104,806 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
Fracture mechanics of plate debonding: experimental validation
No full textPremature plate debonding hampers the efficient use of externally bonded FRP plates for flexural strengthening of concrete beams. Existing research mostly concentrates on finite element (FE) modelling of the concrete–FRP interface but such analyses are of dubious validity because they require far more details than will ever be available for the interface. A fracture-mechanics-based plate debonding model has been developed by the authors; since detailed stress analysis of concrete is unattainable the model is based on the global energy balance of the system. Flaws will inevitability be present in the vicinity of the interface; the model investigates the energy balance when such a flaw propagates. The energy released when the crack extends (GR) is compared with the interface fracture energy required to create the new surfaces GF: If GR > GF the crack will extend causing debonding.Determination of both GR and GF associated with crack extension is not trivial because of the unknowable microstructure of concrete. The early work of the present study developed methods to find both parameters to accuracies sufficient for practical purposes. A modified version of Branson’s model, which takes account of the effects caused by the axial force in the FRP, has been developed for the moment–curvature and subsequent GR analyses, while GF has been determined according to the actual fracture mechanism that takes place in the interface.This paper presents comparisons with a variety of plate debonding test data (including steel plate bonded beams) reported in the literature and shows that the present model can correctly determine both the failure load and the debonding mode. Only simply-supported beams, without additional plate end anchors, under short-term monotonic loads are considered here, but the model could be extendedto analyse more complex practical problems
Plate tectonics /
No full textDevelopments in Geotectonics, 6: Plate Tectonics focuses on the exposition of the plate-tectonics hypothesis, as well as plate boundaries, stratification, and kinematics. The book first offers information on the rheological stratification of the mantle and kinematics of relative movements. Topics include lithosphere, asthenosphere, kinematics of finite motions, measurements of instantaneous movements, and worldwide kinematic pattern. The text then ponders on movements relative to a frame external to the plates and processes at accreting plate boundaries. Discussions focus on reference frames,Includes bibliographical references (pages 279-300).Electronic reproduction.Master and use copy. Digital master created according to Benchmark for Faithful Digital Reproductions of Monographs and Serials, Version 1. Digital Library Federation, December 2002.digitizedPrint version record.Front Cover; Plate Tectonics; Copyright Page; Foreword; Preface; Tabel of Contents; CHAPTER 1. Introduction; CHAPTER 2. Definition; CONSEQUENCES; LIMITATIONS; CHAPTER 3. Rheological stratification of the mantle; LITHOSPHERE; ASTHENOSPHERE; THE LITHOSPHERE AS A STRESS-GUIDE; THE DRIVING MECHANISM; CHAPTER 4. Kinematics of relative movements; INTRODUCTION; INSTANTANEOUS MOVEMENTS; KINEMATICS OF FINITE MOTIONS; MEASUREMENTS OF INSTANTANEOUS MOVEMENTS; PRESENT WORLDWIDE KINEMATIC PATTERN; MEASUREMENTS OF FINITE MOVEMENTS; CHAPTER 5. Movements relative to a frame external to the platesINTRODUCTIONREFERENCE FRAMES; ""ABSOLUTE"" MOVEMENT DETERMINATION; PALEOMAGNETIC SYNTHESIS; CHAPTER 6. Processes at accreting plate boundaries; INTRODUCTION; THE CREATION OF THE OCEANIC CRUST; CONTINENTAL RIFTS; CONTINENTAL MARGINS; CHAPTER 7. Processes at consuming plate boundaries; INTRODUCTION; SINKING PLATE MODEL; STRUCTURE OF TRENCHES AND ASSOCIATED ISLAND ARCS AND CORDILLERAS; CONSUMPTION OF CONTINENT-BEARING LITHOSPHERE; PLATE TECTONICS AND GEOLOGY; Appendix; ReferencesDevelopments in Geotectonics, 6: Plate Tectonics focuses on the exposition of the plate-tectonics hypothesis, as well as plate boundaries, stratification, and kinematics. The book first offers information on the rheological stratification of the mantle and kinematics of relative movements. Topics include lithosphere, asthenosphere, kinematics of finite motions, measurements of instantaneous movements, and worldwide kinematic pattern. The text then ponders on movements relative to a frame external to the plates and processes at accreting plate boundaries. Discussions focus on reference frames,Elsevie
Fracture mechanics of plate debonding
No full textThe study has shown that the phenomena of plate debonding can be studied by means of a fracture-mechanics approach, which obviates the need for a finite element analysis which would have dubious validity in the presence of infinite stress concentrations.It has been necessary to produce a modified form of Branson’s method to allow the calculation of the beam stiffness when the section is partially cracked and when subjected to an axial load imposed by the FRP plate.Hutchinson’s interface breakdown model has proved to be a very useful tool for the study of the debonding of FRP plates from concrete structures. More work remains to be done to study the importance of the various parameters that influence the result. Comparisons with experimental data in the literature are being undertaken
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
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
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
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Jetting, In-Nozzle Meniscus Motion and Nozzle-Plate Flooding in An Industrial Drop-on-Demand Print Head
No full textThe state of the ink film at and near the nozzles of a drop-ondemand(DoD) print head during jetting has a direct impact on
printing performance and reliability. We have developed highspeed imaging apparatus and analytical techniques to investigate
the ink film dynamics on an industrial print head nozzle-plate in real-time. In addition to a direct correlation between the jet
emergence velocity and drive voltage, drive-dependent variations in the oscillation of the ink meniscus in adjacent nozzles were also observed. Using a ray-tracing model to analyze the meniscus shape, the meniscus oscillations for both printing and nonprinting nozzles were found to be complex and involve elements such as pre-oscillation and high-order surface waves. The flooding of non-firing nozzles, deliberately caused by the application of maximum drive voltage to a neighboring nozzle, has been recorded and analyzed dynamically. The build-up of fluid in an annulus around the nozzle (flooding rate) has been characterized and compared with models for the net ink flow
through the nozzle
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
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