• Nuclear Engineering and Technology
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• 제38권5호
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• pp.433-436
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• 2006

The implementation of multiplexing techniques combined with advances in neutron optics make the neutron three-axis spectrometers (TAS) an efficient tool to map inelastic response from single crystals over momentum transfer ranges comparable to the size of a single Brillouin zone. Thanks to recent progress in polarization techniques such experiments can be combined relatively easily with neutron polarization analysis, which does not only provide unambiguous separation of response corresponding to structural and magnetic degrees of freedom, but permits a quantitative analysis of the magnetic response anisotropy, often of crucial importance to test theoretical predictions. In the forthcoming decade we therefore expect a further development of the complementary use, rather than competition, of the reactor-based TAS's with time-of-flight (TOF) instruments for single crystal spectroscopy at the existing (ISIS) as well as at the newly built (SNS, J-PARK) pulsed sources.

• Journal of Advanced Marine Engineering and Technology
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• 제31권7호
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• pp.833-841
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• 2007

The aim of this paper is to analyze the conjugate problems of heat conduction in solid walls coupled with laminar free convection flow adjacent to a vertical flat plate under boundary layer approximation. Using the similarity transformations the governing boundary layer equations for momentum and energy are reduced to a system of partial differential equations and then solved numerically using Finite Difference Method(FDM) known as the Keller-box scheme. Computed solutions to the governing equations are obtained for a wide range of non-dimensional parameters that are present in this problem, namely the coupling parameter P. the Prandtl number Pr and the heat generation parameter Q. The variations of the local heat transfer rate as well as the interface temperature and the friction along the plate and typical velocity and temperature profiles in the boundary layer are shown graphically. Numerical solutions have been consider for the Prandtl number Pr=0.70

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1996년도 제7회 학술강연회논문집
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• pp.27-41
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• 1996

In this study the heat transfer and fluid flow of the molten pool in stationary gas tungsten arc welding using argon shielding gas were investigated. Transporting phenomena from the welding arc to the base material surface, such as current density, heat flux, arc pressure and shear stress acting on the weld pool surface, were taken from the simulation results of the corresponding welding arc. Various driving forces for the weld pool convection were considered, self-induced electromagnetic, surface tension, buoyancy, and impinging plasma arc forces. Furthermore, the effect of surface depression due to the arc pressure acting on the molten pool surface was considered. Because fusion boundary has a curved and unknown shape during welding, a boundary-fitted coordinate system was adopted to precisely describe the boundary for the momentum equation. The numerical model was applied to AISI 304 stainless steel and compared with the experimental results.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.685-689
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• 2004

Numerical simulation is conducted to clarify the heat transfer and fluid flow characteristics of HVAC(Heating, Ventilating and Air-Conditioning) for double' deck train. The HVAC system is installed under the roof of carbody. In the lay-out of HVAC system, air duct must be installed to supply air to 1st and 2nd floor respectively. The standard k-$\epsilon$ and LES models for turbulence and SIMPLE algorithm for pressure equation hased on finite volume method are used to solve the physic a] HVAC model. To assure convergence, QUICK scheme for momentum equation and the 2nd order upwind scheme for turbulent equations arc used. From the results of simulation, the temperature and velocity magnitude are also distributed uniformly in the interior of double-deck passenger car.

• 전자공학회논문지D
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• 제35D권5호
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• pp.54-62
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• 1998

In a plasma etching system, ions become an important parameter in determining the wafer topography which depends on both the physical sputtering mechanism and the chemically enhanced reaction. this paper reports the energy and angular distributions of ions across the plasma sheath using a monte carlo method. The ion distribution is mainly affected by the magnitude of the sheath voltage and by the collision in the sheath. Furthemore, the local potential distribution in a plamsa sheath has been determined by solving the poisson's equation. In th is work, ionic collisions were cosidered in terms of both charge exchange and momentum transfer. The three-dimensional distributions of ions were calculated with varying the input process conditions in the plasma reactor.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.839-843
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• 2001

For robotic endoscope, some researchers suggest pneumatic actuators based on inchworm motion. But, the existing endoscopes are not seemed to be replaced completely because human intestine is very sensitive and susceptible to damage. We design and test a new locomotion of robotic endoscope able to maneuver safely in the human intestine. The actuating mechanism is composed of two solenoids at each side and a single permanent magnet. When the current direction is reversed, repulsive force and attractive at the opposition side propels permanent magnet. Impact force against robotic endoscope transfer momentum from moving magnet to endoscope capsule. The direction and moving speed of the actuator can be controlled by adjusting impact force. Modeling and simulation experiments are carried out to predict the performance of the actuator. Simulation experiments show that force profile of permanent magnet is the dominant factor for the characteristic of the actuator. The results of simulations are verified by comparing with the experimental results.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.40-42
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• 2002

Electromigration is atomic diffusion driven by a momentum transfer from conducting electrons. With every new generation of intergrated circuits, interconnect line widths have been reduced and current densities in the interconnect have become higher. This leads to an increase in the threat to interconnect reliability due to electromigration. In this paper, we simulated stress evolution with changing temperature, duty factor(ratio of on time and pulse time), frequency under pulsed DC condition. As a result, we predict MTF(median time to failure) and found that exponent n is affected by changing temperature, duty factor.

• E2M - 전기 전자와 첨단 소재
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• 제6권1호
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• pp.63-68
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• 1993

CO$_{2}$기체의 운동량변환, 진동여기, 전자여기 및 전리충돌 단면적의 결정은 온도 293[.deg.K], 상대전계의 세기 E/N은 1.0[Td].leq.E/N.leq.200[Td]의 범위에서 볼츠만 방정식을 Backward-Prolongation 방법으로 해석하여 전자 이동속도의 계산값을 산출하고 이것을 M. T. Elford에 의해 실험적으로 측정된 이동속도의 값과 비교하였다. 본 연구에서 운동량변환충돌단면적은 Hake & Phelps의 값을 기초로 하였으며 온도 293[.deg.K], 상대전계의 세기 E/N은 3.0[Td].leq.E/N.leq.50[Td]인 범위 전자에너지분포함수 및 전자특성에너지는 상대전계의 세기 E/N이 1.0[Td].leq.E/N.leq.200[Td]인 범위에서 산출하였다.

• 한국전산유체공학회지
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• 제15권3호
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• pp.87-94
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• 2010

Hydromagnetic flow in a cavity under a uniform magnetic field is studied numerically. The cavity is comprised of four radiatively active surfaces. Due to large temperature difference inside a cavity, the radiative interaction between walls is taken into account. The coupled momentum and energy equations are solved by SIMPLER algorithm while the radiant heat exchanges are obtained by the finite volume method for radiation. A Wide range of Grashof numbers is examined as a controlling parameter. Resultant flow and heat transfer characteristics are investigated as well.

• 대한기계학회논문집B
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• 제23권10호
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• pp.1274-1284
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• 1999

The Regulatory Guide 1.82 recommends an analysis of hydraulic performance for sump of ECCS (Emergency Core Cooing System) when LOCA(Loss of Coolant Accident) occurs in a nuclear power plant. The present study deals with 3-dimensional, unsteady, turbulent and two-phase flow simulation to examine the behavior of mixture of reactor coolant and debris near the floor of containment building in conjunction with appropriate assumptions. The dispersed solid model has been adjusted to the interfacial momentum transfer between reactor coolant and debris. According to the results, the counterclockwiserecirculation zone had been formed in the region between sump and connection aisle about 376 second after LOCA occurs. The debris thickness accumulated on a sump screen periodically increases or decreases up to 2000 second, afterwards its peak decreases.