EXPERIMENTAL INVESTIGATION OF RELATIVE PERMEABILITY UPSCALING FROM THE MICRO-SCALE TO THE MACRO-SCALE

Mobile phones and palm top computers are following trends of increased functionality and processor speed. To allow these trends to continue, compact cooling solutions are required. One potential solution is to introduce cooling fans. However, no fan currently exists which is small enough. This paper investigates the feasibility of producing a fan on the micro scale, which could be used. Theoretical analysis predicts a reduction in efficiency as fan size is reduced. A series of geometrically similar fans was produced so that the scaling could be experimentally investigated. These fans varied in size from the macro to the micro scale. The macro scale fan, which was used as a datum, is typical of those used to cool macro scale electronic systems. The authors developed techniques for the fabrication of the smaller scale fans. These included micro electro discharge machining. Methods for testing the performance of each of these fans were also developed. The pressure flow performance of each of the fans is measured, and confirms that as the micro scale is approached fan efficiency decreases. The observed decrease in efficiency is in agreement with theoretical prediction.

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2D-wavelet based micro and macro texture analysis for asphalt pavement under snow or ice condition

Journal of Infrastructure Preservation and Resilience ◽

10.1186/s43065-021-00029-y ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Feng Li ◽

Gulnigar Ablat ◽

Siqi Zhou ◽

Yixin Liu ◽

Yufeng Bi ◽

...

Keyword(s):

Wavelet Transform ◽

Asphalt Pavement ◽

Asphalt Mixture ◽

Micro Scale ◽

Braking System ◽

Macro Scale ◽

Texture Characteristics ◽

The Mean ◽

Resistance Performance

AbstractIn ice and snow weather, the surface texture characteristics of asphalt pavement change, which will significantly affect the skid resistance performance of asphalt pavement. In this study, five asphalt mixture types of AC-5, AC-13, AC-16, SMA-13, SMA-16 were prepared under three conditions of the original state, ice and snow. In this paper, a 2D-wavelet transform approach is proposed to characterize the micro and macro texture of pavement. The Normalized Energy (NE) is proposed to describe the pavement texture quantitatively. Compared with the mean texture depth (MTD), NE has the advantages of full coverage, full automation and wide analytical scale. The results show that snow increases the micro-scale texture because of its fluffiness, while the formation of the ice sheets on the surface reduces the micro-scale texture. The filling effect of snow and ice reduces the macro-scale texture of the pavement surface. In a follow-up study, the 2D-wavelet transform approach can be applied to improve the intelligent driving braking system, which can provide pavement texture information for the safe braking strategy of driverless vehicles.

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Spatial-Pattern-Induced Evolution of a Self-Replicating Loop Network

Artificial Life ◽

10.1162/artl.2006.12.4.461 ◽

2006 ◽

Vol 12 (4) ◽

pp. 461-485 ◽

Cited By ~ 8

Author(s):

Keisuke Suzuki ◽

Takashi Ikegami

Keyword(s):

Pattern Formation ◽

Spatial Pattern ◽

Spatial Patterns ◽

Spiral Structure ◽

Scale Interactions ◽

Micro Scale ◽

Macro Scale ◽

Loop Network ◽

Spatial Pattern Formation

We study a system of self-replicating loops in which interaction rules between individuals allow competition that leads to the formation of a hypercycle-like network. The main feature of the model is the multiple layers of interaction between loops, which lead to both global spatial patterns and local replication. The network of loops manifests itself as a spiral structure from which new kinds of self-replicating loops emerge at the boundaries between different species. In these regions, larger and more complex self-replicating loops live for longer periods of time, managing to self-replicate in spite of their slower replication. Of particular interest is how micro-scale interactions between replicators lead to macro-scale spatial pattern formation, and how these macro-scale patterns in turn perturb the micro-scale replication dynamics.

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Experimental study of the effects of wire EDM on the characteristics of ferritic steel, at a micro-scale on the contour cut surface

Metallurgical Research & Technology ◽

10.1051/metal/2018032 ◽

2018 ◽

Vol 115 (4) ◽

pp. 413

Author(s):

Nida Naveed

Keyword(s):

Residual Stress ◽

Stress Measurement ◽

Surface Characteristics ◽

Surface Damage ◽

Cutting Process ◽

Contour Method ◽

X Ray Diffraction ◽

Micro Scale ◽

Macro Scale ◽

Cut Surface

This study, on a micro-scale, of the WEDM cut surfaces of specimens to which the contour method of residual stress measurement is being applied provides detailed information about the effects of the cutting process on the surface quality. This is defined by a combination of several parameters: variation in surface contour profile, sub-surface damage and surface texture. Measurements were taken at the start, the middle and at the end of the cut. This study shows that during WEDM cutting, a thin layer, extending to a depth of a few micrometres below the surface of the cut, is transformed. This layer is known as the recast layer. Using controlled-depth etching and X-ray diffraction, it is shown that this induces an additional tensile residual stress, parallel to the plane of the cut surface. The WEDM cut surface and sub-surface characteristics are also shown to vary along the length of the cut. Moreover, these micro-scale changes were compared with macro-scale residual stress results and provides an indication of the point at which the changes occurred by cutting process can be significantly relative to the macro-scale residual stress in a specimen.

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On the Two-Scale Modelling of Elastohydrodynamic Lubrication in Tilted-Pad Bearings

Lubricants ◽

10.3390/lubricants6030078 ◽

2018 ◽

Vol 6 (3) ◽

pp. 78 ◽

Cited By ~ 3

Author(s):

Gregory de Boer ◽

Andreas Almqvist

Keyword(s):

Surface Topography ◽

Load Capacity ◽

Three Dimensional ◽

Elastohydrodynamic Lubrication ◽

Multiscale Methods ◽

Operating Conditions ◽

Real Surface ◽

Micro Scale ◽

Macro Scale ◽

Heterogeneous Multiscale

A two-scale method for modelling the Elastohydrodynamic Lubrication (EHL) of tilted-pad bearings is derived and a range of solutions are presented. The method is developed from previous publications and is based on the Heterogeneous Multiscale Methods (HMM). It facilitates, by means of homogenization, incorporating the effects of surface topography in the analysis of tilted-pad bearings. New to this article is the investigation of three-dimensional bearings, including the effects of both ideal and real surface topographies, micro-cavitation, and the metamodeling procedure used in coupling the problem scales. Solutions for smooth bearing surfaces, and under pure hydrodynamic operating conditions, obtained with the present two-scale EHL model, demonstrate equivalence to those obtained from well-established homogenization methods. Solutions obtained for elastohydrodynamic operating conditions, show a dependency of the solution to the pad thickness and load capacity of the bearing. More precisely, the response for the real surface topography was found to be stiffer in comparison to the ideal. Micro-scale results demonstrate periodicity of the flow and surface topography and this is consistent with the requirements of the HMM. The means of selecting micro-scale simulations based on intermediate macro-scale solutions, in the metamodeling approach, was developed for larger dimensionality and subsequent calibration. An analysis of the present metamodeling approach indicates improved performance in comparison to previous studies.

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