• Journal of Energy Engineering
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• v.8 no.2
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• pp.325-332
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• 1999

When a rotating heat pipe is in operation, liquid condensate returns from the condenser to the evaporator along the inside surface by both components of gravitational and centrifugal forces. It was known that its performance was largely dependent on how to increase the flow rates of condensate and keep the condensate film thickness as thin as possible. Most of research works were focussed on this goal, and various inner wall structures such as tapered wall, stepped wall or coil inserted pipe etc. were developed. In the present study, a stepped wall structure with 3 internal grooves in the condenser and adiabatic zone was examined. For this system, the condensate would flow down to the evaporator through the grooves, resulting a reduced film thickness over the condenser surface. Experimental data showed an enhancement of heat transfer coefficient in the condenser zone. An analytical solution to the condensate film thickness showed that the analytically calculated values of heat transfer coefficient were considerably higher than the experimental data.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.963-969
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• 1996

Cure characteristics of DGEBA(diglycidyl ether of bisphenol A)/dicy(dicyandiamide) system containing diuron(3-(3,4-dichloro phenyl) -1,1-dimethylurea) as an accelerator was investigated. The system has shelf life of six months because dicy is insoluble in liquid/solid resins at room temperature. It is generally known that dicy is an adequate curing agent for one component adhesive due to its highly latent property. With increasing the amount of added dicy, reaction heat of DGEBA/dicy system increased and degree of conversion was not varied. For DGEBA/dicy/diuron system, cure temperature decreased about $40^{\circ}C$ and cure reaction became fast by the addition of diuron which activates dicy. $T_g$ of the mixed resin decreased with the amount of accelerator. which was interpreated with molecular structure forming loose chain. Cure kinetics of DGEBA/dicy and DGEBA/dicy/diuron system were explained using Kamal's autocatalytic reaction model. The effect of acceleration was confirmed with that reaction model.

• Analytical Science and Technology
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• v.11 no.2
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• pp.92-95
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• 1998

K-SGICs(synthetic graphite intercalation compounds) were synthesized in a modified two-bulb pyrex tube. The pressure in the two-bulb tube was maintained at approximately $10^{-3}$ torr for the reaction of potassium and graphite. Deintercalation process of the K-SGlCs obtained by the modified method was heat-treated by keeping in liquid paraffin between $25^{\circ}C$ and $1400^{\circ}C$. The thermal stability and the temperature dependence of the K-SGICs were characterized using differential scanning calorimeter(DSC) analyzer. Enthalpy and entropy for K-SGIC formations were calculated by confirming the deintercalation and thermodynamic exothermic reactions depending on the various temperatures. The structure changes and thermal stability of K-SGICs during the deintercalation reaction of potassium ions and the interlayer spaces of the synthetic graphite were identified by X-ray diffraction(XRD).

• Journal of Pharmacopuncture
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• v.8 no.3
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• pp.5-9
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• 2005

Observation of intra-vascular threadlike structures in the blood vessels of rats is reported with the images by differential interference contrast microscope, and fluorescence inverted microscope of the acridine-orange stained samples. The confocal microscope image and the hematoxylin-eosin staining revealed the distinctive pattern of nuclei distribution that clearly discerned the threadlike structure from fibrin, capillary, small venule, arteriole, or lymph vessel. Physiological function of the intra-vascular thread in connection with acupuncture is discussed. Especially, this threadlike duct can be a circulation path for herb-liquid flow, which may provide the scientific mechanism for therapeutic effect of herbal acupuncture.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2267-2276
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• 1996

Twin-fluid atomization has been widely used in combustors and process industries because of its high performance and simple structure. Flow visualization and pressure measurements were conducted to investigate the effects of gas flow in twin-fluid atomization. Schlieren photographs showed that changes in atomizing gas pressure, altered the wave patterns, and the lengths of both recitrculating toroid (impinging stangnation point) nad supersonic flow region in the jet. A longer supersonic wave pattern like net-shape wqas observed as atomizing gas pressure increased. The disintegration phenomenon of liquid delivery tube. The variation of spray angles with gas pressures were obtained by visualization using laser sheet beam. Suction pressuresat the nozzle orifice exit and recirculating region are shown to be used to estimate the stable atomization condition of a twin-fluid atomizer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.489-493
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• 2005

TFT-LCD(Thin Film Transistor Liquid Crystal Display) module is representative commercial product of FPD(Flat Panel Display). Thickness of TFT-LCD module is very thin. It is adopted for major display unit for IT devices such as Cellular Phone, Camcorder, Digital camera and etc. Due to the harsh user environment of mobile IT devices, it requires complicated structure and tight assembly. And user requirements for the mechanical functionalities of TFT-LCD module become more strict. However, TFT-LCD module is normally weak to high level transient mechanical shock. Since it uses thin crystallized panel. Therefore, anti-shock performance is classified as one of the most important design specifications. Traditionally, the product reliability against mechanical shock is confirmed by empirical method in the design-prototype-drop/impact testredesign paradigm. The method is time-consuming and expensive process. It lacks scientific insight and quantitative evaluation. In this article, a systematic design evaluation of TFT-LCD module for mobile IT devices is presented with combinations of FEA and testing to support the optimal shock proof display design procedure.

• Transactions of Materials Processing
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• v.22 no.1
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• pp.23-29
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• 2013

In this study, a micro/nano-random-pattern-structure surface was machined by electric discharge machining (EDM) followed by replicating the EDM surface with a silicone elastomer having low energy and greater hydrophobicity. The variation of hydrophobicity was of prime interest and was examined as a function of the surface roughness of the replicated silicone elastomer. The hydrophobicity was evaluated by the water contact angle (WCA) measured on the relevant surface. For the experiments, the original surfaces were machined by die sinking electric discharge machining (DS-EDM) and wire cutting electric discharge machining (WC-EDM). The ranges of surface roughness were Ra $0.8{\sim}19{\mu}m$ for the DS-EDM and Ra $0.5{\sim}4.7{\mu}m$ for the WC-EDM. In order to fabricate a hydrophobic surface, the EDM surfaces were directly replicated using a liquid-state silicone elastomer, which was thermally cured. The measured WCA on the replicated surfaces for DS-EDM was in the range of $115{\sim}130^{\circ}$ and for WC-EDM the WCA was in the range of $123{\sim}150^{\circ}$. Additionally, the dynamic hydrophobicity was evaluated by measuring an advancing and a receding WCA on the replicated silicone elastomer surfaces.

• Journal of Welding and Joining
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• v.34 no.1
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• pp.75-81
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• 2016

This study applied laser surface melting process using CW(Continuous wave) Yb:YAG laser and cold-work die steel SM45C and investigated microstructure and hardness. Laser beam speed, power and beam interval are fixed at 70 mm/sec, 2.8 kW and $800{\mu}m$ respectively. Depth of Hardening layer(Melting zone) was a minimum of 0.8 mm and a maximum of 1.0 mm that exceeds the limit of minimum depth 0.5 mm applying trimming die. In all weld zone, macrostructure was dendrite structure. At the dendrite boundary, Mn, Al, S and O was segregated and MnS and Al oxide existed. However, this inclusion didn't observe in the heat-affected zone (HAZ). As a result of interpreting phase transformation of binary diagram, MnS crystallizes from liquid. Also, it estimated that Al oxide forms by reacting with oxygen in the atmosphere. The hardness of the melting zone was from 650 Hv to 660 Hv regardless of the location that higher 60 Hv than the hardness of the HAZ that had maximum 600 Hv. In comparison with the size of microstructure using electron backscatter diffraction(EBSD), the size of microstructure in the melting zone was smaller than HAZ. Because it estimated that cooling rate of laser surface melting process is faster than water quenching.

• Korean Journal of Medicinal Crop Science
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• v.19 no.6
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• pp.446-455
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• 2011

Galgeun-tang (GGT) is a traditional medicinal formula that is widely prescribed to treat cold, asthma, and hives in Korea. Fermented herbal medicines can be made more effective than normal herbal medicines by increasing the absorption and bioavailability of the active compounds. In this study, we fermented Galgeun-tang to produce bioconversion constituents using Lactobacillus plantarum (GGT144), and found that four peaks were decreased, three peaks were increased and two new peaks appeared in the HPLC-DAD chromatogram. After HPLC-DAD-guided fractionation of the newly-appearing compounds (1 and 5) and the increased (6, 7, and 9) compounds, the structure of the compounds was determined using NMR and MS. Using this approach the compounds were identified to be pyrogallol (1), daidzein (5), liquiritigenin (6), cinnamyl alcohol (7), and formononetin (9), respectively. In addition, the decreased compounds were identified to be daidzin (2), liquiritin (3), ononin (4), and cinnam aldehyde (8) using HPLC-DAD analysis with standard compounds. The high performance liquid chromatography method was used to quantify the nine constituents in GGT and GGT144. All calibration curves of the standard compounds displayed excellent linearity with a $R^2$ > 0.9968.

• Korean Journal of Materials Research
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• v.13 no.11
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• pp.737-741
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• 2003

Polycrystalline $Ti_{l-x}$ $Co_{x}$ $O_2$thin films on $SiO_2$ (200 nm)/Si (100) substrates were prepared using liquid-delivery metalorganic chemical vapor deposition. Microstructures and ferromagnetic properties were investigated as a function of doped Co concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature, and the magnetic and structural properties strongly depended on the Co distribution, which varied widely with doped Co concentration. The annealed $Ti_{l-x}$ $Co_{x}$ $O_2$thin films with $x\leq$0.05 showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are only attributed to the X$l-x_{l-x}$ $Co_{x}$X$O_2$phases. On the other hand, in case of thin films above x = 0.05, Co-rich clusters formed in a homogeneous $Ti_{l-x}$ $Co_{x}$ $O_2$phase, and the overall ferromagnetic (FM) properties depended on both FMTCO and FMCo. Co-rich clusters with about 10-150 nm size decreased the value of Mr (the remanent magnetization) and increased the saturation magnetic field.