Study of I layer deposition parameters of deposited micro-crystalline silicon by PECVD at 27.12MHz

이기세(Lee, Kise),김선규(Kim, Sunkue),김선영(Kim, Sunyoung),김상호(Kim, Sangho),김건성(Kim, Gunsung),김범준(Kim, Beomjoon) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06

Microcrystalline silicon at low temperatures has been developed using plasma enhanced chemical vapor deposition (PECVD). It has been found that energetically positive ion and atomic hydrogen collision on to growing surface have important effects on increasing growth rate, and atomic hydrogen density is necessary for the increasing growth rate correspondingly, while keeping ion bombardment is less level. Since the plasma potential is determined by working pressure, the ion energy can be reduced by increasing the deposition pressure of 700-1200 Pa. Also, correlation of the growth rate and crystallinity with deposition parameters such as working pressure, hydrogen flow rate and input power were investigated. Consequently an efficiency of 7.9% was obtained at a high growth rate of 0.92 nm/s at a high RF power 300W using a plasma-enhanced chemical vapor deposition method (27.12MHz).

A Simple Model for TCP Loss Recovery Performance over Wireless Networks

Kim, Beomjoon,Lee, Jaiyong The Korea Institute of Information and Commucation 2004 Journal of communications and networks Vol.6 No.3

There have been a lot of approaches to evaluate and predict transmission control protocol (TCP) performance in a numerical way. Especially, under the recent advance in wireless transmission technology, the issue of TCP performance over wireless links has come to surface. It is because TCP responds to all packet losses by invoking congestion control and avoidance algorithms, resulting in degraded end-to-end performance in wireless and lossy systems. By several previous works, although it has been already proved that overall TCP performance is largely dependent on its loss recovery performance, there have been few works to try to analyze TCP loss recovery performance with thoroughness. In this paper, therefore, we focus on analyzing TCP's loss recovery performance and have developed a simple model that facilitates to capture the TCP sender's behaviors during loss recovery period. Based on the developed model, we can derive the conditions that packet losses may be recovered without retransmission timeout (RTO). Especially, we have found that TCP Reno can retransmit three packet losses by fast retransmits in a specific situation. In addition, we have proved that successive three packet losses and more than four packet losses in a window always invoke RTO easily, which is not considered or approximated in the previous works. Through probabilistic works with the conditions derived, the loss recovery performance of TCP Reno can be quantified in terms of the number of packet losses in a window.

A Simple Model for TCP Loss Recovery Performance over Wireless Networks

Beomjoon Kim,이재용 한국통신학회 2004 Journal of communications and networks Vol.6 No.3

Loss Recovery Modeling of TCP Reno over Wireless Links

Beomjoon Kim,Dongmin Kim,Jechan Han,Jaiyong Lee 에스케이텔레콤 (주) 2003 Telecommunications Review Vol.13 No.5

In this paper, we investigate the loss recovery behavior of TCP Reno over wireless links where packets are not always lost due to network congestion. Loss recovery of TCP Reno operates based on two basic algorithms of fast retransmit and fast recovery. We derive the conditions for successful loss recovery of TCP Reno by modeling the window variation during loss recovery accurately. Based on the developed model, the fast retransmit probability of TCP Reno is derived when the pattern of packet losses are random and correlated. Therefore, the performance of TCP Reno can be evaluated from the aspect of the fast retransmit probability. Main findings of our work are 1) loss recovery function of TCP Reno is not effective when multiple packets are lost in a window. 2) Continuity of packet losses as well as packet loss probability can affect the fast retransmit probability. We explain some of these observations in terms of the variation of the average window size and packet loss probability.

4-Octyl-4 -(5-carboxy-pentamethylene-oxy)azobenzene과 Dilauroyl-L-α- Phosphayidylcholine의 혼합 LB막의 전기화학적 특성

김범준(Kim BeomJoon),민병철(Min ByoungChul),박근호(Park KeunHo) 한국유화학회 2002 한국응용과학기술학회지 Vol.19 No.1

We carried out this experiment to observe electrochemical properties for LB films of phospholipid(Dilauroyl-L-alpha-Phosphayidylcholine) and 4-octyl-4 -(5-carboxypentamethylene-oxy)azobenzene mixture by the cyclic voltammetry. LB films of 8A5H and 8A5H-DLPC(1:1, 2:1) were deposited by using the Langmuir-Blodgett method on the ITO glass. We determined electrochemical measurement by using cyclic voltammetry with a three-electrode system, An Ag/AgCl reference elect rode, a platinum wire counter electrode and LB film-coated ITO working electrode measured in 0.1, 0.5, and 1.0 mol/L NaClO4 solution. A measuring range was reduced from initial potential to -1350 mV, continuously oxidized to 1650 mV and measured to the initial point. The scan rate were 50, 100, 150 and 200 mV/s. As a result, LB films of 8A5H 8A5H-DLPC appeared irreversible process caused by only the oxidation current from the cyclic voltammogram.

금융투자자 보호를 위한 가상자산(Virtual Assets)의 법제화 방안

김범준(Kim Beomjoon),이채율(Lee Chaeyul) 한국법학회 2021 법학연구 Vol.81 No.-

우리나라는 전세계 가상자산 거래 국가 154개국 중 거래 수신량에서 3위를 차지할 만큼 큰 규모를 갖춘 시장 중 하나로서 거래량, 거래대금에서 의미있는 지표를 보유하고 있다. 현재 국내에서 운영되고 있는 가상자산거래소는 77개 이상이며, 거래 가능한 가상자산도 260개를 넘어가고 있다. 특히, 가상자산과 관련된 사업을 진행하는 국내 기업은 금융업이 7개, IT 서비스업 및 통신업이 6개 등으로 15개 이상일 것으로 추정된다. 이렇듯 국내 가상자산 거래 시장은 2017년 비트코인 열풍이 시작된 이래로 계속하여 성장해 나가고 있다. 그러나 정부와 금융당국은 가상자산을 규제하기 위한 법적 근거를 마련하기보다는 해킹, 개인정보유출, 투자사기 등 실제 이용자의 피해가 발생하자 후속조치로 가상자산 공개(ICO) 전면금지, 거래실명제 도입, 자금세탁방지 가이드라인 등을 제시하였다. 즉, 가상자산에 대한 선제적인 규제 정비가 아닌 사후적 정책 대응으로 인해 실제 거래에서 이용자들은 적절한 법적 보호를 받지 못하고 있는 것으로 생각된다. 이후 2020년 3월, 국제자금세탁방지기구(FATF)의 가상자산 규제 권고안을 반영한 「특정 금융거래정보의 보고 및 이용 등에 관한 법률」의 개정을 통해 가상자산에 대한 정의 규정을 신설하고, 가상자산사업자에게 여러 의무를 부과하였으나 그 내용이 자금세탁방지에만 국한되어 있어 투자자 보호를 위한 제도적 배려가 여전히 미비한 실정인 것으로 보인다. 반면, 해외 주요국은 가상자산이 향후 일반적인 상거래 및 금융거래에서 상용화될 수 있는 잠재력을 지니고 있음을 감안하여 가상자산 전반에 대한 제도정비를 완료해 나가고 있는 추세이다. 즉, 선제적 대응으로 가상자산을 기존의 제도권으로 포섭하고, 관련 산업의 발전 계획 및 투자자 보호 체계를 구축한 것이다. 따라서 전세계 가상자산 시장에서 유의미한 거래 규모를 보이고 있는 우리나라의 현행 가상자산 관련 법제를 살펴보고, 해외 주요국의 규제 동향 분석을 통해 국내에 적합한 투자자 보호 방안을 마련하는 것은 디지털 경제로의 변환기에 대응해야 할 현시점에서 의미 있는 작업이 될 것으로 생각된다. 이에 본고에서는 우선 가상자산의 법적 특성을 살펴보고, 국내 최초로 가상자산에 대해 정하고 있는 「특정 금융거래정보의 보고 및 이용 등에 관한 법률」을 검토하였다. 이후, 가상자산 산업선도국가인 미국, 영국 및 스위스의 규제 동향 분석을 바탕으로 가상자산의 유형별 분류를 통한 금융 규제 및 투자자 보호를 주요 내용으로 하는 「가상자산 산업 발전 및 이용자 보호에 관한 법률(가칭)」의 제정필요성을 도출하여 국내 가상자산 거래 시장이 건전하게 성장할 수 있는 방향을 제시하는데 기여하고자 한다. Korea is one of the largest markets in the world, ranking the third in transaction reception among 154 virtual asset trading countries, and has meaningful indicators such as trading volume and transaction price. Currently, there are more than 77 Virtual Asset Exchanges are being operated in Korea, and the number of virtual assets that can be traded exceeds 260. In particular, the number of domestic companies involved in virtual asset-related businesses is expected to be seven in the financial industry, six in IT services and communications, and more than 15 in total. The domestic virtual asset transaction market has been growing since the start of the Bitcoin boom in 2017. However, the Korean governments and authorities have not established definitions and legal grounds on virtual assets. Several guidelines were presented as follow-up measures when actual damage such as hacking, personal information leakage, and fraud occurred. In other words, it is believed that users in actual transactions did not receive adequate legal protection due to a late policy response rather than a preemptive regulatory overhaul of virtual assets. 2020, The revised 「Act on Reporting and Utilization of Specified Financial Transaction Information」, which reflects the FATF’s Virtual Asset Recommendation, established a new definition of virtual assets and virtual asset business operators and imposed obligations on virtual asset business operators equivalent to financial companies. However, the content is limited to the prevention of money laundering, and institutional considerations for the protection of investors are still insufficient. On the other hand, major foreign countries have completed institutional maintenance of virtual assets as a whole, expecting that they have the potential to be commercialized in general financial transactions in the near future. That is, virtual assets were incorporated into existing legal institutions, and related industry development plans and financial investor protection schemes were established. Therefore, it is a meaningful task at this time to respond to the transition to the digital economy by examining Korea’s current virtual asset-related legislation and analyzing regulatory trends in major foreign countries. In response, this article focuses on the nature of virtual assets and on the 「Act on Reporting and Utilization of Specified Financial Transaction Information」. Based on the analysis of virtual asset regulation trends in the U.S., the U.K., and Switzerland, it is necessary to establish a law on the 「Development and Protection of the Virtual Asset Industry」, which focuses on effective financial regulation and investor protection.

실험계획법(DOE)을 이용한 실리콘 박막의 전기적 특성 분석

김선규(Kim, SunKue),김선영(Kim, SunYoung),이기세(Lee, KiSe),김범준(Kim, BeomJoon) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06

미니탭(Minitab) 프로그램에 있는 실험계획법(Design of experiment)를 이용하여 박막실리콘 I-layer의 주효과 및 교호작용에 대한 연구를 실시하였다. I-layer의 주요 특성은 증착속도 및 전도도에 대하여 분석을 하였으며, 최종적으로 선택된 증착조건을 사용하여 비정질 실리콘 태양전지를 제조하여 확인 하였다. 실험설계는 2수준 5인자 완전설계요인법을 사용하였다. 분석결과 단막의 증착속도에 영향을 주는 주효과로는 Power와 E/S거리고 나타났으며, Power와 E/S거리, Power와 Pressure에서 큰 교호작용이 일어남을 확인 할 수 있었다. 암전도의 영향을 주는 주효과는 Sub. Temp.를 제외하고는 모두 영향을 주고 있었으며, 상당히 복잡한 교호작용을 이루고 있어 정확한 분석을 할 수는 없었다. 광전도도의 경우도 주효과에서 SiH4 flow rate를 제외하고는 모두 영향을 주고 있었으며, 복잡한 교호작용으로 정확한 분석이 어려웠다. 따라서 P-value를 분석하여 최종 R-제곱값이 증착속도는 97%이상의 높은 값을 얻었으나 전도도의 경우 최대차수 3차항으로 70~80%정도의 낮은 값을 얻었을 수 있었다. 낮은 값을 얻은 이유로는 실험설계시 몇몇 조건이 불안정한 plasma 상태로 인하여 전도도의 측정 편차가 커 분석오차가 높았을 것으로 추정된다. 암전도를 망소특성, 광전도도를 망대특성으로 광민감도 10⁵으로 최적화 하여 비정질 태양전지를 만들어 평가한 결과 약 9%대의 광변환 효율을 얻을 수 있었으나 만족도 40%대의 낮은 값으로 향후 이와 관련한 더 정밀한 측정 및 분석이 요구된다.

준등온 압축 기반 냉방 시스템용 열교환기의 압력 강하 및 유동 분배 특성 수치 해석 연구

김수현(Soohyun Kim),이명성(Myungsung Lee),김주한(Joo-han Kim),이범준(Beomjoon Lee) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

Due to global warming the consumption of energy for cooling is increasing, and developing high-efficiency cooling systems has many issue in this days. Quasi-isothermal compression technology is a high-efficiency cooling technology that continuously removes high-temperature heat when air is compressed by compressor. A heat exchanger is used between the compressor and the expander for an efficient quasi-isothermal compression process. Therefore, it is important to improve the cooling performance of the heat exchanger. The inside of the heat exchanger is composed by multiple channels, and if the internal flow is non-uniform the performance of the heat exchanger is reduced. In this study, the pressure distribution and flow distribution characteristics for each channel were analyzed through numerical analysis of a heat exchanger using a porous media. To verify the simulation method an experiment was conducted to verify the simulation method, and As a result of comparison, the trends of the performance curves was similar.

준등온 압축 기반 냉방 시스템용 열교환기의 압력 강하 및 유동 분배 특성 수치 해석 연구

김수현(Soohyun Kim),이명성(Myungsung Lee),김주한(Joo-han Kim),이범준(Beomjoon Lee) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

Due to global warming the consumption of energy for cooling is increasing, and developing high-efficiency cooling systems has many issue in this days. Quasi-isothermal compression technology is a high-efficiency cooling technology that continuously removes high-temperature heat when air is compressed by compressor. A heat exchanger is used between the compressor and the expander for an efficient quasi-isothermal compression process. Therefore, it is important to improve the cooling performance of the heat exchanger. The inside of the heat exchanger is composed by multiple channels, and if the internal flow is non-uniform the performance of the heat exchanger is reduced. In this study, the pressure distribution and flow distribution characteristics for each channel were analyzed through numerical analysis of a heat exchanger using a porous media. To verify the simulation method an experiment was conducted to verify the simulation method, and As a result of comparison, the trends of the performance curves was similar.

무선 센서 네트워크에서 임계 값을 적용한 에너지 절감방안 연구

김호년(Ho-Nyeon Kim),김동민(Dong-Min Kim),유준재(June-Jae Yoo),송병철(Byoung-Chul Song),김범준(Beomjoon Kim),이재용(Jae-Yong Lee) 한국통신학회 2004 한국통신학회 학술대회 및 강연회 Vol.2004 No.4