• 대한조선학회지
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• 제23권2호
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• pp.33-45
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• 1986

In the present paper, the nonlinear analysis of dynamic response of the jacket type offshore structures subject to nonlinear fluid force is performed. Furthermore, several analysis methods, such as quasi-static analysis, Newmark-$\beta$ method and state vector time integration technique, and described and compared with each others in order to investigate the efficiency numerical of the schemes for this kind of nonlinear structural analysis. In the problem formulation, various environmental forces acting on the jacket type offshore structure have been studied and calculated. Particularly, hydrodynamic forces are calculated by using the Morison type formula, which contains the interaction effect between the motion of the structure and the velocity of fluid particles. Also, Stokes' 5th order wave theory and Airy's linear wave theory are used to predict the velocity distribution of the fluid particles. Finally, the nonlinear equation of motion of the structure is obtained by using three-dimensional finite element formulation. Based on the above procedures, two examples, i.e. a single pile and a typical offshore jacket platform, are studied in details.

• 한국유체기계학회 논문집
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• 제3권2호
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• pp.50-56
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• 2000

The effects of lobe shapes on the leak flow conductance of Roots-type vacuum pump are studied numerically and experimentally. The modelled lobe shape of Roots-type vacuum pump is two-lobe spur gear. The numerical analyses are performed on leak flows in Roots-type vacuum pump. It is numerically calculated using a 4th-order Runge-Kutta method and is compared with experimental results. Results show that for the case of involute lobe shape the total amount of the leak flow conductance is greater than that of cycloid and Cassini oval lobe shapes.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 춘계학술발표대회 논문집
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• pp.49-54
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• 2009

This study focus on verification of the thermal efficiency of volumetric receiver with $5kW_{th}$ Dish-type solar thermal system. Spiral flow path shaped on receiver and working fluid(steam) flow along the this flow path. Porous material for radiation-thermal conversion used in former researches are substituted with the stainless steel wall installed along the spiral shaped flow path. Numerical analysis for the flow path and temperature distributions are carried out. Numerical results are compared with experimental data. Using the numerical model, the heat transfer characteristics of spiral type receiver for dish-type solar thermal systems are known and the thermal performance of the receiver can be estimated.

• 한국유체기계학회 논문집
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• 제9권6호
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• pp.29-34
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• 2006

Propeller type pump has been widely used for pumping water in agricultural and manufacturing industry. Since a propeller type pump contains a screw impeller inside a circular casing, the numerical analysis becomes complex. However, the accurate prediction of viscous flow is essential for computing hydrodynamic performances. To analysis the flow and the performance of the propeller type pump, the present work has solved 3D incompressible RANS equations on the multiblocked grid. From the present calculation, small amount of flow separation was shown near hub and the flow was recovered to nearly uniform inflow after one diameter downstream. Torque and thrust coefficient were computed and compared with experiments.

• International Journal of Fluid Machinery and Systems
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• 제4권2호
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• pp.229-234
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• 2011

For Lift-type Vertical Axis Wind Turbine (VAWT), it is difficult to evaluate the performance through the scale-model wind tunnel tests, because of the scale effect relating to Reynolds number. However, it is beneficial to figure out the critical value of Reynolds number or minimum size of the Lift-type VAWT, when designing this type of micro wind turbine. Therefore, in this study, the performance of several scale-models of Lift-type VAWT (Reynolds number : $1.5{\times}10^4$ to $4.6{\times}10^4$) was investigated. As a result, the Reynolds number effect depends on the blade chord rather than the inlet velocity. In addition, there was a transition point of the Reynolds number to change the dominant driving force from Drag to Lift.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.472-475
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• 1997

It is well known that pneumatic motors convert fluid power into mechanical power with a low efficiency. The Value of the efficiency depends on several factors, of which the most important are ; type of motor, speed, supply pressure, sie and geometry of the motor. This paper presents an analytical and experimental study of the performance of he vane type pneumatic motors. This investigation deals with all the pneumatic motors. This investigation deals with all the pneumatic motors. This investigation deals with all the major aspects of the air flow through a vane type pneumatic motor and pints out which are the main causes of the low efficiency of the motor, and therefore indicates which changes in a motor design an lead to optimum performance.

• 한국유체기계학회 논문집
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• 제11권5호
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• pp.50-56
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• 2008

Metal cutting operations involve generation of heat due to friction between the tool and the pieces. This heat needs to be carried away otherwise it creates white spots. To reduce this abnormal heat cutting fluid is used. Cutting fluid also has an important role in the lubrication of the cutting edges of machine tools and the pieces they are shaping, and in sluicing away the resulting swarf. As a cutting fluid, water is a great conductor of heat but is not stable at high temperatures, so to improve stability an emulsion type mixed fluid with water and oil is often used. It is pumped over the cutting site of cutting machines as a state of atomized water droplet coated with oil by using jet. In this paper, to develop cutting fluid supplying nozzle to obtain ultra thin oil film for coating water droplet, a numerical analysis of three dimensional mixed fluid Jet through multi-stage nozzle was carried out by using a finite volume method. Jet flow characteristics such as nozzle exit velocity, development of mixing region, re-entrance and jet intensity were analyzed. Detailed mixing process of fluids such as air, water and oil in the nozzle were also investigated. It is easy to understand complex flow pattern in multi-stage nozzle. Important flow Information for advance design of cutting fluid supplying nozzle was drawn.

• 한국기계가공학회지
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• 제7권2호
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• pp.31-37
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• 2008

In this paper, we analyzed the dynamic behavior of magnetic fluid in a circular pipe with multiple permanent magnets. Magnetic fluid react on magnetic field against the normal fluid. In other words, magnetic fluid flow has the electromagnetism and fluid mechanics. So magnetic fluids has studied about the fluids properties and experiment. In this paper we studied the magnetic fluids velocity and pressure distribution for the novel type actuator. Because the velocity and pressure distribution is the important element of the magnetic fluids flow. First, we analyzed the Maxwell equation for the multiple permanent magnet and then concluded the governing equations for the magnetic fluid flow using the equation of Navier-Stokes. And, we simulated the dynamic behavior of magnetic fluid flow using the FEM(Finite Element Method). And we illustrated the relation between magnetic field and dynamic behavior of magnetic fluid flow.

• Geomechanics and Engineering
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• 제33권5호
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• pp.519-528
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• 2023

In this paper, we present the results of an experimental study on the effect of polymer support fluid on shaft resistance of offshore bored piles. A series of pullout tests were performed on bored piles installed under various boundary conditions considering different types of grounds and support fluids, and a range of support fluid exposure times. Contrary to previous studies concerning onshore bored piles, a time dependent effect of polymer fluid on shaft resistance was observed in all ground types. The adverse effect of polymer support fluid on the shaft resistance, however, was considerably less than bentonite support fluid for a given exposure time. No significant reduction in shaft resistance was evident when limiting the exposure time of the polymer support fluid to the side wall of the borehole within 2-3 hours. The degree to which the polymer fluid affects shaft resistance seemed to vary with the ground type. A proper consideration should be given to the time dependent effect of polymer fluid on shaft resistance of bored piles installed in offshore construction environment to limit its adverse effect on the pile performance. The practical implications of the findings are discussed.

• Journal of Nutrition and Health
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• 제56권4호
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• pp.377-390
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• 2023

본 연구는 한국인을 대상으로 제2형 당뇨병 환자와 질병이 없는 정상대조군을 비교하여 성별에 따른 체액 불균형 정도와 영양소 섭취량을 평가하고자 하였다. 조사대상자는 총 57명으로, T2DM이 있는 T2DM군 (n = 36)과 T2DM이 없는 정상대조군 (n = 21)으로 나누어 분석하고, 성별에 따른 체액량의 차이를 고려하여 남성 T2DM군 (n = 24), 남성 정상대조군 (n = 9), 여성 T2DM군 (n = 12), 여성 정상대조군 (n = 12)으로 세분화하여 지표들의 특징을 분석하였다. BIA를 통하여 연구대상자의 체액 조성을 분석한 결과, ECW/ICW는 T2DM군이 정상대조군보다 유의적으로 높았고, 부종지수를 나타내는 ECW/TBW는 T2DM군이 정상대조군보다 유의적으로 높게 나타났다. 성별에 따른 체액 조성을 분석한 결과, 남성과 여성 모두 T2DM군은 정상대조군보다 높은 ECW/ICW, ECW/TBW를 보이며 동일한 체수분율 양상이 나타났다. 식사일기를 통해 연구대상자의 영양소 섭취량을 분석한 결과, 1,000 kcal 당 탄수화물, 식이섬유, 비타민 A, 비타민 C, 나트륨, 칼륨 섭취량은 T2DM군이 정상대조군보다 많았고, 1,000 kcal 당 지방, 콜레스테롤 섭취량은 T2DM군이 정상대조군보다 적었다. 본 연구를 통해 T2DM 환자에게서 체액 불균형이 나타날 가능성이 높음을 알 수 있었으며 추후 당뇨 합병증의 평가, 진단의 기초 자료로 널리 활용될 것으로 사료된다.