• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.5
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• pp.638-644
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• 2016

In this research, theoretical study on empirical analysis method to estimate waterdrop's deformation by shock wave is presented. Flow field is calculated using theoretical and empirical relations. Waterdrop's deformation including movement, size, mass, and orientation is modeled using empirical relations derived from existing experimental data. Developed method is applied to specific flight examples with arbitrary flight speed and vehicle's configuration. The flight speed is assumed to Mach number of 2 and 4. The diameter of waterdrop is varied from 1 to 5 mm. Waterdrops along the stagnation line in front of hemispherical nose with the radius of 50 mm and around a cone-shaped side wall with the half angle of 20 degree are considered. It is found that the maximum diameter of the waterdrop is increased up to 2.77 times the initial diameter. The mass is conserved more than 66.7 %. In the case of a cone-shaped side wall, waterdrop's orientation angles defined from the flight direction when the Mach number is 2 and 4 are calculated as 33.0 and 25.6 degree, respectively.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.489-490
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• 2015

We present population synthesis models for the calcium II triplet (CaT), currently the most popular metallicity indicator, based on high-resolution empirical spectral energy distributions (SEDs). Our new CaT models, based on empirical SEDs, show a linear correlation below [Fe/H] ~ -0.5, but the linear relation breaks down in the metal-rich regime by converging to the same equivalent width. This relation shows good agreement with the observed CaT of globular clusters (GCs) in NGC 1407 and the Milky Way. However, a model based on theoretical SEDs does not show this feature of the CaT and fails to reproduce observed GCs in the metal-rich regime. This linear relation may cause inaccurate metallicity determination for metal-rich stellar populations. We have also confirmed that the effect of horizontal-branch stars on the CaT is almost negligible in models based on both empirical and theoretical SEDs. Our new empirical model may explain the difference between the color distributions and CaT distributions of GCs in various early-type galaxies. Based on our model, we claim that the CaT is not a good metallicity indicator for simple stellar populations in the metal-rich regime.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.4
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• pp.439-445
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• 2017

Plunging breaker slamming pressures on vertical or sloping sea dikes are one of the most severe and dangerous loads that sea dike structures can suffer. Many studies have investigated the impact forces caused by breaking waves for maritime structures including sea dikes and most predictions of the breaker forces are based on empirical or semi-empirical formulae calibrated from laboratory experiments. However, the wave breaking mechanism is complex and more research efforts are still needed to improve the accuracy in predicting breaker forces. This study proposes a semi-empirical formula, which is based on impulse-momentum relation, to calculate the slamming pressure due to plunging wave breaking on a sloping sea dike. Compared with some measured slamming pressure data in two literature, the calculation results by the new formula show reasonable agreements. Also, by analysing probability distribution function of wave heights, the proposed formula can be converted into a probabilistic expression form for convenience only.

• Journal of Distribution Science
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• v.12 no.10
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• pp.67-74
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• 2014

Purpose - This study analyzed how image affects customer trust and satisfaction in the online shopping mall market, which is becoming more competitive; future implications for customer management in online shopping malls were presented. Consumers visit and prefer a few shopping mall sites instead of many sites. Consumers do not visit sites that cannot provide trust and satisfaction. Therefore, establishing trust and satisfaction with differentiated image is essential for survival and growth. Specifically analyzing company image, shop image, and brand image, I studied how symbolic image, functional image, and empirical image affect satisfaction mediated by trust in the online shopping malls of hypermarket retailers. Research design, data, and methodology - To investigate the relationship between image and satisfaction of big box retailers' shopping malls in the online market, the study is based on analyzed data from questionnaires involving advanced research. From May 1st to 20th in the year 2014, a questionnaire survey targeting university students using big box retailers' shopping malls in Seoul was conducted. A total of 282 questionnaires were conducted, and 276 questionnaires were used for empirical analysis, excluding invalid data. Using the SPSS 21.0 statistics package, factor analysis and regression analysis were implemented, and effects of image on trust and satisfaction were presented. Results - First, symbolic image can affect satisfaction with only trust. Among 3 image factors, symbolic image exerts the most influence on trust; trust is important in coupling the medium to satisfaction. Second, functional image and empirical image affect satisfaction directly and indirectly with trust. Conclusions - As I classified the image of hyper market retailers' online shopping malls into symbolic, functional, and empirical image, I analyzed the effects of image on trust and satisfaction empirically. The results of the study and strategic implications are as follows. First, symbolic image can affect satisfaction with only trust. Among 3 image factors, symbolic image exerts the most influence on trust; trust is important in coupling the medium to satisfaction. The establishment of a distinctive symbolic image, such as the online shopping mall's loyalty, level of awareness, and special service, is needed. With the establishment of symbolic image, trust and satisfaction could be improved. Second, functional image and empirical image affect satisfaction directly and indirectly with trust. Especially, as functional image affects trust more than empirical image, setting and implementing a strategy for empirical image based on the right price, service, and convenience could raise trust and satisfaction. Empirical image affects trust and satisfaction substantially. Even though empirical image's influence on trust is lower than that of other three image factors, empirical image's influence on satisfaction is higher than symbolic image. Therefore, it requires a strategy for providing joyful use, and information research functions and distinctive use experience are important to improve satisfaction. This study analyzed image characteristics of hyper-market retailers' online shopping malls in the fast-growing online market; future strategic implications were presented.

• Journal of the Korean Society of Clothing and Textiles
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• v.15 no.3 s.39
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• pp.321-334
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• 1991

The main object of this study was to clarify the concept, scheme, an dimensions of the clothing evaluatie criteria, and to organize its theoretical framework accordingly. The research was carried out in tow ways. The first research was investigated by the critical evaluation of the existing literature, while the other research was investigated by an empirical survey study. The questionnaire was developed for the empirical study. The questionnaire was administered to 640 housewives living in Seoul area during the fall of 1988. Social wear was selected according to the defined times, place, and occasion. As a result of the literature study, the first research problem, the clothing evaluative criteria was loud to exist at three different level - benefit level, element level, and intemediate level -. The colthing evaluative criteria at the benefit le·eel were loud to include four different dimensions-fashionbility, status symbolism, practicality, and economy. The validity of the benefit dimensions was established by the empirical confirmation utilizing factor analysis technique.

• Korean Journal of Child Studies
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• v.38 no.2
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• pp.17-35
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• 2017

Objective: The purpose of this study was to explore research trends in childhood executive function in Korean academic journal articles. This study showed which population groups were studied, which factors of executive function were measured, and which domains were studied in the selected articels. Methods: A systematic review of empirical studies of childhood executive function published in Korean academic journals from 2006 to 2016 was conducted. Through searching the KERIS database, 60 empirical studies were selected for review. Results: The results of the analyses showed that the population group the most studied was normal young children and that factors of executive function most studied were inhibition, cognitive flexibility, and working memory. Conclusion: Based on this systematic review of empirical studies of childhood executive function, several suggestions for future research are addressed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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• pp.836-842
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• 2016

When an accident occurs in the nuclear power plant, the faulted information might mislead to the high possibility of aggravating the accident. At the Fukushima accident, the operators misunderstood that there was no core exposure despite in the processing of core damage, because the instrument information of the reactor water level was provided to the operators optimistically other than the actual situation. Thus, this misunderstanding actually caused to much confusions on the rapid countermeasure on the accident, and then resulted in multiplying the accident propagation. It is necessary to be equipped with the function that informs operators the status of instrument integrity in real time. If plant operators verify that the instruments are working properly during accident conditions, they are able to make a decision more safely. In this study, we have performed various tests for the fault detection sensitivity of an data-driven empirical model to review the usability of the model in the accident conditions. The test was performed by using simulation data from the compact nuclear simulator that is numerically simulated to PWR type nuclear power plant. As a result of the test, the proposed model has shown good performance for detecting the specified instrument faults during normal plant conditions. Although the instrument fault detection sensitivity during plant accident conditions is lower than that during normal condition, the data-drive empirical model can be detected an instrument fault during early stage of plant accidents.

• Journal of Navigation and Port Research
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• v.45 no.3
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• pp.165-172
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• 2021

Breaking wave is one of the important design factors in the design of coastal and port structures as they are directly related to various physical phenomena occurring on the coast, such as onshore currents, sediment transport, shock wave pressure, and energy dissipation. Due to the inherent complexity of the breaking wave, many empirical formulas have been proposed to predict breaker indices such as wave breaking height and breaking depth using hydraulic models. However, the existing empirical equations for breaker indices mainly were proposed via statistical analysis of experimental data under the assumption of a specific equation. In this study, a new Munk-type empirical equation was proposed to predict the height of breaking waves based on a representative linear supervised machine learning technique with high predictive performance in various research fields related to regression or classification challenges. Although the newly proposed breaker height formula was a simple polynomial equation, its predictive performance was comparable to that of the currently available empirical formula.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2586-2591
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• 2022

In the present work, we have irradiated the DI-BSCCO superconducting tapes with the 100 keV deuterium ions to investigate the effect of ion irradiation on their critical current (Ic). The damage simulations are carried out using the binary collision approximation method to get the spatial distribution and depth profile of the damage events in the high temperature superconducting (HTS) tape. The point defects are formed near the surface of the HTS tape. These point defects change the vortex profile in the superconducting tape. Due to the long-range interaction of vortices with each other, the Ic of the tape degrades at the 77 K and self magnetic field. The radiation dose of 2.90 MGy degrades the 44% critical current of the tape. The results of the displacement per atom (dpa) and dose deposited by the deuterium ions are used to fit an empirical relation for predicting the degradation of the Ic of the tape. We include the dpa, dose and columnar defect terms produced by the incident particles in the empirical relation. The fitted empirical relation predicts that light ion irradiation degrades the Ic in the DI-BSCCO tape at the self field. This empirical relation can also be used in neutron irradiation to predict the lifetime of the DI-BSCCO tape. The change in the Ic of the DI-BSCCO tape due to deuterium irradiation is compared with the other second-generation HTS tape irradiated with energetic radiation.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.38.1-38.1
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• 2013

We present the Yonsei evolutionary population synthesis (YEPS) models based on the high-resolution empirical spectral energy distributions (SEDs). We have adopted the MILES library in the optical wavelength, and our new models based on the MILES library show good agreements with our previous models presented in the YEPS I. The effect of hot horizontal-branch (HB) stars on the integrated properties of simple stellar populations (SSPs) is again confirmed by our models based on empirical SEDs. In addition, we have extended our empirical models to the near-IR wavelength and predicted the strengths of the calcium II triplet (CaT) and the Paschen triplet (PaT) based on the INDO-US and the Cenarro library. We find that the effect of HB stars and the age of SSPs on the CaT is almost negligible. On the other hands, the PaT models are very sensitive to the existence of hot stars, e.g., HB stars and young turn-off stars, and show very similar results with Balmer lines. Interestingly, the CaT distribution of GCs in NGC 1407, which is at odds with the optical (B-I) color distribution, can be explained by the unique feature of the CaT-[Fe/H] relations that show almost the same equivalent widths in the metal-rich regime. We will also discuss the impact of the second-generation populations on the strength of the CaT.