• Journal of Drive and Control
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• v.14 no.4
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• pp.23-28
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• 2017

Time-delay control with internal model (TDCIM) is the controller for robot manipulators that applies the time-delay estimation and the concept of internal model control (IMC). TDCIM is robust against unknown dynamics and non-linear friction like coulomb friction and static friction. It is simple and computationally efficient. This study presents the relationship between the discrete TDCIM and the discrete PID controller. The PID controller is the most popular control law in the real application. But often the PID controller can be difficult to achieve the desired level of control performance. The result in this study provides a good candidate solution to these situations.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.91-99
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• 2014

The common-rail injectors are the most critical component of the CRDI diesel engines that dominantly affect engine performances through high pressure injection with exact control. Thus, from now on the advanced combustion technologies for common-rail diesel injection engine require high performance fuel injectors. Accordingly, the previous studies on the numerical and experimental analysis of the diesel injector have focused on a optimum geometry to induce proper injection rate. In this study, computational predictions of performance of the diesel injector have been performed to evaluate internal flow characteristics for various needle lift and the spray pattern at the nozzle exit. To our knowledge, three-dimensional computational fluid dynamics (CFD) model of the internal flow passage of an entire injector duct including injection and return routes has never been studied. In this study, major design parameters concerning internal routes in the injector are optimized by using a CFD analysis and Response Surface Method (RSM). The computational prediction of the internal flow characteristics of the common-rail diesel injector was carried out by using STAR-CCM+7.06 code. In this work, computations were carried out under the assumption that the internal flow passage is a steady-state condition at the maximum needle lift. The design parameters are optimized by using the L16 orthogonal array and polynomial regression, local-approximation characteristics of RSM. Meanwhile, the optimum values are confirmed to be valid in 95% confidence and 5% significance level through analysis of variance (ANOVA). In addition, optimal design and prototype design were confirmed by calculating the injection quantities, resulting in the improvement of the injection performance by more than 54%.

• Nuclear Engineering and Technology
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• v.50 no.7
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• pp.1088-1098
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• 2018

Kori unit #1, which is the first commercial nuclear power plant in Korea, was permanently shutdown in June 2017, and it is about to be decommissioned. Currently in Korea, researches on the decommissioning technology are actively conducted, but there are few researches on workers internal exposure to radioactive aerosol that is generated in the process of decommissioning nuclear power plants. As a result, the over-exposure of decommissioning workers is feared, and the optimal working time needs to be revised in consideration of radioactive aerosol. This study investigated the annual exposure limits of various countries, which can be used as an indicator in evaluating workers' internal exposure to radioactive aerosol during pipe cutting in the process of decommissioning nuclear power plants, and the growth and dynamics of aerosol. Also, to evaluate it, the authors compared/analyzed the cases of aerosol generated when activated pipes are cut in the process of nuclear power plants and the codes for evaluating internal exposure. The evaluation codes and analyzed data conform to ALARA, and they are believed to be used as an important indicator in deriving an optimal working time that does not excess the annual exposure limit.

• Tuberculosis and Respiratory Diseases
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• v.59 no.4
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• pp.368-373
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• 2005

Background : Bronchial anthracofibrosis usually manifest as a form of obstructive airway disease, and can be accompanied by parenchymal diseases such as pneumonia, and pulmonary tuberculosis. This study investigated the ventilatory dynamics according to the severity of bronchial stenosis in patients with bronchial anthracofibrosis. Method : One hundred and thirteen patients with bronchial anthracofibrosis that was confirmed by bronchoscopy and who had undergone a pulmonary function test were enrolled in this study group. The correlation coefficients between the pulmonary functional parameters and the number of lobes with bronchial stenosis were investigated. Results : The incidence of ventilatory dysfunction was 56(49.6%) for obstructive, 8(7.1%) for restrictive, 2(1.8%) for mixed, and 47(41.6%) for a normal pattern. The $FEV_1/FVC$, $FEF_{25{\sim}75%}$, $FEF_{25%}$, $FEF_{50%}$, $FEF_{75%}$, and PEF showed a significant negative correlation (p<0.05) and the Raw had a significant positive correlation with the number of lobes with bronchial stenosis(p<0.001). Conclusion : These findings suggest that the most common abnormality of the ventilatory function in bronchial anthracofibrosis is an obstructive pattern with a small airway dysfunction according to the severity of bronchial stenosis.

• Structural Engineering and Mechanics
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• v.70 no.4
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• pp.479-497
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• 2019

In the current code design, the use of a uniform internal pressure coefficient of cooling towers as internal suction cannot reflect the 3D characteristics of flow field inside the tower body with different ventilation rate of shutters. Moreover, extreme weather such as heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind. In this study, the world's tallest cooling tower under construction, which stands 210m, is taken as the research object. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed iteratively using continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind speed and rainfall intensity on the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower body is analyzed. The combination of wind velocity and rainfall intensity that is most unfavorable to the cooling tower in terms of distribution of internal pressure coefficient is identified. On this basis, the wind/rain loads, distribution of aerodynamic force and working mechanism of internal pressures of the cooling tower under the most unfavorable working condition are compared between the four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the amount of raindrops captured by the internal surface of the tower decreases as the wind velocity increases, and increases along with the rainfall intensity and ventilation rate of the shutters. The maximum value of rain-induced pressure coefficient is 0.013. The research findings lay the basis for determining the precise values of internal surface loads of cooling tower under extreme weather conditions.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.571-575
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• 2007

With intensive competition due to the limited growth of the domestic construction market volume and the opening and construction boom of international construction market, construction firms register to grope strategy of enterprise dimension for improvement such as entry extension of domestic construction market order corporate strategy and international construction market. In this research, influence factors of corporate strategy are extracted and their interrelationships are presented in the domain of change of external environment with the internal and external market system, construction enterprise's internal capacity and corporate strategy, government and the internal and external market. The result of this research will be used for quantitative analysis through system dynamics simulation and basic data of model effectiveness verification through actuality domestic construction enterprise's case study, and can be used to basic data of new corporate strategy establishment because construction enterprise forecasts effect hereafter establishing corporate strategy in construction environment that change rapidly.

• Korean System Dynamics Review
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• v.2 no.2
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• pp.119-134
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• 2001

Since 1998, government-led Korean venture business boom now proceeds into the stage of market-oriented venture business growth. At such a moment, this research is to clarify the relations between the success factors of Korean venture businesses, based on domestic and foreign documentary surveys and inquiry surveys over domestic venture businesses. This research starts from the necessity to overcome the limits of the existing researches by uni-dimensional probing research into success factors of Korean venture businesses and to manifest the multi-dimensional relations between the success factors from the various viewpoints. And this research adopts System-Dynamics methodology to manifest and utilize relations among those factors, avoiding the existing metrical approaches. This research can be called a new approach to the current ecosystems of Korean venture in which whether venture businesses success in Korea is considered to depend on the list on the stock market. For this, this research implemented verification analysis through the simulations of each factor at various levels to build causality map which clarifies the causality of success factors of venture businesses through the System-Dynamics methodology and to utilize it as a way of supporting tool for decision-making of venture businesses. This research will be able to suggest the reactions depending on various internal and external situations. This research tried to manifest the causality map of each factor on the basis of inquiry surveys and documentary surveys to verify feedback among each factor by the SD methodology. This research will be a basis bolster up the still fragile substructure of venture businesses through an efficient analysis framework using the verification of SD methodology and resulting outcomes from this research.

• Proceedings of the Korean System Dynamics Society
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• 2001.10a
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• pp.3-14
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• 2001

Since 1998, government-led Korean venture business boom now proceeds into the stage of market-oriented venture business growth. At such a moment, this research is to clarify the relations between the success factors of Korean venture businesses, based on domestic and foreign documentary surveys and inquiry surveys over domestic venture businesses. This research starts from the necessity to overcome the limits of the existing researches by uni-dimensional probing research into success factors of Korean venture businesses and to manifest the multi-dimensional relations between the success factors from the various viewpoints. And this research adopts System-Dynamics methodology to manifest and utilize relations among those factors, avoiding the existing metrical approaches. This research can be called a new approach to the current ecosystems of Korean venture in which whether venture businesses success in Korea is considered to depend on the list on the stock market. For this, this research implemented verification analysis through the simulations of each factor at various levels to build causality map which clarifies the causality of success factors of venture businesses through the System-Dynamics methodology and to utilize it as a way of supporting tool for decision-making of venture businesses. This research will be able to suggest the reactions depending on various internal and external situations. This research tried to manifest the causality map of each factor on the basis of inquiry surveys and documentary surveys to verify feedback among each factor by the SD methodology. This research will be a basis bolster up the still fragile substructure of venture businesses through an efficient analysis framework using the verification of SD methodology and resulting outcomes from this research.

• Journal of Korean Academy of Nursing
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• v.32 no.2
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• pp.231-242
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• 2002

The purpose of this study was to identify the rate of suicidal attempts, investigate difference of rate of suicidal attempts between students and delinquents, and examine correlation between personality, family dynamics, environment, and suicidal attempts among Korean adolescents. Method: Data were collected through questionnaire surveys. Internal consistencies for this questionnaire ranged from 0.63 to 0.88. The subject used in this study consisted of 922(delinquent : 367, student : 555), using the proportional stratified random sampling method. Statistical methods employed were Chi-square and t-test. Results: \circled1 The rate of suicidal attempts were 10.8%, and the highest peak age of suicidal attempt was 17-18 year old (16.9%). \circled2 Delinquents(19.6%) showed a higher rate of suicidal attempts than students (5.1%). Among the students, girls (43.3%) showed a higher rate of suicidal attempt than boys (19.1%). Whereas, boys (80.9%) showed a higher rate of suicidal attempt than girls (56.7%) among delinquents. \circled3 Those who attempt suicide have more familial problem such as incest, psychosis, depression, attempted suicide, committed suicide, and alcoholism in their family. They also have more dysfunctional family dynamics, environment, and maladaptive personalities than non-attempters. Conclusions: Suicide and suicidal behaviors are multifaceted events. For suicide prevention, independent assessments of variables such as familial problems, personality, family dynamics, and environment must be considered.

• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.5
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• pp.343-350
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• 2017

Underwater glider with a single buoyancy engine could generally obtain propulsive forces by moving the center of buoyancy and gravity. Futhermore, The hull and internal structure of underwater glider are designed according to the purpose of long-time operation, high speed and a wide variety of payloads (sensors, communications and etc.). In this paper, Ray-type underwater glider featuring flatfish is considered in view of hydrodynamics. The hull design is especially performed by the analysis of fluid resistance and dynamic performance. The resistance performance is analyzed using the Computational Fluid Dynamics (CFD). In addition, a simulation program is implemented in order to verify the validity of dynamics modeling and dynamic performances.