• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.7
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• pp.1210-1218
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• 2001

In this paper, A X-band voltage-controlled hair-pin resonator oscillator(VCHRO) is able to a local oscillator or a signal source in transmitter/receiver of a microwave communication system for mobile radar, is designed and fabricated In order to apply mobile radar system is used the hair-pin resonator stronger on shock or vibration than the dielectric resonator, and also, in order to improvement the phase noise and output power is used a system of serial feedback format A hair-pin resonator was simulated by momentum method of HP ADS and then a oscillator circuit was designed that operates at 10.525 GHz by nonlinear method in harmonic balance simulation. The HRO generated output power of 6.93 dBm at 10.525 GHz, phase noise of -57.74 dBc at 100 kHz offset from carrier and the 2'nd harmonic was suppressed -23.90 dBc.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.123-135
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• 1995

A numerical procedure is described for predicting steady drift forces an multiple three-dimensional bodies of arbitrary shape freely floating in waves. The developed numerical approach is based on combination of a three-dimensional source distribution method, wave interaction theory art the far-field method using momentum theory. Numerical results are compared with the experimental or numerical ones, which are obtained in the literature, of steady drift forces on 33(3 by 11) floating composite vertical cylinders in waves. The results of comparison confirmed the validity of the proposed approach. Finally, the interaction effects are examined in the case of an array of 40(4 by 10) freely floating rectangular bodies in shallow water.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.11a
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• pp.43-48
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• 1997

The smoke filling process for the atrium space containing a fire source is simulated using two types of deterministic fire modus: Zone model and Field model. The zone mode used is the CFAST(version 1.6) mode developed at the Building and Fire Research laboratories, NIST in the USA. The lied model is a self-developed fire field model based on Computational Fluid Dynamics(CFD) theories. This article is focused on finding out the smoke movement and temperature distribution in atrium space which is cubic in shape. A computational procedure for predicting velocity and temperature distribution in fro-induced flow is based on the solution, in finite volume method and non-staggered grid system, of 3-dimensional equations for the conservation of mass, momentum, energy, species and so forth. The fire model i. e. Zone model and Field model predicted similar results for Ire clear height and the smoke layer temperature.

• The KIPS Transactions:PartA
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• v.18A no.4
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• pp.123-128
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• 2011

As the global grid has grown in size, large-scale distributed data analysis schemes have gained momentum. Over the last few years, a number of methods have been introduced for allocating data intensive tasks across distributed and heterogeneous computing platforms. However, these approaches have a limited potential for scaling up computing nodes so that they can serve more tasks simultaneously. This paper tackles the scalability and communication delay for computing nodes. We propose a distributed data node for storing and allocating the data. This paper also provides data provisioning method based on the steady states for minimizing the communication delay between the data source and the computing nodes. The experimental results show that scalability and communication delay can be achieved in our system.

• Fire Science and Engineering
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• v.11 no.4
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• pp.3-14
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• 1997

The smoke filling process for the atrium space containing a fire source is simulated using two types of deterministic fire model : Zone model and Field model. The zone model used is the CFAST(version 1.6) model developed at the Building and Fire Research Laboratories, NIST in the USA. The field model is a self-developed frie field model based on Computational Fluid Dynamic (CFD) theories. This article is focused on finding out the smoke movement and temperature distribution in atrium space which is cubic in shape. For solving the liked set of velocity and pressure equation, the PISO algorithm, which strengthened the velocity-pressure coupling, was used. Since PISO algorithm is a time-marching procedure, computing time si very fast. A computational procedure for predicting velocity and temperature distribution in fire-induced flow is based on the solution, in finite volume method and non-staggered grid system, of 3-dimensional equations for the conservation of mass, momentum, energy, species and so forth. The fire model i.e Zone model and Field model predicted similar results for clear heights and the smoke layer temperature.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.2
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• pp.93-101
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• 1986

The behavior of a plane buoyant jet discharged vertically upward into a stagnant uniform environment is analyzed by continuity, momentum transport equation by numerical scheme. The governing equations are solved by finite difference method employing stream function and vorticity transport and Prandtl's turbulent model. Results for centerline velocities and temperatures, temperature distribution and flow pattern in receiving environment due to buoyant jet in the range of discharge densimetric Froude number of 4 to 32 show good agreement with published data. Spreading rate and dispersion ratio, which are required in integral type analysis of whole range of buoyant jet and have not been obtained yet, are derived in terms of discharge densimetric Froude number and vertical distance from source.

• Aerospace Engineering and Technology
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• v.7 no.1
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• pp.136-141
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• 2008

Cylindrical supersonic exhaust diffuser, which utilizes the momentum of high temperature gas exhausted from nozzle, provides simple methods for obtaining stable and low pressure around the propulsion system. Hot zone on which exhausted gas from nozzle exit impinges directly should be cooled to avoid melting of diffuser. This paper describes method and result of subscale high altitude simulation test with water cooling. Subscale gas generator with solid propellant was used for hot gas source and tap water for coolant.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.761-772
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• 2008

The object of this study is to develop the model that solves the numerically difficult problems in hydraulic engineering and to demonstrate the applicability of this model by means of various test examples, such as, verification in the gradually varied unsteady condition, three steady flow problems with the change of bottom slope with exact solution, and frictional bed with analytical solution. The governing equation of this model is the integral form of the Saint-Venant equation satisfying the conservation laws, and finite volume method with the Riemann solver is used. The evaluation of the mass and momentum flux with the HLL Riemann approximate solver is executed. MUSCL-Hancock scheme is used to achieve the second order accuracy in space and time. This study introduce the new and simple technique to discretize the source terms of gravity and hydrostatic pressure force due to longitudinal width variation for the balance of quantity between nonlinear flux and source terms. The results show that the developed model's implementation is accurate, robust and highly stable in various flow conditions with source terms, and this model is reliable for one-dimensional applications in hydraulic engineering.

• Journal of Power System Engineering
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• v.9 no.2
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• pp.81-87
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• 2005

This study is numerical analysis on the increasing temperature characteristics of vaporizer fin for liquefied natural gas with super low temperature. Existing LNG vaporizers use the direct contact heat transfer mode where the extreme super low temperature LNG of $-162^{\circ}C$ flows inside of the tubes and about $20^{\circ}C$air flows on outside of the fin. Recently, the vaporizers with great enhanced performance compared to conventional type have been developed to fulfill these requirements. The vaporizing characteristic of LNG vaporizer with air as heat source has a fixed iced. These characteristic cause a low efficiency in vaporizer, total plant cost and installing space can be increased. The vaporizing characteristics of LNG via heat exchanger with air are analytically studied for an air heating type vaporizer. This study is intended to supply the design data for the domestic fabrication of the thickness and angle vaporizer fin. Governing conservation equations for mass, momentum and energy are solved by STAR-CD based on an finite volume method and SIMPLE algorithm. Calculation parameter is fin thickness, setup angle and LNG temperature. If the vaporization performance of the early stage and late stage of operating is considered, the case of ${\phi}=90^{\circ}$ was very suitable. In this paper was estimated that the heat transfer was most promoted in case of THF=2mm.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1794-1801
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• 2008

Fire-driven flow and temperature distribution in a ventilated tunnel was analyzed by Large Eddy Simulation using FDS code. The simulated tunnel is 182m length, 5.4m wide and 2.4m height. A pool fire was located 112m from tunnel entrance and was taken as a heat source of $0.89m^2$. The heat is assumed to be released uniformly throughout the whole simulated time. The fire strength was 2.76MW and the fuel burnt was octane. The parallel computational method was employed to accelerate the computing time and manage the large grid points which is not possible to handle in the one CPU. The total grid points used were $2.4{\times}10^6$ and 7 CPUs were used to calculate the momentum and energy equations. The simulated results were well compared with the experiments.