• Ocean and Polar Research
• /
• 제35권3호
• /
• pp.249-258
• /
• 2013

Vertical and horizontal mixing processes in the ocean mixed layer determine sea surface temperature and temperature variability. Accordingly, simulating these processes properly is crucial in order to obtain more accurate climate simulations and more reliable future projections using an ocean general circulation model (OGCM). In this study, by using Modular Ocean Model version 4 (MOM4) developed by Geophysical Fluid Dynamics Laboratory, the upper ocean temperature and mixed layer depth were simulated with two different vertical mixing schemes that are most widely used and then compared. The resultant differences were analyzed to understand the underlying mechanism, especially in the Tropical Pacific Ocean where the differences appeared to be the greatest. One of the schemes was the so-called KPP scheme that uses K-Profile parameterization with nonlocal vertical mixing and the other was the N scheme that was rather recently developed based on a second-order turbulence closure. In the equatorial Pacific, the N scheme simulates the mixed layer at a deeper level than the KPP scheme. One of the reasons is that the total vertical diffusivity coefficient simulated with the N scheme is ten times larger, at maximum, in the surface layer compared to the KPP scheme. Another reason is that the zonal current simulated with the N scheme peaks at a deeper ocean level than the KPP scheme, which indicates that the vertical shear was simulated on a larger scale by the N scheme and it enhanced the mixed layer depth. It is notable that while the N scheme simulates a deeper mixed layer in the equatorial Pacific compared to the KPP scheme, the sea surface temperature (SST) simulated with the N scheme was cooler in the central Pacific and warmer in the eastern Pacific. We postulated that the reason for this is that in the central Pacific atmospheric forcing plays an important role in determining SST and so does a strong upwelling in the eastern Pacific. In conclusion, what determines SST is crucial in interpreting the relationship between SST and mixed layer depth.

• 설비공학논문집
• /
• 제7권2호
• /
• pp.184-195
• /
• 1995

A theoretical one-dimensional model for the charging process in stratified thermal storage tanks is established presuming that the fluid ensuing from the tank inlet creates a perfectly mixed, layer above the thermocline. Both the generic and asymptotic closed-form solutions are obtained via the Laplace transformation. The asymptotic solution describes the nature of the charging pertaining to the case of no thermal diffusion, whereas the generic solution is of practical importance to understand the role of operating parameters on the stratification. The present model is validated through comparison with available experimental data, where they agree well with each other within a reasonable limit. An interpretation of the exact solution entails two important features associated with the charging process. The first is that an in-crease in the mixing depth $h_m$ causes a relatively slow temperature rise in the perfectly mixed region, but on the other hand it results in a faster decay of the overall temperature gradient across the thermocline. Next is the predominance of the mixing depth in the presence of the prefectly mixed region. In such a case the effect of the Peclet number is marginal and there-fore the thermal characteristics are solely dependent on the mixing depth paticularly for large $h_m$. The Peclet number affects significantly only for the case without mixing. Variation of the storage efficiency in response to the change in the mass flow rate agrees favorably with the published experimental results, which confirms the utility of the present study.

• 태양에너지
• /
• 제15권2호
• /
• pp.25-37
• /
• 1995

유입관성에 의한 유체혼합뿐 아니라 입구온도의 변화까지 고려된 성층축열조의 충전과정 모델에 대하여 해석적 근사해를 제시하였다. 해석모델은 깊이가 일정한 완전혼합 및 압출유동영역으로 구성되며, 입구온도의 변화는 중첩의 원리에 근거하여 계단함수로 근사화하였다. 완전혼합영역의 과도온도를 구한 후 함수형태에 따라 구분하고, 각각을 경계조건으로 하는 압출유동영역의 온도분포를 잘 정의된 함수의 항으로 유도하였다. 결과적으로 이들의 일차결합이 압출유동영역에 대한 최종해이다. 근사해의 타당성 및 결과의 유용성은 입구온도가 선형적으로 증가하는 경우에 대한 엄밀해와의 비교를 통하여 검증하였다. 계단수의 증가에 따라 근사해는 엄밀해로 급속히 접근하며, 유한한 수의 계단에 의한 근사해도 광범위한 혼합깊이에 대하여 엄밀해와 잘 일치한다. 또한, 혼합깊이가 클수록 소수의 계단에 의한 근사해로도 의미있는 예측결과를 얻을 수 있었다.

• 대한기계학회논문집B
• /
• 제31권8호
• /
• pp.711-717
• /
• 2007

Shape optimization of a staggered herringbone groove micromixer using three-dimensional Navier-Stokes analysis has been carried using Kriging model. The analysis of the degree of mixing is performed by the calculation of spatial data statistics. The calculation of the variance of the mass fraction at various nodes on a plane in the channel is used to quantify mixing. A numerical optimization technique with Kriging model is applied to optimize the shape of the grooves on a single wall of the channel. Three design variables, namely, the ratio of groove width to groove pitch, the ratio of the groove depth to channel height ratio and the angle of the groove, are selected for optimization. A mixing index is used as the objective function. The results of the optimization show that the mixing is very sensitive to the shape of the groove which can be used in controlling mixing in microdevices.

• Korean Chemical Engineering Research
• /
• 제60권3호
• /
• pp.468-471
• /
• 2022

헬리컬 리본 임펠러 교반조의 중심축과 헬리컬 리본을 지지하는 스트럿의 영향을 실험과 가시화를 통하여 검토한 결과, 액위 변화에 따른 불완전 혼합부의 발생 등 혼합성능에 크게 악영향을 미치는 것은 종 방향의 중심축이 아니라 횡 방향의 스트럿임을 밝혔다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제14권3호
• /
• pp.1121-1141
• /
• 2020

We propose a robust visual object tracking algorithm fusing a convolutional neural network tracker trained offline from a large number of video repositories and a color histogram based tracker to track objects for mixing immersive audio. Our algorithm addresses the problem of occlusion and large movements of the CNN based GOTURN generic object tracker. The key idea is the offline training of a binary classifier with the color histogram similarity values estimated via both trackers used in this method to opt appropriate tracker for target tracking and update both trackers with the predicted bounding box position of the target to continue tracking. Furthermore, a histogram similarity constraint is applied before updating the trackers to maximize the tracking accuracy. Finally, we compute the depth(z) of the target object by one of the prominent unsupervised monocular depth estimation algorithms to ensure the necessary 3D position of the tracked object to mix the immersive audio into that object. Our proposed algorithm demonstrates about 2% improved accuracy over the outperforming GOTURN algorithm in the existing VOT2014 tracking benchmark. Additionally, our tracker also works well to track multiple objects utilizing the concept of single object tracker but no demonstrations on any MOT benchmark.

• 한국지반공학회논문집
• /
• 제23권3호
• /
• pp.133-140
• /
• 2007

DCM공법(심층혼합처리 공법)은 흙막이 벽체 등 구조물 조성에 적용하였다. 이러한 DCM 벽체는 경질층에서 관입능력이 있어야 한다. DCM 장비에 부착된 교반날개에 의해 경질지반의 관입능력이 증가되는 알아보기 위해 특수교반날개가 고안되었다. 경질점토층에 관입되는 특수교반날개의 관입특성은 김해와 인천현장에서 조사하였다. 고안한 특수교반날개는 관입속도가 다소 느려도 N=30 이상 되는 지반까지 관입되었고 관입시 효율이 경질지반에서 낮아질 수 있으므로 경제적인 교반날개의 관입깊이를 분석하였다.

• Asian-Australasian Journal of Animal Sciences
• /
• 제27권7호
• /
• pp.1050-1056
• /
• 2014

This study investigated the main factors influencing digester temperature and methods to reduce heat losses during the cold season in the subtropics. Four composite digesters (two insulated and two uninsulated) were buried underground to measure their internal temperature ($^{\circ}C$) at a depth of 140 cm and 180 cm, biogas production and methane ($CH_4$) concentration in biogas from August to February. In parallel the temperature of the air (100 cm above ground), in the slurry mixing tank and in the soil (10, 100, 140, and 180 cm depth) was measured by thermocouple. The influent amount was measured daily and the influent chemical composition was measured monthly during the whole experimental period. Seasonal variations in air temperature significantly affected the temperature in the soil, mixing tank and digester. Consequently, biogas production, which is temperature dependent, was influenced by the season. The main factors determining the internal temperature in the digesters were insulation with Styrofoam, air temperature and temperature of slurry in the mixing tank. Biogas production is low due to the cold climate conditions in winter in Northern Vietnam, but the study proved that storing slurry in the mixing tank until its temperature peak at around 14:00 h will increase the temperature in the digester and thus increase potential biogas production. Algorithms are provided linking digester temperature to the temperature of slurry in the mixing tank.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
• /
• pp.918-921
• /
• 2006

The short-term variation of sea surface temperature before and after typhoons and increase of chlorophyll a concentration that accompany with the typhoons during summer in the East/Japan Sea were explored by satellite. Four typhoons (NAMTHEUN, MEGI, CHABA and SONGDA) and a typhoon (NABI) passed over the East/Japan Sea in 2004 and 2005, respectively. Decreasing of SST was observed in the every five typhoons, however the magnitude of SST decreasing were various from 1 to $5^{\circ}C$. Chlorophyll a increases were found after the typhoons (0.1-3 ${\mu}g$ $l^{-1})$ except NAMTHEUN, and the area was approximately included in SST decreasing area by the typhoons. It suggests that chlorophyll a increase was caused by nutrient input from subsurface layer by strong mixing. On the other hand, rarely chlorophyll a increase was observed in northern area of polar frontal zone, which is located in $38-41^{\circ}N$, than northern area, and chlorophyll a increase in coastal area was higher (more than 3 times) than offshore area. It might suggest that chlorophyll a increase in the East/Japan Sea is also related with the depth or nitracline depth that affects the amount of nutrients supply to the upper layer by typhoon mixing.

• 한국분무공학회지
• /
• 제7권1호
• /
• pp.21-28
• /
• 2002

The mixing of propellant and its mass distribution of unlike-doublet impinging injector, which is known to affect the combustion efficiency significantly, have been studied using PLIF(Planar Laser Induced Fluorescence). The results show that fuel jet penetrates considerably into the oxidizer jet at impinging point as variation of momentum ratio. and then stream flows inclined because of variation of momentum ratio. Consequently, the mixing efficiency shows that maximum efficiency is at MR=3. after MR=3, mining efficiency decreases slightly.