• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.7
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• pp.653-658
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• 2016

High pressure components of a gas turbine engine are generally made of nickel-base superalloys, using precision casting process due to complicated geometries with intricate channels and cooling holes. Turbine components manufactured from directionally solidified and single crystal materials have columnar grains; however, it is found that the crystals do not grow in its preferred direction, although the orientation can be controlled. This anisotropy can lead to the variations of elastic and Hill's parameters in constitutive equations, and they alter stress distributions and the low cycle fatigue life. We aims to evaluate the effects of perturbed crystal orientations on the structural integrity of a directionally solidified nozzle using low cycle fatigue life. We also attempt to show the necessity for the control of allowed manufacturing errors and stochastic analysis. Our approaches included conjugate heat transfer and structural analysis, along with low cycle fatigue life assessment.

• Journal of Technologic Dentistry
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• v.23 no.1
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• pp.65-73
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• 2001

The purpose of this study was to investigate the microstucture and hardness, corrosion of pure Ti alloy, which is widely used as partial denture frame work these days, depending on the cooling method, followed by casting. The first group was bench cooling at room temperature($18^{\circ}C$), the second group was slowly cooled in the furnace from $700^{\circ}C$ to room temperature, and third. rapidly cooled in $0^{\circ}C$ water. The microstructure of each specimen observed by means of photomicrograph taken by electron microscope, in add to the physical characteristics of each specimen were obtained using the rockwell Hardnest Number. the characteristics of corrosion. The results were obtained as follows: 1. From Potentiodynamic plot. we conclude furnace-cooled specimen had the best stabiltity of passive film and that air-cooled specimen showed similar characteristics. The density of electric current of quenched specimen was the highest, which formed kind of unstable passive film. 2. Specimen cooled at room temperature (air cooling) had the highest value of hardness of 81.26HRB, specimen cooled at ice-water, $0^{\circ}C$, had the value of 78.42HRB, and specimen furnace-cooled at $700^{\circ}C$ had lowest value of 77.1HRB. 3. Quenching treated micro-structure formed martensite structure by and large. In case of air cooling, we could see $\alpha$-structure widmanstatten formed overall. In furnace cooling, widmanstatten structure and various shape $\alpha$-structures forming colony with direction were detected.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.405-408
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• 2008

The most effective factors that improve sections and elongate spans of the prestressed concrete girders are shapes of sections and strengths of concretes, and the concrete strength is more influenced to enhance the allowable tensile strength on top and bottom fibers than increasing of flexural strength of girders. In this study, 60 MPa high-strength prestressed concretes were constructed at the Wonsoo Bridge where in the 1st section of expanding constructions of the Nonsan to Junjoo Expressway, the high-strength concrete was placed on the eight- 35 meters simple span IPC girders of four lanes of Nonsan direction. During casting of girder concretes, quality controls were carried out with continuing controls of surface moistures and corrections of the unit water using the air-meter methods right after batching. It was confirmed that compressive strengths of girder concretes ensure the target strength and the heat of hydrations of girder concrete were measured. Though using same materials and constructing methods, there're a wide range of strengths of each girder, so, when high-strength concretes cast in the place hereafter, a countermove should be prepared.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.4
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• pp.95-104
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• 1999

Use of the ultra thick plate is being continuously increased in large off-shore structures, ships, bridges and skyscraper construction, due to increasingly large-sized steel structures and it seems that this trend will be maintained. But, occurrence of the lamella tearing has been reported in ultra thick plate used for construction. It is reportedly caused by impurities such S(sulfur), P(phosphorus) and others accumulated in the ultra thick plate's centerline in the thickness direction with strip shape or by restraint residual stress caused by the welding. In the ultra thick plate made by continuous casting method, occurrence of lamination is difficult to avoid because of the properties of production procedure. Therefore, with a view to reducing the lamella properties, this report tries tearing in the steel structure in the view of welding strength rather than metallic properties, this report tries to seek the optimum groove and welding procedure by using the computer simulation based on FEM(Finite Element Method).

• Convergence Security Journal
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• v.13 no.4
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• pp.61-68
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• 2013

Compared to the past, the number of disabled people in Korea is continuing to increase. As for the scope of the disability, it is expanding as well since it now includes all types of illnesses, car accidents, complications resulting from aging, industrial accidents and others accidents. Attempts are made in terms of applying sports game method that grafts IT technology in order to ensure that the disabled people participate continually in sports. While casting away the notion of play which was the role of a game in the past, new roles and domains were developed. In fact, serious game genre is what leads this change. Because serious game is leading the game industry fast, centered on education, sports, fitness and medical use, its market value can be considered very significant since it can be both fund and effective as it targets the disabled who cannot enjoy sports easily in reality. Accordingly, this research seeks to present the direction for the application of serious game for the disabled people by analyzing the current situation pertaining to the integrated and converged cases applied to the field of sports for the disabled when it comes to the serious game that uses contents based on the IT technology.

• Journal of Powder Materials
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• v.28 no.4
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• pp.331-335
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• 2021

The effects of drying temperature on the microstructure of porous W fabricated by the freeze-casting process of tert-butyl alcohol slurry with WO₃ powder was investigated. Green bodies were hydrogen-reduced at 800℃ for 1 h and sintered at 1000℃ for 6 h. X-ray diffraction analysis revealed that WO₃ powders were completely converted to W without any reaction phases by hydrogen reduction. The sintered body showed pores aligned in the direction of tert-butyl alcohol growth, and the porosity and pore size decreased as the amount of WO₃ increased from 5 to 10vol%. As the drying temperature of the frozen body increased from -25℃ to -10℃, the pore size and thickness of the struts increased. The change in microstructural characteristics based on the amount of powder added and the drying temperature was explained by the growth behavior of the freezing agent and the degree of rearrangement of the solid powder during the solidification of the slurry.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.1
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• pp.13-24
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• 1994

Purse seiner detects a fish school navigating in full speed with the aid of fish finder, sonar, helicopter, etc., and casts a net quickly to enclose the fish school in purse seine net according to the movement of the fish school, wind, and current. At this moment, if the time of casting a net, direction, speed, and turning circle are net suitable, it is unavoidable to lose fish school founded with hard efforts and we only consume our efforts of casting and hauling the net. Therefore, in order to enclose the fish school to enhance the amount of fish for each casting, the author investigated the type of ships equipped with purse seiners and examined maneuvering tests so that we provide some basic information to figure out the ability of steerage correctly. The results obtained are summarized as follows: 1. Block coefficients of pelagic tuna purse seiners with gross tonnage between 500 and 1500 tons are recorded between 0.50 and 0.55 which are greater than those of off shore purse seiners recorded as between 0.44 and 0.54 and less than those of various cargo ships recorded as between 0.56 and 0.84. 2. L/B, L/D, B/D, B/T, and T/D of the class of gross tonnage between 75 and 130 tons are respectively 4.49, 11.00, 2.45, 2.85 and 0.86 as their average and those of the class of between 500 and 1500 tons are 4.89, 10.53, 2.15, 2.73 and 0.75 respectively, which are quite different from those of various cargo ships recorded as 6.0~7.5, 11.0~12.0, 1.6~2.0, 2.2~2.8 and 0.65~0.75 respectively. 3. Rudder area ratio of purse seiners of the class of between 75 and 130 tons is 1/24~1/31 and that of the clase of between 500 and 1500 tons is 1/36~1/42 which is greater than that of various cargo ships recorded as 1.45~1.75. 4. On speed-length ratio of purse seiners. 111 Dong-a has the biggest value 2.94 the class of 130 tons has 2.52 the class of between 75 and 100 tons has 2.30~2.35 and the class of between 500 and 1500 tons has 1.99~2.05. 5. Turning circle of stern trawlers Pusan 404 and Haelim 3 are measured as below according to rudder angles 5$^{\circ}$, 15$^{\circ}$, 25$^{\circ}$ and 35$^{\circ}$ respectively. Advances are 11.3~13.6, 6.0~7.1, 3.6~4.8 and 2.5~3.5 times of LPP respectively. Tactial diameters are 15.2~18.6, 6.9~8.0, 4.2~4.9 and 2.9~3.5 times of LPP. Purse seiner 111 Dong-a with rudder angle 35$^{\circ}$ has a good yaw with quick responsibility since its advance is 2.2~2.3 times of LPP and since its tactial diameter is 2.0~2.1 times of LPP. 6. In full ahead going of purse seiner 111 Dong-a, it takes about 2 minutes and 10.6 times of LPP from the reverse turning its engine into full astern to the ship speed 0. In its full astern going, it takes about 1 minute and 5.1 times of LPP from the reverse turning its engine into full ahead to the ship speed 0. In its full ahead going, it takes about 2 minutes and 50 seconds and 12.3 times of LPP from stopping its engine to the dead slow ahead speed 3.2 knots.

• Korea Science and Art Forum
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• v.37 no.4
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• pp.149-159
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• 2019

This research was started to identify the color status of signboards at the target site and suggest the direction of improvement for the signboard project in Dongsang-dong, Jongno-gil, a central area of the old city center of Gimhae. The area under study forms a depressed street atmosphere with old facilities, and is a typical type of old city center sign that needs to be rebuilt. The purpose of this study is to investigate prior research related to signage and similar signboard improvement cases, and then to identify the current status of colors by sorting out the casting, auxiliary and highlighted colors through the survey of the color of the signboard in the target area, and to propose a desirable direction for the future sign business based on the basis of these findings. This paper divided the target sections by industry and conducted a color analysis of signboards. The results and contents of the research are as follows. First, cast-colored signboards in general businesses showed a variety of primary color distributions with high L* values, on average, with high intensity and high chromaticity. Second, the auxiliary colors were mostly white or black in color-free, making a contrast between the casting colors. Third, the highlight was that a* value showed a high distribution in positive water plus and was mainly distributed in obsolescence, such as red or yellow, and color was used to reflect the characteristics of each store. However, the stores in the entire section lack unity because they were using colors that were higher in color than middle colors, which was causing the street's aesthetic look to be undermined. Based on the results of these studies, it is thought that the future color scheme for Gimhae's signature improvement project will limit the number of colors to a certain extent and give a sense of security and visual comfort to the use of colorlessness and obscurity around the representative colors of Gimhae.

• Journal of the Korean Magnetics Society
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• v.14 no.5
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• pp.196-200
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• 2004

In order to improve dendritic formation of Nd$_2$Fe$\_$14/B phase in the strip-cast Nd-Fe-B alloys that are frequently used for production of high energy sintered magnets, effect of small substitutional additives such as Cu (0.3～1.0 at. %) and Co (0.5～1.5 at.%) on the phase formation and microstructures of the strip-cast alloys based on Nd$\_$14/Fe$\_$80/B$\_$6/ were investigated. As the amount of Cu addition increased, formation of Nd$_2$Fe$\_$14/B dendrites along the direction normal to the strip surface was suppressed with the reduction of the strip thickness mainly due to the increase of fluidity of the melt. However, both the dendrites and their <001> preferred orientation along the direction normal to the strip surface were improved with the increase of the strip thickness as the amount of Co addition increased. The dendrites became finer after small amount of Cu or Co was added. While small copper additions tended to stabilize the formation of primary Fe, small cobalt additions suppressed it. When small amount of Zr was added, however, the dendrite structures were totally collapsed with excessive grain growth of Nd$_2$Fe$\_$14/B.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.4
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• pp.363-373
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• 2000

To understand and investigate chemical characteristics of thermal environment in the southwestern Paciflc, we have measured hydrological and chemical parameters such as temperature, salinity, transparency, pH, nutrients and hydrogen sulfide (H$_2$S). Samples were collected with CTD-casting at 12 station, in Manus Basin including PACMANUS, DESMOS and Susu Knolls, Hydrothermal systems consist of circulation zones where seawater interacts with rock, thereby changing chemical and physical characteristics of both the seawater and the rock. The altered seawater, called hydrothermal fluid, is injected back into the ocean from the hydrothermal vent fields and forms hydrothermal plumes. Consequently, we detected hydrothermal plume with transparency and sulfide anomalies at PACMANUS and Susu Knolls. Sulfide, as geochemical tracer of hydrothermal plume, ranged 0-3.31 ${\mu}$M, and averaged 0.63 ${\mu}$M in the study area. The height, flux and activity of the plume are affected by circulations in the deep water and the spread of plume follows along the isopycnal surface. Therefore the observed H$_2$S anomaly can provide important clue for the source location and it appears that the targestsource in the PACMANUS is aligned in the north-south direction.