• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.22-27
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• 2006

This paper describes the development of the stream-tube based dispersion model for modeling contaminant transport in open channels. The operator-splitting technique is employed to separate the 2D contaminant transport equation into the pure advection and pure dispersion equations. Then the total variation diminishing (TVD) schemes are combined with the second-order Lax-Wendroff and third-order QUICKEST explicit finite difference schemes respectively to solve the pure advection equation in order to prevent the occurrence of numerical oscillations. Due to various limiters owning different features, the numerical tests for 1D pure advection and 2D dispersion are conducted to evaluate the performance of different TVD schemes firstly, then the TVD schemes are applied to experimental data for simulating the 2D mixing in a straight trapezoidal channel to test the model capability. Both the numerical tests and model application show that the TVD schemes are very competent for solving the advection-dominated transport problems.

• 한국항해학회지
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• 제15권1호
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• pp.1-9
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• 1991

The coaxial sample holder with 20mm in diameter and the adaptor from type N connector-to-20mm${\phi}$ coaxial tube are designed and manufactured which have been used for designing and measuring the fabricated microwave absorber. In addition, the measure in method of material constants of the microwave absorbers is described, which is focused on minimizing the error due to the sample's shapes, the fitting conditions, etc. After describing the design method of a single-layed microwave absorber, the microwave absorbers for X-band, C-band and S-band RADARs are designed and fabricated, respectively, which are composed of ferrite, carborn, and binder and have good performance. Futhermore, we develop the high performance microwave absorber in extremely wide-band type for RADAR, which is composed of different material and its mixing ratio and which could cover nearly from 4 to 10 GHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.503-506
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• 2002

BSCCO 2212 HTS was fabricated by CFP(centrifugal forming process). The powder was initially ground in the mixing ratio of 2:2::1:2 with 10% of SrSO$_4$. The temperature increased up to 1035$^{\circ}C$ and 1200$^{\circ}C$ for melting. The melt was poured into the preheated and rotating copper mould from 200 to 600$^{\circ}C$. The specimen was not broken by thermal impact when the melting temperature was over 1050$^{\circ}C$ and copper mould was preheated over 400$^{\circ}C$ for 30min. A tube type of specimen was annealed at 840$^{\circ}C$ or 860$^{\circ}C$ in oxygen atmosphere for 24hours. Typical microstructure was analyzed in terms of CFP parameters by XRD, SEM, and EDS and also superconducting characteristics were compared.

• International Journal of Fluid Machinery and Systems
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• 제6권1호
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• pp.1-10
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• 2013

Jet pump is one type of artificial lifts and is used when depth and deviation of producing wells increases and pressure depletion occurs. In the present study, numerical analysis has been carried out to analyze the flow behavior and find the performance of the jet pump. Reynolds-averaged Navier Stokes equations were solved and k-${\varepsilon}$ turbulence model was used for simulations. Water and light oil as primary fluids were used to pump water, light oil and heavy oil. The ratios of area and length to diameter of the mixing tube were considered as design parameters. The pump efficiency was considered to maximize for the downhole conditions. It was found that the increase in viscosity and density of the secondary fluid reduced efficiency of the system. Water as primary fluid produced better efficiency than the light oil. It was also found that the longer throat length increased efficiency upto 40% if light oil was used as primary fluid and secondary fluid viscosity was 350 cSt.

• 대한기계학회논문집
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• 제8권2호
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• pp.133-140
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• 1984

본 연구에서는 이러한 2유체방정식모델을 Stokes의 저항력 뿐만 아니라 벽면 의 영향을 함께 노고하여 벤츄리관에서의 정압강하가 공기류량과 고체유량, 그리고 입 자의 크기에 어떻게 의존하는가를 해석하였다. 본 연구의 수치해석결과를 Farbar와 Lee와 Crowe의 실험과 비교하였으며, 만족할 만한 일치를 얻었다.

• Nuclear Engineering and Technology
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• 제44권8호
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• pp.831-846
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• 2012

KAERI has developed a two-phase CFD code, CUPID, for a refined calculation of transient two-phase flows related to nuclear reactor thermal hydraulics, and its numerical models have been verified in previous studies. In this paper, the CUPID code is validated against experiments on the downcomer boiling and moderator flow in a Calandria vessel. Physical models relevant to the validation are discussed. Thereafter, multi-scale thermal hydraulic analyses using the CUPID code are introduced. At first, a component-scale calculation for the passive condensate cooling tank (PCCT) of the PASCAL experiment is linked to the CFD-scale calculation for local boiling heat transfer outside the heat exchanger tube. Next, the Rossendorf coolant mixing (ROCOM) test is analyzed by using the CUPID code, which is implicitly coupled with a system-scale code, MARS.

• 한국유체기계학회 논문집
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• 제8권6호
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• pp.33-39
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• 2005

A thermal vapor compressor in which the subsonic/supersonic flow appears simultaneously, has been accurately designed through the CFD analysis for the various shape parameters such as the primary nozzle shape, converging duct shape, mixing tube diameter, and so on. The performance of the developed thermal vapor compressor has been experimentally verified to be installed in a Multi Effect Desalination(MED) plant as an important element. In this paper, the effects of each parameter are discussed on the basis of CFD results and the experimental results for various boundary conditions(motive pressure, suction pressure, and discharge pressure) are presented in compared with CFD results. The two results show a good agreement with each other within 2 % accuracy with regard to the entrainment ratio.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.648-649
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• 2006

The dry-milling technique was used for mixing and crushing oxides and graphite powders. The ratio of ball-to-powder was 30:1 and argon gas was filled in jar. The excess carbon was $10{\sim}20wt%$ of the stoichiometric amount. The dry-milling was carried for 20 hours. The mixed powders were reduced and carburized at $900{\sim}980^{\circ}C$ for 3 hours flowing Ar gas in tube furnace. The dry-milled powders showed the wide diffraction patterns of X-ray. The reactions of reduction and carburization were completed in 3 hours at $980^{\circ}C$. After the reactions, the mean size of WC particles was about 200 nm. The content of free carbon in WC/Co mixed powders was less as the reaction temperature increased.

• Restorative Dentistry and Endodontics
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• 제4권1호
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• pp.29-34
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• 1978

The purpose of this study was to measure penetration of dye stuff(5% Methylene blue, Hematoxylin, Crystal violet and Safranin-O) on silicate cement, Adaptic, Hi-pol and unfilled resin. Each filling material was mixed on the mixing pad and the mixed material was inserted with condensation force of 500gr, 1000gr and 2000gr and without condensation force into preformed glass tube (10mm in diameter and 10mm in height). The specimen was stored in the air for 24 hours, then specimen was immersed in various dye solution (5% methylene blue, hematoxin, crystal violet and safranin-O) for different period of time (l hour and 24 hours). These dye-treated specimen was cut horizontally at the middle portion and the dye penetration in cut surface was measured. Following results were obtained. 1. Pentration of various dye was excessive in silicate cement with and without Condensation force. 2. There has been no evidence of dye penetration in unfilled resin. 3. Dye penetration occurced with in 1 hour period and the extending time didn't affect the dye penetration.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.50-52
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• 2005

In this paper, the analysis of the eddy current testing(ECT) signals under thc Influence of the ferromagnetic support plate was performed in steam generator(SG) tube of nuclear power plant. In order to remove the influence of the ferromagnetic support plate, a multi-frequency ECT was used. The models which was established for the analysis of the signals is calculated using numerical analysis of finite element method. Through the result of numerical analysis, improved signals is acquired considering the influence of the ferromagnetic support plate using mixing of multi-frequency This paper is presented the residual errors and the phase changes for analysis of the defect signals which should be considered when conducting a ECT using multi-frequency.