Korean language math-to-speech rules for digital books for people with reading disabilities and their usability evaluation

The Journal of Supercomputing - Although Digital Accessible Information System, an international digital talking book standard, is conducting active research on upper level education for people...     

A study of the influence of air-knife tilting on coating thickness in hot-dip galvanizing

Gas wiping is a decisive operation in hot-dip galvanizing process. In special, it has a crucial influence on the thickness and uniformity in coating film, but may be subsequently responsible for the problem of splashing. The progress of industry demands continuously the reduction of production costs which may relate directly with the increase of coating speed, and the speed up of coating results in the increase of stagnation pressure in gas wiping system in final. It is known that the increase of stagnation pressure may accompany a harmful problem of splashing in general. Together with these, also, from the view point of energy consumption, it is necessary to design a nozzle optimally. And there is known that the downward tilting of nozzle using in air knife system is effective to prevent in somewhat the harmful problem of splashing. In these connections, first, we design a nozzle with constant expansion rate. Next, for the case of actual coating conditions in field, the effects of tilting of the constant expansion rate nozzle are investigated by numerical analysis. Under the present numerical conditions, it was turned out that the nozzle of constant expansion rate of p = having a downward jet angle of 5° is the most effective to diminish the onset of splashing, while the influence of small tilting of the nozzle on impinging wall pressure itself is not so large.     

Scan-Along Polygonal Approximation for Data Compression of Electrocardiograms

Three fast and efficient "scan-along" algorithms for compressing digitized electrocardiographic data are described. These algorithms are "scan-along" in the sense that they produce the compressed data in real time as the electrocardiogram is generated. The algorithms are based on the minimum perimeter polygonal approximation for digitized curves. The approximation restricts the maximum error to be no greater than a specified value. Our algorithms achieve a compression ratio of ten on a database of 8000 5-beat abnormal electrocardiograms sampled at 250 Hz and a compression ratio of eleven on a database of 600 3-beat normal electrocardiograms (different from the preceding database) sampled at 500 Hz.     

An experimental study of supersonic dual coaxial free jet

A supersonic dual coaxial jet has been employed popularly for various industrial purposes, such as gasdynamic laser, supersonic ejector, noise control and enhancement of mixing. Detailed characteristics of supersonic dual coaxial jets issuing from an inner supersonic nozzle and outer sonic nozzles with various ejection angles are experimentally investigated. Three important parameters, such as pressure ratios of the inner and outer nozzles, and outer nozzle ejection angle, are chosen for a better understanding of jet structures in the present study. The results obtained from the present experimental study show that the Mach disk diameter becomes smaller, and the Mach disk moves toward the nozzle exit, and the length of the first shock cell decreases with the pressure ratio of the outer nozzle. It was also found that the highly underexpanded outer jet produces a new oblique shock wave, which makes jet structure much more complicated. On the other hand the outer jet ejection angle affects the structure of the inner jet structure less than the pressure ratio of the outer nozzle, relatively.     

Supersonic moist air flow with condensation in a wavy wall channel

The characteristics of Prandtl-Meyer expansion of supersonic flow with condensation along a wavy wall in a channel are investigated by means of experiments and numerical analyses. Experiments are carried out for the case of moist air flow in an intermittent indraft supersonic wind tunnel. The flow fields are visualized by a Schlieren system and the distributions of static pressure along the upper wavy wall are measured by a scanning valve system with pressure transducers. In numerical analyses, the distributions of streamlines, Mach lines, iso-pressure lines, and iso-mass fractions of liquid are obtained by the two-dimensional direct marching method of characteristics. The effects of stagnation temperature, absolute humidity, and attack angle of the upper wavy wall on the generation and the locations of generation and reflection of an oblique shock wave are clarified. Futhermore, it is confirmed that the wavy wall plays an important role in the generation of an oblique shock wave and that the effect of condensation on the flow fields is apparent.     

Effect of rupture disc curvature on the compression waves in S/R valve

When the pressure at a weak spot established at a certain part of a high pressure vessel or piping system exceeds a design pressure, this weak spot bursts, and the pressurized gas emitted through the weak spot generates a compression wave system at the downstream of the disc. In this connection, an experimental study was performed by using a shock tube facility with dimensional analysis to relate the valve opening time and shock wave formation distance with the diaphragm radius of curvature, the pressure ratio and depth of cross type groove. Four kinds of curvature radii were used with and without 90° groove. It was found that the smaller the radius of curvature of the rupture disc is, the thinner the thickness of the rupture disc is; and the smaller the ultimate strength of the rupture disc is, the shorter the valve opening time becomes. The radius of curvature and the ultimate strength of the rupture disc for the same conditions are smaller; the maximum pressure rise caused by the coalescences of the compression wave at the downstream of the valve is smaller. Finally, we found that the formation distance of the shock wave for the case of smaller curvature is longer than that for the case of a larger one because of the retardation of accumulation of the compression wave.     

A study on the flow with nonequilibrium condensation in a minimum length nozzle

As recognized previously, a minimum-length nozzle has the smallest possible throat-to-exit length that is still capable of maintaining uniform supersonic flow at the nozzle exit. In the present study, for the flow of moist air through a nearly minimum-length nozzle designed by the method of characteristics, the effects of nonequilibrium condensation on the uniformity of flow properties, the momentum efflux, and the flow distortion at the nozzle exit plane are discussed by experiment and numerical analysis of a third-order Total Variation Diminishing (TVD) finite difference scheme. The onset and zone of nonequilibrium condensation in a minimum-length nozzle are quite different from those of a general convergent-divergent supersonic nozzle. We know that the uniformity of flow properties at the nozzle exit with regard to the flow with nonequilibrium condensation in a minimum-length nozzle cannot be guaranteed. On the other hand, owing to the positions of the onset of condensation at the incident region of expansion waves from the sharp corner just downstream of the nozzle throat, the deceleration gradient and magnitude of heat released from the process of nonequilibrium condensation to the surrounding of ϕ₀=60% are greater than those of ϕ₀=70% in the case of T₀=290K. Furthermore, it has been determined that the decrease in efflux of momentum from the nozzle exit for the stagnation relative humidity of ϕ₀=70%(T₀=290K), which corresponds to the case with nonequilibrium condensation shock, is 6.8% smaller than that of isentropic expansion. This paper was recommended for publication in revised form by Associate Editor Do Hyung Lee Soon-Bum Kwon received his B.S. and M.S. degrees in Mechanical Engineering from Kyungpook National University in 1974 and 1980, respectively, and his Ph.D. degree from Kyushu University in 1987. He is a Professor at the School of Mechanical Engineering at Kyungpook National University. His research interests are compressible gas dynamics and nonequilibrium condensation.     

Experimental and computational studies on Coanda nozzle flow for the air knife application

To control the film thickness of zinc in the process of continuous hot-dip galvanizing,it is known from the earlydays that the gas wiping through an air knife is the most effective one.The gas wiping using in galvanizing proc-ess brings about a problem of splashing from the strip edge for a certain high speed of coating.So,in the presentstudy,the effects of the deflection angle of Coanda nozzle on jet structure and the distribution of impinging pres-sure at the plate surface are investigated numerically and experimentally.In numerical analysis,the governingequations consisted of three-dimensional time dependent full Navier-Stokes equations,standard k-ε turbulencemodel to solve turbulent stress and so on are employed.In experiment,16 channel pressure scanning valve and3-axis auto traversing unit are used to measure the impinging pressure at the strip surface.As a result,it is foundthat the smaller the deflection angle for the same nozzle slit of air knife is,the larger the impinging pressure is.Toreduce the size of separation bubble and to enhance the cutting ability,it is recommendable to use an air knifewith the Coanda nozzle.     

A sketch-based interface to modify and reproduce motion sequences

We present a sketch-based user interface, which was designed to help novices to create 3D character animations by multi-pass sketching, avoiding the ambiguities usually present in sketch input. Our system also contains sketch-based editing and reproducing tools, which allow paths and motions to be partially updated rather than wholly redrawn; and graphical block interface permits motion sequences to be organized and reconfigured easily. A user evaluation with participants of different skill levels suggest that novices using this sketch interface can produce animations almost as quickly as users who are experienced in 3D animation.