• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1463-1471
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• 2017

In order to monitor the pipe thinning caused by flow-accelerated corrosion (FAC) that occurs in coolant piping systems, a shear horizontal ultrasonic pitch-catch waveguide technique was developed for accurate pipe wall thickness monitoring. A clamping device for dry coupling contact between the end of the waveguide and pipe surface was designed and fabricated. A computer program for multi-channel on-line monitoring of the pipe thickness at high temperature was also developed. Both a four-channel buffer rod pulse-echo type and a shear horizontal ultrasonic waveguide type for high-temperature thickness monitoring system were successfully installed to the test section of the FAC proof test facility. The overall measurement error can be estimated as ${\pm}10{\mu}m$ during a cycle from room temperature to $200^{\circ}C$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.337-342
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• 2001

A numerical study of three-dimensional fluid flow and heat transfer in the metering section of a single screw extruder has been performed. The mathematical model for the screw channel is simplified by unwound channel and fixing the coordinate system to the screw. The pressure boundary and the prescribed mass flow rate conditions are imposed on the inlet and outlet, respectively. The commercial code STAR-CD based on the finite volume method is used to obtain the results of the present work. The computation of the reverse flow, which cannot be computed by the marching-type 3-D model, is performed in the present study.

• 물과 미래
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• 제18권4호
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• pp.361-367
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• 1985

수리구조물에 의하여 하천단면의 감소로 유발되는 수면의 변화를 수치적으로 해석하였다. 수면변화는 수축화와 등류의 Froude No.에 가장 민감하게 나타났으며, 수면의 변화로부터 구한 배수는 Skogerboe의 실험식과 매우 잘 맞았다. 이는 배수의 크기는 수치해석법으로 예측할 수 있음을 시사한다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.292-297
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• 2001

Twin screw extruders are the heart of the polymer processing industry. They are used at some stage in nearly all polymer processing operations. This paper is concerned with the basic elements of the extruder design. The proper design of the geometry of the extruder screw is of crucial importance to the proper functioning of the extruder. If the material transport instabilities occur as a result of improper screw geometry, even the most sophisticated computerized control system cannot solve the problem. For this purpose, a characteristic design on flights shape of the extruder screw. This paper presents cross section designs of a closely intermeshing twin screw extruder with double-flighted screw elements, and channel depth characteristics for a double flighted corotating self-wiping twin screw extruder.

• JSTS:Journal of Semiconductor Technology and Science
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• 제2권4호
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• pp.253-258
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• 2002

This paper reports the design, modeling, fabrication and measurement of passive microvalves, which are applicable to glaucoma implants. The proposed microvalves were designed using fluidic theory. The microvalves consisted of microchannels and chambers. The microchannels had a constant fluidic resistance generating a pressure difference. Six kinds of microvalves were designed using fluidic equations for laminar flow and fabricated to examine the influences of chamber size, channel length and the shape of channel cross section. The pressure difference between the designed microvalve and the fabricated microvalve was measured to be less than 4%.

• 한국전산유체공학회지
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• 제11권4호
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• pp.101-106
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• 2006

In the microfluidic devices the most important thing is mixing efficiency ol various fluids. In this study a newly designed miler is proposed to enhance the mixing effect with the purpose to apply it to microchannel mixing in a short future. This design is composed of a channel with cross baffles periodically arranged on the both bottom and top surfaces ol the channel. To obtain the yow patterns, the numerical computation was performed by using a commercial code, ANSYS CFX 10.0. To evaluate the mixing performance, we computed Lyapunov exponent and obtained Poincare sections. it was shown that our design provides the excellent mixing effect.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.159-162
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• 2006

In the microfluidics devices the most important thing is mixing efficiency of various fluids. In this study a newly designed mixer is proposed to enhance the mixing effect with the purpose to apply it to microchannel mixing in a short future. This design is composed of a channel with cross baffles periodically arranged on the both bottom and top surfaces of the channel. To obtain the flow patterns, the numerical computation was performed by using a commercial code, ANSYS CFX 10.0. To evaluate the mixing performance, we computed Lyapunov exponent and obtained Poincare sections.

• 대한기계학회논문집B
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• 제29권6호
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• pp.747-754
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• 2005

Because the liquid-vapor interfacial shear stress affects seriously the liquid flow and the maximum heat transport rate of the grooved wick heat pipe, an accurate modeling for the pressure drop characteristics of the liquid flow is required. A novel method for calculating the liquid pressure drop and the velocity profile of an open channel flow in a microchannel with an arbitrary cross-section is suggested and validated by experiments. An experimental apparatus for the Poiseuille number of the liquid flow in open rectangular microchannels with the hydraulic diameters of 0.40mm, 0.43mm, 0.48mm is used in order to reproduce real situations in the grooved wick heat pipe. Analytic results from the suggested method are compared with the experimental data and they are in a close agreement with each other.

• ETRI Journal
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• 제17권4호
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• pp.1-12
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• 1996

A novel body-tied silicon-on-insulator(SOI) n-channel metal-oxide-semiconductor field-effect transistor with grounded body electrode named GBSOI nMOSFET has been developed by wafer bonding and etch-back technology. It has no floating body effect such as kink phenomena on the drain current curves, single-transistor latch and drain current overshoot inherent in a normal SOI device with floating body. We have characterized the interface trap density, kink phenomena on the drain current ($I_{DS}-V_{DS}$) curves, substrate resistance effect on the $I_{DS}-V_{DS}$ curves, subthreshold current characteristics and single transistor latch of these transistors. We have confirmed that the GBSOI structure is suitable for high-speed and low-voltage VLSI circuits.

• Korean Journal of Hydrosciences
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• 제8권
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• pp.41-56
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• 1997

A new routing computer model for the symmetric compound channel called the ASRMCS(Apparent Shear Force Muskingum-Cunge Method in Symmetry) has been developed. The Muskingum-Cunge routing method is adapted. The Apparent Shear Force (ASF) between the deep main channel and the shallow floodplan flow is introduced while the flow is routed. The nonlinear parameter method is applied. The temporal and spatial increments are varied according to the flow rate. The adaptation of above schemes is tested against the routed hydrographs using the DAMBRK model. The results of general routing practice of Muskingum-Cunge Method(GPMC) are also compared with those of above two models. The results of the new model match remarkably well with those of DAMBRK. The routed hydrographs show a smooth variation from the inflow boundary condition without any distortions caused by the difference of cross-section shape. However, the results of GPMC, showing early rise and fall of routed hydrograph, have considerable differences from those of the ASFMCS and DAMBRK.