• Journal of The Korean Society of Agricultural Engineers
• /
• v.56 no.2
• /
• pp.59-64
• /
• 2014

In this study, the large scale test was performed to investigate the behavior of failure for the embankment and spillway transitional zone by overtopping. The pore water pressure, earth pressure, settlement and failure pattern of covering embankment with geotextile were compared and analyzed. The pore water pressure showed a small change in the spillway transition zone and core, indicating that the geotextile efficiently reinforced the embankment. The earth pressure decreased the infiltration of the pore water only in inclined cores type to secure local stability. The behavior of failure started from the bottom and gradually progressed upwards. After the intermediate overtopping period (100 min), width and depth of the seepage erosion were very small due to the effect of geotextile which delayed failure. Therefore, the reinforced method by geotxtile was a very effective method to respond to the emergency due to overtopping.

• Nuclear Engineering and Technology
• /
• v.55 no.11
• /
• pp.3973-3982
• /
• 2023

As for two-phase flow in rectangular channels, the flow regimes especially like churn-turbulent and annular flow are significant for the physical problem like Countercurrent Flow Limitation (CCFL). In this study, the rectangular channels with cross-sections of 4 × 66 mm, 6 × 66 mm, 8 × 66 mm are adopted to investigate the flow regimes of air-water vertical upward two phase flow under adiabatic condition. The gas and liquid superficial velocities are 0 ≤ j_g ≤ 20m/s and 0.25 ≤ j_f ≤ 3m/s respectively which covering bubbly to annular flow. The flow regimes are identified by random forest algorithm and the flow regime maps are obtained. As the results, the transitional void fraction from slug to churn turbulent flow fluctuate from 0.47 to 0.58 which is significantly affected by the dimensional size of channel and flow rate. Besides, the void fraction at transitional points from churn-turbulent (slug) to annular flow are 0.66-0.67, which are independent with the gap size. Furthermore, a new criteria of slug to churn-turbulent flow is established in this study. In addition, by introducing the interfacial force model, the criteria of churn-turbulent (slug) flow to annular flow is verified.

• Journal of Mechanical Science and Technology
• /
• v.17 no.4
• /
• pp.562-570
• /
• 2003

This experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin friction coefficients have been measured for fully developed flows of water and of 0.4% aqueous solution of sodium carboxymethyl cellulose (CMC), respectively, when the inner cylinder rotates at the speed of 0～600 rpm. Also, the visualization of vortex flows has been performed to observe the unstable waves. The results of present study reveal the relation of the bulk flow Reynolds number Re and Rossby number Ro with respect to the skin friction coefficients. In somehow, they show the existence of flow instability mechanism. The effect of rotation on the skin friction coefficient is significantly dependent on the flow regime. The change of skin friction coefficient corresponding to the variation of rotating speed is large for the laminar flow regime, whereas it becomes smaller as Re increases for the transitional flow regime and. then, it gradually approach to zero for the turbulent flow regime. Consequently, the critical (bulk flow) Reynolds number Re$\_$c/ decreases as the rotational speed increases. Thus, the rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.337-340
• /
• 2002

The present experimental and numerical investigations are performed for the characteristics of transitional flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one rotating. The flow field of an annulus has been numerically solved using a finite volume method. The pressure losses and Skin-friction coefficients have been measured for the fully developed flow of water and $0.2{\%}$ aqueous solution of sodium carboximethy1 cellulose (CMC), respectively at inner cylinder rotational speed of $0{\~}600rpm$. The transitional flow has been examined by the measurement of pressure losses to reveal the relation of the Reynolds and Rossby numbers with the skin-friction coefficients. The occurrence of transition has been checked by the gradient changes of pressure losses and skin-friction coefficients with respect to the Reynolds numbers. Consequently the critical(axial-flow) Reynolds number decreases as the rotational speed increases. Thus, the rotation of inner cylinder promotes the early occurrence of transition due to the onset of Taylor vortices.

• Journal of the Korean Wood Science and Technology
• /
• v.33 no.2 s.130
• /
• pp.17-23
• /
• 2005

Juvenile and transitional-juvenile wood samples from loblolly pine (Pinus taeda) were immersed in water to investigate longitudinal and tangential swelling properties. Increment cores from twenty-six loblolly pine trees were sampled at breast height (1.37 m). Earlywood rings 5 and 9 were separated from the core, extracted, oven-dried and immersed in water at room temperature. The variance in longitudinal swell was significant for ring 5 compared to ring 9 (p = 0.001). It was found that tangential swell might predict longitudinal swelling of juvenile wood at ring 9 but not at ring 5. Poor correlation in ring 5 suggests that swelling response in younger juvenile wood may differ. The swell response at ring 5 did not follow the shrinkage models discussed in the literature while ring 9 adhered to the expected curve.

• Animal cells and systems
• /
• v.16 no.1
• /
• pp.77-84
• /
• 2012

The objective of the study was to investigate if reproductive characteristics of $Pandalus$ $eous$ affect the depth distribution in the East Sea of Korea. $P.$ $eous$ was found at depths of 500-900 m in the East Sea of Korea, with the highest percentage occurrence (34%) at 500 m. A negative correlation was observed between the number of individuals and the depth. The overall sex ratio also turned out to be significantly correlated with depth. On average, the larger individuals (bigger than 26.37 cm), which included transitional, female, and ovigerous females, were mostly distributed at 700 m depth. The percentage of males increased by depth and ovigerous females were mainly distributed in the shallow water (300 m) during winter. Ovigerous females were not found at 900 m, which is the deepest depth range in this study. The percentage of transitional individuals was greatest at 500 m and decreased gradually with depth. All ovigerous female individuals were of the spent ovarian stage in winter. Female numbers in the ripe ovarian stage increased with depth and immature females rarely appeared. The gonadosomatic indices of the nonovigerous females and ovigerous females were highest at 700 m in depth. The mean egg size of $P.$ $eous$ was $0.83{\pm}0.11mm^3$ in the non-eyed stage and $0.93{\pm}0.17mm^3$ in the eyed stage.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.261-264
• /
• 2006

This paper deal with development of dredging equipment that proper water head elimination method changing transitional dredging method. Numerical simulation and model test were accomplished for development of seabed sediment inhalation equipment using water head. Sediment elimination system by the difference of water head has been analysed by numerical method. Model test was achieved for inhalation equipment performance test using water head by primary design. Also sediment elimination system has designed and developed that doesn't occur secondary pollution phenomenon. To verify the numerical results are compared with experimental results.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.14 no.3
• /
• pp.171-180
• /
• 2009

Based on the constituent analysis of sediments near Dok Island, the origin and sedimentary facies were Investigated. The sediments are mainly from originated from volcanic and volcaniclastic rock fragments derived from Dok Island and carbonate sediments formed by a variety of shallow-dwelling organisms that secreted calcareous skeletons. Carbonate producers include mollusks (bivalves and gastropods), encrusting & branching bryozoans, encrusting & segmented red algae, worm tubes, barnacles, diatoms, sponge spicules and echinoderm fragments. The distribution and relative amount of these constituents are basically dependent upon water depth and grain size even though local variations can be observed within the same depth interval. Five sedimentary facies can be divided: nearshore facies (<20 m), neritic facies ($20{\sim}100m$), upper transitional facies ($100{\sim}200m$), lower transitional facies ($200{\sim}700m$), and hemipelagic facies (>700 m). The sediments that were sampled below the water depth of 2,000 m still contain a significant amount of carbonates (ca. $10{\sim}20%$), implying that the carbonate compensation depth in the East Sea may well exceed this water depth.

• Journal of Environmental Impact Assessment
• /
• v.20 no.3
• /
• pp.325-335
• /
• 2011

Estuary is a transitional zone between river and ocean environment that receives the maritime and riverine influence simultaneously. Estuaries are the most productive habitats because their incoming water provides large quantities of nutrients. The Seomjin River estuary, located in the middle south of Korea, has no barrage and shows natural characteristic of estuary. However, due to dredging and reclamation the environment of the estuary has been changed significantly in the river mouth. In addition, increased freshwater intake in midstream of the Seomjin River results in salinity intrusion. In this paper salinity variation in downstream estuary of the Seomjin River has been simulated and tested using EFDC model. The results of simulation were compared with measured data collected at three points, Culture & Art Center, Sumjin Iron Bridge, and Mokdori, located at 9Km, 14Km, and 15.5Km respectively from downstream estuary. Based on the simulated results, the contribution of the flushing discharge has been evaluated in preventing the salinity intrusion by increasing the discharge flowrates released from the Juam dam.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1014-1017
• /
• 2007

본 연구에서는 K-mean 알고리즘을 이용하여 수지조사지점을 클러스터링하고, 수질변화 특성을 비교 분석하였다. 현행 용담댐 저수지의 호내 수질조사점은 10개소를 운용하고 있으나, 샘플링의 경제성과 효율성을 위하여 수질변동 특성이 유사한 몇 개의 지점으로 클러스터링을 할 필요성이 있다. 군집의 개수를 3개, 4개, 5개로 변화해 가면서 알고리즘을 적용한 결과, 크게 3개의 영역으로 분류되었다. 즉, 지류의 유입부분과 용담호의 중류 지역 그리고 댐앞 지점으로 분류되었다. 지류로 부터의 오염부하 유입에 따른 영향을 직접적으로 받는 3번, 8번, 9번 조사지점은 수질변동 특성이 유사한 것으로 분석되었으나, 공간적으로 이격되어 있어 조사지점을 계속 유지하는 것이 바람직할 것으로 판단된다. 용담호의 중류에 해당하는 5번, 6번, 7번 지점은 하천과 호소의 중간적인 성격을 지닌 전이지대(transitional zone)에 해당하며, 수질변동특성이 유사하여 하나의 조사지점으로 통합하는 것이 적절할 것으로 판단된다. 1번, 2번, 4번 조사지점은 댐앞 지점으로써 호소의 성격이 강한 지점으로 볼 수 있으며, 하나의 조사지점으로 통합할 수 있다. 통합된 조사지점의 강우기 수질 변화는 매우 유사한 패턴을 보이고 있는 것을 확인할 수 있다.