• Proceedings of the Korea Society of Environmental Biology Conference
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• 2002.05a
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• pp.72-72
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• 2002

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.551.2-551.2
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• 2006

• Journal of Navigation and Port Research
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• v.38 no.6
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• pp.577-583
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• 2014

A ship-to-ship (STS) lightering operation takes place in order to transfer cargo (e.g. crude oil or petroleum products) between an ocean-going ship and a service ship alongside it. Instrumental measurements to accurately determine the relative speeds and distances during the approach between the vessels would benefit the operational safety and efficiency. A velocity information GPS (VI-GPS) system, which uses the instantaneous velocity measures from carrier-phase Doppler measurement, has been applied in a field observation onboard a service ship (Aframax tanker) approaching a ship-to-be-lightered (VLCC) in open waters. This article proposes to apply VI-GPS as the input sensor to a guidance and decision-support system aiming to provide accurate velocity information to the officer in charge of an STS operation. A method for precise velocity measurement using VI-GPS was described and the measurement results were compared each other with the results of Voyage Data Recorder (VDR) and VI-GPS that showed the concept of a guidance and decision-support system applying VI-GPS with the field test results during STS operations. Also, it turned out that VI-GPS has sufficient accuracy to serve as an input sensor from the field test results.

• International Journal of Fluid Machinery and Systems
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• v.2 no.3
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• pp.215-222
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• 2009

Jets issuing through small holes in a wall into a freestream has proven effective in the control of flow separation. This technique is known as the vortex generator jet (VGJs) method. If a precursor signal of separation is found, the separation control system using VGJs can be operated just before the onset of separation and the flow field with no separation is always attained. In this study, we measured the flow field and the wall static pressure in a two-dimensional diffuser to find a precursor signal of flow separation. The streamwise velocity measurements were carried out in the separated shear layer and spectral analysis was applied to the velocity fluctuations at some angles with respect to the diffuser. The pattern of peaks in the spectral analysis changes as the divergence angle increases over the angle of which the whole separation occurs. This change in the spectral pattern is related to the enhancement of the growth of shear layer vortices and appears just before the onset of separation. Therefore, the growth of shear layer vortices can be regarded as a precursor signal to flow separation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2404-2412
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• 1994

A mathematical model has been developed for predicting kinematic, thermal, and solidification histories of atomized droplets during flight. Liquid droplet convective cooling, recalescence, equilibrium-state solidification, and solid-phase cooling were taken into account in the analysis of the solidification process. The spherical shell model was adopted where the heterogeneous nucleation is initiated from the whole surface of a droplet. The growth rate of the solid-liquid interface was determined from the theory of crystal growth kinetics with undercooling caused by the rapid solidification. The solid fraction after recalescence was obtained by using the integral method. The thermal responses of atomized droplets to gas velocity, particle size variation, and degree of undercooling were investigated through the parametric studies. It is possible to evaluate the solid fraction of the droplet according to flight distance and time in terms of a dimensionless parameter derived from the overall energy balance of the system. It is also found that the solid fraction at the end of recalescence is not dependent on the droplet size and nozzle exit velocity but on the degree of subcooling.

• Atmosphere
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• v.33 no.5
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• pp.457-475
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• 2023

Accurately predicting localized heavy rainfall is challenging without high-resolution mesoscale cloud information in the numerical model's initial field, as precipitation intensity and amount vary significantly across regions. In the Korean Peninsula, the radar observation network covers the entire country, providing high-resolution data on hydrometeors which is suitable for data assimilation (DA). During the pre-processing stage, radar reflectivity is classified into hydrometeors (e.g., rain, snow, graupel) using the background temperature field. The mixing ratio of each hydrometeor is converted and inputted into a numerical model. Moreover, assimilating saturated water vapor mixing ratio and decomposing radar radial velocity into a three-dimensional wind vector improves the atmospheric dynamic field. This study presents radar DA experiments using a numerical prediction model to enhance the wind, water vapor, and hydrometeor mixing ratio information. The impact of radar DA on precipitation prediction is analyzed separately for each radar component. Assimilating radial velocity improves the dynamic field, while assimilating hydrometeor mixing ratio reduces the spin-up period in cloud microphysical processes, simulating initial precipitation growth. Assimilating water vapor mixing ratio further captures a moist atmospheric environment, maintaining continuous growth of hydrometeors, resulting in concentrated heavy rainfall. Overall, the radar DA experiment showed a 32.78% improvement in precipitation forecast accuracy compared to experiments without DA across four cases. Further research in related fields is necessary to improve predictions of mesoscale heavy rainfall in South Korea, mitigating its impact on human life and property.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.17 no.2
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• pp.63-68
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• 2017

Gaucher disease (GD) is caused by the deficiency of glucocerebrosidase. In pediatric patients with GD, especially Type I GD, enzyme replacement therapy (ERT) can reduce the hepatosplenomegaly and improve the hematologic finding and growth velocity. Herein, we report a 2-year-old girl with Type I GD presented with hepatosplenomegaly, bone pain and growth retardation. A 2 year-old-girl was referred to our hospital due to severe hepatosplenomegaly and growth retardation. She suffered from both leg pain and chronic fatigue. Simple x-ray showed widened distal long bones like that of an 'Erlenmeyer flask' which is associated with GD. The laboratory test showed anemia and thrombocytopenia. The enzyme activity was markedly reduced and the direct sequencing of the GBA gene showed the compound heterozygous mutations, p.G46E and p.L444P. As the G46E have been considered as the protective gene against neuronopathic genotype, we could assess the Type I GD in this patient. After one year of ERT, the growth velocity became 11 cm per year. Bone pain and fatigue disappeared. The volume of liver and spleen was reduced from $683cm^3$ and $703cm^3$ to $590cm^3$ and $235cm^3$, respectively. Although GD is an extremely rare disease in Korea, growth retardation and bone pain in children are the important signs which lead to early detection of GD and a simple radiologic finding is helpful to assess the GD at outpatient clinic. We highlight that the early diagnosis and early ERT is important for good growth and outcome for pediatric patients with GD.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.3
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• pp.117-124
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• 2010

For Ar=5, Pr=1.18, Le=0.15, Pe=2.89, Cv=1.06, $P_B$=20 Torr, the effects of impurity $(N_2)$ on thermally and solutally buoyancy-driven convection ($Gr_t=3.46{\times}10^4$ and $Gr_s=6.02{\times}10^5$, respectively) are theoretically investigated for further understanding and insight into an essence of thermo-solutal convection occurring in the vapor phase during the physical vapor transport. For $10K{\leq}{\Delta}T{\leq}50K$, the crystal growth rates are intimately related and linearly proportional to a temperature difference between the source and crystal region which is a driving force for thermally buoyancy-driven convection. Moreover, both the dimensionless Peclet number (Pe) and dimensional maximum velocity magnitudes are directly and linearly proportional to ${\Delta}T$. The growth rate is second order-exponentially decayed for $2{\leq}Ar{\leq}5$. This is related to a finding that the effects of side walls tend to stabilize the thermo-solutal convection in the growth reactor. Finally, the growth rate is found to be first order exponentially decayed for $10{\leq}P_B{\leq}200$ Torr.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.7 s.166
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• pp.1120-1128
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• 1999

An elastic-viscoplastic finite element analysis is performed to investigate detailed growth behavior of creep cracks and the numerical results are compared with experimental results. In Cr-Mo steel stress fields obtained from the crack growth method by mesh translation were compared with both cases that the secondary creep rate is only used as creep material property and the primary creep rate is included. Analytical stress fields, Riedel-Rice(RR) field, Hart-Hui-Riedel(HR) field and Prime(named in here) field, and the results obtained by numerical method were evaluated in details. Time vs. stress at crack tip was showed and crack tip stress fields were plotted. These results were compared with analytical stress fields. There is no difference of stress distribution at remote region between the case of 1st creep rate+2nd creep rate and the case of 2nd creep rate only. In case of slow velocity of crack growth, the effect of 1st creep rate is larger than the one of fast crack growth rate. Stress fields at crack tip region we, in order, Prime field, HR field and RR field from crack tip.

• Journal of the Korean Solar Energy Society
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• v.29 no.4
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• pp.7-14
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• 2009

Nucleate pool boiling experiments with constant heat flux condition were performed using pure R11 and R113 for various surface angles under saturated pool condition. A circular heater of 1 mm diameter, with artificial cavity in the center, fabricated using MEMS technique and the high-speed controller were used to maintain the constant heat flux. Images of bubble growth were taken at 5,000 frames per second using a high-speed CCD camera. The bubble geometry was obtained from the captured bubble images. The effects of surface angles on the bubble growth behaviors were analyzed as dimensional scales for the initial and thermal growth regions. The parameters for the bubble growth behaviors were bubble radius, bubble growth rate, sliding velocity, bubble shape and advancing and receding contact angles. These phenomena require further analysis for various surface angles, but this study will provide good experimental data with constant heat flux boundary condition for such works.