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[en] The vibrations induced in tube array by a transversal flow are of great practical interest because of their destruction effects especially on heat exchanger. Through turbulence can significantly excite the tube by itself, most intense vibrations are still caused by fluidelastic phenomena. The study described in this paper gives important information concerning the characteristics of these phenomena. A lot of bundlle mock-ups with various pitches have been tested in air. Large range parameter domains have been investigated (flow velocities, velocity profiles, natural frequencies and damping ratios of tubes, etc ...)
[fr]Les vibrations induites dans un faisceau tubulaire sous ecoulement transversal sont d'un grand interet pratique a cause de leurs effets destructeurs plus particulierement sur les echangeurs de chaleur. Quoique la turbulence puisse exciter de maniere importante le tube lui-meme, les vibrations les plus importantes sont encore produites par les phenomenes aero-hydroelastiques. Cette etude a permis de degager un certain nombre de phenomenes fondamentaux et de deboucher sur une methode d'estimation des vibrations des faisceaux de tubes. Un grand nombre de geometries de faisceaux ont ete testees et un domaine important de variations des parametres mecaniques a ete etudie (vitesse d'ecoulement, profils de vitesse, frequences de resonance et d'amortissement des tubes, etc ...)
[en] We develop a velocity-dependent one-scale model for the evolution of domain wall networks in flat expanding or collapsing homogeneous and isotropic universes with an arbitrary number of spatial dimensions, finding the corresponding scaling laws in frictionless and friction dominated regimes. We also determine the allowed range of values of the curvature parameter and the expansion exponent for which a linear scaling solution is possible in the frictionless regime.
[en] Korea Atomic Energy Research Institute (KAERI) is conducting development on the pyrorpcess mock-up facility (PMF) for full-scale pyroprocess inactive demonstration. A conceptual design of the PMF was carried out and design study for PMF is being carried out in this year. The PMF will incorporate an integrated engineering scale pyroprocessing system for an advanced nuclear fuel cycle technology. The conceptual requirements of the process equipments had been studied to build the basic data such as equipments size, heat load, weight, operation conditions, feed materials and product materials. The PMF cell size, capacity requirements of utility service such as HVAC, remote handling equipments, safety issues had been considered in conceptual design stages, too. The PMF shall be comply with safety requirements such as process and structure safety, radioactivity levels and contamination control, radiation monitoring for personnel protection, and fire prevention
[en] This paper proposes a conclusive scalable model for the complete actuation response for ionic polymer metal composites (IPMC). This single model is proven to be able to accurately predict the free displacement/velocity and force actuation at varying displacements, with up to 3 V inputs. An accurate dynamic relationship between the force and displacement has been established which can be used to predict the complete actuation response of the IPMC transducer. The model is accurate at large displacements and can also predict the response when interacting with external mechanical systems and loads. This model equips engineers with a useful design tool which enables simple mechanical design, simulation and optimization when integrating IPMC actuators into an application. The response of the IPMC is modelled in three stages: (i) a nonlinear equivalent electrical circuit to predict the current drawn, (ii) an electromechanical coupling term and (iii) a segmented mechanical beam model which includes an electrically induced torque for the polymer. Model parameters are obtained using the dynamic time response and results are presented demonstrating the correspondence between the model and experimental results over a large operating range. This newly developed model is a large step forward, aiding in the progression of IPMCs towards wide acceptance as replacements to traditional actuators
[en] Based on the spatial factor other than the temporal accumulation, the hidden tree model was built up to model scale-free networks. This paper further assumed that a node has multiple roles in different hidden trees, and explored the multi-role hidden tree model. The experimental results showed that multi-role hidden tree model can also produce scale-free networks. This conclusion indicates that the hidden tree model is robust with multiple roles
[en] This review article describes various multiscale approaches, development of which was spurred by the emergence of nanotechnology. The multiscale approaches are grouped into two main categories: information-passing and concurrent. In the concurrent multiscale methods both, the discrete and continuum scales are simultaneously resolved, whereas in the information-passing schemes, the discrete scale is modelled and its gross response is infused into the continuum scale. Most of the information-passing approaches provide sublinear computational complexity, (i.e., scales sublinearly with the cost of solving a fine scale problem), but the quantities of interest are limited to or defined only on the coarse scale. The issues of appropriate scale selection and uncertainty quantification are also reviewed
[en] We revisit the cosmological evolution of domain wall networks, taking advantage of recent improvements in computing power. We carry out high-resolution field theory simulations in two, three and four spatial dimensions to study the effects of dimensionality and damping on the evolution of the network. Our results are consistent with the expected scale-invariant evolution of the network, which suggests that previous hints of deviations from this behavior may have been due to the limited dynamical range of those simulations. We also use the results of very large (10243) simulations in three cosmological epochs to provide a calibration for the velocity-dependent one-scale model for domain walls: we numerically determine the two free model parameters to have the values cw=0.5±0.2 and kw=1.1±0.3.
[en] A general scaling model is defined which allows the extrapolation of small-scale collisional fragmentation experiment results, and existing collisional theories are considered within its framework. Scaling based exclusively upon the specific energy, Q, of the event (the ratio of projectile kinetic energy to the mass of the target body) is shown to hold when (1) the projectile and target material properties do not depend on size or time scales, and (2) the collision is governed by kinetic energy independently of impact velocity. Because neither of these conditions should hold, serious doubt is cast on the validity of Q's use as the sole scaling parameter. 43 refs
[en] In this paper we derive, directly from the Nambu-Goto action, the relevant components of the acceleration of cosmological featureless p-branes, extending previous analysis based on the field theory equations in the thin-brane limit. The component of the acceleration parallel to the velocity is at the core of the velocity-dependent one-scale model for the evolution of p-brane networks. We use this model to show that, in a decelerating expanding universe in which the p-branes are relevant cosmologically, interactions cannot lead to frustration, except for fine-tuned nonrelativistic networks with a dimensionless curvature parameter k<<1. We discuss the implications of our findings for the cosmological evolution of p-brane networks.
[en] We develop a velocity-dependent one-scale model describing p-brane dynamics in flat homogeneous and isotropic backgrounds in a unified framework. We find the corresponding scaling laws in frictionless and friction-dominated regimes considering both expanding and collapsing phases.