• Fire Science and Engineering
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• v.17 no.3
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• pp.50-54
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• 2003

The backlayer phenomena of smoke in the road tunnel is evaluated through numerical experiments. A commercial code, PHOENICS is used to simulate smoke flow in the road tunnel. The independent and dependent variables are ventilation air velocity and the length of backlayer of smoke respectively. Hybrid scheme and $textsc{k}-\varepsilon$ turbulence model is adopted in the simulation process and mass residual is used as a convergence criterion. The experimental results say that the length of backlayer is reduced linearly with the increase of ventilating air velocity and that there is a critical air velocity which prevents from the onset of backlayering phenomena. One finds that there is a fresh air region near the bottom of tunnel which could make the passenger escape from the region polluted by smoke. These phenomena come from the severe vertical stratification of the smoke air mixture in the tunnel.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.3
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• pp.215-224
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• 1990

Finite element model capable of solving coupled deformation-fluid diffusion equations for the fully saturated porous medium was developed using Galerkin's residual method. This model was used to study the mechanical and hydraulic behaviors of unconsolidated sediment near South Harbor, Pusan. The vertical displacement of top surface clay sediment, when subjected to the external load, is significantly affected by the excessive pore pres- sure buildup and its decay due to the pore fluid diffusion. The sand deposit overlain by the much less permeable clay layer serves as a flow channel. Consequently, the fluid diffusion due to pore pressure difference is significantly facilitated, which also affects the diffusion-dependent sediment deformation.

• Corrosion Science and Technology
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• v.11 no.6
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• pp.218-224
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• 2012

Liquid droplet impingement erosion (LDIE) known to be generated in aircraft and turbine blades is recently appeared in nuclear piping. UT thickness measurements with both A-scan and B-scan UT inspection equipments were performed for a component estimated as susceptible to LDIE in feedwater heater vent system. The thickness data measured with B-Scan equipment were compared with those of A-Scan. Thermal hydraulic analysis based on ANSYS FLUENT code was performed to analyze the behavior of liquid droplets inside piping. The wall thinning rate and residual lifetime based on both existing Sanchez-Caldera equation and measuring data were also calculated to identify the applicability of the existing equation to the LDIE management of nuclear piping. Because Sanchez-Caldera equation do not consider the feature of magnetite formed inside piping, droplet size, colliding frequency, the development of new evaluation method urgently needs to manage the pipe wall thinning caused by LDIE.

• Nuclear Engineering and Technology
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• v.33 no.6
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• pp.638-651
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• 2001

The present study is to assess the applicability of the best-estimate thermal-hydraulic code, MARS 1.4, for the analysis of thermal-hydraulic behavior in PWRs during natural circulation conditions. The code simulates a natural circulation test, BETHSY test 4. la, which was conducted on the integral test facility of BETHSY. The test represented the cooling states of the primary cooling system under single-phase natural circulation, two-phase natural circulation and the reflux condensation mode with conditions corresponding to the residual power, 2% of the rated core power value and 6.8 MPa at the secondary system. Based on MARS 1.4 calculations, the major thermal-hydraulic behaviors during natural circulation are evaluated and the differences between the experimental data and calculated results are identified. The calculated results show generally good behavior with regard to the experimental results; the region of single-phase natural circulation is 100-92% of the initial mass inventory, two-phase natural circulation is 84-63 %, and the reflux condensation mode occurred below 58 %. U-tubes empty and the core uncovery are obtained at 39 % and 34 % of the initial mass inventory, respectively.

• Journal of the Korean Vacuum Society
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• v.8 no.2
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• pp.165-171
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• 1999

Diamond-like carbon(DLC) films were synthesized using the rf-plasma CVD technique with the addition of small amounts of nitrogen and oxygen to a gas mixture of $CH_4$ and $H_2$. The gas flow ratio of $CH_4$ to $H_2$ was 2.4:1, and 3% , 13.6% of nitrogen were added to the gas mixture of $CH_4$ and $H_2$ for the deposition of DLC films. The film stress tended to decrease as the nitrogen concentration increased from 3% to 13.6%, probably due to the decrease of the number of the interlink between carbon atoms. The residual stress tended to slightly decrease when 3% of oxygen was added. Scratch tests were performed to investigate the adhesion between the DLC films and the Ti intelayer after pretreating the TiN surface with direct hydrogen plasma. The adhesion was enhanced by adding nitrogen and oxygen to the $CH_4$ and $H_2$ gas mixture. The adhesion for the 3% nitrogen addition was better than that for the 13.6% nitrogen addition. The Vicker's hardness of the DLC films was measured to be 1100Hv.

• Journal of Environmental Science International
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• v.24 no.6
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• pp.721-729
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• 2015

Surface heat balance of the Gangjeong-Goryung Reservoir is analyzed for 12-17 August 2013. Each flux elements at the water surface is derived from the special field observations with application of an aerodynamical bulk method for the turbulent heat fluxes and empirical formulae for the radiation heat fluxes. The rate of heat storage in the reservoir is estimated by using estimated by surface heating rate and the vertical water temperature data. The flux divergence of heat transport is estimated as a residual. The features of the surface heat balance are almost decided by the latent heat flux and the solar radiation flux. On average for 12-17 August 2014 in the Gangjeong- Goryung Reservoir, if one defines the insolation at the water surface as 100 %, 94 % is absorbed in the reservoir; thereafter the reservoir loses about 30~50% by sensible heat, latent heat and net long-wave radiation. The residue of 50~80 % raises the water temperature in the reservoir or transported away by the river flow during the daytime.

• Tuberculosis and Respiratory Diseases
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• v.40 no.4
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• pp.345-352
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• 1993

The role of magnetic resonance(MR) imaging in the evaluation of thoracic disease has been limited Nontheless, MR has inherent properties of better contrast resolution than CT allowing tissue-specific diagnosis. MR has capability of direct imaging in sagittal, coronal, and oblique planes which provide better anatomic information than axial images of CT such as lesions in the pulmonary apex, aorticopulmonary window, peridiaphragmatic region, and subcarinal region. MR is sensitive to blood flow making it an ideal imaging modality for the evaluation of cardiovascular system of the thorax without the need for intravenous contrast media. Technical developments and better control of motion artifacts have resulted in improved image quality, and clinical applications of MR imaging in thoracic diseases have been expanded. Although MR imaging is considered as a problem-solving tool in patients with equivocal CT findings, MR should be used as the primary imaging modality in the following situations: 1) Evaluation of the cardiovascular abnormalities of the thorax 2) Evaluation of the superior sulcus tumors 3) Evaluation of the chest wall invasion or mediastinal invasion by tumor 4) Evaluation of the posterior mediastinal mass, especially neurogenic tumor 5) Differentiation of fibrosis and residual or recurrent tumor, especially in lymphoma 6) Evaluation of brachial plexopathy With technical developments and fast scan capabilities, clinical indications for MR imaging in thorax will increase in the area of pulmonary parenchymal and pulmonary vascular imaging.

• KSBB Journal
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• v.13 no.2
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• pp.203-208
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• 1998

We investigated the effects of dissolved oxygen (D.O.) and fructose (C-source) on cell growth and biosynthesis of cyclosporin A (CyA) produced as a secondary metabolite by a wild-type filamentous fungus, Tolypocladium inflatum. This was performed by controlling the level of D.O. and the residual C-source, as required, through adjustment of medium flow rate, medium concentration and agitation rate in fed-batch cultures. CyA production was furned out to be maximal, when D.O. level was controlled around 10% saturated D.O. and concentration of the C-source was maintained sufficiently low (below 2 g/L) not to cause carbon catabolite repression. Under this culture condition, we obtained the highest values of CyA concentration (507.14 mg/L), Qp (2.11 mg CyA/L/hr), $Y_x/s$ (0.49 g DCW/g fructose), $Y_p/s$<(22.56 mg CyA/g fructose), and YTEX>$_p/x$ (48.31 mg CyA/g DCW), but relatively lower values of cell concentration (11.98 g DCW/L) and cell productivity (0.043 g DCW/L/hr), in comparison with other parallel fed-batch fermentation conditions. These results implied that, in the carbon-limited culture with 10% saturated D.O. level, the producer microorganism utilized the C-source more efficiently for secondary metabolism.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.11a
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• pp.95-98
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• 2007

This study investigates the mechanical properties of the high strength concrete in the region of 80MPa corresponding to the temperature and fiber content change. For the properties of the fresh, slump flow is $600{\pm}100mm$, and air content is $3.0{\pm}1.0%$. They satisfy each targets, and there was no difference for the each fiber types. As the propertied of the hardened concrete, the compressive strength at 28 days is indicated over 80MPa, and they are similar to the change of the fiber types. The residual compressive strength in response to the temperature change of the NY, PP, and NY+PP fiber at $200^{\circ}C$ are increased by 115, 114, and 110% on the standard condition, and it is suddenly decreased at $400^{\circ}C$. They are decreased by 33, 19, and 16% on the standard condition at $800^{\circ}C$.

• Structural Engineering and Mechanics
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• v.8 no.3
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• pp.233-242
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• 1999

In the present study, the elasto-plastic analysis of prismatic plate structures subjected to pure bending is carried out using the finite strip method. The end cross-sections of the structure are assumed to remain plane during deformation, and the compatibility along corner lines is ensured by choosing proper displacement functions. The effects of both the initial geometrical imperfections and residual stresses due to fabrication are included in the combined geometrically and materially nonlinear simulation. The von-Mises yield criterion and the Prandtl-Reuss flow theory of plasticity are applied in modelling the elasto-plastic behavior of material. Newton-Raphson iterations are carried out as the rotation of the end cross sections of the structure is increased step by step. The parameter representing the overall axial strain of structure is adjusted constantly during the iteration process in order to eliminate the resulting overall axial force on any cross-section of the structure in correspondence with the assumption of zero axial force in pure bending. Several numerical examples are presented to validate the present method and to investigate the effects of some material and geometrical parameters.