• Journal of Korea Foundry Society
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• v.19 no.5
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• pp.393-402
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• 1999

The reheating of the billet in the semi-solid state as quickly and homogeneously as possible is one of the most important aspects. From this point of view, an optimal design of the induction coil is necessary. The objective of inductive coil designsi a uniform induction heating over the length of the billet. The effect of coil length, diameter, the gap between coil surface and billet and axial position of the billet on temperature distribution of billet has been investigated. These design parameters have an important effectiveness on the electro-magnetic field. Therefore, in this study an optimal coil design to minimize electromagnetic ed effect will be proposed by defining the relationship between billet length and coil length. In particular, key point in induction heating process is focussed on optimizing the coil design with regard to the size of the heating billet and the frequency of induction heating system. After demonstrating the suitability of an optimal coil design through the FEM simulation of the induction heating process, the results of the coil design are also applied to the reheating process to obtain a fine globular microstructure. Its considered that the reheating conditions of aluminum alloys for thixoforging and a new CAE model of the induction heating process are very useful for thixoforging practitioners including induction heating ones.

• Journal of Korea Foundry Society
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• v.12 no.6
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• pp.471-479
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• 1992

For the last 2 decades, the bonding materials for the foundry sand and the foundry equipments with high performance have been developed and employed in the foundry shops. In those periods, the furan resins hardened in higher temperature have been replaced with the self-hardened ones in the room temperature. Simultaneously the various reclamation methods of the self-hardened furan resin sand have been developed in order to get the clean working environments, the reduction of solid wastes and the lower of production cost in the foundry. In this experimental study, the combustion reclamation method using the fluidized bed among the various methods was studied in order to reduce the L.O.I. and /or $N_2$ gas due to the deposition of the furan resins and the hardeners. Comparing the results of this experimental combustion reclamation method with those of the employed pneumatic method, the Surface Stability Index of the specimen made by combustion method is 30% higher than that of the latter one and L.O.I. decreases about 30%. The reclamation temperature of 650$^{\circ}C$ in this experimental fluidized bed would be recommended in the viewpoints of the reclamation period, the fuel consumption and the residual quantity of the furan resin. The formula determining the minimum fluidizing velocities according to the temperatures in the fluidized bed has been obtained.

• Natural Product Sciences
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• v.13 no.2
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• pp.128-131
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• 2007

Tumor angiogenesis is a critical step f3r the growth and metastasis of solid tumors. Vascular endothelial growth factor (VEGF) is the most important angiogenic molecule associated with tumor-induced neovascularization. VEGF exerts its activity through binding to its receptor tyrosine kinase, KDR/Flk-1, expressed on the surface of endothelial cells. This study was carried out to investigate inhibitory effect of extracts from root cortex of Paeonia suffruticosa Andrews on VEGF binding to VEGF receptor. The MeOH extract from P. suffrutiocosa Andr. inhibited the binding of KDR/Flk-1-Fc to immobilized VEGF$_{165}$ more than 45% at the concentration of 100 ${\mu}$g/mL. The MeOH extract was further fractionated into n-hexane, ethyl acetate, n-BuOH, and aqueous fractions. Among the four fractions, the ethyl acetate fraction from the root cortex of P. suffruticosa Andr. exhibited highly effective inhibition (${\approx}$ 79% inhibition) and then n-BuOH fraction (${\approx}$ 45% inhibition) on the binding of KDR/Flk-1-Fc to immobilized VEGF$_{165}$ at the concentration of 100 ${\mu}$g/mL. The ethyl acetate fraction from the root cortex of P. suffruticosa Andr. more efficiently blocked VEGF-induced human umbilical vein endothelial cell proliferation, than the growth of HT1080 human fibrosarcoma. Our results suggest that P. suffruticosa Andr. may be used as a candidate fur developing anti-angiogenic agent.

• Korea-Australia Rheology Journal
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• v.15 no.2
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• pp.83-90
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• 2003

In cases of the microfluidic channel, the electrokinetic influence on the transport behavior can be found. The externally applied body force originated from the electrostatic interaction between the nonlinear Poisson-Boltzmann field and the flow-induced electrical field is applied in the equation of motion. The electrostatic potential profile is computed a priori by applying the finite difference scheme, and an analytical solution to the Navier-Stokes equation of motion for slit-like microchannel is obtained via the Green's function. An explicit analytical expression for the induced electrokinetic potential is derived as functions of relevant physicochemical parameters. The effects of the electric double layer, the zeta potential of the solid surface, and the charge condition of the channel wall on the velocity profile as well as the electroviscous behavior are examined. With increases in either electric double layer or zeta potential, the average fluid velocity in the channel of same charge is entirely reduced, whereas the electroviscous effect becomes stronger. We observed an opposite behavior in the channel of opposite charge, where the attractive electrostatic interactions are presented.

• Journal of Korean Society on Water Environment
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• v.22 no.3
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• pp.468-474
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• 2006

In the secondary settling tanks, three different types of settling phenomena occurs; i.e., zone settling for sludge thickening in the bottom part of settling tank, and discrete and flocculent settling for clarification in the upper part. In this paper, morphological parameters of the floc in sludge blanket layers along the length of a long rectangular tank were investigated. The plant used for this study had a serious bulking problem caused by Microthrix parvicella. Floc size decreased as the surface area of settling tank increases, which indicates that in the secondary settling tank where zone settling believed to be predominant, free or flocculent type of settling contributes to floc size distributions. Large floc particles deposit in the front zone of settling tank, but small and loose flocs mostly in the zone near its outlet. On the other hand, filament length contained in one gram of sludge blanket solid increases along the flow direction. Large flocs with less filaments settle faster, but small flocs having more filaments result in poor settling. These results support function of microorganism selection occurring in secondary settling tank. In addition, designing a long rectangluar settling tank with double hoppers might be one of the ways of bulking control, but this idea has to be verified with a further study.

• Journal of Radiation Industry
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• v.4 no.1
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• pp.13-17
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• 2010

The radioisotope labelling study was carried out for the sediment transport investigation. The fate of suspended solid materials is deeply related to the harbour siltation and the shoreline deformation that take place as a result of the artificial development of coastal area. In the experiment, $^{99m}TcO_4{^-}$ was chemically reduced and labelled in such a way that the labelled particles have the similar settling characteristics with the natural sediment. The radioisotope labelling techniques can be widely used for the natural resource exploration where the hydraulic dynamics of underground water and surface water are of importance.

• Korean Journal of Metals and Materials
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• v.48 no.9
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• pp.856-860
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• 2010

Silver nanoparticles were formed on silica substrates through thin film dewetting at high temperature. The microstructural and morphological evolution of the particles were characterized as a function of processing variables such as initial film thickness, annealing time, and temperature. Silver thin films were deposited onto the silica using a pulsed laser deposition system and annealed in reducing atmosphere to induce agglomeration of the films. The film thicknesses before dewetting were in the range of 5 to 25 nm. A noticeable agglomeration occurs with annealing at temperatures higher than $300^{\circ}C$, and higher annealing temperature increases particle size uniformity for the same film thickness sample. Average particle size linearly correlates to the film thickness, but it does not strongly depend on annealing temperature and time, although threshold temperature for complete dewetting increases with an increase of film thickness. Lower annealing temperature develops faceted surface morphology of the silver particles by enhancing the growth of the low index crystal plane of the particles.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.8
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• pp.316-324
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• 2016

This study investigated a compact regenerative evaporative cooler (REC). To achieve practical applications of an REC, it is very important to consider the compactness as well as the cooling performance. Therefore, a prototype of the REC was designed and fabricated to improve the compactness by reducing the length through the insertion of fins in both the dry and wet channels. The REC prototype was tested in terms of performance evaluation under various operating conditions. An analytical model was also developed to analyze the effects of the axial conduction through the solid body of the REC, the wetness of the surface in the wet channel, and the thermal capacity of the evaporation water flow. The model was validated by comparing the results of a simulation with experimental data. The numerical simulation was based on the model to analyze the performance of the REC and to suggest methods to improve the cooling performance of the REC. Finally, the performance of the present REC was compared to that obtained in previous experimental studies. The results showed that the REC prototype in the present study is the most compact and achieves the highest cooling performance.

• Journal of Distribution Science
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• v.19 no.12
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• pp.71-81
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• 2021

Purpose: This study to seek to answer two research questions in distribution science: what photo decoration cues in online grocery stores could be identified? Could photo decoration cues significantly effect on the affective perception and behavioral intention of consumers? Research design, data, and methodology: his study conducted a laboratory experiment with a 2×2×2 factorial design to validate the proposed research model and test our proposed hypotheses. Research design, data and methodology: Two stages experiments were adopted in this study, among 360 voluntaries who have had an experience of online grocery shopping, 331 valid data had been collected and analyzed using MANOVA and PLS-SEM algorism. Results: (1) both reflective surface and complementary goods layout lead to visual appeal and shopping enjoyment; (2) contrast color usage positively impacts on visual appeal while does not significantly affect shopping enjoyment; (3) consumers' affective responses positively impact attitudes toward product and store which in turn lead to purchase intention and store loyalty. Implications for research and practice are discussed. Conclusions: Using the media richness theory, visual rhetoric theory and visual design literature as the theoretical foundation, the study provides a solid foundation to comprehend the impact of photo design artifacts on consumers' affective responses when online consumers shopping online for fresh grocery.

• Journal of Powder Materials
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• v.25 no.6
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• pp.514-522
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• 2018

Layered-double hydroxide (LDH)-based nanostructures offer the two-fold advantage of being active catalysts with incredibly large specific surface areas. As such, they have been studied extensively over the last decade and applied in roles as diverse as light source, catalyst, energy storage mechanism, absorber, and anion exchanger. They exhibit a unique lamellar structure consisting of a wide variety of combinations of metal cations and various anions, which determine their physical and chemical performances, and make them a popular research topic. Many reviewed papers deal with these unique properties, synthetic methods, and applications. Most of them, however, are focused on the form-factor of nanopowder, as well as on the control of morphologies via one-step synthetic methods. LDH nanostructures need to be easy to control and fabricate on rigid substrates such as metals, semiconductors, oxides, and insulators, to facilitate more viable applications of these nanostructures to various solid-state devices. In this review, we explore ways to grow and control the various LDH nanostructures on rigid substrates.