• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.69-77
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• 2002

To acquire the dynamic response and design the controller of the airship, the longitudinal motion of the airship with respect to the vertical gust, which is the nonlinear system, was studied. The effects of the apparent mass and moment of the airship delay the dynamic response and the settling time, which are slower than those of conventional airplanes. The current object of the airship is designed to cruise at 500~1000m altitude. At that height, the atmospheric conditions are generally unstable by wind gust. In this paper, it has been studied for the case of vertical gust, since the apparent mass effects are dominant in has been studied for the case of vertical gust, since the apparent mass effects are dominant in that plane. In addition to the study of the dynamic responses of the airship, the controller was designed using the PID-controller. When the gust was applied, airship responses were recovered of equilibrium states. However, it takes too ling time for recovery and the speed of airship is reduced. So, the aim in this paper was to fasten the recovery speed and to get back the cruising velocity. The control parameters were determined from the stability mode analysis, and the control inputs were the thrust and the elevator deflection angle.

• Journal of Biomedical Engineering Research
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• v.20 no.2
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• pp.173-182
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• 1999

Contrast-enhanced CT has an important role in assessing liver lesions, the optimal protocol to get most effective result is not clear. The mein goal when deciding injention protocol is to optimize lesion detectability with rapid scanning when lesion to liver contrast is maximum. For this purpose, we developed a physiological model of the contrast medium enhancement based on the compartment modeling and pharmacokinetics. Blood supply to liver is achieved in two paths. This dual supply characteristic distinguishes the CT enhancement of liver from that of the other organs. The first path is by hepatic artery and to second, by portal vein. However, it is assumed that only gepatic artery can supply blood to hepatocellular carcinoma(HCC) compartment, thus, the difference of contrast enhancement is resulted between normal liver tissue and hepatic tumor. By solving differential equations for each compartment simultaneously using the computer program Matlab, CT contrast-enhancement curves were simulated. The simulated enhancement curves for aortic, hepatic, portal vein, and HCC compartments were compared with the mean enhancement curves from 24 patients exposed to the same protocols as the simulation. These enhancement curves showed a good agreement. Furthermore, we simulated lesion-to-liver curves for various injection protocols, and the effects were analyzed. The variables to be considered in the injection protocol were injection rate, dose, and concentration of contrast material. These data may help to optimize scanning protocols for better diagnosis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.2
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• pp.149-158
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• 1998

The SAR patterns of biological objects contacted with coaxial waveguide antennal has been investigated, in which the biological object was modeled by a homogeneous and four-layered lossy human body. We derived the finite-difference time-domain(FDTD) algorithm and equation of MUR and generalized perfectly matched layer(GPML) ABCs in cylindrical coordination. The coupling between coaxial waveguide antenna and a biological object was analyzed by use of MUR and GPML ABCs in the FDTD method to obtain the absorbed power patterns in the media. The specific absorption rates (SAR) distribution which was corresponding to the temperature distribution was calculated in each region by use of the steady-state response in the FDTD method. The SAR patterns of the FDTD method using MUR absorbing boundary conditions(ABCs) was compared with those of the FDTD method using GPML ABCs. The comparison exhibits that the penetration depth of the SAR patterns using MUR ABCs is deeper than that of the SAR patterns using GPML ABCs because of loss in free space. However, the spread in the lateral directions of the SAR patterns using GPML ABCs is smaller than of the SAR patterns using MUR ABCs.

• Food Science and Preservation
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• v.14 no.4
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• pp.385-393
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• 2007

Much research is conducted on the biological activities of medicinal herbs, traditional plants, and agricultural products, cultivated in Korea. This study focused on optimization of hot-water extraction methods for such products, by analyzing and monitoring extraction characteristics using a response surface methodology. We found that the total phenolics contents, electron-donating abilities, and nitrite-scavenging abilities of extracts were significantly affected both by the solvent used for extraction, and by the nature of the particular herb or plant under study. The extraction efficiencies of valuable ingredients such as alliin, allicin, and total thiosulfinate, were greatly affected by extraction temperature, but not by extraction time or the solvent used. We elicited a regression formula for each variable. We first entered the optimal values of all extraction conditions giving active ingredients into the model. Next, we entered the optimal values of all extraction conditions favoring the retention of valuable antioxidant characteristics. Finally, we entered processing factors into the model. Overall, the optimal extraction was at $80^{\circ}C$ for 3.5 hr with 8.5 ml of solvent/g of sample. The predicted values of each variable were similar to the actual values.

• Journal of Digital Convergence
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• v.15 no.7
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• pp.445-456
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• 2017

Mobile healthcare apps should be paid more attention not just as software, but also as significant health information providers. We examine the impact of psychological factors (e,g., instrumental efficacy, informational efficacy, health information orientation, playfulness, and responsiveness) on intention to continuous use of mobile healthcare apps. Based on an expanded technology acceptance model (TAM II), this study examined the effects of psychological factors influencing the usage of mobile healthcare apps. The results showed that informational efficacy and instrumental efficacy influenced intention to use through perceived ease of use and perceived usefulness. Playfulness influenced intention to continuous use directly as well as indirectly through perceived ease of use and perceived usefulness. Health information orientation and responsiveness influenced intention to continuous use through perceived usefulness. This study suggests the need for adopting instrumental, informative perspectives and playfulness in contemporary health research and production of mobile healthcare apps.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.153-159
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• 2005

Recently, various novel numerical models based on Navier-Stokes equation rave been developed for calculating wave motions in the sea with coastal or ocean structures. Among those models, Volume Of Fluid (VOF) method might be the most popular one, and it has been used for numerical simulations of wave motions including complicated phenomena of wave breakings. VOF method, however, needs enormous computation time and large computational storage memories in general, thus it is practically difficult to use VOF method for calculations in the case of random waves because long and stable computation ( e.g. for more than 100 significant wave periods) is required to obtain statistically meaningful results. On the other hand of the wave motion is potential motion, Boundary Element Method (BEM), which is a much faster and more accurate method than VOF method, am be effectively used. The aim of this study is to develop a new efficient model applicable to calculations of wave motion and/or wave-structure interactions under random waves. To achieve this, a strictly combined BEM-VOF model has been developed by making the best use of both methods' merits; VOF method is used in a restricted fluid domain around a structure where complicated phenomena of wave breakings may exist, and BEM is used in the other domains far from the disturbance where the wave motion may be assumed to be potential. The verification of the model was performed with numerical results for Stokes'5th order wave propagation and a random wave propagation.

• Journal of the Korean Society of Child Welfare
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• no.32
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• pp.69-97
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• 2010

The purpose of this study is to investigate the effects of high school students' academic problems such as academic stress and low academic achievement on suicidal ideation and the mediating effects of individual-level risk factors (e.g., depression, aggression) and protective factors (self-esteem, emotion regulation) on the relationship between academic problems and suicidal ideation. This study used data of three waves(2005-2007) from the Korea Youth Panel Survey(KYPS). The analyses were conducted on 2,093 academic high school students, who participated in this panel study. The results from structural equation modeling show that academic stress has positive effects on depression and aggression, but negative effect on self-esteem. Low academic achievement has positive effect on aggression but negative effect on self-esteem. Depression and aggression as individual-level risk factors have positive effects on suicidal ideation. In contrast, self-esteem and emotion regulation as individual-level protective factors have negative effects on suicidal ideation. The relationship between academic problems and suicidal ideation is mediated by depression, aggression, and self-esteem. Based on the study findings, practice implications for youth welfare are discussed to screen high-risk youths and to prevent adolescent suicide in advance.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.5
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• pp.1123-1132
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• 2012

Many domestic organizations are introducing and operating various information security management systems capable of coping with technical, administrative, and legal issues comprehensively and systematically, in order to prevent various infringement incidents such as personal information disclosure and hacking preemptively and actively. However, empirical analyses regarding the extent to which an information security management system contributes to information security performance have not been fully conducted, even though enterprises and organizations are actively introducing such systems in order to achieve their information security objectives as a part of their organizational management activities in line with their respective business, by investing considerable effort and resources in developing and operating these systems. This approach can be used to apply, develop, and operate the information management system actively within an organization. this study focused on analyzing how each specific phase of the information security management system affects information security performance, compared with previous studies, which generally focus on the information security control item in analyzing information security performance. The information security management system was analyzed empirically to determine how the Security PCDA cycling model affects information security performance.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.3
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• pp.145-151
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• 2023

In order to extend shelf life for rockfish fillets by modified atmosphere packaging (MAP), different package atmospheres were compared in the product quality preservation. Firstly, CO₂ solubility was measured at 0, 5, 10, and 15℃ to be incorporated into the mathematical model to predict the volume and CO₂ concentration of the package at expected storage temperature. The CO₂ solubility given in Henry's constant decreased with temperature to be fitted with a linear equation. Then air packaging as control and four MAP conditions of 100 g fillets were prepared and stored for duration of 5 days at 10℃ to compare them in the quality preservation effect. Four MAP conditions employed were CO₂(60):O₂(30):N₂(10), CO₂(60):O₂(0):N₂(40), CO₂(30):O₂(30):N₂(40) andCO₂(30):O₂(0):N₂(70). MAP conditions with high CO₂ concentration inhibited total aerobic bacteria, and the conditions containing O₂ led to low TVB-N. MAP of CO₂(60):O₂(30):N₂(10) was found to be the best condition for rockfish fillet preservation considering total aerobic bacteria growth and nitrogenous volatiles production.

• Korea Journal of Hospital Management
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• v.29 no.2
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• pp.57-79
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• 2024

Purpose: The present study identified the determinants in the development of intrapreneurial intention in small and medium-sized local hospitals. A careful literature review led to the development of a conceptual model which identified two types of employee competence-individual competence and managerial competence-to influence intrapreneurial orientation positively. It was hypothesized that intrapreneurial orientation predicts intrapreneurial intention and is mediated by intrapreneurial commitment. Methodology/Approach: The target population was chosen from two medical institutions of 'D' Hospital and 'E' Geriatric Hospital in Changwon City, South Korea. Samples were collected from 299 respondents who completed a structured questionnaire. Findings: The results from a structural equation modeling statistical analysis indicated that (1) individual competence and managerial competence positively and significantly predict intrapreneurial orientation, (2) intrapreneurial orientation positively and significantly influences intrapreneurial intention, (3) intrapreneurial commitment partially mediates the relation of intrapreneurial orientation to intrapreneurial intention, and (4) the mediation effect of intrapreneurial commitment was significant in the medical-personnel group, but not in the non-medical group. Practical Implications: Overall findings from the present work provide vital insights into understanding the preconditions for developing employee intrapreneurship in small and medium-sized local hospitals.