• Ocean Systems Engineering
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• v.14 no.3
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• pp.277-299
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• 2024

In this study, the wave-induced motion responses of modular floating structures (MFS) was investigated through a series of experiments in a two-dimensional wave tank. A 1:63 scale model test was conducted using a 1-by-2 modular floating structure consisting of two modules and connectors. Two different types of connectors were considered: a pitch-free hinge and rigid connector. The numerical analysis was performed based on the higher-order boundary element method (HOBEM) and wave Green function with potential flow theory. First, the heave and pitch RAOs of the modules from the regular wave tests were directly compared with numerical analysis results. Next, the motion spectra and their statistical values from the irregular wave tests were compared with the numerical analysis results. The study revealed that the sheltering effect of the weather side module led to a reduction in motion of the lee side module. The numerical analysis showed good agreement with the experimental data, demonstrating the validity of the numerical method. Additionally, the rigid connector, which strongly constrain all six degrees of freedom, significantly reduce pitch motion, making the modules behave as a single rigid body.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.71-76
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• 2017

The roll damping problem in the design of ships and offshore structures remains a challenge to many researchers due to the fluid viscosity and nonlinearity of the phenomenon itself. In this paper, the study on viscous roll damping of a circular cylinder was carried out using forced oscillations. The roll moment generated by forced oscillation using a torque sensor was measured for each forced oscillation period and compared with the empirical formula. Although the magnitude of the measured torque from the shear force was relatively small, the results were qualitatively similar to those obtained from the empirical formula, and showed good agreement with the quantitative results in some oscillation periods. In addition, the flow around the circular cylinder wall was observed closely through the PIV measurements. Owing to the fluid viscosity, a boundary layer was formed near the wall of the circular cylinder, and a minute wave was generated by periodical forced oscillations at the free surface through the PIV measurement. In this study, the suitability of the empirical formula for the roll moment caused by viscous roll damping was verified by model tests. The wave making phenomenon due to the fluid viscosity around the wall of a circular cylinder was testified by PIV measurements.

• Journal of Environmental Health Sciences
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• v.43 no.4
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• pp.247-256
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• 2017

Objectives: The deaths of Korean victims exposed to the disinfectant CMIT/MIT have remained unresolved. This is mainly due to a lack of concordance between the few available toxicity tests and the abundant epidemiological data, making it difficult to establish a cause-and-effect relationship. Therefore, this study was carried out to investigate any potential associations between CMIT/MIT exposure and death. Methods: Groups of experimental and control C57BL/6 mice were instilled (in the trachea) with chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) using a visual instillobot. CMIT/MIT was instilled over a period of three days and eight weeks, respectively, to achieve acute and chronic exposures. A threshold dose-response model was applied for estimating the threshold level as one line of evidence for a causal association between CMIT/MIT and death. Results: An acute exposure of 1.2 mg ai/kg/day of CMIT/MIT was estimated to reflect the threshold for death. The dose-response curve with this threshold showed a very steep slope and a narrow range of CMIT/MIT exposures. The narrow range of CMIT/MIT exposures, in particular, indicated an evident boundary between survival and death, thus implicating a strong causal association. A similar threshold dose-response relationship observed following acute exposure was also seen following chronic exposure to CMIT/MIT. Airborne disinfectant exposure was visible as minimal or mild lung damage with no fibrosis, as shown by histopathological tests. However, many observations are considered to be functional respiratory tract or lung failure due to death, as observed in necropsies of the mice that died due to CMIT/MIT exposures. Conclusions: There are two strong lines of evidence for a causal association between death and CMIT/MIT exposure: 1) The threshold dose-response curve, with a very steep slope and a narrow range of CMIT/MIT exposures showing a visible boundary between survival and death; and 2) many cases of functional respiratory or lung failure.

• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.575-585
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• 1997

A daily runoff system was constructed to support decision making for water use in the downstream region of multipurpose dams in the Han River. The daily runoff system used the modified model from NWSRFS by Tabios III et al. (1986), and potential evapotranspiration was computed from Penman equation. DWOPER was used for channel routing. While the North Han River is the main river reach in the channel routing system, the South Han River and the Soyang River became tributaries. The rainfall-runoff model was calibrated and verified for five subbasins. Daily runoffs were simulated with the hydrometeorological data in 1986 and1990. The simulations were performed from April to November, and the sum of computed discharges for seven or thirty days were compared with actual releases of the downstream dams. It showed the average absolute errors of 8.7 ~31.6%. The sum of total discharges were 10% or less. While stage errors were produced by 0.5 m or less at Yoju station in the ease of simulation from April to August in 1986, the errors kept under 0.2 m since September. In the simulation for 1990, we compared two simulation results. One is produced from real internal and downstream boundary conditions and the other is one from internal and downstream boundary conditions fixed arbitrarily. The two cases showed similar results.

• Journal of Navigation and Port Research
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• v.29 no.10 s.106
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• pp.853-858
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• 2005

Recently, various novel numerical models based on Navier-Stokes equation have been developed for calculating wave motions in the sea with coastal or ocean structures. Among those models, Volume Of Fluid (VOF) method might be the most popular one, and it has been used for numerical simulations of wave motions including complicated phenomena of wave breakings. VOF method, however, needs enormous computation time and large computational storage memories in general, thus it is practically difficult to use this method for calculations in the case of random waves because long and stable computation (e.g for more than 100 significant wave periods) is required to obtain statistically meaningful results. On the other hand if the wave motion is potential motion, Boundary Element Method (BEM), which is a much faster and more accurate method than VOF method, can be effectively used. The aim of this study is to develop a new efficient model applicable to calculations of wave motion and/or wave-structure interactions under random waves. To achieve this, a strictly combined BEM-VOF model has been developed by making the best use of both methods' merits; VOF method is used in a restricted fluid domain around a structure where complicated phenomena of wave breakings may exist, and BEM is used in the other domains far from the disturbance where the wave motion may be assumed to be potential. The verification of the model was performed with numerical results for Stokes' 5th order wave propagation and a random wave propagation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.153-159
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• 2005

Recently, various novel numerical models based on Navier-Stokes equation rave been developed for calculating wave motions in the sea with coastal or ocean structures. Among those models, Volume Of Fluid (VOF) method might be the most popular one, and it has been used for numerical simulations of wave motions including complicated phenomena of wave breakings. VOF method, however, needs enormous computation time and large computational storage memories in general, thus it is practically difficult to use VOF method for calculations in the case of random waves because long and stable computation ( e.g. for more than 100 significant wave periods) is required to obtain statistically meaningful results. On the other hand of the wave motion is potential motion, Boundary Element Method (BEM), which is a much faster and more accurate method than VOF method, am be effectively used. The aim of this study is to develop a new efficient model applicable to calculations of wave motion and/or wave-structure interactions under random waves. To achieve this, a strictly combined BEM-VOF model has been developed by making the best use of both methods' merits; VOF method is used in a restricted fluid domain around a structure where complicated phenomena of wave breakings may exist, and BEM is used in the other domains far from the disturbance where the wave motion may be assumed to be potential. The verification of the model was performed with numerical results for Stokes'5th order wave propagation and a random wave propagation.

• Cartoon and Animation Studies
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• s.36
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• pp.259-280
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• 2014

Animation is showing the highest record in entertainment around the world and writing the history of 3D animation again. The image contents effect thanks to the proper introduction of the state-of-art digital technology, which is one of the causes of the outstanding entertainment and the factual reproduction of the images, provided an opportunity to transmit the meaning of image aesthetics, which is a virtual reality and image reproduction through the reality realization of photo medium, and to reinterpret the boundary of virtual reality. Especially, the development of digital contents technology due to scientific technologies demolishes the boundary of virtual reality and reality and creates the effect of making viewers be absorbed by realizing the virtual reality by means of 3D reality images which highlight the special characteristic of photos. The aspect of the contents technology and image aesthetics which can be interpreted in a view point beyond the existing concept of reality is found in the aura theory of Benjamin and in the Simulacres of Baudrillard. The 3D image by photo-reality herein presents various suggestions in the aspect of real existence of spatial expression, the meaning creation process of reality, the existence value of virtual images.

• Journal of Animal Environmental Science
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• v.14 no.1
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• pp.15-22
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• 2008

This study was carried out to investigate the effect of enzyme complex on odor emission from swine slurry and the process of making swine liquid manure. Ammonia and hydrogen sulfide concentrations were significantly decreased by using the enzyme complex of liter per ton level of liquid swine slurry in the manure storage tank according to the time. Characteristics of liquid swine slurry were affected by the enzyme complex, total nitrogen and ammonia nitrogen contents were reduced compare with control. Ammonia and hydrogen sulfide concentrations in the finishing pig building and offensive odor compound on the boundary line of swine farm were significantly decreased by spraying in swine finishing building. In conclusion, the results obtained from this study suggest that using the enzyme complex of liter per ton level of liquid swine slurry for making liquid swine manure may improve the quality of swine liquid fertilizer and reduce odor emission. Also farm scale enzyme complex treatment may improve air quality in finishing pig building and deduce offensive odor compound of swine farm.

• Journal of the Korean Geographical Society
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• v.51 no.6
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• pp.799-817
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• 2016

This article aims to reveal the ways in which a "space of difference" is produced and interpret the space as a heterotopic space, drawing the case of Filipino elderly care-givers in Israel. The in-betweens and temporariness of the migrants'experiences in the Israeli society lead to the creation of a heterotopic space. Paying attention to their particular life rhythm as live-in care-givers, namely weekdays-workplace and weekend-flat, this article explores how the migrant care-givers build their own society through a variety of spatial practices and multiple social relations based on the flat. In making the flat a perfect form of a lifestyle for their own, the migrants inscribe their presence in the flat in unique ways for different purposes, in a way different to that which surrounds it. However, the structure of flat not only signifies the migrants' marginality but also reflects the challenging position. The flat has functions in relation to all other space that remains, even if such connection often creates effects of contrast and difference. In this light, the flat is not merely an alienated and circumscibed exotic migrant enclave but a heterotopic space which is dynamically constructed in relation to other sites in the wider societal order.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.501-506
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• 2004

Korean cadastral system is primarily based on the graphical maps, thus, map reproduction by excessive shrinkage or extension, map mishandling and imperfection of surveying techniques have created cadastral non-coincident areas, which caused public distrust as well as considerable difficulties in land administration and policy making. Therefore, in this study, the methodologies for the resolution of the non-coincident problem are presented by means of a comparative analysis between cases of the non-coincident areas. The non-coincidence caused by the mismatch of parcel boundaries can be settled by introducing a coordinate-based system, namely $\ulcorner$Integrated Land Information System$\lrcorner$, meanwhile, those by other reasons can be done by establishing and executing a plan that can deliver the unification of the cadastral and the land registration systems. Governmental intention and budgetary measures for securing the project expenses are essential to make this feasible. If the comprehensive improvement project is completed, the cadastral registers that define the parcel boundary, area and ownership will recover public confidence, which in turn secures land owners' rights by promoting land markets and stabilizing land prices.