检索结果-南通市图书馆

Turbulence properties in the solar convection envelope:properties of the overshooting regions

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2009年第5期9卷 585-595页

作者： qian-Sheng Zhang yan.Li National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Graduate School of the Chinese Academy of Sciences Beijing 100049 China

We apply the turbulent convection model （TCM） to investigate properties of turbulence in the solar convective envelope, especially in overshooting regions. The results show TCM gives negative turbulent heat flux uτ＇T＇ in overshooting regions, which is similar to other nonlocal turbulent convection theories. The turbulent temperature fluctuation T＇T＇ shows peaks in overshooting regions. Most important, we find that the downward overshooting region below the base of the solar convection zone is a thin cellular layer filled with roll-shaped convective cells. The overshooting length for the temperature gradient is much shorter than that for element mixing because turbulent heat flux of downward and upward moving convective cells counteract each other in this cellular overshooting region. Comparing the models＇ sound speed with observations, we find that taking the convective overshooting into account helps to improve the sound speed profile of our nonlocal solar models. Comparing the p-mode oscillation frequencies with observations, we validated that increasing the diffusion parameters and decreasing the dissipation parameters of TCM make the p-mode oscillation frequencies of the solar model be in better agreement with observations.

关键词： convection - turbulence - Sun helioseismology

Construction of Supersaturated Design with Large Number of Factors by the Complementary Design Method

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2013年第2期29卷 253-262页

作者： yan.LIU Min-qian LIU School of Mathematical Sciences Tianjin Normal University Department of Statistics School of Mathematical Sciences and LPMC Nankai University

Supersaturated designs （SSDs） have been widely used in factor screening experiments. The present paper aims to prove that the maximal balanced designs are a kind of special optimal SSDs under the E（fNOD） criterion. We also propose a new method, called the complementary design method, for constructing E（fNoD） optimal SSDs. The basic principle of this method is that for any existing E（fNOD） optimal SSD whose E（fNOD） value reaches its lower bound, its complementary design in the corresponding maximal balanced design is also E（fNOD） optimal. This method applies to both symmetrical and asymmetrical （mixed-level） cases. It provides a convenient and efl：icient way to construct many new designs with relatively large numbers of factors. Some newly constructed designs are given as examples.

关键词： balanced design coincidence number complementary design equidistant design weak equidistantdesign

MIXED DISCONTINUOUS GALERKIN METHOD FOR QUASI-NEWTONIAN STOKES FLOWS

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2024年第3期42卷 885-910页

作者： yan.ia qian Fei Wang Wenjing yan School of Mathematics and Statistics Xi'an Jiaotong UniversityXi'an 710049China School of Mathematics and Statistics&State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

In this paper,we introduce and analyze an augmented mixed discontinuous Galerkin(MDG)method for a class of quasi-Newtonian Stokes *** the mixed formulation,the unknowns are strain rate,stress and velocity,which are approximated by a discontinuous piecewise polynomial triplet ■for k≥***,the discontinuous piecewise polynomial function spaces for the field of strain rate and the stress field are designed to be *** addition,the pressure is easily recovered through simple *** the benefit of the analysis,we enrich the MDG scheme with the constitutive equation relating the stress and the strain rate,so that the well-posedness of the augmented formulation is obtained by a nonlinear functional *** k≥0,we get the optimal convergence order for the stress in broken ■(div)-norm and velocity in L^(2)-***,the error estimates of the strain rate and the stress in-norm,and the pressure in L^(2)-norm are optimal under certain ***,several numerical examples are given to show the performance of the augmented MDG method and verify the theoretical *** evidence is provided to show that the orders of convergence are sharp.

关键词： Quasi-Newtonian fows Mixed discontinuous Galerkin method Symmetric strain rate Symmetric stress Optimal convergence orders

Copper-catalyzed arenes amination with saccharins

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 2015年第8期58卷 1354-1358页

作者： Kai Sun yan.Li qian Zhang College of Chemistry and Chemical Engineering Anyang Normal University Department of Chemistry Northeast Normal University

A novel copper-catalyzed direct C–N formation reaction of simple arenes with cheap and pharmacological saccharin derivatives under relatively mild conditions was developed with arenes as limiting *** work provided a ... 详细信息

关键词： aromatic amines C-N bond formation arenes saccharins arenes as limiting reagents

Perfect optomechanically induced transparency in two-cavity optomechanics

在线全文

学校读者我要写书评

暂无评论

Frontiers of physics 2023年第5期18卷 245-253页

作者： Lai-Bin qian Xiao-Bo yan School of Physics and Electronic Engineering Northeast Petroleum UniversityDaqing 163318China

Here,we study the controllable optical responses in a two-cavity optomechanical system,especially on the perfect optomechanically induced transparency(OMIT)in the model which has never been studied *** results show that the perfect OMIT can still occur even with a large mechanical damping rate,and at the perfect transparency window the long-lived slow light can be *** addition,we find that the conversion between the perfect OMIT and optomechanically induced absorption can be easily achieved just by adjusting the driving field strength of the second *** believe that the results can be used to control optical transmission in modern optical networks.

关键词： perfect optomechanically induced transparency slow light optomechanically induced absorption cavity optomechanics

Piezoelectric fbers for fexible and wearable electronics

在线全文

学校读者我要写书评

暂无评论

Frontiers of Optoelectronics 2023年第1期16卷 49-63页

作者： Shengtai qian Xingbei Wang Wei yan State Key Laboratory for Modifcation of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai 201620China School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore 639798Singapore School of Materials Science and Engineering Nanyang Technological UniversitySingapore 639798Singapore

Flexible and wearable electronics represent paramount technologies ofering revolutionized solutions for medical diagnosis and therapy,nerve and organ interfaces,fabric computation,robot-in-medicine and *** ubiquitous in everyday life,piezoelectric materials and devices play a vital role in fexible and wearable electronics with their intriguing functionalities,including energy harvesting,sensing and actuation,personal health care and *** a new emerging fexible and wearable technology,fber-shaped piezoelectric devices ofer unique advantages over conventional thin-flm *** this review,we survey the recent scientifc and technological breakthroughs in thermally drawn piezoelectric fbers and fber-enabled intelligent *** highlight the fber materials,fber architecture,fabrication,device integration as well as functions that deliver higher forms of unique applications across smart sensing,health care,space security,actuation and energy *** conclude with a critical analysis of existing challenges and opportunities that will be important for the continued progress of this feld.

关键词： Piezoelectric materials and devices Flexible electronics Smart fbers Intelligent fabrics

Relationship Between Microstructures and Microhardness in High-Speed Friction Stir Welding of AA6005A-T6 Aluminum Hollow Extrusions

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 115-126页

作者： Xiang-qian Liu Hui-Jie Liu yan.Yu Luoyan. Ship Material Research Institute Luoyang 471023China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China

AA6005 A-T6 aluminum hollow extrusions were friction stir welded at a fixed high welding speed of 2000 mm/min and various rotation *** results showed that the heat-aff ected zone(HAZ)retained the similar grain structure as the base material except some grain coarsening,and the density of dislocations andβ′precipitates were almost unchanged,indicating that the high welding speed inhibited the coarsening and dissolution ofβ″precipitates via fast cooling *** thermo-mechanically aff ected zone(TMAZ)was characterized by elongated and rotated grains,in which a low density ofβ′precipitates and the highest density of dislocations were *** highest heat input and severest plastic deformation occurring in the nugget zone(NZ)resulted in the occurrence of dynamic recrystallization and a high density of ***,all theβ″precipitates and most of theβ′precipitates dissolved into the matrix,and a fewβ′precipitates were transformed intoβ*** microhardness was controlled by the precipitation and solution strengthening in the HAZ,by the dislocation and precipitation strengthening in the TMAZ,and by the fine-grain and dislocation strengthening in the *** the increase in rotation speed,the peak and the lowest microhardness value increased monotonously.

关键词： Aluminum hollow extrusions High-speed friction stir welding Grain structure Dislocation and precipitates Microhardness distribution

Plasma treated M1 MoVNbTeO_(x)-CeO_(2) composite catalyst for improved performance of oxidative dehydrogenation of ethane

在线全文

学校读者我要写书评

暂无评论

Green Energy & Environment 2023年第3期8卷 904-914页

作者： Shuairen qian Yuxin Chen Binhang yan.Yi Cheng Department of Chemical Engineering Tsinghua UniversityBeijing100084China

High activity and productivity of MoVNbTeO_(x) catalyst are challenging tasks in oxidative dehydrogenation of ethane(ODHE)for industrial *** this work,phase-pure M1 with 30 wt%CeO_(2) composite catalyst was treated by oxygen plasma to further enhance catalyst *** results show that the oxygen vacancies generated by the solid-state redox reaction between M1 and CeO_(2) capture active oxygen species in gas and transform V^(4+)to V^(5+)without damage to M1 *** space-time yield of ethylene of the plasma-treated catalyst was significantly increased,in which the catalyst shows an enhancement near~100% than that of phase-pure M1 at 400℃ for ODHE *** treatment for catalysts demonstrates an effective way to convert electrical energy into chemical energy in catalyst *** conversion is achieved by using the catalyst as a medium.

关键词： Oxidative dehydrogenation of ethane(ODHE) MoVNbTeO_(x) Composite catalyst Oxygen plasma Energy conversion

Two-weight Norm Inequalities for Local Fractional Integrals on Gaussian Measure Spaces

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2022年第7期38卷 1203-1228页

作者： Bo Ning DI qian Jun HE Dun yan.yan School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049P.R.China School of Applied Science Beijing Information Science and Technology UniversityBeijing 100192P.R.China

In this paper,the authors establish the two-weight boundedness of the local fractional maximal operators and local fractional integrals on Gaussian measure spaces associated with the local *** precisely,the authors first obtain the two-weight weak-type estimate for the locala fractional maximal operators of orderαfrom L^(p)(v)to L^(q,∞)(u)with 1≤p≤qa A_(p,q,a)^(b') ,and then obtain the two-weight weak-type estimate for the local fractional *** addition,the authors obtain the two-weight strong-type boundedness of the local fractional maximal operators under a condition of(u,v)∈M_(p,q,a)^(6a+9√da^2) and the two-weight strong-type boundedness of the local fractional *** estimates are established by the radialization method and dyadic approach.

关键词： Local fractional integral local fractional maximal operator two-weight inequality Gaussian measure space