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A pragmatical physics-based model for predicting ladle lifetime
Get PDFIn this paper we develop a physics-based model for lining erosion in steel ladles. The model predicts the temperature evolution in the liquid slag, steel, refractory bricks, and outer steel shell of the ladle. The flow of slag and steel is due to forced convection induced by inert gas injection, vacuum treatment (extreme bubble expansion), natural convection, and waves caused by the gas stirring. The lining erosion takes place by dissolution of refractory elements into the steel or slag. The mass and heat transfer coefficients inside the ladle during gas stirring are modelled based on wall functions which take the distribution of wall shear velocities as a critical input. The wall shear velocities are obtained from computational fluid dynamics (CFD) simulations for a sample of scenarios, spanning out the operational space, and a model is developed using curve fitting. The model is capable of reproducing both thermal and erosion evolution well. Deviations between model predictions and industrial data are discussed. The model is fast and has been tested successfully in a 'semi-online' application. The model source code is available to the public at [https://github.com/SINTEF/refractorywear].publishedVersio
Edge-based Data Profiling and Repair as a Service for IoT
Get PDFWith the proliferation of IoT devices and the consequent exponential growth in data generation, ensuring data quality has become a critical challenge in IoT applications. Erroneous data can significantly impact the reliability and effectiveness of decision-making processes and downstream analytics. Leveraging the computational abilities of edge devices enables data profiling and repair tasks at the edge, allowing for immediate remediation of erroneous data within the data stream and improved scalability through distributed repair across multiple edge devices. Cloud-based data profiling and repair methods have been extensively researched, but limited computational resources constrain their applicability at edge/fog devices. To overcome this limitation and enhance generalizability, Machine Learning (ML) offers a promising solution, allowing sensor substitution, missing value prediction, and corrupt data replacement. ML-based data repair techniques can be flexibly deployed at the edge using containerized repair services for real-time data repair. In this paper, we propose and assess EDPRaaS (Edge-based Data Profiling and Repair as a Service), a novel approach designed for efficient data quality profiling and repair in IoT environments. EDPRaaS incorporates an ML-based data repair component, enabling real-time data repair at the edge. It leverages pandas profiling and Great Expectations tools for data profiling, providing comprehensive insights into the dataset and detecting data quality issues.publishedVersio
Conduction and Electric Fields in Dielectric Liquids in Needle-to-Plane Gaps
Get PDFThis paper describes measurements of conduction currents in both neat and commercial insulating liquids. Conduction in thermodynamic equilibrium has been measured by applying a low ac voltage in a uniform field. High-field pre-discharge currents have been measured in a needle-to-plane configuration stressed with respectively high voltage ac and steep step high voltage pulses. There was significantly increased conduction for high field compared to low field conditions. Notably, measurements at high fields in needle-plane configurations indicate space charge limitation of currents with polarity differences. The high field conduction exhibited considerable variation across different liquids. At high applied fields, electronic processes are probably governing the charge formation. Simulations indicate that space charges may reduce the local field in front of needle tips at time scales relevant for propagating streamers.Conduction and Electric Fields in Dielectric Liquids in Needle-to-Plane GapsacceptedVersio
The role of electrical current mode in calcium carbonate deposition on conductive carbon nanofiber–epoxy coating
Get PDFCalcium carbonate is one of the most common scaling minerals. In this paper we have used different electrical current modes (direct current [DC], pulsed DC, and alternating current [AC]) to control the amount, morphology, and distribution of calcium carbonate deposit on electroconductive epoxy/carbon nanofiber (CNF) coating. The effect of different current modes on surface scaling was visualized using scanning electron microscopy. It has been shown that both AC and DC anodic polarization limited scale deposition on epoxy/CNF coated surfaces, although the mechanisms of scale inhibition during AC and DC polarization were different. DC polarization of the coating at +2 V resulted in the smallest scale buildup without leading to coating degradation, while DC polarization at potentials as high as +5 V caused the coating to degrade. Interestingly, application of pulsed DC with high pulse frequency (50 Hz) inhibited the degradation. The type of current applied affected also the morphology of the precipitate at the cathode. The results presented in this work show, for the first time, how different modes of electrical current applied to electroconductive composite coatings can be used to control the morphology and distribution of calcium carbonate scale, and how the organic coating degradation at high polarization potentials can be avoided.publishedVersio
The role of parent austenite grain size on the variant selection and intervariant boundary network in a lath martensitic steel
Get PDFThis study investigated the influence of parent austenite grain refinement on the intervariant boundary network (population and connectivity) in a lath martensitic steel. Parent austenite grain refinement revealed a progressive reduction in the fraction of the 60° misorientation boundaries in martensite, which was linked to a decrease in the 60° / [110] intervariant boundary population. The phenomenological theory of martensite crystallography demonstrated that the variant selection mechanism altered from the 3-variant clustering (V1V3V5) in the coarse parent austenite towards the 4-variant clustering (V1V2V3V4) in the fine parent austenite grain, due to the change in the lattice parameter of the parent and daughter phase in which the martensite transformation occurs, as measured using in situ neutron diffraction. The change in the variant clustering arrangement with the parent austenite grain refinement led to a progressive promotion of 60° / [111] and 10.5° / [011] intervariant boundaries at the expense of 60° / [110] martensite intervariant boundaries. Subsequently, the connectivity of low energy {110} tilt intervariant boundaries gradually increased through the refinement of parent austenite grain size, eventually reducing the high energy {110} twist boundary connectivity. This change improved the impact toughness of martensite produced from the fine-grained austenite as the weak connectivity of high energy boundaries delays the coalescence of voids, promoting ductile fracture.publishedVersio
Equal, normalized and included? Experiences with buying your own home for the mentally disabled
Get PDFThis project examines the practices of six Norwegian municipalities, which, in a variety of ways, are trying to enable mentally disabled residents to build or buy their own homes. The survey has confirmed some previous findings: The financing model operated by the Norwegian State Housing Bank makes it possible for many mentally disabled people to purchase homes on the ordinary housing market. However, even though private developers are, without exception, friendly, this appears to be a complicated and resourcedemanding process. The cases demonstrate how municipalities can enable better processes in a variety of ways. Leaving home can be a major upheaval both for young mentally disabled people and their parents, entailing changes in the young person’s responsibilities, personal economy, and sense of independence. The overall objective is to achieve inclusivity. Some of the homes are quite ordinary and are located among other similar homes, but our findings indicate that to date, residents experience little or no positive interaction with their other neighbors. Natural meeting places and communal areas dedicated to entire neighborhoods are rare in new housing projects. If we are to meet the objectives of inclusivity and participation, we must expand our focus and not only look at the homes but also at the neighborhood in which the residents will be included.publishedVersio
NEMECYS: Addressing Challenges to Building Security Into Connected Medical Devices
Get PDFThe European health care system is moving toward personalised, distributed, and home-based services. This is made possible via new and improved connected medical devices (CMDs), and will benefit health care providers in terms of reduced cost and improved service. Patients will see improved quality of life in terms of reduced travel time and reduced stress via treatment at home or where they want it. However, for these benefits to be fully realised, the cybersecurity of CMDs needs to be ensured. This paper presents a brief survey of challenges to building security into CMDs, and introduces NEMECYS, an EU-funded project which will help practitioners to (a) comply with Medical Device (MD) regulations; (b) be able to apply proportionate MD cybersecurity, and (c) build in cybersecurity by design for both MDs and the connected scenarios they operate in.publishedVersio
Thermodynamically consistent modeling of gas flow and adsorption in porous media
Get PDFIn modeling of gas flow through porous media width adsorption, the thermodynamic properties of the adsorbed phase are usually approximated by those of the bulk liquid. Using non-isothermal, gaseous transport of moist air through a porous insulation material as example, we show that this leads to violation of the second law of thermodynamics and a negative entropy production. To resolve this violation, we use information about the adsorption and thermodynamic properties of bulk fluids to derive consistent thermodynamic properties of the adsorbed phase, such as the chemical potential, enthalpy and entropy. The resulting chemical potential of the adsorbed phase is a starting point for rate-based models for adsorption based on non-equilibrium thermodynamics. Incorporating the consistent thermodynamic description into the energy, entropy and momentum balances restores agreement with the second law of thermodynamics. We show that the temperature evolution in the porous medium from the consistent description differs from the standard formulation only if the adsorption depends explicitly on temperature. This highlights the importance of characterizing the temperature dependence of the adsorption with experiments or molecular simulations for accurate non-isothermal modeling of porous media.publishedVersio