• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.1-7
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• 2004

The polyethylene pipe can use semi-permanent because of the high corrosion resistance with chemical stability. In addition to, there is the merit that is an easy to establish and to maintain. However, as the reason that it is simply degraded when the polyethylene pipe was exposed to the outside, mainly it is used to lay under the ground with low-pressure gas transportation pipe. In this study, the nondestructive evaluation method was used to maintain the integrity of the polyethylene pipe. We simulated the various defects on the polyethylene pipes, and then the AE signal occurred according to the impact test of steel ball was evaluated by the acoustic emission method. From the results, the waveform and dominant frequency could be distinguishing from the defect shapes of polyethylene pipe. Especially, in the case of notch defect, the AE signals occur different by the angle and depth of the notch.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.341-348
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• 2016

The aim of this study is to suggest design requirements on the military barriers which are installed to reduce critical damage on protective facilities against sudden pin-point attacks caused by North Korean artilleries. For this purpose, site investigation and review of design drawings associated with barriers built in the contact areas are conducted. With identified data concerning barriers, the geometric modeling, which is used in the structural analysis, is performed. And then, the possible threat of North Korea is determined based on intelligence preparation of battlefields. Once the structural modeling and threat analysis are completed, structural damage on barriers and protective facilities are assessed in terms of impact, penetration, scabbing, and blast pressure effects. According to the analysis results, the thickness of barriers should be 450mm at least and current established barriers need to be structurally reinforced via sectional enlargement.

• Biomedical Science Letters
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• v.15 no.1
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• pp.9-15
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• 2009

Early age at menarche, which is indicator of early biological maturity, has been shown to be associated with increased adult body mass index. Early menarche has also been associated with many cardiovascular disease risk factors and metabolic syndrome. To evaluate the impact of menarche to cardiovascular risk factor, we assessed by age at menarche, brachial-ankle pulse wave velocity (baPWV), which represents arterial stiffness, in women with or without metabolic syndrome. The subjects recruited for this study were three hundred one women. Relatively early menarche and relatively late menarche were classified according to less than $50^{th}$ percentile for relatively early menarche, and great than the $50^{th}$ percentile for relatively late menarche. Subject were divided four group, 1) women who had not adulthood metabolic syndrome and relatively early menarche, 2) women who had not adulthood metabolic syndrome and relatively late menarche, 3) women who had adulthood metabolic syndrome and relatively early menarche, 4) women who had adulthood metabolic syndrome and relatively late menarche. Women who had a relatively early menarche with adulthood metabolic syndrome had significantly high levels of blood pressure, triglyceride, fasting insulin and homeostatic model assessment of insulin resistance (HOMA-IR) levels than women with late menarche with adulthood metabolic syndrome, and had significantly lower HDL-cholesterol levels. And also, women who underwent a relatively early menarche with metabolic syndrome had highest level of baPWV in adult. In this study we found effect of age at menarche on adulthood metabolic risk factors for cardiovascular disease (e.g., baPWV, insulin resistance, hyperlipidemia) in Korean women.

• Geomechanics and Engineering
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• v.20 no.3
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• pp.191-205
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• 2020

Soil shear strength parameters play a remarkable role in designing geotechnical structures such as retaining wall and dam. This study puts an effort to propose two accurate and practical predictive models of soil shear strength parameters via hybrid artificial neural network (ANN)-based models namely genetic algorithm (GA)-ANN and particle swarm optimization (PSO)-ANN. To reach the aim of this study, a series of consolidated undrained Triaxial tests were conducted to survey inherent strength increase due to addition of polypropylene fibers to sandy soil. Fiber material with different lengths and percentages were considered to be mixed with sandy soil to evaluate cohesion (as one of shear strength parameter) values. The obtained results from laboratory tests showed that fiber percentage, fiber length, deviator stress and pore water pressure have a significant impact on cohesion values and due to that, these parameters were selected as model inputs. Many GA-ANN and PSO-ANN models were constructed based on the most effective parameters of these models. Based on the simulation results and the computed indices' values, it is observed that the developed GA-ANN model with training and testing coefficient of determination values of 0.957 and 0.950, respectively, performs better than the proposed PSO-ANN model giving coefficient of determination values of 0.938 and 0.943 for training and testing sets, respectively. Therefore, GA-ANN can provide a new applicable model to effectively predict cohesion of fiber-reinforced sandy soil.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.1097-1103
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• 2011

Liquid droplet impingement erosion (LDIE) is caused by the impact of high-velocity droplets entrained in steam or air on metal. The degradation caused by the LDIE has been experienced in steam turbine internals and high-velocity airplane components (particularly canopies). Recently, LDIE has also been observed in the pipelines of nuclear plants. LDIE among the pipelines occurs when two-phase steam experiences a high pressure drop (e.g., across an orifice in a line to the condenser). In 2011, a nuclear power plant in Korea experienced a steam leak caused by LDIE in a pipe through which a two-phase fluid was flowing. This paper describes a study on the design change of a pipe affected by LDIE in order to mitigate the damage. The design change has been reviewed in terms of fluid dynamics by using the FLUENT code.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.31-38
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• 2016

Most of propellants that is used widely in the world release toxic gases such as methane gas and carbon dioxide during combustion which are noxious to the environment. This study established a synthetic process of a high nitrogen containing derivative of triazole, 4,5-bis(azidomethyl)-methyl-1,2,3-triazole (DAMTR), which can be applied as energetic plasticizer to environmental concerns. Also, the compound was characterized by NMR, IR spectroscopy, and physical properties such as glass transition temperature, melting point, decomposition temperature, density, impact sensitivity, viscosity and volatility were measured. In addition, the heats of formation (${\Delta}H_f$) and detonation properties (pressure and velocity) of DAMTR were calculated using Gaussian 09 and EXPLO5 programs.

• International Journal of Advanced Culture Technology
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• v.8 no.2
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• pp.1-5
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• 2020

As the world gradually advances to an aging society, the quality of human life is valued. Among them, 'quality of sleep' is very closely related to quality of life. Recently, Korea expanded health insurance coverage for "sleep disorders". Particularly, as the number of sleep multiple tests and prescriptions for sleep aids has increased rapidly, much attention has been focused on the related medical service environment. Therefore, this study looked at an in-depth interview of 11 hospitals to see what treatment delivery system is being established when the government applies health insurance for 'sleep disorders'. In conclusion, the organizations with the most average number of sleep polyp tests per day were found to have more sleep polyp labs (hardware) and more full-time specialists. Also, the polysomnography lab (hardware) and the specialist's full-time status (software) did not necessarily result in a "positive pressure regulator prescription" that can solve "sleep apnea" caused by "sleep ailments". Rather, it was found that the number of days of sleep multiple laboratories (hardware), the number of full-time specialists (software) or the specialty majors (software) had a greater impact. In particular, the higher the specialist's full-time personnel (software) index (=6.000), the higher the sleep-inducing agent prescription rate(=1.000), and the lower the specialist's full-time personnel (software) index (=1.000), the higher the sleep-inducer's prescription rate(= 0.010) Was low. In addition, even if the professional full-time personnel(software) index was the same (=1.000), the hospital type was lower as it was closer to the public hospital(=0.067) and higher at the specialized hospital (= 0.933). In the case of university hospitals, when the full-time specialists (software) are in the same condition (= 1.000), the frequency of use of the sleep laboratory (=1.000) and the sleep test rate (= 1.000) were all the same.

• Management & Information Systems Review
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• v.4
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• pp.349-374
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• 2000

With rapid advances on Interactive technology, and the growing popularity of the Internet, Internet shopping receives considerable attention in both the popular-press and academic journals. The Internet has enormous commercial possibilities. But it is a new and dynamic medium that poses special challenges for marketers. The revolutionary nature of the Internet mandates that established wisdom on consumer marketing along with marketing-mix strategies has to be reexamined and perhaps radically revised. In order to assist marketers in this endeavor it is critical to understand consumers' buying behaviors of Internet shopping. But research in this area still very much its infancy. This study examined previous researches of Internet shopping and developed conceptual framework of Internet shopping modes. Additionally, this study examined empirical investigation of Internet shopping. Preliminary results suggests that there are significant differences in individuals' perceptions of Internet shopping and traditional shopping modes. Various factors influences on consumers' buying behavior on Internet shopping. There are Individuals' factors(personality, lifestyle, prior experience, perceived risk etc), shopping mall factors(trust, vividness, security, promotion, etc), product characteristics(product category, brand, etc), situational factors(time pressure, locational constraints etc), social/cultural factors(Norms, importance of other peoples etc). Additionally, We conducted empirical study of the impact of the Internet on consumer shopping behavior. We gathered consumers' reactions via an open-ended survey using a sample of 90 shoppers. We related the reactions to the factors of consumers' satisfaction or dissatisfaction of the Internet shopping. Consequently, there are many questions regarding factors that might influence Internet shopping. From theoretical and practical perspectives, studies that examine these factors would seem to offer much to the discipline. This paper has attempted th provide insights and direction of future empirical examination of Internet shopping.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.864-870
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• 2017

The propellants are burned in the pre-burner of the staged combustion cycle engine, and the resulting hot gas drives the turbine, and the turbine operates the turbo pump. The burned gas passing through the turbo pump is supplied to the combustor at high temperature and high pressure, where the gas is supplied in an excess of fuel or an excess of oxidant depending on the amount of fuel or oxidant. When the cycle works at oxidizer-rich staged combustion, its metal pipe can ignite or explode by the impact of even small particles. In this study, we develop the powder combinations for anti-oxidation coating through the analysis of other coating materials and establish the coating process.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.2
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• pp.97-104
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• 2009

Ever increasing fuel prices, almost doubled in the last three years, and global pressure to reduce their environmental impact have been enforcing commercial vessel operators and designers to re-assess current vessel designs with emphasis on their propulsion systems and operational practices. In this paper the "Inclined Keel Hull (IKH)" concept, which facilitates to use larger propeller diameter in combination with lower shaft speed rates and hence better transport efficiency, is explored for a modern 3600 TEU container vessel with the aim of fitting an 13 % larger diameter propeller (and hence resulting 20% lower rpm) to gain further power saving over the similar size basis container ship with conventional "level keel" configuration. It appears that successful application of the "inclined keel Hull" concept is a fine balance amongst the maximum gain in propulsive efficiency, minimum increase in hull resistance and satisfaction of other naval architectural and operational requirements. In order to make the concept economically more viable, this paper concentrates on the fore body design with the possible combination of increase of volume in its fore body to recover the expected volume loss in the aft body due to the space for larger propeller and its low wave-making resistance to minimize the efficiency loss using a well-established optimization software.