• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.335-342
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• 2007

A propulsion and lift shafting system in an air cushion vehicle is flexible multi-elements system which consists of two aeroderivative gas turbines with own bevel gears, four stage lift fan reduction gear, two stage propulsion reduction gear air propellers and high capacity of lifting fans. In addition, the system includes the multi-branched shafting with multi-gas turbine engines and thin walled shaft with flexible coupling. Such a branched shafting system has very intricate vibrating characteristics and especially, the thin walled shaft with flexible couplings can lower the torsional natural frequencies of shafting system to the extent that causes a resonance in the range of operating revolution. In this study, to evaluate vibrational characteristics some analytical methods for the propulsion and lift shafting system are studied. The analysis, including natural frequencies and mode shapes, for five operation cases of the system is conducted using ANSYS code with a equivalent mass-elastic model.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.2
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• pp.219-226
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• 2017

These days, the great part of design processes in the field of ship or offshore manufacturing are planned and implemented using the CAD system customized for shipbuilding companies. It means that all information for design and production could be extracted and reused at the other useful fields which need cost considerable time and efforts. The typical example is the field of welding material quantity evaluation which is demanded during the construction of ship or offshore structures. The proper evaluation of welding material to be used and the usage of them at the stage of schedule planning are mostly important to achieve the seamless process of production and costing in advance. This study is related to the calculation of welding length and needed welding material quantity at the stage of design completion utilizing the customized CAD system. The calculated welding material quantity would be classified according to welding posture, assembly stage, block, bevel and welding type so as to improve the accuracy of total cost evaluation. Moreover it is possible to predict the working time for welding operation and could be used efficiently for the cost management using the results of this research.

• Journal of the Semiconductor & Display Technology
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• v.8 no.1
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• pp.1-5
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• 2009

Typically, single-wafer wet etching is done by dispensing chemical onto the front and back side of spin wafer. The wafer is fixed by a number of chuck pins, which obstruct the chemical flow and would result in the incomplete removal of the remaining film, which can become a source of contamination in the next process. In this paper, we introduce a novel design of wafer chuck, in which chuck pins are groupped into two and each group of pins fixes the substrate alternatively. Two groups of chuck pins fix the high-speed spin substrate with non contact method using a magnetic material. The actual process has been executed to observe the effectiveness of this new wafer chuck. It was found that the new wafer chuck performed better than the conventional wafer chuck for removing the remaining film from the bevel and edge side of substrate.

• Journal of Welding and Joining
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• v.25 no.6
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• pp.44-52
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• 2007

A welding process of a lifting lug for lifting heavy objects is one of the important welding processes directly related to the safety in shipbuilding. Welding a lifting lug is done in the manually and takes about forty minutes. Working environment for the lifting lug welding is very poor due to an radiant heat and a harmful fume. The purpose of this study is to develop methods of multi-pass welding using the lifting lug welding robot system. This study shows robot welding methods to achieve proper corner, straight and connection welding and an effectiveness of application.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.6
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• pp.270-274
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• 2019

In this study, simulation structure analysis was performed for the differential gear system for passenger cars as a prerequisite for the design of the balancing module. The differential gear system was modeled by using CATIA and simulation structure analysis was performed using ANSYS software. The material of the modeled differential gear system uses the mechanical properties of S45C (Q&T). In the structural analysis of the differential gear, the areas where the maximum stress and the maximum strain occurred can be identified. The maximum stress and maximum strain occurred in the pitch circle of the bevel gear. In evaluating the safety factor, it was found that sufficient safety factor was secured. Based on the analysis results for the differential gear, it is expected that it will be a good reference if we design the balancing module device.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.72-79
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• 2021

A circular saw is an effective tool for cutting glass and carbon-fiber hybrid composites. This study investigated tool wear and cut quality when reusing saw blades. The carbide saws wear four times faster than the new ones, and polycrystalline diamond (PCD) is very resistant to tool wear, except at the end of its lifespan. The cut cross-section quality is affected by the blade type, tool wear, and spindle speed. Alternate top bevel (ATB)-type blades are suitable for cutting fiber-reinforced plastics, but triple-chip grind (TCG)-type blades are unsuitable because they cause fiber-pullout defects. Tool wear and low spindle speeds increase the occurrence of arc scratches, due to the rear saw blade. A microscopic examination showed that the burr, which is a mixture of fiber chips and epoxy matrix, was bonded on top, and glass-fiber delamination occurred on the bottom glass-fiber-reinforced polymer (GFRP) surface.

• Journal of Ocean Engineering and Technology
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• v.32 no.6
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• pp.518-526
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• 2018

As a new technical approach, this paper introduces a method for improving an electrically propelled outboard motor in consideration of the driving system applied to an electric-propulsion boat with solar cell energy. The most efficient model for a drive shaft, propeller shaft, and bevel gear was suggested and examined with respect to the results of test operation in prototype mode. Furthermore, this research included a performance evaluation of the manufactured prototype to acquire the purposed quantity value and the development items. After manufacturing the desired prototype of an electrically propelled outboard motor, the maximum sail time, thrust force, noise, and weight were evaluated in a performance test. An additional test in relation to the maximum sail speed (knots) of the completed prototype was conducted using a sea trial evaluation to acquire the optimum quantity.

• International Journal of Industrial Entomology and Biomaterials
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• v.2 no.1
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• pp.27-35
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• 2001

This study was carried out to investigate the mineral content in the regional, varietal and seasonal mulberry leaves. On average, mulberry leaf samples contained minerals in the order of potassiumi phosphorus, calcium, magnesium, iron and so on (2.494 g/100 g, 2.255 g/100 g, 1.835 g/100 g, 0.627 g/100 g, 0.0245 g/100 g DW, respectively). Calcium content was 19-fold and 4-fold higher than that of green tea and spinach, respectively, suggesting that mulberry loaves appear to be a calcium-rich food source. In the comparison of geographic samples of Cheongilppong variety, calcium bevel was highest in Youngchun sample (2.477 g/100 g) and highest potassium level in Suwon sample (2.962 g/100 g). In the geographic samples of YK209 variety, Jinju-City sample was highest in calcium content (1.509 g/100 g). Among wild mulberry loaves collected from Cheju Island and Tsushima, potassium level was highest in Bongge-dong, Cheiu City (3.865 g/100 g) and calcium level in Mitshshima Town, Tsushima (2.948 g/100 g). In the comparison of varietal samples collected in Suwon at the mulberry field of Dept. of Sericulture & entomology, Shinkwangppong variety was highest in the potassium levels although Keryangppong and Shinkwangppong were higher in calcium revel. In the comparison of seasonal samples of Cheongilppong, there was a rough trend of increase in some minerals up to July (e.g., calcium rind )potassium). Finding of the highest calcium and potassium contents in the wild mulberry (3.865 g/100 g and 2.948 g/100 g, respectively) rather than in the cultivated ones warrant that more focus should be paid to wild mulberry leaves to utilize their minerals effciently.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.4
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• pp.643-652
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• 1998

This paper presents the characteristics of a relay station antenna with the newly designed back-plate structure which is composed of the U-shaped metal plate for suppression of the back lobe by edge diffraction. The back lobe level of the conventional type was about -20 dB in the -z direction ( 180 ) . In order to improve the characteristics, the U-shaped mesh type metal plate is considered, where the design condition of the model antenna satisfies the wide null point angle range with the back lobe level of -30 dB below in the -z direction. The design parameters with the minimum back lobe level such as the dipole length, the distance between dipole elements and the back plate size have been found by using the released NEC Win Pro code. The calculated and measured back lobe Bevel of model antenna have been obtained 48.48 dB and -45 dB at 325 MHz, respectively.

• Journal of Biomedical Engineering Research
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• v.13 no.4
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• pp.339-352
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• 1992

A numerical simulation of the steady and pulsatile flow across the end-to-side anastomosis was performed In order to understand the role of flow dynamics in the preferential bevel opment of distal anastomotic intimal hyperplasla. The finite element technique was employed to solve two-dimensional unsteady pulsatile flow in that region. The results of the steady flow revealed that low shear stresses occur at the proximally occluded host artery and at the recirculation region in the Inner wall just distal to the toe region of the anastomosis. The nor- mal;zed wall shear rate was increased, as was the recirculation zone size in the host artery of the by-pass graft anastomosis, with increased anastomotic junction angle. In order to min imize the size of the low wall shear region which might result in the intimal hyperplasia in the by-pass graft anastomosis, a smaller anastomotic junction angle is recommended. The pulsatile flow simulation revealed flow that regions of low and ascillating mali shear do exist near the anastomosis as In the steady simulation. The shift of stagnation point depends on the pulsation of the flow. As the flow was accelerated at systole, the stagnation point moved downstream, disappered at early diastole and reappeared during late diastole. Low shear stress was also found along both walls of the occluded proximal artery. However, the diastolic flow behavior is quite different from the steady results. The vortex near the occluded artery moved downstream and inwardly during late systole, and disappeared during diastole. Recirculations proximal to the toe and heel regions were significant during diastole. Shear stress oscillation was found along the opposite wall. The results of the present study revealed that tow shear occurs at the proximally occluded host artery aud the recirculation region in the inner wall Just dlstal to the toe region of the anastomosis. The present study suggested that the regions of fluctuated wall shear stress wit flow separation is correlated with the preferential developing regions of anastomosis neointial fibrous hyperplasia.