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

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 (≤3μm lateral dimension) were less significant in determining water vapour ingress. In contrast, larger defects (≥3 μm 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

Modelling water vapor permeability through atomic layer deposition coated photovoltaic barrier defects

Transparent barrier films such as Al2O3 used for prevention of oxygen and/or water vapour permeation are the subject of increasing research interest when used for the encapsulation of flexible photovoltaic modules. However, the existence of micro-scale defects in the barrier surface topography has been shown to have the potential to facilitate water vapour ingress, thereby reducing cell efficiency and causing internal electrical shorts. Previous work has shown that small defects (≤ 3 μm lateral dimension) were less significant in determining water vapour ingress. In contrast, larger defects (≥ 3 μm lateral dimension) seem to be more detrimental to the barrier functionality. Experimental results based on surface topography segmentation analysis and a model presented in this paper, will be used to test the hypothesis that the major contributing defects to water vapour transmission rate are small numbers of large defects. The model highlighted in this study has the potential to be used for gaining a better understanding of photovoltaic module efficiency and performance

Best software test & quality assurance practices in the project life-cycle. An approach to the creation of a process for improved test & quality assurance practices in the project life-cycle of an SME

The cost of software problems or errors is a significant problem to global industry, not only to the producers of the software but also to their customers and end users of the software. There is a cost associated with the lack of quality of software to companies who purchase a software product and also to the companies who produce the same piece of software. The task of improving quality on a limited cost base is a difficult one. The foundation of this thesis lies with the difficult task of evaluating software from its inception through its development until its testing and subsequent release. The focus of this thesis is on the improvement of the testing & quality assurance task in an Irish SME company with software quality problems but with a limited budget. Testing practices and quality assurance methods are outlined in the thesis explaining what was used during the software quality improvement process in the company. Projects conducted in the company are used for the research in the thesis. Following the quality improvement process in the company a framework for improving software quality was produced and subsequently used and evaluated in another company

A Probabilistic Fatigue Strength Assessment in AlSi-Cast Material by a Layer-Based Approach

An advanced lightweight design in cast aluminium alloys features complexly shaped geometries with strongly varying local casting process conditions. This affects the local microstructure in terms of porosity grade and secondary dendrite arm spacing distribution. Moreover, complex service loads imply changing local load stress vectors within these components, evoking a wide range of highly stressed volumes within different microstructural properties per load sequence. To superimpose the effects of bulk and surface fatigue strength in relation to the operating load sequence for the aluminium alloy EN AC 46200, a layer-based fatigue assessment concept is applied in this paper considering a non-homogeneous distribution of defects within the investigated samples. The bulk fatigue property is now obtained by a probabilistic evaluation of computed tomography results per investigated layer. Moreover, the effect of clustering defects of computed tomography is studied according to recommendations from the literature, leading to a significant impact in sponge-like porosity layers. The highly stressed volume fatigue model is applied to computed tomography results. The validation procedure leads to a scattering of mean fatigue life from −2.6% to 12.9% for the investigated layers, inheriting strongly varying local casting process conditions

Code decay triangulation using metrics, experts' opinion and defect counts

This extended abstract summarises the findings of a case study in which three differents types of data (metrics, experts' opinion and defect counts) were used to evaluate the presence of code decay

Beethoven's Nationality

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In situ assessment and minimization of nonlinear propagation effects for femtosecond-laser waveguide writing in dielectrics

The effect of nonlinear propagation on the shape of the focal volume has been assessed by in situ plasma emission imaging during the subsurface processing of a commercial phosphate glass. The sample was processed with an elliptically shaped femtosecond-laser beam at 1 kHz repetition rate and scanned transversely with respect to the writing beam axis. As a consequence, optimal conditions for minimizing undesirable nonlinear propagation effects during the production of optical waveguides by direct laser writing have been determined. Under these conditions, it is possible to induce structural transformations and still preserve the focal volume shape associated with the linear propagation regime. While at low pulse energy a single scan laser-written structure does not support a guided mode, the use of multiple scans with minimized nonlinear propagation effects enables the production of optical waveguides. The latter show a significantly improved performance in terms of the refractive index change and propagation losses when compared to single scan waveguides. © 2010 Optical Society of America.This work was partially supported by the University of Zaragoza under Project 223/88 and by the Spanish Ministry of Science and Innovation under TEC2008-01183 project. A. Ruiz de la Cruz and W. Gawelda acknowledge their I3P-CSIC postdoctoral contracts (co-funded by the European Social Fund). D. Puerto and A. Ferrer acknowledge their grants under Projects TEC 2005-00074 and TEC 2006-04538.Peer Reviewe

Validation and Verification of LADEE Models and Software

The Lunar Atmosphere Dust Environment Explorer (LADEE) mission will orbit the moon in order to measure the density, composition and time variability of the lunar dust environment. The ground-side and onboard flight software for the mission is being developed using a Model-Based Software methodology. In this technique, models of the spacecraft and flight software are developed in a graphical dynamics modeling package. Flight Software requirements are prototyped and refined using the simulated models. After the model is shown to work as desired in this simulation framework, C-code software is automatically generated from the models. The generated software is then tested in real time Processor-in-the-Loop and Hardware-in-the-Loop test beds. Travelling Road Show test beds were used for early integration tests with payloads and other subsystems. Traditional techniques for verifying computational sciences models are used to characterize the spacecraft simulation. A lightweight set of formal methods analysis, static analysis, formal inspection and code coverage analyses are utilized to further reduce defects in the onboard flight software artifacts. These techniques are applied early and often in the development process, iteratively increasing the capabilities of the software and the fidelity of the vehicle models and test beds