• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.6
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• pp.995-1006
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• 2015

Underwater glider, as a new kind of autonomous underwater vehicles, has many merits such as long-range, extended-duration and low costs. The shape of underwater glider is an important factor in determining the hydrodynamic efficiency. In this paper, a high lift to drag ratio configuration, the Blended-Wing-Body (BWB), is used to design a small civilian under water glider. In the parametric geometric model of the BWB underwater glider, the planform is defined with Bezier curve and linear line, and the section is defined with symmetrical airfoil NACA 0012. Computational investigations are carried out to study the hydrodynamic performance of the glider using the commercial Computational Fluid Dynamics (CFD) code Fluent. The Kriging-based genetic algorithm, called Efficient Global Optimization (EGO), is applied to hydrodynamic design optimization. The result demonstrates that the BWB underwater glider has excellent hydrodynamic performance, and the lift to drag ratio of initial design is increased by 7% in the EGO process.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.621-631
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• 2017

Many developing countries considering the introduction of nuclear power find that large-scale reactor plants in the range of 1,000 MWe to 1,600 MWe are not grid appropriate for their current circumstance. By contrast, small modular reactors are generally too small to make significant contributions toward rapidly growing electricity demand and to date have not been demonstrated. This paper proposes a radically simplified re-design for the nuclear steam cycle for a medium-sized reactor plant in the range of 600 MWe. Historically, balance of plant designs for units of this size have emphasized reliability and efficiency. It will be demonstrated here that advances over the past 50 years in component design, materials, and fabrication techniques allow both of these goals to be met with a less complex design. A disciplined approach to reduce component count will result in substantial benefits in the life cycle cost of the units. Specifically, fabrication, transportation, construction, operations, and maintenance costs and expenses can all see significant reductions. In addition, the design described here can also be expected to significantly reduce both construction duration and operational requirements for maintenance and inspections.

• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.673-680
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• 2022

Modular construction is recognized as a construction method with various advantages, such as shortening the construction duration, achieving quality control through factory production, ease of maintenance, and reduced construction costs due to reduced weight of materials. However, despite efforts by the modular industry and government to activate modular construction, it has rarely been established in the domestic market. Currently, there are technical limitations to the modular construction fire resisting technology applied to general buildings. The lack of access to modular construction fire resistance regulation is considered a major factor. In this study, the current status and problems with modular construction fire resistance regulation, a significant hindrance factor, were considered to activate modular construction. This study is intended to present a direction for institutional improvement in modular construction fire resistance and a direction for research and development.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.6
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• pp.482-490
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• 2023

With the advent of the Fourth Industrial Revolution, many companies are developing Smart Ships to enable autonomous navigation, unmanned operation, and cost-effective shipping. In order to facilitate the operation of these Smart Ships, significant emphasis is being placed on improving external communication capabilities and developing autonomous navigation systems. Moreover, unmanned ship operation necessitates replacing of all visually observed conditions with sensors, leading to an inevitable increase in the number of sensors and actuators compared to traditional methods. However, in South Korea, the communication network for sensors and actuators primarily relies on the conventional 1:1 hardwired wiring, with the use of higher-level communication networks when necessary. Therefore, in this paper, we introduce the AS-Interface protocol, which is used for monitoring and controlling sensors and actuators, with the expectation that it will greatly contribute to the development of future Smart Ships by reducing production time, costs, and maintenance duration.

• Economic and Environmental Geology
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• v.44 no.6
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• pp.533-539
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• 2011

Critical infrastructure resilience has been integrated in critical infrastructure protection in US after Department of Homeland Security recognized that protection, in isolation, is a brittle strategy. Here "resilience" is the system's ability to efficiently reduce both the magnitude and the duration of systemic impacts after hazards, and quantitatively assessed as a resilience cost. The resilience cost is the sum of systemic impacts and recovery efforts, and many case studies on resilience costs show that the recovery effort should be included in resilience assessment. This paper explains how the resilience cost is defined and quantified with a case study.

• Journal of Applied Reliability
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• v.14 no.4
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• pp.225-229
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• 2014

A one-shot device is defined as a product, system, weapon, or equipment that can be used only once. After use, the device is destroyed or must undergo extensive rebuild. Determining the reliability of a one-shot device poses a unique challenge to the manufacturers and users due to the destructive nature and costs of the testing. This paper presents a reliability growth prediction for a one-shot system. It is assumed that 1) test duration is discrete(i.e. trials or rounds); 2) trials are statistically independent; 3) the number of failures for a given system configuration is distributed according to a binomial distribution; and 4) the cumulative expected number of failures through any sequence of configurations is given by AMSAA model. When the system development is represented by three configurations and the number of trials and failures during configurations are given, the AMSAA model parameters and reliability at configuration 3 are estimated by using a reliability growth analysis software. Further, if the reliability growth predictions do not meet the target reliability, the sample size of an additional test is determined for achieving the target reliability.

• Neonatal Medicine
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• v.16 no.1
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• pp.25-35
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• 2009

Purpose: The characteristics of hospitalized patients in neonatal intensive care units (NICUs), including hospitalization costs (HC) and National Health Insurance (NHI) status were studied. Methods: We gathered the following data from 7 hospitals in Korea during 2006: the distribution of patients according to birth weight (BW), and the duration of the hospital stay according to BW and He. Results: The patients who were admitted to the NICU consisted of high-risk neonates, including low birth weight or premature neonates, which comprised 50% of all neonates admitted to the NICU. The duration of hospitalization was 75-90 days for neonates with BW <1,000 g, 45-60 days for neonates with BW between 1,000 and 1,499 g, and approximately 15 days for neonates with BW between 2,000 and 2,499 g. The portion of the HC covered by the NHI was 77.1%, 22.9% of the total HC was not covered by the NHI (19.5% was included in the list, but not covered by the NHI and 3.4% was not listed, but covered by the NHI). The average total HC per person was 4,360,000 won, and the HC covered and not covered by the NHI were 3,677,000 won and 1,007,000 won, respectively. The mean HC were as follows; 35,000,000 won for a BW <500 g, 18,000,000 won for a BW between 500 and 999 g, 16,000,000 won for a BW between 1,000 and 1,499 g, and 4,200,000 won for a BW between 1,500 and 1,999 g. Conclusion: Not only premature, but also ill neonates were under the care of the NICU. The HC increased as the BW decreased and the hospitalization period increased. The proportion of the patient's financial burden is >25% of the total He. For this matter, additional NHI is needed.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.369-376
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• 2020

This study was to investigate the predictors of suicidal thoughts in the subjects who received the support for depression drug costs at a local public health center. The subjects were 156 depressed patients aged 18 and over. Data analysis was conducted by descriptive statistics, χ²-test, t-test and logistic regression analysis. The results of the analysis showed that the suicidal thoughts rate of the subjects was 25%, and the subjects showed significant differences in suicidal thoughts as the duration of antidepressant use was longer (t=-2.19, p<.05), the perceived physical health(t=3.03, p<.01) and the perceived mental health (t=5.21, p<.001) were lower, and the depression(x²=41.11, p<.001) were higher. The predictors of suicidal thoughts were perceived mental health(OR=0.97, p<.05) and depression(OR=8.44, p<.001). The regression equation of this study explained 42.4% of the suicidal thoughts of the subjects. Continued assessment and convergent mental health promotion programs are required for depression patients living in the community.

• Korean Journal of Biological Psychiatry
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• v.26 no.2
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• pp.39-46
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• 2019

Antidepressants are widely used to treat depression in Korea, however, only a few studies have focused on the provider of the treatment. The aim of the study is to compare the differences between patients who were prescribed antidepressants by psychiatrists and those who were prescribed antidepressants by non-psychiatrists in South Korea. Patients with a diagnosis of depressive disorder who had been newly prescribed antidepressants in 2012 were selected from the Health Insurance Review and Assessment Service database. They were classified into two groups depending on whether they received the antidepressant prescription from a psychiatrist or non-psychiatrist. Sociodemographic, clinical, and depression related cost has been investigated. Treatment resistant depression, which is defined as a failure of two antidepressant regimens to alleviate symptoms, was also investigated. Prescription adequacy was assessed based on whether a regimen was maintained for at least 4 weeks. Among the 834694 patients with pharmaceutically treated depression (PTD) examined in this study, 326122 (39.1%) were treated by psychiatrists. Patients who were treated by psychiatrists were younger and had more psychiatric comorbidities than those treated by non-psychiatrists. They had longer PTD duration (229.3 days vs. 103.0 days, p < 0.05) and a larger proportion of treatment resistant depression (9.3% of PTD) when compared to those patients treated by non-psychiatrists. The patients treated by psychiatrists had a smaller proportion of inadequate antidepressant use compared to those patients in the non-psychiatrist group (44.5% vs. 65.1%, p < 0.05). The costs related to depression corrected with PTD duration were higher in the non-psychiatrist group (32214 won vs. 56001 won, p < 0.05). Patients who receive antidepressants from psychiatrists are patients with more severe, treatment-resistant depression. Psychiatrists prescribe antidepressants more adequately and cost- effectively than non-psychiatrists.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.309-316
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• 2016

In this study, performance of hardening accelerator types which promote setting and hardening of cement has been reviewed in order to develop early age strength of concrete with compressive strength of 21~27 MPa after examination of strength development of the concrete at early age according to curing temperature and unit cement(binder) content. As results, soluble mineral salt showed better hardening acceleration effect than organic salt in the scope of this study. Also, hydration reaction accelerating effect of $C_3S$ by Soluble mineral salt is effective on development of early age compressive strength and it was shown that the Pt's hydration reaction accelerating effect was the best. Construction duration reduction can be expected by securing compressive strength for prevention of early aged freezing damage in 25hour-curing time under curing temperature at $15^{\circ}C$. Also, it was shown that compressive strength of specimen cured at $5^{\circ}C$ was similar with plain specimen cured at $10^{\circ}C$. Therefore, it is expected that fuel costs and carbon dioxide can be reduced when the same construction duration is considered.