• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.173-175
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• 2015

We simulate the particle bed motions with combustion and reduction in steel making rotary kilns. The particle bed motions are simulated by a Lagrangian approach called Discrete Phase Model (DPM). To reduce the number of tracking particles, the Coarse Grain Model (CGM) was applied. The model for particle motions showed good agreements with experimental results. In addition to the particle motion, the combustion and reduction simulation was performed. The combustion and reduction simulation can consider heat, mass and momentum transfer between the gas phase and particle beds.

• 대한기계학회논문집B
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• 제20권3호
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• pp.1096-1105
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• 1996

A theoretical model of the frost formation has been presented to investigate the characteristics of the growth of frost layer by considering molecular diffusion of water vapor and heat generation caused by sublimation of water vapor in the frost layer. The present model was compared with existing experimental data as well as a previous model. The difference between the present model and existing experimental data was found to be about 6 percent. An analysis for the behavior of frost formation using present model shows a good agreement with the trend for a number of experimentally observed features. The present analysis can also provide the physical understanding on the phenomena of the frost formation.

• 자원리싸이클링
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• 제27권4호
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• pp.65-69
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• 2018

용매추출에서 등온추출곡선은 수상과 유기상에서 평형관계에 있는 농도를 나타낸다. 등온추출곡선과 조업선을 동시에 나타낸 McCabe-Thiele도는 물질 전달공정에서 여러 유용한 정보를 제공한다. 추출반응식과 평형상수를 알고 있는 경우 등온추출곡선을 계산으로 구하는 방법을 소개하였다. 또한 분배계수가 일정한 경우 금속 추출에 필요한 추출단수를 추산할 수 있는 Kresmer식을 소개하였다.

• Earthquakes and Structures
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• 제2권4호
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• pp.323-336
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• 2011

The problem of reconstruction of complete building response from a limited number of response measurements is considered. The response at the intermediate degrees of freedom is reconstructed by using piecewise cubic Hermite polynomial interpolation in time domain. The piecewise cubic Hermite polynomial interpolation is preferred over the spline interpolation due to its trend preserving character. It has been shown that factorization of response data in variable separable form via singular value decomposition can be used to derive the complete set of normal modes of the structural system. The time domain principal components can be used to derive empirical transfer functions from which the natural frequencies of the structural system can be identified by peak-picking technique. A reduced-rank approximation for the system flexibility matrix can be readily constructed from the identified mass-orthonormal mode shapes and natural frequencies.

• 한국지반공학회논문집
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• 제15권6호
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• pp.143-154
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• 1999

본 연구에서는 암반 앵커의 텐던-그라우트 경계면의 하중전달기구(load transfer mechanism)를 규명하기 위하여 암질이 강한 자연 화강암과 콘크리트로 제작된 모형 암반에 시공된 모형 암반 앵커에 대한 정적 인발험(static uplift test)을 수행하였다. 불연속면이 텐던-그라우트의 전단응력 분포에 미치는 영향을 밝히기 위하여 수평한 절리면을 갖고 있는 모형암반도 제작되었다. 실험 결과 불연속면이 없는 암반에 시공된 암반 앵커의 경우 앵커 상단에 심한 응력 집중이 발생함을 알 수 있었고 불연속면이 증가할수록 깊이에 따라 균일한 전단응력 분포를 나타냈다. 또한, 실험결과에 대한 회귀분석을 통하여 텐던-그라우트 경계면의 전단응력 분포에 관한 경험식을 산정하였으며, 실험에 의한 전단응력 분포는 텐던 직경의 2~3배 깊이에서는 이론에 의한 전단응력 분포 보다 작게 나타나고 그 이하에서는 반대 현상을 관찰할 수 있었다.

• 한국유체기계학회 논문집
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• 제18권2호
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• pp.60-66
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• 2015

Conjugate heat transfer analysis was performed to investigate the flow and cooling performance of the high pressure turbine nozzle of gas turbine engine. The CHT code was verified by comparison between CFD results and experimental results of C3X vane. The combination of k-${\omega}$ based SST turbulence model and transition model was used to solve the flow and thermal field of the fluid zone and the material property of CMSX-4 was applied to the solid zone. The turbine nozzle has two internal cooling channels and each channel has a complex cooling configurations, such as the film cooling, jet impingement, pedestal and rib turbulator. The parabolic temperature profile was given to the inlet condition of the nozzle to simulate the combustor exit condition. The flow characteristics were analyzed by comparing with uncooled nozzle vane. The Mach number around the vane increased due to the increase of coolant mass flow flowed in the main flow passage. The maximum cooling effectiveness (91 %) at the vane surface is located in the middle of pressure side which is effected by the film cooling and the rib turbulrator. The region of the minimum cooling effectiveness (44.8 %) was positioned at the leading edge. And the results show that the TBC layer increases the average cooling effectiveness up to 18 %.

• 대한기계학회논문집B
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• 제37권10호
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• pp.933-940
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• 2013

본 실험에서는 실제 태양광 발전용 인버터의 냉각에 사용할 2개의 압출형과 2개의 압입형 히트싱크의 방열 성능을 평가하였다. 두 압입형 히트싱크의 핀의 개수는 62개와 98개, 전열면적은 $2.8m^2$, $5.3m^2$이고, 두 압출형 히트싱크의 핀의 개수는 38개와 47개, 전열면적은 $1.8m^2$, $1.9m^2$이다. 압입형 히트싱크의 방열율은 각각 82.7 %, 86.3 %, 압출형 히트싱크의 방열율은 각각 79.6 %, 81.6 %로 측정되었다. 각 히트싱크의 방열성능 평가결과에서 히트싱크의 전열면적이 증가할수록 방열율이 증가하는 경향을 보였다. 압입형인 S-62 히트싱크는 압출형인 E-47 히트싱크 보다 전열면적이 47.4 % 증가하였음에도 불구하고 방열량은 1.3% 증가하는데 그쳤다. 이는 압출형의 우수한 전열성능 때문인 것으로 판단된다. 또한 압입형인 S-98 히트싱크는 동일한 압입형인 S-62 히트싱크에 비해 전열면적이 89.3 % 증대되었음에도 방열량 증가는 4.4 %에 불과하여 전열면적에 대한 최적화가 필요함을 알 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.385-388
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• 2002

The researches of a two-phase atomizers have been carried out in the field of automotive and aerospace industries in order to improve the atomization performance of the liquid droplets ejecting from these nozzles. The smaller droplets have the advantages of the reduction of environmental pollution matter and effective use of energy through the improvement of heat and mass transfer efficiency. Thus, to propose the basic information of two-phase flow, an internal mixing atomizer was designed, its shape factor was 0.6 and the liquid feeding hole was positioned at the center of the mixing tube which was used to mix the air and liquid. The experimental work was performed in the field after the nozzle exit orifice. The measurement of the liquid droplets was made by PDPA system. This system can measure the velocity and size of the droplets simultaneously. The number of the droplets used in this calculation was set to 10,000. The flow patterns were regulated by ALR (Air to Liquid mass Ratio). ALR was varied from 0.1024 to 0.3238 depending on the mass flow rate of the air. The analysis of sampling data was mainly focused on the spray characteristics such as flow characteristics distributions, half-width of spray, RMS, and turbulent kinetic energy with ALR.

• 한국항공우주학회지
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• 제40권9호
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• pp.745-751
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• 2012

하이브리드 로켓은 축 방향의 산화제 유동과 고체 연료의 기화로 인한 벽면 분출 유동사이의 상호 간섭에 의해 복잡한 형태의 혼합 전단층이 존재한다. 연소실 입구에 링이 설치되어 있고 질량분사가 있는 실린더 유동에 대하여 압축성 효과를 고려한 LES(Large Eddy Simulation) 기법을 적용하여 수치계산을 수행하였다. 최근의 실험에 의하면 연료 중간에 링과 같은 다이아프램이 설치된 경우, 연소율의 증가가 관찰되었다. 계산 결과에 따르면, 축방향 유동과 벽면 분출 유동이 상호 간섭하여 발생하는 벽면 와류가 국부적인 연료 표면으로의 열전달을 증가시켜 실험에서 관찰되는 딤플이 생성되는 것을 확인하였다. 또한 연소실 입구에 설치된 링에 의하여 발생되는 와류는 벽면 와류가 보다 활발하게 생성되고 열전달과 혼합을 향상시키는 역할을 하며 이 때문에 연소율이 증가되는 것으로 보인다.

• Clinical and Experimental Reproductive Medicine
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• 제42권3호
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• pp.94-100
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• 2015

Objective: The goal of this study was to ascertain optimal assisted hatching (AH) method in frozen embryo transfer. We compared the effect of depending on whether mechanical or laser-AH was performed before or after the vitrification of embryo development rate and blastocyst cell numbers. Methods: In order to induce superovulation, pregnant mare's serum gonadotropin followed by human chorionic gonadotropin were injected into 4- to 5-week-old female mice. 2-cell embryos were then collected by flushing out the oviducts. The Expanded blastocysts were recovered after the collected embryos were incubated for 48 hours, and were then subjected to artificial shrinkage (AS) and cross-mechanical AH (cMAH) or quarter-laser zona thinning-AH (qLZT-AH) were carried out using the expanded blastocysts before or after vitrification. After 48 hours of incubation, followed by vitrification and thawing (V-T), and blastocysts were fluorescence stained and observed. Results: The rate of formation of hatched blastocysts after 24 and 72 hours of incubation was significantly higher in the AS/qLZT-AH/V-T group than in the other groups (p<0.05). The cell number of the inner cell mass was higher in AS/V-T/non-AH and AS/V-T/cMAH groups than those of others (p<0.05). In the control group, the number of trophectoderm and the total cell number were higher than in the AS-AH group (p<0.05). Conclusion: The above results suggest that AS and AH in vitrification of expanded blastocysts lead to the more efficient formation of hatched blastocysts in mice.