• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.93-98
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• 2008

We investigated the effect on the removal of BOD, SS, TN and TP and algal growth inhibition of Vegetated Artificial Floating Island (VAFI), by examining microorganism activity and nutrient uptake in the batch test of various conditions: (1) Blank (Control group), (2) VAFI of $0.25m^2$, (3) AFI of $0.25m^2$ which has no vegetation, (4) buoyant plate of $0.25m^2$, (5) buoyant plate of $0.25m^2$ with linear media. The proportion of BOD removal in the VAFI, AFI, buoyant plate and buoyant plate with media were 82.7, 80.8, 45.2% and 59.6% respectively. TN removal in the VAFI, AFI and buoyant plate with media were 51.2, 31.7% and 25.1% respectively. TP removal in the VAFI, AFI, buoyant plate and buoyant plate with media were 23.3, 16.7, 10.0% and 13.3% respectively. Chlorophyll-${\alpha}$ removal in the VAFI was 97.9%. The factors of chlorophyll-${\alpha}$ removal in the VAFI accounted for the shading effect of 35.1%, microorganisms activity of 61%, and plant root of 1.8%.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.3
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• pp.350-357
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• 2012

The velocity response of stiffened rectangular plate under high velocity impact was studied. Numerical simulation was conducted on the stiffened plate with four stiffeners under various impact positions. Considered stiffener types were rib, I, hat and T stiffener. For the center impact position of I stiffened plate, the simulated residual velocity was 365.6 m/s with the initial projectile velocity 500 m/s. The reinforcing characteristic of I stiffened plate was excellent among four stiffeners.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.470-472
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• 1996

POSCO has a plan for facility expansion in plate mill by building No.3 Plate Mill. By No.3 Plate Mill's coming on line, POSCO' current plate production of 2.3 million tons will increase by over 1 million tons to 3.36 million tons (Currently, annual domestic demand for plates is 4.42 million tons). With the plan of facility expansion, POSCO also has the plan of integrating the Plate Warehouse. But, we came to have a question whether the roller table from the mill to the warehouse could carry extended products. Engineers working in the mill wanted to install transfer facility to reduce the load of the roller table, but the engineers in facility purchasing team didn't want to buy the new facility. So, We needed to analyzed the material flow by simulation. The simulation was done on the VAX system by SLAM II. And this project was done by two engineers for 2 months. In the end, we concluded that two transfer facilities are needed for material flow with no bottle neck point.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.749-756
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• 2006

Because of the orthotropic elastic properties and significant two-way bending action, orthotropic plate theory may be suitable for describing the behavior of concrete filled grid bridge decks. Current AASHTO LRFD Bridge Design Specification(2004) has live load moment equations considering flexural rigidity ratio between longitudinal and transverse direction, but the Korea highway bridge design specification(2005) doesn't. The Korea highway bridge standard specification LRFD(1996) considers an orthotropic plate model with a single load to estimate live load moments in concrete filled grid bridge decks, which may not be conservative. This paper presents live load moment equations for truck and passenger car, based on orthotropic plate theory. The equations of truck model use multiple presence factor, impact factor, design truck and design tandem of the Korea highway bridge standard specification LRFD(1996). The estimated moments are verified through finite-element analyses.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1415-1422
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• 2011

Sheet aluminum alloys used in manufacturing of machine structures for transportation show the difference of crack growth speed depending on thickness under the constant fatigue stress condition. The referred thickness effect is a major fatigue failure property of sheet aluminum alloys. In this work, we identified the thickness effect in fatigue test of thick plate and thin plate of Al 2024-T3 alloy under the constant fatigue stress condition, and presented the thickness effect to a correlative equation, $U_{i}^{equ}=f(R_t)$ which is determined by the shape factor, thickness ratio, $R_t$ and the loading factor, equivalent effective stress intensity ratio depending on thickness, $U_{i}^{equ}$. And we analyzed quantitatively the crack growth retardation behavior in thin plate compared to thick plate by the thickness effect using ${\Delta}K$ conversion method. We obtained such values as decrement of thickness(DoT), decrement of stress intensity factor range, ${\Delta}K$ (DoS) and identified the relation between them to present the nature of thickness effect in this work.

• Journal of Environmental Health Sciences
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• v.29 no.1
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• pp.28-33
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• 2003

This study was carried out to treat sewage using sand trench combined with septic tank process in rural areas. In order to find optimum parameters, design and operation mode was changed from Run 1 to Run 4. In order to facilitate nitrification and T-P removal, diffuser and iron plate was installed in the 3rd trench of Run 2 period. The septic tank played a role as pre-application process of sand trench system. The removal efficiencies of COD, NH$_4$-N, T-P at steady state were 94.6%, 87.9% and 54.5%, respectively. Addition of diffuser and iron plate in the 3rd trench has increased the removal efficiencies of the NIL-N and T-P. In this system, denitrification were not occurred because of the high DO.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.977-982
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• 2000

As a newly structural system, RCS composite system has been researched last two decades. However mechanism of exterior T-type joint for RCS composite system is not well known. This research is focus on the exterior T-type joint for RCS composite system. Specimens are designed by the ASCE guideline, tested and compared with the inner RCS joint. Test variables include face bearing plate(FBP), extended face bearing plate(E-FBP) and U-bar. The tests indicate that the strength of exterior T-type joint is higher than that of the guideline by ASCE. The U-bar has a significant effect on the joint strength and absorbing the strain energy.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.5
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• pp.709-718
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• 2010

This paper deals with two contents: first, distributions of plate slenderness ratios, stiffened plate slenderness ratios, and stiffener slenderness ratios, which include dimensions and material variables of stiffened plates, of stiffened plates of large-sized in-service vessels, and, second, comparison of compressive strengths. The investigated vessels consist of 59 tankers, 49 bulkers, 28 product carriers, 15 container carriers, and 12 multi-purpose vessels. The tankers are ranged from handymax class to VLCC and larger than Suezmax class. The sizes of the bulkers are 20K to 200K deadweight. The maximum size of containers is less than 5000TEU class. Two parameters for normal distributions of the slenderness ratios (mean and standard deviation) are suggested and probable ranges of the slenderness ratios are also graphically presented. The ultimate strengths of the stiffened plates are presented using the various simplified formulas and nonlinear FEAs. As well, average compressive strength curves, which are necessary for the estimation of the hull girder moment capacities, are proposed. It is proved that formulas for stiffened plates in CSR overestimate slightly in overall average strain range. Mode5 formula (plate buckling mode) in CSR show unreasonably conservative results with respect to the ultimate strengths rather than post-ultimate average compressive strengths.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1250-1261
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• 2002

Many research works have validated the J-T approach to elastic-plastic crack-tip stress fields in a variety of plane strain specimens. To generalize the validity of J-T method, further investigations are however needed for more practical 3D structures than the idealized plane strain specimens. In this work, we perform 3D finite element (FE) modeling of welded plate and straight pipe, and accompanying elastic, elastic-plastic FE analyses. Manual 3D modeling is almost prohibitive, since the models contain semi-elliptical interfacial cracks which require singular elements. To overcome this kind of barrier, we develop a program generating the meshes for semi-elliptical interfacial cracks. We then compare the detailed 3D FE stress fields to those predicted with J-T two parameters. Thereby we extend the validity of J-T application to 3D structures and infer some useful informations for the design or assessment of pipe welds.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.649-659
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• 2002

For a variety of elastic-plastic stress fields of plane strain specimens, many research works verified the validity of J-T approach. To generalize the validity of J-T method, however, further investigations are needed for more practical 3D structures than the idealized geometries as plane strain specimens. In this work, selecting two main types of structures such as plate and straight pipe, we perform 3D finite element(FE) modeling, and accompanying elastic, elastic-plastic FE analyses. We then study the validity of J-T application to 3D structures, and present some useful informations for the design or assessment of pipe welds by comparing the stress fields from the detailed 3D FE analyses to those predicted with J-T two parameters.