Experimental study on inertial hydrodynamic behaviors of a complex remotely operated vehicle

This paper presents an experimental study on inertial hydrodynamic behaviors of an open-frame remotely operated vehicle (ROV) that has a complex open-frame hull but a large capacity to hold more instruments on board than those of other ROVs. A 1:4 scaled model was tested by a vertical planar motion mechanism in a circulating water channel of Harbin Engineering University. The inertial coefficients, which can be used for the simulation of motions and therefore for the maneuverability of the ROV, were calculated. Particular attention was paid to discuss the properties of the cross-inertial coefficients, which are related to the inertial forces/moments induced by the motion in other directions

Flow interaction between a streamwise oscillating cylinder and a downstream stationary cylinder

In this paper, we present some experimental results about the physical effects of a cylinder’s streamwise oscillation motion on a downstream one in a tandem arrangement. The upstream cylinder undergoes a controlled simple harmonic oscillation at amplitudes A/d = 0.2–0.8, where d is the cylinder diameter, and the frequency ratio of fe/fsfe/fs = 0–3.0, where fefe is the cylinder oscillation frequency and fsfs is the natural frequency of vortex shedding from a single stationary cylinder. Under these conditions, the vortex shedding is locked to the controlled oscillation motion. Flow visualisation using the planar laser-induced fluorescence and qualitative measurements using hot-wire anemometry reveal three distinct flow regimes behind the downstream cylinder. For fe/fs>(fe/fs)cfe/fs>(fe/fs)c , where (fe/fs)c(fe/fs)c is a critical frequency ratio which depends on A/d and Reynolds number Re, a so-called SA-mode occurs. The upstream oscillating cylinder generates binary vortices symmetrically arranged about the centreline, each containing a pair of counter-rotating vortices, and the downstream cylinder sheds vortices alternately at 0.5fe0.5fe . For 0.7–1.

Application of the Fisher-Rao metric to ellipse detection

The parameter space for the ellipses in a two dimensional image is a five dimensional manifold, where each point of the manifold corresponds to an ellipse in the image. The parameter space becomes a Riemannian manifold under a Fisher-Rao metric, which is derived from a Gaussian model for the blurring of ellipses in the image. Two points in the parameter space are close together under the Fisher-Rao metric if the corresponding ellipses are close together in the image. The Fisher-Rao metric is accurately approximated by a simpler metric under the assumption that the blurring is small compared with the sizes of the ellipses under consideration. It is shown that the parameter space for the ellipses in the image has a finite volume under the approximation to the Fisher-Rao metric. As a consequence the parameter space can be replaced, for the purpose of ellipse detection, by a finite set of points sampled from it. An efficient algorithm for sampling the parameter space is described. The algorithm uses the fact that the approximating metric is flat, and therefore locally Euclidean, on each three dimensional family of ellipses with a fixed orientation and a fixed eccentricity. Once the sample points have been obtained, ellipses are detected in a given image by checking each sample point in turn to see if the corresponding ellipse is supported by the nearby image pixel values. The resulting algorithm for ellipse detection is implemented. A multiresolution version of the algorithm is also implemented. The experimental results suggest that ellipses can be reliably detected in a given low resolution image and that the number of false detections can be reduced using the multiresolution algorithm

The Effect of Aggregate Particle Size on Formation of Geopolymeric Gel

Due to enhanced mechanical and chemical properties, geopolymeric materials are a potential alternative to ordinary Portland cement and high-strength cement for the construction industry. The effects of aggregate particle size on the formation and the mechanical properties of geopolymeric materials are investigated in the current work. The addition of soluble silicates to the alkaline activator was found to increase the dissolution of silicate ions from the aggregate into the geopolymer binder phase. The results indicate that the surface area of aggregate influences the strength development of a geopolymer

Numerical investigations of convective phenomena of oil impingement on end-windings

A novel experimental rig for analysing intensive liquid cooling of highly power-dense electrical machine components has been developed. Coupled fluid flow and heat transfer has been modelled, using computational fluid dynamics (CFD), to inform the design of a purpose-built enclosure for optimising the design of submerged oil jet cooling approaches for electrical machine stators. The detailed modelling methodology presented in this work demonstrates the value in utilising CFD as a design tool for oil-cooled electrical machines. The predicted performance of the final test enclosure design is presented, as well as examples of the sensitivity studies which helped to develop the design. The sensitivity of jet flow on resulting heat transfer coefficients has been calculated, whilst ensuring parasitic pressure losses are minimised. The CFD modelling will be retrospectively validated using experimental measurements from the test enclosure

Equivalence of the Parke-Taylor and the Fadin-Kuraev-Lipatov amplitudes in the high-energy limit

We give a unified description of tree-level multigluon amplitudes in the high-energy limit. We represent the Parke-Taylor amplitudes and the Fadin-Kuraev-Lipatov amplitudes in terms of color configurations that are ordered in rapidity on a two-sided plot. We show that for the helicity configurations they have in common the Parke-Taylor amplitudes and the Fadin-Kuraev-Lipatov amplitudes coincide.Comment: LaTeX, 24 pages (including 4 tar-compressed uuencoded figures

Thermal management of a high speed permanent magnet machine for an aeroengine

The paper describes the mechanical and thermal design of a high speed, high power density synchronous permanent magnet machine for an aero engine starter generator system with a power rating of 150 kW and maximum speed of 32,000 rpm. As both mechanical and thermal aspects have a direct impact on machine overall performance and weight reduction, a critical design optimisation was carried out. Intensive cooling is guaranteed by direct liquid oil-cooling of stationary components; a stator sleeve is also introduced into the airgap to prevent excessive windage. Thermal investigations were carried out by the means of Computational Fluid Dynamics (CFD) and Lumped Parameter Thermal Network (LPTN) analyses. Experimental validation also allowed the identification of most critical machine temperatures and the validation of the models developed. Finite Element Analysis(FEA) is used for the static structural analyses of the statorsleeve

Spillover of a tobamovirus from the Australian indigenous flora to invasive weeds

The tobamovirus yellow tailflower mild mottle virus (YTMMV) was previously reported in wild plants of Anthocercis species (family Solanaceae) and other solanaceous indigenous species growing in natural habitats in Western Australia. Here, we undertook a survey of two introduced solanaceous weeds, namely Solanum nigrum (black nightshade) and Physalis peruviana (cape gooseberry) in the Perth metropolitan area and surrounds to determine if YTMMV has spread naturally to these species. At a remnant natural bushland site where both solanaceous weeds and indigenous Anthocercis hosts grew adjacent to one another, a proportion of S. nigrum and P. peruviana plants were asymptomatically-infected with YTMMV, confirming spillover had occurred. Populations of S. nigrum also grow as weeds in parts of the city isolated from remnant bushland and indigenous sources of YTMMV, and some of these populations were also infected with YTMMV. Fruit was harvested from virus-infected wild S. nigrum plants and the seed germinated under controlled conditions. Up to 80% of resultant seedlings derived from infected parent plants were infected with YTMMV, confirming that the virus is vertically-transmitted in S. nigrum, and therefore infection appears to be self-sustaining in this species. This is the first report of spillover of YTMMV to exotic weeds, and of vertical transmission of this tobamovirus. We discuss the roles of vertical and horizontal transmission in this spillover event, and its implications for biosecurity

Detection of NMR signals with a radio-frequency atomic magnetometer

We demonstrate detection of proton NMR signals with a radio frequency atomic magnetometer tuned to the NMR frequency of 62 kHz. High-frequency operation of the atomic magnetometer makes it relatively insensitive to ambient magnetic field noise. We obtain magnetic field sensitivity of 7 fT/Hz$^{1/2}$ using only a thin aluminum shield. We also derive an expression for the fundamental sensitivity limit of a surface inductive pick-up coil as a function of frequency and find that an atomic rf magnetometer is intrinsically more sensitive than a coil of comparable size for frequencies below about 50 MHz.Comment: 7 page

Numerical investigations of convective phenomena of oil impingement on end-windings

A novel experimental rig for analysing intensive liquid cooling of highly power-dense electrical machine components has been developed. Coupled fluid flow and heat transfer has been modelled, using computational fluid dynamics (CFD), to inform the design of a purpose-built enclosure for optimising the design of submerged oil jet cooling approaches for electrical machine stators. The detailed modelling methodology presented in this work demonstrates the value in utilising CFD as a design tool for oil-cooled electrical machines. The predicted performance of the final test enclosure design is presented, as well as examples of the sensitivity studies which helped to develop the design. The sensitivity of jet flow on resulting heat transfer coefficients has been calculated, whilst ensuring parasitic pressure losses are minimised. The CFD modelling will be retrospectively validated using experimental measurements from the test enclosure