• Smart Media Journal
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• v.9 no.4
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• pp.176-186
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• 2020

The size and shape of crops are diverse, and the growing environment is also different. Therefore, when one uses a drone to spray pesticides, the characteristics of each crop must be considered, and flight conditions such as the flight height and forwarding velocity of the drone should be changed. The droplet flow of pesticides is affected by various flight conditions, and a large change occurs in the sprayed area. As a result, an uneven distribution of liquid may be formed at the wake, and the transport efficiency will be decreased as well as there would be a risk of toxic scatter. Therefore, this paper analyzes the degree of distribution of pesticides to the crops through numerical analysis when pesticide is sprayed onto the selected three crops with different characteristics by using agricultural drones with different flight conditions. On the purpose of establishing a guideline for spraying pesticides using a drone in accordance with the characteristics of crops, this paper compares the amount of pesticides distributed in the crops at the wake of nozzle flow using the figure of merit, and the sum of transported liquid rate divided by the root mean square of the probability density function.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.307-312
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• 2023

In this study, a catalytic oxidation-heat recovery system was designed that can remove unreacted with a concentration of about 1% to 6% in the exhaust gas of hydrogen fuel cells and recover heat to ensure safety in the hydrogen economy. The safety system was devised by filling hydrogen oxidation catalysts at room temperature that can remove unreacted hydrogen without any energy source, and an exhaust-heat recovery device was integrated to efficiently recover the heat released from the oxidation reaction. Through CFD analysis, variations in pressure and fluid within the system were shown depending on the filling conditions of the hydrogen oxidation system. In addition, it was found that waste heat could be recovered by optimizing the temperature of the exhaust gas, flow rate, and pressure conditions within the heat recovery system and securing hot water above 40 ℃ by utilizing the exhaust gas oxidation heat source above 300 ℃. Through this study, it was possible to confirm the potential of utilizing hydrogen processes, which are applied in small to medium-sized systems such as hydrogen fuel cells, as a safety system by evaluating them at a pilot scale. Additionally, it could be a safety guideline for responding to unexpected hydrogen safety accidents through further pilot-scale studies.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.3
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• pp.381-395
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• 2023

This paper presents a GIS-based site suitability analysis for a smart hydrogen energy plant in the Gangwon-Do region, South Korea. A GIS-based multi-criteria decision analysis (MCDA) was implemented in this study to identify the most suitable sites for the development of smart hydrogen energy plants. The study utilizes various spatial data layers, including hydrogen generation potential and climatic conditions, environmental and topographic conditions, and natural catastrophic conditions, to evaluate the suitability of potential sites for the hydrogen energy plant. The spatial data layers were then used to rank and prioritize the sites based on suitability. The findings revealed that 4.26% of the study area, or 712.14 km², was suitable for constructing smart hydrogen energy plants. Some regions of Cheorwon-gun, Chuncheon-si, Wonju-si, Yanggu-gun, Gangneung-si, Hoengseong-gun, and near the coastal region along the east coast were found to be suitable for solar and wind energy utilization. The proposed MCDA provides a valuable tool for decision-makers and stakeholders to make informed decisions on the location of smart hydrogen energy plants and supports the transition to a sustainable and low-carbon energy system. Decision-makers can use the results of this study to select suitable sites for constructing smart hydrogen energy plants.

• Composites Research
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• v.30 no.5
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• pp.297-302
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• 2017

Finite element analysis of T-beam laminate structure under bending-torsional loading was conducted to prevent the delamination which is the major failure behavior on laminated composites. Three-dimensional preform, which is that fabric is braided through thickness direction, is suggested from the laminate analysis. The analysis aimed to optimize the fiber ratio in laminated composites. After it is suggested that guideline for design of T-beam structure using commercial software ANSYS Composites PrePost. The results show that strength of T-beam structure is increased 21.6% when the fiber density along with beam length direction is two times bigger than transverse direction. It is expected that development of high strength T-beam structure using designed three-dimensional preform.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.3
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• pp.303-309
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• 2015

In this study, a vehicle dynamic analysis and roller rig test were performed to evaluate the applicability of a suspensionless composite bogie to railway vehicles. A vehicle dynamic analysis was carried out under different rubber bushing stiffness values. The stiffness of the rubber bushing that plays a role in guiding wheel sets was varied in the range of 10-100 MN/m, in 10-MN/m steps. Based on the results, the composite bogie with a rubber bushing stiffness of more than 40 MN/m satisfied the design requirements. In addition, a rubber bushing with a stiffness of 81 MN/m was fabricated, and a roller rig test was performed. Based on the test results, the vehicle equipped with the composite bogie had a critical speed of 363 km/h, which agreed with the simulation result within an error of 10%.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.73-79
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• 2002

Fretting wear test in room temperature air was performed to evaluate the wear mechanism of fuel rod using a fretting wear tester, which has been developed for experimental study. The main focus was to compare the wear behaviors of fuel rod against support springs at different contact geometries (i.e. concave and convex) and slip directions (axial and transverse). The wear on the tube was examined by the surface roughness tester, which measures the volume. The result indicated that with change of contact geometry from 5N of normal load to 0.1mm gap, wear volume of tube Increased in the condition of concave spring, but slowly decreased in convex spring. From the results of SEM observation, wear mechanism of each test condition was also depend on the above contact parameters. The wear mechanism of each test condition in room temperature air is discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.235-240
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• 2011

A flexible hose attached to a mother ship experiences various motions that depend on the movement of the mother ship and that of underwater vehicle. Although the motion of the hose is a very important factor that determines how a mother ship should be steered in a real situation, it is difficult to experimentally obtain information about the hose motion. Therefore, we study the motion of the hose analytically. The ANCF(absolute nodal coordinate formulation) was used to model the hose, because this formulation can relax the Euler-Bernoulli theory and the Timoshenko beam theory and allow the deformation of the cross section. The mother ship is assumed to be a rigid body with 6 degrees of freedom. The motion of the hose is predominantly affected by the behavior of the mother ship and by the fluid flow.

• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.367-370
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• 2012

본 연구는 하나의 장치 내에서 "싸이클론-관성충돌-여과포 집진"이라는 다단 제진 단계가 동시에 이루어져 입경 분포별로 순차적인 제진이 가능한 멀티 집진기의 처리가스 제어 효율을 극대화시킬 수 있는 기류 흐름을 얻기 위한 최적화 설계 조건을 검토하는 것이다. 우선 1단계 제진 과정인 원심력을 이용하여 조대입자의 유선 이탈을 촉진시킬 수 있는 사이클론 유동을 최적화시키기 위한 집진기 입구 형상 설계 검토를 위해 수치 해석적 연구를 수행하였다. 그 결과, 멀티집진기 입구 형상을 일반적인 설계 방식인 접선 유입식으로만 설계한 것에 비해 선회류를 한번 더 가속화시킬 수 있는 가이드 베인을 추가로 설계한 경우 선회류의 pitch가 짧고 강하게 형성되어 사이클론부에서 조대입자의 유선 이탈을 촉진시키는데 매우 효과적인 것으로 예측되었다. 단, 사이클론부 하단 벤츄리 형상으로 인해 약 4~5 m/s의 강한 하향 흐름이 호퍼 하단까지 형성되고 있어 탈리 분진의 재비산 문제가 발생할 가능성이 크므로 벤츄리 형상 설치 유무에 대한 영향도 추가적으로 연구가 필요할 것으로 판단된다.

• Journal of Digital Convergence
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• v.12 no.7
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• pp.21-36
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• 2014

The purposes of the study was to investigate BYOD (Bring Your Own Device) policy since it would be limited to distribute all of the digital devices required for the schools within the budget of the government. First, the concept and characteristics of BYOD were introduced. Then, the pros and cons of BYOD were analyzed according to the case studies of BYOD policies of the U.S. Based on the previous experiences, guidelines of domestic BYOD policies were established. Regarding the institutional aspect, technical issues, usage, damages, digital divide, information security, and resources were discussed. Additionally, conditions of technology, networks, filtering, software were also considered as essential infrastructure. In sum, as an alternative of distributing digital devices in schools, the importance of BYOD should be regarded as top priorities with systematic preparations in launching digital education. It would be expected that this study play a fundamental role in launching domestic BYOD policy by supporting specific strategies.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.6
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• pp.70-77
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• 2011

A ventilation-relief valve performs as a safety-valve assembly for the liquid-propellant feeding system of space launch vehicle. This valve plays a role of relieving the vaporized propellants from propellant tanks during the filling and storing stages of propellants. Also it regulates to maintain the pressure of ullage volume of on-board propellant tanks within the safety-margin during the flight. The simulation model of ventilation-relief valve is designed with AMESim to predict and evaluate the dynamic characteristics and pneumatic behaviors of valve. To validate a valve simulation model, the simulation results of the opening and closing pressures and their operating durations of valve by AMESim analysis are compared with the results of mathematical methods. In addition, the results of internal flow simulation with FLUENT are utilized to improve the accuracy of valve-modeling. This study will serve as one of reference guides to enhance the developmental efficiency of ventilation-relief valves with the various operating conditionss, which shall be used in Korea Space Launch Vehicle-II.