• Journal of Energy Engineering
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• v.24 no.1
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• pp.149-163
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• 2015

In this study, we conducted study on the confirmation of thermal-hydraulic safety for Mast assembly with Computational Fluid Dynamics(CFD) analysis. Before performing the natural convection analysis for the Mast assembly by using CFD code, we validated the CFD code against two benchmark natural convection data for the evaluation of turbulence models and confirmation of its applicability to the natural convection flow. From the first benchmark test which was performed by Betts et al. in the simple rectangular channel, we selected standard k-omega turbulence model for natural convection. And then, calculation performance of CFD code was also investigated in the sub-channel of rod bundle by comparing with PNL(Pacific Northwest Laboratory) experimental data and prediction results by MATRA and Fluent 12.0 which were performed by Kwon et al.. Finally, we performed main natural convection analysis for fuel assembly inside the Mast assembly by using validated turbulence model. From the calculation, we observed stable natural circulation flow between the mast assembly and pool side and evaluated the thermal-hydraulic safety by calculating the departure from nucleate boiling ratio.

• Korean Journal of Optics and Photonics
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• v.30 no.5
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• pp.193-196
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• 2019

The design and control of thermal flow is important for the operation of high-power laser diodes (LDs). It is necessary to analyze and improve the thermal bottleneck near the active layer of an LD. As the error in prediction of the thermal resistance of an LD is large, typically due to the hyperbolic increase and saturation to linear increase of the thermal resistance as a function of thickness, it is helpful to use a simple, modified divergence model for the improvement and optimization of thermal resistance. The characteristics of LDs are described quite well, in that the values for simulated thermal resistance curves and the thermal cross section followed are almost the same as the values from the model function. Also, the thermal-cross-section curve obtained by differentiating the thermal resistance is good for identifying thermal bottlenecks intuitively, and is also fitted quite well by the model proposed for both a typical LD structure and an improved LD with thin capping and high thermal conductivity.

• Journal of Convergence Society for SMB
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• v.6 no.4
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• pp.85-91
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• 2016

This study is to research the tear film stability for 48 eyes, agreed the purpose of study, didn't have no contact lens wearing and were tested all two times in a day. Their visual acuity was more than 0.8, corrective visual acuity more than 0.8, the fattest K-reading, apical corneal radius, was in 7.40~8.40mm, corneal astigment was less than 1.00D and orthophoria. The tests, tear scope test, tear film break up time test(TBUT) and schirmer test order, were performed their functions before and after their working at interval of 6 hours over. The tearscope test results was no difference, TBUT was no difference, although 1.2 seconds more in the afternoon, shcirmer test was decreased 2.0mm in the afternoon.

• Journal of Energy Engineering
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• v.25 no.3
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• pp.66-72
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• 2016

In this study, a sulfonated poly(arylene ether ketone) block copolymer was prepared from hydrophilic oligomer and hydrophobic oligomer. The structure of the prepared membrane was characterized by $^1H$-NMR, FT-IR and GPC. The $M_w$(weight-average molecular weights) of the polymer was $209,700g\;mol^{-1}$ and the molecular weight distribution($M_w/M_n$) of 1.25 was obtained. The prepared membrane showed excellent thermal stability with gradual weight loss up to $200^{\circ}C$. The proton conductivity of SPAEK block copolymer reached the maximum of $9.0mS\;cm^{-1}$ at $90^{\circ}C$ under 100% relative humidity (RH). From the observed results, it is necessary to do more aggressive attempt to study the possibility of application as an ion-conductive composite electrolyte.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.37-42
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• 2008

Purpose: This study is to prepare tintable hard coatings for plastic lenses and to evaluate spectroscopic and surface characteristic for these coatings. Methods: These coatings had been prepared by the sol-gel method using TEOS, MTMS and GPTS. Scanning electron microscopy (SEM), Raman spectroscopy, infrared (IR) spectroscopy and UV/VIS spectroscopy have been used to investigate the optical and structural characteristics of the coatings. Results: Tint ability of this coating was about 2 times higher than general hard coatings. The lenses applied by tintable hard coatings showed excellent adhesion, abrasion resistance, hot water resistance, and chemical resistance. Pencil hardness was 5H and the surface of coatings was smooth and free of cracks. Conclusions: This hard coating system for plastic lenses offered a hard and stable surface that could be tinted.

• Journal of IKEEE
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• v.22 no.2
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• pp.274-280
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• 2018

In this paper, we have developed the vacuum infusion automation system for the safety and quality advancement of the boat. It is necessary for the precise mixing rate of resinoid and curingagent to inject in an inner ship and deck at short time. We need for the optimal condition to a strengthen construction of boat. This one can solve the post deformability of the strengthen structure and can control the precise mixing rate of resinoid and curingagent to the resinoid fluidity and flowing rate per time. Under these condition, we can advance the an quality construction that based on the model and database information of the boat. Also, we can have an effective process management and retrench the production cost.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.604-604
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• 2012

국지성 집중호우에 따른 도심지 내수 침수 피해의 주원인으로 하수관거의 설계기준을 초과하는 강우가 침수피해의 주요 원인이며, 도심화로 인해 불투수 면적이 증가함에 따라 유출되는 시간이 짧아 저지대의 피해는 불가피하다. 2010년과 2011년에 100년 이상의 강우사상이 서울시에 연이어 나타나면서 집중호우로 인한 피해지역이 유사하게 나타났으며, 광화문 거리의 연이은 침수는 현재 서울시의 하수관거의 용량과 빗물펌프장 및 저류조 시설로 구성된 기존 수방대책의 한계점을 보이고 있다. 이에 서울시는 광화문 일대의 배수능력을 향상시키기 위하여 효자배수분구 빗물배수터널을 계획하고 있다. 일본, 미국 및 유럽 등지에서는 대심도 지하수로 시설에 대한 수리실험 및 수치 연구를 바탕으로 다양한 지하방수로가 건설되어 국지성 집중 강우에 대해 적절히 대응하고 있으나, 국내의 경우에는 대심도 지하방수로 시설에 대한 연구가 미비하여 지하방수로 설계 지침 및 기술적 자료가 부족한 실정이다. 그러므로 대심도 빗물배수터널 시설에서의 흐름특성 분석에 관한 수리실험 및 수치해석 등의 구체적인 연구가 필요하다고 판단된다. 본 연구에서는 수리모형 실험의 물질적 및 시간적 한계를 극복하기 위하여 일반적으로 3차원 유체거동의 특성분석에 많이 사용되는 Fluent 6.3 모형을 이용하여 대심도 빗물배수터널 시설의 접선식 유입구에 대한 흐름특성을 수치모의 하였다. 접선식 유입구 및 수직갱(drop shaft)에 대한 기하 모형의 격자망은 수치해석의 안정성 확보를 위하여 그림 1과 같이 6면체 격자로 구성하였다. 맨홀 내의 다상유동을 고려하기 위하여 VOF(Volume of Fluid) Scheme을 적용하였으며, 수치해석 방법으로는 비정상류, 1st order implicit method를 사용하였다. Fluent에서의 난류 흐름을 계산하는 방법에는 난류 운동에너지와 난류 에너지 소산율 $\epsilon$의 전달 방정식을 도입한 k-$\epsilon$ 난류 모형을 채택하였다.

• Journal of Korea Port Economic Association
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• v.25 no.2
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• pp.259-276
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• 2009

The study herein has focused on offering foundation infrastructure in order for seamen who arrive at Korean ports to use internet service smoothly in waiting time and free time. It also concentrated on how to build communication infrastructure for efficient operations when improving existing ports and developing new ports. For this, it has grasped the tendency of researches concerning the existing port communication and has also investigated the status and problems of communication infrastructure being used currently in ports. So it has suggested several realistic development methods based on mesh network and has reviewed them in terms of the stability, economic feasibility and efficiency. Additionally, this research offers the results of the performance test conducted on major equipment in market by the suggested methods. This research can be a good guideline in building wireless communication systems of ports and is expected to contribute to creating traffic volume by improving the image of ports.

• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.245-252
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• 2021

A turbidity current in a river and a lake occurs due to diverse nutrient loading including suspended sediment in sediment runoff, which affects water withdrawal and river environments. We developed one dimensional time-variant numerical model based on Python for the Nagdonggang mainstream. We examined the numerical stability and the applicability of the model by performing the simulation of quasi-steady flow in non-flooding for three cases, which are different according to the point and the amount of turbidity inflows in the Nagdonggang upstream and a tributary. The result was reasonable in the respect of the conservation of matter. The model will facilitate to simulate a large river if we can secure the data of turbidity variations in a target river reach or measured points in a field.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.129-143
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• 2017

The shallow sediments in the southwestern Ulleung Basin consist of mass flow deposits such as slide/slump and debris flow deposits (DFD), caused by slope failure. These sediments are proven to be important in studying geological disaster and stability of the seafloor. In this paper, we analysised the flow accumulation and slope failure susceptibility of the Ulleung Basin on the basis of multi-beam data, collected in this area. We also studied the distribution pattern and the seismic characteristics of the DFD in the uppermost layer of the Ulleung Basin on the basis of seismic data. The slope susceptibility was calculated as the frequency ratio of each factors including slope, aspect, curvature and stream power index (SPI), which causes the slope failure. These results indicate that the slope failure is frequently to occur in the southern and western continental slope of the Ulleung Basin. The sediment flow (mass flow) caused by the slope failure converges to the north and northwest of the Ulleung Basin. According to the seismic characteristics, the uppermost layer in study area can be divided into four sedimentary unit. These sedimentary units develop from the south and southwest to the north and northwest in association with slope susceptibility and flow accumulation.