• 설비공학논문집
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• 제18권10호
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• pp.811-818
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• 2006

Mixing vanes have been installed in the space grid of nuclear fuel rod bundle to improve turbulent heat transfer. Split mixing vanes induce the vortex flow in the cooling water to swirl in sub-channel of fuel assembly. But, The swirling flow decays rapidly so that the heat transfer enhancing effect limited to short length after the mixing vane. In the present study, the large scale vortex flow (LSVF) is generated by rearranging the mixing vanes to the coordinated directions. This LSVF mixing vanes generate the most strong secondary flow vortices which maintain about $35D_h$ after the spacer grid. The streamwise vorticity generated by LSVF sustain two times more than that split mixing vane.

• 한국수소및신에너지학회논문집
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• 제23권6호
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• pp.678-687
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• 2012

Concentration fields of solid powder in a liquid fuel were quantitatively measured by a visualization technique. The measurement system consists of a camcoder and three LCD monitors. The solid powder (glass powder) were filled in a head tank which was installed over a main mixing tank ($D{\times}H$, $310{\times}370mm$). The main mixing tank was filled with JetA1 fuel oil. With a sudden opening of the upper tank by pressurized nitrogen gas with 1.9 bar, the solid powder were poured into the JetA1 oil. An impeller type agitator was being rotated in the mixing with 700 rpm for the enhancements of mixing. Uniform visualization for the mixing flow field was made by the light from the three LCD monitors, and the visualized images were captured by the camcoder. The color images captured by the camcoder The color information of the captured images was decoded into three principle colors R, G, and B to get quantitattive relations between the concentrations of the solid powder and the colors. To get better fitting for the strong non-linearity between the concentration and the color, a neural network which has strong fitting performances was used. Analyses on the transient mixing of the solid powders were quantitatively made.

• Applied Science and Convergence Technology
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• 제27권5호
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• pp.86-89
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• 2018

Observations of neutrino oscillations are very strong evidence for the existence of neutrino masses and mixing. From recent experimental results on neutrino oscillation, we find that neutrino mixing angles are quite consistent with the so-called tri-bi-maximal mixing pattern, but the deviation from observational results is non-negligible. However, the tri-bi-maximal mixing pattern is still useful as a leading order approximation and provides a good guideline to search for the flavor symmetry in the neutrino sector. We introduce the $S_4$ permutation symmetry as a flavor symmetry to the standard model of particle physics with additional particle contents of heavy right-handed neutrinos and scalar fields. Finally, we obtain the tri-bi-maximal mixing pattern as a mixing matrix in the lepton sector within the suggested model. To derive the required unitary mixing matrix for the neutrino sector, the double seesaw mechanism is utilized.

• Journal of the Korean Statistical Society
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• 제28권2호
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• pp.253-264
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• 1999

Conditinal weakly convergence of the blockwise bootstrapped empirical process for stationary sequences to the appropriate Gaussian process is reestablished particularly for severely dependent $\alpha$-mixing sequences. Issue of block size is discussed from the point of validity of bootstrap method.

• 대한기계학회논문집
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• 제18권3호
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• pp.690-700
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• 1994

The effects of thermal stratification on the flow of a stratified fluid past a circular cylinder were examined in a wind tunnel. In order to produce strong thermal stratifications, a compact heat exchanger type variable electric heater is employed. Linear temperature gradient of up to $250^{\circ}C/m$ can be well sustained. The velocity and temperature profiles in the cylinder wake with a strong thermal gradient of $200^{\circ}C/m$ were measured and the smoke wire flow visualization method was used to investigate the wake characteristics. It is found that the temperature field effects as an active contaminant, so that the mean velocity and temperature profiles can not sustain their symmetricity about the wake centerline when such a strong thermal gradient is superimposed. It is evident that the turbulent mixing in the upper half section is stronger than that of the lower half of the wake in a stably stratified flow.

• 한국해양환경ㆍ에너지학회지
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• 제4권2호
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• pp.15-24
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• 2001

Huang 등[1996]이 제안한 해양방류 혼합구역에 대한 분석방법을 활용하여 마산만 해양방류 해역의 혼합구역에서 주변해수의 흐름과 밀도성층의 변화에 따른 혼합 희석에 의한 수중방류하수의 농도변화분포를 산정하였다. 방류해역에서 5월 중순부터 8월 중순까지 3개월 동안 연속 관측된 조류의 매 시간별 유향과 유속변화에 따른 혼합구역에서의 하수농도분포를 계산하고, 마산만 해수유동에 있어 가장 큰 요소인 조류의 변화를 고려하여 15일 간격으로 방류하수의 평균된 농도분포를 구하였다. 이 결과에 의하면 조류의 유속이 상대적으로 강했던 기간동안에는 혼합구역에서의 평균농도는 매우 낮았고, 유속이 약했던 기간에는 낮은 희석률로 인해 평균농도가 매우 높게 나타났다. 그리고 관측된 조류의 주 방향으로 인해 혼합구역이 방류해역의 서측 해안까지 확장됨을 나타내었으며, 이는 방류해역에서 조사된 퇴적물의 오염도 분포결과와도 잘 일치되었다.

• Journal of applied mathematics & informatics
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• 제29권1_2호
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• pp.201-210
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• 2011

In this paper, we obtain the H$\`{a}$jeck-R$\`{e}$nyi type inequality and the strong law of large numbers for asymptotically linear negative quadrant dependent random variables by using this inequality. We also give the strong law of large numbers for the linear process under asymptotically linear negative quadrant dependence assumption.

• Communications for Statistical Applications and Methods
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• 제20권3호
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• pp.193-197
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• 2013

Almost sure central limit theorems are established for a stationary bootstrap sample mean of strong mixing processes. Both weak and strong consistencies are obtained.

• Ocean and Polar Research
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• 제44권3호
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• pp.191-207
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• 2022

Using the results of CTD casts made in Spring from 2017 to 2021, in this study we investigated the water mass distribution and occurrence of temperature inversion in the western seas of Jeju Island in spring. The distribution of water masses was characterized by cold and fresh water in the northwest and warm and saline water in the southeast, forming a strong thermohaline front running in the southwest-to-northeast direction. Strong temperature inversion mainly occurred in the frontal boundary when the cold water intrudes beneath the warm water at depths of 30-50 m. Analysis of the mixing ratio demonstrated that Jeju Warm Water is dominantly distributed in the western seas of Jeju Island, but its ratio can be modified depending on the southward extension of Yellow Sea Cold Water (YSCW). Results of in situ measurement showed that in 2020, the YSCW largely expanded to the western seas of Jeju Island, occupying approximately 40 % of the mixing ratio. Due to the expansion of YSCW, a strong thermohaline front was formed in the study area, thereby causing thick and strong temperature inversion. On the other hand, in 2018 the mixing ratio of YSCW was minimum (~18%) during the study period of 2017-2021, and thus a relatively weak frontal boundary was formed, without the occurrence of temperature inversion. The observational results also suggest that the interannual changes of water mass distribution and the associated temperature inversion in the western seas of Jeju Island are closely related with wind-driven Yellow Sea circulation in spring, which is the summer monsoon transition period.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.391-398
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• 2008

LES analysis was conducted with in-house CFD code to investigate the turbulence evolution and interaction due to turbulence ring and splash plate in the gas generator. Though chemical reaction was not accounted for, the results can be useful in determining the turbulence characteristics generated by ring and plate. The calculation results show that the installation of turbulence ring can introduce additional turbulences and improve turbulent mixing in the downstream flow. However, the addition of splash plate in the downstream of TR brings totally different shape of perturbation energy and enstrophy distribution for turbulent mixing. This enhancement can be done by the formation of the intensively strong vorticity production and mixing behind the plate. Pressure drop was found to be a reasonable level of about 1% or less of initial pressure in all calculation cases. Also, calculation results revealed that the variation of TR shape and intrusion length did not change the characteristics of turbulent mixing in the chamber. Even though the effect of installation location of splash plate on the turbulent mixing is not investigated yet, calculation results conclude the addition of splash plate leads to the increase in turbulent mixing with an acceptable pressure drop.