• Ocean Systems Engineering
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• v.11 no.1
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• pp.83-97
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• 2021

The submerged U-shape breakwater interaction with the solitary wave is simulated by the Boussinesq equations using the finite-difference scheme. The wave reflection, transmission, and dissipation (RTD) coefficients are used to investigate the U-shape breakwater's performance for different crest width, Lc1, and indent breakwater height, du. The results show that the submerged breakwater performance for a set of U-shape breakwater with the same cross-section area is related to the length of submerged breakwater crest, Lc1, and the distance between the crests, Lc2 (or the height of du). The breakwater has the maximum performance when the crest length is larger, and at the same time, the distance between them increases. Changing the Lc1 and du of the U-shape breakwaters result in a significant change in the RTD coefficients. Comparison of the U-shape breakwater, having the best performance, with the averaged RTD values shows that the transmission coefficients, Kt, has a better performance of up to 4% in comparison to other breakwaters. Also, the reflection coefficients KR and the diffusion coefficients, Kd shows a better performance of about 30% and 55% on average, respectively. However, the model governing equations are non-dissipative. The non-energy conserving of the transmission and reflection coefficients due to wave and breakwater interaction results in dissipation type contribution. The U-shape breakwater with the best performance is compared with the rectangular breakwater with the same cross-section area to investigate the economic advantages of the U-shape breakwater. The transmission coefficients, Kt, of the U-shape breakwater shows a better performance of 5% higher than the rectangular one. The reflection coefficient, KR, is 60% lower for U-shape in comparison to rectangular one; however, the diffusion coefficients, Kd, of U-shape breakwater is 35% higher than the rectangular breakwater. Therefore, we could say that the U-shape breakwater has a better performance than the rectangular one.

• Journal of the Korean GEO-environmental Society
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• v.9 no.5
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• pp.83-89
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• 2008

This study is to figure out the speed of soil diffusion and shapes as well when landslide occurred. It was measured the speed and shapes of soil diffusion using installed indoor-simulation of a land slide. Standard sand was used to measure it and this measurement is following the moisture content of standard sand. The result of this experiment follows the moisture content; as the moisture content goes up, the area and speed of soil diffusion goes faster as well. As the average of records by the moisture content was analyzed, the area and speed of land slide are increased proportionally. The shape of diffusion is formed as fanwise. It depends on the moisture content as above; the speed was fast when the moisture content is high, and it was getting narrower and longer as the speed of diffusion was faster.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.50-56
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• 2001

Fabrication methods are shown to produce slender and cylindrical tungsten shafts by electrochemical etching. The shape of microshatf formed by electrochemical etching is determined by the combination of two conflicting factors, i.e., initial shape and diffusion layer. We can obtain a desirable shaft profile by adjusting the thickness gradient of diffusion layer. The diameter of microshaft is controlled by mathematical model based on relation between process parameters and diameter.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.11
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• pp.1464-1472
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• 1995

In this paper, we propose an error diffusion image halftoning technique based on the noise spectrum shaping. The new technique can arbitrarily control the shape of the display error spectrum whereas conventional halftoning algorithms have been known to minimize dc errors only in which case edge information cannot be properly rendered. As a method for estimating the error diffusion coefficients, a least mean square (LMS) approach is adopted.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.2
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• pp.49-55
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• 2018

A T-shape structure was manufactured by the superplastic forming and diffusion bonding process using two Ti-3Al-2.5V alloy tubes. A Ti-3Al-2.5V tube was prepared for the hydroforming in the superplastic condition until it reaches a surface area such as a roof welded in the hole of another Ti-3Al-2.5V tube. Afterward, the superplastic forming process and the diffusion bonding process were carried out simultaneously until the appropriate bonding along the interface area of two Ti-3Al-2.5V tubes was obtained. The bonding qualities were different at each location of the entire interface according to the applied process conditions such as strain, pressure, temperature, holding time, geometries, etc. The microstructures of bonding interface have been observed to understand the characteristics of the applied processes in this study.

• Nuclear Engineering and Technology
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• v.53 no.2
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• pp.399-413
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• 2021

The solution of the time-dependent neutron diffusion equation can be approximated using quasi-static methods that factorise the neutronic flux as the product of a time dependent function times a shape function that depends both on space and time. A generalization of this technique is the updated modal method. This strategy assumes that the neutron flux can be decomposed into a sum of amplitudes multiplied by some shape functions. These functions, known as modes, come from the solution of the eigenvalue problems associated with the static neutron diffusion equation that are being updated along the transient. In previous works, the time step used to update the modes is set to a fixed value and this implies the need of using small time-steps to obtain accurate results and, consequently, a high computational cost. In this work, we propose the use of an adaptive control time-step that reduces automatically the time-step when the algorithm detects large errors and increases this value when it is not necessary to use small steps. Several strategies to compute the modes updating time step are proposed and their performance is tested for different transients in benchmark reactors with rectangular and hexagonal geometry.

• Design & Manufacturing
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• v.13 no.4
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• pp.40-44
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• 2019

The light diffusion component spreads the light from one point evenly over a large area. Various types of light diffusion parts such as films and lenses are applied in the high-tech industries such as LCD display devices, lighting devices, and solar energy generation. Among these, a diffuser sheet (Diffuser Sheet) has a function to uniformly distribute the light, and various studies have been conducted to improve its function. The shape of the conventional light diffusion pattern is mainly made of a dot or hemispherical shape. In this study, a rectangular cone-shaped structure having a light diffusion function and an advantage of controlling the angle of refraction of light was fabricated by using a solenoid indentation process. The change in shape of the indentation structure was analyzed.

• Journal of Ocean Engineering and Technology
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• v.32 no.4
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• pp.261-271
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• 2018

In this study, a hydraulic model test, to which Particle Image Velocimetry (PIV) system applied, was used to determine the hydrodynamic characteristics of the advection-diffusion of saltwater according to bottom conditions (impermeable/permeability, diameter, and inclination) and the difference of the initial salt. Considering quantitative and qualitative results from the experiment, the characteristics of the density current were discussed. As an experimental result, the advection-diffusion mechanism of salinity was examined by the shape of saltwater wedge and the flow structure of density currents with various bottom conditions. The vertical salt concentration obtained from the experiment was used as quantitative data to calculate the diffusion coefficient that was used in the numerical model of the advection-diffusion of saltwater.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.157-163
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• 2006

A new technique utilizing LII signal for the measurement of flow velocities of laminar diffusion flames has been investigated. Soot particles in ethylene diffusion flames are heated by a modulated Ar-ion laser beam. LII signals and their phase angles are measured using a lock-in amplifier at the different flame heights and the axial flow velocity are obtained from the measured phase angle delay. The measured velocities are similar to those from LDV measurements under the same operating conditions. The effects of laser power, LII signal wavelength, and modulation frequency are not sensitive to the velocity measurement. However, the choice of an optical chopper blade type could affect the measurement result. The use of a 6/5 chopper blade showed the better result that is possibly due to the square shape of modulated laser beam. This study successfully demonstrated that axial flow velocities of laminar diffusion flames can be measured by a new technique utilizing LII signal, which does not need particle seeding unlikely to LDV or PIV techniques.

• IE interfaces
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• v.23 no.4
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• pp.337-348
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• 2010

The Bass model is the most widely used model in research of new product diffusion because it presents a nice explanation on the diffusion process of new products. However, it has a limitation that its performance of fitness is lower as the available data become less and also, the diffusion curve is bell-shape and so, it can not represent the various diffusion patterns. Recently, a two-pieces Bass model is developed and applied to analyze diffusion of 10 products. The results are encouraging in terms of fitness. However, diffusion pattern is not dealt with in the paper. In this paper, analysis of diffusion pattern is in depth addressed in two-pieces Bass model. It is shown that the diffusion curves are divided into 3 types with respect to the peak adoption rate and each type is divided into 2 types further. Takeoff time of a diffusion process is analyzed by using the inflection point and regime-change time where it represents the point that imitation and innovation parameters change. Empirical studies for 68 products(28 domestic products and 40 USA products) are performed to analyze the diffusion pattern. Findings are that diffusion patterns of all products except 1 USA product show type I and regime-change time becomes shorter as the introduction time of the product is later in domestic products and regime-change time can be regarded as a takeoff time in 47% of total 68 products.