• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.98-106
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• 2020

This study examined the integrity of diesel engines for underwater vessels through failure analysis, analyzed the causes of abnormal diesel engine stoppage during building and examined the integrity of secondary damages. The diesel engine stoppage was analyzed by checking the temperature change of the piston before and after the abnormality and checking the damage. In addition, in order to analyze the secondary damage caused by the explosion, the tensile and compressive stresses transmitted to the crankshaft, the core part of the diesel engine, were calculated, and the stress distribution was examined through finite element analysis, but the crankshaft was designed by safety. It was confirmed that there was no damage to the crankcase even when the diesel engine was taken out of the ship and closely inspected. The integrity of the crank shaft was verified in advance for the occurrence of diesel engine emergency shutdown accidents through this research result. Therefore, the inspection and restoration were carried out to the minimum extent, and the quality of diesel engines was secured. This study is expected to be used as a reference for ensuring soundness in any future review of diesel engine quality problems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.687-693
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• 2016

The rapid turning and acceleration movement of a rotorcraft leads to a sloshing phenomenon in the fuel tank. Sloshing caused by rapid movement can affect the internal components by creating an excessive load. In severe situations, the resulting damage to the internal components and pipes can also lead to the tearing of the fuel tank itself. Therefore, to improve the survivability of the crew, the internal components of the fuel tank must be designed to retain their structural soundness during the sloshing phenomenon. In order to accomplish this, the sloshing load acting on the components first needs to be determined. This paper investigates the sloshing load applied to the internal components by performing numerical analysis for rotary-wing aircraft fuel tanks in the sloshing test. Fluid-Structural Interaction (FSI) analysis based on smoothed particle hydrodynamics (SPH) is conducted and the conditions specified in the US military standard (MIL-DTL-27422D) are employed for the numerical simulation. Based on this numerical simulation, by analyzing the load applied to the internal components of the fuel tank due to the sloshing phenomenon, the possibility of obtaining the design data by numerical analysis is examined.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.278-284
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• 2017

In this study, the heat input conditions suitable for the AZ61 magnesium alloy were derived by controlling the welding speed at a constant rotational speed. In addition, from an economic point of view, industry demands higher welding speeds. Therefore,the effects of the welding speed were studied. The rotational speed applied was 800rpm, and the welding speed was varied from 100 to 500mm/min to evaluate the behavior of the welded regions. Tensile and hardness tests were conducted to examine the mechanical properties. Optical microscopy was used to observe the microstructure and soundness of the welded regions. Defects were observed at the welded region when the welding speed was more than400mm/min. As the welding speed increased, the grain size of the stir zone decreased and the hardness tended to increase proportionally. When the rotational speed was 800 rpm and the welding speed was 200mm/min and 300mm/min, there wereno defects in the welded region and excellent mechanical properties were recorded. In addition, the joint efficiencies were 100.5% and 101.2%, respectively, and the ultimate tensile strength was similar to that of the base metal. Fracture of the tensile specimen occurred between the advancing side and stir zone, and the fracture location coincided with the region where the hardness decreased temporarily.

• The korean journal of orthodontics
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• v.41 no.1
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• pp.25-35
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• 2011

Objective: The purpose of this study was to optimize the thread pattern of orthodontic microimplants. Methods: In search of an optimal thread for orthodontic microimplants, an objective function stability quotient (SQ) was built and solved which will help increase the stability and torsional strength of microimplants while reducing the bone damage during insertion. Selecting the AbsoAnchor SH1312-7 microimplant (Dentos Inc., Daegu, Korea) as a control, and using the thread height (h) and pitch (p) as design parameters, new thread designs with optimal combination of hand p combination were developed. Design soundness of the new threads were examined through insertion strain analyses using 3D finite element simulation, torque test, and clinical test. Results: Solving the function SQ, four new models with optimized thread designs were developed (h200p6, h225p7, h250p8, and h275p8). Finite element analysis has shown that these new designs may cause less bone damage during insertion. The torsional strength of two models h200p6 and h225p7 were significantly higher than the control. On the other hand, clinical test of models h200p6 and h250p8 had similar success rates when compared to the control. Conclusion: Overall, the new thread designs exhibited better performance than the control which indicated that the optimization methodology may be a useful tool when designing orthodontic microimplant threads.

• Journal of Family Resource Management and Policy Review
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• v.13 no.3
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• pp.181-205
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• 2009

The purpose of this study is to investigate some Influencing factors related to the wealth perception and property increase of 519 women in Seoul. The research was conducted from the end of February 15 to the beginning of January 20, 2009. The figures obtained were analyzed by frequency, percentage, mean, x-test, t-test, F-test, chi-square, and Duncan's F-test with SPSS pc+ The major findings of who study are summarized as follows: l.There were significant differences between the wealth recognition (economic plan affirmative and negative perception of wealth) for women according to social and psychological variables; economic plans have a higher value for married women, older women, those who have followed a postgraduate university course, those with higher income and expenditure, higher life satisfaction, and high and middle satisfaction with their economic life. In particular, economic plans varied significantly according to expectation of wealth in old age, and future economic prospects in the middle group. 2. Increased wealth and economic according to social and psychological variables (marital status, age, education, income, expenditure, life satisfaction, satisfaction with economic life, expectation of wealth in old age, future economic prospects) were shown to be associated with the following methods of increasing property: use of savings banks (p<.001) showed a rate of deposit of 20%-40% (p<.001) saving and thrift was a practice (p<001) that was related to the cost of living; and education expenditure (p<.001) as a property preparation period was exhibited in women aged 25-30 (p<.001). 3. There were significant differences in the recognition of wealth according to strategies for increasing wealth. There were no significant differences between mean of property acquisition and point of expenditure or the property preparation period in the perception of wealth. The related variables in rate of deposits were under 20% according to economic plan and negative wealth perception. In contrast, in the middle and high group, the economic plan and negative wealth perception were 20%-40% in relation to the rate of deposits. Variables related to the action of saving and thrift and property acquisition were practiced in the low and middle group of affirmative wealth recognition and the high group of negative wealth perception. The high group for wealthrecognition and the low group for wealthnegation exhibited little savings, thrift, and property accumulation. Those variables which point an expenditure the cost of living were education expenditure in all groups of negative wealth perception. The women in the study practiced more soundness economic planning according to their increased wealth and economic strategy. This study suggests that women should have positive wealth perception in their lives.

• The Korean Society of Law and Medicine
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• v.18 no.2
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• pp.195-218
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• 2017

The increase in medical expenses for convalescent hospitals is increasing abnormally, which puts enormous burden on the National health insurance finances. This is a phenomenon that has been associated with the social phenomenon of rapid aging. The fact that the convalescent hospitals are paid the fixed amount per day for hospitalization became the incentive for some hospitals to use the patients as means of making money. And these hospitals intend to get regular care or take medicines at other hospitals in order to reduce medical expenses, even when the medical fee is paid. In order to prevent such financial leaks, the Health Insurance Review and Assessment Service adjusted the patient group for inpatients in a hospital with the above behavior, and then cut the cost of medical care benefits. However, Above decision was canceled by the court on the grounds that there was no basis rule. However, based on the above case, I think that it can be an opportunity to draw up the problem and to improve of the Medical Fee System of hospital. The modified medical fee system can strengthen the medical function of the convalescent hospital. In addition, it seems reasonable to exclude admission for "physically disabled group". Even if admission is allowed for the physically disabled group due to social needs, it should be excluded from the National health insurance for the fianacial soundness and the sustainability of the system.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.410-417
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• 2012

Currently domestic thermal and nuclear power plants are comprised of many type's condenser and steam generator tubes to produce the electricity of good quality. There are some methods to inspect these tubes in the event that several defects were discovered in these facilities. Among many non-destructive methods, we used guided wave to inspect the soundness of tubes, because this method is very fast to detect the defect and very simple to install the equipment and also, can inspect up to the long range at a fixed point. Also, this method has a drawback that does not detect a very small size defect. So, we made an effort to overcome this drawback through the experimentation and signal analysis according to the size and shape of the defect through the manufacture of various artificial cracks capable to generate within the small size tube in the study and we anticipate that these detect limits can be overcome along with the development of the signal processing and manufacturing technology of the sensor for the inspection.

• Communications for Statistical Applications and Methods
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• v.18 no.1
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• pp.119-130
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• 2011

This paper measures and analyzes the performance of insurance companies in Korea in respect to sustainable development and suggest strategic implications based on the analysis. The correlation, regression, ANOVA, and t-test are employed. The results of this study are summarized as follows. First, it shows tat social index is important in the life insurance industry; however, the environmental index, is important in the non-life insurance industry. Second, the result gained by regressing the size and financial soundness on the performance of sustainable development demonstrates that the size variable is statistically significant. It suggests that size is a necessary condition for sustainable development. Finally, ANOVA shows that the small and medium sized companies have a significantly poor performance compared to the large companies concerning the social index and reputation index in the life insurance industry. The small and medium sized companies in the non-life insurance industry exhibit a significantly poor performance compared to the large companies in respect to all the indexes, except for the social index. Therefore, the small and medium sized companies make every endeavor in the poor indexes to improve performance.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.144-154
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• 2017

The riparian vegetation is one of corridor type ecosystems, an ecotone and able to improve the ecological soundness by structural and functional link. And they act as habitats, sources and sinks of species, conduits, filters and barriers. This study was carried out to develop the vegetation model for the fluctuation areas of lake reservoirs consider of hydrologic and soil environments according to the vegetation structure of the reference ecosystem. To develop the case study, 2 sites within 10degree slope of the Daecheong Lake were selected. The riparian vegetation models were built by the results of GIS analysis, remote satellite analysis, field survey results, consider of water level, flooded frequency, soil and topographic index, land cover or land use etc. 1) study area varied from FWL to -5m of NFWL, 2) slope 10% below, 3) vegetations flooded below 100days yearly are Salix koreensis, Salix chaenomeloides, Salix gracilistyla, 4)land cover type classified wildlife grassland, abandoned paddy field, cropland according to landuse (or landcover), 5)finally model was constructed as ecological landscape forest. The model designs were suggested by 2 types in Daecheong lake reservoir. The model for the riparian vegetation corridors could be the basic and useful data to improve the ecological and landscape properties.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.2
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• pp.122-128
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• 2005

A feasibility study on the application of self?shielded flux cored arc welding to the on-site SM520 steel bridge box fabrication for express trains and high way construction instead of gas-shield flux cored arc welding was conducted in terms of weld soundness, mechanical properties, toughness and microstructures. All welded specimens made with the self?shielded FCAW process were tested by magnetic particle and ultrasonic techniques and they were found to be sound. All multipass weld specimens made with both self-shielded and gas-shielded FCAW processes showed yield and tensile strengths of $462{\sim}549\;MPa$ and $548{\sim}640\;MPa$, respectively. The impact values of Charpy V-Notch weld specimens also met with the required value of 40J at $-20^{\circ}C$. The hardness values of the top area of weldments were higher than those of the bottom area because of higher residual stresses in the near surface. It was found that welding characteristics of SM520 steel by the on-site welding conditions with self-shielded FCAW showed almost equivalent to those by gas-shielded FCAW in terms of sound welds, mechanical properties and microstructure.