• Steel and Composite Structures
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• 제26권3호
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• pp.255-263
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• 2018

A steel-concrete composite (SC) panel typically consists of two steel faceplates and a plain concrete core. This paper investigated the impact response of SC panels through drop hammer tests and numerical simulations. The influence of the drop height, faceplate thickness, and axial compressive preload was studied. Experimental results showed that the deformation of SC panels under impact consists of local indentation and overall bending. The resistance of the panel significantly decreased after the local failure occurred. A three-dimensional finite element model was established to simulate the response of SC panels under low-velocity impact, in which the axial preload could be considered reasonably. The predicted displacements and impact force were in good agreement with the experimental results. Based on the validated model, a parametric study was conducted to further discuss the effect of the axial compressive preload.

• International Journal of Fluid Machinery and Systems
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• 제6권4호
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• pp.170-176
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• 2013

Counter Rotating Turbine (CRT) is an axial turbine with a nozzle followed by a rotor and another rotor that rotates in the opposite direction of the first one. Axial spacing between blade rows plays major role in its performance. Present work involves computationally studying the performance and flow field of CRT with axial spacing of 10, 30 and 70% for different mass flow rates. The turbine components are modeled for all the three spacing. Velocity, pressure, entropy and Mach number distributions across turbine stage are analyzed. Effect of spacing on losses and performance in case of stage, Rotor1 and Rotor2 are elaborated. Results confirm that an optimum axial spacing between turbine components can be obtained for the improved performance of CRT.

• Advances in biomechanics and applications
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• 제1권2호
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• pp.85-93
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• 2014

In this paper, two procedures of enumerating the axial rotation are proposed using the unit sphere of the spherical rotation coordinate system specifying 3D rotation. If the trajectory of the movement is known, the integration of the axial component of the angular velocity plus the geometric effect equal to the enclosed area subtended by the geodesic path on the surface of the unit sphere. If the postures of the initial and final positions are known, the axial rotation is determined by the angular difference from the parallel transport along the geodesic path. The path dependency of the axial rotation of the three dimensional rigid body motion is due to the geometric effect corresponding to the closed loop discontinuity. Firstly, the closed loop discontinuity is examined for the infinitesimal region. The general closed loop discontinuity can be evaluated by the summation of those discontinuities of the infinitesimal regions forming the whole loop. This general loop discontinuity is equal to the surface area enclosed by the closed loop on the surface of the unit sphere. Using this quantification of the closed loop discontinuity of the axial rotation, the geometric effect is determined in enumerating the axial rotation. As an example, the axial rotation of the arm by the Codman's movement is evaluated, which other methods of enumerating the axial rotations failed.

• 한국음향학회지
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• 제16권6호
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• pp.61-67
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• 1997

압전 회전센서(Piezoelectric Gyroscope)는 물체의 회전속도를 감지하기 위한 센서로서 압전효과를 이용해 코리올리스힘(Coriolis Force)을 측정하는 센서이다. 기존에 사용되고 있는 압전 회전센서는 1축형이 주종을 이루고 있는데 비하여 본 연구에서는 한 차원 발전된 2축형의 회전센서를 고안, 제작하였다. 이러한 새로운 구조에 대한 검토 및 고찰을 위해 유한요소법 (Finite Element Method) 을 통한 동적 해석을 실시하여 구조의 타당성을 검증하고 각 설계인자 변화에 따른 센서의 특성변화를 조사하였다. 또한 그 결과를 토대로 직접 회전센서를 제작하여 그 성능을 평가, 비교하였다. 나아가 센서의 특성평가를 위한 회전 시뮬레이터를 구성한 후 정량적인 실험을 통해 제작된 센서의 반응을 조사하였으며, 그 결과 본 논문에서 개발된 2축형 센서는 두 방향의 회전력에 대한 우수한변별도 및 감도를 나타내어 새로운 형태의 회전 센서로서의 사용가능성을 확인할 수 있었다.

• 한국입자에어로졸학회지
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• 제5권2호
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• pp.37-43
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• 2009

Particulate matter (PM) is one of the major indoor air pollutants especially in the subway station in Korea. In order to remove PM in the subway station, several kinds of PM removal system such as roll-filter, auto-washable air filter, demister, and electrostatic precipitator are used in the air handling unit (AHU) of subway stations. However, those systems are prone to operation and maintenance problems since the filter-regeneration unit consisting of electrical or water jet parts might malfunction due to the high load of particulates unless the filter medium is periodically replaced. In this study, the use of axial-flow cyclone was proposed for particulate filter unit in the AHU for its low operation and maintenance cost. Novel shape of axial-flow cyclone was designed by using computational fluid dynamics (CFD). The shape of vortex vane was optimized in terms of pressure drop and tangential velocity. In addition, CFD analysis was validated experimentally through the pressure drop measurement of mock-up model. We found that pressure drop and tangential velocity of fluid through the axia-flow cyclone was significantly affected by the rotating degree of vortex vane and the numerical prediction of pressure drop agreed well with experimental measurement.

• Korean Chemical Engineering Research
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• 제54권4호
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• pp.527-532
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• 2016

감압상태(1torr)의 순환유동층 플라즈마 반응기(내경 10 mm, 높이 800 mm)에서 기상 유속과 고체순환속도가 축방향 고체체류량 분포에 미치는 영향을 연구하였다. 폴리스타이렌 고분자 입자와 질소가스를 고체 및 기상 물질로 각각 사용하였다. 감압상태 순환유동층의 고체 순환량 변화는 상승관의 많은 기체 유량(40~80 sccm)에 의한 변화만큼 고체재순환부의 작은 유량 변화(6.6~9.9 sccm)에 의해서도 가능하였다. 감압상태 순환유동층의 고체 순환속도는 재순환부 기체 유속에 따라 증가하였다. 상승관내의 축방향 고체 체류량 분포는 하부의 농후상 영역에서 상부의 희박상 영역까지 높이에 따라 감소하는 형태를 나타내었다. 상승관 내 각 높이에서 고체순환속도의 증가에 따라 직선적으로 고체 체류량이 증가하였다. 이로써 플라즈마 형성과 유지 그리고 플라즈마 반응을 위해 적절한 플라즈마 로드 위치를 결정할 수 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.719-724
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• 2003

The present experimental study deals with noise reduction and improvements in cooling performance in a plasma display panel(PDP) television (TV). To reduce the noise, the effects of installation parameters are studied. The experimental parameters under investigation are the distance between the fan and the rear case of a PDP TV, position of the strut on the fan, and the fan RPM. The variance of RPM is the most significant facto., and a 250 RPM decrease from 910 RPM causes about 4㏈(A) reduction in the system noise. To increase performance, flow characteristics are investigated by using a visualization technique and measuring the volume flow rate. The visualized results show that a radial direction flow due to large system resistance is significant, and an axial velocity oscillation is observed from the measurement of the volume flow rate. To prevent both a radial direction flow and an axial velocity oscillation, sponges are inserted in the space between f3n and the rear case. Inserted sponges improve the volume flow rate of cooling fans up to 32% since they convert a radial direction flow to an axial direction flow. Also an axial velocity oscillation with large amplitude and low RPM disappears. Increasing volume flow rate causes the PDP TV to improve its cooling performance. Additionally the same volume flow rate can be obtained with a decreased fan speed due to the inserted sponge. Noise reductions of 4.2 ㏈(A) at the rear and 1.1 ㏈(A) at the front of the TV are obtained by the decreased RPM. An increase of 10% of the volume flow rate is also achieved by inserting sponges.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1389-1394
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• 2004

Experiments were done for the unsteady flow in a counter rotating axial flow fan near peak efficiency and stall point. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional passage flow patterns were investigated through the acquired data by the $45^{\circ}$ inclined hot-wire. Comparison of flow characteristics between two different operating conditions such as tip vortex, secondary flow and turbulence intensity were performed through the analyses of axial, radial and tangential velocity distributions. As a result, tip vortex and secondary flows are enforced and measured obviously at stall point.

• Steel and Composite Structures
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• 제37권1호
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• pp.37-49
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• 2020

In this paper, free vibration finite element analysis of axially moving laminated composite beams subjected to axial tension is studied. It is assumed that the beam has a constant axial velocity and is subject to uniform axial tension. The analysis is based on higher-order theories that have been presented by Carrera Unified Formulation (CUF). In the CUF technique, the three dimensional (3D) displacement fields are expressed as the approximation of the arbitrary order of the displacement unknowns over the cross-section. This higher-order expansion is considered in equivalent single layer (ESL) model. The governing equations of motion are obtained via Hamilton's principle. Finally, several numerical examples are presented and the effect of the ply-angle, travelling speed and axial tension on the natural frequencies and beam stability are demonstrated.

• 한국산업융합학회 논문집
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• 제23권1호
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• pp.101-106
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• 2020

Along with dust collection efficiency, pressure loss is a very important cyclone operation factor. A severe rise in pressure loss causes the problem of cost. To solve the problem, the method connecting axial-vane type cyclones in parallel is suggested recently. The axial vane type cyclone dust collector applied in this study is a small portable type. Multiple cyclones are installed in a round type. The basic performance test on the axial vane type cyclone dust collector was conducted. As a result, the cut size reduced along with a rise in the wind velocity of the cyclone dust collector inlet. According to the test on dust collection efficiency, the effect of dust collection began to appear in the range of 3㎛ and dust collection efficiency was greatly improved at 5 ㎛. The noise of the cyclone dust collector well met the fan sound power level of KSB 6361.