• Korea-Australia Rheology Journal
• /
• v.13 no.1
• /
• pp.37-45
• /
• 2001

Numerical simulation of coextrusion process of viscoelastic fluids within a die has been carried out. In the coextrusion process velocity profile at the outflow boundary is not known a priori, which makes it difficult to impose the proper boundary condition at the outflow boundary. This difficulty has been avoided by using the open boundary condition (OBC) method. In this study, elastic viscous stress splitting (EVSS) formulation with streamline upwind (SU) method has been used in the finite element method. In order to test the validity of the OBC method, comparison between the results of fully developed condition at the outlet and those of OBC has been made for a Newtonian fluid. In the case of upper convected Maxwell (UCM) fluid, the effect of outflow boundary condition on the interface position has been investigated by using two meshes having different downstream lengths. In both cases, the results with the OBC method showed reasonable interface shape. In particular, for the UCM fluid the interface shape calculated with OBC was independent of the downstream length, while the results with the zero traction condition showed oscillation of interface position close to the outlet. Viscosity difference was found to be more important than elasticity difference in determining the final interface position. However, the overshoot of interface position near the con-fluent point increased with elasticity.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.9
• /
• pp.2737-2740
• /
• 2013

The layered $KTiNbO_5$ was successfully synthesized with titanium(IV) isopropoxide and niobium oxalate by a novel polymerized complex (PC) method. The morphology and structure of the as-prepared sample was characterized by means of High-Resolution Transmission Electron Microscope, powder X-ray diffraction, and Laser Raman Spectroscopy. The spectral response characteristic was recorded by using UV-vis Diffuse Reflectance Spectroscopy. Results show that $KTiNbO_5$ as-prepared by PC method presents an uniform morphology of nano-particles, the mean particle sizes is ca. 28 nm corresponding to the (002), and the crystal structure can be well indexed to the orthorhombic phase. The sample as-prepared by PC method has higher band gap energy than that of the sample prepared by a solid-state reaction method due to the quantum size effect.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.9
• /
• pp.832-837
• /
• 2006

Antennas were fabricated by physical(adhesive) and chemical(deposition+plating) method on organic-inorganic composite material. And antennas were measured dielectric constant and gain. Dielectric constant of antennas were fabricated by physical method was decreased with increase of adhesive tape thickness and number of conduction material composition. But antennas were fabricated by chemical method was reached to 90 % of dielectric material. Gain of antennas were fabricated by physical method was decreased with increase of adhesive tape thickness. But they were unrelated with conduction material composition. The other side antennas were fabricated by chemical method excelled more 0.8 dBic than antennas were fabricated by physical method in gain of antenna. Finally, chemical method can expect excellent product process because it can produce smaller size, higher gain and elimination of many handworks.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.8
• /
• pp.2431-2435
• /
• 2013

A simple and efficient method for the synthesis of spiro[4H-pyran-oxindole] derivatives by means of three-component reactions between isatins, malononitrile or ethyl cyano-acetate, and 1,3-dicarbonyl compounds in the presence of catalytic amount of magnesium perchlorate in 50% aqueous ethanol medium has been described.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2001.05a
• /
• pp.217-220
• /
• 2001

In the shearing process the burr or rollover must be minimized in order to improve the quality of product. The burr size can be minimized by control of several process parameters. But removal of all burrs are impossible. Most mechanical type deburring methods (vibrating bowls, rotating barrels, shot blasting, for example.) will remove large burrs, other methods use chemical (electro-chemical deburring) or heat (thermal energy deburring). The electro-chemical deburring process removes burrs by the deplating method. Electro-chemical deburring equipment is requires a small capital investment than other methods(mechanical or thermal methods). Electro-chemical deburring method need to many parameters for control such as a time, voltage and concentration of electrolyte. In this paper shows relations of these parameters by experiment.

• Corrosion Science and Technology
• /
• v.7 no.3
• /
• pp.173-178
• /
• 2008

Recently an electrochemical noise method (ENM) with three electrodes has gained attention as a corrosion monitoring system in chemical plants. So far a few studies have been carried out for localized corrosion and environmental cracking of chemical plant materials. In this paper the ENM system is briefly summarized. Then an application of ENM to general corrosion for chemical plant materials is described. The emphasis is focused upon the analysis of stress on the corrosion cracking process of austenitic stainless steel in 30% $MgCl_2$ aqueous solution and the corrosion fatigue crack initiation process of 12 Cr stainless steel in 3% NaCl aqueous solution by ENM. Finally future problems for ENM to monitor regarding corrosion and environmental cracking in chemical plants are discussed.

• Analytical Science and Technology
• /
• v.21 no.5
• /
• pp.438-441
• /
• 2008

We have developed an alternative to the internal chemical reference based on a calibrated reference signal which is not a real NMR line but an electronically produced signal (HERETIC) and determined the phosphorus concentration using this method. The area ratio of HERETIC and sample peaks obtained from the standard samples was used to measure the concentrations of different samples directly. The analysis of phosphorus by this method showed the excellent linear regression coefficient ($R^2=0.9999$) for the concentration range from 20 ppm to 500 ppm with HERETIC peak as reference.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.10
• /
• pp.1635-1636
• /
• 2007

• Bulletin of the Korean Chemical Society
• /
• v.10 no.4
• /
• pp.406-407
• /
• 1989

• Korean Chemical Engineering Research
• /
• v.55 no.4
• /
• pp.510-513
• /
• 2017

Patchouli oil extraction in general is still using conventional methods that require a long time of extraction. It is therefore necessary to develop extraction methods to obtain patchouli oil with optimum yield and quality. One of the new methods, which has been successfully developed, is microwave hydrodistillation (MHD). In addition to optimizing the extraction process of patchouli oil, this study also used microwave air-hydrodistillation (MAHD). Based on the research results, extraction using MAHD method can produce higher yield of patchouli oil when compared using MHD method. Also, based on the results of the analysis by GC-MS, extraction using MAHD method can produce quality of patchouli oil that is almost the same when compared using MHD method. This is supported by the results of the analysis by GC-MS, which showed that the content of patchouli alcohol is the main component of patchouli oil, and is almost the same for patchouli oil extracted using MHD method (26.32%) and MAHD method (25.23%).