173,125 research outputs found
Thin plate buckling mitigation and reduction challenges for naval ships
No full textThin plate buckling or distortion on ship structures is an ongoing issue for shipbuilders. It has been identified that a significant number of factors can be put in place based on prior knowledge and good practice. Additionally, research work aimed at reducing thin plate distortion has been relatively prolific, particularly in the area of simulation modelling. However, the uptake in the research findings by industry has been relatively low. A number of these findings are discussed and their application considered. For any further reductions in thin plate distortion to be generated there is a clear need for better interaction between the research institutes and the industry
Toroidal-poloidal partitioning of plate motions since 120 MA
No full textChanges in plate motions and plate configurations during the Cenozoic and Mesozoic have been investigated extensively, but most geodynamical models have concentrated on present-day plate motions. We have investigated the recent evolution of plate tectonics by examining the history of toroidal-poloidal partitioning of plate motions. Taking into account estimated errors, our results suggest a significant increase in the ratio of toroidal to poloidal motions postdating the Hawaiian-Emperor (H-E) bend at 43 Ma, corresponding to an overall decrease in global plate motions. These changes may reflect greater mantle plume activity in the Mesozoic, but a causal mechanism is not obvious. In general, observed Cenozoic and Mesozoic plate motions do not appear to be random, which implies that they are correlated. We also find perhaps three significant changes in net rotation of the lithosphere with respect to hotspots since 120 Ma
On boundary layer in the Mindlin plate model: Levy plates
No full textThis work is related to the bending problem of thick rectangular Levy plates. Series solution for the Mindlin (thick) plate model is obtained and represented as a sum of the Kirchhoff (thin) plate model solution, the ``shear terms'' and the ``boundary layer terms''. Hard- and soft-simple supported, hard- and soft-clamped and free boundary conditions are considered. In order to detect plate regions where Kirchhoff model is good enough, and plate regions where Mindlin model should be used, a model error indicator is introduced. Several examples are presented, illustrating the difference between the Mindlin and the Kirchhoff results, the strengths of boundary layers for different boundary conditions, accuracy of several possible model error indicators and dependence of results on plate thickness. (C) 2007 Elsevier Ltd. All rights reserved
Cenozoic Plate Tectonic Reconstructions and Plate Boundary Processes in the Southwest Pacific
No full textThe Australia-Pacific-Antarctic plate circuit has long been a weak link in global plate reconstruction models for Cenozoic time. The time period spanning chron 20 to chron 7 (43-25 Ma) is particularly problematic for global plate models because seafloor spreading was occurring in two poorly constrained regions in the Southwest Pacific - the Macquarie Basin southwest of New Zealand, and the Adare Basin north of the Ross Sea, Antarctica. I present a new shipboard dataset collected aboard several recent geophysical cruises which places important constraints on the tectonic evolution of these two regions. Utilizing multibeam bathymetry, magnetic, gravity, and seismic data in the Macquarie Basin, I am able to locate tectonic features and magnetic anomalies with greater accuracy than was previously possible. These tectonic features and magnetic anomalies are then used to calculate relative motion between the Australia and Pacific Plates for chrons 18-11 (40-30 Ma). I use revised locations of the rifted margins along the boundary of the Macquarie Basin to determine a best-fit pre-rift reconstruction for this region. During this same time period, seafloor spreading between East and West Antarctica was occurring along the Adare Trough, an extinct spreading center located north of the Ross Sea. Motion along the Adare Trough accounts for roughly 180 km of previously unrecognized motion between East and West Antarctica. I present multibeam and seismic data in the Adare Basin that place constraints on the timing and character of motion along this plate boundary
Numerical computation for parallel plate thermoacoustic heat exchangers in standing wave oscillatory flow
No full textA simplified computational method for studying the heat transfer characteristics of parallel plate thermoacoustic heat exchangers is presented. The model integrates the thermoacoustic equations of the standard linear theory into an energy balance-based numerical calculus scheme. Details of the time-averaged temperature and heat flux density distributions within a representative domain of the heat exchangers
and adjoining stack are given. The effect of operation conditions and geometrical parameters on the heat exchanger performance is investigated and main conclusions relevant for HX design are drawn as far as fin length, fin spacing, blockage ratio, gas and secondary fluid-side heat transfer coefficients are concerned. Most relevant is that
the fin length and spacing affect in conjunction the heat exchanger behaviour and have to be simultaneously optimized to minimize thermal losses localized at the HX-stack
junctions. Model predictions fit experimental data found in literature within 36% and 49% respectively at moderate and high acoustic Reynolds numbers
The role of calcium and predation on plate morph evolution in the three-spined stickleback (Gasterosteus aculeatus)
No full textWhile the genetic basis to plate morph evolution of the three-spined stickleback (Gasterosteus aculeatus) is well described, the environmental variables that select for different plate and spine morphs are incompletely understood. Using replicate populations of three-spined sticklebacks on North Uist, Scotland, we previously investigated the role of predation pressure and calcium limitation on the adaptive evolution of stickleback morphology and behavior. While dissolved calcium proved a significant predictor of plate and spine morph, predator abundance did not. Ecol. Evol., xxx, 2014 and xxx performed a comparable analysis to our own to address the same question. They failed to detect a significant effect of dissolved calcium on morphological evolution, but did establish a significant effect of predation; albeit in the opposite direction to their prediction.Peer reviewe
PLATE-INJECTION INTO A SEPARATED SUPERSONIC BOUNDARY-LAYER
No full textThe structure of a supersonic laminar boundary layer near a flat plate is examined when fluid is injected into it with velocity of O(ε3U*[infty infinity]) over a distance of O(L). Here U*[infty infinity] is the undisturbed fluid velocity, L the length of the plate and ε−8 is a representative Reynolds number. An essential requirement of the theory is that separation must have occurred upstream of the blow through a free interaction. It is assumed that between separation and the blow the reversed flow region has a wedge-like shape, of semi-angle in which O(ε2), the fluid velocity has decayed to insignificant values at points just upstream of the blowing region. The blown fluid fills this wedge and the favourable pressure gradient necessary to drive this fluid downstream causes the boundary of the wedge to curve until at the end of the blow it is parallel to the plate. Explicit expressions for the pressure variation and boundary-layer thickness are worked out using a (crucially) modified form of the Cole-Aroesty theory. The relation. between the strong injection studied here and massive injection, when the blowing velocity is of O(U*[infty infinity]), is also discussed
Real Time Vehicle License Plate Recognition on Mobile Devices
No full textAutomatic license plate recognition is useful in many contexts such as parking control, law enforcement and vehicle background checking. The high cost and low portability of commercial systems makes them inaccessible to the majority of end users. However, current mobile devices now have processors and cameras that make image processing and recognition applications feasible on them. This thesis investigates high accuracy real-time license plate recognition on a smartphone, taking into account device limitations. It first explores how, using the minimal image processing and simple configurable heuristics based on plate geometry, license plates and their characters can be detected in an image. Then, using minimal training data, it shows that a character recognition package can achieve high levels of accuracy. This approach accurately recognized 99 percent of plates appearing in a test set of videos of vehicles with New Zealand license plates
Vortex equilibria in flow past a plate
No full textFamilies of vortex equilibria, with constant vorticity, in steady flow past a flat plate are computed numerically. An equilibrium configuration, which can be thought of as a desingularized point vortex, involves a single symmetric vortex patch located wholly on one side of the plate. Given that the outermost edge of the vortex is unit distance from the plate, the equilibria depend on three parameters: the length of the plate, circulation about the plate, and the distance of the innermost edge of the vortex from the plate. Families in which there is zero circulation about the plate and for which the Kutta condition at the plate ends is satisfied are both considered. Properties such as vortex area, lift and free-stream speed are computed. Time-dependent numerical simulations are used to investigate the stability of the computed steady solutions
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