• Bulletin of the Korean Chemical Society
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• 제27권8호
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• pp.1145-1148
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• 2006

Excitability is one of the basic and fundamental mechanisms utilized for signal transmission in living organisms. With reference to the condition by Marek and the condition by Schneider, we found a condition in which excitability with similar shapes can appear by chemical and electric perturbation. Our condition is constructed with 3 chemical channels and 1 electric channel, and can be used as a condition for a chemical spiking neuron and as a unit of a chemical spiking neural network.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.589-593
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• 2007

재생 가능한 자원인 동식물성 기름을 원료로 제조되는 수송용 연료 바이오디젤은 낮은 대기오염물질 배출과 $CO_2$ Neutral 특성으로 환경친화적인 연료로 인정을 받으며 전세계적으로 그 생산량이 급격히 증가하고 있다. 대부분의 상용화 공정은 염기촉매를 이용한 전이에스테르화 반응에 근거하고 있으며 높은 생산성을 위해 연속 공정을 채택하고 있다. 원료유 중의 유리지방산(free fatty acid, FFA)은 염기 촉매와 반응하여 지방산염(Soap)과 수분을 생성하며 반응촉매의 투입양을 증가시카고 반응 후에 글리세롤과 지방산 메틸에스테르와의 분리를 어렵게 만든다. 높은 수율과 후속공정의 부하를 줄이기 위해서는 식물성 원료유 중의 FFA는 고체 산촉매 하에서 메탄올과 에스테르화 반응시켜 전환 제거되어야 한다. 본 연구에서는 고체산 촉매인 Amberlyst-15을 충전한 4단 PBR(Packed Bed Reactor, 충전율 60%(v/v))에서 반응시간과 반응온도에 따른 대두원유의 전처리 효율을 조사하였으며 최적 전처리 조건을 도출하였다. 최적 전처리 조건에서 대두원유는 초기 산가 1.6에서 0.4-0.6으로 연속 전처리할 수 있었다. 본 연구에서는 연속 흐름 반응기인 PFR(Plug Flow Reactor)와 4단 CSTR(Continuous Stirred Tank Reactor)에서 균질계 촉매인 KOH 존재하에 대두유와 메탄올과의 전이에스테르화 반응 특성을 조사하였으며 각 연속 반응시스템에서 최적 운전 조건을 도출하였다. PFR 반응기에서 반응온도, 반응시간, 반응물 흐름방향, static mixer(SM) 개수에 따른 반응특성을 조사한 결과, PFR에서의 최적 반응조건은 하향류 흐름 방향과 3개의 SM를 설치한 조건에서 반응시간 5.8분, 반응온도 90$^{\cdot}C$, 메탄올:오일 몰비 9:1, KOH 농도 0.8%로 도출되었다. CSTR 반응기에서는 반응온도와 체류시간에 따른 반응특성을 조사하였으며 최적반응 조건으로 반응온도 80$^{\cdot}C$, 메탄올/오일 몰비 9:1, KOH 농도 0.8%, 체류시간 18.4분, 교반속도 250rpm로 조사되었다.

• Journal of Microbiology and Biotechnology
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• 제25권10호
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• pp.1670-1679
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• 2015

Two hollow fiber membrane biofilm reactors (HF-MBfRs) were operated for autotrophic nitrification and hydrogenotrophic denitrification for over 300 days. Oxygen and hydrogen were supplied through the hollow fiber membrane for nitrification and denitrification, respectively. During the period, the nitrogen was removed with the efficiency of 82-97% for ammonium and 87-97% for nitrate and with the nitrogen removal load of 0.09-0.26 kg NH₄⁺-N/m³/d and 0.10-0.21 kg NO₃^--N/m³/d, depending on hydraulic retention time variation by the two HF-MBfRs for autotrophic nitrification and hydrogenotrophic denitrification, respectively. Biofilms were collected from diverse topological positions in the reactors, each at different nitrogen loading rates, and the microbial communities were analyzed with partial 16S rRNA gene sequences in denaturing gradient gel electrophoresis (DGGE). Detected DGGE band sequences in the reactors were correlated with nitrification or denitrification. The profile of the DGGE bands depended on the NH₄⁺ or NO₃^- loading rate, but it was hard to find a major strain affecting the nitrogen removal efficiency. Nitrospira-related phylum was detected in all biofilm samples from the nitrification reactors. Paracoccus sp. and Aquaspirillum sp., which are an autohydrogenotrophic bacterium and an oligotrophic denitrifier, respectively, were observed in the denitrification reactors. The distribution of microbial communities was relatively stable at different nitrogen loading rates, and DGGE analysis based on 16S rRNA (341f /534r) could successfully detect nitrate-oxidizing and hydrogen-oxidizing bacteria but not ammonium-oxidizing bacteria in the HF-MBfRs.

• Korean Chemical Engineering Research
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• 제44권5호
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• pp.520-527
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• 2006

본 연구에서는 FC(fluorocarbon) 플라즈마 반응기에서 입사하는 이온에너지에 따른 고분자 증착, 식각과 증착의 경쟁반응 및 물리적 스퍼터링 등의 여러 표면 현상들을 모델링하였다. $SiO_2$ 식각에 대한 표면반응은 식각반응 영역을 잘 혼합된 CSTR(continuous stirred tank reactor) 가정을 도입하여 이온 도움에 의한 식각으로 모사되었다. 정상상태 고분자층을 통한 식각과 증착의 경쟁반응의 모델링은 이온 도움에 의한 고분자 생성 및 분해 메커니즘을 제안하여 수행하였다. 이러한 메커니즘은 최근 발표된 실험 및 분자동력학적 전산모사 결과에 기초하였으며,모델 계수들은 빔실험 결과 및 플라즈마 실험결과들을 이용하여 구하였다. 최종 개발된 모델의 결과들은 타당성을 검증하기 위해 문헌에 보고된 실험결과들과 비교하였다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.493-500
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• 2003

The effect of reductive treatment with elemental iron on the extent of mineralization by Fenton oxidation was studied for the explosive 2,4,6-trinitrotoluene (TNT) and hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX) using a completely-stirred tank reactor (CSTR). The results support the hypothesis that TNT and RDX are reduced with elemental iron to products that are oxidized more rapidly and completely by Fenton's reagent. Iron pretreatment enhanced the extent of TOC removal by approximately $20\%\;and\;60\%$ for TNT and RDX, respectively. Complete TOC removal was achieved for TNT and RDX solutions with iron pretreatment under optimal conditions. On the other hand, without iron pretreatment, complete mineralization of TNT and RDX solutions were not achieved even with much higher $H_2O_2$ and $Fe^{2+}$ concentrations. The bench-scale iron treatment-Fenton oxidation integrated system showed more than $95\%$ TOC removal for TNT and RDX solutions under optimal conditions. The proposed zero-valent iron-Fenton process was evaluated with pink water from the Iowa Army ammunition plant. Results from batch and column experiments show that TNT, RDX, and octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine (HMX) were completely removed from the pink water and that triaminotoluene (TAT) and ${NH_4}^+$ were recovered as products in reduction with zero-valent iron. By using an integrated system, $83.3\pm4.2\%$ of TOC was removed in a CSTR with 10 mM of $Fe^{2+}$ and 50 mM of $H_2O_2$. These results suggest that the reduction products of TNT and RDX are more rapidly and completely mineralized by Fenton oxidation and that a sequential iron treatment-Fenton oxidation process may be a viable technology for pink water treatment.

• 한국응용과학기술학회지
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• 제24권4호
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• pp.436-443
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• 2007

Anaerobic reductive dehalogenation of perchloroethene (PCE) was studied with lactate as the electron donor in a continuously stirred tank reactor (CSTR) inoculated with a mixed culture previously shown to dehalogenate vinyl chloride (VC). cis-1,2- dichloroethene (cDCE) was the dominant intermediate at relatively long cell retention times (>56 days) and the electron acceptor to electron donor molar ratio (PCE:lactate) of 1:2. cDCE was transformed to VC completely at the PCE to lactate molar ratio of 1:4, and the final products of PCE dehalogenation were VC (80%) and ethene (20%). VC dehalogenation was inhibited by cDCE dehalogenation. Propionate produced from the fermentation of lactate might be used as electron donor for the dehalogenation. Batch experiments were performed to evaluate the effects of increased hydrogen, VC, and trichloroethene (TCE) on VC dehalogenation which is the rate-limiting step in PCE dehalogenation The addition of TCE increased the VC dehalogenaiton rate more than an increase in the $H_2$ concentration, which suggests that the introduction of TCE induces the production of an enzyme that can comtabolize VC.

• KSBB Journal
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• 제20권2호
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• pp.100-105
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• 2005

탈질화 균주인 Paracoccus denitrificans를 이용한 탈질화 공정에 있어서 탈질 효율의 증대를 위해 선행 연구를 바탕으로 화학적 permeabilization 처리 후 균주를 고정화시키는 방법을 이용하였다. 반응기는 이상적인 CSTR을 도입하여 free cell reactor와 immobilized cell reactor 그리고 permeabilized and immobilized cell reactor의 세 가지 형태의 실험을 실시하였으며, 탈질효율의 비교를 위해 M-M 식을 적용시켰다. 각 반응기의 체류시간에 따른 탈질 효과는 permeabilized and immobilized cell reactor가 가장 우수하였으며 또한 반응 평형에도 다른 두 반응기에 비해 빨리 도달하는 것으로 나타났다.

• 자원리싸이클링
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• 제16권5호
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• pp.65-70
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• 2007

자극-반응(stimulus-response method)법을 이용하여 1단과 다단 혼합침강형 추출장치의 물질흐름특성을 규명하기 위한 실험을 수행하였다. 실험 결과, 1단 추출장치의 혼합조의 반응특성은 CSTR과 동일한 결과를 나타내었으며 혼합-침강조의 반응특성에서는 시간 지연 효과가 나타나며, 단수가 증가할수록 시간지연효과는 증가하였다. 1단과 다단 추출장치의 반응특성 실험결과를 RTD모델 해석프로그램인 K-RTD를 이용하여 분석하여 1단 및 다단 추출기의 RTD을 개발하였다. 본 연구에서 개발한 1단 및 다단 혼합침강조형 추출기의 RTD 모델에 의한 계산값과 실험값에 대한 상관 계수는 각각 0.963과 0.995로 비교적 높은 것을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1428-1431
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• 1997

This paper presents an efficient fault diagnosis methodology for lare chemical processes. The methodology is based on a two-tier strategy, When a falt occurs in a process, a top tier identifies the sector (process part or unit) that may contain the fault(s). Afterwards, a bottom tier or lower level evaluates the suspicious sector. The process modeling methodology based on functionality-behavior relations of process units, is proposed and utilized in the top-tier. This methodology models a target process as sequences of functions and variables and their relations. In the bottom tier, each sector has a dedicated diagostic module, which is tailored to the available information or models of the sector. For the sectors selected in the top-tier diagnosis, each diagnostic module is executed to identify the actual faults within the sector. Teh utility of the methodology is illustrated in the diagnosis of the CSTR with heat exchanger.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.309-312
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• 1997

The dynamic characteristics of a continuous MMA/MA free-radical solution copolymerization reactor were studied. A mathematical model was developed and kinetic parameters which had been estimated in the previous work were used. With this model, bifurcation diagrams were constructed with various parameters as the bifurcation parameter to predict the region of stable operating conditions and to enhance the controller performance. It was shown that the steady-state multiplicity existed over wide ranges of residence time and jacket inlet temperature. Periodic solution branches were found to emanated from Hopf bifurcation points. Under certain conditions isola was also observed, which would result in poor performance of feedback controllers.