• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.169-172
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• 1995

Establishment of a diagnosing technology for the deterioration of reinforced concrete structures due to salt contamination is urgent, but few analytical methods based on measured data obtained from concrete structures have been presented so far. Chloride penetration into concrete from sea water is generally understood and analysed as diffusion of chloride ion. This paper presents a new method of predicting chloride penetration into concrete based on diffusion theory. Also, it determines the duralility of Marine structure in service with the prediction of remaiing lifetime by the carvonation test.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.179-182
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• 2010

본 연구에서는 MLS 차분법을 이용하여 동역학 문제를 해석하기 위한 explicit 동적해석 알고리즘을 제시한다. 격자망이 없는 장점을 부각시키기 위해 이동최소제곱법에 근거한 Taylor 전개로부터 미분근사를 얻고 차분식을 구성했다. 지배 미분방정식의 시간항을 CDM(Central difference Method) 차분하여 빠른 속도로 동적해석을 수행하였다. 수치결과를 통해 본 연구에서 제시한 알고리즘의 정확성과 안정성을 확인할 수 있었다.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.59-60
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• 2001

산업의 발전과 함께 해양환경 중에서 사용되는 항만시설과 해양구조물 등을 비롯하여 철강재로 제작되는 각종 구조물, 공업용수배관, 열교환기, 선박 등의 기계장치나 각종설비는 그 사용 환경이 다양해지고 오염되면서 부식손상이 발생되어 지고있다. 더욱이 강전해질의 해양환경 중에서 기계적인 충격 침식과 더불어 전기화학적인 부식이 중첩하여 발생하는 경우에는 침식과 부식 이 상호간에 가속하는 상승효과 때문에 각종 기계장치 및 설비의 수명에 대한 안정성 확보가 어렵다. (중략)

• Journal of Korea Port Economic Association
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• v.30 no.3
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• pp.187-207
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• 2014

The purpose of this paper is to examine the business performance difference based on the ownership structure type in the aspect of profitability and stability. In order to conduct this analysis in two aspects, the ship financial institutions have been classified into two groups: state-owned banks and private-owned banks. First of all, the difference of ROE and ROA between private and public ship financial institutions is statistically significant, but no difference has been shown in terms of stability measured through BIS capital adequacy ratio. Second, to test the business performance difference according to the ownership structure types before and after the global financial crisis, we examined the outcome difference in the ship financial institutions in terms of profitability and stability. However, in the event that the analysis was conducted with public and private financial institutions, the business outcome difference before and after the global financial crisis has been shown in the sector of private financial institutions, but has not been shown in the sector of public financial institutions. It is meaningful that this study is the first work which examined the difference of the operating performance by the ownership structure types of ship financial institutions. However, it is noted that small sample for this empirical study is a limitation of this thesis.

• Journal of Korea Port Economic Association
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• v.38 no.4
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• pp.87-106
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• 2022

Uncertainties in the energy market are increasing due to technology developments (shale revolution), trade wars, COVID-19, and the Russia-Ukraine war. Especially, since 2020, the risk of international trade in the energy market has increased significantly due to changes in the supply chain of transportation and due to prolonged demand reduction because of COVID-19 and the Russian-Ukraine war. Considering these points, this study analyzed connectedness between energy price, tanker index, and uncertainty to understand the connectedness between international trade in the energy market. Main results are summarized as follows. First, as a result of analyzing stable period and unstable period of the energy price model using the MS-VAR model, it was confirmed that both the crude oil market model and the natural gas market model had a higher probability of maintaining stable period than unstable period, increasing volatility by specific events. Second, looking at the results of the analysis of the connectedness between stable period and unstable period of the energy market, it was confirmed that in the case of total connectedness, connectedness between variables was increased in the unstable period compared to the stable period. In the case of the energy market stable period, considering the degree of connectedness, it was confirmed that the effect of the tanker freight index, which represents the demand-side factor, was significant. Third, unstable period of the natural gas market model increases rapidly compared to the crude oil market model, indicating that the volatility spillover effect of the natural gas market is greater when uncertainties affecting energy prices increase compared to the crude oil market.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.43-52
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• 2021

As port development in soft ground is actively promoted for international logistics and transportation, the Deep Mixing Method (DMM) is continuously applied to form an improved column body directly in the ground by mixing cement with soil to secure the stability of the structure. However, in the case of cement, there is a problem of emitting a lot of greenhouse gases during the production process, so the development and use of new alternative materials are socially required to achieve the national goal of carbon neutrality. Accordingly, in this study, CMD-SOIL, developed to induce a hardening reaction similar to cement by recycling recycled resources, was used as a ground improvement material for the DMM. In addition, it was attempted to determine the possibility of replacing cement by conducting on-site test construction and evaluating applicability. As a result of the study, the compressive strength of CMD-SOIL compared to the design reference strength was 1.46 to 2.64 times higher in the field mixing test and 1.2 to 5.03 times higher than in the confirmed boring. In addition, the ratio (λ) of the compressive strength in the field to the design reference strength was 0.63 to 1.14, which was similar to the previous research results. Therefore, in the case of CMD-SOIL, it is possible to express the compressive strength necessary to secure stability, and there is no difference in applicability compared to existing materials such as ordinary portland cement and blast furnace slag cement, so it was analyzed that it could be used as a ground improvement material for the DMM.

• Journal of Animal Science and Technology
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• v.47 no.6
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• pp.1033-1040
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• 2005

Protein function of ovotransferrin with various pH and temperature, and its antimicrobial characteristics were determined. Foaming ability of ovotransferrin was high in alkali condition (pH 11), then diminished as time follows. In acidic condition (pH 3.0), very little amount of foam was produced and disappeared promptly in 30min. However, neutral condition (pH 7.0) was revealed as the best area for foam production and foam stability of ovotransferrin. Temperature effect on foam stability of ovotransferrin showed that the highest foam was produced at 60℃. Ovotransferrin was shown weak antimicrobial activity against E. Coli, S .typhi, P. aerug and Candida albicans at dose of 12.5mg/ml and 25mg/ml. Anti-microbial effect of ovotransferrin with either lysozyme or albumine on pathogenic bacteria and fungi shows that the most effective dose was 25mg/ml, especially on S. typhi and C. albicans.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.93-101
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• 2004

A method to calculate stability limits is investigated to predict the characteristics of high-frequency combustion instability in liquid-propellant rocket engine. It is based on the theory of linear stability analysis proposed in previous works and useful to predict combustion stability at the beginning stage of engine development. The system of equations governing reactive flow in combustor has the simplified and linearized forms. The overall equation expressing stability limits is adopted. The procedures to evaluate quantitatively each term included in the equation are proposed. The thermo-chemical properties and flow variables required in the evaluation can be obtained from calculation of thermodynamic equilibrium, CFD results, and experimental test data. Based on the existent data, stability limits are calculated with actual rocket engine (KSR-III rocket engine). The present calculations show the reasonable stability limits in a quantitative manner and the stability characteristics of the engine are discussed. The prediction from linear stability analysis could be serve as the first approximation to the true prediction.

• Journal of Convergence for Information Technology
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• v.12 no.5
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• pp.290-297
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• 2022

This study was conducted to determine the cell cytotoxicity, astringency, nitrite oxide scavenging, iNOS protein expression level, pro-inflammatory cytokine, elastase inhibition, and type I pro-collagen synthesis as a functional cosmetics material of Salvia miltiorrhiza root. We prepared the 80% ethanol(SE) and hot-distilled water(SW), respectively. Both SE and SW showed no toxicity from 0.05 to 0.5 mg/mL concentration as a result of MTT assay in NHDF or RAW264.7 cells. In the measurement of astringent effect, SE reveled 74.6% of astringent activity in 10 mg/mL. SE showed that LPS-induced nitric oxide production, iNOS protein expression, and cytokines were inhibited in a dose-dependent manner. Furthermore, two extracts significantly inhibited elastase activity and increased the type I pro-collagen production. Therefore, it is expected that Salvia miltiorrhiza extract is used as a natural material for functional cosmetics that can effectively prevent skin-related inflammation and wrinkles, and aging.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.6
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• pp.495-507
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• 2009

The expected sliding distance for the lifetime of a caisson breakwater has a limitation to be used as the stability criterion of the breakwater. Since the expected sliding distance is calculated as the mean of simulated sliding distances for the lifetime, there is possibility for the actual sliding distance to exceed the expected sliding distance. To overcome this problem, the exceedance probability of the allowable sliding distance is used to assess the stability of sliding. Latin Hypercube sampling and Crude Monte Carlo simulation were used to calculate the exceedance probability. The doubly-truncated normal distribution was considered to complement the physical disadvantage of the normal distribution as the random variable distribution. In the case of using the normal distribution, the cross-sections of Okgye, Hwasun, and Donghae NI before reinforcement were found to be unstable in all the limit states. On the other hand, when applying the doubly-truncated normal distribution, the cross-sections of Hwasun and Donghae NI before reinforcement were evaluated to be unstable in the repairable limit state and all the limit states, respectively. Finally, the shortcoming of the expected sliding distance as the stability criterion was investigated, and we reasonably assessed the stability of sliding of caissons by using the exceedance probability of allowable sliding distance for the caisson breakwaters in Korea.