• 한국유체기계학회 논문집
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• 제17권6호
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• pp.64-68
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• 2014

This paper is intended to provide experimental data for the design of the small VAWT(vertical axis wind turbine). Three types(lift, drag, and hybrid) of the blade of VAWT are tested with digital wind tunnel in this study. From the test, the relation of power coefficient and tip speed ratio for the blades are evaluated and compared each other depending on the blade type. Especially, the characteristics of hybrid blade which is shown to be expanded in the market without any logical data is proposed in the relation of power coefficient and tip speed ratio. It is shown that the hybrid blade can be used to make higher starting torque with trade off of degradation of power coefficient.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1465-1469
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• 2009

Darrieus wind turbine blade is one of the vertical wind power system in which the lift of blade is used. In the calculation of wind power for the type of that, the multiple streamtubes method is known as an effective method. But it has big difference in the region of higher tip speed ratio because the incoming air velocity is used in the calculation of lift. The incoming air velocity is reduced from inlet to outlet continually by transferring energy to the wind blade. In this study, the air velocity on the blade, which is called blade velocity, is obtained with newly developed algorithm and used to determine the lift. And it is verified that applying blade velocity on the lift calculation cause the power prediction to improve dramatically in the region of higher tip speed ratio.

• Journal of Advanced Marine Engineering and Technology
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• 제23권2호
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• pp.252-258
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• 1999

As an effective means to convey crushed materials from seabed to on board ship and to raise hazardous or abrasive liquids air-lift pump provides a reliable mechanism due to its simple config-uration and easy-to-operate principle. The present study is focused on fundamental investigation of related performance by the analysis program based on the gas-liquid two-phase flow in circular pipes. The program covers pump operating in isothermal and vertical two-phase flow with Newto-nian liquids. it is summarized as important result that an optimum air mass flow rate exists for the maximum lifted liquid mass flow rate in terms of a given submergence rates and furthermore attachment of downcomer gives little effects on riser performance the conveyed liquid flow rate increases with larger submergence rate.

• 한국군사과학기술학회지
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• 제24권3호
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• pp.255-263
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• 2021

This paper investigates numerically the effect of rotor hub vibratory load components on the airframe vibration responses of high-speed compound unmanned rotorcraft (HCUR) using a lift-offset coaxial rotor, wings, and two propellers. The rotor hub vibratory loads are predicted using a rotorcraft comprehensive analysis code, CAMRAD II, and the airframe vibration responses are calculated by a finite element analysis software, MSC.NASTRAN. It is shown that the vibratory hub pitch moment of a lift-offset coaxial rotor is the most dominant component for both the longitudinal and vertical vibration responses at four specified locations of the airframe.

• Journal of Biosystems Engineering
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• 제8권2호
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• pp.1-10
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• 1983

The resulting characteristics of vibrations show different patterns for the various oscillating mechanisms. These vibrations causes troublesome operation problems for the operators and sometimes for the machines. Furthermore, in some cases the practical usage of this oscillating mechanism is constrained by its mechanical conditions. In this study, a balanced oscillating tillage tool with triple blades having different acting area was designed. The horizontal and vertical oscillating accelerations and draft power requirement due to the various travel speeds, lift angles, amplitudes and oscillating frequencies were investigated in a laboratory soil bin with a soil having invariable properties. The results obtained are summarized as follows: 1. Overall, the horizontal acceleration decreased as the oscillating frequency and amplitude decreased. But the increase in travel speed caused the decrease horizontal acceleration. The blade with the lift angle of $30^{\circ}$ exhibited the lowest value of horizontal acceleration among the blades tested. 2. For the vertical acceleration, the fluctuating trend of oscillating acceleration was similar to the trend of the horizontal acceleration. 3. The draft power requirement decreased as the amplitude and oscillating frequency increased. But the increase in travel speed caused the increase in draft power requirement. The blade with the lift angle of $10^{\circ}$ showed the lowest value of draft power requirement among the blades tested.

• 한국건설관리학회논문집
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• 제13권2호
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• pp.110-119
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• 2012

초고층 건축물의 수요가 늘어나면서 수직 양중 계획과 장비에 대한 중요성이 증대되고 있으며, 경제적이고 효율적인 리프트 사용을 위하여 무인 리프트의 사용 비중이 늘어나고 있다. 하지만 리프트의 정지위치 에러가 발생하거나 누적되는 경우 작업 효율성이 떨어지고, 문제 해결을 위해 리프트 업체가 리프트를 재 세팅 하는 동안 리프트 사용이 불가하게 되어 공사 진행에 장애가 된다. 본 연구에서는 리프트 정지위치 에러에 의한 시간 및 비용 손실을 방지하기 위해 리프트 정지위치 감지장치를 개발하였다. 실험을 통해, 정지위치 에러 발생 시 이를 보정하는 기능을 검증하였고, 정확도도 약 9.75mm 증가하는 것을 확인하였다.

• 대한수학회논문집
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• 제35권3호
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• pp.1019-1035
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• 2020

In this paper, we introduce the deformed-Sasaki metric on the tangent bundle TM over an m-dimensional Riemannian manifold (M, g), as a new natural metric on TM. We establish a necessary and sufficient conditions under which a vector field is harmonic with respect to the deformed-Sasaki Metric. We also construct some examples of harmonic vector fields.

• 충청수학회지
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• 제31권4호
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• pp.421-427
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• 2018

The aim of this study is to investigate the prolongations of G-structures immersed in the generalized almost r-contact structure on a manifold M to its tangent bundle T(M) of order 2. Moreover, theorems on Hsu structure, integrability and (${F\limits^{\circ}},\;{{\xi}\limits^{\circ}}{{\omega}\limits^{\circ}}_p,\;a,\;{\epsilon}$)-structure have been established.

• 대한수학회논문집
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• 제36권3호
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• pp.575-592
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• 2021

In this paper, we introduce the Berger type deformed Sasaki metric on the cotangent bundle T^*M over an anti-paraKähler manifold (M, 𝜑, g) as a new natural metric with respect to g non-rigid on T^*M. Firstly, we investigate the Levi-Civita connection of this metric. Secondly, we study the curvature tensor and also we characterize the scalar curvature.

• 한국건설관리학회논문집
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• 제14권5호
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• pp.153-163
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• 2013

건축물이 고층화, 대형화 될수록 수직 양중 계획 및 운영에 관한 중요성이 부각되고 있다. 이에 프로젝트 초기 단계에 실제 모델과 유사한 건설용 리프트 양중계획을 수립하려는 노력이 계속되고 있지만 프로젝트 착수 후 리프트 운행을 컨트롤 할 수 있는 시스템은 부재한 실정이다. 따라서 본 논문에서는 건설용 리프트 운영 효율증대를 위하여 센서를 사용한 리프트 운행 정보를 수집하고 실시간 분석이 가능한 건설용 리프트 최적화 운행 시스템 개발을 실시 및 검증 단계를 수행하여, 양중 효율의 지표가 되는 사용자 대기 시간의 단축을 도모하고 향후 무인 스마트 리프트의 초석이 되는 시스템을 제시하고자 한다.