ATM 망에서 ABR 서비스를 위한 EFCI 스위치와 ER 스위치 간의 상호 운용성 분석

이철효(Cheol-Hyo Lee),조유제(You-Ze Cho) 한국정보과학회 1997 정보과학회논문지 : 시스템 및 이론 Vol.24 No.6

ATM 망에서 전송률 기반의 ABR(Available Bit Rate) 흐름 제어를 위한 스위치는 크게 EFCI(Explicit Forward Congestion Indication) 스위치와 ER(Explicit Rate) 스위치로 구분할 수 있다. EFCI 스위치와 ER 스위치는 서로 다른 전송률 제어 방식을 사용하기 때문에 ATM 망에서 혼용하여 사용할 경우 ABR 서비스 성능의 저하가 발생할 수 있다. 본 논문에서는 ABR 서비스를 위하여 EFCI 스위치와 ER 스위치가 혼용되어 사용될 경우의 상호 운용성을 분석하였다. 이를 위하여 하나의 VC(Virtual Connection) 경로상에 사용되는 ER 스위치의 수와 위치에 따른 ABR 서비스 성능을 송신원의 ACR(Allowed Cell Rate) 변화, 스위치의 큐 길이, throughput과 VC 간의 대역폭 사용의 공평성 관점에서 비교하였다. 시뮬레이션 결과로부터 현재 ATM 포럼의 송수신원 동작이 EFCI 스위치와 ER 스위치 간의 상호 운용면에서는 문제가 없음을 알 수 있었다. 그리고, 하나의 VC가 EFCI 스위치와 ER 스위치를 거쳐 갈 때, ABR 흐름 제어의 성능은 사용된 ER 스위치의 수보다는 위치에 따라 크게 영향을 받음을 알 수 있었다. 또한, 폭주가 발생하는 스위치만 ER 스위치로 시용하여도 모든 스위치가 ER인 경우와 거의 비슷한 성능을 나타냄을 알 수 있었다. 따라서, EFCI 스위치와 ER 스위치를 혼용하는 경우에 ABR 서비스 성능의 개선을 위해서 폭주가 발생할 가능성이 높은 스위치는 반드시 ER 스위치로 사용하는 것이 바람직하다. In A TM networks, switch mechanisms for rate-based ABR flow control can be classified into EFCI(Explicit Forward Congestion Indication) and ER(Explicit Rate) types. Since EFCI and ER switches use different rate control mechanisms, the ABR performance can be degraded when an ATM network consists of EFCI and ER switches. This paper investigated the interoperability issues between EFCI and ER switches for the ABR service. For this purpose, the ABR service performance was compared according to the number and location of ER switches used on a VC(Virtual Connection) path in terms of ACR(Allowed Cell Rate) oscillation of source, queue length of switch, throughput, and fairness of bandwidth allocation among VCs. Simulation results showed that there is no problem ill interoperability between EFCI and ER switches which conform to the source and destination end system behaviors of the ATM Forum. Also, it was shown that the location of ER switches on a VCs path has more critical effects on the ABR performance rather than the number of ER switches used. Moreover, even though only switches at congestion point in network are used as ER, the ABR performance exhibited very similar behaviors to that of all ER switch case. Therefore, in order to improve the ABR performance when EFCI and ER switches are mixed in an ATM network, it would be desirable to use at least the switches with high possibility of being congested as ER.

유류오염토양의 정화기술과 적용사례

이철효,Lee, Cheol-Hyo 한국기술사회 2008 技術士 Vol.41 No.3

The most common soil contaminants are petroleum-based. Hydrocarbons from diesel fuel and gasoline are widespread problems, as are total petroleum hydrocarbon(TPH). There are two distinct classes of soil remediation: in-situ, or on-site, and ex-situ, or off- site. On-site cleanups are often preferred because they are cheaper. On the other hand, excavating a contaminated area and transporting it to a remote site before cleaning it can often be more complete. Ex-situ remediation also has the added bonus of taking the bulk of contaminants off-site before they can spread further. In addition, in-situ situations are limited because only the topside of the soil is accessible.

Cemented Te로부터 고순도 Te 금속의 제조

이철경,이강인,유효신,양동효,하윤철,정구진,손헌준,Lee, Churl-Kyoung,Rhee, Kang-In,Yu, Hyo-Shin,Yang, Dong-Hyo,Ha, Yoon-Cheol,Jung, Gu-Jin,Sohn, Hun-Joon 한국자원리싸이클링학회 1999 資源 리싸이클링 Vol.8 No.5

정수처리에서 pH 저감에 의한 응집효율향상에 관한 연구

이환,이철효,정창규,이윤진,Lee, Hwan,Lee, Cheol-Hyo,Jung, Chang-Gue,Lee, Yoon-Jin 한국환경보건학회 2003 한국환경보건학회지 Vol.29 No.2

This paper reports on a pilot scale comparison of PACS coagulation with and without pH preadjustment. The pH of the water was adjusted with carbon dioxide and sulfuric acid. Process performance was assessed on the basis of total organic carbon(TOC), UV absorbance, turbidity and disinfection by-product(DBP) precursors. Coagulation pH appeared to be a determining factor for maximum NOM removal. The optimum coagulation pH in order to decrease TOC and turbidity were pH 7. Preadjustment of pH 7 increased TOC removal to as much as 43, 47 percent with sulfuric acid and carbon dioxide. Moreover, coagulation at pH 7 caused a reduction in UV$_{254}$, THMFP and HAAFP compared to the baseline coagulation. For preadjustment of pH 7 with carbon dioxide, the percentage of TOC, UV$_{254}$, THMFP and HAAFP shows the reduction rate of 3.8, 0.5, 4.8, 9.4% comparing to the coagulation rendition using sulfuric acid. Acid addition to depress pH during coagulation decrease Langelier Saturation Index(LSI), potentially causing increase corrosion in water distribution systems. LSI for carbon dioxide and sulfuric acid at pH 6 was -2.3, -3.3. Therefore, carbon dioxide was more effective at controlling corrosion than sulfuric acid.

토양세척에 의한 비소 및 중금속 오염토양의 복원

고일원,이철효,이광표,김경웅,Ko Ilwon,Lee Cheol-Hyo,Lee Kwang-Pyo,Kim Kyoung-Woong 한국지하수토양환경학회 2004 지하수토양환경 Vol.9 No.4

음이온 비소와 양이온 아연 및 니켈로 오염된 토양을 산세척으로 복원하기 위해서 토양세척 파일럿 장비를 이용해서 토양의 물성과 산세척 특성 및 미세토양과 용존 오염물의 발생 특성을 고찰하였다. 비소와 아연 및 니켈의 pH $2{\sim}3$에서 산세척시 황산과 인산은 공존 경쟁 음이온의 존재로 비소의 제거 효율을 높였고, 염산은 비소, 니켈, 아연을 동시에 효율적으로 제거하였다. 세척조에서 화학적 용출은 임계체류시간 이상에서 세척 효율이 일정해졌고, 산에 의한 용출 가능한 존재형태는 교환성 및 산화물 결합과 유기성 결합형태, 그리고 부분적으로 잔류형태였다. 오염 토양의 입도에 따른 과립의 토양입자의 토양세척 효율은 높지만, 미세입자($<74{\mu}m$)는 오염물질의 농집 현상이 일어나서 제거효율이 감소했다. 또한, $<149{\mu}m$ 이하의 미세토양을 물리적 입도 분리시 전체 세척효율이 향상되었다. 따라서, 미세토양의 양이 최소가 되고 화학적 용출이 최대가 되는 세척 효율 교차지점에서 화학적 용출과 미세토양의 분리가 토양세척의 증가된 효율을 보여 주었다. In order to remediate soils contaminated with oxyanionic As and cationic Zn and Ni through the pilot-scale acid washing, the effectiveness of acid washing and the properties of contaminated soils, fine soil particle and dissolved contaminants were evaluated. $H_{2}SO_4\;and\;H_{3}PO_4$ washing at pH $2{\sim}3$ enhanced the removal of As by the presence of competitive oxyanions and HCl washing effectively removed simultaneously As, Zn and Ni. The effectiveness of soil washing was little enhanced above the critical reaction time, and the carbonate, Fe/Mn oxide and organic/sulfides associated fraction were dominantly removed. The washing of coarse soil particles was highly efficient, but that of fine soil particles($<74{\mu}m$) was recalcitrant due to the enrichment with contaminants. Moreover, the physical separation of fine particles($<149{\mu}m$) enhanced the overall efficiency of soil washing. Therefore, both chemical extraction and separation of fine soil particles showed the high effectiveness of soil washing in the intersection point to minimize the amount of fine soil particles and to maximize the chemical extraction of contaminants.

지그비 디바이스 프로파일

허재두,이철효,Heo, Jae-Du,Lee, Cheol-Hyo 한국정보통신기술협회 2006 TTA저널 Vol.106 No.-

유기성 영양분 첨가 및 화학적 산화 연계를 통한 유류오염 토양의 생물학적 정화효율 향상에 관한 연구

김국진,오승택,이철효,서상기,강창환,장윤영,Kim, Guk-Jin,Oh, Seung-Taek,Lee, Cheol-Hyo,Seo, Sang-Ki,Kang, Chang-Hwan,Chang, Youn-Young 한국지하수토양환경학회 2008 지하수토양환경 Vol.13 No.3

본 연구는 유류화합물로 오염된 토양의 생물학적 정화효율을 향상시키기 위한 연구로서, 정화목표인 TPH 500 mg/kg을 달성하기 위하여 유기성 영양분과 화학적 산화를 추가적으로 연계 적용하여 생물학적 정화효율의 성능향상 시험을 수행하였다. 경유로 오염된 토양을 대상으로 시험한 결과, 생물학적으로 정화하는 과정에서 무기성 성분(N, P)을 영양분으로 사용하여 정화한 경우에서 보다(정화효율 80.2%) 유기성 영향분인 퇴비와 액분을 사용한 경우가 각각 84.4%, 92.2%로 높은 정화효율을 보여주었다. 난분해성 물질을 함유한 토양의 생물학적 정화과정에서 tailing 현상이 일어나는 기간에 화학적 산화와 생물학적 정화를 병행하였을 때 TPH 농도를 134 mg/kg로 떨어뜨려 정화효율 98.1%를 얻은 반면에 생물학적 정화만 진행한 경우 TPH 1,073 mg/kg로 정화효율 84.7%를 나타내 화학적 산화의 병행처리가 더 효과적임을 알 수 있었다. A biological study was conducted to evaluate the enhancement of landfarming of soil contaminated with petroleum hydrocarbon (TPH) applying organic composite nutrients and a chemical oxidation during bioremediation. The target value of soil TPH after treatment was 500 mg/kg TPH. Addition of an organic compost and liquid swine manure for the removal of soil THP showed higher efficiency as 84.4% and 92.2% respectively than inorganic nutrients of 80.2%. In addition to the removal of non-biodegradable portion of residual hydrocarbons in soil, a chemical oxidation was applied during tailing period of the biological remediation, which showed high remediation efficiency as 98.1% compared with single bioremediation efficiency of 84.7%.

비포화대 오염정화 설계를 위한 공압파쇄 모사 해석

권미선,박은규,이철효,김용성,김남진,Kwon, Mi-Seon,Park, Eun-Gyu,Lee, Cheol-Hyo,Kim, Yong-Seong,Kim, Nam-Jin 한국지하수토양환경학회 2010 지하수토양환경 Vol.15 No.6

Pneumatic fracturing is an emerging tool to enhance the remediation efficiency of contaminated unsaturated zones by injecting high pressure air and inducing artificial fracture networks. Pneumatic fracturing is reported to be well suited for the cases where the contaminated unsaturated zone thickness is less than 5 m as many contaminated domestic sites in Korea. Nevertheless, there have been almost no studies carried out on the site-specific efficiency and the optimized design of pneumatic fracturing considering the unsaturated zone characteristics of Korea. In this study, we employ numerical simulations to compare the efficiency of pneumatic fracturing on the aspect of the site remediation and the porosity improvement at several hypothetic unsaturated zones composed of four typical soil types. According to the simulation results, it is found that the zone with fine grains soil such as clay and silt shows better efficiency than the zone composed of coarse grains in terms of air flow and porosity enhancements. The results imply that pneumatic fracturing may improve the efficiency of site reclamation by jointly or independently applied to the many contaminated sites in Korea.

TNT 오염토의 염기성 가수분해 효율 향상을 위한 최적 운전인자 도출

이환,최재헌,이철효,김주엽,Lee, Hwan,Choi, Jae-Heon,Lee, Cheol-Hyo,Kim, Ju-Yup 한국지하수토양환경학회 2015 지하수토양환경 Vol.20 No.6

Nitro-aromatic Compounds (NACs) of explosives are structurally non-degradable materials that have an adverse effect to humans and ecosystems in case of emissions in natural due to the strong toxicity. In this study, batch test in the laboratory-scale has been conducted to find some process parameters of alkaline hydrolysis by considering the characteristics of NACs which are unstable in a base status and field application evaluation have been performed on the batch test results. Based on the experimental results of both laboratory and pilot-scale test, the optimum conditions of parameters for the alkaline hydrolysis of soils contaminated with explosives were pH 12.5, above the solid-liquid ratio 1 : 3, above the room temperature and 30 minute reaction time. In these four process parameters, the most important influencing factor was pH, and the condition of above pH 12.0 was necessary for high contaminated soils (more than 60 mg/kg). In the case of above pH 12.5, the efficiency of alkaline hydrolysis was very high regardless of the concentrations of contaminated soils. At pH 11.5, the removal efficiency of TNT was increased from 76.5% to 97.5% when the temperature in reactor was elevated from room temperature to 80℃. This result shows that it is possible to operate the alkaline hydrolysis at even pH 11.5 due to increased reaction rate depending on temperature adjustment. The results found in above experiments will be able to be used in alkaline hydrolysis for process improvement considering the economy.

배치형과 연속흐름형에 의한 토양 중 RDX의 아임계 분해특성 비교연구

최재헌,이환,이철효,김주엽,박정훈,조영태,Choi, Jae-Heon,Lee, Hwan,Lee, Cheol-Hyo,Kim, Ju-Yup,Park, Jeong-Hun,Jo, Young-Tae 한국지하수토양환경학회 2015 지하수토양환경 Vol.20 No.6

The purpose of this study is to compare the degradation characteristics by subcritical water of RDX contaminated soil using batch mode and dynamic mode devices. First, upon application of RDX contaminated soil, RDX treatment efficiency was increased with increasing the temperature in both modes. At 150℃, the treatment efficiency was 99.9%. RDX degradation efficiency got higher with lower ratio of solid to liquid. However, the treatment efficiency in the dynamic mode tended to be decreased at a certain ratio of solid to liquid or lower. The treatment efficiency was increased when it took longer time for the reactions in both modes. As the results of analysis on concentration of treated water after subcritical water degradation, the RDX recovery rate of dynamic and batch modes at 150℃ was 10.5% and 1.5%, respectively. However, both modes showed very similar recovery rates at 175℃ or higher. RDX degradation products were analyzed in treated water after it was treated with subcritical water. According to the results, RDX degradation mechanism was mostly oxidation reaction and reduction reaction was partially involved. Therefore, it suggested that most of RDX in soil was degraded by oxidation of subcritical water upon extraction. According to this result, it was found that both batch and dynamic modes were very effectively applied in the treatment of explosive contaminated soil.