In this study, a motion control problem for the vessels towed by tugboats or towing ships on the sea is considered. The towed vessel looks like the barge ship, which is used for many purposes. In these vessels, basically, the power propulsion system is not installed but just towed by a towing vessel such as tugboats with ropes and wires. It means that the motions of towed vessel are basically dependent on the tracking route of towing boat. Therefore, in some cases, undesirable and unpredictable motions may be made by environmental factors such as wave, wind attack and so on. As a result, a collision accident with others may occur during maneuvering situation. Based on these facts, the authors try to encourage the steering performance of the towed vessel by using controllable rudders without any propulsion system. In this study, especially, a controllable vessel with three rudders is considered, and a mathematical model is induced for the future study. The model is described as surge, sway motion and inertia moment by following the general representation method for the surface ship.

In this study, the conventional cylinder-shaped lower bar on the canvas was modified and its performance was tested to improve the opening force of the stow net on anchor. The improved new lower bar used in the test is consisted of 13 flat bars with a length of 1.8 m, a width of 0.075 m and a thickness of 4 mm, and a pipe with a length of 2.0 m and a diameter of 50 mm. A stow net with the improved lower bar and a stow net with an existing lower bar were installed underwater and their trajectories for 21 hours were examined. To confirm their trajectories, GPS loggers were attached to the buoys on the left and right canvases and the buoy of the hauling rope. As a result of the test, the rotation of the gear with the improved bar was smoother than that with the existing bar. As a result of comparing the changes in the interval of the buoys attached to the canvas after the low and high tide, the buoy spacing of the gear with the improved bar is wider than that of the conventional gear; moreover, the larger the interval, the smoother the rotation of the fishing gear was. Therefore, it is considered that using the improved lower bar can enhance the performance of the stow net.

To ensure the safety and functionality of a railroad bridge, maintaining the integrity of the bridge via continuous structural health monitoring is important. However, most structural integrity monitoring methods proposed to date are based on modal responses which require the extracting process and have limited availability. In this paper, the applicability of the existing damage identification method based on free-vibration reponses to time-domain deflection shapes due to moving train load is investigated. Since the proposed method directly utilizes the time-domain responses of the structure due to the moving vehicles, the extracting process for modal responses can be avoided, and the applicability of structural health evaluation can be enhanced. The feasibility of the presented method is verified via a numerical example of a simple plate girder bridge.

In this study, we developed a thermoelectric generation system for coastal fishing boats that allows for a high-density arrangement of thermoelectric modules, verified the improvement in performance by conducting comparative analysis between field test results and results from previous studies. The developed thermoelectric generation system was installed in a 3-ton gill-netter to analyze the engine revolutions per minute and energy production per day for each fishing process over a period of 20 days. From the experimental results, the maximum electric energy generated was 207.1 Wh, the minimum was 53.93 Wh and the average electric energy was 129.98 Wh. In accordance with the increasing of the engine r.p.m., the maximum electric production was 183 W at 1,500 r.p.m. It was approximately 80.5% of designed capacity, 227.2 W. Considering the result in the earlier research was 50.7% of designed capacity, 115.8 W. It was improved by 30% compared to the earlier one. The fishing operation was classified as departure, fishing and arrival. From the result on production analysis of electric energy, the composition of energy was 63% in fishing, 19.5% in departure and 17.5% in arrival. The electric energy production per unit hour was 42.8% in arrival, 32.9% in departure and 24.3% in fishing.

본 연구에서는 장미 재배온실을 대상으로 온실 내부의 태양잉여열과 외부의 공기열을 선택적 열원으로 이용하여 온실난방용 온수를 생산할 수 있는 공기 대물 히트 펌프의 설계와 성능시험을 수행하였다. 태양잉여열 이용 축열운전과 외기열 이용 축열운전은 작물의 생육적온을 고려한 온실내부의 설정온도에 따라 자동전환 되도록 설계하였다. 제어반에 12개의 기준온도를 설정함으로써 축열운전 전환, 난방, 환기를 자동제어하며, 태양잉여열-외 기열 선택적 축열운전에서 축열조의 온도는 축열능력과 난방부하에 대응하여 35~52oC로 3단계 변온제어 하였다. 태양잉여열-외기열 선택적 축열에서 태양잉여열 이용 축 열은 전체 시간의 23.1%, 외기열 이용 축열은 30.7%, 히트펌프 휴지시간은 46.2%를 차지하였으며, 난방성능계수는 태양잉여열 이용 축열 시 3.83, 외기열 이용 축열 시 2.77, 전체 3.24로 평가되었다. 비교시험을 위해 축열 조 온도를 50~52oC로 항온제어 하는 조건에서 외기열 단독 이용 축열 시험을 수행하였으며 이때의 난방성능계 수는 2.33으로 분석되었다. 결과적으로 공기 대물 히트 펌프의 열원으로 온실내부 태양잉여열과 외부 공기열을 병용하고, 축열조 온도를 변온제어한 결과 일반적인 외기열 이용 축열운전과 축열조 항온제어에 비해 난방성능 계수가 39% 향상됨을 확인하였다.

The improvement of resistance performance for the 4.99 ton class fishing boats was shown. The 4.99 ton fishing boats are the most commonly used one in the Korean coastal region. The evaluation of resistance performance was estimated by the Computational Fluid Dynamics (CFD) analysis. The CFD simulation was performed by the validation for various types of bow shapes on the hull. The optimized hull form from the simulation was selected and showed the best resistance performance. This hull type was tested on the towing tank in the National Institute of Fisheries Science (NIFS). The effective horsepower (EHP) was estimated by the resistance test on the towing tank with the bare hull condition. The drag force on the three service speed conditions was obtained for the resistance analysis to power prediction. The measured drag forces are compared with the results from the CFD simulation with one another. As results of the model tests, it was confirmed that the shape of the bow is an important factor in the resistance performance. The effective horsepower decreased about 30% in comparison with the conventional hull form. Also, the resistance performance improved the reduction of required horsepower, which especially contributed to the energy-saving for the fisheries industry. In the CFD analysis, the resistance performance improved slightly. In this case, the ratio of the residual resistance (CR) in the total resistance (CT) was high. Therefore, the CFD analysis was not enough to satisfy with reflection for the free surface and wave form in the CFD procedure. Both model test and CFD calculation in this study can be applied to the initial design process for the coastal fishing vessel.

노즐 플레이트는 발전 설비의 증기 터빈에 장착되는 핵심 장비로서 터빈 내부의 blade는 고정익으로 서 터빈에 유입되는 수증기의 유입속도와 방향을 조절하여 회전익에 전달해 주는 역할을 한다. 이 노즐 플레이트에는 많은 블레이드들이 inner ring 및 outer ring에 용접 방식으로 제작되어 활용되고 있으나, 용접시의 열변형, 노즐 블레이드 피치간의 불균일에 의한 제품불량 등이 문제가 되고 있다. 더욱이 용접공정 및 후공정으로 인한 제작 기간이 증가하여 원가 상승의 요인이 되는 문제가 있다. 본 연구는 용접식 노즐 플레이트를 조립식으로 설계 변경하여 구조를 개선하고 이의 적용성을 점검하고자 한다. 적용 가능성을 확인하기 위한 방법으로서 노즐 플레이트의 응력해석으로 구조안정성을 점검하고 또한 플레이트의 성능을 테스트하는 장치가 필요하다. 노즐 플레이트의 공기 출구의 속도 노즐단의 엔탈피 효율 등을 측정하기 위한 장치는 공기 흡입구와 여과기, test section 등으로 구성하여 설계한다.

In this study, a new designed propeller was applied on 24 ton class squid jigging vessel to reduce of fuel consumption. The selected squid jigging boat was under construction at the shipyard to determine the resistance of the hull through the model experiment. The propeller design was carried out by using the experimental data and ITTC procedures. Sea trials were performed by measuring the speed and the horsepower required by the condition of five power levels of engine load, namely 70%, 80%, 90%, MCR and maximum engine power. The speed and delivered horse power were compared between the conventional propeller and the new design propeller. Delivered horse power by installing the new propeller takes 90% engine load at start-up conducted by decreased 9.06%. The measuring speed is increased up to the 0.6 knots in the low-speed range to high range. This study showed that only the design and installation of a new propeller can improve the propulsion efficiency of the boats; furthermore, reduce fuel costs can be achieved at the same time by improving the increased cruising speed.

To overcome recent emission regulation, various hybrid systems are being developed. In the E-4WD(electric four wheel drive) system, the engine and transmission drive the front wheel, electric motor and single reduction gear drive the rear wheel. As the gear ratio of the reduction gear set determines the electric motor's operating point, the gear ratio is important to enhancement efficiency of hybrid system. This study is to analyze motor reduction gear ratio's influence on E-4WD hybrid system for optimized efficiency and driving performance. Fuel economy, operating point of power source and hybrid mode are analyzed using simulation developed with dynamic programming method.

Because National Fire Safety Codes is mixed performance criteria and specification, and it defines the fire extinguish equipment type and standards that need to be installed in a building as one method. Therefore, to fully reflect the fire risk characteristics of the building, such as the wooden building there is a limit. In this study, suggested to the performance criteria drawn methodologies through fire load of wooden buildings studies, theory on performance and performance analysis to fire extinguish equipment of the wooden buildings is installed according to current fire safety codes.