저온 플라즈마와 광촉매에 의한 NO/SO_(2) 제거

김동주,김교선 강원대학교 산업기술연구소 2006 産業技術硏究 Vol.26 No.A

In this study, we analyzed the effects of several process variables on the removal efficiencies of NO and SO_(2) by the dielectric barrier discharge process combined with photocatalysts. The TiO_(2) photocatalysts were coated onto the spherical-shaped glass beads as dielectric materials by the dip-coating method to analyze the effects of photodegradation reaction on the NO and SO_(2) removal. As the voltage applied to the plasma reactor increases, or as the pulse frequency of applied voltage increases, the NO and SO_(2) removal efficiencies increase. Also as the residence time increases, or as the initial concentration of NO decreases, the NO and SO_(2) removal efficiencies increase. The higher the amount of TiO_(2) particles coated onto the glass bead is, the larger the surface area of TiO_(2) particles for the photodegradation reaction is and the NO and SO_(2) are removed more quickly by the faster photodegradation reactions.

TEOS/O₂플라즈마 반응기에서 미립자 성장에 대한 실험적 분석

김동주,김교선 江原大學校 産業技術硏究所 2001 産業技術硏究 Vol.21 No.B

A study on the particle growth in TEOS/O2 plasma was performed, and particle size and its distribution was measured by the electrical aerosol analyzer (EAA), light scattering particle size analyzer and the particle size was also determined by SEM, the effects of process variables such as total gas flow rate, reactor pressure, supplied power and initial reactant concentration on the particle growth were investigated. From the EAA results, the particle size distribution is divided into three groups of the cluster size and the small and large size particles. The particle size distribution measured by the light scattering particle size analyzer becomes bimodal, because the cluster size particles smaller than 20nm in diameter cannot be detected by the light scattering particle size analyzer. The size of particles measured by the light scattering particle size analyzer is in good agreements with those by the SEM. Also we could understand that the particle formation is very sensitive to the changes of reactor pressure and reactant concentration. As the total gas flow rate increases, the particle size deceases because of the shorter residence time. As the reactor pressure, or the reactant concentration increases, the particle concentration increases and the particles grow more quickly by the faster coagulation between particles.

실란 펄스 플라즈마 공정에서의 화학농도 변화

김동주,김교선 江原大學校 産業技術硏究所 2005 産業技術硏究 Vol.25 No.A

We investigated numerically the evolutions of several chemical species which are important for film growth and particle generation in the pulsed SiH₄ plasmas. During the plasma-on, the SiH_(x) concentration increases with time mainly by the generation reaction from SiH₄, but, during the plasma-off, decreases because of the hydrogen adsorption reaction. During the plasma-on, the concentrations of negative ions increase with time by the polymerization reactions of negative ions and those become almost zero in the sheath regions because of the electrostatic repulsion. During the plasma-off, the concentrations of negative ions decrease with time by the neutralization reactions with positive ions and some negative ions can diffuse toward the sheath regions because there is no electric field inside the reactor. The polymerized negative ions of higher mass can be reduced successfully by using the pulsed plasma process.

저온 플라즈마와 광촉매에 의한 NO/SO_(2) 제거

김동주,김교선 강원대학교 산업기술연구소 2006 産業技術硏究 Vol.26 No.B

In this study, we analyzed the effects of several process variables on the removal efficiencies of NO and SO_(2) by the dielectric barrier discharge process combined with photocatalysts. The TiO_(2) photocatalysts were coated onto the spherical-shaped glass beads as dielectric materials by the dip-coating method toe analyze the effects of photodegradation reaction on the NO and SO_(2) removal. As the voltage applied to the plasma reactor increases, or as the pulse frequency of applied voltage increases, the NO and SO_(2) removal efficiencies increase. Also an the residence time increases, or as the initial concentration of NO decreases, the NO and SO_(2) removal efficiencies increase. The higher the amount of TiO_(2) particles coated onto the glass bead is, the larger the surface area of TiO_(2) particles for the photodegradation reaction is and the NO and SO_(2) are removed more quickly by the faster photodegradation reactions.

공정 변수 변화에 따른 실란 플라즈마내 음이온 특성

김교선,김동주 江原大學校 産業技術硏究所 1995 産業技術硏究 Vol.15 No.-

We have studied the generation and behavior of negative ions in silane plasmas. The negative ions were formed by homogeneous reaction in silane plasma and the behavior of negative ions were predicted by solving the model equations. The concentration profiles of negative ions were shown as a function of reactor length and time. The effects of process variables such as reactor pressure, flow rate and electrical field strengths on the behavior of negative ions were analyzed.

DeSOx/DeNOx 효율 개선을 위한 펄스 코로나 방전하에서 기체미립자 전환반응의 적용

김동주,최유리,김교선 江原大學校 産業技術硏究所 1998 産業技術硏究 Vol.18 No.-

In this paper, we investigated the post-combustion removal of nitrogen oxide(N0?) and sulfur oxide(S0?) which is based on the gas to particle conversion process by the pulsed corona discharge. Under normal pressure, the pulsed corona discharge produces the energetic free electrons which dissociate gas molecules to form the active radicals. These radicals cause the chemical reactions that convert SO? and NO? into acid mists and these mists react with NH? to form solid particles. Those particles can be removed from the gas stream by conventional devices such as electrostatic precipitator or bag filter. The reactor geometry was coaxial with an inner wire discharge electrode and an outer ground electrode wrapped on a glass tube. The simulated flue gas with SO? and NO? by adding NH? and H?O in the gas stream. We also measured the rmoval efficiency of SO? and NO? in a cylinder type corona discharge reactor and obtained more than 90% of removal efficiency in these experimental conditions. The effects of process variables such as the inlet concentrations of SO?, NH? asnd H?O, residence time, pulse frequencies and applied voltages were investigated.

펄스 코로나 방전 공정에서 탈질, 탈황 효율의 실험적 분석

김성민,김교선 강원대학교 산업기술연구소 2003 産業技術硏究 Vol.23 No.A

In this study, we analyzed NO_2 and SO, removal efficiencies by a pulsed corona discharge process and investigated the effect of several process variables The removal efficiencies of NO and SO_2 were measured changing the process variables of initial concentrations of NO. H_2 0. and NH_3, SO_2. applied voltage. pulse frequency and residence time As the applied voltage or the frequency of applied voltage or the residence time increases, the TO and SO2 removal efficiencies increase. The NO and SO_2 removal efficiencies also increase by the addition of O_2 or H_2 O, or by using the large diameter of the discharge electrode. The experimental results can be used as a basis to design the pulsed corona discharge process to remove NO,, SO, and VOCs.

펄스 SiH₄플라즈마 화학기상증착 공정에서 입자 성장에 대한 펄스 변조의 영향

김동주,김교선 강원대학교 산업기술연구소 2006 産業技術硏究 Vol.26 No.B

We analyzed systematically particle growth in the pulsed SiH_4 plasmas by a numerical method and investigated the effects of pulse modulations (pulse frequencics, duty ratios) on the particle growth. We considered effects of particle charging on the particle growth by coagulation during plasma-on. During plasma-on (t_(on)), the particle size distribution in plasma reactor becomes bimodal (small sized and large sized particles groups). During plasma-off (t_(off)), there is a single mode of large sized particles which is widely dispersed in the particle size distribution. During plasma on, the large sized particles grows more quickly by fast coagulation between small and large sized particles than during plasma-off. As the pulse frequency decreases, or as the duty ratio increases, t_(on) increases and the large sized particles grow taster. On the basis of these results, the pulsed plasma process can be a good method to suppress efficiently the generation and growth of particles in SiH_(4) PCVD process. This systematical analysis can be applied to design a pulsed plasma process for the preparation of high quality thin films.

저온 플라즈마 공정에 의한 효율적인 탈황 탈질 공정 연구

김성민,김교선 한국공업화학회 2003 응용화학 Vol.7 No.2

In this study, we analyzed NO_(x) and So_(x) removal efficiencies by a pulsed corona discharge process and investigated the effect of several process variables. The removal efficiencies of NO and So₂ were measured changing the process variables of initial concentrations of NO, H₂O, and NH₃, SO₂, applied voltage, pulse frequency and residence time. As the applied voltage or the frequency of applied voltage or the residence time increases, the NO and SO₂ removal efficiencies increase. The NO and SO₂ removal efficiencies also increase by the addition of O₂ or H₂O, or by using the large diameter of the discharge electrode. The experimental results can be used as a basis to design the pulsed corona discharge process to remove NO_(x), SO_(x) and VOCs.

무선망에서의 throghput 성능 향상을 위한 개선된 TCP 프로토콜에 대한 고찰

김효선,유혁 高麗大學校附設 컴퓨터科學技術硏究所 1999 JOURNAL OF COMPUTER SCIENCE & ENGINEERING TECHNOLO Vol.1 No.-

최근 무선 통신의 대중화가 증가함에 따라 이동 컴퓨팅 환경에 대한 관심이 나날이 높아 가고 있지만 무선망의 특징을 고려한 프로토콜의 개발은 미흡한 상태이다. 유선망에서 널리 통용되고 있는 TCP는 패킷 손실의 원인을 혼잡(congestion)에 의한 것으로 간주하여 혼잡 제어(congestion control)나 회피(avoidance) 메커니즘을 이용하여 패킷의 회복(recovery)에 적절히 대응하고 있다. 하지만 무선망에서의 패킷 손실은 대부분이 혼잡에 의한 것이 아니라 handoff 시의 disconnection이나 무선망 자체의 높은 bit 에러율에 의한 것이므로, 무선망에 기존의 TCP를 그대로 적용하게 되면 오히려 불필요한 메커니즘 호출로 인한 throughput의 저하를 가져오게 된다. 이런 성능 저하를 해결하기 위하여 무선망에 적합하도록 TCP를 개선하는 움직임이 세계적으로 일어나고 있으며, 이를 크게 단대단 프로토콜, split-connection 프로토콜, 링크 계층 프로토콜[2]로 나눌 수 있다. 본 논문은 이러한 흐름의 여러 가지 대표적인 프로토콜들을 비교·분석하였다. The more popular a wireless communication is, the higher an interest in mobile computing environment is. Reliable transport protocols such as TCP are tuned to perform well in traditional networks where packet losses occur mostly because of congestion. However, networks with wireless link also suffer from significant non-congestion-related losses due to reasons such as bit errors and handoffs. TCP responds to all losses by invoking congestion control and avoidance algorithms, resulting in degraded end-to-end performance in wireless system. We compare and analyze several schemes designed to improve the performance of TCP in such networks. These schemes are classified into three broad categories: end-to-end protocols, split-connection protocols and link layer protocols.