检索结果-南通市图书馆

Stability of core-annular flow of power-law fluids in the presence of interfacial surfactant

Science China(physics,Mechanics & Astronomy) 2010年第5期53卷 933-943页

作者： SUN XueWei,PENG Jie & ZHU KeQin department of Engineering Mechanics,tsinghua {2.,beijing 100084,China 1. department of Engineering Mechanics Tsinghua University Beijing 100084 China

The shear-thinning influence on the core-annular flow stability of two immiscible power-law fluids is considered by making a linear stability *** flow is driven by an axial pressure gradient in a straight pipe with the interface between the two fluids occupied by an insoluble *** the basic flow for this core-annular arrangement,the analytical solution is obtained with respect to the power-law fluid *** linearized equations for the evolution of infinitesimal disturbances are derived and the stability problem is formulated as a generalized matrix eigenvalue problem,which is solved by using the software package Matlab based on the QZ *** shear-thinning property is found to have marked influence on the power-law fluid core-annular flow stability,which is reflected in various ***,the capillary instability is magnified by the shear-thinning property,which may lead to an essential difference between power-law and Newtonian fluid *** when the interface is close to the pipe wall,the power-law fluid flow may be unstable while the Newtonian fluid flow is ***,under disturbances to the interface a velocity discontinuity at the interface appears which is destabilizing to the *** magnitude of this velocity discontinuity is affected by the power-law index and the flow stability is influenced ***,the shear-thinning property may induce new stability modes which do not appear in the Newtonian fluid *** flow stability shows much dependence on the interface location,the role of which was neglected in most previous *** shear-thinning fluid flow is more unstable to long wave disturbances when the interface is close to the pipe wall,while the Newtonian fluid flow is more unstable when the interface is close to the pipe *** this trend is changed by the addition of interfacial surfactant,for which the power-law fluid flow is more stable no matter where the interface is loca

关键词： core-annular flow power-law fluid interfacial surfactant linear stability analysis

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Analysis on ignition and extinction of n-heptane in homogeneous systems

引用

Science China(Technological Sciences) 2005年第5期48卷 556-569页

作者： LIU Yongfeng1 & PEI Pucheng2.1. Mechanical and Electrical Engineering department, beijing Institute of Civil Engineering and Architec-ture, beijing 100044, China 2. State Key Laboratory of Automotive Safety and Energy, tsinghua university, beijing 100084, China 1. Mechanical and Electrical Engineering department Beijing Institute of Civil Engineering and Architecture 100044 Beijing China 2. State Key Laboratory of Automotive Safety and Energy Tsinghua University 100084 Beijing China

To calculate ignition delay times, the governing equations about species and temperature, which are in a closed volume based on the theory of thermal explosion and in a continuously stirred flow reactor, are deducted. The method referred to steady state assumptions is based on the observation that due to very fast chemical processes in combustion problems many chemical species and reactions are in a quasi-steady state or partial equilibrium. When a species is assumed to be in the steady state, the corresponding differential equation can be replaced by an algebraic relation, which reduces the computational costs. The steady state solution of the reactor equations describes the three ignition temperature regimes and get “S-shaped curve”. The reduced simplified 4-step mechanism for n-heptane from 1011 elementary reactions leads with the steady state assumptions to linear differential equations, which is solved. The simulation results of the 4-step reduced mechanism for n-heptane are fitted well with the experiment data. At last, two important parameters are discussed thoroughly and the temperature perturbation is given. It reduces the computational efforts considerably without losing too much accuracy and further supplies numerical methods for turbulent combustion in the diesel engine.

关键词： ignition delay times, thermal runaway, steady state assumptions, continuously stirred flow reactor.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Two-fluid Dynamics in Clusters of Galaxies

引用

Chinese Journal of Astronomy and Astrophysics 2005年第1期5卷 6-20页

作者： Yu-Qing LouNational Astronomical Observatories, Chinese Academy of Sciences, beijing 100012.1} of {2. & tsinghua Center for Astro{2. (THCA), tsinghua university, beijing 100084 department of Astronomy and Astro{2., The university of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 USA National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

We develop a theoretical formulation for the large-scale dynamics of galaxy clusters involving two spherical 'isothermal fluids' coupled by their mutual gravity and derive asymptotic similarity solutions analytically. One of the fluids roughly approximates the massive dark matter halo, while the other describes the hot gas, the relatively small mass contribution from the galaxies being subsumed in the gas. By properly choosing the self-similar variables, it is possible to consistently transform the set of time-dependent two-fluid equations of spherical symmetry with self-gravity into a set of coupled nonlinear ordinary differential equations (ODEs). We focus on the analytical analysis and discuss applications of the solutions to galaxy clusters.

关键词： dark matter - hydrodynamics - ISM: general - galaxies: clusters -outflows winds - shocks

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

QUASI-STATIONARY DISTRIBUTIONS FOR THE RADIAL ORNSTEIN-UHLENBECK PROCESSES

引用

Acta Mathematica Scientia 2008年第3期28卷 513-522页

作者：叶俊 department of Mathematical Sciences Tsinghua University

The purpose of this article is to obtain the quasi-stationary distributions of the δ（δ 〈 2.-dimensional radial Ornstein-Uhlenbeck process with parameter -λ by using the methods of Martinez and San Martin （2.01）. It is described that the law of this process conditioned on first hitting 0 is just the probability measure induced by a （4 - δ）- dimensional radial Ornstein-Uhlenbeck process with parameter -λ. Moreover, it is shown that the law of the conditioned process associated with the left eigenfunction of the process conditioned on first hitting 0 is induced by a one-parameter diffusion.

关键词： Radial Ornstein-Uhlenbeck process quasi-stationary distribution quasiinvariant

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A Remark on the Symplectic Blow-up in Dimension 4

引用

Acta Mathematica Sinica,English Series 1996年第4期12卷 379-384页

作者： Ma Renyi department of Applied Mathematics tsinghua university {2., 100084 China department of Applied Mathematics Tsinghua University Beijing China

In this note, we prove that the symplectic blow-up or blow-down in the dimension 4 is rigid, i.e. the symplectic area of the divisor does not exceed the symplectic radius of the neighbourhood on which we do the blow-u... 详细信息

关键词： J-Holomorphic disc Contact manifold Symplectic blow-up

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Centralizers and Iterate Radicals of Morse-Smale Diffeomorphisms of the Circle

引用

Acta Mathematica Sinica,English Series 1995年第1期11卷 1-11页

作者： Zhang Meirong department of Applied Mathematics tsinghua university {2.,100084 China department of Applied Mathematics Tsinghua University Beijing People's Republic of China

In this paper,we will use the embedding flows in[1],[2.to give a complete descrip- tion of the smooth centralizers and iterate radicals of all C^r(r≥2.Morse-Smale diffeomorphisms of the circle S^*** a result,we prove... 详细信息

关键词： Centralizers and Iterate Radicals of Morse-Smale Diffeomorphisms of the Circle TDFs

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Local Gromov-Witten invariants of canonical line bundles of toric surfaces

引用

Science China Mathematics 2010年第6期53卷 1571-1582页

作者： YANG Fei & ZHOU Jian department of Mathematical Sciences,tsinghua {2.,beijing 100084,China 1. department of Mathematical Sciences Tsinghua University Beijing 100084 China

We define and compute by localizating the local equivariant Gromov-Witten invariants of the canonical line bundles of toric surfaces,not necessarily Fano.

关键词： local Gromov-Witten invariants localization partition function geometric engineering

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Arbitrarily long distance quantum communication using inspection and power insertion

引用

Chinese Science Bulletin 2009年第1期54卷 158-162页

作者： WANG WanYing1,2.WANG Chuan1,2.ZHANG GuangYu1,3 & LONG GuiLu1,2.1 department of physics,{2. university,beijing 100084,China 2.{2. National Laboratory for Information Science and Technology,{2. university,beijing 100084,China 3 College of Applied Science,Harbin university of Science and Technology,Harbin 150080,China department of physics Tsinghua University Beijing 100084 China tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China College of Applied Science Harbin University of Science and Technology Beijing 100084 China

The biggest obstacle for long distance quantum communication is the channel loss and the channel noise on photons. In this paper,a method to solve this problem was analyzed using inspection and power insertion (IPI). It is proved that quantum communication may be established over arbitrarily long distance using this technology. The amount of resources required is a polynomial function of the dis-tance. IPI is proposed as a general technique to prolong quantum secure direct communication where secret messages are transmitted directly over a quantum channel.

关键词：长距离量子通信量子安全通信量子密匙分布噪声

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

DYNAMIC AND KINEMATIC WAVE MODELSFOR 1-D RILL FLOW: A COMPARISON

引用

International Journal of Sediment Research 1999年第2期14卷 95-105页

作者： SHAO Xuejun (department of Hydraulic Engineering, tsinghua university,{2., China)

Overland flows on hillslopes due to rainfall excess are numerically simulated with a simplified strip microtopography which has one single straight rill, and comparisons are made between predictions of a dynamic wave model (DWM) and a kinematic wave model (KWM). Overland flow on the strip is treated as one-dimensional and interrill flow is not simulated. The DWM is based on the Saint-Venant equation, and the KWM is derived using the Chezy formula. A numerical scheme is developed which solves the non-linear DWM equations in a similar way to that of solving the KWM equations, *** the basis of the method of characteristics. This scheme greatly reduces the complexity of the solution procedure and therefore allows the use of DWM in process-based catchment models involving a large number of topographical elements, i.e., hillslopes. Simulation result shows that. in terms of the predicted flow velocity V and depth h, the *** model is an accurate approximation to the dynamic one for broad sheet overland flows resulted from normal rainfall excess rates (1-3 mm/min). However. for small rill width, e.g. B2.cm. or if the rainfal excess rate is extremely large (e.g.. 2. mm/min). differences of V and h between the two models will be significant. In general, the KWM tends to underestimate rill flow depth but overestimate its velocity, especially for small rill width. though it does give the same steady discharge per unit width, q =V h, as that predicted by DWM for steady rainfall excess rate. At the rising stage of the hydrograph, KWM predicts higher unit width discharge q, which leads to overestimation of rill detachment as a stream power function method is used.

关键词： Overland flow Rill flow Kinematic wave model Method of characteristics

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Solving the input data in error correc-tion of optical fabrication by finite Fourier coefficient algorithm

引用

Science China(Technological Sciences) 2006年第1期49卷 50-60页

作者： CHENG Haobo1,2. SUN Guozheng3 & FENG Zhijing2.1. department of Optical Engineering, beijing Institute of Technology, beijing 100081, China 2. department of Precision Instruments and Mechanology, tsinghua university, beijing 100084, China 3. China North Industries Group Corporation, beijing 100089, China 1. department of Optical Engineering Beijing Institute of Technology Beijing 100081 China 2. department of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China 3. China North Industries Group Corporation Beijing 100089 China

A free-form lens (FFL) is a special surface that is difficult to be fabricated. FFL are usually fabricated by computer-controlled optical surfacing (CCOS) technique. During CCOS, the material removal amount is determined by the unit removal function (URF) convoluting with the input data――the dwell time. When the removal amount and the URF are known, how to solve the input data involves the special algorithm――deconvolution. Usually, the input data are solved by virtue of low pass filter or iterative methods. However, an approximation solution would destroy the machining stability nec-essary to perform precisely CCOS. In this paper, to solve the input data, a new method that is based on the finite Fourier coefficient is put forward. It can give a continuous and accurate solution for fabricating choice. Several parameters are simulated, which influ-ence the process of CCOS, and evaluating on the effect of the method is also carried out. Experimental results verify that this method is suitable for guiding the manufacturing of high precision FFL.

关键词： optical fabrication, computer controlled optical surfacing, free-form lens, finite Fourier coefficient, error correction.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：