• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3548-3556
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• 2015

In order to fulfill the needs of reliable and economically feasible foundation, engineers should consider not only the working load that can endure extreme conditions but also apprehending precise behavior of continuous dynamic load while designing the foundation of offshore wind power generators. To actualize the foundation, a model pile was made in miniature. Also, calibration chamber was made and a 500mm height of sand-bed was made to perform "static lateral load experiment" and "repetitive loading experiment", total of two Lateral load tests. As a result, in Static Lateral load test, the bigger length/diameter of model pile led an increase in load displacement. However, when performing "Cyclic Lateral load test", the increase in number of under loading led the decrease in horizontal displacement from each repeated lateral load. While performing Static Lateral load test and repeated loading experiment, we could observe the decreasing in the rate of ultimate lateral load capacity increase of the pile. Also, it turned out that the higher relative density of the ground, the lower ultimate lateral load capacity by repeated horizontal loading.

• The Korean Journal of Petroleum Geology
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• v.14 no.1
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• pp.36-44
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• 2008

Natural gas in tight reservoirs, one of unconventional hydrocarbon resources, has become a significant exploration and exploitation targets. Tight gas reservoirs are the gas-bearing rocks that commonly have a permeability of less than 0.1 millidarcy (mD). Tight gas reservoirs are characterized by extensive and deep locations as well as abnormal pressure such as over- or under-pressure. The tight gas reservoirs are independent of structural or stratigraphic traps, whereas conventional gases normally occur at these traps. Tight gas reservoirs can be productive when stimulated by hydraulic fracturing. Better production areas within the tight reservoir beds are referred to as sweet spots that are commonly caused by natural fractures, which should be understood and identified to enhance the recovery of the gas from tight reservoirs. The exploration and production techniques allow the commercial production of tight gas, one of environmentally friendly resources. Slant and horizontal wells have best production when they intersect the fractures. Gas production from the tight reservoirs has rapidly grown in U.S. and Canada. Indeed, the U.S. gas production of tight sandstones increases from 11.1% in 1990 to 24.1% in 2005. The presence of tight gas reservoirs has been suggested on the Korean offshore block 6-1. Paradigm shift from conventional to unconventional tight reservoir is required to develop the tight gas from the block.

• Journal of the Korean Solar Energy Society
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• v.36 no.1
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• pp.63-73
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• 2016

How effectively a wind farm captures high market prices can greatly influence a wind farm's viability. This research identifies and creates an understanding of the effects that result in various capture prices (average revenue earned per unit of generation) that can be seen among different wind farms, in the current and future competitive SMP (System Marginal Price) market in South Korea. Through the use of a neural network to simulate changes in SMP caused by increased renewables, based on the Korea Institute of Energy Research's extensive wind resource database for South Korea, the variances in current and future capture prices are modelled and analyzed for both onshore and offshore wind power generation. Simulation results shows a spread in capture price of 5.5% for the year 2035 that depends on both a locations wind characteristics and the generations' correlation with other wind power generation. Wind characteristics include the generations' correlation with SMP price, diurnal profile shape, and capacity factor. The wind revenue cannibalization effect reduces the capture price obtained by wind power generation that is located close to a substantial amount of other wind power generation. In onshore locations wind characteristics can differ significantly/ Hence it is recommended that possible wind development sites have suitable diurnal profiles that effectively capture high SMP prices. Also, as increasing wind power capacity becomes installed in South Korea, it is recommended that wind power generation be located in regions far from the expected wind power generation 'hotspots' in the future. Hence, a suitable site along the east mountain ridges of South Korea is predicted to be extremely effective in attaining high SMP capture prices. Attention to these factors will increase the revenues obtained by wind power generation in a competitive electricity market.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.956-964
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• 2017

This study contributes to deepening understand of the characteristics of fishing vessel rolling motions to improve the development of capsizing alarm systems. A time domain rolling motion simulation was performed. In order to verify capsizing alarm systems, it is necessary to carry out experiments assuming a capsizing situation and perform actual fishing vessel measurements, but these tasks are impossible due to the danger of such a situation. However, in many capsizing accidents, a close connection with rolling motion was found. Accordingly, the rolling motion of a fishing boat, which is the core of a fishing vessel capsizing alarm system, has been accurately measured and a time domain based on a rolling motion simulation has been performed. This information was used to verify the algorithm for a capsizing alarm system. Firstly, the characteristics of rolling motion were measured through a motion experiment. For small vessels such as fishing vessels, it was difficult to interpret viscosity due to analytical methods including CFD and potential codes. Therefore, an experiment was carried out focusing on rolling motion and a rolling mode RAO was derived.

• Journal of Korea Port Economic Association
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• v.35 no.2
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• pp.77-92
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• 2019

As China's economic growth pole has shifted from the coastal area to the Midwest and the inland since the beginning of 2000, construction of China's inland ports was promoted in the coastal area. The inland port functions as offshore port, thereby streamlining import and export logistics and customs clearance and so on. The purpose of this study is to identify the competitiveness and potential of China's inland ports via functional and geographical classification, as well as SWOT-PEST analysis. According to the results of the study, inland ports can be functionally categorized as sea port-based, industrial-based, distribution-based and customs clearance-based. The majority of the sea port-based inland ports are located in the eastern part of China while industry-based and distribution-based inland ports are situated in the Midwest. On contrast, the inland ports in Northwest mainly perform the function of customs clearance to promote international trade with neighbouring countries. The inland ports in the eastern region have high competitiveness owing to a large volume of international trade in the region, whereas those in the Midwest have high potential. The 'One Belt to One Road' initiative proposed by the Xi's Government is expected to play a significant role in promoting the development of inland ports in the Midwest and border areas.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.3
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• pp.122-130
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• 2021

A wind-speed estimation at the arbitrary elevations is key component for the design of the offshore wind energy structures and the computation of the wind-wave generation. However, the wind-speed estimation of the target elevation has been carried out by using the typical functions and their typical parameters, e.g., power and logarithmic functions because the available wind speed data is limited to the specific elevation, such as 2~3m, 10 m, and so on. In this study, the parameters of the vertical profile functions are estimated with optimal and analyzed the parameter ranges using the HeMOSU-1 platform wind data monitored at the eight different locations. The results show that the mean value of the exponent of the power function is 0.1, which is significantly lower than the typically recommended value, 0.14. The values of the exponent, the friction velocity, and the roughness parameters are in the ranges 0.0~0.3, 0~10 (m/s), and 0.0~1.0 (m), respectively. The parameter ranges differ from the typical ranges because the atmospheric stability condition is assumed as the neutral condition. To improve the estimation accuracy, the atmospheric condition should be considered, and a more general (non-linear) vertical profile functions should be introduced to fit the diverse profile patterns and parameters.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.553-560
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• 2020

This paper presents an algorithm for identifying and eliminating errors by seagrasses in coastal bathymetry surveying using drone and HD camera. Survey errors due to seagrasses were identified, segmentated and eliminated using a L∗a∗b color space model. Bathymetry survey using a drone and HD camera has many advantages over conventional survey methods such as ship-board acoustic sounder or manual level survey which are time consuming and expensive. However, errors caused by sea bed reflectance due to seagrasses habitat hamper the development of new surveying tool. Seagrasses are the flowering plants which start to grow in November and flourish to maximum density until April in Korea. We developed a new algorithm for identifying seagrasses habitat locations and eliminating errors due to seagrasses to get the accurate depth survey data. We tested our algorithm at Wolpo beach. Bathymetry survey data which were obtained using a drone with HD camera and calibrated to eliminate errors due to seagrasses, were compared with depth survey data obtained using ship-board multi-beam acoustic sounder. The abnormal bathymetry data which are defined as the excess of 1.5 times of a standard deviation of random errors, are composed of 8.6% of the test site of area of 200 m by 300 m. By applying the developed algorithm, 92% of abnnormal bathymetry data were successfully eliminated and 33% of RMS errors were reduced.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.2
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• pp.193-201
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• 2021

The welding has a high proportion of the production and drying of ships or offshore plants. Non-destructive testing is carried out to verify the quality of welds in Korea, radiography test (RT) is mainly used. Currently, most shipyards adopt analog-type techniques to print the films through the shoot of welding parts. Therefore, the time required from radiography test to pass or fail judgment is long and complex, and is being manually carried out by qualified inspectors. To improve this problem, this paper covers a platform for scanning and digitalizing RT films occurring in shipyards with high resolution, accumulating them in management servers, and applying artificial intelligence (AI) technology to detect welding defects. To do this, we describe the process of designing and developing RT film scanning equipment, welding inspection information integrated management platform, fault reading algorithms, visualization software, and testing and verification of each developed element in conjunction.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.414-421
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• 2022

Subsea oil and gas exploration is increasingly moving into deeper water depths, and typically, subsea pipelines operate under high pressure and temperature conditions. Owing to the difference in these components, the axial force in the pipe is accumulated. When a pipeline is operated at a high internal pressure and temperature, it will attempt to expand and contract for differential temperature changes. Typically, the line is not free to move because of the plane strain constraints in the longitudinal direction and soil friction effects. For a positive differential temperature, it will be subjected to an axial compressive load, and when this load reaches a certain critical value, the pipe may experience vertical (upheaval buckling) or lateral (snaking buckling) movements that can jeopardize the structural integrity of the pipeline. In these circumstances, the pipeline behavior should be evaluated to ensure the pipeline structural integrity during operation in those demanding loading conditions. Performing this analysis, the correct mitigation measures for thermal buckling can be considered either by accepting bar buckling but preventing the development of excessive bending moment or by preventing any occurrence of bending.

• Journal of the Korean Geotechnical Society
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• v.25 no.2
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• pp.45-54
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• 2009

The electrical characteristics of soils have been used for investigating soil properties. The purpose of this study is the development and application of the electrical resistivity cone probe (ERCP) for the evelation of the porosity in the field with high precision. The shape of the probe tip is a cone shape to minimize the disturbance during penetration. In addition, the four terminal pair configuration is adopted to minimize the electrical interference. The electrical resistances are continuously measured during penetration of the ERCP using penetration rigs with 0.33 mm/sec penetration rate at Incheon and Busan sites. With the measured resistance profile and electrical resisivity of electrolyte of undisturbed samples, soil porosity profiles are obtained by using Archie's law. The empirical coefficients for the Archie's law are obtained based on the electrolyte extracted from the undisturbed samples. The estimated porosity profiles show similar trends to those of in-situ penetration tests such as SPT, CPT, and DMT. This study suggests that the ERCP may be an effective tool for the porosity estimation in the field with minimum disturbance.