• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.22-22
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• 2011

기존의 빈도해석(frequency analysis) 방법은 자료의 정상성(stationarity)을 가정하고 있다. 즉, 자료 분포가 기상에 영향을 받는 정도가 통계적으로 유의하지 않다는 것을 의미하는데 최근의 관측값들은 주기를 나타내거나 증가, 감소하는 경향을 자주 보이고 있고 이는 정상성에 대한 가정이 더 이상 유효하지 않음을 의미한다. 본 연구는 최근 증가경향이 두드러지게 나타나고 있는 관측 연최대 일강우량을 대상으로 증가 변동점(changing point)을 탐색하였다. 이를 위하여 Barry and Hartigan이 1999년에 제안한 BCP (Bayesian Change Point) 방법을 우리나라 전체 강우 관측지점에 적용하였다. 적용 결과, 2000년대를 기준으로 이전의 관측값과 통계적 특성이 다른 관측값들이 많이 발생하는 것을 알 수 있었다. 향후, 매개변수와 시간의 회귀분석(regression analysis)으로 확률분포형의 미래 매개변수를 구하는 비정상성 빈도해석 방법 적용시, BCP 결과로 얻은 변동점을 바탕으로 회귀분석의 구간을 적절하게 선택한다면 계산된 결과의 신뢰성이 더욱 향상되리라 본다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.142-142
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• 2017

High Flory-Huggins interaction parameter (${\chi}$)를 가지는 polystyrene-block-dimethylsiloxane (PS-b-PDMS)는 초미세 패턴 제작과 우수한 defect density, 우수한 edge roughness 특성으로 향상된 패턴을 제공한다는 점에서 반도체 분야에서 많은 연구가 되고 있다. 하지만, PS와 PDMS 사이에 존재하는 큰 surface tension의 차이로 인해 PDMS는 PS와 air 사이에서 segregate되기 때문에 수직배향에 불리하여 high aspect ratio (HAR)을 가지는 cylinder, lamellar 패턴 제작에 있어 큰 어려움을 가진다. 본 연구에서는 이러한 문제를 해결하기 위해, PS-b-PDMS BCP 패턴과 하부 실리콘 기판 사이에 amorphous carbon layer (ACL)를 삽입하여 효과적으로 pattern transfer하는 공정을 연구하였다. 플라즈마를 이용하여 무한대에 가까운 etch selectivity를 가지는 식각 공정을 개발함으로써 낮은 aspect ratio를 가지는 PS-b-PDMS BCP 패턴의 한계점을 극복하였다. Large-x value를 가지는 BCPs를 이용하여도 매우 높은 aspect ratio를 가지면서 동시에 pattern quality를 향상시킬 수 있는 plasma process를 제시하였다.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.220-228
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• 2018

In this study, we found a simple surface biofunctionalization of biphasic calcium phosphate (BCP) based on the high affinity between alendronate and the calcium ions of BCP, and the strong interaction between heparin and bone morphogenic protein-2 (BMP-2). The biofunctionalized BCP did not be precipitated well and display a remarkable enhancement of osteogenic activity of human adipose-derived stem cells by showing increased alkaline phosphatase (ALP), calcium deposition and osteogenic-related genes (i.e., Runx-2, ALP, osteocalcin, and osteopontin), and bone regeneration in the calvarial defect model. Therefore, this simple surface technique can be used to easily functionalize various calcium phosphates.

• Journal of Korea Water Resources Association
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• v.47 no.8
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• pp.671-684
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• 2014

Change point analysis is a efficient tool to understand the fundamental information in hydro-meteorological data such as rainfall, discharge, temperature etc. Especially, this fundamental information to change points to future rainfall data identified by reasonable detection skills can affect the prediction of flood and drought occurrence because well detected change points provide a key to resolve the non-stationary or inhomogeneous problem by climate change. Therefore, in this study, the comparative study to assess the performance of the 3 change point detection skills, cumulative sum (CUSUM) method, Bayesian change point (BCP) method, and segmentation by dynamic programming (DP) was performed. After assessment of the performance of the proposed detection skills using the 3 types of the synthetic series, the 2 reasonable detection skills were applied to the observed and future rainfall data at the 5 rainfall gauges in South Korea. Finally, it was suggested that BCP (with 0.9 posterior probability) could be best detection skill and DP could be reasonably recommended through the comparative study. Also it was suggested that BCP (with 0.9 posterior probability) and DP detection skills to find some change points could be reasonable at the North-eastern part in South Korea. In future, the results in this study can be efficiently used to resolve the non-stationary problems in hydrological modeling considering inhomogeneity or nonstationarity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.2
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• pp.92-98
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• 2012

The co-precipitation technique has been applied to synthesize biphasic calcium phosphate (BCP). $Ca(NO_3)_2{\cdot}4H_2O$, $(NH_4)_2HPO_4$, TEOS and $Mg(NO_3)_2{\cdot}6H_2O$ as the starting materials was used. After the heat treatment of powder crystalline phases HAp and ${\beta}$-TCP analysis showed a mixed phase. The overall spectra appear to have mainly two modes corresponding to characteristic $PO^{3-}_4$ and $OH^-$ groups. After immersion in Hanks' Balanced Salt Solution (HBSS) for 1 week a precipitation started to be formed with individual small granules on the specimen surface. An MTT assay indicated that ionic substituted BCP powders had no cytotoxic effects on MG-63 cells, and that they have good biocompatibility.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.5
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• pp.237-242
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• 2010

Magnesium-substituted BCP (biphasic calcium phosphate) powders were prepared by incorporating small amounts of magnesium into the structure of different hydroxyapatite (HAp)/${\beta}$-tricalcium phosphate (${\beta}$-TCP) ratios through coprecipitation method. A series of magnesium substitutions ranging from 0, 0.5, and 1.0 wt%, which are comparable to the measured magnesium contents, were performed. The obtained powders were characterized by the following analytical techniques: X-ray diffraction analysis (XRD), Thermo Gravimetric Analyzer (TGA) and Fourier transform infrared spectroscopy (FT-IR). The results have shown that substitution of magnesium in the calcium-deficient apatites resulted in the formation of biphasic mixtures of different HAP/${\beta}$-TCP ratios after heating above $1000^{\circ}C$. The 1.0 wt% magnesiumsubstituted-BCP were soaked in Hank's solutions after 2 weeks to observe the morphology of the biocement, especially needle-like hydroxyapatite crystals and to estimate the length and diameter of nanoneedle crystals.

• 한국약용작물학회:학술대회논문집
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• 2008.11a
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• pp.394-395
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• 2008

• 베이커리
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• no.8 s.433
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• pp.108-111
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• 2004

• Korean Chemical Engineering Research
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• v.52 no.6
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• pp.743-749
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• 2014

Even if many studies for the prevention of accidents in chemical plant have been carried out, recently more severe accidents in chemical plants have occurred continuously. These have a large potential impact and the loss of casualties and economic can vary according to the activities of early emergency responses. Thus, in order to mitigate the impact of accidents, the studies preparing the guidelines for emergency response have to be urgently needed. In this study, the current emergency responses guidelines and regulations in Korea were investigated to find out the drawbacks. And, to tackle these, BCP(Business continuity plan) method was used to improve the activities of early emergency responses as suggesting the basic components, response steps, feedback and procedures of the emergency responses.

• Journal of Periodontal and Implant Science
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• v.45 no.2
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• pp.46-55
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• 2015

Purpose: This study evaluated the mechanical and structural properties of biphasic calcium phosphate (BCP) blocks processed using a modified extrusion method, and assessed their in vivo effectiveness using a rabbit calvarial defect model. Methods: BCP blocks with three distinct ratios of hydroxyapatite (HA):tricalcium phosphate (TCP) were produced using a modified extrusion method:HA8 (8%:92%), HA48 (48%:52%), and HA80 (80%:20%). The blocks were examined using scanning electron microscopy, X-ray diffractometry, and a universal test machine. Four circular defects 8 mm in diameter were made in 12 rabbits. One defect in each animal served as a control, and the other three defects received the BCP blocks. The rabbits were sacrificed at either two weeks (n=6) or eight weeks (n=6) postoperatively. Results: The pore size, porosity, and compressive strength of the three types of bone block were $140-170{\mu}m$, >70%, and 4-9 MPa, respectively. Histologic and histomorphometric observations revealed that the augmented space was well maintained, but limited bone formation was observed around the defect base and defect margins. No significant differences were found in the amount of new bone formation, graft material resorption, or bone infiltration among the three types of BCP block at either of the postoperative healing points. Conclusions: Block bone substitutes with three distinct compositions (i.e., HA:TCP ratios) processed by a modified extrusion method exhibited limited osteoconductive potency, but excellent space-maintaining capability. Further investigations are required to improve the processing method.