• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.900-905
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• 2016

The field of power system harmonics has been receiving a great deal of attention recently. This is primarily due to the fact that non-linear (or harmonic-producing) loads comprise an ever-increasing portion of what is handled at a typical industrial plant. The incidence rate of harmonic-related problems is low, but awareness of harmonic issues can still help increase offshore power plant system reliability. On the rare occasion that harmonics become a problem, this is either due to the magnitude of harmonics produced or power system resonance. This harmonic study used an electrical configuration for the offloading scenario of a Floating LNG (FLNG) unit, considering power load. This electrical network configuration is visible in the electrical network load flow study part of the project. This study has been carried out to evaluate the performance of an electric power system, focusing on the harmonic efficiency of an electrically driven motor system to ensure offshore plant safety. In addition, the design part of this study analyzed the electric power system of an FLNG unit to improve the safety of operation and maintenance.

• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.523-532
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• 2015

Hydrocyclone is widely used in industry, for its simple design, high capacity, low maintenance and low operational cost. The objective of this study is to develop hydrocyclone coagulation and filtration system. The system is made of hydrocyclone ballasted coagulation with polyaluminium chloride silicate (PACS) and upflow filter to treat micro particles in urban storm runoff. Roadside sediment particles (< $200{\mu}m$) was mixed with tap water to make various turbid suspensions to simulate urban storm runoff. The filter cartridge was filled with polyethylene media system and ran 1hr per everyday and total operation time were 8.19hrs and backwashing everyday after end of operation. The operation condition of flowrate was $8.2{\sim}11.9m^3/day$ (mean $10.1m^3/day$) and surface overflow rate (SOR) based on filter surface area was $45.5{\sim}65.9m^3/m^2/day$ (mean $55.7m^3/m^2/day$). The range of PACS dosage concentration was 14.0~31.5 mg/L. As the results of operation, the range of removal efficiency of turbidity, SS were 81.0~95.8% (mean 89.5%) 81.8~99.0% (mean 91.4%), respectively. An increase of filtration basin retention time brought on increased of removal efficiency of turbidity and SS, and increase of SOR brought on decreased of removal efficiency. During the first flush in urban area, storm runoff have an high concentration of SS (200~600 mg/L) and the filtration bed becomes clogged and decreased of removal efficiency. Backwashing begins when the drainage pipe valve at the filtration tank bottom is completely open (backwashing stage 1). Backwashing stage 2 was using air bubbles and water jet washing the media for 5 mins and open the drainage valve. After backwashing stage 1, 2, 61.83~64.04%, 18.53~27.51% of SS loading was discharged from filtration tank, respectively. Discharged SS loading from effluent was 7.12~14.79% and the range of residual SS loading in fliter was 2.26~5.00%. The backwashing effects for turbidity, SS were 89.5%, 91.4%, respectively. The hydrocyclone coagulation and filtration with backwashing system, which came out to solve the problems of the costly exchange filter media, and low efficiency of removing micro particles of filter type nonpoint treatment devices, is considered as an alternative system.

• The Korean Journal of Applied Statistics
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• v.30 no.4
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• pp.539-553
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• 2017

We propose a multi-state model to analyze semi-competing risks data with interval-censored or missing intermediate events. This model is an extension of the three states of the illness-death model: healthy, disease, and dead. The 'diseased' state can be considered as the intermediate event. Two more states are added into the illness-death model to incorporate the missing events, which are caused by a loss of follow-up before the end of a study. One of them is a state of the lost-to-follow-up (LTF), and the other is an unobservable state that represents an intermediate event experienced after the occurrence of LTF. Given covariates, we employ the Lin and Ying additive hazards model with log-normal frailty and construct a conditional likelihood to estimate transition intensities between states in the multi-state model. A marginalization of the full likelihood is completed using adaptive importance sampling, and the optimal solution of the regression parameters is achieved through an iterative quasi-Newton algorithm. Simulation studies are performed to investigate the finite-sample performance of the proposed estimation method in terms of empirical coverage probability of true regression parameters. Our proposed method is also illustrated with a dataset adapted from Helmer et al. (2001).

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.4
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• pp.329-334
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• 2017

The structures, which are made up with the huge number of degrees-of-freedom and the assembly of substructures, have a great complexity. In order to increase the computational efficiency, the analysis models have to be simplified. Many substructuring techniques have been developed to simplify large-scale engineering problems. The techniques are very powerful for solving nonlinear problems which require many iterative calculations. In this paper, a modal derivatives-based model order reduction method, which is able to capture the stretching-bending coupling behavior in geometrically nonlinear systems, is adopted and investigated for its performance evaluation. The quadratic terms in nonlinear beam theory, such as Green-Lagrange strains, can be explained by the modal derivatives. They can be obtained by taking the modal directional derivatives of eigenmodes and form the second order terms of modal reduction basis. The method proposed is then applied to a co-rotational finite element formulation that is well-suited for geometrically nonlinear problems. Numerical results reveal that the end-shortening effect is very important, in which a conventional modal reduction method does not work unless the full model is used. It is demonstrated that the modal derivative approach yields the best compromised result and is very promising for substructuring large-scale geometrically nonlinear problems.

• Proceedings of KOSOMES biannual meeting
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• 2007.05a
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• pp.91-96
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• 2007

Lab scale experimental study was carried out for SBR process, to investigate the effects of influent ship sewage organic compound removal and Bacillus sp. state on design parameters. This process was able to remove nitrogen and phosphorus as well as organic matter efficiently. More than 95% of chemical oxygen demand(COD) were removed. In addition, about 97% of total nitrogen (T-N) was reduced. The total phosphorus(T-P) reduction averaged 93%. The performance load of SBR process was shown to be $0.095kg{\cdot}TOC/m^3{\cdot}day$. The pH was decreased from 8.1 to 7.0 within 30 min and increased to 7.3 at the end of anoxic stage, and these phenomena were explained. The sludge produced in the SBR process is characterized by low generation rate (about $0.36kg{\cdot}MLSS/kg{\cdot}TOC$) and excellent settleability. The number of Bacillus sp. in the SBR was 24.2%, indicating that Bacillus sp. was a predominant species in the reactor.

• 대한공업교육학회지
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• v.44 no.2
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• pp.86-103
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• 2019

The purpose of this study is to provide basic data on the development of education and training programs for training 'mechanical facilities maintenance manager'. To this end, the DACUM technique was used for job analysis and education and training programs were developed through expert consultation meetings. The job analysis was based on the 10-member DACUM Committee to derive the job definition, job model, job description, and task description of the 'mechanical facilities maintenance manager'. The main findings are as follows. First, the 'mechanical facilities maintenance manager' was defined as those who operate, inspect, diagnose, and repair mechanical facilities to provide the best performance and efficient operation management, provide a safe and pleasant environment, and perform energy saving and facility life extension tasks. Second, the duties of the 'mechanical facilities maintenance manager' analyzed in the job model consist of the comprehensive plan for operation of mechanical facilities, energy management of mechanical facilities, operation management of mechanical facilities, maintenance of mechanical facilities, safety environment management of mechanical facilities, and customer support management of mechanical facilities. Considering the nature and content of the duties, 4 to 11 tasks per duty were derived and a total of 33 tasks were presented as job model. Third, the curriculum for the 'mechanical facilities maintenance manager' was set up in two courses: Practice I for Mechanical Facilities Maintenance and Practice II for Mechanical Facilities Maintenance. Considerations and policy suggestions were presented when applying and implementing education and training programs based on the results of the research.

• Journal of Navigation and Port Research
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• v.29 no.5 s.101
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• pp.475-480
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• 2005

Lab scale experimental study was carried out for SBR process, to investigate the effects of influent ship sewage organic compound removal and Bacillus sp. state on design parameters. This process was able to remove nitrogen and phosphorus as well as organic matter efficiently. More than $92.0\%$ of chemical oxygen demand(COD) were removed. In addition, about $84.0\%$ of total nitrogen (T-N) was reduced. The total phosphorus(T-P) reduction averaged $93\%$. The performance load of SBR process was shown to be $0.095kg{\cdot}TOC/m3{\cdot}day$. The pH was decreased from 8.1 to 7.0 within 30 min and increased to 7.3 at the end of anoxic stage, and these phenomena were explained. The sludge produced in the SBR process is characterized by low generation rate (about $0.36kg{\cdot}MLSS/kg{\cdot}TOC$) and excellent settleability. The number of Bacillus sp. in the SBR was $24.2\%$, indicating that Bacillus sp. was a predominant species in the reactor.

• Resources Recycling
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• v.9 no.4
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• pp.28-36
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• 2000

This study describes to analyze the characteristics for separation and recovery of both the dried particles and the purified solvent from the waste solvent through the vaporization process by the continuous and instantaneous vacuum drying system. The vacuum drying system for the waste solvents recovery consists of a feeding pump, a double pipe heat exchanger, a vacuum spray chamber, and a condenser. The vacuum drying system heats the waste solvent to the vapor in the double pipe heat exchanger and the expanded vapor is sprayed at the end of the tube. The vaporized solvent in the condenser are recovered. The particles in the waste solvent are separated and dried from the vapor in the vacuum spray chamber. Performance evaluation of the vacuum drying system was conducted using the mixture of the dried pigment particles and benzene or alkylbenzene as test samples. For the mixture of 10 wt% pigment particles an 90% benzene, the recovery efficiency of benzene was 88% with the purity of 99% and the recovery efficiency of dried particles was 94% with the moisture of 1.1 wt%. The size of pigment particles was decreased from $6.5\mu\textrm{m}$ to $5.6\mu\textrm{m}$ in diameter due to high speed spraying and dispersion in the vacuum drying system during drying process. Therefore, the vacuum drying system showed to be an effective method for separating particles and solvent in the waste solvent.

• Journal of Technology Innovation
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• v.29 no.3
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• pp.33-62
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• 2021

This study compares and analyzes the efficiency of R&D activities of technology-innovative small and medium-sized enterprises(SMEs) between industries and proposes ways to improve efficiency. The research samples are 6,708 technology-innovative SMEs, which have received a guarantee by the KIBO from 2008 to 2011. Input variables are the level of R&D personnel, R&D investment, and output variables are patent applications, prototype. Efficiency is measured by the DEA model, and indirect comparisons that are individually measured by industry are performed. As a result of the analysis, the CCR for determining the optimal returns to scale is 0.19, the BCC for determining the optimal input distribution is 0.70, and the SE for determining the optimal output is 0.30. By industry type, the medium and low-tech industries have high CCR and BCC, while the high-end and high-tech industries have high SE. R&D activities need to be operated on an optimal scale through managing R&D performance because there is the inefficiency of scale across the industry. The contribution of the study is to analyze the R&D efficiency of each industry of technology-innovative SMEs by the technology evaluation data of the KIBO.

• Journal of Korean Home Economics Education Association
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• v.32 no.4
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• pp.1-18
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• 2020

The purpose of this study is to improve media literacy through home economics education. To this end, in this study, developed were 10 teaching-learning plans, learning activity sheets, and teaching materials for the 'relationship' area, the core concept of the 2015 revised home economics curriculum, using the ADDIE method. Pre- and post-survey results after implementing the developed program showed statistically significant improvements in enhancing participants' ability to access media and critical understanding of media. Through this, also found was that the ability to express and produce one's own thoughts and feelings has improved. As a result of a qualitative analysis, it was found that students who participated in the class experienced an overall change in the performance goals of media literacy, especially in 'critical understanding and evaluation', and improved in media use ethics and social participation consciousness as well. It is significant that this study has developed a program that can foster media literacy in home economics education. It is expected to help improve the acceptability of media literacy education in home economics education, enhancement of the expertise of home economics teachers' media literacy education, and the improvement of teaching and learning activities in the field.