• International Journal of Reliability and Applications
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• v.10 no.1
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• pp.17-32
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• 2009

The aim of this work is to generalize reliability equivalence technique to apply it to a system consists of n independent and non-identical components connected in series system, that have mixing constant failure rates. We shall improve the system by using some reliability techniques: (i) reducing some failure rates; (ii) add hot reduncy components; (iii) add cold reduncy components; (iv) add cold reduncy components with imperfect switches. We start by establishing two different types of reliability equivalence factors, the survival equivalence (SRE), and mean reliability equivalence (MRE) factors. Also, we introduced some numerical results.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.737-749
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• 2016

Recently perovskite materials with much cheaper cost and marvellous optoelectronic properties have been studied for next generation LED display devices overseas. Technology development trends of inorganic $CsPbX_3$(X=halogen) based LEDs (PeLEDs) with assumed high stability were investigated on literature worldwide. It was found that syntheses methods of these nanocrystals (NCs, mainly quantum dots, QDs) made great progress. A new room temperature synthesis method showed outstanding PL (photoluminescence) properties such as high quantum yield (QY), narrow emission width, storage stability comparable with, or often exceeding those of conventional hot injection method and CdSe@ZnS type inorganic colloidal QDs. PeLEDs with shell layers might be more promising, indicating urgent real research start of this solution processing technology for small businesses in Korea.

• International Journal of Advanced Culture Technology
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• v.12 no.1
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• pp.26-33
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• 2024

With the start of COVID-19 in 2020, the MBTI test became popular among Korean young generation and then developed into a nationwide hot topic. This paper aims to investigate the characteristics of the MBTI popularity in Korea and the public opinions toward this phenomenon. With the analysis of the reports contents, 231 news reports related to MBTI were selected from KINDS (Korea Integrated News Database System) as research samples. The general attitude of the media towards MBTI tests and the reasons for the formation of positive and negative evaluations will be discussed from three perspectives: media attention, media attitudes and cognitive sources. The research finds that the increasing interest in MBTI among the younger generation in Korea is driven by a post-epidemic desire for self-exploration, emotional planning, and online group affiliation. MBTI has gained quasi-scientific status, similar to horoscopes, influenced by celebrities and a substantial fan base in online communication. While widely used for entertainment and social currency, there are concerns that extensive labeling may unconsciously impact individuals' self-perception and hinder the development of a holistic and objective cognitive framework.

• Journal of The Korean Society of Grassland and Forage Science
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• v.11 no.4
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• pp.203-208
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• 1991

This experiment was carried out to compare the effects of summer temperature and nitrogen application on carbohydrates and fiber contents in orchardrass stubble grown in the cool summer year, 1980 and in the hot summer year, 1984. For this study, the contents of carbohydrates, neutral detergent fiber (NDF), acid detergent fiber(ADF) and hemicellulose in orchardgrass stubble were investigated. 1. Total water soluble carbohydrates(TSC) in orchardrass stubble were accumulated during the period of cool season and were declined when the weather was hot and dry. The reserve level of those were decreased when a new leaf emerged after the start of plant growth and then were increased as the plant was in full flourish. 2. The reserve of carbohydrate content in orchardgrass stubble was about twice times higher in cool summer year than that in hot summer year, and the reserve rate of carbohydrates showed to be fast in cool summer year. When the nitrogen fertilizer applied, the content of TSC in orchardgrass stubble more lowered but not significantly different(p<0.05). 3. The contents of NDF, ADF and hemicellulose in orchardgrass stubble in cool summer year were not significantly different from those in hot summer year. These contents showed also no significant difference among different levels of nitrogen applications. 4. The relationship of carbohydrate, NDF, ADF and hemicelluose contents according to the levels of nitrogen applications were negatively correlated in cool summer year. But there was no consistency in hot summer year.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.6
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• pp.475-482
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• 2014

This paper presents the results of an experimental feasibility study on low-temperature differential Stirling engines with water spray heat transfer. The water spray enhances the efficiency of the heat transfer from heat sources to the engine and reduces the performance degeneration due to the dead volumes of conventional heat exchangers. A test Stirling engine was developed and an experiment was conducted to determine the characteristics for the initial start-up, steady-state operation, and power output for various flow rates and temperatures of hot supply water. The test results showed that larger flow rates led to reductions in the minimum working temperature of the hot water at start-up. During a series of steady-state operations, higher flow rates and temperatures increased the working speed. Furthermore, the work per cycle and power output were also increased. Eventually, the test Stirling engine had a power level of 0.05 W. Based on this, further research will be conducted to obtain a higher power output and investigate various applications.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.2
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• pp.6-11
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• 2000

In the pressurized propellant feed system of liquid rocket, feed pressure is decided chamber pressure of normal combustion state. However, during ignition period the initial chamber pressure is atmosphere. So, it may have overflow, hard-start and even critical damage of engine. This paper proposes an improved propellant feed system for the stable combustion of liquid rocket. Hot test were already performed to verify the presented propellent feed system. The proposed propellant feed system uses two steps - pre and main combustion - to prevent large pressure increase and uses cavitating venturis for stable flow rate in whole combustion. This system feeds the flow rate lesser than the designed flow rate, so combustion pressure reached pre-combustion pressure. Cavitating venturis offer unique flow control capabilities at normal and abnormal combustion state, because flow rate is solely dependent on upstream absolute pressure and fluid properties, but independent on downstream condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.279-285
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• 2011

We perform a numerical study to determine the time of onset of natural convection in a transient hot wire (THW) device for measuring the thermal conductivity of nanofluids. The samples used in this simulation are water-based $Al_2O_3$ nanofluids with volume fractions of 1%, 4%, and 10%, and the properties are calculated by theoretical models and experimental correlations. The THW apparatus using coated wire is modeled by the control-volume-based finite difference method, and the start of natural convection is determined by observing the temperature rise of the wire under a gravity field. The onset time is 11.5 s for water and 41.6 s for water-based $Al_2O_3$ nanofluids predicted by Maxwell thermal conductivity model with a 10% volume fraction. We confirm that the onset time of natural convection of nanofluids in the cylinder increases with the nanoparticle volume fraction. We suggest a correlation for predicting the onset time on the basis of the numerical results. Finally, it is shown that the measurement error due to natural convection is negligible if the measurement using the transient hot wire method is completed before the onset of natural convection in the base fluid.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1909-1915
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• 2010

The material properties of gas turbine components change during the daily start/stop thermal cycle because of exposure to the hot combustion gas. Recently, single-crystal Ni-based superalloys have been used to manufacture many hot-gas components for gas turbines. However, the user needs to depend on the manufacturer for maintenance issues because of the lack of data required for predicting blade life and material degradation. In this study, we investigate the time-dependent degradation of first-stage blades at various operating facilities to collect the basic data for life assessment and damage analysis. The blade material is a single-crystal Ni-based superalloy, CMSX-4, and the EOH (equivalent operating hours) are 25,000 and 52,000, respectively. We prepared the test specimen directly from used blades and carried out mechanical tests and microstructural observations.

• The Korea Journal of Herbology
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• v.32 no.6
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• pp.31-39
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• 2017

Objectives : Menopausal symptoms are characteristic symptoms which are occur in women before and after menopause. In Western medicine, hormone therapies are mainly used but patients show reluctance because they exhibit serious side effects. In Oriental medicine, there are also limits to the treatment. So I tried to find a new easily accessible treatment. I performed the experiments to verify the effect of natural dyed apparel with Indigo and Schisandra fruit. Methods : This experiment was performed on 30 women who were experiencing menopausal symptoms. We checked the participant's general condition through questionnaire and physical condition with inbody test and made natural-dyed living suit style dresses. We asked the women to wear the apparel for four weeks. They checked for changes in symptoms weekly with kupperman's index. Results : The main symptoms of participants are sweating, hot flushes, joint pain. After wearing of the apparel, there were decreased hot flushes, sleep improvement, psychological stability etc. According to the kupperman's index, patients with mild symptoms were 13.3% at first week to start the experiment but four weeks later, patients with mild symptoms were increased to 50%. On the other hand, patients with severe symptoms were decreased 33.3% to 6.7%. In the test results, there was a significant decrease in 1, 2 and 3 weeks, there was a decrease in 4 weeks but no significance in the figure Conclusion : Natural dyed apprel with Indigo and Schisandra fruit was effective on treating women who were experiencing menopausal symptoms.

• Journal of Korean Medical classics
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• v.6
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• pp.41-53
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• 1993

The theory of 4 great doctors in Geum Won era has been considered as a most scientific medicine after SangHanRon of Jang, Jung Kyung. And it influence for all the later medical theory and practice. I have found a common points between their Fire and Fever pathology and constitutional pathology of Li, Je Ma. The results obtained are as follows. 1. On the Viewpoint of medical history, there is common points in the fact that the start of Geum Won 4 great doctor' principle had been drived from awakening of the abuse of warm and hot herbs based on Hwa Je Guk Bang in the last stage of Song dynasty, and that the appearance of Sa Sang medicine was from the scientific reflection against the currency of the animation by warm herbs which was popular in the Jo Sun dynasty. 2. The theory of Fire and Fever pathology of 4 great doctors has been fixed in the principle of Cold and Fever pathology of viscera and bowel in the Sa Sang medicine. 3. The pathological meaning of 'internal fire' in the conculusion by 4 great doctors has got scientific fruit by Sa Sang medicine in its theory of four constitutional psychology and the formation of four visceras. 4. It is considered that the study of DongUiSuSeBoWon is needed for the relation with former medical theories.