• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.3
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• pp.176-185
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• 2009

A general flow distribution model and a simple process of numerical analysis, which can be applied to multi-pass systems with manifolds, are presented. A numerical procedure, namely a modified equal pressure method based on the discrete model, was developed to predict flow rates at branch tubes. The predicted pressure distribution agreed well with the previous research with the average error less than 11%. A parametric study was performed to demonstrate the effect on the flow distribution.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2280-2285
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• 2008

A general flow distribution model and a simple process of numerical analysis, which can be applied to multi-pass systems with manifolds, are presented. Correlations are derived from the discrete model, and numerically calculated using a modified equal pressure method. The predicted pressure distribution agrees well with the available experimental results of other researchers with the average error less than 2% for 10 branch manifolds, and 4% for 20 branch manifolds. A parametric study is performed to demonstrate the effect on the flow distribution.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.10
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• pp.2667-2677
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• 1995

A new numerical algorithm using equal order linear finite element and fractional step method has been developed which is capable of analyzing unsteady fluid flow and heat transfer problems. Streamline Upwind Petrov-Galerkin (SUPG) method is used for the weighted residual formulation of the Navier-Stokes equations. It is shown that fractional step method, in which pressure term is splitted from the momentum equation, reduces computer memory and computing time. In addition, since pressure equation is derived without any approximation procedure unlike in the previously developed SIMPLE algorithm based FEM codes, the present numerical algorithm gives more accurate results than them. The present algorithm has been applied preferentially to the well known bench mark problems associated with steady flow and heat transfer, and proves to be more efficient and accurate.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.4
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• pp.435-443
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• 2009

Optimal duct design of a HVAC system requires analysis technology to accurately evaluate its pressure losses, flow rate and velocity for making a compromised design among fan capacity and duct size affecting initial manufacturing and operation costs, and noise induced by the HVAC system. In this paper, we carry out initial duct design using the equal friction method. Using the result, the T-method is applied for accurate analysis of flow rate. Then, the duct size is modified using the difference between the required and the calculated flow rate, which can guarantee required flow rate, reduce the pressure unbalance among duct paths and lead to select optimal fan performance. To verify the validity and effectiveness of the proposed design method, an example for HVAC system design including noise analysis is demonstrated.

• Korean Journal of Metals and Materials
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• v.46 no.3
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• pp.144-149
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• 2008

Equal channel angular pressing (ECAP) has been studied intensively over the decade as a typical top-down process to produce ultrafine/nano structured materials. ECAP has successfully been applied for a processing method of severe plastic deformation to achieve grain refinement of magnesium and to enhance its low ductility. However, difficult-to-work materials such as magnesium and titanium alloys were susceptible to shear localization during ECAP, leading to surface cracking. The front pressure, developed by Australian researchers, can impose hydrostatic pressure and increase the strain level in the material, preventing the surface defect on workpiece. In the present study, we investigated the deformation and fracture behavior of pure magnesium using experimental and numerical methods. The finite element method with different ductile fracture models was employed to simulate plastic deformation and fracture behavior of the workpiece.

• Ocean Systems Engineering
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• v.13 no.1
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• pp.57-77
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• 2023

In the present study, the total hydrodynamic pressure exerted by the fluid on walls of rectangular tanks due to horizontal excitations of different frequencies, is investigated by pressure based finite element method. Fluid within the tanks is invisid, compressible and its motion is considered to be irrotational and it is simulated by two dimensional eight-node isoparametric. The walls of the tanks are assumed to be rigid. The total hydrodynamic pressure increases with the increase of exciting frequency and has maximum value when the exciting frequency is equal to the fundamental frequency. However, the hydrodynamic pressure has decreasing trend for the frequency greater than the fundamental frequency. Hydrodynamic pressure at the free surface is independent to the height of fluid. However, the pressure at base and mid height of vertical wall depends on height of fluid. At these two locations, the hydrodynamic pressure decreases with the increase of fluid depth. The depth of undisturbed fluid near the base increases with the increase of depth of fluid when it is excited with fundamental frequency of fluid. The sloshing of fluid with in the tank increases with the increase of exciting frequency and has maximum value when the exciting frequency is equal to the fundamental frequency of liquid. However, this vertical displacement is quite less when the exciting frequency is greater than the fundamental frequency.

• Journal of the Korean Society of Industry Convergence
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• v.16 no.2
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• pp.29-33
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• 2013

This study has been conducted to propose an optimal design guidance of underfloor air distribution system by examining air pattern and proper exhaust status of floor plenum using CFD (Computational Fluid Dynamics). Simulation shows deficient air pattern and exhaust status at BPG (Bypass Grille) of the current design. As a means to find an alternative design, four cases have been developed and tested. Case 1, 2 and 3 show similar results in comparison to the current design. However, case 4 shows improved air pattern and exhaust status at BPG(Bypass Grille), and has been chosen as the optimal alternative.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.804-807
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• 1997

Recently equal-channel angular pressing (ECAP) has been employed to produce ultra-fine grain size materials. In this paper pure-Zirconium is considered due to its applicability to nuclear reactors. Among many process parameters of ECAP frictional effect on the plastic deformation of die has been investigated. The back pressure effect due to friction increases the stress level of die especially at the crossing area of channels, which may result in plastic deformation of die. The finite element method has been employed to investigate this issue.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.8
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• pp.504-509
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• 2005

This paper presents a new method for obtaining the noninvasive and unrestrained blood pressure readings noninvasively and unrestrainedly using based on reflected wave arrival time(RAT) in the volume of pulse. Since this new method employs only volume pulse, is more rapider and simpler than the method using pulse transit time(PTT) because it only employs the volume of pulse. Blood pressure, PTT and RAT were acquired from 15 healthy subjects. Each subjects were performed forty trials of each measurement. As a result of those trials, the mean error between oscillometric and RAT measurements for systolic blood pressure was $4.55\pm5.64mmHg$. This result showed quite equal with the mean error between oscillometric and PPT measurf:ments, $4.22\pm5.30mmHg$, However, it was not obtained a satisfactory result in the relativity of oscillometric to both RAT and PPT measurements for diastolic blood pressure because of personal difference. To conclude, the method of systolic blood pressure estimation noninvasively and unrestrainedly using by RAT may be used as the method by PTT. Nevertheless, additional studies would be necessary for the RAT/PTT estimation of diastolic blood Pressure measurement.

• Journal of the Korean Society of Costume
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• v.52 no.8
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• pp.15-27
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• 2002

To set the measurements of bras for women in their 20s, considering the comfortableness in wearing and tightness, this paper conducted a questionnaire survey concerning breasts and bras as well as measurements of body and contact surface pressure. Easier and more accurate method of determining cup sizes based on the breast circumference is recommended to make up for the problem of current bra size system that can falsely measure cup sizes. Lower chest circumference was set at 5 cm equal intervals, and the breast circumference applicable to the cup size was set starting from the standard, 18 cm (A-cup), at 2 cm equal intervals, which gave the best coverage (88.1%).