• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.1
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• pp.45-51
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• 2004

Boiler tubes in power plants are often leaked due to various material degradations including creep and thermal fatigue damage under severe operating conditions such as high temperature and high pressure over an extended period of time. To monitor and diagnose the tubes on site and in real time, the acoustic emission (AE) technology was applied. We developed an AE leak detection system, and used it to study the variation of AE signal from the on-site tubes in response to the changes in the boiler operation condition and to detect the locations of leakage based on it. Detection of leak was performed by acquiring and evaluating the signals in separate regimes of high and low frequency signal. As a result of these studies, we found that on-line monitoring and detection of leak location for boiler tubes is possible using the developed system. Thus, the system is expected to contribute to the safe operation of power plants, and prevent economic losses due to potential leak.

• FLOWER RESEARCH JOURNAL
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• v.17 no.3
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• pp.197-200
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• 2009

A new grafted cactus cultivar, G. 'Gohong', was developed by crossing 'DR' line with dark red color and G. 'Seolhong' with dark red color in 2004. It grew for 6 months after grafting in vitro and culturing at 100 mL test tube. After grafting and planting in greenhouse in 2005, various characteristics were evaluated three times until 2008. It has flat-round shape and dark red skin. In addition, it has 8 to 10 ribs and gray and straight spines on the body. The diameter of it was 44.1 mm after 10 months. It grew bigger and faster comparing with G 'Seolhong' cultivar. The ability of propagation in G. 'Gohong' is similar to that of G. 'Seolhong' producing approximately 12.1 daughter globes for 10 months after planting.

• FLOWER RESEARCH JOURNAL
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• v.19 no.4
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• pp.248-250
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• 2011

A new grafted cactus cultivar, G. mihanovichii 'Ihong', for exporting abroad, was developed by crossing G. mihanovichii 'DR' line with dark red color, and G. mihanovichii 'Seolhong' cultivar with dark red in 2005. It grew for 6 months after grafting in vitro and culturing at 100 mL test tube. After grafting and planting in greenhouse in 2006, various characteristics were evaluated three times until 2009. It has flat round shape and dark red skin. In addition, it has 8 to 10 ribs and brown straight spines on the body. Its diameter was 44.0 mm after 10 months from planting, and bigger comparing with that of 'Seolhong' cultivar. The ability of propagation in 'Ihong' was better than that of 'Seolhong' and 'Ihong' approximately produced 15.8 offsets for 10 months.

• FLOWER RESEARCH JOURNAL
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• v.16 no.3
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• pp.196-199
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• 2008

A new grafted cactus variety, 'Dahong', Gymnocalycium mihanovichii, is hybrid crossed between '9508021' line with red and black color, and 'Jinhong', with dark red color in 2002. It was cultivated for 6 months after grafted in vitro and planted at 100 mL test tube. After grafting in vivo in 2003, the various characteristics of this was evaluated three times until 2006. It has the flat-round shape and dark red skin, and produces the daughter globes at areoles, which are arranged well at the low part of globe. In addition, it has 8~10 ribs and the gray and slant spines in body. The ability of propagation is better than 'Jinhong' to produce approximately 13.6 daughter globes.

• FLOWER RESEARCH JOURNAL
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• v.18 no.4
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• pp.291-294
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• 2010

A new grafted cactus cultivar, G. mihanovichii 'Hwangun', for exporting abroad, was developed by crossing G. mihanovichii 'Hwangwol' variety with yellow and orange color, and G. mihanovichii '0111021' line with yellow color in 2008. It grew for 6 months after grafting in vitro and culturing at 100 mL test tube. After grafting and planting in greenhouse in 2005, various characteristics were evaluated three times until 2008. It has flat-round shape and bright yellow skin. In addition, it has 7 to 9 ribs and brown straight spines on the body. The diameter of it was 40.9 mm after 10 months after planting, and small comparing with G. mihanovichii 'Hukwang' cultivar. The ability of propagation in G. mihanovichii 'Hwangun' is prior to that of G. mihanovichii 'Hukwang' producing approximately 22.3 daughter globes for 10 months.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.5
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• pp.372-378
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• 2007

GHX (Geothermal Heat Exchanger) design which determines the performance and initial cost is the most important factor in ground source heat pump system. Performance of GHX is strongly dependent on the thermal resistance of soil, grout and pipe. In general, GHX design is based on the static simulation program. In this study, dynamic simulation has been peformed to analyze the variation of system performance for various GHX parameters. Line-source theory has been applied to calculate the variation of ground temperature. The averaged weather data measured during a 10-year period $(1991\sim2000)$ in Seoul is used to calculate cooling and heating loads of a building with a floor area of $100m^2$. The simulation results indicate that thermal properties of borehole play significant effect on the overall performance. Change of grout thermal conductivity from 0.4 to $3.0W/(m^{\circ}C)$ increases COP of heating by 9.4% and cooling by 17%. Change of soil thermal conductivity from 1.5 to $4.0W/(m^{\circ}C)$ increases COP of heating by 13.3% and cooling by 4.4%. Change of GHX(length from 100 to 200 m increases COP of heating by 10.6% and cooling by 10.2%. To study long term performance, dynamic simulation has been conducted for a 20-year period and the result showed that soil temperature decreases by $1^{\circ}C$, heating COP decreases by 2.7% and cooling COP decreases by 1.4%.

• Journal of the Korean Society of Systems Engineering
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• v.18 no.2
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• pp.94-107
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• 2022

Accidents prevention and mitigation is the highest priority of nuclear power plant (NPP) operation, particularly in the aftermath of the Fukushima Daiichi accident, which has reignited public anxieties and skepticism regarding nuclear energy usage. To deal with accident scenarios more effectively, operators must have ample and precise information about key safety parameters as well as their future trajectories. This work investigates the potential of machine learning in forecasting NPP response in real-time to provide an additional validation method and help reduce human error, especially in accident situations where operators are under a lot of stress. First, a base-case SGTR simulation is carried out by the best-estimate code RELAP5/MOD3.4 to confirm the validity of the model against results reported in the APR1400 Design Control Document (DCD). Then, uncertainty quantification is performed by coupling RELAP5/MOD3.4 and the statistical tool DAKOTA to generate a large enough dataset for the construction and training of neural-based machine learning (ML) models, namely LSTM, GRU, and hybrid CNN-LSTM. Finally, the accuracy and reliability of these models in forecasting system response are tested by their performance on fresh data. To facilitate and oversee the process of developing the ML models, a Systems Engineering (SE) methodology is used to ensure that the work is consistently in line with the originating mission statement and that the findings obtained at each subsequent phase are valid.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.18-27
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• 2021

This study aims to develop an improved evaluation technology for assessing CANDU-6 safety. For this purpose, the multiple steam generator tube rupture (mSGTR) followed by an unmitigated station blackout (SBO) in a CANDU-6 plant was selected as a hypothetical event scenario and the analysis model to evaluate the plant responses was envisioned into the MARS-KS input model. The model includes logic models for controlling the pressure and inventory of the primary heat transport system (PHTS) decreasing due to the u-tubes' rupture, as well as the main features of PHTS with a simplified model for the horizontal fuel channels, the secondary heat transport system including the shell side of steam generators, feedwater and main steam line, and moderator system. A steady state condition was successfully achieved to confirm the stable convergence of the key parameters. Until the turbine trip, the fuel channels were adequately cooled by forced circulation of coolant and supply of main feedwater. However, due to the continuous reduction of PHTS pressure and inventory, the reactor and turbine were shut down and the thermal-hydraulic behaviors between intact and broken loops got asymmetric. Furthermore, as the conditions of low-flow coolant and high void fraction in the broken loop persisted, leading to degradation of decay heat removal, it was evaluated that the peak cladding temperature (PCT) exceeded the limit criteria for ensuring nuclear fuel integrity. This study is expected to provide the technical bases to the accident management strategy for transient conditions with multiple events.

• Journal of Korean Dental Hygiene Science
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• v.5 no.1
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• pp.13-19
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• 2022

Background: In this study, zirconia copings were fabricated by setting clinically acceptable inner values for prostheses using computer-aided design/computer-aided manufacturing (CAD/CAM). The processed copings were evaluated for the marginal and internal fit of each abutment shape with a CAD program using the silicone replica technique. Methods A total of 20 copings was produced by selecting models commonly used in clinical practice. After injecting the sample, the minimum thickness, internal adhesion interval, and distance to the margin line were set to 0.5, 0.05, and 1.00 mm using a dental CAD program, respectively. It was measured using a 2D section function in a three-way program of the silicon replication technology. Although the positions and number of measurements of the anterior and posterior regions differed, nine parts of each pre-tube were designated and measured by referring to a previous study to compare the two samples. Results As a result, the average margin of the mesial, distal, and buccal (labial) surfaces was 59.90 ㎛ in the anterior region and 60.40 ㎛ in the posterior region. The mean axial wall margin was 67.25 ㎛ in the anterior region and 69.25 ㎛ in the posterior region. In occlusion, the anterior teeth (77.70 ㎛), posterior teeth (77.60 ㎛), and both anterior and posterior regions were within the clinically acceptable range. Conclusion The edge and inner fit of zirconia coping manufactured using the CAD/CAM system showed clinically applicable results. To reduce errors and increase accuracy, materials and machine errors that affect the manufacture of prosthetics should be investigated. Based on our results, the completeness of prosthetics could increase if the inner value and characteristics of the material are adjusted when applied in clinical practice.

• Asia pacific journal of information systems
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• v.30 no.3
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• pp.568-589
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• 2020

Recently, Social media has become a concern for businesses, including Small and Medium Enterprises (SMEs). SMEs began to adopt social media to support their performance. To benefit from the application of social media, SMEs must implement the right strategy. This study aims to analyze the factors that influence the use of social media in SMEs. Furthermore, alignment between social media functionalities and strategies and their effect on SME's performance are investigated. A case study is conducted in Gymi, a garment SMEs in East Java, Indonesia. The data collection includes interviews with the owner of SMEs, observations, and document analysis. Data analysis is performed by pattern matching, which matches the patterns from the literature with data from the case study. The results of this study show that cost-effectiveness, interactivity, and compatibility are factors that influence the use of social media in Gymi. The social media used by Gymi are Instagram, Facebook, YouTube, WhatsApp, and LINE. However, the main social media used to support Gymi's functions is Instagram. Gymi has a relatively good social media strategy as it has defined a specific goal, target audience, and channel selection for social media (Instagram). It also has specific resources and policies to handle social media. Gymi monitors and evaluates their social media content activities. These strategies are aligned with the Instagram feature used to support Gymi's function, particularly marketing, sales, customer service, and to some extent, internal operation. The alignment contributes to Gymi's performance measured by the increase in reputation (number of Instagram followers) and sales.