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1.
《Journal of Fluids and Structures》2006,22(6-7):741-755
A number of occurrences of flow-induced vibration in the power-generating industry are presented, many in nuclear plant where all incidents/problems have to be reported. Specifically, cases of (i) vortex-induced vibration (VIV), (ii) fluidelastic instability in cylinder arrays, (iii) axial and (iv) annular-flow-induced vibration, (v) leakage-flow instability and (vi) shell-type ovalling are discussed. For items (ii), (v) and (vi), a few words on the mechanisms underlying the vibration are provided. 相似文献
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Marvin A. Hamstad 《Experimental Mechanics》1986,26(1):7-13
The technique of acoustic emission has two broad applications areas. The first is nondestructive evaluation. The second is
as a tool in studies or research which are not fundamentally directed towards acoustic emission. It is this second application
with which we are concerned here. Acoustic emission is a very useful tool in this role because of its high sensitivity, real-time
capability, volume-monitoring approach, and sensitivity to any process or mechanism which generates sound waves. This paper
presents a comprehensive review of areas where acoustic emission (AE) has been used for materials studies on composite materials.
The following fields, among others, will be covered: (1) time-dependent composite properties, (2) impact studies, (3) correlation
of AE with stress level, (4) application to matrix cure studies, (5) relationship of AE-detected damage to other measures
of damage, (6) studies of the effects of matrix material, (7) application to differences in second phase, (8) interface studies,
(9) AE and dimensional stability, (10) AE applied to orientation studies, and (11) environmental effects. This review will
emphasize the roles that AE can play as a tool for the materials scientist: (1) discovery of damage mechanisms, (2) characterization
of damage progression with increasing time or stress, (3) optimization of fabrication variables, and (4) reduction in the
numbers of test specimens required in various studies. 相似文献
4.
A Boundary Element Method (BEM)-based inverse algorithm utilizing the iterative regularization method, i.e. the Conjugate
Gradient Method (CGM), is used to solve the Inverse Heat Conduction Problem (IHCP) of estimating the unknown transient boundary
heat flux in a multi-dimensional domain with arbitrary geometry.
Results show that the advantages of applying the CGM in the inverse calculations lie in that the major difficulties in (i)
choosing a suitable quadratic norm, (ii) determining a proper regularization order and (iii) determining the optimal smoothing
(or regularization) coefficient in the conventional Regularization Method (RM) are avoided.
Received on 27 October 1997 相似文献
5.
On the boundedness and the stability properties of solution of certain fourth order differential equations 总被引:1,自引:1,他引:0
This paper investigates equation(1)in two cases:(i)P≡0,(ii)P(≠O)satisfies|P(t,x,y,z,ω)|≤(A |y| |z| |ω|)q(t),where q(t)is a nonnegative function of t.For case(i)the asymptotic stability in the large of the trivial solution x=0 is investigatedand for case(ii)the boundedness result is obtained for solutions of equation(1).Theseresults improve and include several well-known results. 相似文献
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Polystyrene (PSt) microspheres with diameter of 375 nm to be used as the seeds for seeded emulsion polymerization were prepared via emulsion polymerization using potassium persulfate (KPS) as initiator in ethanol-water mixed solvents.Emulsifier-free seeded emulsion copolymerization of styrene (St) with acrylonitrile (AN) was carried out in the presence of poly(ethylene glycol) monomethoxymonomethacrylate (PEGm)macromonomer as reactive stabilizer and 2,2'-azobisisobutyronitrile (AIBN) as initiator to obtain submicron-sized PEGm graft poly(styrene-co-acrylonitrile) (PEGm-g-PSAN) composite particles with unique morphology.Scanning electron microscopy (SEM) indicated that St and AN together contributed to forming the unusual morphology.The concentration of St and AN,total monomer concentration,initiator type and the monomer adding method remarkably affected the morphology of the composite polymer particles. 相似文献
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本文所提算法适用于二维和三维多介质流体力学两步欧拉数值方法中输运计算的混合网格(包括自由面网格)界面处理。在一个混合网格中,界面被近似地看作直线(二维)或平面(三维)。整个方法分为三步:(1)第一步,用混合网格周围的八个网格的介质面积份额(二维)或二十六个网格的介质体积份额(三维)确定界面的法线方向;第二步,用混合网格的本身的介质面积份额(二维)或体积份额(三维)确定界面的方程(位置);第三步,用此直线方程求出通过网格边界的流以及下一时刻网格的面积份额(二维)或体积份额(三维)。最后给出了用此方法所做的一些数值计算及与SLIC算法的比较。 相似文献
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Enhancement of energy efficiency for mechanical production of fine and ultra-fine particles in comminution 总被引:1,自引:0,他引:1
Yanmin Wang Eric Forssberg 《中国颗粒学报》2007,5(3):193-201
This paper presents the energy requirements for mechanical production of fine and ultra-fine particles in comminution. Recent approaches for effective size reduction and energy saving in comminution are described, viz., (a) development and application of new mills/classifiers, (b) adjustment of the bead characterization in stirred bead mills, (c) hybrid comminution systems with roller-press and media mill, (d) assisted methods, and (e) simulation.2007 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. 相似文献
11.
We re-examine the large amplitude transverse oscillations of axisymmetric disks spinning near a critical speed resonance as considered by Raman and Mote (Int. J. Non-linear Mech. 34 (1) (1999) 139). Averaged equations in traveling wave based coordinates are shown to provide a transparent explanation for certain bifurcations presented in Raman and Mote (Int. J. Non-linear Mech. 34 (1) (1999) 139). The theoretical results in Raman and Mote (Int. J. Non-linear Mech. 34 (1) (1999) 139) are proved analytically, and an enhanced interpretation of their results is presented. 相似文献
12.
Hong Chu Hongyan Wang Zhongbin Ni Xiaoya Liu Mingqing Chen 《Particuology》2008,6(5):369-375
Polystyrene (PSt) microspheres with diameter of 375 nm to be used as the seeds for seeded emulsion polymerization were prepared via emulsion polymerization using potassium persulfate (KPS) as initiator in ethanol-water mixed solvents. Emulsifier-free seeded emulsion copolymerization of styrene (St) with acrylonitrile (AN) was carried out in the presence of poly(ethylene glycol) monomethoxymonomethacrylate (PEGm) macromonomer as reactive stabilizer and 2,2'-azobisisobutyronitrile (AIBN) as initiator to obtain submicron-sized PEGm graft poly(styrene-coacrylonitrile) (PEGm-g-PSAN) composite particles with unique morphology. Scanning electron microscopy (SEM) indicated that St and AN together contributed to forming the unusual morphology. The concentration of St and AN, total monomer concentration, initiator type and the monomer adding method remarkably affected the morphology of the composite polymer particles. 相似文献
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M.Shamsul Alam 《International Journal of Non》2004,39(8):1343-1357
A modified and compact form of Krylov-Bogoliubov-Mitropolskii (KBM) (Introduction to Nonlinear Mechanics, Princeton University Press, Princeton, NJ, 1947; Asymptotic Methods in the Theory of Nonlinear Oscillations, Gordan and Breach, New York, 1961) unified method (J. Franklin Inst. 339 (2002) 239) is determined for obtaining the transient response of an nth order (n?2) differential equation with small non-linearities. The formula presented in (J. Franklin Inst. 339 (2002) 239) is a changed form of KBM method. For n=2,3,4, some previous formulas were found separately by several authors in terms of amplitude and phase variables; but the formula of Shamsul Alam, J. Franklin Inst. 339 (2002) 239) is derived in terms of some unusual variables instead of amplitudes and phases. The formula of Shamsul Alam, J. Franklin Inst. 339 (2002) 239) is a general form and used arbitrarily to obtain asymptotic solution for n=2,3,4,…. However, a solution obtained by formula Shamsul Alam, J. Franklin Inst. 339 (2002) 239) is transformed to a formal form replacing the unusual variables by amplitude and phase variables. In the present paper, the formula of Shamsul Alam, J. Franklin Inst. 339 (2002) 239) is itself transformed to a usual form (i.e. in terms of amplitude and phase variables). The later form of the formula is similar to most of the previous formulas found by several authors when n=2,3,4. This form of the formula is also generalized and it is easier than those obtained in all previous papers (extension) and identical to that initiated by original contributors (Introduction to Nonlinear Mechanics, Princeton University Press, Princeton, NJ, 1947; Asymptotic Methods in the Theory of Nonlinear Oscillations, Gordan and Breach, New York, 1961). 相似文献
15.
《Particuology》2015
There is increasing recognition that some nanomaterials may pose a risk to human health and the environment. Moreover, the industrial use of the novel engineered nanomaterials (ENMs) increases at a higher rate than data generation for hazard assessment; consequently, many of them remain untested. The large number of nanomaterials and their variants (e.g., different sizes and coatings) requiring testing and the ethical pressure towards nonanimal testing means that in a first instance, expensive animal bioassays are precluded, and the use of (quantitative) structure–activity relationships ((Q)SARs) models as an alternative source of (screening) hazard information should be explored. (Q)SAR modelling can be applied to contribute towards filling important knowledge gaps by making best use of existing data, prioritizing the physicochemical parameters driving toxicity, and providing practical solutions for the risk assessment problems caused by the diversity of ENMs. This paper covers the core components required for successful application of (Q)SAR methods to ENM toxicity prediction, summarizes the published nano-(Q)SAR studies, and outlines the challenges ahead for nano-(Q)SAR modelling. It provides a critical review of (1) the present availability of ENM characterization/toxicity data, (2) the characterization of nanostructures that meet the requirements for (Q)SAR analysis, (3) published nano-(Q)SAR studies and their limitations, (4) in silico tools for (Q)SAR screening of nanotoxicity, and (5) prospective directions for the development of nano-(Q)SAR models. 相似文献
16.
Three exact solutions are obtained for 2-D incompressible potential flows around two moving circles in three cases: (i) expansion
(or contraction) of themselves, (ii) approaching (or departing from) each other, (iii) moving perpendicularly to the line
connecting the centres in opposite directions. Meanwhile, another set of two exact solutions is obtained for 2-D incompressible
potential flows between two moving eccentric circles in two cases: moving parallely or perpendicularly to the line connecting
the centres. 相似文献
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通过试验, 本文就游离氧化铁在粘性土尤其是红土中富积含量的变化对土体工程地质性质产生的影响及其规律性做了初步研究。 相似文献
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在数学规划的领域里定义了互逆规划——各自目标函数与约束条件位置相互交换的一对规划. 接着指出,尽管互逆规划与对 偶规划在表面上似乎类似,但是二者存在 5 点不同:(1) 是否为同一个问题的不同;(2) 存在``对偶间隙'与否的不同;(3) 设计变量数目的不同;(4) 是否单目标与多目标问题的不同;(5) 问题合理与否的不同. 然后,基于互逆规划的定义,用以审视结 构拓扑优化模型,给出如下结果:(1) 从这个角度洞悉,在结构优化中,确实有不合理的模型一直被沿用着;(2) 找到了修正不 合理模型使之合理化的方法;(3) 对于给定体积下的柔顺度最小化 (MCVC) 模型,指出了其不合理的原因;(4) MCVC 模型实际是互 逆规划的 m 方,由此建立起其对应的 s 方, 即给出了多个柔顺度约束的体积最小化 (MVCC) 模型;(5)给出了MVCC模型中的结构 柔顺度约束的物理解释和算法,论证了 ICM (independent continuous and mapping) 方法以往关于全局化应力约束的概念和方法;(6)数值算例表明了 MCVC 与 MVCC 模型作为互逆规划的差异,且印证了 MVCC 模型的合理性.MCVC 模型在不同体积约束及多工况下不同的权系数时,得到最优拓扑不同;但 MVCC 模型在多工况柔顺度约束下可得到唯一的最优拓扑. 相似文献
19.
Residual Reynolds number effects in the established data for the velocity profile in turbulent boundary layers (and in pipe
or channel flows) are found to be remarkably large. We combine two eddy-viscosity models (with overlapping validity in the
inertial sublayer) and show (both analytically and numerically) that this enhancement (which involves a viscous correlation
length) arises from inner-outer sublayer interaction. 相似文献
20.
In this paper, we propose a method to minimize the Multi-User Interference (MUI) caused by Multiple Access (MA) in a Time
Hopping Ultra Wide Band (TH-UWB) system with Line-Of-Sight (LOS) multipath channel in a residential environment IEEE 802.15.4a.
We consider both synchronous and asynchronous cases. 相似文献