• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.3
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• pp.56-66
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• 2013

Weight reduction of the VTHL / TSTO type of the reusable launch vehicles using RBCC engines are investigated. To predict weight and thrust of the vehicles, equations of motion are analyzed. Analysis results are compared with specifications of existing launch vehicles for validations. For the mission of inserting 2.5 ton payload to 200 km circular orbit, the case A, which uses the RBCC engine in the 1st stage shows smaller weight than the case B, which uses the RBCC engine in the 2nd stage. The weight of the case A shows only 25.8% of a existing rocket launch vehicle's weight.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.12
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• pp.663-672
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• 2017

Building information modeling (BIM) technology based on 3D modeling has been applied to the entire domestic construction industry since 2010. It can calculate quantity take-off considering construction productivity at design phase. Based on this, it is possible to improve the reliability of construction cost prediction of design phase in the process of cost estimation. However, Building Information Level (BIL) defined by Ministry of Land, Infrastructure and Transport and Public Procurement Service does not seem to offer doable environment due to the lack of detailed application items. By calculating construction cost that meets Construction Cost Estimate Accuracy by American Association of Cost Engineers (AACE) through quantity take-off and cost estimation based on 3D modeling of BIM technology, a BIL improvement proposal at design phase for Mechanical Contracts and Construction is provided here. Results showed that properties including outline and minimum specification of the main equipment, internal main piping, and internal main duct should be defined from the intermediate design phase to have reliable cost estimation.

• Journal of Digital Contents Society
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• v.18 no.5
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• pp.889-894
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• 2017

The purpose of this paper is to implement smart farm using automatic navigation, short - range wireless communication network technology, and automatic take - off and landing system using unmanned aerial vehicle to maximize the efficiency of grazing farm management. The grazing pasture management system that integrates ICT fusion technology for the activation of the mountain ecological livestock production is expected to contribute to the improvement of the productivity of the grazing livestock, the infrastructure to produce the excellent quality, and the competitiveness of the livestock industry in response to the FTA. And it will contribute to the improvement of career force through the supply to the farmhouse.

• Journal of the Ergonomics Society of Korea
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• v.20 no.2
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• pp.47-57
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• 2001

To simulate an actual slip to measure floor slipperiness, slip resistance testers simulate slip in only forward direction because forward slip in the landing phase was found to be the most important factor for loss of balance. Backward slip in the take off phase was possible but was excluded in the friction test protocol because it was not dangerous. However, backward slip was tested in the friction test protocol without any theoretical background of the significance in generating dangerous slips and falls and was proven to be as good as forward slip in measuring floor slipperiness. Therefore, this study was designed to investigate the significance of backward slip in generating dangerous slips and falls with different combinations of floor and shoe sole. The results showed different tendency of backward slip in take off phase being significant in generating dangerous slips and falls because backward slip in the takeoff phase affected gait pattern disturbances seriously. resulted in dangerous falls. Fast toe velocity increased the severity of backward slip and confirmed the significance of backward slip in generating dangerous slips and falls. As a result, this study recommends the utilization of backward slip in the measurement of floor slipperiness.

• Nuclear Engineering and Technology
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• v.36 no.2
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• pp.142-152
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• 2004

The liquid entrainment and vapor pull-through offtake model of RELAP5/MOD3 had been developed for SBLOCA (Small Break Loss of Coolant Accident). The RELAP5/MOD3 model for horizontal volumes accounts for the phase separation phenomena and computes the flux of mass and energy through a branch when stratified conditions occur in the horizontal pipe. In the case of CANDU reactor, this model should be used in the coolant flow of 95 feeders connected to the reactor header component under the horizontal stratification in header. The current RELAP5 model can treat the only 3 directions junctions; vertical upward, downward, and side oriented junctions, and thus improvements for the liquid entrainment and vapor pull-through model were needed for considering the exact angles. The RELAP5 off-take model was modified and generalized by considering the geometric effect of branching angles. Based on the previous experimental results, the critical height correlation was reconstructed by use of the branch line connection angle and validation analyses were also performed using SET. The new model can be applied to vertical upward, downward and angled branch, and the accuracy of the new correlations is more improved than that of RELAP5.

• Journal of Ocean Engineering and Technology
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• v.30 no.5
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• pp.361-366
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• 2016

The aim of this study was to experimentally investigate the hydrodynamic performance of a hemispheric wave energy converter (WEC) and its wave power takeoff. The WEC is a heaving body-type point absorber with a hydraulic-pump power take-off (PTO) system. The hydraulic PTO system consists of a hydraulic cylinder, hydraulic motor, and generator, with consideration given to the hydraulic pressure and flow rate. Two body model shapes, including the original hemisphere and a bottom-chopped hemisphere, were considered. The heave RAOs of the two models were evaluated for various body drafts. The effects of the hydraulic PTO system on the RAOs were also investigated.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.3
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• pp.99-106
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• 2011

50kW급 동체회전형 파력발전시스템(WEC;wave energy converter)의 전력변환장치(PTO; power take-off)를 설계 제작한 후 성능시험을 하였다. 파력발전시스템은 2개의 실린더형 동체가 회전관절로 연결된 구조로 수면의 반정도 잠기는 구조로 되어있다. 파랑에 의해 유도된 회전관전의 움직임이 유압실린더에 힘을 가해주며, 유압실린더는 고압의 작동유를 축압기를 경유하여 발전기에 체결된 유압모터로 공급한다. 유압식 PTO은 유압실린더가 왕복운동하는 움직임을 이용하여 고품질의 전력을 생산하는데 효과전인 수단을 제공한다. 파력발전시스템의 경제성은 PTO의 에너지 변환 효율에 크게 의존한다. 발전기를 AC 380V 전력계통에 연계시킨 후, 발전기에서 나오는 출력이 5, 20, 35, 43kW 일때 PTO 전체와 개별기기에 대한 효율을 측정하였다. 본 논문에서 유압식 PTO시스템의 설계에 대해 설명하였으며 효율 향상에 초점을 맞추어 PTO 성능대해 분석하였다.

• Smart Structures and Systems
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• v.18 no.3
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• pp.425-448
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• 2016

In this paper, a new Pigeon Colony Algorithm (PCA) based on the features of a pigeon colony flying is proposed for solving global numerical optimization problems. The algorithm mainly consists of the take-off process, flying process and homing process, in which the take-off process is employed to homogenize the initial values and look for the direction of the optimal solution; the flying process is designed to search for the local and global optimum and improve the global worst solution; and the homing process aims to avoid having the algorithm fall into a local optimum. The impact of parameters on the PCA solution quality is investigated in detail. There are low-dimensional functions, high-dimensional functions and systems of nonlinear equations that are used to test the global optimization ability of the PCA. Finally, comparative experiments between the PCA, standard genetic algorithm and particle swarm optimization were performed. The results showed that PCA has the best global convergence, smallest cycle indexes, and strongest stability when solving high-dimensional, multi-peak and complicated problems.

• Journal of the Korea Society of Computer and Information
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• v.24 no.2
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• pp.127-137
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• 2019

In this study, we have developed a calculation system for BIM-based quantities, 4D process, and 5D construction costs, by integrating object shape attributes and the standard classification system which consist of Cost Breakdown System(CBS), Object Breakdown System(OBS) and Work Breakdown System(WBS) in order to use for the 4 dimensional process control of roads and rivers. First, a new BIM library database connected with the BIM library shape objects was built according to the CBS/OBS/WBS standard classification system of the civil engineering field, and a integrated database system of BIM-based quantities, process(4D), and construction costs(5D) for roads and rivers was constructed. Nextly, the process classification system and the cost classification system were automatically disassembled to the BIM objects consisting of the Revit-family style elements. Finally, we added functions for automatically generating four dimensional activities and generating a automatic cost statement according to the combination of WBS and CBS classification system The ultimate goal of this study was to extend the integrated quantities, process(4D), and construction costs(5D) system for new roads and rivers, enabling the integrated use of process(4D) and construction costs(5D) in the design and construction stage, based on the tasks described above.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.143-151
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• 2021

The purpose of our study is to confirm the trend of the muscle activity of the trunk and lower limb muscles by the attack method and phase during volleyball exercise. To achieve this purpose, spike serve and spike were conducted for 9 male middle school students, and at that time, it was divided into four phase, such as run jump, take off, impact, and follow, and the rectus abdominis, erector spine, and left rectus femoris, left biceps femoris, left anterior tibialis, left gastrocnemius midialis, right rectus femoris, right biceps femoris, right anterior tibialis, right gastrocnemius midialis, were examined. Spike serve and spike were each performed three times, and randomly cross-allocated to extract accurate data. We was no difference in all muscles according to the attack method, and the muscle activity of the rectus abdominis was highest in the impact phase and the muscle activity of the vertebral spine muscle was highest in the close-up phase. In addition, all of the measured left and right lower limb muscles showed the highest muscle activity between the assisted devices. As a result, We found out that regardless of the method of spike serve and spike, the lower limbs in the run-up phase for a high jump, the vertebrae in the take off phase, the preparation phase for hitting the ball strongly, and in the impact phase at the moment of hitting the ball. It can be seen that it exerts the greatest power in the rectus abdominis.