• Nuclear Engineering and Technology
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• 제23권3호
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• pp.306-315
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• 1991

본 연구는 두개의 직선 pipe가 elbow로 연결된 piping system의 내부에 유체가 흐를때 발생하는 out-of-plane 운동을 다루었으며, Extended Hamilton's principle을 이용하여 운동방정식을 유도하였다. clamped-clamped, clamped-pinned; pinned-pinned인 경계조건을 갖는 piping system의 경우, dynamic instability는 일어나지 않음을 고찰하였으며, 각 경계조건에 대한 진동수 방정식으로부터 고유진동수의 수치해를 얻었다. 유체의 속도와 Coriolis힘이 진동수에 미치는 영향을 고찰하였고, 유체의 속도와 압력이 어느값을 넘어설때 buckling-type instability가 일어남을 알았다. 그리고 유체의 속도와 압력의 함수로 등가임계속도를 정의하고 여러가지 경계조건에 대해 buckling 이 일어나는 등가임계속도를 계산하였다.

• 전기학회논문지
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• 제61권3호
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• pp.413-421
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• 2012

This paper proposes the design and implementation of fluid flow generation system by using polypropylene(PP) water capture, which harvests electric energy from the kinetic energy of tidal current or water flow and drives the desired load, and applies it to the discharge drain of Hadong thermal power plant. This experimental system is composed of water captures, driving wheel, gear trains, 10[kW] synchronous generator, and three phase rectifying circuit which drives lamp load for test. The proposed water capturing system which is composed of water captures, rope and driving wheel, rotates as caterpillar according to water flow. This system is very easy to manufacture and more economical than another type of tidal current turbines such as conventional propeller and helical type. Also, we estimated the available fluid flow energy that can be extracted from the cooling water in discharge drain based on drain's cross-sectional area. Therefore, this paper confirms the validity of proposed fluid flow generation system with water captures and the possibility of its application for renewable energy generation in discharge drain of thermal power plant, from the obtained performance characteristic of this energy conversion system.

• KSBB Journal
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• 제23권1호
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• pp.48-53
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• 2008

토마토의 locular fluid로부터 최종적으로 Sephadex G-200 affinity chromatography에 의해 lectin을 분리한 다음, 이들의 분자량, 적혈구 응집력, 혈액특이성, 열 안정성, 최적 온도 및 pH 안정성의 생화학적 성질을 연구하였다. SBS-PAGE의 결과, 분자량이 39 kDa와 23 kDa로서 각각 2개의 subunit로 구성된 124 kDa의 분자량을 가지는 tetramer이다. 트립신으로 처리된 사람의 A, B, O, AB형의 혈액을 사용하여 각각의 혈구응집반응을 확인한 결과, A, B, O, AB형 모두에서 응집반응이 일어났으며, 이 중 B형 혈액에서 가장 높은 활성을 나타냈으며, A와 O형은 중간, AB형은 가장 낮은 활성을 보였다. 분리된 토마토 locular fluid의 최적반응 온도는 $50^{\circ}C$로서, 가장 높은 $70^{\circ}C$를 포함하는 $40-80^{\circ}C$에서 열 안정성을 보였으며, 이의 최적 pH는 7.0이다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.313-320
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• 2002

A new semi-active control strategy for seismic response reduction using a neuro-controller and a magnetorheological (MR) fluid damper is proposed. The proposed control system consists of the improved neuro-controller and the bang-bang-type controller. The improved neuro-controller, which was developed by employing the training algorithm based on a cost function and the sensitivity evaluation algorithm replacing an emulator neural network, produces the desired active control force, and then the bang-bang-type controller causes the MR fluid damper to generate the desired control force, so long as this force is dissipative. In numerical simulation, a three-story building structure is semi-actively controlled by the trained neural network under the historical earthquake records. The simulation results show that the proposed semi-active neuro-control algorithm is quite effective to reduce seismic responses. In addition, the semi-active control system using MR fluid dampers has many attractive features, such as the bounded-input, bounded-output stability and small energy requirements. The results of this investigation, therefore, indicate that the proposed semi-active neuro-control strategy using MR fluid dampers could be effectively used for control of seismically excited structures.

• 한국정밀공학회지
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• 제19권11호
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• pp.37-45
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• 2002

This paper presents the field-dependent Bingham characteristics and damping force control of an electro-rheological (ER) fluid under squeeze mode operation. The squeeze force of the ER fluid due to the imposed electric field is analyzed and an appropriate size of the disk-type electrode is devised. On the basis of the theoretical model of the ER fluid under squeeze mode operation, the yield stress and response speed of the ER fluid are distilled from the time responses of squeeze force to the step electric potentials. Measured squeeze forces under various excitation conditions are compared with the predicted ones from Bingham model and time constant obtained at the transient response test. In addition, the controllability of the field-dependent damping force of the ER fluid under squeeze mode is experimentally demonstrated by implementing simple PID controller.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.351-358
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• 2001

In this study, for the investigation of effects of several parameters, such as fluid mesh boundary size, cylinder or block shape, dimensions of depth, breadth and length at free suface, and fluid mesh element size to the depth direction on a reliable shock response of finite element model under underwater explosion with consideration of the bulk cavitation analysis of a simplified surface ship was carried out using the LS-DYNA3D/USA code. The shock responses were not much affected by the fluid mesh parameters. The computational time was greatly dependent on the number of DAA boundary segments. It is desirable to reduce the DAA boundary segments in the fluid mesh model, and it is not necessary to cover the fluid mesh boundary to or beyond the bulk cavitation zone just for the concerns about an initial shock wave response. It is also the better way to prefer cylinder type of the fluid mesh model to the block one.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.946-949
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• 2003

This paper reports on the fluid flow simulation results of a multilayer type piezoelectric valve. The mechanical and fluidic analysis are done by finite element method. The designed structure is normally closed type using buckling effect, which is consist of three separate structures; a valve seat die, an actuator die and a MLCA(Multilayer Type Ceramic Actuator). It is confirmed that the complete laminar flow and the lowest flow leakage are strongly depend on the valve seat geometry. In addition, turbulent flow was occurs in valve outlet according to increase seat dimension, height and inlet pressure. From this, we was deducts the optimum geometry of the valve seat and diaphragm deflection that have an great influence fluid flow in valve. Thus, it is expected that our simulation results would be apply for piezoelectric applications such as valve and pump, fluidic control systems.

• 한국기계가공학회지
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• 제19권8호
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• pp.8-14
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• 2020

In the air current pulverizing type grinding method, the blade wings fitted inside a casing are rotated at a high speed to generate a cornering air current, which facilitates the collision of materials with one another, leading to the pulverizing phenomenon. In contrast to mechanical grinding, grit pulverizing leads to fine grinding and less acid waste and degeneration of the material. Moreover, this approach prevents the loss of nutritional value, while allowing the milling grain to have an excellent texture. However, the existing air current pulverizing type machines consist of prefabricated blades, which cannot be rotated at a speed higher than 5,000 rpm. Consequently, the grinding process becomes time consuming with a low productivity. To overcome these problems, in this study, the shape and structure of the air current pulverizing type wings were optimized to allow rapid grinding at more than 8,000 rpm. Moreover, the optimal design for the ripening parts for the air current pulverizing type device was determined by performing a computational fluid dynamics analysis based on airflow analyses to produce machinery that can grinding materials to the order of micrometers.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.304-311
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• 2001

This research numerically analyzes the dynamic characteristics of a coupled journal and thrust hydrodynamic bearing due to its groove location which has the static load due to the weight of a rotor in the axial direction and the dynamic load due to its mass unbalance in the radial direction. The Reynolds equation is transformed to solve a plain member rotating type of journal bearing(PMRJ), a grooved member rotating type of journal bearing (GMRJ), a plain member rotating type of thrust bearing (PMRT) and a grooved member rotating type of thrust bearing (GMRT). FEM is used to solve the Reynolds equations in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors, such as whirl radius or floating height of a rotor, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. This research shows that the groove location affects the pressure distribution in the fluid film and consequently the dynamic performance of a HDD spindle system.

• 수산해양기술연구
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• 제56권4호
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• pp.395-406
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• 2020

The objectives of this study were to develop the optimal structures of recirculating aquaculture tank for improving the removal efficiency of solid materials and maintaining water quality conditions. Flow analysis was performed using the CFD (computational fluid dynamics) method to understand the hydrodynamic characteristics of the circular tank according to the angle of inclination in the tank bottom (0°, 1.5° and 3°), circulating water inflow method (underwater, horizontal nozzle, vertical nozzle and combination nozzle) and the number of inlets. As the angle in tank bottom increased, the vortex inside the tank decreased, resulting in a constant flow. In the case of the vertical nozzle type, the eddy flow in the tank was greatly improved. The vertical nozzle type showed excellent flow such as constant flow velocity distribution and uniform streamline. The combination nozzle type also showed an internal spiral flow, but the vortex reduction effect was less than the vertical nozzle type. As the number of inlets in the tank increased, problems such as speed reduction were compensated, resulting in uniform fluid flow.