1,668 research outputs found
Good Words (Magazine) for 1868
No full textAs Abbey writes, the fable articles here precede and are different from their first appearance in book form a year later. For it was then that Ralston published the first edition of Krilof and His Fables. See my comments on the third (1871) and fourth (1883) editions. The book smells of its many years! The three fable articles are on 39-46, including six illustrations on 40-41; 215-221, including six illustrations on 216-17; and 413-20, including six illustrations on 416-17. These are magazine articles. They comment on Krilof's views and particularly on Russian foibles. Thus one prose text after another is integrated into the article. In the book, there will be, after a preface and a memoir, a simple collection of texts. In fact, the selection of Krilof fables within the article here is excellent, and the author puts them into a good cultural and political context. At least some of the illustrations are the same as those in the third edition.. The texts are close to those found in the published books. It makes sense to see the texts in the magazine here as forerunners of those fable texts there. I presume that Ralston had opportunity to edit and amend between his magazine articles and his book's first edition. The publisher of the magazine is of course the publisher of the third edition that I have. The print is minuscule! I needed a magnifying glass for normal reading. The index just after 774 assigns J.B. Zwecker and A.B. Houghton as illustrators for the eighteen illustrations in the three fable articles. Dalziel, Houghton, and Zwecker are the names I can make out on the illustrations. Dalziel is not mentioned on the title page, but there is reference to others.This is a hardbound book (hard cover)Norman MacLeod; W.R.S. Ralston for fable
Simple drag prediction strategies for an Autonomous Underwater Vehicle’s hull shape
No full textThe range of an AUV is dictated by its finite energy source and minimising the energy consumption is required to maximise its endurance. One option to extend the endurance is by obtaining the optimum hydrodynamic hull shape with balancing the trade-off between computational cost and fluid dynamic fidelity. An AUV hull form has been optimised to obtain low resistance hull. Hydrodynamic optimisation of hull form has been carried out by employing five parametric geometry models with a streamlined constraint. Three Genetic Algorithm optimisation procedures are applied by three simple drag predictions which are based on the potential flow method. The results highlight the effectiveness of considering the proposed hull shape optimisation procedure for the early stage of AUV hull desig
The use of computational fluid dynamics to assess the hull resistance of concept autonomous underwater vehicles
No full textAutonomous Underwater Vehicles (AUV’s) provide an important tool for collecting detailed scientific information from the oceans depths. The hull resistance of an AUV is an important factor in determining the powering requirements and range of the vehicle. This paper discusses the use of Computational Fluid Dynamics (CFD) to determine the hull resistance of three existing AUV’s, of differing shape and size. The predictions are compared with available experimental data and good agreement found. This work has demonstrated that with use of suitable shape parameterisation it is possible to carry out concept design evaluation using a RANS flow solver
Electrical and magnetic properties of II-VI diluted magnetic semiconductors
No full textThe electrical and magnetic properties of MOVPE grown epitaxial layers of Hg(_1-x)Mn(_x)Te layers has been investigated using a number of techniques. The samples have been grown by the Inter Diffused Multilayer Process, (IMP) on (100) semi insulating GaAs substrates with ZnTe and CdTe buffer layers. The samples have been shown to show a number of phenomena nopt observed in the bulk material, such as an anomaly in the resistivity, rnagnetoresistance related to the intrinsic magnetism of the material, and saturation of the room temperature magnetisation. In general the samples are of a highly compensated nature with the value of |R(_H)e|(^-1) varying between l0(^14) and 5xI0(^17) cm(^-3) at 20K, the Hall mobilities varying between 8 and 3.5x10(^5) cm(^2)V(^-1)s(^-1) at 20K. Magnetically, the samples generally show a paramagnetic signal that is swamped by the diamagnetic background of the substrate and buffer layers. The paramagnetisrn can be well modelled using a Curie Weiss fit. A number of the samples show a saturation in the magnetisation, which, has been explained via the use of vacancy ordering within MnTe regions in the sample. The susceptibility of the samples has been investigated using a Faraday balance system, and this data has been fitted using; a cluster model for Mn ions within the sample. The photomagnetisation of Cd(_0.9)Mn(_0.1)Te:In has been investigated using a faraday balance system, and modelled using the work of Dietl and Sample, to calculate the number of polarons that had formed on donors in the sample, ΔN(_D)(^MAG) = 1.28x10(^15)cm(^-3). The number of donors in the sample has been measured by means of the Hall effect, ΔN(_D)(^ELEC) = 1.92x10(^15)cm(^-3), and this value compared to that obtained from the model. We have proposed a model to explain this discrepancy based on the concept of band tails in the impurity band
Autobiography of Captain John Hodgson : of Coley Hall, near Halifax; his conduct in the Civil Wars, and his troubles after the Restoration /
No full textIncludes indexesContains facsim. of original t.p. of his "Memoirs."Bibliography: p. [83-84]Mode of access: Internet
The impact of placement method on Antifer-block stability
No full textThe main objective of this research was to assess the impact of different placement methods, with different packing densities, on the stability of double layered Antifer-block armour layers. This was done by experimental research in the wave-flume of the Fluid mechanics laboratory of the Faculty of Civil Engineering and Geosciences at Delft University of Technology. 17 experiments were performed with packing densities between 44.8 and 61.1 percent. For every experiment the under layer, toe and armour layer were rebuilt. The placed Antifer layer was tested with eight irregular wave series with increasing significant wave heights from 9cm up to 20cm. From these experiments followed that regular placement methods behave more stable than irregular placement methods with a similar packing density. Also the more irregular (less accurate) positioning of blocks within a regular placement method caused a decrease in stability. Higher packing densities for equal placement methods lead to higher stabilities and higher reflection coefficients. The resulting -values were between 4.0 and 23.7. If the reflection coefficients during the first wave series were high, this resulted in more overtopping during the latest wave series, which indicates that there is a positive correlation between the reflection and the overtopping. Overall it could be concluded that, when the under layer and the toe are smooth and the blocks can be placed accurately, the best performing placement methods are the closed pyramid placement method for packing densities around 45% and 50% and the double pyramid placement method for packing densities around 55% and 60%. The size of the openings to the under layer, of the double pyramid placement method, influenced the reflection coefficients. When the second layer was shifted half a nominal diameter upwards the reflection coefficients were minimal. It is recommended to investigate the possible negative influence of oblique incoming waves on the stability of the double pyramid placement method. The eventual choice of the placement method and packing density depends on the allowed reflection and/or overtopping and the construction costs. The construction costs can be divided into the production costs, the placement costs and the constant costs. For equal constant costs and equal or small differences in placement costs the placement with the higher packing density and accompanying stability value is cheaper for high design wave heights. When the placement costs decrease for both placements or only for the placement with the higher packing density, then the placement with the higher packing density becomes also cheaper for lower wave heights.Civil Engineering and Geoscience
The simulation of free surface flows with Computational Fluid Dynamics
No full textComputational fluid dynamics is a powerful and versatile tool for the analysis of flow problems encountered in themaritime environment. The University of Southampton Fluid-Structure Interactions research group use ANSYS CFX tomodel a wide variety of flow problems; to gain insight into flow physics, improve designs and increase the efficiencyand safety of marine vehicles. A series of three case studies from on-going research looks at: loads applied on liquefiednatural gas tanks due to sloshing, slamming pressures experienced by high speed craft as well as the influence ofpropellers on the resistance characteristics of autonomous underwater vehicles. The presence of the free surface,complex shapes and the unsteady nature of these applications make their simulation with computational fluid dynamicsparticularly challenging. The successful validation of the computational models has resulted in the development of aselection process for suitable multiphase models as well as cost-effective meshing strategies
Transient Skin Effect in Power Electronic Applications
No full textThis study describes transient electromagnetic phenomena in electrical conductors that are connected to modern power electronic circuits and therefore subjected to current controlled pulses with fast rise times and high peak current ratings. Electromagnetic field diffusion is discussed and a brief review of alternating current skin effect phenomena is presented before it is generalised to transient regimes of operation. It is shown that the magnetic field diffuses into the conductor from the outside on the initiation of a current pulse and therefore the axial current density distribution inside the conductor changes with time under a transient current due to the well-known electromagnetic relations – the current begins at the conductor surface and diffuses inwards. The implications of such behaviour are briefly discussed in the context of modern power electronics and its applications
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