Airflow distortion at instrument sites on the ODEN during the ACSE project

Wind speed measurements obtained from anemometers mounted on ships are prone to systematic errors caused by the distortion of the air flow around the ship's hull and superstructure. This report describes the results of simulations of the air flow around the ODEN made using the computational fluid dynamics (CFD) software VECTIS. The airflow distortion at anemometer sites used during the ACSE project has been quantified at a wind speed of 7 ms-1 for a wide range of wind directions: every 10 degrees from bow on to 120 degrees off the bow, and an additional run was undertaken at 150 degrees off the bow. The anemometers used in this study were located in the bows of the ship. The vertical displacements of the airflow at the anemometer sites and at a location of an aerosol intake are included. Wind speed profiles above a motion-stabilised doppler lidar were also obtained. For bow-on flows the anemometers in the bows of the ship experienced relatively small flow distortion. At these sites the flow was decelerated by about 3% of the free stream wind speed. Over the full range of relative wind directions the flow to the METEK sonic is generally accelerated with the largest wind speed biases at flows directly over the beam. The vertical displacement of the airflow increases from around 3 m for flows directly over the bow, to around 6 m for flows over the ship's beam as the lockage of the airflow by the ship becomes greater. The vertical displacement at the aerosol intake location varied from 6m for flows directly over the bow, to around 16 m for flows over the ship's beam. The ship imposes a significant obstacle to the flow and forces a strong vertical velocity in the lowest few tens of meters above the lidar

Thermal performance of a solar oven with augmented sunlight concentration

This paper describes the thermal performance of a novel solar oven that incorporates a compact reflec-tive lens, or ring array, to augment sunlight concen-tration. Performance is reported in terms of the pos-itive effect of the ring array versus a non-concen-trating lid, maximum operating temperature, ther-mal efficiency, performance under partly cloudy skies, and the effects of incidence angle and track-ing. Use of the ring array lens improved thermal efficiency by 4% in the test range up to 100°C, while boosting the maximum operating temperature from 138°C to 196°C. Comparative tests conducted under clear sky conditions against two other com-mercial types showed that when tracked in the azimuth plane at near-normal incidence angles, the new design generated maximum cooking power of 300 W and boiled water at a rate 13% faster than the next best commercial oven tested. Augmented sunlight concentration sensitised the new design to higher angles of incidence and performance was negatively affected in the non-tracked state. Under non-ideal operating conditions, including partial shading by cloud, the oven outperformed both commercial units

Thermal performance of a solar oven with augmented sunlight concentration

This paper describes the thermal performance of a novel solar oven that incorporates a compact reflec-tive lens, or ring array, to augment sunlight concen-tration. Performance is reported in terms of the pos-itive effect of the ring array versus a non-concen-trating lid, maximum operating temperature, ther-mal efficiency, performance under partly cloudy skies, and the effects of incidence angle and track-ing. Use of the ring array lens improved thermal efficiency by 4% in the test range up to 100°C, while boosting the maximum operating temperature from 138°C to 196°C. Comparative tests conducted under clear sky conditions against two other com-mercial types showed that when tracked in the azimuth plane at near-normal incidence angles, the new design generated maximum cooking power of 300 W and boiled water at a rate 13% faster than the next best commercial oven tested. Augmented sunlight concentration sensitised the new design to higher angles of incidence and performance was negatively affected in the non-tracked state. Under non-ideal operating conditions, including partial shading by cloud, the oven outperformed both commercial units

Predicting precipitation kinetics during the annealing of additive manufactured inconel 625 components

The prediction of solidification microstructures associated with additive manufacture of metallic components is fundamental in the identification scanning strategies, process parameters and subsequent heat treatments for optimised component properties. Interactions between the powder particles and the laser heat source result in complex thermal fields in and around the metal melt pool, which will influence the spatial distribution of chemical species as well as solid-state precipitation reactions. This paper demonstrates that a multi-component, multi-phase precipitation model can successfully predict the observed precipitation kinetics in Inconel 625, capturing the anomalous precipitation behaviour exhibited in additively manufactured components. A computer coupling of phase diagrams and thermochemistry (CALPHAD)-based approach captures the impact of dendritic segregation of alloying elements upon precipitation behaviour. The model was successful in capturing the precipitation kinetics during annealing considering the Nb-rich and Nb-depleted regions that are formed during additive manufacturing

The High Magnetic Field Phase Diagram of a Quasi-One Dimensional Metal

We present a unique high magnetic field phase of the quasi-one dimensional organic conductor (TMTSF)$_2$ClO$_4$. This phase, termed "Q-ClO$_4$", is obtained by rapid thermal quenching to avoid ordering of the ClO$_4$ anion. The magnetic field dependent phase of Q-ClO$_4$ is distinctly different from that in the extensively studied annealed material. Q-ClO$_4$ exhibits a spin density wave (SDW) transition at $\approx$ 5 K which is strongly magnetic field dependent. This dependence is well described by the theoretical treatment of Bjelis and Maki. We show that Q-ClO$_4$ provides a new B-T phase diagram in the hierarchy of low-dimensional organic metals (one-dimensional towards two-dimensional), and describe the temperature dependence of the of the quantum oscillations observed in the SDW phase.Comment: 10 pages, 4 figures, preprin

Camera motion estimation through planar deformation determination

In this paper, we propose a global method for estimating the motion of a camera which films a static scene. Our approach is direct, fast and robust, and deals with adjacent frames of a sequence. It is based on a quadratic approximation of the deformation between two images, in the case of a scene with constant depth in the camera coordinate system. This condition is very restrictive but we show that provided translation and depth inverse variations are small enough, the error on optical flow involved by the approximation of depths by a constant is small. In this context, we propose a new model of camera motion, that allows to separate the image deformation in a similarity and a ``purely'' projective application, due to change of optical axis direction. This model leads to a quadratic approximation of image deformation that we estimate with an M-estimator; we can immediatly deduce camera motion parameters.Comment: 21 pages, version modifi\'ee accept\'e le 20 mars 200

Subject-specific, multiscale simulation of electrophysiology: a software pipeline for image-based models and application examples

Many simulation studies in biomedicine are based on a similar sequence of processing steps, starting from images and running through geometric model generation, assignment of tissue properties, numerical simulation and visualization of the results—a process known as image-based geometric modelling and simulation. We present an overview of software systems for implementing such a sequence both within highly integrated problem-solving environments and in the form of loosely integrated pipelines. Loose integration in this case indicates that individual programs function largely independently but communicate through files of a common format and support simple scripting, so as to automate multiple executions wherever possible. We then describe three specific applications of such pipelines to translational biomedical research in electrophysiology