6,884 research outputs found

    12th Commencement Address

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    A correlational study of areal surface texture parameters on some typical machined surfaces

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    A number of areal surface texture parameters have been adopted by standards bodies, namely ISO 25178-2, in which forty-one parameters within six groups are defined. The selection of the suitable areal parameters becomes an issue for a designer. The study of correlation among parameters is one of the ways to find the most suitable parameters for a specification. This paper presents a Spearmanā€™s correlation study of areal surface texture parameters on some typical machined surfaces. Sixty surfaces, produced by nineteen machining methods, have been assessed by the use of an optical instrument; the operators adhered to ISO 25178-3; and parameters defined by ISO 25178-2. The correlation results are classified by using five correlation levels. It details the correlations between different groups of parameters, together with the correlation of parameters within the same group. The results are presented in Spearmanā€™s rank correlation coefficient matrix and charts. A three-layer parameters tree is then proposed to help engineer in the selection of parameters

    Functional Modelling of Water Vapour Transmission through Surface Defects Using Surface Segmentation Analysis

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    Flexible photovoltaic films have been recently shown to have efficiencies comparable to those of solid Si based photovoltaics. Flexible PV films have significant advantages in terms of ease of manufacture by roll-to-roll (R2R) techniques and in easy building integration. A significant challenge is the protection of the flexible solar cells from water vapour ingress, which seriously reduces cell life and efficiency. Transparent barrier films are a possible solution to addressing the water vapour transmission rate (WVTR) challenge. Consequently thin barrier films such as those made from Al2O3 are the subject of increasing research interest when used for the encapsulation of flexible PV modules. The film can be produced by several thin film deposition processes such as atomic layer deposition (ALD). However, micro-scale defects in the barrier film such as pinholes and particulate debris have been shown to have serious consequences in terms of WVTR. Our previous research has empirically shown that small defects (ā‰¤3Ī¼m lateral dimension) were less significant in determining water vapour ingress. In contrast, larger defects (ā‰„3 Ī¼m lateral dimension) have been shown to have a greater effect on the barrier functionality. The present paper illustrates the use of surface segmentation techniques to efficiently extract defect data from measured surface topography of barrier film sheets. Experimental results are presented where the defect information is correlated with the WVTR tests. A model is then presented to test the hypothesis that the major contributing defects to water vapour transmission rate (WVTR) are small numbers of large defects. The model presented in the paper shows excellent correlation with experimental results and provides a theoretical basis for the development of in process surface measurement for thin film R2R manufacture

    Nano scale Characterisation of Photovoltaic Ultra Barrier Films

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    This paper reports on the recent work carried out as part of the EU funded NanoMend project. The project seeks to develop integrated process inspection, cleaning, repair and control systems for nano-scale thin films on large area substrates

    Land, Income, Mobility and Housing: The Case of Metro Manila

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    Housing developments have been hampered by exorbitantly priced land specifically in the cities. The 1991 housing survey show that Metro Manila households pay the same rate as other households from developing countries. This article reviews the Philippine urban policies and examines the expenditures of owners and renters on shelters. It also investigates the factors on residential mobility among the sample households.urban management, tariff structure, housing program, land management, rent and fee

    The topographic development and areal parametric characterization of a stratified surface polished by mass finishing

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    Mass finishing is amongst the most widely used finishing processes in modern manufacturing, in applications from deburring to edge radiusing and polishing. Processing objectives are varied, ranging from the cosmetic to the functionally critical. One such critical application is the hydraulically smooth polishing of aero engine component gas-washed surfaces. In this, and many other applications the drive to improve process control and finish tolerance is ever present. Considering its widespread use mass finishing has seen limited research activity, particularly with respect to surface characterization. The objectives of the current paper are to; characterise the mass finished stratified surface and its development process using areal surface parameters, provide guidance on the optimal parameters and sampling method to characterise this surface type for a given application, and detail the spatial variation in surface topography due to coupon edge shadowing. Blasted and peened square plate coupons in titanium alloy are wet (vibro) mass finished iteratively with increasing duration. Measurement fields are precisely relocated between iterations by fixturing and an image superimposition alignment technique. Surface topography development is detailed with ā€˜log of process durationā€™ plots of the ā€˜areal parameters for scale-limited stratified functional surfacesā€™, (the Sk family). Characteristic features of the Smr2 plot are seen to map out the processing of peak, core and dale regions in turn. These surface process regions also become apparent in the ā€˜log of process durationā€™ plot for Sq, where lower core and dale regions are well modelled by logarithmic functions. Surface finish (Ra or Sa) with mass finishing duration is currently predicted with an exponential model. This model is shown to be limited for the current surface type at a critical range of surface finishes. Statistical analysis provides a group of areal parameters including; Vvc, Sq, and Sdq, showing optimal discrimination for a specific range of surface finish outcomes. As a consequence of edge shadowing surface segregation is suggested for characterization purposes

    Dynamic reservoir-condition microtomography of reactive transport in complex carbonates: effect of initial pore structure and initial brine pH

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    We study the impact of brine acidity and initial pore structure on the dynamics of fluid/solid reaction at high PĆ©clet numbers and low Damkƶhler numbers. A laboratory Ī¼-CT scanner was used to image the dissolution of Ketton, Estaillades, and Portland limestones in the presence of CO2-acidified brine at reservoir conditions (10 MPa and 50Ā°C) at two injected acid strengths for a period of 4 hours. Each sample was scanned between 6 and 10 times at āˆ¼4 Ī¼m resolution and multiple effluent samples were extracted. The images were used as inputs into flow simulations, and analysed for dynamic changes in porosity, permeability, and reaction rate. Additionally, the effluent samples were used to verify the image-measured porosity changes. We find that initial brine acidity and pore structure determine the type of dissolution. Dissolution is either uniform where the porosity increases evenly both spatially and temporally, or occurs as channelling where the porosity increase is concentrated in preferential flow paths. Ketton, which has a relatively homogeneous pore structure, dissolved uniformly at pH = 3.6 but showed more channelized flow at pH = 3.1. In Estaillades and Portland, increasingly complex carbonates, channelized flow was observed at both acidities with the channel forming faster at lower pH. It was found that the effluent pH, which is higher than that injected, is a reasonably good indicator of effective reaction rate during uniform dissolution, but a poor indicator during channelling. The overall effective reaction rate was up to 18 times lower than the batch reaction rate measured on a flat surface at the effluent pH, with the lowest reaction rates in the samples with the most channelized flow, confirming that transport limitations are the dominant mechanism in determining reaction dynamics at the fluid/solid boundary

    Flexible shape extraction for micro/nano scale structured surfaces.

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    Surface feature is the one of the most important factors affecting the functionality and reliability of micro scale patterned surfaces. For micro scale patterned surface characterisation, itā€™s important to extract the surface feature effectively and accurately. The active contours, known as ā€œsnakesā€, have been successfully used to segment, match and track the objects of interest. The active contours have been applied to facial boundary detection, medical image processing, motion correction, etc. In this paper, surface feature extraction techniques based on active contours have been investigated. Parametric active contour models and geometric active contour models have been presented. Also, a group of examples has been selected here to demonstrate the feasibility and applicability of the surface pattern extraction techniques based on active contours. At last, experimental results will be given and discussed
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