• Journal of Ocean Engineering and Technology
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• v.23 no.5
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• pp.39-44
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• 2009

The hydrostatic slipper bearing is generally used in high pressure axial piston pumps to support the load generated from two surfaces which are sliding relatively at low speed. The object of the bearing is to remove the possibility of direct contact by maintenance of an adequate oil film thickness between two metal surfaces. Because the bearing performance is influenced by the bearing deformation, it is highly dependent on the injection pressure, the bearing surface profile and so on. In this study, the deformation characteristics of a hydrostatic slipper bearing is investigated according to the injection pressure by the finite element analysis. In the analysis, the special boundary condition to take the fluid-structure interaction (FSI) into account is used on the interactive surface. The results, such as bearing deformation, stress and lifting force, obtained from the fully coupled analysis are compared with those from the single step sequential method.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.2
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• pp.1-6
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• 2022

Recently, the development of UAM, which was named by NASA as an alternative to solve the traffic and environmental problems caused by the rapidly progressing urbanization. When designing UAM, the location of lift fans greatly affects the core technology of the eVTOL type, distributed electric propulsion technology and aerodynamic performance of the vehicle. In this paper, a hybrid UAM model was designed using OpenVSP, an open source aircraft configuration modeling program, and aerodynamic analysis was performed according to the lift fans position change by the vortex lattice method. As a result, it is confirmed that the flight parameters and trailing wakes are stable by fixing the lift fan with the state rotated 0° to the flow direction of the aircraft during cruise flight. Also, OpenVSP is a suitable tool to be used in aircraft configuration modeling and design.

• International journal of advanced smart convergence
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• v.12 no.4
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• pp.353-360
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• 2023

This paper explores notable shifts in the restaurant startup market following the lifting of social distancing measures. Key trends identified include an escalated interest in startups, a heightened focus on the quality and diversity of food, a relative decline in the importance of delivery services, and a growing interest in specific industry sectors. The study's data collection spanned three years, from April 2021 to May 2023, encompassing the period before and after social distancing. Data were sourced from a range of online platforms, including blogs, news sites, cafes, web documents, and intellectual forums, provided by Naver, Daum, and Google. From this collected data, the top 50 words were identified through a refinement process. The analysis was structured around the social distancing application period, comparing data from April 2021 to April 2022 with data from May 2022 to May 2023. These observed trend changes provide founders with valuable insights to seize new market opportunities and formulate effective startup strategies. In summary, We offer crucial insights for founders, enabling them to comprehend the evolving dynamics in food service startups and to adapt their strategies to the current market environment.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.14-18
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• 2007

The ground effect on tilt-rotor UAV is analyzed by simulating the hovering UAV for various altitudes. Ground effect increases pressure beneath the UAV body and generates additional lifting force. The ground effect diminishes at altitude 3m and hovering UAV generates constant lifting force above 3m.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.48-53
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• 2011

Current trends in propeller design have led to the need for extremely complex blade shapes, which place great demands on the accuracy of design and analysis methods. This paper presents a new proposal for improving the prediction of propeller performance with a vortex lattice method using the lifting surface theory. The paper presents a review of the theory and a description of the numerical methods employed. For 8 different propellers, the open water characteristics are calculated and compared with experimental data. The results are in good agreement in the region of a high advanced velocity, but there are differences in the other case. We have corrected the parameters for the trailing wake modeling in this paper, and repeated the calculation. The new calculation results are more in agreement with the experimental data.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.807-812
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• 1995

In this study, comparisons were made among three representative methods for predicting compressive forces on the lumbosacral disc: LP-based model, double LP-based model and EMG-assisted model. Two subjects simulated lifting tasks that are normally performed in the refractories industry. In the refractories lifting tasks, vertical and horizontal distance, and weight of load were varied. To calculate the L5/Sl compressive forces, EMG signals from six trunk muscles were measured and postural data were recorded using the Motion Analysis System. The EMG-assisted model was shown to reflect well all three factors considered here. On the other hand, the compressive forces of the two LP-based models were only significantly affected by weight of load.

• Journal of the Korean Society of Safety
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• v.35 no.4
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• pp.40-47
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• 2020

Although gangform has good workability due to the integration of outer wall forms and working platforms, 22 workers were died from 21 gangform related accidents during 2012 to 2016. Quantitative risk assessment is required for evident based prevention measure selection. In this study, based on 52 accident data from 2004 to the first half of 2019, FTA is conducted for probabilities of direct causes and their contribution to accidents. Three stages are considered; gangform installation, dismantling and lifting, and using. The effectiveness of countermeasures is evaluated through minimum cut set, RAW and RRW. Complete assembly of gangform on the ground level, detailed planning, and fall prevention device are suggested as prevention measures for installation, dismantling and lifting, and using stages, respectively.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.251-255
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• 2008

Flow field around helicopter involves incompressible flow near the blade root and compressible flow at the blade tip. A problem occurs for low Mach number flow due to the stiffness of the governing equations. Time-derivative preconditioning techniques have been incorporated to reduce the stiffness that occurs at low speed region. The preconditioned form of the compressible Navier-Stokes and Euler equations is used. Computations are performed for the Caradonna-Tung's hovering and non-lifting forward flight case. Computational results are in good agreement with the experimental data.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.251-255
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• 2008

Flow field around helicopter involves incompressible flow near the blade root and compressible flow at the blade tip. A problem occurs for low Mach number flow due to the stiffness of the governing equations. Time-derivative preconditioning techniques have been incorporated to reduce the stiffness that occurs at low speed region. The preconditioned form of the compressible Navier-Stokes and Euler equations is used. Computations are performed for the Caradonna-Tung's hovering and non-lifting forward flight case. Computational results are in good agreement with the experimental data.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.156-158
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• 2008

Along the various gap distance between shoe and swash plate and pocket diameter, lifting force of piston shoe during the compressing stage was calculated. The flow in piston, orifice, shoe, and back space was considered to be 2-dimension axisymmetric and analysed by Fluent, a commercial CFD Software. The wall boundary condition was given as nonslip and adiabatic, while the change in fluid viscosity was considered as linear along temperature. Calculated lifting force and oil leakage of shoe was used in the design of a pump to confirm the shape of the shoe.