411,574 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
Systematic investigation of different formulations for drug delivery through the human nail plate "in vitro"
No full textHuman nails do not have only protective and decorative role, but can also be considered as an alternative pathway for drug delivery, especially in nail diseases such as onychomycosis or psoriasis. These nail diseases are widely spread in the population, particularly among elderly and immunocompromised patients. Oral therapies are accompanied by systemic side effects and drug interactions, while topical therapies are limited by the low permeation rate through the nail plate. For the successful treatment of nail disease the applied active drug must permeate through the dense keratinized nail plate and reach deeper layers, the nail bed and the nail matrix. Studies conducted on the human skin elucidated its structure, functions, and its permeability for some substances, but very little is known about skin derivate, the nail, and the properties of nail keratin. The purpose of this work is to improve the understanding of physicochemical parameters that influence drug permeation through the nail plate in order to treat not only topical nail diseases but also to consider the possibility to reach systemic circulation and neighboring target sites. The study was divided in two parts, which will be presented as two published articles. In the first part, caffeine has been chosen as hydrophilic model drug for permeability experiments on human cadaver nail samples. Further, a screening of possible permeation enhancers has been fulfilled and hydrophobins, small amphiphilic fungal proteins with an astonishing feature of selfassembling, have been selected as promising enhancers for drug delivery through the human nail plate. In the second part of the study, lipophilic drug terbinafine, which is applied orally in the treatment of onychomycosis, has been tested in permeability experiments from the formulations with and without hydrophobins.
Transport experiments were carried out in Franz diffusion cells across human cadaver nail samples at 32°C under an occlusive effect. Caffeine was applied in a concentration of 2% (w/v) from the water and 20% (v/v) ethanol/water solutions and it was detected by UV spectrophotometer. Duration of permeability studies with caffeine was six days. Terbinafine was applied in a concentration of 10% (w/v) from the 60% (v/v) ethanol/water solutions and it was detected by HPLC. Permeability experiments with terbinafine lasted 10 days. Characterization of the nail samples and applied formulations was maintained throughout the study in order to illuminate examined absorption processes. To detect amount of a drug remained in the nail after experiment, milling test has been performed.
Identified potential enhancers for drug delivery through the human nail plate were methanol, dimethyl sulfoxide (DMSO), and hydrophobins. Methanol and DMSO induced irreversible structural changes in nail samples, while hydrophobins in most of the cases formed a film layer on the nail surface acting not only as enhancers but as protectors, too. Addition of 20% (v/v) ethanol in the formulations did not influence negatively the hydration of the nail and therefore the permeability coefficient. Among three different tested hydrophobins in the formulations with terbinafine, hydrophobin B increased permeation rate 13.05-fold, which assorted it in the list of substances able to augment drug delivery through the nail plate. Although a hydrophilic drug with lower molecular weight compared to terbinafine, caffeine reservoir in the nail plate samples was detected to be lower than terbinafine reservoir, which was influenced by the duration of experiment and which supported a theory that terbinafine has an affinity towards keratin in the nail plate. The question: Can we increase permeation rate even more and enable substances with different chemical and physical properties to permeate through the death keratinized cells of the nail plate, requires further investigations. Finally, an amount of drug which would be detected in the blood should be estimated in vivo
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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
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
R32 Partial Condensation Inside A Brazed Plate Heat Exchanger
No full textIt is well known that when a superheated gas reaches a cold surface, the condensation starts immediately only if the wall temperature is lower than the dew temperature of the refrigerant; in this case, the heat transfer phenomenon can be also affected by the superheating temperature. This paper presents the experimental measurements of the heat transfer coefficient carried out during partial condensation of superheated R32 refrigerant in a commercial brazed plate heat exchanger prototype. The present work aims at highlighting the effects of the superheating during the partial condensation of R32 by imposing 5, 10, 15, and 25 K of vapour superheating at the inlet of the brazed plate heat exchanger prototype. The experimental measurements were carried out by varying the specific mass velocity between 15 and 40 kg m-2 s-1 and the outlet vapour quality between 0.0 and 0.65. The experimental data were collected at around 36.5 °C saturation temperature (saturation pressure of 2.27 MPa). The present data is used to validate a new step-by-step model for the calculation of the heat transfer coefficient, which accounts for the different superheating inlet temperatures
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