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The mechanical properties of composite structures depend on the preform impregnation and a successful impregnation can be achieved using the permeability relation in the case of an infusion process. The objective of this study is to develop an analytical model to predict the permeability K of carbon and glass fabrics through hybrid laminate using different stacking sequence, applying an average-permeability model. Preforms permeabilities were evaluated through tortuosity and void-volume fraction. The model allows the analysis of different stacking sequence combinations (interleaved and in block), measuring the contribution of each material type. As a result, hybrid average-permeability model was validated through experimental permeability tests, dimensionless permeability, and tortuosity results, besides enabling predictions of the flow front behavior with, INTRODUCTION Resin transfer molding (RTM) is an attractive manufacturing process for composites. It provides many advantages for industrial processes: relatively low costs, reduced processing time, and ability to produce complex [...]

Previous methods for calculating power loss in litz-wire windings usually assume very fine strands such that the diameter of strands is much smaller than skin depth. In this paper, we present a method for calculating proximity-effect loss in litz-wire windings, using an equivalent complex permeability model of the winding. We first obtain a permeability model for litz-wire bundles, then use homogenization techniques to find the effective permeability of a winding. Permeability models are provided for bundles consisting of either rectangularly packed or hexagonally packed strands. The permeability model enables high-accuracy proximity-effect loss analysis and field analysis for litz-wire windings at high frequencies. It can also be used to find the leakage inductances in magnetic components. Index Terms--Complex permeability, eddy currents, inductors, litz wire, magnetic devices, power conversion, power transformers, proximity effect, skin effect.

The theory of consolidation has its origin in the effective stress concept developed by Terzaghi, which was derived based on several assumptions to arrive at a simplified theory. Considering the limitations involved in Terzaghi's theory, various attempts are being made by researchers to idealize the problem to represent various field situations. This paper presents a more generalized theory for vertical consolidation of a compressible medium of finite thickness, subjected to suddenly applied loading, assuming small strain and no creep. The theory assumes small deformations, and thus the settlement is governed by vertical strains generated by an increment of loading, neglecting the effect of self-weight of the soil. The analytical solution presented here takes into account e-log K and e-log [sigma]' linear responses under instantaneous loading. With [C.sub.c] as the slope of the e-log [sigma]' line and M the slope of the e-log K line, a parameter [C.sub.c]/M is identified which is found to govern the rate of consolidation. In this paper, an analytical closed form solution is obtained for vertical consolidation considering the variation in the compressibility and permeability. CE Database subject headings: Consolidation; Clays; Permeability; Compressibility; Strain.

Effective medium theory (EMT) was employed to estimate permeability of fine-grained estuarine sediments. X-radiographs were taken of sediment cores collected in the field and from laboratory aquaria, designed to mimic the benthic environment of an estuary. Image analysis of two-dimensional X rays provided values of pore parameters required by the EMT model, which include pore body and throat radii, pore throat length, porosity, and the interconnectivity of pores. Values of these parameters were used to quantitatively calculate permeability based upon Darcy's law. The EMT model with an arithmetic mean for averaging pore parameters predicted permeability 1 order of magnitude higher than measured values. The harmonic mean for averaging pore parameters in the EMT model provided estimates of permeability similar to measured values. DOI: 10.1061/(ASCE)0733-9429(2002)128:11(1002) CE Database keywords: Darcy's law; Estuaries; Imaging techniques; Marine clays; Numerical models; Permeability; Permeameters; Sediment.

The material parameters to express the degree of discontinuity of hydraulic gradient in the developed model (Part I) are calibrated based on the sensible analysis of the experimental results, and then the applicability of the calibrated parameters is discussed. As a result, the material parameters are calibrated by the sensible analysis, and then its relevance can be confirmed by another experiment. Moreover, it can be seen that the normalized permeability of concrete as a nonhomogeneous material by the initial permeability (homogeneous material) can be regressed with three straight lines in the crack width axis with the logarithm. Then the intersection point at the crack width axis shows the critical width at which leakage will not occur. The intersection point at the last two straight lines shows the critical Reynolds number at which flow becomes laminar to turbulent according to the experimental result.

A mathematical model for water migration in concrete that changes from a homogeneous to a nonhomogeneous material due to its loading history is developed in detail. In the proposed model, concrete is assumed to be composed of aggregate, cement paste, water, a crack band, and an interfacial crack between the aggregate and cement paste. The discontinuities for displacement and hydraulic gradient on cracks are considered on the microlevel. Then the governing equation for water migration in concrete as a homogeneous and a nonhomogeneous material is developed by coupling the mass conservation law and the force equilibrium. Therefore, it is possible to apply the developed model not only to cement-based material but also to porous permeable material like soil material and rock. However, the applicability of the developed model must be confirmed by comparing the experimental results.

Author(s): Nicolas de Prost [sup.1], Georges Saumon [sup.2], Didier Dreyfuss [sup.2] [sup.3] [sup.4] Author Affiliations: (1) grid.50550.35, 0000000121754109, Service de Réanimation Médicale, Hôpital Henri Mondor, Assistance Publique-Hôpitaux de Paris, , [...]

The permeability of cyanobacterial gas vesicles was determined by measuring the gradient of oxygen through a suspension of Microcystis sp. gas vesicles. Using oxygen diffusivity through water as a reference point, the diffusivity through gas vesicles occupying 35% of the suspension volume was calculated to be 0.81 that of diffusivity through water. The gas permeability coefficient was shown to be 32 mm per second, while the rate consant for the gas vesicle to fill was 2.4 x 10(super -6) per second. It was concluded that randomly oriented gas vesicles cannot provide a gas-conducting channel.