• Journal of Electrical Engineering and information Science
• /
• v.2 no.5
• /
• pp.65-71
• /
• 1997

We present heterojunction solar cells with a structure of metal/a-Si:H(n-i-p)/poly-Si(n-p)/metal for the terrestrial applications. This cell consists fo two component cells: a top n-i-p junction a-Si:Hi cell with wide-bandgap 1.8eV and a bottom n-p junction poly-Si cell with narrow-bandgap 1.1eV. The efficiency influencing factors of the solar cell were investigated in terms of simulation an experiment. Three main topics of the investigated study were the bottom cell with n-p junction poly-Si, the top a-Si:H cell with n-i-p junction, and the interface layer effects of heterojunction cell. The efficiency of bottom cell was improved with a pretreatment temperature of 900$^{\circ}C$, surface polishing, emitter thickness of 0.43$\mu\textrm{m}$, top Yb metal, and grid finger shading of 7% coverage. The process optimized cell showed a conversion efficiency about 16%. Top cell was grown by suing a photo-CVD system which gave an ion damage free and good p/i-a-Si:H layer interface. The heterojunction interface effect was examined with three different surface states; a chemical passivation, thermal oxide passivation, and Yb metal. the oxide passivated cell exhibited the higher photocurrent generation and better spectral response.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.94-95
• /
• 2007

In this paper, the dependence of electrical characteristics of Silicon-$Al_2O_3$-Nitride-Oxide-Silicon (SANOS) memory cell transistors and program speed, reliability of memory device on interface trap between Si substrate and tunneling oxide was investigated. The devices were fabricated by the identical processing in a single lot except the deposition method of the charge trapping layer, nitride. In the case of P/E speed, it was shown that P/E speed is slower in the SONOS cell transistors with larger interface trap density by charge blocking effect, which is confirmed by simulation results. However, the data retention characteristics show much less dependence on interface trap. Therefore, to improve SANOS memory characteristic, it is very important to optimize the interface trap and charge trapping layer.

• Tribology and Lubricants
• /
• v.30 no.6
• /
• pp.330-336
• /
• 2014

Sintered metallic brake pads and low alloy heat resistance steel disks are applied to mechanical brake systems in high energy moving machines that are associated with recently developed 200km/h trains. This has led to the speed-up of conventional urban rapid transit. In this study, we use a lab-scale dynamometer to investigate the effects of the composition of friction materials on the tribological characteristics of sintered metallic brake pads and low alloy heat resistance steel under dry sliding conditions. We conduct test under a continuous pressure of 5.5 MPa at various speeds. To determine the optimal composition of friction materials for 200 km/h train, we test and the evaluate frictional characteristics such as friction coefficients, friction stability, wear rate, and the temperature of friction material, which depend on the relative composition of the Cu-Sn and Fe components. The results clearly demonstrate that the average friction coefficient is lower for all speed conditions, when a large quantity of iron power is added. The specimen of 25 wt% iron powder that was added decreased the wear of the friction materials and the roughness of the disc surface. However when 35 wt% iron powder was added, the disc roughness and the wear rate of friction materials increased By increasing the amount of iron powder, the surface roughness, and temperature of the friction materials increased, so the average friction coefficients decreased. An oxidation layer of $Fe_2O_3$ was formed on both friction surfaces.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.7 no.3
• /
• pp.62-73
• /
• 2008

In this paper, domestic standard revision plan of dynamic frequency method which is used both in unmanned automatic toll collection system and manned collection system of the express highway is presented. For such ETCS, the infrared rays (870 nm) of active frequency method and the frequency integrated method (5.8 GHz) are adopted and extended to be operated to the all around the Toll Gate. This standardization plan is based on inter connection reference model between OSI (Open System Interconnection) in process of ITS short range radio communication standardization of 5.8 GHz bandwidth to support traffic information and control system service, and the derived revision plan by starting from physical layer which support interoperability for multiple access between RSE (Road Side Equipment) and OBE (On Board Equipment), in which is categorized into physical layer, data link layer, and application layer. In case of radiation power, existing standard is divided by class1 (within 10 m) and Class2 (within 100 m) according to transmission lengthwhile it is operated with just single standard 'Class1' because of notification of Ministry of Information and Communication in 2004. In the case of the limitation value of incident power in communication area, considering operation plan of ETCS that is on actuality operation the measurements are reflected to the standard. In other wort this paper proposed the improvement standard of incident power, pseudo response in the communication area and radiated power in order to secure stability and compatibility among operator systems about the needed part on ETCS operation.

• Fire Science and Engineering
• /
• v.33 no.6
• /
• pp.120-125
• /
• 2019

A real-scale combustion test was conducted on a vinyl flooring in a divided space, with 50 mL of an inflammable liquid sprayed on it. The combustion behavior of the vinyl flooring was studied in real time, and the carbonization patterns of the surface and cross-sections of the carbonized vinyl floor were analyzed. When the flame ignited by gasoline reached its peak, a continuously flaming region, intermittent flaming region, plume region, etc., were formed. The combustion of 50 mL gasoline on vinyl flooring took 26 s, and a halo pattern was observed. This test involved spraying kerosene evenly on the vinyl flooring and attempting to ignite the flooring using a gas torch, which failed. After the combustion of the vinyl flooring was complete, its carbonized range was measured to be 600 mm in length and 380 mm in width, and the carbonized area was 1000 ㎟. Heat transformed the coated layer of surface of the carbonized vinyl flooring into a carbonized layer, which became harder. The analysis of cross-section of the boundary surface of the carbonized vinyl flooring using a stereoscopic microscope showed that the vinyl flooring was bubbling, and that the white boundary layer at the bottom of the coated layer had disappeared.

• Proceedings of the KIEE Conference
• /
• 1995.07c
• /
• pp.1137-1139
• /
• 1995

$SiN_x$ films deposited on bare Si and wet-etched Si by RPCVD were fabricated to investigated the effect of wet-etched surface of Si on the characteristics of the interface between $SiN_x$ and Si. FT-IR spectra on each film showed similar characteristics. However, it was confirmed that the electric characteristics(I-V, C-V) of the interface between $SiN_x$ and Si have been degraded by the wet etching process of Si, which is applied for the formation of Si field emitter array. Therefore, we suggest that the stacked structure of insulating layer with good interface characteristics is desirable for FED application.

• Laser Solutions
• /
• v.16 no.4
• /
• pp.7-11
• /
• 2013

The surface oxidation of magnesium was performed by Plasma electrolytic oxidation treatment method. And the optical reflectance spectra of the oxidation layers are studied. In the PEO process, the growth of the oxide layer take place at room temperature. Surface roughness of the obtained result, the average surface roughness is $0.08{\mu}m$ difference. The reason seems to the influence of the $Na^+$.

• Korean Journal of Food Science and Technology
• /
• v.9 no.4
• /
• pp.313-316
• /
• 1977

The patterns of saponins of lateral gingengs cultivated different areas and various ginseng products were investigated by quantitative thin-layer chromatography. In the case of ginseng cultivated in the Kum San and Gang Hwa area, some parts of the panaxatriol series of the saponins (peak 6 and 7.8.9) were higher in concentration than in ginseng grown in other areas while the other ingredients were almost the same. In the process of heat treatment the quantity of peak 2 was generally decreased. However, in the case of red and white ginseng, one part of the panaxatriol saponins, peak 6 was increased. This tendency was also found in honeyed ginseng and ginseng tea which were not exposed to sunlight, but the increase was much less. The change in the red and white ginseng which were exposed to sunlight was very substantial. Therefore we can assume that the increase of peak 6 comes about due to the combination of heat treatment and exposure to sunlight, especially due to exposure to sunlight.

• Journal of Sensor Science and Technology
• /
• v.23 no.5
• /
• pp.291-294
• /
• 2014

In this study, a chemiresistive sensor based on one-dimensional $WO_3$ nanostructures is presented for application in non-invasive medical diagnostics. $WO_3$ nanostructures were used as an active gas sensing layer and were deposited onto a $SiO_2/Si$substrate using Pt interdigitated electrodes (IDEs). The IDE spacing was $5{\mu}m$ and deposition was performed using RF sputter with glancing angle deposition mode. Pt IDEs fabricated by photolithography and dry etching. In comparison with thin film sensor, sensing performance of nanostructure sensor showed an enhanced response of more than 20 times when exposed to 50 ppm acetone at $400^{\circ}C$. Such a remarkable faster response can pave the way for a new generation of exhaled breath analyzers based on chemiresistive sensors which are less expensive, more reliable, and less complicated to be manufactured. Moreover, presented sensor technology has the potential of being used as a personalized medical diagnostics tool in the near future.

• Journal of the Korean Society for Railway
• /
• v.12 no.1
• /
• pp.72-80
• /
• 2009

The tribiological characteristics such as friction coefficient, friction stability, wear rate and braking temperature between various types of metallic friction materials and heat resistant steel disk, were investigated by using lab-scale dynamometer. Friction materials for high speed train have higher friction coefficient and friction stability as compared to aircraft friction materials even though friction materials for high speed train have lower wear rate. In addition. Cu-matrix friction materials have higher temperature increase rate than Fe-matrix friction materials. All friction surfaces have Fe-base oxide layer after completing test.