• Journal of Welding and Joining
• /
• v.32 no.6
• /
• pp.47-55
• /
• 2014

The purpose of the study is to produce a mechanically improved weld and minimum variation of color through comparing unpulsed and pulsed GTAW (Gas Tungsten Arc Welding) for pure titanium (CP grade7) tube. Pulsed GTAW using 60 A peak current and 20 A background current (1:9) achieved the wider window of welding conditions having part and full penetration without burn-through than the case of unpulsed GTAW. Moreover, the pulsed welding reduced a discoloration on the back bead of the weld and the size of microstructures (basket weave and serrated ${\alpha}$). That is because the pulsed welding has it's a low heat input and severe weld flow induced from electric current variation. Furthermore, the pulsed welding improved the bending property of the welded Ti tube. The enhanced bending property for the pulsed GTAW was due to the insignificant discoloration on the weld surface with maintaining the metal polish.

• KSBB Journal
• /
• v.25 no.4
• /
• pp.363-370
• /
• 2010

Lipid from Scenedesmus sp. was extracted, fractionated and purified by silicic acid column chromatography. Total lipid content of extract was $21.38{\pm}1.03$ wt%, and triacylglycerol, an index lipid for biodiesel production was detected. Ten species of $C_{16}{\sim}C_{22}$ with saturated and unsaturated fatty acid were identified showing the very adequate fatty acid profiles for biodiesel production with a good flow property at low temperature. The fractions of glycolipid, neutral and phospholipid were 52.64, 28.10 and 19.26% of total lipid, respectively. The triacylglycerol of 12.63% and chlorophyll a of 49.47% was fractioned using stepwise elution of n-hexane-diethyl ether (95:5, v/v) solvent. The high content of chlorophyll was considered as a potential source of value-added co-product.

• Journal of ILASS-Korea
• /
• v.26 no.1
• /
• pp.1-8
• /
• 2021

Droplet evaporation has been known as a common phenomenon in daily life, and it has been widely used for many applications. In particular, the influence of the different heated substrates on evaporation flux and flow characteristics is essential in understanding heat and mass transfer of evaporating droplets. This study aims to simulate the droplet evaporation process by considering variation of thermal property depending on the substrates and the surface temperature. The commercial program of ANSYS Fluent (V.17.2) is used for simulating the conjugated heat transfer in the solid-liquid-vapor domains. Moreover, we adopt the diffusion-limited model to predict the evaporation flux on the different heated substrates. It is found that the evaporation rate significantly changes with the increase in substrate temperature. The evaporation rate substantially varies with different substrates because of variation of thermal property. Also, the droplet evaporates more rapidly as the surface temperature increases owing to an increase in saturation vapor pressure as well as the free convection effect caused by the density gradient.

• International conference on construction engineering and project management
• /
• 2022.06a
• /
• pp.1106-1113
• /
• 2022

Cost segregation helps reduce tax liabilities by reclassifying real property to personal property and accelerates tax depreciation of a property. A typical cost segregation study requires much time and high costs. This study proposed a BIM integrated cost segregation process that can be applied to any commercial building project. The proposed BIM-based cost segregation process was verified in a new commercial construction project. It approved that this approach can: (1) increase the cash flow for the owner and provide assistance to tax-paying enterprises; (2) enable the contractor to use it as an added value in the bidding process; (3) realize data sharing in a common platform to improve the cost segregation study efficiency and reduce costs and errors; (4) contribute to the asset management in the life cycle of buildings while filling in the blank of cost segregation process. Future studies will focus on the automation of cost segregation and asset management in building construction's life cycle.

• 한국전산유체공학회:학술대회논문집
• /
• 2009.04a
• /
• pp.283-289
• /
• 2009

In level set method, material properties are made to change smoothly across an interface of two materials with different properties by introducing an interpolation or smoothing scheme. So far, the weighted arithmetic mean (WAM) method has been exclusively adopted in level set method, without complete assessment for its validity. We showed here that the weighted harmonic mean (WHM) method for rate constants of various rate processes, including viscosity, thermal conductivity, electrical conductivity, and permittivity, gives much more accurate results than the WAM method. The selection of interpolation scheme is particularly important in multi-phase electrohydrodynamic problems in which driving force for fluid flow is electrical force exerted on the phase interface. Our analysis also showed that WHM method for both electrical conductivity and permittivity gives not only more accurate, but also more physically realistic distribution of electrical force at the interface. Our arguments are confirmed by numerical simulations of drop deformation under DC electric field.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.1419-1424
• /
• 2007

Centrifugal turbo blower is requested highly efficiency and low noise in FCEV, but the noise generated by this machine causes of the most serious problems in the NVH performance. In general, centrifugal turbo blower is dominated by mechanical noise and aerodynamic noise. Mechanical noise is generated by rotation of the bearing, misalignment and unbalance. And aerodynamic noise is generated by the strong intersection between the flow discharged from the impeller and the cut-off in the casing. The first object of this study is to comprehend a noise property of the blower through the noise test. And, second object is to bring up the method that can reduce blower noise.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.575-580
• /
• 2002

The most recent, like any other field we have requested that the concrete would increase more a performance. So, in this research we are intended to study on the property of Photocatalytic Concrete which is one of the High Performance Concrete. The fundamental phenomena of the Photocatalytic Concrete were observed by the NOx Analyzer, Bonding strength, SEM, Flow and Surface hardness(Pencil tester). As a result of this study, the Photocatalytic Concrete used Photocatalytic powder, admixture and other materials can obtain its properties, also photocatalytic efficiency(NOx reduction). Also, we have convinced of the Photocatalytic Concrete possibility and put on a spurt to improve its properties added a various experiment.

• YAKHAK HOEJI
• /
• v.46 no.1
• /
• pp.6-10
• /
• 2002

The present study investigated the rheological properties and adjuvant activity of IgG production of ι-Carrageenan prepared using two different methods . incubation at 37.4$^{\circ}C$ after either being heated or not being heated int 6$0^{\circ}C$ for 10 minutes. The carrageenan exhibited plastic flow with thixotropy in both cases, but the viscosity of the sample that had been heated was significantly higher. C57BL/6 mice were then immunized intraperitoneally with either of the carrageenans containing protein antigens. The maximum adjuvant effect was found when using the nonheated carrageenan, especially in term of IgG2a, IgG2b, and IgG3 production. In contrast, IgG1 antibody production was the same far both types of carrageenan. furthermore, when administered oral1y, neither type of carrageenan resulted in the production of any antibodies.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.5
• /
• pp.516-523
• /
• 2008

Centrifugal turbo blower is requested highly efficiency and low noise in FCEV, but the noise generated by this machine causes of the most serious problems in the NVH performance. In general, centrifugal turbo blower is dominated by mechanical noise and aerodynamic noise. Mechanical noise is generated by rotation of the bearing, misalignment and unbalance. And aerodynamic noise is generated by the strong intersection between the flow discharged from the impeller and the cut-off in the casing. The first object of this study is to comprehend a noise property of the blower through the noise test. And, second object is to bring up the method that can reduce blower noise.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.547-550
• /
• 2000

The steel pipe for fluid catalytic cracking(FCC) unit. petroleum refinery, is lined with refractory to protect the system from high-temperature of the internal flow. The property of the refractory has an effect upon the stress analysis of FCC unit. Because 1-D pipe element or 3-D shell element are usually used in commercial codes of stress analysis to evaluate the structural soundness, the equivalent elastic modulus considering steel and refractory should be applied. In the research, the theoretical method to obtain the value of the equivalent property is introduced and then the stress analysis is carried out with the part of FCC unit.