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Prediction and predictability of a catastrophic local extreme precipitation event through cloud-resolving ensemble analysis and forecasting with Doppler radar observations

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Science China Earth Sciences 2016年第1期59卷 518-532页

作者： QIU xue xing zhang fu Qing Anhui Meteorological Observatory Hefei 230031 China Department of Meteorology Pennsylvania State University University Park PA 16802 USA

Local extreme rain usually resulted in disasters such as flash floods and landslides. Upon today, it is still one of the most difficult tasks for operational weather forecast centers to predict those events accurately. In this paper, we simulate an extreme precipitation event with ensemble Kalman filter(En Kf) assimilation of Doppler radial-velocity observations, and analyze the uncertainties of the assimilation. The results demonstrate that, without assimilation radar data, neither a single initialization of deterministic forecast nor an ensemble forecast with adding perturbations or multiple physical parameterizations can predict the location of strong precipitation. However, forecast was significantly improved with assimilation of radar data, especially the location of the precipitation. The direct cause of the improvement is the buildup of a deep mesoscale convection system with En Kf assimilation of radar data. Under a large scale background favorable for mesoscale convection, efficient perturbations of upstream mid-low level meridional wind and moisture are key factors for the assimilation and forecast. Uncertainty still exists for the forecast of this case due to its limited predictability. Both the difference of large scale initial fields and the difference of analysis obtained from En Kf assimilation due to small amplitude of initial perturbations could have critical influences to the event's prediction. forecast could be improved through more cycles of En Kf assimilation. Sensitivity tests also support that more accurate forecasts are expected through improving numerical models and observations.

关键词： En Kf Doppler radar data Local extreme rain Predictability

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Novel transcatheter aortic heart valves exhibiting excellent hemodynamic performance and low-fouling property

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Journal of Materials Science & Technology 2019年第1期35卷 207-215页

作者： f.Guo K.Jiao Y.Bai J.Guo Q.Chen R.Yang x.zhang Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences School of Materials Science and Engineering University of Science and Technology of China School of Textile and Material Engineering Dalian Polytechnic University Lumenous Peiertech

Transcatheter aortic heart valves(TAHVs) have been widely used for aortic valve replacements, with less trauma and lower clinical risk compared with traditional surgical heart valve replacements. In the present study, composites of poly(ethylene glycol) diacrylate(PEGDA) hydrogels and anisotropic highshrinkage polyethylene terephthalate/polyamide6(PET-PA6) fabric(PEGDA/PET-PA6) were fabricated as artificial heart valve leaflets. Dynamic mechanical analyses(DMA) indicated that PEGDA/PET-PA6 composites possessed anisotropic mechanical properties(i.e., storage moduli ~23.30 ± 1.36 MPa parallel to the aligned fabric fibers and ~9.68 ± 0.90 MPa perpendicular to the aligned fibers at 1 Hz) that were comparable to aortic valve leaflets. The PEGDA/PET-PA6 composites with smooth surfaces were highly hydrophilic(contact angle ~41.6°± 3.8°) and had low-fouling properties without platelet adhesion,suggesting a low risk of thrombogenicity when they interacted with blood. furthermore, transcatheter aortic heart valves were fabricated using nitinol self-expanding frames and PEGDA/PET-PA6 composites as artificial leaflets, which presented excellent hemodynamic performance with a large orifice area(1.75cm2) and low regurgitation(3.41%), thus meeting the requirements of ISO 5840-3 standard. Therefore,PEGDA/PET-PA6 composites had suitable mechanical properties, good biocompatibility, and low-fouling properties, indicating that they might be used for TAHVs in the future.

关键词： Transcatheter aortic heart valve Textile fabric Poly(ethylene glycol)diacrylate Anti-fouling

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Ion motion effects on the generation of short-cycle relativistic laser pulses during radiation pressure acceleration

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High Power Laser Science and Engineering 2014年第2期2卷 1-7页

作者： W.P.Wang x.M.zhang x.f.Wang x.Y.Zhao J.C.xu Y.H.Yu L.Q.Yi Y.Shi L.G.zhang T.J.xu C.Liu Z.K.Pei B.f.Shen State Key Laboratory of High field Laser Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences

The effects of ion motion on the generation of short-cycle relativistic laser pulses during radiation pressure acceleration are investigated by analytical modeling and particle-in-cell simulations. Studies show that the rear part of the transmitted pulse modulated by ion motion is sharper compared with the case of the electron shutter only. In this study, the ions further modulate the short-cycle pulses transmitted. A 3.9 fs laser pulse with an intensity of 1.33×1021W cm-2is generated by properly controlling the motions of the electron and ion in the simulations. The short-cycle laser pulse source proposed can be applied in the generation of single attosecond pulses and electron acceleration in a small bubble regime.

关键词： radiation pressure acceleration short-cycle pulses particle-in-cell simulations.

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STUDY ON DYNAMIC J-INTEGRAL Of MECHANICAL HETEROGENEOUS WELDED JOINT

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Acta Metallurgica Sinica(English Letters) 2004年第6期17卷 934-939页

作者： f.Q.Tian D.Y.He x.Y.Li Y.W.Shi D.zhang InstituteofCompositeMaterials ShanghaiJiaotongUniversityShanghai200030China SchoolofMaterialsScienceandEngineering BeijingPolytechnicUniversityBeijing100022China

Welded joint is a mechanical heterogeneous body, and mechanical heterogeneity has great effect on dynamic fracture behaviour of welded joints. In the present investigation, dynamic response curve and dynamic J-integral of practical undermatched welded joint and whole base and whole weld three-point-bend (TPB) models containing longitudinal crack are com- puted. Dynamic J-integral is evaluated using virtual crack extension (VCE) method and the computation is performed using MARC finite element code. Because of the effect of inertia, dynamic load response curve of computed model waves periodically. Dynamic J-integral evaluated by VCE method is path independent. The effect of inertia has little influence on dynamic J-integral curve. The value of dynamic J-integral of undermatched welded joint is lower than that of whole base metal and higher than that of whole weld metal. The results establish the foundation of safety evaluation for dynamic loaded welded structures.

关键词： virtual crack extension welded joint dynamic response curve dynamic J-integral

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In situ digital testing method for quality assessment of soft soil improvement with polyurethane

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第5期16卷 1732-1748页

作者： x.f.Wang C.J.Wang W.V.Yue Z.J.zhang Z.Q.Yue Department of Civil Engineering China University of Geosciences (Beijing)BeijingChina Department of Water Science and Engineering Zhengzhou UniversityZhengzhouChina Department of Geotechnical Engineering Tongji UniversityShanghaiChina Department of Civil Engineering The University of Hong KongChina

This study purposes an in situ testing method on quality assessment of soil *** drilling data includes the spatial distribution and in situ strength of untreated and treated soil along three different drillholes measured by on-site drilling monitoring *** factual drilling data can characterize the degree of soil improvement by penetration injection with permeable *** from on-site drilling monitoring shows that the linear zones represent constant drilling speeds shown in the plot of drill bit advancement *** drilling time,which indicates the spatial distributions of soil *** soil profile at the study site is composed of four layers,which includes fill,untreated silty clay,treated silty clay,and mucky *** results of soil profile are verified by the parallel site *** constant drilling speeds profile the coring-resistant strength of drilled *** comparing with the untreated silty clay,the constant drilling speeds of the treated silty clay have been decreased by 13.0-62.8%.Two drilling-speed-based indices of 61.2%and 65.6%are proposed to assess the decreased average drilling speed and the increased in situ strength of treated silty *** tests,*** compressive strength(UCS)test,have been performed with core sample to investigate and characterize in situ strength by comparing that with drilling *** show that the average predicted strengths of treated silty clay are 2.4-6.9 times higher than the average measured strength of untreated silty *** UCS-based indices of 374.5%and 344.2%verified the quality assessment(QA)results by this new in situ *** method provides a cost-effective tool for quality assessment of soil improvement by utilizing the digital drilling data.

关键词： Drilling process monitoring system Hydraulic rotary drilling process Constant drilling speed Soil improvement Quality assessment

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Exact elastic impedance tensor for isotropic media

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Science China Earth Sciences 2015年第6期58卷 1350-1360页

作者： zhang feng LI xiangYang State Key Laboratory of Petroleum Resource and Prospecting China University of Petroleum

The existing expressions of elastic impedance,as the generalized form of acoustic impedance,represent the resistance of subsurface media to seismic waves of non-normal incidence,and thus include information on the shear-wave *** this sense,conventional elastic impedance is an attribute of the seismic reflection and not an intrinsic physical property of the subsurface *** derivation of these expressions shares the approximations made for reflectivity,such as weak impedance contrast andisotropic or weakly anisotropic media,which limits the accuracy of reflectivity reconstruction and seismic *** this paper,we derive exact elastic impedance tensors of seismic P-and S-waves for isotropic media based on the stress-velocity *** componentof the impedance tensor represents a unique mechanical property of the *** of P-wave elastic impedance tensor components are discussed for seismic inversion and *** to synthetic data and real data shows the accuracy and robust interpretation capability of the derived elastic impedance in lithology characterizations.

关键词： stress tensor velocity tensor elastic impedance inversion reservoir characterization

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A Pressure-Drop Model for Oil-Gas Two-Phase flow in Horizontal Pipes

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fluid Dynamics & Materials Processing 2021年第2期17卷 371-383页

作者： xinke Yang Shanzhi Shi Hui zhang Yuzhe Yang Zilong Liu Ruiquan Liao Joseph x.f.Ribeiro Engineer Technology Research Institute of xinjiang Oilfield Company Karamay834000China School of Petroleum Engineering Yangtze UniversityWuhan430100China Laboratory of Multiphase Pipe flow of Gas Lift Innovation Center CNPC(Yangtze University)Wuhan430100China Kumasi Technical University KumasiGhana

The accurate prediction of the pressure distribution of highly viscous fluids in wellbores and pipelines is of great significance for heavy oil production and *** flow behavior of high-viscosity fluids is quite different with respect to that of low-viscosity ***,the performances of existing pressure-drop models seem to be relatively limited when they are applied to high-viscosity *** this study,a gas-liquid two-phase flow experiment has been carried out using a 60 mm ID horizontal pipe with air and white *** experimental results indicate that viscosity exerts a significant influence on the liquid holdup and pressure *** the same gas and liquid volume,both the liquid holdup and pressure drop increase with an increase in the *** two existing models,a modified pressure drop method is developed,which is applicable to horizontal pipes for different viscosities and does not depend on the flow *** new method displays a high accuracy in predicting the new experimental data presented here and other published data in literature.

关键词： Horizontal pipe different viscosities pressure drop model gas-liquid two-phase flow

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Effects of dealloying and heat treatment parameters on microstructures of nanoporous Pd

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Journal of Materials Science & Technology 2020年第13期47卷 123-129页

作者： Y.Z.Chen x.Y.Ma W.x.zhang H.Dong G.B.Shan Y.B.Cong C.Li C.L.Yang f.Liu State Key Lab.of Solidification Processing Northwestern Polytechnical University710072 Xi’anChina

Microstructures of nanoporous Pd are essentially important for its physical and chemical *** this work,we show that the microstructures of nanoporous Pd can be tuned by adjusting compositions of the precursor alloys,and dealloying and heat treatment *** the ligament and pore sizes decrease with increasing the electrochemical potential upon dealloying and the concentration of noble component in the precursor *** treatment causes coarsening of the nanoporous *** a critical temperature,the nanoporous structures are subjected to significant *** the critical temperature,surface diffusion is believed to dominate the coarsening *** the critical temperature,the nanoporous structure coarsens remarkably at a rather high rate,which is ascribed to a multiple-mechanism controlled process.

关键词： Nanoporous metals Microstructure Dealloying Kinetics Coarsening

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EffECTS Of HDDR PROCESS ON STRUCTURE AND MAGNETIC PROPERTIES Of Nd(fe,Ti)_(12)N_δ PREPARED BY MECHANICAL ALLOYING

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Acta Metallurgica Sinica(English Letters) 1998年第1期11卷 68-78页

作者： B.ZCui x.K.Sun x.G.Zhao W.Liu Q.f.xiao T.Zhao Z.D.zhang Y.C.Sui Chinese Acad of Sciences Shenyang China

The effects of the hydrogenation-disproportionation-desorption-recombination (HDDR) process on the structure and the magnetic properties of the mechanical alloying (MA) prepared Nd8fe84 Ti8 alloy and its nitride counterpart have been studied in detail. It has been found that Nd(fe, Ti)12Hδ is formed in the temperature range from 300 to 550°℃. The disproportionation is ready to start at 550°℃ and is complete at 960°℃.The desorption and the recombination are almost synchronized. The phase of Nd(fe,Ti)7 is formed at 750°℃ during the HDDR treatment. With increasing temperature of HDDR process, the metastable structure of TbCu7 type is gradually transformed into the structure of ThMn12 type. The intrinsic coercivity and the maximum magnetic energy product increase with increasing temperature of HDDR process.

关键词： Nd(fe Ti)_(12)N_δ compound,magnetic property hydrogenation

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STUDY ON THE PROBLEMS Of CONTACT IN THE NUMERICAL SIMULATION Of SHEET fORMING

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Acta Metallurgica Sinica(English Letters) 2000年第2期13卷 459-464页

作者： K.f. zhang, f.x. Diao, Q.f. Song, W. Wu, K.B. Chen and T.xie Harbin Institute of Technology, Harbin 150001, China

This study is concerned with the problems of contact in the process of numerical simulation of sheet metal forming in rigid visco-plastic shell fEM. In respect of analysis of sheet deep drawing process,for the tool model described by triangular elements, a kind of contact judging algorithm about the correlation between the node of deformed mesh and the triangular element of a tool is presented. In SPf/DB Lagrangian multiplier method is adopted to solve the contact problem between deformed meshes, and a new reliable practical dynamic contact checking algorithm is presented. As computation examples, the simulation results of metal sheet deep drawing and SPf/DB are introduced in this paper.

关键词： kcontact search algorithm rigid visco-plastic shell fEM Lagrangian multiplier method sheet metal forming

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