• Applied Chemistry for Engineering
• /
• v.18 no.6
• /
• pp.557-561
• /
• 2007

Polypropylene (PP)/corn starch master batch (starch-MB) blends with different PP compositions of 40, 50, 60, and 80 wt% were prepared by melt compounding at $200^{\circ}C$, using lab scale Brabender mixer. The chemical structures and thermal properties of the PP/starch-MB blends were investigated by FT-IR, differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). The chemical structure was confirmed by the existence of hydroxy group. There was no district change in melting temperature and melting enthalpy, and TGA curve indicated a decrease in degradation temperature with starch-MB content. The porosity change of blend was measured by scanning electron microscope (SEM), the degree of porosity on the blend surface increased with the starch-MB content. The rheological properties indicated an increase in complex viscosity, shear thinning tendency and elasticity with the starch-MB concentration. These effects were confirmed by an oscillatory viscometer at $200^{\circ}C$. From these results, it is found that 40 wt% is the optimum starch-MB concentration. The fiber was fabricated from PP60/MB40 with 40 wt% starch-MB and the porosity and tensile properties were investigated.

• Korean Journal of Optics and Photonics
• /
• v.16 no.4
• /
• pp.354-360
• /
• 2005

A high performance LWIR(long wavelength infra red) zoom thermal imaging sensor using $480{\times}6$ HgCdTe(MCT) linear detector has been developed by ADD Korea. The optical system consists of zoom telescope having large objective about 190 mm diameter and optically well corrected scanning system. The zoom ratio of the telescope is 3: 1 and its magnification change is performed by moving two lens groups. And also these moving groups are used for athermalization of the system. It is certain that the zoom sensor can be used in wide operating temperature range without any degradation of the system performance. Especially, the sensor image can be displayed with the HDTV(high definition television) format of which aspect ratio is 16:9. In case of HDTV format, the scanning system is able to display 620,000 pixels. This function can make wider horizontal field of view without any loss of performance than the normal TV format image. The MRTD(minimum resolvable temperature difference) of the LWIR thermal imaging sensor shows good results below 0.04 K at spatial frequency 2 cycles/mrad and 0.23 K at spatial frequency 8 cycles/mrad at the narrow field of view.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.12
• /
• pp.1772-1780
• /
• 2003

An optimal soot blowing system has been developed for an optimal operation of power utility boilers by both minimization of the use of steam and the number of soot blowers worked during soot blowing. Traditionally, the soot blowing system has been operated manually by operators. However, it causes the reduction of power and thermal performance degradation because all soot blowers installed in the plant should be worked simultaneously even there are lots of tubes those are not contaminated by slagging or fouling. Heat transfer area is divided into four groups, furnace, convection area including superheater, reheater and economizer, and air preheater in the present study. The condition of cleanness of the tubes is calculated by several parameters obtained by sensors. Then, a part of soot blowers works automatically where boiler tubes are contaminated. This system has been applied in a practical power plant. Therefore, comparison has been done between this system and manual operation and the results are discussed.

• Advances in aircraft and spacecraft science
• /
• v.1 no.1
• /
• pp.1-14
• /
• 2014

Physico-chemical changes of the plasma modified titanium alloy [Ti-6Al-4V] surface were studied with respect to their crystallographic changes by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM).The plasma-treatment of surface was carried out to enhance adhesion of high performance nano reinforced epoxy adhesive, a phenomenon that was manifested in subsequent experimental results. The enhancement of adhesion as a consequence of improved spreading and wetting on metal surface was studied by contact angle (sessile drop method) and surface energy determination, which shows a distinct increase in polar component of surface energy. The synergism in bond strength was established by analyzing the lap-shear strength of titanium laminate. The extent of enhancement in thermal stability of the dispersed nanosilica particles reinforced epoxy adhesive was studied by Thermo Gravimetric Analysis (TGA), which shows an increase in onset of degradation and high amount of residuals at the high temperature range under study. The fractured surfaces of the joint were examined by Scanning electron microscope (SEM).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.12
• /
• pp.1058-1062
• /
• 2000

We investigated resistive superconducting fault current limites (SFCLs) fabricated using YBCO thin films on 2-inch diameter sapphire substrates. Nearly identical SFCL units were prepared and tested. The units were connected in series and parallel to increase the current and voltage ratings. A serial connection of the units showed significantly unbalanced power dissipation between the units. This imbalance was removed by introducing a shunt resistor to the firstly quenched unit. Parallel connection of the units increased the current rating. An SFCL module of 4 units in parallel, each of which has minimum quench current rating. An SFCL module of 4 units in parallel, each of which has minimum quench current 25 A$\_$peak/, was produced and successfully tested at a 220 V$\_$rms/circuit. From the resistance increase, we estimated that the film temperature increased to 200 K in 5 msec, and 300 K in 120 msec. Successive quenches revealed that this system is stable without degradation in the current limiting capability under such thermal shocks as quenches at 220 V$\_$rms/.

• The Korean Journal of Ceramics
• /
• v.4 no.1
• /
• pp.15-19
• /
• 1998

Defects formation of Chemical Vapor Deposition (CVD) diamond on $^4He^{2+}$ irradiation and after remote hydrogen plasma treatment(RHPT) were investigated by cathodoluminescence(CL). As calculated in the TRIM simulation, the light elements of $^4He^{2-}$ can be penetrated into the diamond bulk structure at 3~4 $\mu\textrm{m}$ depth. The effects of the implantation region were observed when 5 keV~20 keV electron energy (insight 0.3~4.0$\mu\textrm{m}$) of CL measurement was irradiated to diamond at temperature 80 K. After the RHPT, rehybridization of irradiation damaged diamond was studied. The intensity of 5RL center(intrinsic defect of C) was diminished. The 2.16 eV center (N-V center) occurring usually by annealing could not be seen after RHPT. The diamond was rehybridized by hydrogen radicals without etching and thermal degradation by the RHPT.

• Journal of Electrochemical Science and Technology
• /
• v.7 no.1
• /
• pp.33-40
• /
• 2016

Sr_0.92Y_0.08TiO_3-δ (SYT) was investigated as an alternative anode in humidified CH₄ fuel for SOFCs at low temperatures (650 ℃-750 ℃) and compared with the conventional Ni/yttria-stabilized zirconia (Ni/YSZ) anode. The goal of the study was to directly use a hydrocarbon fuel in a SOFC without a reforming process. The cell performance of the SYT anode was relatively low compared with that of the Ni/YSZ anode because of the poor electrochemical catalytic activity of SYT. In the presence of CH₄ fuel, however, the cell performance with the SYT anode decreased by 20%, in contrast to the 58% decrease in the case of the Ni/YSZ anode. The severe degradation of cell performance observed with the Ni/YSZ anode was caused by carbon deposition that resulted from methane thermal cracking. Carbon was much less detected in the SYT anode due to the catalytic oxidation. Otherwise, a significant amount of bulk carbon was detected in the Ni/YSZ anode.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.6
• /
• pp.569-575
• /
• 2011

Since the high heat generation of LED chips can cause a reduction in lifetime, degradation of luminous efficiency, and variation of color temperature, studies have been carried out on the optimization of LED packaging and heat sinks. Recently, LED packages have been applied to high-power lights such as car headlamps or street lights, and it is known that cooling using only free convection is not at all efficient. Thus, in this study, a heat pipe with forced convection was examined for the optimization of the cooling performance in high-power LED lights. In addition, optimal on-off control of a fan was adopted to increase the fan lifetime, since the lifetime of the fan is generally shorter than that of the LEDs.

• 한국초전도학회:학술대회논문집
• /
• v.10
• /
• pp.272-275
• /
• 2000

We investigated a resistive superconducting fault current limiter (SFCL) fabricated using YBCO thin films on 2-inch diameter sapphire substrates. Nearly identical SFCL units were prepared and tested. The units were connected in series and parallel to increase the current and voltage ratings. A serial connection of the units showed significantly unbalanced power dissipation between the units. This imbalance was removed by introducing a shunt resistor to the firstly quenched unit. Parallel connection of the units increased the current rating. An SFCL module of 4 units in parallel, each of which has minimum quench current 25 Ap, was produced and successfully tested at a 220 V circuit. From the resistance increase, we estimated that the film temperature increases to 200 K in 5 msec, and 300 K in 120 msec. Successive quenches revealed that this system is stable without degradation in the current limiting capability under such thermal shocks as quenches at 220 V.

• Journal of Powder Materials
• /
• v.23 no.4
• /
• pp.276-281
• /
• 2016

Carbonyl iron (CI) is successfully incorporated as an additive into a polystyrene (PS) matrix via a highenergy ball milling method, under an n-hexane medium with volume fractions between 1% and 5% for electromagnetic interference shielding applications by the combination of magnetic CI and an insulating PS matrix. The morphology and the dispersion of CI are investigated by field emission scanning electron microscopy, which indicates a uniform distribution of CI in the PS matrix after 2 h of milling. The thermal behavior results indicate no significant degradation of the PS when there is a slight increase in the onset temperature with the addition of CI powder, when compared to the as-received PS pellet. After milling, there are no interactions between the CI and the PS matrix, as confirmed by Fourier transformed infrared spectroscopy. In this study, the milled CI-PS powder is extruded to make filaments, and can have potential applications in the 3-D printing industry.