• Environmental and Resource Economics Review
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• v.18 no.1
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• pp.139-158
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• 2009

With the sample of Middle East crude oil imported to South Korea, this study empirically analyzes the effectiveness of the risk management strategies using derivatives such as futures and options. Assuming the hedging period of one to twelve months, it considers a spot purchasing strategy, 1 : 1 futures hedge strategy, OLS-based minimum-variance futures hedge strategy, buying call option strategy, and collar transaction strategy. According to the ex-ante result, using the derivatives of futures or options makes lower the procurement costs when the crude oil prices is increasing. With the hedging period less than or equal to six months, the hedging strategy using futures turns out to be superior in terms of procurement cost reduction and hedging effectiveness improvement. In contrast, the hedging strategies of buying call option and collar transaction would generate better results when the hedging program last over six months.

• Journal of the Korean Applied Science and Technology
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• v.30 no.4
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• pp.688-700
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• 2013

The potential of biodiesel production technology using lipids extracted from sewage sludge was investigated. Despite the bright prospect of biodiesel production, efforts to commercialize it have been very limited. One of the major obstacles has been the high price associated with refined oil feedstock, which makes up nearly 70-75% of the total production costs. Hence, in order to reduce the cost of biodiesel production, using cheaper feedstock such as waste oil or low-quality oil has been proposed. Especially, sewage sludge, a relatively inexpensive feedstock, is a promising raw material for such a purpose. In this study, it is aimed to review biodiesel production technology from sewage sludge as a lipid feedstock. It is process modifications to combine the oil extraction steps, fuel conversion steps (i.e. in situ transesterification, thermo-chemical process with non-catalytic heterogeneous biodiesel production) and fuel quality from sewage sludge.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.3
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• pp.321-332
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• 2015

In an attempt to find the improvement of the fishing efficiency according to the hull form remodeling for the 3 tuna purse seiner, the Catch-Per-Unit-Effort (CPUE) for that undertaken before (2008) and after (2010) was analyzed. In addition, the CPUE of 6 similar ships operated same period and same fishing ground. As result, it came to verify that the three modified ships had a significant value on the CPUE. An another index for the improvement of fishing efficiency is the rate of reduction of fuel oil consumption for the modified ships. Fuel oil consumption per day in service speed as comparing with the original ships were reduced 2.1%, 4.0% and 5.1% on the modified ship A, B, and C respectively. And each ship's service speed was increased 1.0 kt, 0.6 kt, and 0.4 kt according to the modified ship A, B, and C in due order. In the conclusion, the remodeling job with newly equipped bulbous bow, lengthened slipway and enlarged rudder area were improved fairly much on fuel oil efficiency, the ship's speed, and in the end, that led to the improving fishing efficiency. Hence, the remodeling of tuna purse seiner come to improve not only the fishing performance, but contribute to the reduction of operating cost by saving energy for the fisheries industry.

• Environmental and Resource Economics Review
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• v.16 no.3
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• pp.653-682
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• 2007

In this study, multi-sectoral partial equilibrium and computable general equilibrium models of Taiwan are used to investigate the direct and indirect effects of energy price increases on overall economies and agro-food sector in Taiwan. The results suggest that agricultural prices, production cost would increase between 0.27% to 1.88%, and a reduction in GDP around 0.39% to 0.54 %. The negative impact on livestock sector is slightly higher than that on the crop sector. Negative impacts are also observed in the employment and wages. The rising oil price has the potential to discourage production of energy-intensive activity because of the possibility of substitution and adaptations. The growth rate of real GDP will shrink by 0.64% to 1.06% and CPI will increase by 1.17% to 1,95%. Both the agriculture and non-agricultural sector also respond by raising output prices by 0.80% to 1.33%. The rising international oil price has urged the government to take policy actions like using alternative fuels such as biodiesel, bioethanol, and adopting measures to cut down on energy consumptions mainly in transportation sectors in response to public concern over economic shocks.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.491-494
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• 2007

Recently Gas & Oil plant construction projects are increasing in the world. The EPC (Engineering, Procurement and Construction) company, which participate in the plant projects, should possess the pertinent engineering license and procurement skill to create high added-value. It is because the procurement is very substantial to cover 70% of the total project cost. Nonetheless, there exist various risks involved in the procurement process due to the characteristics of the construction projects with long duration and complicated process as well as the procured goods or services subjected to various logistics. The objective of this paper is to analyze proper process in the procurement and to identify various information and document. Also to analyze procurement process, the principal data are derived from the interview with experts and specialty contractors of plant project. The result of this study would widely be used as a guide to the procurement personnel in forecasting the risks in advance.

• Journal of the Korean Society of Mineral and Energy Resources Engineers
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• v.55 no.6
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• pp.660-669
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• 2018

Enhanced oil recovery (EOR) is a method used to improve the recovery factor of remaining hydrocarbon in reservoir. Polymer and surfactant EOR techniques have limitations depending on reservoir or production conditions (temperature, salinity, etc.) because the polymer and surfactant are highly affected by the reservoir conditions. In this study, analysis of the current improvements to chemical substances and application technologies was performed based on recent research data. Conventional polymer is readily degraded by the conditions of high temperature and high salinity. Therefore, new polymers and injection techniques have been developed to remediate such problems. In addition, surfactant applicable to shale and carbonate reservoirs is developed as petroleum recovery expands to unconventional reservoirs. However, these chemical substances are not widely used in the current oil fields due to high costs. Therefore, further studies must be conducted to reduce the cost and thus increase the effectiveness of EOR techniques.

• Earthquakes and Structures
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• v.20 no.1
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• pp.109-122
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• 2021

Significant progress in the oil and gas industry advances the application of pipeline into an intelligent era, which poses rigorous requirements on pipeline safety, reliability, and maintainability, especially when crossing seismic zones. In general, strike-slip faults are prone to induce large deformation leading to local buckling and global rupture eventually. To evaluate the performance and safety of pipelines in this situation, numerical simulations are proved to be a relatively accurate and reliable technique based on the built-in physical models and advanced grid technology. However, the computational cost is prohibitive, so one has to wait for a long time to attain a calculation result for complex large-scale pipelines. In this manuscript, an efficient and accurate surrogate model based on machine learning is proposed for strain demand prediction of buried X80 pipelines subjected to strike-slip faults. Specifically, the support vector regression model serves as a surrogate model to learn the high-dimensional nonlinear relationship which maps multiple input variables, including pipe geometries, internal pressures, and strike-slip displacements, to output variables (namely tensile strains and compressive strains). The effectiveness and efficiency of the proposed method are validated by numerical studies considering different effects caused by structural sizes, internal pressure, and strike-slip movements.

• Journal of The Korean Society of Integrative Medicine
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• v.11 no.3
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• pp.219-226
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• 2023

Purpose : The purpose of this study was to compare changes of salivary flow rate, salivary buffering capacity, and S. mutans after using a mouthwash containing essential oil or probiotics widely used as oral lactic acid bacteria in the oral environment. Methods : Fifty-three healthy adults aged 20 years or older voluntarily participated in this study after they were informed of the purpose of this study. Subjects were divided into a group treated with probiotics (L. reuteri) and a group treated with mouthwash containing essential oil. To evaluate changes in the oral environment, salivary flow rate, salivary buffering capacity, and S. mutans test were performed at baseline and 4 weeks later. Unstimulated and stimulated salivary flow samples were collected for 5 minutes and results were recorded in ml per minute. Salivary buffering capacity was divided into scores of 1 (low), 2 (moderate) and 3 (high) according to the color of the strip. The amount of S. mutans was classified as scores of 0, 1, 2, and 3 according to the decision table. Data collected in this study were analyzed at the 95 % significance level using the SPSS Version 23.0 program. Results : Both the unstimulated salivary flow rate and the stimulated salivary flow rate increased statistically after the intervention compared to those before intervention in the probiotics group. However, there was no statistically significant difference between the probiotics group and the mouthwash group. Salivary buffering capacity and S. mutans results showed no statistically significant differences between the probiotics group and the mouthwash group either. The salivary buffering capacity and the salivary flow rate showed a positive correlation. Conclusion : To improve the oral environment, such as salivary flow rate and salivary buffering capacity, an optimal product can be selected in consideration of individual preference and cost-effectiveness.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.5
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• pp.803-812
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• 2023

The subsea separator of an offshore plant for offshore oil and gas development performs the process of separating oil and gas from crude oil produced in the subsea. The oil-gas subsea separator can be divided into a gravity type that separates fluids by gravity and an in-line type that separates fluids using centrifugal force of density. In the case of the deep sea, the development of a small in-line type separator is required due to manufacturing cost and safety problems caused by water pressure. Therefore, in this study, the gas-liquid phase separation efficiency of the subsea separator was identified through the study of the multiphase flow characteristics of the in-line type separator. For the optimal design of the in-line type separator, the shape of the internal swirl element(ISE) was selected first, and the separation efficiency results for each section of the in-line type separator were analyzed. This study was conducted in parallel with experiments and numerical analysis, and it is expected that the reliability and efficiency of the in-line type separator will be improved through the results.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1747-1753
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• 2024

The accurate determination of formation density and the physical properties of rocks is the most critical logging tasks which can be obtained using gamma-ray transport and detection tools. Though the simulation works published so far have considerably improved the knowledge of the parameters that govern the responses of the detectors in these tools, recent studies have found considerable differences between the results of using a conventional model of a homogeneous mixture of formation and fluid and an inhomogeneous fractured medium. It has increased concerns about the importance of the complexity of the model used for the medium in simulation works. In the present study, we have suggested two various models for the flow of the fluid in porous media and fractured rock to be used for logging purposes. For a typical gamma-gamma logging tool containing a ¹³⁷Cs source and two NaI detectors, simulated by using the MCNPX code, a simplified porous (SP) model in which the formation is filled with elongated rectangular cubes loaded with either mineral material or oil was investigated. In this model, the oil directly reaches the top of the medium and the connection between the pores is not guaranteed. In the other model, the medium is a large 3-D matrix of 1 cm³ randomly filled cubes. The designed algorithm to fill the matrix sites is so that this realistic random (RR) model provides the continuum growth of oil flow in various disordered directions and, therefore, fulfills the concerns about modeling the rock textures consist of extremely complex pore structures. For an arbitrary set of oil concentrations and various formation materials, the response of the detectors in the logging tool has been considered as a criterion to assess the effect of modeling for the distribution of pores in the formation on simulation studies. The results show that defining a RR model for describing heterogeneities of a porous medium does not effectively improve the prediction of the responses of logging tools. Taking into account the computational cost of the particle transport in the complex geometries in the Monte Carlo method, the SP model can be satisfactory for gamma-gamma logging purposes.