• Journal of Korea Water Resources Association
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• v.38 no.6 s.155
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• pp.429-438
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• 2005

In this study, a couple of ordinary differential equations which can describe random waves are derived from the Boussinesq equations. Incident random waves are generated by using the TMA(TEXEL storm, MARSEN, ARSLOE) shallow-water spectrum. The governing equations are integrated with the 4-th order Runge-Kutta method. By using newly derived wave equations, nonlinear energy interaction of propagating waves in constant depth is studied. The characteristics of random waves propagate over a sinusoidally varying topography lying on a sloping beach are also investigated numerically. Transmission and reflection of random waves are considerably affected by nonlinearity.

• Analytical Science and Technology
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• v.21 no.1
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• pp.58-63
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• 2008

Nano-sized ZnO crystals were successfully incorporated using ion exchange method in TMA-A zeolite synthesized by the hydrothermal method. The optimal composition for the synthesis of TMA-A zeolite was resulted in a solution of $Al(i-pro)_3$ : 2.2 TEOS : 2.4 TMAOH : 0.3 NaOH : 200 $H_2O$. 0.3 g of TMA-A zeolite and 5 mol of $ZnCl_2$ solution were employed for the preparation of ZnO incorporated TMA-A zeolite. The crystallization process of ZnO incorporated TMA-A zeolite was analyzed by X-ray diffraction (XRD). The incorporated nano-sized ZnO crystals and the crystallinity of TMA-A zeolite were evaluated by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The size of the incorporated nano-sized ZnO crystals was 3~5 nm, while the TMA-A zeolite was 60~100 nm. The bonding structure and absorption of the ZnO incorporated TMA-A zeolite were compared with the ZnO and TMA-A zeolite by the FT-IR analysis. Subsequentlly, the ZnO incorporated TMA-A zeolite showed the photoluminescent characteristics on the wavelengths of 330~260 nm and 260~230 nm by measurement of UV spectrophotometer.

• Food Science of Animal Resources
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• v.31 no.1
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• pp.115-121
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• 2011

The objective of this study was to develop models to predict freshness factors (total viable counts (TVC), pH, volatile basic nitrogen (VBN), trimethylamine (TMA), and thiobarbituric acid (TBA) values) and the storage period in beef using a visible and near-infrared (NIR) spectroscopic technique. A total of 216 beef spectra were collected during the storage period from 0 to 14 d at a $10^{\circ}C$ storage. A spectrophotometer was used to measure reflectance spectra from beef samples, and beef freshness spectra were divided into a calibration set and a validation set. Multi-linear regression (MLR) models using the stepwise method were developed to predict the factors. The MLR results showed that beef freshness had a good correlation between the predicted and measured factors using the selected wavelength. The correlation of determination ($r^2$), standard error of prediction (SEP), and ratio of standard deviation to SEP (RPD) of the prediction set for TVC was 0.74, 0.64, and 2.75 Log CFU/$cm^2$, respectively. The $r^2$, SEP, and RPD values for pH were 0.43, 0.10, and 1.10; those for VBN were 0.73, 1.45, and 2.00 mg%; those for TMA were 0.70, 0.19, and 2.58 mg%; those for TBA values were 0.73, 0.13, and 2.77 mg MA/kg; and those for storage period were 0.77, 1.94, and 2.53 d, respectively. The results indicate that visible and NIR spectroscopy can predict beef freshness during storage.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.163-163
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• 2016

선박의 대형화 등으로 인한 세계적인 항만들이 하역능력의 제고를 위하여 선박의 대형화, 고속화, 전용선화에 있어 큰 움직임을 보이고 있다. 또한 항만의 연간 작업가능일수 확보를 위하여 신항만 건설시 항 내 정온도 향상을 위하여 최적의 방파제 배치 및 최선의 소파기술에 대한 연구지원을 아끼지 않고 있다. 이뿐 아니라 최근 파랑 수치모형의 정확성이 향상되고 계산시간이 단축됨으로써 각 격자 상에 입력된 수심정보와 입사경계에서의 입사정보 경계면에서의 경계(반사율) 정보로부터 손쉽게 천해파랑 정보를 산출할 수 있게 되었다. 본 연구에서는 스펙트럼을 통해 각각의 파고와 주기를 추출하였으며, 쌍곡선형 완경사 방정식을 수치 해석하여 불규칙파의 설계파를 산정하였다. 또한 Matlab을 사용하여 전 프로그램이 toolbox화 됨으로써 운영하는데 편리하고 특히 다양한 지형의 적용에 용이하게 되었다. Matlab은 다른 언어와 달리 전 프로그램이 vectorizing 되어 계산시간이 상당히 단축되었다. 본 연구를 통해 실무자들이 항만이나 어항 등 연안해역 개발시 유의파고를 사전에 예측하여 연안해역 개발하는 데 큰 도움이 되리라 기대한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.7
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• pp.904-914
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• 2020

Through the Ministry of Trade, Industry, and Energy, South Korea is trying to support the "Building Project for Liquified Natural Gas (LNG) Bunkering Ship," centered on the Korea Gas Corporation, while the Ministry of Maritime Af airs and Fisheries is pushing to construct an LNG bunkering terminal at Busan New Port. LNG bunkering ships are essential for supplying LNG fuel from the terminal to the ships, resulting in the need for safety operation procedures. Therefore, in this study, the stability of a coastal LNG bunkering ship operating from Busan New Port to the anchorage in Busan Port was assessed to investigate the need for operational procedures for coastal LNG bunkering ships. Seakeeping analysis of the LNG bunkering ship was performed for each significant wave height by combining the response amplitude operator from the ship motion analysis under the potential flow theory with the actual observed sea data for five years and Texel, Marsen, and Arsloe (TMA) spectrum suitable for the Busan coast. The results showed that the roll and horizontal acceleration were the main risks that affected the navigation seakeeping performance above a significance wave height of 2 m. The operational periods of the LNG bunkering ship ranged from 83.3% to 99.9% of the total observation period.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.4
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• pp.342-354
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• 2008

Some statistical characteristics of deepwater waves along the Korean coast have been investigated using various sources of wave measurement and hindcasting data. For very large waves comparable to design waves, it is recommended to use the average value of the empirical formulas proposed by Shore Protection Manual in 1977 and by Goda in 2003 for the relation between significant wave height and period. The standard deviation of significant wave periods non-dimensionalized with respect to the mean value for a certain significant wave height varies between 0.04 and 0.21 with a typical value of 0.1 depending upon different regions and different ranges of significant wave heights. The mean and standard deviation of the principal deepwater wave direction are presented at the 106 coastal grid points along the Korean coast. For relatively large waves, the probability density function of the directional spreading parameter $s_{max}$ is expressed as a lognormal distribution. The most suitable frequency spectrum in the Korean coast is the TMA spectrum. The probability density function of the peak enhancement factor $\gamma$ is also expressed as a lognormal distribution, with its mean value of 2.94, which is close to the value in the North Sea.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.443-443
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• 2013

유기광전자소자는 아주 얇은 두께로 제작 가능하여 휘어지는 소자를 구현할 수 있다. 이런 장점 때문에 플렉서블 디스플레이, 플렉서블 태양전지 구현에 가장 적합한 소자로 각광받고 있다. 하지만 수분이나 산소에 의한 소자내의 유기물과 금속의 열화로 소자의 수명이 줄어들기 때문에 산소 및 수분 침투를 방지하는 봉지기술(encapsulation)이 필요하다. 본 연구는 원자층 증착법을 이용한 무기박막층과 분자층 증착법을 이용한 폴리머박막의 적층구조를 이용하여 유기소자에 적용할 수 있는 수분 투과 방지막을 제작하였다. 무기박막층으로는 trymethylaluminum (TMA)과 $H_2O$를 사용하여 $Al_2O_3$를 제작하였고 폴리머층으로는 TMA와 ethylene glycol를 사용하여 alucone박막을 제작하였다. 폴리머층으로 사용된 alucone박막의 X-선 광전자 분광 스펙트럼은 대기중 수분과 산소에 의한 화학결합구조의 변화를 보였지만, $Al_2O_3$와 적층구조로 사용되었을 때, 배리어특성을 증가시키고 휘어짐에 따른 보호막의 열화현상을 줄여줄 수 있는 것을 Ca-test를 통해 확인하였다. 이러한 현상은 alucone막을 적층함으로써 $Al_2O_3$를 침투한 소량의 수분과 산소가, alucone박막을 지나면서 다음 $Al_2O_3$ 층으로 침투하기 전까지의 경로를 늘려주기 때문이라 사료된다.