DNA methylation maintenance显示文摘最近的研究证明 UHRF1 被指向 DNMT1 到 DNA 复制 foci 为 DNA methylation 维护要求,大概通过它的唯一的半甲醇化物有 DNMT1 的 DNA 有约束力的活动和相互作用。UHRF2, UHRF 家庭蛋白质的另一个成员,高度类似于在顺序和结构的 UHRF1,关于它在 DNA methylation 的角色的涨的问题。在这研究,我们证明 UHRF2 象 UHRF1 一样,也优先地绑在 methylated histone H3 离氨酸 9 (H3K9 ) 通过它的保存 tudor,通过 SET 和戒指的领域和半甲醇化物 DNA 联系了领域。象 UHRF1 一样, UHRF2 在 pericentric heterochromatin 被充实。heterochromatin 本地化取决于到大程度它的 methylated H3K9 有约束力的活动并且到它的 methylated 上的更少的程度 DNA 有约束力的活动。Coimmunoprecipitation 实验证明 UHRF1 和 UHRF2 与 DNMT1, DNMT3a, DNMT3b 和 G9a 交往。尽管有所有这些保存功能,我们发现 UHRF2 不能在 Uhrf1 空老鼠救 DNA methylation 缺点胚胎的干细胞。这个罐头在房间周期的 S 阶段期间为 UHRF2 被归因于无能到成员 DNMT1 到复制 foci。确实,我们发现当 UHRF1 在房间以一种 S 阶段依赖者方式与 DNMT1 交往时, UHRF2 不做。因此,我们的学习证明 UHRF2 和 UHRF1 不在 DNA methylation 维护是机能上地冗余的并且作为为 DNA methylation 指向 DNMT1 的关键规章的机制揭示在 UHRF1 和 DNMT1 之间的 cell-cycle-dependent 相互作用。Jiqin Zhang Qinqin Gao Pishun Li Xiaoli Liu Yuanhui Jia Weicheng Wu Jiwen Li Shuo Dong Haruhiko Koseki Jiemin Wong 2011Cell Research2011,21,12:12
6Cold acclimation improves photosynthesis by regulating the ascorbate–glutathione cycle in chloroplasts of Kandelia obovata显示文摘As the most northerly mangrove species in China, Kandelia obovata may undergo extreme cold event stress. Enhancing the cold tolerance of this species is crucial to its successful afforestation. This study aimed to determine the resistance of K. obovata seedlings to low temperature stress by cold acclimation and to explain the mechanisms for alleviating cold injury. To understand these mechanisms, seedlings that were acclimatized and not acclimatized were exposed to 5℃/- 2℃(day/night)for 48 h.Results showed that low temperature stress reduced leaf photosynthesis of non-acclimatized seedlings by inducing oxidative stress and structural damage to chloroplasts. These phenomena were shown by increasing levels of malondialdehyde (MDA), O2-and H2O2, as well as decreasing enzyme activities in the ascorbate–glutathione (AsA-GSH) cycle. However, cold-acclimatized seedlings had improved photosynthetic rates and efficiency of photosystem II (PSII) under low temperature stress. Compared with non-acclimatized seedlings, leaves of coldacclimatized seedlings under low temperature stress for 48 h exhibited higher anti-oxidative enzyme activities, lower levels of O2^- and H2O2, less damage to chloroplast structure, and removed 33.7% of MDA at low temperature stress for 48 h. The data indicate that cold acclimation enhances photosynthetic capacity by effectively regulating activation in the PSII electron transport and the AsA–GSH cycle to scavenge excess ROS in chloroplasts, while the latter is more important.Weicheng Liu Chunfang Zheng Jinong Chen Jianbiao Qiu Zhixing Huang Qi Wang Yong Ye 2019Journal of Forestry Research2019,30,3:11
7Precipitation seesaw phenomenon and its formation mechanism in the eastern and western parts of Northwest China during the flood season显示文摘Extending across three major plateaus,namely the Qinghai-Tibetan Plateau,the Inner Mongolia-Xinjiang Plateau and the Loess Plateau,Northwest China has the complex terrain and spatio-temporal climate variations,and is affected by the interactions among different circulation systems,such as the summer monsoon,the westerlies and the plateau monsoon.The understanding of the climate variability,as well as its characteristics and evolution mechanisms in this area has been limited so far.In this paper,the precipitation characteristics and mechanisms in the eastern and western parts of Northwest China during the flood season are compared and analyzed based on the data from 192 national meteorological observational sites in Northwest China in 1961-2016.The results show that,divided by the northern boundary of the East Asian summer monsoon,there are huge differences in the precipitation variation characteristics between the eastern and western parts.The inter-annual variations,interdecadal variations and total trends in the two parts all show a significant seesaw phenomenon.Moreover,it is found that the seesaw phenomenon of precipitation variation is closely related to the opposite variation between the East Asian summer monsoon index(MI)and the westerly circulation index(WI).In addition,the inverse variations on different time scales are only related to the contributions of precipitation at specific grades.Besides,in the two matching patterns of precipitation in the seesaw phenomenon,the middle and high latitudes are occupied by the'high-low-high'wave trains in the precipitation increases in the east of Northwest China(ENWC)and decreases in the west of Northwest China(WNWC)pattern,meaning precipitation increases in ENWC and decreases in WNWC.Whereas the opposite'low-high-low'wave trains at 500 hPa height are observed in the middle and high latitudes in the WH-EA pattern at 500 hPa height,meaning precipitation increases in WNWC and decreases in ENWC.Thus,the atmosphere circulation situation with two wave train types can support both the precipitation seesaw phenomenon and the opposite variation between MI and WI.Moreover,the seesaw phenomenon is shown to be related to the separate or joint effects of the South Asian High,ENSO and the plateau heating on the common but opposite effect on the summer monsoon and the westerlies,in which the South Asian High probably plays a more critical role.This study could deepen the scientific understanding of precipitation mechanisms and improve the weather forecast technology in Northwest China during the flood season.Qiang ZHANG Jingjing LIN Weicheng LIU Lanying HAN 2019Science China Earth Sciences2019,62,12:11
8Modeling and behaviours of rockfill materials in three-dimensional stress space显示文摘A bounding surface model incorporating a unified nonlinear strength criterion is proposed.The proposed bounding surface model contains 9 model parameters,which can be determined from the conventional triaxial tests.The bounding surface model can reproduce such behaviours as the strain hardening,the post-peak strain softening,and the volumetric strain contraction and expansion.Based on the comparisons between the predictions and the test results,the proposed strength criterion and model can well reproduce the experimental results of the strength and stress-strain behaviours of rockfill material in three-dimensional stress space.The strength behaviour of rockfill material is summarized as:(a) the failure stress ratio decreases with the initial confining pressure on the meridian plane;(b) the failure deviatoric stress decreases with the Lode angle from 0o to 60o on the deviatoric plane.The stress ratio decreases with increasing one of such factors as the initial void ratio,the intermediate principal stress ratio and the minor principal stress at the same strain when the other factors are given.XIAO Yang LIU HanLong ZHU JunGao SHI WeiCheng 2012Science China(Technological Sciences)2012,55,10:10
9Dilatancy equation of rockfill material under the true triaxial stress condition显示文摘Rockfill material is widely used for construction of high rockfill dam due to its facility,economical cost,high strength and effective aseismatic property.It is provoked profoundly to propose a suitable constitutive model for a better application of this material.The dilatancy equation of rockfill material plays a significant role in the constitutive model.For the sake of simplicity,a dilatancy equation is established by the linear least square method on the basis of the rearranged data of rockfill material in the true triaxial tests.Based on the fact that the rearranged data at different initial confining pressures are aligned in a narrow band,the dilatancy behavior of rockfill material is independent of the initial confining pressure.However,different from the initial confining pressure,both the intermediate principal stress ratio and the specimen density exhibit a remarkable influence on the dilatancy behaviors of rockfill material.Furthermore,the predictions of the proposed dilatancy equation are in a good agreement with the rearranged test data of rockfill material at different specimen densities and stress paths.XIAO Yang 1,2,LIU HanLong 1,2,ZHU JunGao 1,2 & SHI WeiCheng 1,3 1 Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,Hohai University,Nanjing 210098,China 2 Geotechnical Research Institute,Hohai University,Nanjing 210098,China 3 School of Civil Engineering and Architecture,Changzhou Institute of Technology,Changzhou 213002,China 2011Science China(Technological Sciences)2011,54,S1:9
10Mechanisms on inhibition of photosynthesis in Kandelia obovata due to extreme cold events under climate change显示文摘Introduction:Mangroves that grow at the latitudinal extremes of their distribution are susceptible to extreme cold events.Successive enhancement of low temperature stress(seLTS)is a typical characteristic of extreme cold events.Low temperature stress can inhibit mangrove photosynthesis,which often inhibits the growth and development of mangroves.However,the possible reasons for impairment to photosynthesis of mangroves due to extreme cold events remain unclear.Methods:Kandelia obovata seedlings in a growth chamber were exposed to 5℃/−2℃(day/night)for 36 h(−2℃ for 16 h)with 12 h light per day at 600μmol m^(−2) s^(−1) photosynthetic photon flux density(PPFD)(a low temperature stress,aLTS),then the plants were transferred to the control condition(15℃/10℃(day/night)and allowed to recover for 5 days(R1).The other seedlings were subjected to low temperature treatment with a day/night temperature of 5℃/−1℃ in a growth chamber for 24 h.Then these plants were transferred to 5℃/−2℃(day/night)under the same light and climate conditions for 36 h(two low temperature stresses,tLTS).Following the successive enhancement of low temperature treatment,these plants were returned to 15℃/10℃(day/night)for another 5-day recovery period(R2).Results:Results showed that aLTS treatment significantly reduced leaf net photosynthetic rate(P_(n))and stomatal conductance(G_(s)),while increased intercellular CO_(2) concentration(C_(i)).Photosynthetic activity of leaves quickly recovered after the plants were returned to control temperature for 5 days(R1).However,decreases in leaf Pn were more obvious under tLTS treatment than those under aLTS treatment.This reduced Pn might be attributed to stomatal and non-stomatal limitations.Moreover,non-stomatal limitation played a major role in reducing Pn during tLTS treatment,as proven by reduced ribulose 1,5-biphosphate carboxylase(RuBPCase)activity.This limitation also enhanced lipid peroxidation in chloroplasts,decreased sucrosemetabolizing enzymes and ratios of both chlorophyll a/chlorophyll b(Chl a/b)and chlorophyll/carotenoids(Chl/Car),and increased protease senescence.Damages of tLTS treatment to photosynthesis were insufficiently alleviated even after the plants were returned to control temperature for 5 days(R2).Conclusions:Successive enhancement of low temperature depressed successful recovery of leaf photosynthesis of K.obovata seedlings mainly by impairing pigment synthesis,antioxidant metabolism,and sucrose translocation,as well as accelerating senescence of endopeptidase.Furthermore,our results suggest that decreases in sucrose content in leaves might also account for increases in reactive oxygen species(ROS)in chloroplasts.Chunfang Zheng Jianwu Tang Jinong Chen Weicheng Liu Jianbiao Qiu Xin Peng Yong Ye 2016Ecological Processes2016,5,1:6
11New mass loss kinetic model for thermal decomposition of biomass显示文摘Based on non-isothermal experimental results for eight Chinese biomass species, a new kinetic model, named as the 損seudo bi-component separate-stage model (PBSM)? is developed in this note to describe the mass loss behavior of biomass thermal decomposition. This model gains an advantage over the commonly used 損seudo single-component overall model (PSOM)?and 損seudo multi-component overall model (PMOM)? By means of integral analysis it is indicated that the new model is suitable to describe the mass loss kinetics of wood and leaf samples under relatively low heating rates (e.g. 10℃/min, used in this work).LIU Naian FAN Weicheng R.Dobashi LIN Qizhao 2001Chinese Science Bulletin2001,46,16:6
12Mechanism of the Rpn13-induced activation of Uch37显示文摘Lianying Jiao Songying Ouyang Neil Shaw Gaojie Song Yingang Feng Fengfeng Niu Weicheng Qiu Hongtao Zhu Li-Wei Hung Xiaobing Zuo V. Eleonora Shtykova Ping Zhu Yu-Hui Dong Ruxiang Xu Zhi-Jie Liu 2014Protein & Cell2014,5,8:4
13Recovery of photosynthesis,sucrose metabolism,and proteolytic enzymes in Kandelia obovata from rare cold events in the northernmost mangrove,China显示文摘Introduction:Understanding how mangroves respond to rare cold events has implications for both restoration and conservation under climate change scenarios.This study investigated the responses of photosynthesis and activities of key enzymes involving carbon and nitrogen metabolism at different ages of Kandelia obovata to a rare cold event in the winter of 2010.Methods:This study took place on Ximen Island,Zhejiang Province,China.We measured the physiological recovery of 2-3-,5-6-,9-10-and 54-55-year-old K.obovata trees after freezing injury in February and March in 2011 and 2012,respectively.Results:Chilling injury index and electrolyte leakage of K.obovata increased with increasing tree age in the winter of 2010,and electrolyte leakage in K.obovata at different ages in the winter of 2010 was far higher than that in the winter of 2011.The rare cold events significantly changed the recoveries of the leaf net photosynthetic rate(Pn)and stomatal conductance(Gs);ratios of chlorophyll a/chlorophyll b(Chl a/Chl b);contents of total soluble sugar(TSS),sucrose,free amino acid(FAA),and soluble protein;and activities of sucrose phosphate synthase(SPS),endopeptidase,and carboxypeptidase in K.obovata at different ages.These effects were mainly due to changes in the physiological mechanism in the 2-year-old trees.A clear decrease in Pn of the 2-year-old trees was observed in February 2011,as exemplified by reductions in ratios of Chl a/Chl b and chlorophyll/carotenoid(Chl/Car),as well as inhibition of the levels of TSS and FAA(osmotic substances).During recovery in 2011 and 2012,the activities of SPS and sucrose synthase(SS)were responsible for sucrose synthesis after the rare cold events in 2011,but only SPS activity was one of the main factors contributing to the metabolism of stachyose to sucrose without cold damage in 2012.Carboxypeptidase played a more important role than endopeptidase during protein hydrolysis after the rare cold events.Conclusions:The results suggest that the recovery of photosynthetic capacity in K.obovata was changed after a rare cold event,which is associated with pigment components and activities of SS,SPS,and carboxypeptidase,especially the seedlings.Chunfang Zheng Yong Ye Weicheng Liu Jianwu Tang Chengnian Zhang Jianbiao Qiu Jinong Chen 2016Ecological Processes2016,5,1:4
14Photonic cavity enhanced high-performance surface plasmon resonance biosensor显示文摘Herein we propose a novel strategy to enhance surface plasmon resonance(SPR)by introducing a photonic cavity into a total-internal-reflection architecture.The photonic cavity,which is comprised of a highly reflective photonic crystal(PC),defect layers,and a gold(Au)film,enables Fabry–Perot(FP)resonances in the defect layers and therefore narrows the SPR resonance width in the metallic surface as well as increases the electric field intensity and penetration depth in the evanescent region.The fabricated sensor exhibits a 5.7-fold increase in the figure of merit and a higher linear coefficient as compared with the conventional Au-SPR sensor.The demonstrated PC/FP cavity/metal structure presents a new design philosophy for SPR performance enhancement.GUI-SHI LIU XIN XIONG SHIQI HU WEICHENG SHI YAOFEI CHEN WENGUO ZHU HUADAN ZHENG JIANHUI YU NUR HIDAYAH AZEMAN YUNHAN LUO ZHE CHEN 2020Photonics Research2020,8,4:4
15Improving the performance of solid oxide electrolysis cell with gold nanoparticles-modified LSM-YSZ anode显示文摘Gold, as the common current collector in solid oxide electrolysis cell(SOEC), is traditionally considered to be inert for oxygen evolution reaction at the anode of SOEC. Herein, gold nanoparticles were loaded onto conventional strontium doped lanthanum manganite-yttria stabilized zirconia(LSM-YSZ) anode, which evidently improved the performance of oxygen evolution reaction at 800 °C. The current densities at 1.2 V and 1.4 V increased by 60.0% and 46.9%, respectively, after loading gold nanoparticles onto the LSM-YSZ anode. Physicochemical characterizations and electrochemical measurements suggested that the improved SOEC performance was attributed to the accelerated electron transfer of elementary process in anodic polarization reaction and the newly generated triple phase boundaries in gold nanoparticles-loaded LSMYSZ anode.Yuefeng Song Xiaomin Zhang Yingjie Zhou Houfu Lv Qingxue Liu Weicheng Feng Guoxiong Wang Xinhe Bao 2019Journal of Energy Chemistry2019,28,8:4
16Effect of ultrasonic micro-forging treatment on microstructure and mechanical properties of GH3039 superalloy processed by directed energy deposition显示文摘In this work,ultrasonic micro-forging treatment(UMFT)was introduced to achieve homogeneous microstructure,reduce defects and improve mechanical properties of GH3039 superalloy cladding layer processed by directed energy deposition(DED).The microstructure,defects and mechanical properties of the cladding layers treated by UMFT with different ultrasonic powers(UIPs)were investigated.Results revealed a gradient structure as equiaxed grains distributed at the top,a columnar-to-equiaxed transition(CET)region that mixed of columnar dendrites and equiaxed grains distributed at the middle and columnar dendrites at the bottom of the cladding layer was formed.After UMFT,the proportion of equiaxed grains was increased,the average size of equiaxed grains was refined to 10μm from 16μm,the orientation of grains was more uniform and the phases enriched of Al,Ti,C,Nb and Mo were precipitated.The grain refinement can be attributed to the fracture of columnar dendrites induced by the ultrasonic vibration during solidification.Besides,the porosity of the cladding layer was reduced after UMFT.The microhardness of the cladding layers exhibited a depth-dependent gradient at the top region.The microhardness of the top surface was the highest and showed an increasing trend with the increase of UIP.The microhardness of different grain morphologies exhibited no substantial difference.However,due to grain refinement and precipitation of strengthening phase induced by UMFT,the microhadness of some local locations were improved.These results indicated UMFT has a significant effect on improving the microstructure,defects and mechanical properties of the deposited cladding layer.Qingqing Li Yong Zhang Jie Chen Bugao Guo Weicheng Wang Yuhai Jing Yong Liu 2021Journal of Materials Science & Technology2021,,11:4
17Fusaricidins in Paenibacillus polymyxa A21 and their antagonistic activity against Botrytis cinerea on tomato显示文摘Four kinds of antifungal compounds from an extract of Paenibacillus polymyxa A21 with molecular masses of 883.56, 897.59, 947.55, and 961.58 Da were characterized as the members of fusaricidin-type of antibiotics according to LC-MS analysis. Fusaricidins isolated from culture filtrate displayed high antagonistic activity against several plant fungal pathogens, especially Botrytis cinerea, the causal agent of gray mold. The fusaricidins biosynthetic gene cluster(BGC) from A21 was cloned by PCR and comparative cluster analysis revealed that gene fus TE, the 3′ boundary of the fusaricidin BGC in strain PKB1, was not present in fusaricidin BGC of A21, indicating that fus TE is not necessary for fusaricidin synthesis. Fusaricidin extract from A21 significantly reduced gray mold disease incidence and severity on tomato. The m RNA levels for three pathogenesis-related proteins(PRs) revealed that treatment of tomato leaves with fusaricidin extract induced the expression of PR genes to different levels, suggesting that one reason for the reduction of gray mold infection by fusaricidin is induction of PR proteins, which lead to increased resistance to pathogens. This is the first report of the application of fusaricidins to control tomato gray mold and the comparative cluster analysis provides important molecular basis for research on fusaricidin biosynthesis.Weicheng LIU Xiaoli WU Xuelian BAI Hong ZHANG Dan DONG Taotao ZHANG Huiling WU 2018Frontiers of Agricultural Science and Engineering2018,5,2:4
18Statistics of the Z–R Relationship for Strong Convective Weather over the Yangtze–Huaihe River Basin and Its Application to Radar Reflectivity Data Assimilation for a Heavy Rain Event显示文摘The relationship between the radar reflectivity factor(Z) and the rainfall rate(R) is recalculated based on radar observations from 10 Doppler radars and hourly rainfall measurements at 6529 automatic weather stations over the Yangtze–Huaihe River basin. The data were collected by the National 973 Project from June to July 2013 for severe convective weather events. The Z–R relationship is combined with an empirical qr–R relationship to obtain a new Z–qr relationship, which is then used to correct the observational operator for radar reflectivity in the three-dimensional variational(3 DVar) data assimilation system of the Weather Research and Forecasting(WRF) model to improve the analysis and prediction of severe convective weather over the Yangtze–Huaihe River basin. The performance of the corrected reflectivity operator used in the WRF 3 DVar data assimilation system is tested with a heavy rain event that occurred over Jiangsu and Anhui provinces and the surrounding regions on 23 June 2013. It is noted that the observations for this event are not included in the calculation of the Z–R relationship. Three experiments are conducted with the WRF model and its 3 DVar system, including a control run without the assimilation of reflectivity data and two assimilation experiments with the original and corrected reflectivity operators. The experimental results show that the assimilation of radar reflectivity data has a positive impact on the rainfall forecast within a few hours with either the original or corrected reflectivity operators, but the corrected reflectivity operator achieves a better performance on the rainfall forecast than the original operator. The corrected reflectivity operator extends the effective time of radar data assimilation for the prediction of strong reflectivity. The physical variables analyzed with the corrected reflectivity operator present more reasonable mesoscale structures than those obtained with the original reflectivity operator. This suggests that the new statistical Z–R relationship is more suitable for predicting severe convective weather over the Yangtze–Huaihe River basin than the Z–R relationships currently in use.Xue FANG Aimei SHAO Xinjian YUE Weicheng LIU 2018Journal of Meteorological Research2018,32,4:3
19A Thermodynamic Analysis on the Catalytic Combustion of Methane显示文摘Chemical equilibria involving 10 species and adiabatic reaction temperature of methane combustion in air under various conditions have been calculated in detail by means of total Gibbs energy minimization of the system. The calculation data show that the adiabatic combustion temperature of CH4 and air at stoichiometric ratio is up to about 2200 K, and the equilibrium concentration of NO is about 0.0018, however that of NO2 is only 1 × 10-6. A large amount of carbon deposition emerges when the CH4 concentration is above 26.5%. The NO and NO2 appear only when the CH4 concentration is below 16%.The maximum equilibrium concentrations of NO and NO2 are 0.0028 and 2× 10-6 respectively, at about 8%CH4 concentration. The NO and NO2 concentrations increase with the system temperature at a low CH4 concentration. However, both of them can be decreased when CO2 or steam is introduced into the system, which also decreases the adiabatic combustion temperature. The decrease in adiabatic temperature caused by CO2 addition is more appreciable than that caused by the addition of H2O. Pressure does not have a notable effect on the system equilibrium at a low methane concentration.Weicheng Liu, Yunpeng Xu, Zhijian Tian, Zhusheng XuDalian Institute of Chemical Physics, The Chinese Academy of Sciences, Dalian 116023, China 2003Journal of Natural Gas Chemistry2003,12,4:3
20Helicobacter pylori antibody responses in association with eradication outcome and recurrence: a population-based intervention trial with 7.3-year follow-up in China显示文摘Objective:To identify serum biomarkers that may predict the short or long term outcomes of anti-Helicobacter pylori(H.pylori)treatment,a follow-up study was performed based on an intervention trial in Linqu County,China.Methods:A total of 529 subjects were selected randomly from 1,803 participants to evaluate total anti-H.pylori immunoglobulin G(Ig G)and 10 specific antibody levels before and after treatment at 1-,2-and 7.3-year.The outcomes of anti-H.pylori treatment were also parallelly assessed by 13C-urea breath test at 45-d after treatment and 7.3-year at the end of follow-up.Results:We found the medians of anti-H.pylori Ig G titers were consistently below cut-off value through 7.3years in eradicated group,however,the medians declined in recurrence group to 1.2 at 1-year after treatment and slightly increased to 2.0 at 7.3-year.While the medians were significantly higher(>3.0 at 2-and 7.3-year)among subjects who failed the eradication or received placebo.For specific antibody responses,baseline seropositivities of Fli D and Hpa A were reversely associated with eradication failure[for Fli D,odds ratio(OR)=0.44,95%confidence interval(95%CI):0.27–0.73;for Hpa A,OR=0.32,95%CI:0.17–0.60].The subjects with multiple positive specific antibodies at baseline were more likely to be successfully eradicated in a linear fashion(Ptrend=0.006).Conclusions:Our study suggested that total anti-H.pylori Ig G level may serve as a potential monitor of longterm impact on anti-H.pylori treatment,and priority for H.pylori treatment may be endowed to the subjects with multiple seropositive antibodies at baseline,especially for Fli D and Hap A.Tianyi Wang Yang Zhang Huijuan Su Zhexuan Li Lian Zhang Junling Ma Weidong Liu Tong Zhou Weicheng You Kaifeng Pan 2017Chinese Journal of Cancer Research2017,29,2:3
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