• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.215-218
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• 2015

Simultaneous laser ignition and spectroscopy is a scheme that enables rapid determination of the local equivalence ratio and condensed fuel concentration during a reaction in a two phase spray flame. We have conducted quantitative analysis of the LIBS signals according to the equivalence ratio, droplet size, droplet number density and droplet concentration as a part of novel feedback control strategy proposed for flame ignition and stabilization with simultaneous in situ combustion flow diagnostics. This is a desirable scheme since such real time information onboard an engine for instance can be constantly monitored and fed back to the control loop to enhance the mixing process and minimize emissions of unwanted species and potential combustion instability.

• Journal of the Semiconductor & Display Technology
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• v.16 no.2
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• pp.75-78
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• 2017

We reports improved monitoring performance of Self plasma-optical emission spectroscopy (SP-OES) by augmenting a by-pass tube to a conventional straight (or single) tube type self plasma reactor. SP-OES has been used as a tool for the monitoring of plasma chemistry indirectly in plasma process system. The benefits of SP-OES are low cost and easy installation, but some semiconductor industries who adopted commercialized SP-OES product experiencing less sensitivity and slow sensor response. OH out-gas chemistry monitoring was performed to have a direct comparison of a conventional single type tube and a by-pass type tube, and fluid dynamic simulation on the improved hardware design was also followed. It is observed faster pumping out of OH from the chamber in the by-pass type SP-OES.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.2
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• pp.20-27
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• 2022

Hypergolic propellant ignited spontaneously when fuel and oxidizer contact without ignition system. Due to this characteristic, the risk of accidents is high when new propellants are evaluated. Prevention of accidents is very important because the damage can be large when the accident occur. In this work, we proposed non-ignition evaluation method which can replace conventional ignition evaluation method by using microreactor. The reactor was fabricated by MEMS. The heat of reaction as according to fuel and NaBH₄ was estimated. At the condition of highest heat of reaction ignition was observed by drop test.

• Journal of Surface Science and Engineering
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• v.48 no.4
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• pp.163-168
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• 2015

Graphene has attracted much attention due to its remarkable physical properties and potential applications in many fields. In special, the electronic properties of graphene are influenced by the number of layer, stacking sequence, edge state, and doping of foreign elements. Recently, many efforts have been dedicated to alter the electronic properties by doping of various species, such as hydrogen, oxygen, nitrogen, ammonia and etc. Here, we report our recent results of plasma doping on graphene. We prepared mechanically exfoliated graphene, and performed the plasma treatment using ammonia gas for nitrogen doping. The direct-current plasma system was used for plasma ignition. The doping level was estimated from the number of peak shift of G-band in Raman spectra. The upshift of G-band was observed after ammonia plasma treatment, which implies electron doping to graphene.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1994.11a
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• pp.21-26
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• 1994

Conventional electroexplosive devices (EED) commonly use a very small metal bridgewire to ignite explosive materials i.e. pyrotechnics, primary and secondary explosives. The use of semiconductor devices to replace “hot-wire” resistance heating elements in automotive safety systems pyrotechnic devices has been under development for several years. In a typical 1 amp/1 watt electroexplosive devices, ignition takes place a few milliseconds after a current pulse of at least 25 mJ is applied to the bridgewire. In contrast, as for a SCB devices, ignition takes place in a few tens of microseconds and only require approximately one-tenth the input energy of a conventional electroexplosive devices. Typically, when SCB device is driven by a short (20 $\mu\textrm{s}$), low energy pulse (less than 5 mJ), the SCB produces a hot plasma that ignites explosive materials. The advantages and disadvantages of this technology are strongly dependent upon the particular technology selected. To date, three distinct technologies have evolved, each of which utilizes a hot, silicon plasma as the pyrotechnic initiation element. These technologies are 1.) Heavily doped silicon as the resistive heating initiation mechanism, 2.) Tungsten enhanced silicon which utilizes a chemically vapor deposited layer of tungsten as the initiation element, and 3.) a junction diode, fabricated with standard CMOS processes, which creates the initial thermal environment by avalanche breakdown of the diode. This paper describes the three technologies, discusses the advantages and disadvantages of each as they apply to electroexplosive devises, and recommends a methodology for selection of the best device for a particular system environment. The important parameters in this analysis are: All-Fire energy, All-Fire voltage, response time, ease of integration with other semiconductor devices, cost (overall system cost), and reliability. The potential for significant cost savings by integrating several safety functions into the initiator makes this technology worthy of attention by the safety system designer.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.295-296
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• 2006

Prototype NBI(Neurtal Beam Injector), which Is tested at KAERI(Kaeri Atomic Energy Research Instutide), is the facility for tokamak plasma Ignition of the advanced nuclear fusion KSTAR(Korea Superconducting Tokamak Advanced Research). New NBI facility, which is the part of KSTAR tokamak, will be constructed during next three years. This investigation is focused on the preliminary test to construct the control system for KSTAR NBI, before KSTAR NBI facility is constructed.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.495-504
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• 2015

This work investigated the characteristics of a packed-bed plasma reactor system and the performances of the plasma reactors connected in series or in parallel for the decomposition of ethylene. Before the discharge ignition, the effective capacitance of the ${\gamma}$-alumina packed-bed plasma reactor was larger than that of the reactor without any packing, but after the ignition the effective capacitance was similar to each other, regardless of the packing. The energy of electrons created by plasma depends mainly on the electric field intensity, and was not significantly affected by the gas composition in the range of 0~20% (v/v) oxygen (nitrogen : 80~100% (v/v)). Among the various reactive species generated by plasma, ground-state atomic oxygen and ozone are understood to be primarily involved in oxidation reactions, and as the electric field intensity increases, the amount of ground-state atomic oxygen relatively decreases while that of nitrogen atom increases. Even though there are many parameters affecting the performance of the plasma reactor such as a voltage, discharge power, gas flow rate and residence time, all parameters can be integrated into a single parameter, namely, specific input energy (SIE). It was experimentally confirmed that the performances of the plasma reactors connected in series or in parallel could be treated as a function of SIE alone, which simplifies the scale-up design procedure. Besides, the ethylene decomposition results can be predicted by the calculation using the rate constant expressed as a function of SIE.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.550-551
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• 2013

Large-area RF-driven ion source is being developed at Germany for the heating and current drive of ITER plasmas. Negative hydrogen (deuterium) ion sources are major components of neutral beam injection systems in future large-scale fusion experiments such as ITER and DEMO. RF ion sources for the production of positive hydrogen ions have been successfully developed at IPP (Max-Planck- Institute for Plasma Physics, Garching) for ASDEX-U and W7-AS neutral beam injection (NBI) systems. In recent, the first NBI system (NBI-1) has been developed successfully for the KSTAR. The first and second long-pulse ion sources (LPIS-1 and LPIS-2) of NBI-1 system consist of a magnetic bucket plasma generator with multi-pole cusp fields, filament heating structure, and a set of tetrode accelerators with circular apertures. There is a development plan of large-area RF ion source at KAERI to extract the positive ions, which can be used for the second NBI (NBI-2) system of KSTAR, and to extract the negative ions for future fusion devices such as ITER and K-DEMO. The large-area RF ion source consists of a driver region, including a helical antenna (6-turn copper tube with an outer diameter of 6 mm) and a discharge chamber (ceramic and/or quartz tubes with an inner diameter of 200 mm, a height of 150 mm, and a thickness of 8 mm), and an expansion region (magnetic bucket of prototype LPIS in the KAERI). RF power can be transferred up to 10 kW with a fixed frequency of 2 MHz through a matching circuit (auto- and manual-matching apparatus). Argon gas is commonly injected to the initial ignition of RF plasma discharge, and then hydrogen gas instead of argon gas is finally injected for the RF plasma sustainment. The uniformities of plasma density and electron temperature at the lowest area of expansion region (a distance of 300 mm from the driver region) are measured by using two electrostatic probes in the directions of short- and long-dimension of expansion region.

• Journal of the Korean Vacuum Society
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• v.20 no.5
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• pp.322-326
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• 2011

Etch process of silicon dioxide layer by using capacitively coupled plasma (CCP) is currently being used to manufacture semiconductor devices with nano-scale feature size below 50 nm. In typical CCP plasma etcher system, plasmas are generated by applying the RF power on upper electrode and ion bombardment energy is controlled by applying RF power to the bottom electrode with the Si wafer. In this case, however, etch results often drift due to heating of the electrode during etching process. Therefore, controlling the temperature of the upper electrode is required to obtain improvement of etch repeatability. In this work, we report repeatability improvement during the silicon dioxide etching under extreme process conditions with very high RF power and close gap between upper and bottom electrodes. Under this severe etch condition, it is difficult to obtain reproducible oxide etch results due to drifts in etch rate, critical dimension, profile, and selectivity caused by unexpected problems in the upper electrode. It was found that reproducible etch results of silicon dioxide layer could be obtained by controlling temperature of the upper electrode. Methods of controlling the upper electrode and the correlation with etch repeatability will be discussed in detail.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.712-721
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• 2015

Pulse Detonation Engine (PDE) has been considered as a future propulsion system for broad range of operation and higher thermal efficiency. Various subsystem technologies have been studied for more than decade to improve the performance of the potential system. New valve systems has been developed for the stable operation at high frequency including inflow-driven valve, rotary valve and valveless system. To foster the detonation initiation with a little ignition energy, plasma ignition method and DDT (deflagration to detonation transition) acceleration method such as swept ramp mechanism have been studied. Fluidic nozzle system and other nozzle system are the ongoing research topics to maximize the propulsion performance of the PDE. Present paper introduces the state of the art of PDE subsystem technologies developed in recent years.