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关键词： 薄壁箱梁   面内剪切效应   能量变分法   挠度   剪力流  

摘要： 以薄壁箱梁的弯曲理论为基础,从分析微板剪力流出发,结合弹性理论中求解平面应力问题的假设,推导考虑薄壁箱梁各板面内剪切效应时的弯曲纵向位移函数,同时从理论上导出剪力滞翘曲位移函数。运用能量变分原理及铁木辛柯深梁理论的假设简化并求解考虑各板面内剪切效应的纵向位移函数,并给出数值算例。研究结果表明:按本文推导的考虑各板面内剪切效应的位移函数计算的简支梁跨中截面正应力与实测值及有限元值吻合良好,剪应力与挠度较以往方式求解的结果更为准确,且箱梁挠度及腹板剪应力计算值相对于初等梁的结果均有明显增加,最大增量达到21%。

关键词： Pulsation   Fluidized bed   Fine coal   Density   Separation   PARTICLE-SIZE   SEPARATION   BUBBLE   MODEL  

摘要： Coal is one of the most important primary energy resources worldwide. Because of the shortage of water resources, dry coal beneficiation has become a research hotspot. A pulsating air dense medium fluidized bed (PADMFB) that introduces a pulsating air flow to the air dense medium fluidized bed was proposed for fine coal particles. In order to investigate whether coal particles can be separated by density in PADMFB, as well as size affecting the results under practical condition, the time ratio and the largest distance between two equal-falling particles were used as indexes for analyzing the beneficiation possibility in this paper. The equations of time ratio and the largest distance between two equal-falling particles when sinking from the surface to the bottom of the bed were established. Fine coal was confirmed to be separated theoretically in the PADMFB. Furthermore, the fine coal -6 + 1 mm size fraction was separated using the PADMFB. The ash content of the coal could be reduced from 56.15% to 33.69% when the gas pulsation frequency was 1.82 Hz, and the probable error, E value was 0.085 g/cm(3) in experimental setup. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Urban centres   Polycentric   Passenger flows   Spatial clustering: urban planning   NETWORK STRUCTURE   TRAVEL PATTERNS   LOS-ANGELES   URBAN   EMPLOYMENT   POLYCENTRICITY   CITY   ACCESSIBILITY   POPULATION   SUBCENTERS  

摘要： Urban geography could be characterized by analysing the;patterns that describe the flows of people and goods. Measuring urban structures is essential for supporting an evidence-based spatial planning policy. The objective of this study is to examine how the spatial-temporal distribution of public transport passenger flow could be used to reveal urban structure dynamics. A methodology to identify and classify centres based on mobility data was applied to Metropolitan Stockholm in Sweden using multi-modal public transport passenger flows. Stockholm is known for its long-term monocentric planning with a dominant central core and radial public transport system. Strategic nodes along its radial public transport system have been a focus for development of sub-centres. Although the regional planning policy embraces a shift towards a polycentric planning policy, the results indicate that this has not been realized insofar. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Tapered fluidized bed   Minimum fluidization velocity   Minimum velocity of full fluidization   Maximum pressure drop   Bed expansion ratio   Empirical model   REGULAR PARTICLES   PREDICTION   DRY   BEHAVIOR   POWDERS   FORCES   WASTE  

摘要： Understanding the hydrodynamic behavior of tapered fluidized beds is essential for accurate design and better operation in these fluid-solid contactors. Minimum fluidization velocity, minimum velocity of full fluidization, maximum pressure drop and bed expansion ratio are more important hydrodynamic characteristics in tapered fluidized beds. In this study, based on experimental data, dimensional analysis has been used to develop dimensionless correlations for predicting hydrodynamic characteristics of Geldart B particles in tapered fluidized bed. The effects of bed geometry, static bed height, particle density, size, and sphericity and also interparticle forces on hydrodynamic behavior of tapered fluidized beds have been investigated. Numerical comparison indicated that the predictions of the present model are in good agreement with experimental data. The ability of the proposed models to predict hydrodynamic characteristics of fluidized particles has been compared to that of existing models in the literatures. (C) 2015 Elsevier B.V. All rights reserved.

关键词： DIFFERENTIAL equations   MATHEMATICAL physics   MATHEMATICAL models   MATHEMATICS   DIRECTION field (Mathematics)  

摘要： We study the radius of convergence of a differential equation on a smooth Berkovich curve over a non-archimedean complete valued field of characteristic O. Several properties of this function are known: F. Baldassarri proved that it is continuous (see [2]) and the authors showed that it factorizes by the retraction through a locally finite graph (see [12] and [10]). Here, assuming that the curve has no boundary or that the differential equation is overconvergent, we provide a shorter proof of both results by using potential theory on Berkovich curves.

关键词： Boltzmann equation   Discontinuous Galerkin methods   Spectral methods   High order methods   SCHEME  

摘要： In this paper we present a Discontinuous Galerkin method for the Boltzmann equation. The distribution function f is approximated by a shifted Maxwellian times a polynomial in space and momentum, while the test functions are chosen as polynomials. The first property leads to consistency with the Euler limit, while the second property ensures conservation of mass, momentum and energy. The focus of the paper is on efficient algorithms for the Boltzmann collision operator. We transform between nodal, hierarchical and polar polynomial bases to reduce the inner integral operator to diagonal form. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Venous intervention   Paediatric interventions   Embolization   Peripheral vascular   Vein   Vascular malformations   SODIUM TETRADECYL SULFATE   TISSUE VENOUS MALFORMATIONS   LYMPHATIC MALFORMATIONS   PERCUTANEOUS SCLEROTHERAPY   CYSTIC HYGROMA   ETHANOL SCLEROTHERAPY   MR-ANGIOGRAPHY   ADULT PATIENTS   SCLEROSING THERAPY   SURGICAL-TREATMENT  

摘要： This review article aims to give an overview of the current state of imaging, patient selection, agents and techniques used in the management of low-flow vascular malformations. The review includes the current classifications for low-flow vascular malformations including the 2014 updates. Clinical presentation and assessment is covered with a detailed section on the common sclerosant agents used to treat low-flow vascular malformations, including dosing and common complications. Imaging is described with a guide to a simple stratification of the use of imaging for diagnosis and interventional techniques.

关键词： Circulating fluidized bed   Flow regimes   Pressure   CPFD simulation   Non-uniformity   Power spectrum   HILBERT-HUANG TRANSFORM   EXTERNAL HEAT-EXCHANGER   TIME-SERIES ANALYSIS   REGIMES   HYDRODYNAMICS   IDENTIFICATION   DECOMPOSITION   FLUCTUATIONS   DISTRIBUTOR   BOILER  

摘要： For large scale circulating fluidized bed (CFB) boilers, a new type of annular combustion chamber was proposed to improve the secondary air penetration and provide adequate space to arrange the heat transfer surface. To investigate the gas-solids flow characteristics and optimize the structure of the annular combustion chamber, a "cold" test rig was built with a cross sectional area of 1.18 m(2) and a height of 8.0 m. High frequency pressure transducers were used to obtain the pressure fluctuations characteristics. CFD simulation based on computational particle fluid dynamic (CPFD) was used to obtain pressure fluctuations and particles concentration. The time domain analysis, power spectrum analysis and Hilbert-Huang transform were applied to the experimental and simulation data. Different flow regimes including single bubble regime, exploding bubble regime and turbulent fluidization regime were identified. The flow characteristics were investigated in terms of standard deviation and higher-order moments, auto-correlation, power spectrum, and EMD energy entropy. The results show that the gas-solids flow in the bottom region of the annular combustion chamber was relatively uniform. The gas-solids flow in annular combustion chamber was proved similar to that in a conventional CFB riser. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Conservative discretization   Fokker-Planck   Rosenbluth potentials   Fully implicit algorithms   Jacobian-free Newton-Krylov   Multigrid preconditioning   CONSERVATIVE DIFFERENCE SCHEME   KINETIC SIMULATION   NUMERICAL SCHEME   ACCURATE   TRANSPORT   EFFICIENT   SYSTEM  

摘要： In this study, we demonstrate a fully implicit algorithm for the multi-species, multidimensional Rosenbluth-Fokker-Planck equation which is exactly mass-, momentum-, and energy-conserving, and which preserves positivity. Unlike most earlier studies, we base our development on the Rosenbluth (rather than Landau) form of the Fokker-Planck collision operator, which reduces complexity while allowing for an optimal fully implicit treatment. Our discrete conservation strategy employs nonlinear constraints that force the continuum symmetries of the collision operator to be satisfied upon discretization. We converge the resulting nonlinear system iteratively using Jacobian-free Newton-Krylov methods, effectively preconditioned with multigrid methods for efficiency. Single- and multi-species numerical examples demonstrate the advertised accuracy properties of the scheme, and the superior algorithmic performance of our approach. In particular, the discretization approach is numerically shown to be second-order accurate in time and velocity space and to exhibit manifestly positiveentropy production. That is, H-theorem behavior is indicated for all the examples we have tested. The solution approach is demonstrated to scale optimally with respect to grid refinement (with CPU time growing linearly with the number of mesh points), and timestep (showing very weak dependence of CPU time with time-step size). As a result, the proposed algorithm delivers several orders-of-magnitude speedup vs. explicit algorithms. Published by Elsevier Inc.