• Fire Science and Engineering
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• v.32 no.5
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• pp.15-21
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• 2018

This study examined the growth characteristics and carbonization pattern when a fire occurs due to a flammable liquid sprinkled on a vinyl floor. When acetone was sprinkled on a floor, the flame reached its peak in approximately 0.2 s after it was ignited. The lower part of the flame showed a laminar pattern while the upper part showed a turbulent pattern. The pattern showed a turbulent pattern and generated white smoke. The combustion completed floor surface showed carbonization of a dim pore pattern. In the case of benzene, an intense flame was formed in approximately 0.6 s after ignition. The flame length was measured to be approximately 50 mm. When the flame became weak, a significant amount of black smoke was generated due to incomplete combustion. The combustion completed floor surface showed carbonization of a pour pattern and splash pattern. In the case of alcohol, an intense flame was formed in approximately 1.1 s after ignition. In addition, the depth of carbonization was significant where the flammable liquid was collected and a trace of carbonization was observed at the boundary of the flow path of the flammable liquid.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.105-110
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• 2011

The doping procedure in crystalline silicon solar cell fabrication usually contains oxygen injection during drive-in process and removal of phosphorous silicate glass(PSG). In this paper, we studied the effect of oxygen injection and PSG on conversion efficiency of solar cell. The mono crystalline silicon wafers with $156{\times}156mm^2$, $200{\mu}m$, $0.5-3.0{\Omega}{\cdot}cm$ and p-type were used. After etching $7{\mu}m$ of the surface to form the pyramidal structure, the P(phosphorous) was injected into silicon wafer using diffusion furnace to make the emitter layer. After then, the silicon nitride was deposited by the PECVD with 80 nm thickness and 2.1 refractive index. The silver and aluminium electrodes for front and back sheet, respectively, were formed by screen-printing method, followed by firing in 400-425-450-550-$880^{\circ}C$ five-zone temperature conditions to make the ohmic contact. Solar cells with four different types were fabricated with/without oxygen injection and PSG removal. Solar cell that injected oxygen during the drive-in process and removed PSG after doping process showed the 17.9 % conversion efficiency which is best in this study. This solar cells showed $35.5mA/cm^2$ of the current density, 632 mV of the open circuit voltage and 79.5 % of the fill factor.

• Journal of the Korean Solar Energy Society
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• v.33 no.2
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• pp.11-17
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• 2013

Silicon nitride($SiN_x:H$) deposited by radio frequency plasma enhanced chemical vapor deposition(RF-PECVD) is commonly used for anti-reflection coating and passivation in crystalline silicon solar cell fabrication. In this paper, characteristics of the deposited silicon nitride was studied with change of working pressure, deposition temperature, gas ratio of $NH_3$ and $SiH_4$, and RF power during deposition. The deposition rate, refractive index and effective lifetime were analyzed. The (100) p-type silicon wafers with one-side polished, $660-690{\mu}m$, and resistivity $1-10{\Omega}{\cdot}cm$ were used. As a result, when the working pressure increased, the deposition rate of SiNx was increased while the effective life time for the $SiN_x$-deposited wafer was decreased. The result regarding deposition temperature, gas ratio and RF power changes would be explained in detail below. In this paper, the optimized condition in silicon nitride deposition for silicon solar cell was obtained as 1.0 Torr for the working pressure, $400^{\circ}C$ for deposition temperature, 500 W for RF power and 0.88 for $NH_3/SiH_4$ gas ratio. The silicon nitride layer deposited in this condition showed the effective life time of > $1400{\mu}s$ and the surface recombination rate of 25 cm/s. The crystalline silicon solar cell fabricated with this SiNx coating showed 18.1% conversion efficiency.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1018-1021
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• 2006

Powdered metal parts and components may be carburized successfully in a vacuum furnace by combining carburizing technology $VacCarb^{TM}$ with a hi-tech control system. This approach is different from traditional carburizing methods, because vacuum carburizing is a non-equilibrium process. It is not possible to set the carbon potential as in a traditional carburizing atmosphere and control its composition in order to obtain a desired carburized case. This paper presents test results that demonstrate that vacuum carburizing system $VacCarb^{TM}$ carburized P.M. materials faster than traditional steel with acceptable results. In the experiments conducted, PM samples with the lowest density and open porosity showed a dramatic increase in the surface carbon content up to 2.5%C and a 3 times deeper case. Currently the boost-diffusion technique is applied to control the surface carbon content and distribution in the case. In the first boost step, the flow of the carburizing gas has to be sufficient to saturate the austenite, while avoiding soot deposition and formation of massive carbides. To accomplish this goal, the proper gas flow rate has to be calculated. In the case of P.M. parts, more carbon can be absorbed by the part's surface because of the additional internal surface area created by pores present in the carburized case. This amount will depend on the density of the part, the densification grade of the surface layer and the stage of the surface. "as machined" or "as sintered". It is believed that enhanced gas diffusion after initial evacuation of the P.M. parts leads to faster carburization from within the pores, especially when pores are open . surface "as sintered" and interconnected . low density. A serious problem with vacuum carburizing is delivery of the carbon in a uniform manner to the work pieces. This led to the development of the different methods of carburizing gas circulation such as the pulse/pump method or the pulse/pause technique applied in SECO/WARWICK's $VacCarb^{TM}$ Technology. In both cases, each pressure change may deliver fresh carburizing atmosphere into the pores and leads to faster carburization from within the pores. Since today's control of vacuum carburizing is based largely on empirical results, presented experiments may lead to better understanding and improved control of the process.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.1
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• pp.53-60
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• 2014

Different kinds of post-deposition annealing (PDA) by a rapid thermal process (RTP) are used to enhance the field-effect passivation of $Al_2O_3$ film in crystal Si solar cells. To characterize the effects of PDA on $Al_2O_3$ and the interface, metal-insulator semiconductor (MIS) devices were fabricated. The effects of PDA were characterized as functions of RTP temperature from $400{\sim}700^{\circ}C$ and RTP time from 30~120 s. A high temperature PDA can retard the passivation of thin $Al_2O_3$ film in c-Si solar cells. PDA by RTP at $400^{\circ}C$ results in better passivation than a PDA at $400^{\circ}C$ in forming gas ($H_2$ 4% in $N_2$) for 30 minutes. A high thermal budget causes blistering on $Al_2O_3$ film, which degrades its thermal stability and effective lifetime. It is related to the film structure, deposition temperature, thickness of the film, and annealing temperature. RTP shows the possibility of being applied to the PDA of $Al_2O_3$ film. Optimal PDA conditions should be studied for specific $Al_2O_3$ films, considering blistering.

• KSBB Journal
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• v.22 no.6
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• pp.433-437
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• 2007

A constant desire has been to fabricate nanopatterns for biochip and the Ultraviolet-nano imprint lithography (UV-NIL) is promising technology especially compared with thermal type in view of cost effectiveness. By using this method, nano-scale to micro-scale structures also called nanopore structures can be fabricated on large scale gold plate at normal conditions such as room temperature or low pressure which is not possible in thermal type lithography. One of the most important methods in fabricating biochips, immobilizing, was processed successfully by using this technology. That means immobilizing proteins only on the nanopore structures based on gold, not on hardened resin by UV is now possible by utilizing this method. So this selective nano-patterning process of protein can be useful method fabricating nanoscale protein chip.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.65-74
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• 2016

Ship ad-hoc network (SANET) extends the coverage of the maritime communication among ships with the reduced cost. To fulfill the growing demands of real-time services, the SANET requires an efficient clock time synchronization algorithm which has not been carefully investigated under the ad-hoc maritime environment. This is mainly because the conventional algorithms only suggest to decrease the beacon collision probability that diminishes the clock drift among the units. However, the SANET is a very large-scale network in terms of geographic scope, e.g., with 100 km coverage. The key factor to affect the synchronization performance is the signal propagation delay, which has not being carefully considered in the existing algorithms. Therefore, it requires a robust multi-hop synchronization algorithm to support the communication among hundreds of the ships under the maritime environment. The proposed algorithm has to face and overcome several challenges, i.e., physical clock, e.g., coordinated universal time (UTC)/global positioning system (GPS) unavailable due to the atrocious weather, network link stability, and large propagation delay in the SANET. In this paper, we propose a logical clock synchronization algorithm with multi-hop function for the SANET, namely multi-hop clock synchronization for SANET (MCSS). It works in an ad-hoc manner in case of no UTC/GPS being available, and the multi-hop function makes sure the link stability of the network. For the proposed MCSS, the synchronization time reference nodes (STRNs) are efficiently selected by considering the propagation delay, and the beacon collision can be decreased by the combination of adaptive timing synchronization procedure (ATSP) with the proposed STRN selection procedure. Based on the simulation results, we finalize the multi-hop frame structure of the SANET by considering the clock synchronization, where the physical layer parameters are contrived to meet the requirements of target applications.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.10
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• pp.57-60
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• 1971

In this experiment 5 Korean varieties and 3 U.S.A. varieties of wheat were investigated for their moisture content, ash content, crude protein content and extraction rate. The results are summarized as follows; 1. In the case of U.S.A. wheat, the ash content is directly proportional to the content of protein but the extraction rate is negatively correlated to the content of ash. 2. In the case of korean wheat, there is no proportional tendency as in the U.S.A. wheat. It might be cause by the low extraction rate where the endosperm is hardly separated from the bran layer at the same conditions of temering process. 3. The concentration of protein particles in the endospern, is centrifugal in the U.S.A. wheats, but in the Korean varieties the direction is oppositional to the U.S.A. varieties. 4. Yooksung ＃3, Cahngkwang, Youngkwang and Hard winter wheat are adapted to the production of all purpose flour or noodle flour; Noring ＃4, Jinkwang and Softwhite wheat are suitable for the process of cake flour; and Dark northern spring is just adaped to the production of bread flour.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.204-205
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• 2006

In the response to the demand for electrical energy, much effort aimed to develop and commercialize high temperature superconducting (HTS) power equipments has been made around the world. In Korea, companies and universities are developing a power distribution and transmission class HTS transformer that is one of the 21st century superconducting frontier projects. The composite winding of transmission class HTS transformer is concentrically arranged H1-L-H2 from center. H1 is continuous disk type, L is layer type and H3 is continuous disk type. For the development of transmission HTS transformer with composite winding, the cryogenic insulation technology should be established. We have been analyzed insulation composition and investigated electrical characteristics such as breakdown of $LN_2$, barrier, kapton films, surface flashover on FRP in $LN_2$. We are going to compare with measured each value and apply the value to most suitable insulating design of the HTS transformer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.3-4
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• 2006

In this paper, a nickel silicide technology with post-silicidation annealing effect for thin film SOI devices is investigated in detail. Although lower resistivity Ni silicide can be easily obtained at low forming temperature, poor thermal stability and changing of characteristic are serious problems during the post silicidation annealing like ILD (Inter Layer Dielectric) deposition or metallization. So these effects are observed as deposited Ni thickness differently on As doped SOI (Si film 30nm). Especially, the sheet resistance of Ni thickness deposited 20nm was lower than 30nm before the post silicidation annealing. But after the post silicidation annealing, the sheet resistance was changed. Therefore, in thin film SOI MOSFETs or Ni-FUSI technology that the Si film is less than 50nm, it is important to decide the thickness of deposited Ni in order to avoid forming high resistivity silicide.