• Journal of Ocean Engineering and Technology
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• v.20 no.4 s.71
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• pp.43-49
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• 2006

Detailed investigations were carried out on the stability of the dredged soil bed against wave actions, aimedat establishing the design method of artificial tidal flats using dredged soil. The soil was dredged at Nagoya port, Japan, and has a mean grain size of 0.013mm. Basic features of artificial dredged soil bed against wave actions were explained from a series of model experiments in a wave flume. The two types of section shapes were employed; one is a horizontal bed and the other is a sloped one. Changes of the bed profile, shear strength, grain size distribution and water content, according to the wave actions, were measured in detail. The cumulative effect of the wave actions, over about one week, was investigated. A dredged soil bed moves withthe wave actions with relatively small wave height. It should be especially. noted that the clay component is dissolved and flown out, away from the surface layer, and consequently the surface layer hardens, as if it is covered with sand. Wren the wave height is gradually increased, the bed is not liquefied and the shear strength of the dredged bed is increased by a wave-induced dissipation of pore pressures in the bed and a decrease of clay component by the wave-induced leakage.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.8
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• pp.53-59
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• 2000

In this study aluminum casting experiments are carried out to reduce the grain size of a cast preform and to spheriodize its dendritic structure by adding Ti+B and Zr and to modify flaked eutectic silicon by adding Sr, And a finite element simulation is performed to determine an optimal configuration of the cast preform to be used in forging of a compressor piston for an automobile air-conditioner. When 0.15% Ti+B Zr and 0.05% Sr are added respectively into the molten aluminum alloy the finest grain in casting of the preform is obtained. It is confirmed that the optimal configuration of the cast preform predicted by FEM simulation is very useful for forging the compressor piston. After forging the cast preform of the compressor piston. the microstructure and the hardness of the cast preform is compared with those of the cast/forged product.

• Advances in aircraft and spacecraft science
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• v.6 no.4
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• pp.333-348
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• 2019

Low fuel regression rate is the main drawback of hybrid rocket which should be overcome. One of the improvement techniques to this problem is usage of a solid fuel grain with a complicated geometry port, which has been promoted owing to the recent development of additive manufacturing technologies. In the design of a hybrid rocket fuel grain with a complicated geometry port, the understanding of fuel regression behavior is very important. Numerical investigations of fuel regression behavior requires a capturing method of solid fuel surface, i.e. gas-solid interface. In this study, level set method is employed as such a method and the preliminary numerical tool for capturing a hybrid rocket solid fuel surface is developed. At first, to test the adequacy of the numerical modeling, the simulation results for circular port are compared to the experimental results in open literature. The regression rates and oxidizer to fuel ratios show good agreements between the simulations and the experiments, after passing enough time. However, during the early period of combustion, there are the discrepancies between the simulations and the experiments, owing to transient phenomena. Second, the simulations of complicated geometry ports are demonstrated. In this preliminary step, a star shape is employed as complicated geometry of port. The slot number effect in star port is investigated. The regression rate decreases with increasing the slot number, except for the star port with many slots (8 slots) in the latter half of combustion. The oxidizer to fuel ratio increases with increasing the slot number.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.1
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• pp.58-67
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• 2021

This paper describes the development for the dual thrust rocket motor with two types of propellants with different combustion characteristics. We developed the composition of two kinds of propellant to be applied to a rocket motor, and improved a propellant charging process in a free grain type to improve the adhesion method and the problems of adhesion between different propellants. In addition, to meet the ignition phenomenon as a small rocket motor, the ignition delay was improved by applying a nozzle plug developed in a high density foam. The propulsion rocket motor reflecting this design and the improved manufacturing process was evaluated through a ground performance test.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.211-211
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• 2022

Amaranth is a nutritious and broadly adapted seed crop in high demand around the world. A preliminary approach for understanding the genetics of amaranth resources entails a morphologic characterization, which can provide the basis for breeding the first variety in Korea, leading to satisfying the needs of farmers and consumers. Therefore, this study aimed to evaluate the phenotypic characteristics of ten genetic amaranth accessions for the selection of outstanding accessions in terms of yield and grain quality. A randomized complete block design was used, with fifteen replications for each accession under field conditions. Five quantitative and three qualitative descriptors were evaluated with descriptive analysis. The results showed that the accessions with plant heights smaller than the average (>112.7 cm) presented lower yields and smaller seed sizes, thus decreasing the grain quality. The cluster analyses established groups of accessions with good yields (>30.1 g of seeds per plant) and stable morphological characteristics. Based on yield and morphological descriptors, the proposed selection index indicated four accessions as potential parents for amaranth breeding programs in Kora.

• Korean Institute of Interior Design Journal
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• no.41
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• pp.11-18
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• 2003

This study was carried out to find the cases of change in the Anglican Church including its rectory in Onsuri, Gangwha island, which was built in Korean traditional architecture style. The materials used for the study were published books, old photos taken before the change, drawings, and field survey. The result are as followings. 1) Painting concealed natural wooden grain should be removed as well as carpet on the wooden floor. The way of ceiling finishing is to be restored as traditional way. 2) Refer to the rectory, it needs to be restored totally, since it has been changed many times through partial renovation. It lacks unification of design in entire elevation, windows and door. The practical spaces such as indoor flush toilet and boiler room are desirable not to be revealed or designed in harmony with other spaces. 3) Stript flooring in the rectory are to be restored to frame flooring, room finishing including vinyl flooring, vinyl wall paper and moulding along the cornice to the traditional paper finish. Lattice patterns of windows and doors are recommended to be restored according to the traditional design.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.358-363
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• 2017

The high intercept probability depends on optimization of the system, which consists of target detection, tracking system, missile system and so on. To reduce the complexity of global optimization of the system performance, simplification of the relative dependances of each sub-system is done and design parameters for DACS configuration are identified. The conceptual design process is addressed based on the requirement of the design parameters and new methodology is suggested for higher performance.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.226-233
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• 2022

In the present work, a phase-field model was developed to investigate the influence of recrystallization on bubble evolution during irradiation. Considering the interaction between bubbles and grain boundary (GB), a set of modified Cahn-Hilliard and Allen-Cahn equations, with field variables and order parameters evolving in space and time, was used in this model. Both the kinetics of recrystallization characterized in experiments and point defects generated during cascade were incorporated in the model. The bubble evolution in recrystallized polycrystalline of U-Mo alloy was also investigated. The simulation results showed that GB with a large area fraction generated by recrystallization accelerates the formation and growth of bubbles. With the formation of new grains, gas atoms are swept and collected by GBs. The simulation results of bubble size and distribution are consistent with the experimental results.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.286-291
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• 2023

Perovskite materials are promising candidates for next-generation optoelectronic devices owing to their outstanding external quantum efficiency, high color purity, and ability to tune the light emission wavelength. However, conventional thermal annealing processes caused the degradation of perovskite, resulting in poor optoelectronic properties and a short lifetime. Herein, we propose a laser-induced recrystallization of perovskite thin film to enhance its light-emitting properties. Laser-induced recrystallization process was performed using rapid and instantaneous laser heating, which successfully induced grain growth of the perovskite material. The laser processing conditions were thoroughly optimized based on theoretical calculations and various material analyses such as x-ray diffraction, scanning electron microscope, and photoluminescence spectroscopy.

• Journal of the Korean Society of Costume
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• v.56 no.4 s.103
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• pp.48-64
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• 2006

The purpose of the study was to demonstrate how to recreate spencer jacket in the empire style in an attempt to apply this historic style to theatrical costumes and other high fashion items in modern times. The study was carried out through 2 steps. (1)Block patterns of spencer jacket of its basic design were developed through draping based on the design characteristics mentioned above. (2)Spencer jackets of three designs, which were the typical designs of each category have been made of velvet to find out more specific structural characteristics. The structural characteristics of Spencer jacket in draping were as follows: (1)Jacket length position was suitable 9cm below body's bust line and neckline should be enlarged front & side neck point 2cm, back neck point 1.5cm. (2)Cut out the front bodice after CF line moved 1cm outwards and bust dart amount should not exceed 2-3cm. Shoulder point moved inwards. (3)Side back grain line was parallel to princess line of the back bodice. Add 0.5cm ease to the under arm of the front and side bark bodice, it was good for the activity of arm. (4)Armhole line was trued as maintaining to across back width 14-15cm at least. Shoulder line was to connect from the point 2cm depart shoulder point along armhole line to point 2cm side neck point along neck line. (5)Sleeve length was suitable 70cm, cut out the bias direction to move forwards the grain line from shoulder point. Puff position was good from the 2cm depart shoulder point to shoulder line.