In this paper, a pico hydro turbine employing low head circulation water at fish farms is designed and evaluated. Due to the advantages of simple structures, small head requirements, and low-cost investment, the constant thickness propeller turbine is considered as a feasible solution. The design process based on the free vortex method is presented in full detail, and a 4-blade runner is built using BladeGen. The turbine performance is analyzed both numerically and via experimental methods. Despite slight differences, the results show similar trends between CFD simulations and experiments carried out on factory test-rigs in a wide range of working conditions. At the design flow rate, the turbine achieves the best efficiency of 70 %, generating 3.5 kW power when rotating at 420 rpm. The internal flow field, as well as the turbine's behavior, are investigated through the distribution of blade streamlines, pressure, and velocity around the runner. Moreover, the pressure coefficient on the blade surface at 3 span positions is plotted while the head loss for each simulation domain is calculated and displayed by charts.

The Al-Zour coastal area, located in southern Kuwait, is a region of concentrated industrial water use, seawater intake, and the outfall of existing power plants. The Al-Zour LNG import facility project is ongoing and there are two issues regarding the seawater temperature in this area that must be considered: variations in water temperature under local meteorology and an increase in water temperature due to the expansion of the thermal discharge of expanded power plant. MIKE 3 model was applied to simulate the water temperature from June to July, based on re-analysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the thermal discharge input from adjacent power plants. The annual water temperatures of two candidate locations of the seawater intake for the Al-Zour LNG re-gasification facility were measured in 2017 and compared to the numerical results. It was determined that the daily seawater temperature is mainly affected by thermal plume dispersion oscillating with the phase of the tidal currents. The regional meteorological conditions such as air temperature and tidal currents, also contributed a great deal to the prediction of seawater temperature.

The recent increase in crude oil trading has led to an increase in the workings of SPM for crude oil carriers. VLCCs generally encounter difficulty entering port due to limitations in terms of sea depth and maneuverability. The SPM is a system that allows mooring to the buoy located in the outer sea for such vessels. However, the buoy is more affected by relatively external forces because of their offshore location. Therefore, the safety assessment of SPM is particularly important as it can lead to large oil pollution disasters in the event of SPM accidents. Despite this, in the implementation of the Marine Traffic Safety Audit Scheme in Korea, there exists no guidance for SPM. In this study, a SPM mooring safety assessment is performed using OPTIMOOR, a numerical analysis program, so as to understand the mooring characteristics of SPM. As a result, it is confirmed that the tension of mooring lines and hull movement in the SPM are greatly affected by the encounter angles with external forces. In addition, it is found that the maximum tension of the mooring line is elevated as the water depth becomes shallower through sensitivity analysis. According to SPM characteristics, which has a large influence on the encounter angle, this study has proposed an amendment to setting criteria in the implementation of the Maritime Traffic Safety Audit Scheme which could improve the reliability and accuracy of mooring safety assessments.

The Port of Pyeong Taek is located on the west coast, meaning that the difference between the rise and fall of tide is great (flood tide 1.8 to 2.9 knots, ebb tide 1.6 to 2.9 knots). Due to mainly N~NW’ly strong winds & high waves during winter, navigating as well as loading & discharging vessels must focus on cargo handling. The strong tidal and wind forces in the Port of Pyeong Taek can push an LNG carrier away from its berth, which will end up causing forced disconnection between the vessel’s cargo line and shore-side loading arm. The primary consequence of this disconnection will be LNG leakage, which will lead to tremendous physical damage to the hull and shore-side equipment. In this study, the 125K LNG Moss Type ship docked at No. 1 Pier of the Pyeong Taek is observed, and the tension of the mooring line during cargo handling is calculated using a combination of wind and waves to determine effective mooring line and mooring line priority management. As a result if the wind direction is 90° to the left and right of the bow, it was found that line monitoring should be performed bearing special attention to the Fore Spring Line, Fore Breast Line, and Aft Spring Line.

Even if only two ships are encountered, a collision may occur due to the mistaken judgment of the positional relationship. In other words, if an officer does not know a target ship’s intention, there is always a risk of collision. In this paper, the experiments are conducted to investigate how the intention affects the action of collision avoidance in cooperative and non-cooperative situations. In non-cooperative situation, each ship chooses a course that minimizes costs based on the current situation. That is, it always performs a selfish selection. In a cooperative situation, the information is exchanged with a target ship and a course is selected based on this information. Each ship uses the Distributed Stochastic Search Algorithm so that a next-intended course can be selected by a certain probability and determines the course. In the experimental method, four virtual ships are set up to analyze the action of collision avoidance. Then, using the actual AIS data of eight ships in the strait of Dover, I compared and analyzed the action of collision avoidance in cooperative and non-cooperative situations. As a result of the experiment, the ships showed smooth trajectories in the cooperative situation, but the ship in the non-cooperative situation made frequent big changes to avoid a collision. In the case of the experiment using four ships, there was no collision in the cooperative situation regardless of the size of the safety domain, but a collision occurred between the ships when the size of the safety domain increased in cases of non-cooperation. In the case of experiments using eight ships, it was found that there are optimal parameters for collision avoidance. Also, it was possible to grasp the variation of the sailing distance and the costs according to the combination of the parameters, and it was confirmed that the setting of the parameters can have a great influence on collision avoidance among ships.

The purpose of this study is to optimize the extraction conditions (time, pH, and temperature) for water-soluble dietary fiber (SDF) and solids from Opuntia ficus-indica (OFI) stems and to evaluate the functionality of the optimized extract. The maximum extraction yield was obtained when 100% distilled water was used, indicating that ethanol hampered the extraction. The extraction yields were lower at higher temperatures and lower pHs. The maximum extraction of SDF (27.92%) and solids (5.6 g) was achieved with a 7-h extraction at 50oC and pH 7.0, with desirability being 0.958. The stem extract obtained under the optimum extraction conditions had an antioxidant capacity of 118.10 mg vitamin C equivalents (VCE) using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. In a medium containing 30% extract, the growth of E. coli was reduced by 34%, while that of B. cereus was reduced by 23%. These results suggest that OFI stems can be used as a functional resource.

The goal of this study was to identify how well learners express themselves when an online conversation environment is provided in a SW education curriculum. In order to achieve this goal, this study took place during the first semester of 2018, with the subjects being 115 students belonging to two classes from 5th grade and two from the 2nd year of middle school in schools that were conducting the SW leadership school project. The results of creating an online conversation environment and collecting the students’ opinions about it showed that the higher the age of the students, the better they adapted to the online environment and, furthermore, female students especially proved to be more active at online expressions compared to male students.

본 연구는 중국 상장기업을 표본으로 기업의 소유 및 지배구조가 기업의 현금보유에 미치는 영향을 실증적으로 분석하고 또한 소유 및 지배구조에 따라 현금자산이 어떻게 다르게 사용되는지를 분석한다. 더 나아가 기업의 경영성과에 어떤 영향을 미치는지를 실증적으로 분석한다. 주요 분석 결과는 다음과 같다. 먼저 중국기업의 소유 및 지배구조는 기업의 현금보유 경향에 영향을 미치는 것으로 나타났다. 대주주 지분율이 높고 이사회규모가 작은 기업의 현금보유가 많은 것으로 나타난 반면, 소유권이 분산되어 효과적인 감시주체가 적고 이사회 규모가 커서의사결정의 효율성이 떨어지는 기업은 현금자산이 적었다. 이는 이들 기업은 현금자산을 주로 비합리적인 자본 지출이나 연구개발에 빨리 소진하였기 때문인 것으로 볼 수 있다. 이러한 현금사용 방식의 차이는 기업성과에도 영향을 미쳐 대주주 지분율이 낮고 이사회 규모가 큰 기업에서 현금을 많이 보유할 때 영업이익률이 낮은 것으로 나타난 반면, 대주주 지분율이 높고 이사회 규모가 작은 기업의 경영성과는 더 좋은 것으로 나타났다. 중국기업의 소유 및 지배구조는 배당정책에도 영향을 미쳤는데 대주주 지분율이 높은 기업에서는 기업내부의 현금이 증가함에 따라 배당을 많이 하는 반면에, 대주주 지분율이 낮은 기업에서는 배당이 감소하여 기업내부의 현금 을 주주에게로 이전하지 않는 것으로 나타났다. 이러한 결과는 중국기업의 소유구조상 대주주 지분율이 낮고 소유권이 분산된 기업에서는, 지배 주주가 존재하고 소유권이 집중된 기업보다 주주와 경영자 사이의 대리인 문제가 더 심각함을 보여 준다. 이에 따라 소유권이 분산된 중국기업에서 향후 주주의 권한 강화와 함께 경영진에 대한 감독이 강화될 필요가 있음을 시사한다. 또한 이사회 규모와 관련해서 이사회 규모가 작은 기업의 이사회가 더 효율적이며, 사외이사는 기업의 현금보유 경향에 영향을 미치지 않고 그 역할을 제대로 수 행하지 못하며 사외이사의 독립성이 떨어짐을 의미한다. 따라서 향후 중국기업에서 이사회 효율성을 강화하고 사외이사 제도를 적극 보완하는 등 이사회 기능을 개선해야 함을 시사한다.