• Journal of the Korean Society of Marine Environment & Safety
• /
• v.26 no.5
• /
• pp.551-560
• /
• 2020

Recently, the offshore wind power generator market is expected to grow significantly because of increased energy demand, reduced dependence on fossil fuel-based power generation, and environmental regulations. Consequently, wind power generation is increasing worldwide, and several attempts have been made to utilize offshore wind power. Norway's Petroleum Safety Authority (PSA) requires a leg-structure design with a collision energy of 35 MJ owing to the event of a collision under operation conditions. In this study, the results of the numerical analysis of a wind turbine installation vessel subjected to ship collision were set such that the maximum collision energy that the leg could sustain was calculated and compared with the PSA requirements. The current leg design plan does not satisfy the required value of 35 MJ, and it is necessary to increase the section modulus by more than 200 % to satisfy the regulations, which is unfeasible in realistic leg design. Therefore, a collision energy standard based on a reasonable collision scenario should be established.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.3
• /
• pp.14-21
• /
• 2017

The extreme floods recently are have been attributed global warming, The development of a canal tunnel to prevent floods by making a bypass or undercurrent to flood discharge in a major flooding area is required because urban flooding in heavy rainfall occurs frequently, increasing the impermeability according to lack of capacity in sewage to urbanization by the existing urban basin. In this study, a numerical simulation was performed to support design standards for a multi-purpose waterway tunnel combined road tunnel of canal tunnel. The numerical simulation showed that the size of the friction loss occurring in the tunnel section of the same channel occurred more than the theoretically calculated frictional loss derived from the numerical simulations. This is probably due to the additional frictional loss caused by the change in the flow structure due to the geometry of the pipe when the shape of the channel is non-circular. The increase in friction loss was more pronounced in the laminar flow than in the turbulent flow. Depending on the shape of the conduit, the friction loss should be adjusted for accurate flow calculations. This result can provide the basin information about the design of flood by a pass conduit.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.2
• /
• pp.174-190
• /
• 1996

Damage assessment based on in situ surveys for oil spills in marine environment is limited by fundamental difficulties as well as tremendous expenses. Except for intertidal zones, the damage is not preserved well. Also such surveys are usually confined to adult organisms. To overcome these limitations a computer model, NRDAM/CME, was developed in the case of USA (Reed et al., 1989), where an acute toxicity data base was used to assess indirect damages through food webs and loss due to recruitment as well as adult losses. In the present study damage assessment of natural biological resources for hypothetical oil spills is attempted using a computer model for hypothetical spills of Bunker C and heavy crude oil. In the model, the logical structure of NRDAM/CME was adopted, and biomass and productivity database were compiled for the Korean waters. The results showed that the damage increased in a nonlinear fashion as the spill amount increased. The magnitude of the damage depended upon the chemical properties of oil viscosity and solubility in particular, which implies that usage of oil dispersant might increase the damage by dispersing oil. The results also indicate that long term damage due to recruitment loss could be greater than short term damage.

• Journal of the Korean earth science society
• /
• v.34 no.1
• /
• pp.13-27
• /
• 2013

Quantitative precipitation estimation (QPE) is one of the most important elements in meteorological and hydrological applications. In this study, we adjusted the QPE from an S-band weather radar based on co-kriging method using the geostatistical structure function of error distribution of radar rainrate. In order to estimate the accurate quantitative precipitation, the error of radar rainrate which is a primary variable of co-kriging was determined by the difference of rain rates from rain gauge and radar. Also, the gauge rainfield, a secondary variable of co-kriging is derived from the ordinary kriging based on raingauge network. The error distribution of radar rain rate was produced by co-kriging with the derived theoretical variogram determined by experimental variogram. The error of radar rain rate was then applied to the radar estimated precipitation field. Locally heavy rainfall case during 6-7 July 2009 is chosen to verify this study. Correlation between adjusted one-hour radar rainfall accumulation and rain gauge rainfall accumulation improved from 0.55 to 0.84 when compared to prior adjustment of radar error with the adjustment of root mean square error from 7.45 to 3.93 mm.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.4
• /
• pp.307-313
• /
• 2016

When liquefied natural gas (LNG) is stored in a tank, it is necessary to maintain low temperature. It is very important that insulation techniques are applied to the LNG cargo because of this extreme environment. Hence, laminated wood, especially plywood, is widely used as the structural member and insulation material in LNG cargo containment systems (CCS). However, fracture of plywood has been reported recently, owing to sloshing effect. Therefore, it is necessary to increase the strength of the structural member for solving the problem. In this study, compressed wood, which is used as a support in LNG independent type B tanks, was considered as a substitute for plywood. Compression and bending tests were performed on compressed wood under ambient and cryogenic temperatures to estimate the mechanical behaviors and fracture characteristics. In addition, the direction normal to the laminates surface was considered as an experimental variable. Finally, the feasibility of using compressed wood for an LNG CCS was evaluated from the test results.

• Geophysics and Geophysical Exploration
• /
• v.11 no.1
• /
• pp.68-77
• /
• 2008

We have developed an inversion algorithm for loop-loop electromagnetic (EM) data, based on the localised non-linear or extended Born approximation to the solution of the 2.5D integral equation describing an EM scattering problem. Source and receiver configuration may be horizontal co-planar (HCP) or vertical co-planar (VCP). Both multi-frequency and multi-separation data can be incorporated. Our inversion code runs on a PC platform without heavy computational load. For the sake of stable and high-resolution performance of the inversion, we implemented an algorithm determining an optimum spatially varying Lagrangian multiplier as a function of sensitivity distribution, through parameter resolution matrix and Backus-Gilbert spread function analysis. Considering that the different source-receiver orientation characteristics cause inconsistent sensitivities to the resistivity structure in simultaneous inversion of HCP and VCP data, which affects the stability and resolution of the inversion result, we adapted a weighting scheme based on the variances of misfits between the measured and calculated datasets. The accuracy of the modelling code that we have developed has been proven over the frequency, conductivity, and geometric ranges typically used in a loop-loop EM system through comparison with 2.5D finite-element modelling results. We first applied the inversion to synthetic data, from a model with resistive as well as conductive inhomogeneities embedded in a homogeneous half-space, to validate its performance. Applying the inversion to field data and comparing the result with that of dc resistivity data, we conclude that the newly developed algorithm provides a reasonable image of the subsurface.

• The Journal of Engineering Geology
• /
• v.17 no.2 s.52
• /
• pp.205-215
• /
• 2007

In this study, the soil characteristics are analyzed using the result of various soil tests as an object of the soil layer of natural slopes in landslides areas. Also, the relationship with landslides and interrelation with each soil properties are analyzed. The landslides in three areas with different geological condition are occurred due to heavy rainfall in same time. The geology of Jangheung area, Sangju area and Pohang area is gneiss, granite, and the tertiary sedimentary rock, respectively. However soil characteristics have a little differentiation to geological condition, the soils sampled from landslide area have higher proportion of fine particle and porosity, and lower density than those from non landslide area. In case of same geological condition, landslides are occurred in the terrain slope with high permeability. The permeability is mainly influenced by the soil characteristics such as particle size distribution, porosity, particle structure, and the geological origins such as weathering, sedimentary environment. The soil layer with high internal friction angle is more stable than that with low internal friction angle in all geological condition. The permeability is mainly influenced by effective particle size, coefficient of uniformity, coefficient of gradation, porosity, density and so on. Also, those have interrelation with each factor. These interrelations are similar in all study area. Meanwhile, in proportion as the void ratio and the porosity rises the permeability increases.

• Child Health Nursing Research
• /
• v.7 no.4
• /
• pp.421-433
• /
• 2001

The purpose of this phenomenological study was to understand the lived experience of mothers of children with muscular dystrophy. The participants were 11 mothers recruited by snowball sampling, who agreed with the objectives of the research and could verbally communicate with the researcher and who lived with their sons who had muscular dystrophy. Data collection was done through in-depth interviews with participants in their own homes. Each interview took 50 to 120 minutes. All of the interviews were audiotaped and then transcribed. Data were analyzed using Colaizzi's (1978) method of phenomenology. From the transcripts 109 significant sentences and phrases were selected and 13 clusters of themes were categorized from 67 significant statements. These results were integrated into the essential structure of the lived experience of mothers of children with muscular dystrophy. 1. Anxious and relying on chance due to indefinite diagnosis. 2. Only able to cry with shock because of son's fatal disease. 3. Seeing the future as dismal and feeling resentment that this disease in transmitted through the mother. 4. Feeling caught between a husband who is distancing himself from his family and the family which is disintegrating. 5. Feeling like a sinner for transmission of genetic disease(Feeling guilt for conceiving a son with a genetically transmitted fatal disease). 6. Empathizing with other suffers of muscular dystropy and their parents in their grief and helping to dissipate their heavy feelings. 7. Deciding to sacrifice self as a way of taking responsibility for giving birth to a handi-capped son. 8. Losing hope (feeling despair) as son's condition deteriorates in spite of all attempts to help him. 9. Wishing to die with son who becomes progressively immobile. 10. Accumulating Han*(한, 恨), because of rising Hwa(화, anger), and becoming sick both mentally and physically. 11. Seeing events as destiny and finding self-control through faith. 12. Finally, giving up sacrificing self for son and becoming concerned(involved) with other children in the family. 13. Feeling fear at son's impending death. This is the first research on the experience of Korean mothers of children with muscular dystrophy. In applying the phenomenology research method, this study not only helps health professionals understand the experience of these mothers in the Korean patriarchal social system, but the researcher, as a nurse, can share their agony and grief through identification of their inner world through in-depth personal interviews. The results obtained in this study will not only help in the development of family nursing practice for families with genetically transmitted diseases but also prepare basic data for family nursing practice in the Korean sociocultural context.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.22 no.5
• /
• pp.529-541
• /
• 2020

Although TBM's cutterhead requires design review for fatigue failure due to wear-induced section loss as well as heavy load during excavation, it is difficult to find a case of fatigue analysis for TBM cutterhead at present. In this study, a stress-life design review was conducted on cutter heads with a diameter of 8.2 m using S-N curves as a safety life design concept. Also, we introduced the fatigue design method of construction equipment and the method of assessing fatigue damage and explained the results of the fatigue analysis on the TBM cutter head with a diameter of 8.2 m. The S-N curve has been shown to play a key role in fatigue design and can also be used to assess how much fatigue damage a structure is suffering from at this point in time. In the future, it is necessary to find out when fatigue problems occur during using the equipment and when it is good to conduct safety inspections of the equipment.

• Journal of Navigation and Port Research
• /
• v.33 no.8
• /
• pp.563-572
• /
• 2009

The steel industry, as the national representative strategic industry of our country, has played the motive power for the economic growth of Korea in 1970s as the positive support of the government and the management endeavor of the private were harmonized. However, in case of our country, we have mostly relied on import of the raw materials for the steel industry, and as the weight of the imported raw materials is heavy, the steel industry is the industry whose transport burden is big as it is called 'transport industry'. So, the transport rationalization will be the important task of the steel industry. This study has analyzed the economic efficiency per the transport route (container ship vs bulk ship) of the sea transport related to import/export of the steel scrap on the level acquiring the stable supply of the steel scrap. For this, this study firstly researched the status of domestic/foreign steel industry. And analyzed the world crude steel production volume, steel scrap consumption volume and world steel scrap trading structure. Also, in order to compare the transport logistics expenses between two transport devices, namely, container ship and bulk ship, this study calculated the logistics expenses per ton by using the traffic hours and traffic expenses items as the imported/exported scrap freights of 'D' company.