• Computational Structural Engineering
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• v.9 no.3
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• pp.125-134
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• 1996

The base-isolation of building, as appeared in many studies, has shown remarkable performance in seismic response attenuation of the internal system as well as the building structure itself. But for the case that the internal system is submerged and hence subject to a considerable hydrodynamic effect, the seismic response of the system due to the base-isolation of building can be greater than the case that they are in air. This paper presents the dynamic analysis of a submerged internal system on base-isolated building to show such an example. The results show that an additional treatment is required to reduce the adverse effects on the seismic response of such a system when the building is base-isolated, and that the system response can be reduced to some extent by an appropriate control of fluid gap between the system and the building structure.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.2
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• pp.148-153
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• 2014

Submerged bodies such as autonomous underwater vehicles (AUV) or remotely operated vehicles (ROV) are widely used in various fields of exploring underseas. Those bodies keep ballasting and deballasting for stable navigation and operation. Identifying the internal volumetric spaces of the bodies is a primary step for such an operation. Unfortunately, most CAD models given to the engineer do not properly represent the compartments since each face of a compartment exists as an independent entity rather than as a face that belongs to the compartment. In this paper, an algorithm that automatically identify the faces as a group that forms a closed volumetric space, i.e., a compartment is presented. A submerged body is sliced into a number of cross sections. Each sliced section is analyzed to yield closed loops that are sections of the compartment. Then, the associated closed loops are gathered along the longitudinal direction to form a compartment. The algorithm presented is shown to provide a practical and reasonable solution that can readily be used in various applications.

• International journal of steel structures
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• v.18 no.4
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• pp.1191-1199
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• 2018

Concepts of submerged floating tunnels (SFTs) for land connection have been continuously suggested and developed by several researchers and institutes. To maintain their predefined positions under various dynamic environmental loading conditions, the submerged floating tunnels should be effectively moored by reasonable mooring systems. With rational mooring systems, the design of SFTs should be confirmed to satisfy the structural safety, fatigue, and operability design criteria related to tunnel motion, internal forces, structural stresses, and the fatigue life of the main structural members. This paper presents a feasibility study of a submerged floating tunnel moored by an inclined tendon system. The basic structural concept was developed based on the concept of conventional cable-stayed bridges to minimize the seabed excavation, penetration, and anchoring work by applying tower-inclined tendon systems instead of conventional tendons with individual seabed anchors. To evaluate the structural performance of the new type of SFT, a hydrodynamic analysis was performed in the time domain using the commercial nonlinear finite element code ABAQUS-AQUA. For the main dynamic environmental loading condition, an irregular wave load was examined. A JONSWAP wave spectrum was used to generate a time-series wave-induced hydrodynamic load considering the specific significant wave height and peak period for predetermined wave conditions. By performing a time-domain hydrodynamic analysis on the submerged floating structure under irregular waves, the motional characteristics, structural stresses, and fatigue damage of the floating tunnel and mooring members were analyzed to evaluate the structural safety and fatigue performance. According to the analytical study, the suggested conceptual model for SFTs shows very good hydrodynamic structural performance. It can be concluded that the concept can be considered as a reasonable structural type of SFT.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.120-124
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• 2009

This study was performed to investigate the application of submerged membrane bioreactor (MBR) system for biological nutrient removal of municipal wastewater. MBR bioreactor consists of four reactors such as anaerobic, stabilization, anoxic and submerged membrane aerobic reactors with two internal recycles. The hydraulic retention time (HRT), sludge retention time (SRT) and flux were 6.2 hr, 34.1 days and $19.6L/m^2/hr$ (LMH), respectively. As a result of operation, the removal efficiency of $COD_{Cr}$, SS, TN and TP were 94.3%, 99.9%, 69.4%, and 74.6%, respectively. There was no significant effect of microbial activity after the maintenance cleaning using 200 mg/L of NaOCl. Membrane filtration for the treatment of municipal wastewater was performed for longer than 9 months without chemical recovery cleaning.

• Journal of the Korean Society for Railway
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• v.17 no.2
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• pp.100-105
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• 2014

To design a submerged floating railway that is safe against underwater explosions, railway behavior must be investigated and clarified. In this paper, shock waves and impulse pressures generated by a charge away from the submerged floating railway are expressed using experimental formulas. The submerged floating railway tethered by mooring lines is modeled as a simply supported beam with elastic springs. Finite element analysis for the beam model subjected to impulse loading is conducted so that the response of the submerged floating railway can be investigated. For design purposes, a simplified analysis method combined with dynamic load factor is proposed for the same model. Maximum deformation and internal forces are calculated and compared with the time dependent analysis results. It is shown that the simplified analysis results show good agreement.

• Journal of Navigation and Port Research
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• v.43 no.5
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• pp.328-334
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• 2019

Underwater architecture in providing a comfortable living space underwater is mandated to survive prevailing environmental loads, especially hydrostatic ambient water pressure exerted on the structure of individual habitat hulls at depth and hydrodynamic fluctuation of external forces that perturb the postural equilibrium and mooring stability of the underwater housing system, for which the design including the hull shape and mooring system constraint the responses. In this study, the postural stability of a proposed underwater floating housing system with three vertically connected ellipsoidal-shape habitat hulls of different sizes are theorized and calculated for hydrostatic stability, using MATLAB in the volumetric integration of a hull and the weight of operational loads under assumed scenarios. The assumptions made in the numerical method to estimate the stability of the habitat system include the fixed weight of the hulls, and their adjustable loads within operational limits for the set meteorological oceanic conditions. The purpose of this study was to numerically manipulate a) The buoyancy and b) The adjusted center of mass of the system within the range of designed external and internal load changes, by which the effective mooring system capability and postural equilibrium requirements were argued with the quantitative analysis.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.2
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• pp.289-294
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• 2006

A pilot scale non-woven fabric filter separation activated sludge system was investigated for practical application on domestic wastewater reclamation and reuse. The system was operated in A/O (Anaerobic/Oxic) process with submerged filter module in the aerobic compartment. In the test of two types of filter materials ($70g/m^2$ and $35g/m^2$), the initial flux (0.42m/d) could be maintained for about three months by regular air backwashing of $70g/m^2$ filter at 0.3m water head. The removal efficiency of organic matter by the system was BOD 93.3%, CODcr 96.3%, SS 96.7%. The effluent quality was 7.8mg/L, 12mg/L and 5mg/L for BOD, CODcr and SS, respectively. The water quality was enough to meet a standard for domestic reuse without human contact. T-N removal efficiency was 49.9% at internal recycle rate 2Q and C/N ratio 3.3. The removal efficiency of T-P was 50% with average effluent concentration, 2.6mg/L.

• Journal of Power System Engineering
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• v.8 no.3
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• pp.30-35
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• 2004

In the steel making industries, the continuous casting process has been applied to the number of company because of its economical benefit. Casting rolls are utilized for frictional drive and transport of solidifying slap. Dimensional tolerances, mechanical stability and surface condition of the cast roll can affect both the surface and internal quality of the product being cast. To overcome these problems, the industry is accelerating on the rate of technology improvements. Samples were overlaid on the S45C steel by submerged arc welding process. And the hardness, wear, electrochemical corrosion and oxidation tests were carried out. Test results were that all these materials were satisfying basic requirements of caster rolls. By these results, the addition of 0.1%Nb and 0.15%V increase mechanical properties and tempering resistance by its superior carbide forming characteristics in low carbon $12{\sim}13%Cr$ martensitic stainless steels.

• Journal of Korean Society on Water Environment
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• v.21 no.6
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• pp.602-608
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• 2005

A laboratory-scale experiment was conducted to investigate control of soluble microbial products (SMP) by the internal recycle rate in the submerged membrane separation activated sludge process. The internal recycle rate of the reactor RUN 1 and RUN 2 were 100 % and 200 %, respectively. SMP concentration was rapidly accumulated in the reactor (RUN 1). The variation of accumulated SMP concentration was related to the denitrification rate at the beginning experiment however SMP concentration decreased without correlatively to the denitrification rate during long operation time. The microbial kinetic model was rapidly presented in the both microbial growth and extinction in the reactor (RUN 1). In the SMP kinetic model, Internal recycle rate is the lower, value of UAP and BAP which SMP matter were presented low. The study about development of kinetic model is relatively well adjusted to the experiment exception SMP. In the future, SMP formation equation must be thought that continually research is necessary.

• Environmental Engineering Research
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• v.14 no.3
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• pp.174-179
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• 2009

The InSub system(applied for a patent) was developed, as it combined the indirectly aerated submerged biofiltration(InSub) reactor and Anaerobic/ Anoxic reactor. This system which can eliminate organism and nutrient materials at the same time, which is safe and economical to be maintained and managed is more simple process than the complicated existing biological advanced sewage treatment system. The most suitable HRT of this study showed 9 hours. As looking into the effluent concentration and removal efficiency of each item at 9 hours of HRT, each effluent concentration for $SS,\;BOD5,\;COD_{Mn},\;and\;COD_{Cr}$ was 1.46 mg/L, 7,09 mg/L, 9.84 mg/L and 16.42 mg/L. And their removal efficiency was 96.98%. 90.59%, 77.18% and 83.92%, respectively. Each effluent concentration of T-N and T-P was 10.42 mg/L and 1.04 mg/L. Their removal efficiency was 73.38% and 61.62%, respectively. This pilot plant experiment(the state was without the internal recycling.) followed a variety of HRT. The results confirmed that it was to be advanced sewage treatment system with high efficiency when it combined with the internal recycling.