• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.483-490
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• 2016

Automobile door latch is a fine design and assembly techniques are required in order to produce them in a small component assembly shape such as a spring, injection products, a small-sized motor. The door latch is fixed to not open the door of the car plays an important role it has a direct impact on the driver's safety. In this study, during trimming of the terminals of the connector main components of the car door latch, reduce rollover and conducted a research to find a suitable effective shear surface. Using the Taguchi method with orthogonal array of Finite Element Analysis and optimal Design of Experiments were set up parameters for the shear surface quality of the car door latch connector terminals. The design parameters used in the analysis is the clearance, the radius, and the blank holding force, the material of the connector terminal is a C2600. Trimming process optimum conditions suggested by the analysis has been verified by experiments, the shear surface shape and dimensions of a final product in good agreement with forming analysis results.Taguchi method from the above results in the optimization for the final rollover and effective shear surface improved for a vehicle door latch to the connector terminal can be seen that the applicable and useful for a variety of metal forming processes other than the trimming process is determined to be applicable.

• Journal of Korean Society on Water Environment
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• v.33 no.2
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• pp.170-180
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• 2017

The study used jet water flow, ultra-sonication and ozonation system units to investigate impact of the unit components on water quality of stagnant Yeo-cheon River reach, Korea. Samples were collected at six locations, before operation and after 1, 3 and 6 hrs of operation. By operating the water flow unit only, dissolved oxygen increased as high as 90% after 3 hr at 25 m downstream of the device and Chl-a was reduced by 80%. Incorporating sonication, greater than 80% of Chl-a was removed even at 100 m distance from the device. Besides, total dissolved phosphorus was reduced from an average value of $420({\pm}70){\mu}g/L$ before ultrasonic irradiation to $160({\pm}40){\mu}g/L$ after the treatment. Releasing ozone into the flow with sonication, Chl-a was considerably removed from the water column and ammonia nitrogen was also decreased to average value of $20{\mu}g/L$ from $60{\mu}g/L$. However, as only $3{\ast}10^{-3}mg/L$ of ozone was used for safety purpose and due to brief reaction time it takes, effect of integrating ozone to the system covered limited area. Generally, combining sonication to jet flow is promising in preventing algal bloom formation since it has effectively removed Chl-a from the water column.

• Korean Journal of Environment and Ecology
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• v.34 no.4
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• pp.282-293
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• 2020

This study investigated a long-term variation trend of water quality, fish compositions, and ecological health conditions in the Gwanpyeong stream located in the nearby Daejeon metropolitan city to understand the impact of urban development projects on the aquatic ecosystem. The sampling was made in four surveys (2009, 2010, 2016, 2019) before and after urbanization. The urban development was conducted in 2008, resulting in the stream's ecological disturbance, and the stream restoration was conducted in 2012. Thus, stream monitoring was conducted to analyze the ecological trends before and after the restoration. The multi-metric models for Fish Assessment Index(FAI) and necropsy-based Health Assessment Index(HAI) were applied in the fish community and organ-level, respectively, to assess the ecological health of the stream. Minimum turbidity and chlorophyll-a(Chl-a) occurred in the mid-stream(St. 2), and this was probably due to rapid current velocity in the riffle zone. We collected 18 fish species, and the dominant species was Zacco platypus (40.6%). In 2016 immediately after the stream restoration, the relative proportions of sensitive species and insectivore species were the highest along with highest values in the species diversity and species richness index, resulting in the best condition in the ecological health, based on FAI model values. However, the ecological health, based on the FAI, became worse in the latest survey conducted in 2019. The analysis of the HAI model based on the organ-level approach showed skin erosion in the fish of upper stream, kidney defects in downstream, and the liver and gill defects observed in all sites, indicating that the anatomical health was also affected.

• Journal of the Korean GEO-environmental Society
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• v.21 no.10
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• pp.11-16
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• 2020

Korea's agricultural reservoir is one of the country's major infrastructures and plays an important role in people's lives. However, aging reservoirs are a risk for life and property. Currently, large and small dams and reservoirs have been constructed nationwide for more than 40 years of aging. Dams and reservoirs built nationwide are managed by various institutions. Therefore, it is difficult to manage all dams and reservoirs due to cost and time. Managers in the field with less management personnel and lack of expertise should be able to quickly identify risk factors for multiple reservoirs. In this study, risk factors such as seepage, leakage, settlement slide, crack and erosion were selected. To assess the risk of the items, we used the analytical hierarchical process (AHP), one of the Multi-Criteria Decision Making (MCDM) methods. The analysis showed that seepage has the greatest impact on reservoir collapse. It is judged that the priority of detailed diagnosis can be determined by evaluating the risk of dam reservoir collapse in a convenient way in advance using the calculated weight.

• Korean Journal of Construction Engineering and Management
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• v.16 no.1
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• pp.64-73
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• 2015

The theft of construction equipments and materials at construction sites is one of the risk factors that may affect to the productivity as well as the progress of the project. However, managers of the construction site have paid little attention to the security measure, therefore the theft loss at construction sites has been occurred repeatedly every year. In this study the situation analysis has been carried out for the present condition of theft loss of construction equipments and materials as well as its prevention measure based on the questionnaire survey targeting field managers, experienced theft loss at the site, as a part of base study to set up a security measure of construction sites. The main content of this study is analyzing characteristics of theft loss and the degree of impact and risk by it at construction sites, then reviewing the direction of the prevention plan establishment for the future through the analysis of the importance and utilization level of prevention measures. The result of this study would give an opportunity to create an awareness against the theft loss at construction sites as well as can be utilized as a basic survey for the systematic development of concerned prevention measures.

• Journal of Korean Society of Forest Science
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• v.107 no.1
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• pp.59-70
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• 2018

The objective of this study was to develop erosion control dam for preventing disaster in consideration of characteristics of forested catchment near urban area, and to assess its stability and functionality to see its practicability in the field. Two types of hybrid erosion control dams were developed including debris flow prevention dam by using pillar and float board screen type and debris flow control dam by using groyne. Also, review about their static (sliding, overturning, bearing capacity) and dynamic (member force) stability was carried out. According to the result, most of the assessed items met standard safety level although there were some cases where assessed items were short of stability criteria against impact. Also, after miniature flume experiments based on the developed erosion control dam to prove structure function (material catch, deposit), it turned out the dam decreased flow sediment amount and velocity while increasing sediment-capturing capacity by 3.5 times on average compared to the one controlled without erosion control dam. When function of erosion control dam for forested catchment near urban area is quantified based on future flume experiments in a variety of conditions, the dams can be practically used in the urban area, contribution to effectively reducing debris flow damage.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.191-198
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• 2008

Flow accelerated corrosion (FAC) phenomenon of low alloy carbon steels in nuclear power plant has been known as one of major degradation mechanisms. It has a potential to cause nuclear pipe rupture accident which may directly impact on the plant reliability and safety. Recently, the equipotential switching direct current potential drop (ES-DCPD) method has been developed, by the present authors, as a method to monitor wall loss in a piping. This method can rapidly monitor the thinning of piping, utilizing either the wide range monitoring (WiRM) or the narrow range monitoring (NaRM) technique. WiRM is a method to monitor wide range of straight piping, whereas NaRM focuses significantly on a narrow range such as an elbow. WiRM and NaRM can improve the reliability of the current FAC screening method that is based on computer modeling on fluid flow conditions. In this paper, the measurements by ES-DCPD are performed with signal sensitivity analyses in the laboratory environment for extended period and showed the viability of ES-DCPD for real plant applications.

• Journal of Environmental Policy
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• v.13 no.4
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• pp.79-105
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• 2014

Natech risk is a type of complex disasters that natural hazards trigger technological disaster or industrial accidents. Research on Natech risk has been started from the mid-1990s in European countries and the Unites States, and drawn much more attention after the Fukushima nuclear accident caused by the 2011 East Japan earthquake. While early studies on Natech risk have focused on the causal natural hazards and possibility to occur, and the resulting spill of hazardous materials from the perspective of science and engineering, the recent research interests lie on effective Natech risk management. Especially, emphasizing the difference of Natech risk management from traditional disaster management, issues of uncertainty management, integration between natural disaster and technological disaster, and responsibility, has been drawn attention. In Korea, Natech risk has not been introduced as a research topic. Although some regulatory improvements have been made in nuclear safety and chemical Substance management after the Fukushima disaster, the potential impact of natural hazards in these areas has not been considered yet. It is necessary to raise the issues of Natech risk management in research and policy areas through active discussion and interdisciplinary approaches.

• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.1-6
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• 2015

In this study, with the awareness of the limitations set in the currently operated calculations of holding power and the holding power coefficient of anchors of naval ships due to its simple application of a specific value, various factors that impact the holding power and its coefficient were verified based on existing data analysis of literature research and numerous experiment results from anchor manufacturers, research institutes and academic community in order to overcome the aforementioned limitations. In addition, holding power and holding power coefficient were compared and analyzed by the shape of anchors. As a result, we came to know that the holding power of AC-14 type anchor is stronger than that of ASS type anchor or U.S. Navy Standard type anchor which makes it possible to reduce the weight of the anchor and therefore ease the process of naval shipbuilding. Furthermore, we confirmed the fact that U.S. Navy Standard type anchor does not react sensitively to the weight change of the anchor. Lastly, we found out that Danforth type anchor's holding power coefficient is in inverse proportion to the weight. Moreover, instructions for managing anchor are arranged easily for your information. The results of this study is expected to provide anchor - operating naval crew with a reliable theoretical basis pertaining to an anchor's holding power and its coefficient and contribute much for the safety of their act of anchoring.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.6
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• pp.484-492
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• 2016

The turbine is an important component and has a significant impact on the thermodynamic efficiency of the organic Rankine cycle. A precise preliminary design is essential to developing efficient turbines. In addition, performance analysis and structural analysis are needed to evaluate the performance and structural safety. However, there are only a few exclusive studies on the development process of the radial inflow turbines for the organic Rankine cycle (ORC). In this study, a preliminary design of the ORC radial inflow turbine was performed. Subsequently, the performance and structural analysis were also carried out. The RTDM, which was developed as an in-house code, was used in the preliminary design process. The results of the performance analysis were found to be in good agreement with target performances. Structural analysis of the designed turbine was also carried out in order to determine whether the material selection for this study is suitable for the flow conditions of the designed turbine, and it was found that the selected aluminum alloy is suitable for the designed turbine. However, the reliability of the preliminary design algorithms and numerical methods should be strictly verified by an actual experimental test.