• Bulletin of the Korean Chemical Society
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• 제8권5호
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• pp.414-418
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• 1987

Electrochemical reduction of dibenzoylmethane was studied on mercury electrode by means of cyclic voltammetry, polarography and potentiostatic measurements in ethanol-water system. In acidic solutions monomeric pinacol was produced by irreversible two-electron process while monomeric and dimeric pinacol were competitively produced by the same process in neutral solution. However, in basic solution the dimeric pinacol was mostly produced through radical by irreversible one-electron transfer process. Mechanisms of the reduction of dibenzoylmethane are deduced from Tafel slope, pH dependance and reaction order with respect to the concentration of dibenzoylmethane in the solution of various pH.

• 환경생물
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• 제23권4호
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• pp.390-397
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• 2005

The inhibition of cell recovery might be proceeded via either the damage of the mechanism of the recovery itself or via the formation of irreversible damage which could not be repaired at all. Both these processes may take place at the same time. Any of these possibilities would result in a decrease in both the rate and extent of cell recovery. To distinguish them, a quantitative approach describing the process of recovery as a decrease in the effective radiation dose was applied to experimental data on the recovery from potentially lethal damage in Chinese hamster cells exposed to X-rays alone or combined with various chemicals (pyruvate, novobiocin, lactate, nalidixic acid, 3-aminobenzamide). For these particular cases, it is concluded that the recovery process itself is not damaged and the inhibition of the recovery is entirely due to the enhanced yield of the irreversibly damaged cells.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1999년도 춘계 학술발표회 논문집
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• pp.151-157
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• 1999

원심 펌프내 3차원 유동 특성을 고찰하기 위하여 혼류형 원심펌프의 내부유동특성을 수치적 고찰하였다. 회전차 내의 유동현상에 대한 상세한 해석과 이해는 원심펌프의 주요 요소들에 대한 성능 예측에 있어 매우 중요하다. 회전차 내부의 유동은 3차원 점성효과가 지배적이기 때문에 펌프 성능에 중대한 영향을 준다. 회전차내의 3차원 점성유동은 주 영역인 등엔트로피 유동과 원심력과 Coriolis힘에 의한 경계층의 변화, 벽면의 전단응력, 2차 유동(secondary flow)등의 영향에 의한 비가역 영역으로 구분한다. 저 운동량 영역을 만드는 회진차 내부의 점성 유동은 정체영역(blockage)과 실속(stall)이라는 비가역 영역을 만들게 되는데, 결과적으로 펌프의 성능과 효율저하를 유발시킨다. 특히 Coriolis힘과 원심력은 비가역 영역을 증대시키는 가장 큰 힘이라는 사실을 알았다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.266-266
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• 2013

We show a set-up of poly (4,4'-aminotriphenylene hexafluoroisopropylidenediphthalimide) (6F-TPA PI)/Al sample in which holes are injected by photoelectron emission process instead of direct charge carrier injection via metal electrode. In this process, an irreversible electrical phase transition of 6F-TPA PI is found in contrast to the Al/6F-TPA PI/Al structure, leading to a write-once-readmany behavior. The photoelectron spectroscopy results measured before and after the switching process revealed that the irreversible electrical phase transition of 6F-TPA PI is attributed to the chemical modification of the carbonyl group in phthalimide moiety.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.244-244
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• 2012

Polymer memory devices have attracted considerable attention because of their advantages such as low cost potential, good scalability, flexibility, simplicity in structure, and large capacity for data storage. Metal/poly (4,4'-aminotriphenylene hexafluoroisopropylidenediphthalimide) (6F-TPA PI)/metal system has been found to show an electrical bi-stable behavior. Here, we show a novel set-up of 6F-TPA PI/Al sample in which holes are injected by photoelectron emission process instead of direct charge carrier injection via metal electrode. In this process, an irreversible electrical phase transition of 6F-TPA PI is found, leading to a write-once-read-many (WORM) behavior. The photoelectron spectroscopy results measured before and after the switching process revealed that the irreversible electrical phase transition of 6F-TPA PI is attributed to the chemical modification of the carbonyl group in phthalimide moiety.

• 상하수도학회지
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• 제19권1호
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• pp.38-46
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• 2005

In this research, we tried to combine the coagulation/sedimentation process as pre-treatment with UF membrane filtration to reduce the membrane fouling and to improve the permeate water quality. We used the Jet Mixed Separator (JMS) as coagulation/sedimentation process. We observed that the HPC and E.Coli can't be removed through the direct UF memebrane filtation of surface water. The removal efficiency of dissolved organic substances, indicated by E260 and DOC, was 40% and 15%, respectively. However, the removal efficiency of it increased two time as a result of combination of JMS process as coagulation/sedimentation pre-treatment. This was resulted from the formation of high molecular humic micro-floc through JMS process. The accumulation amount of irreversible cake layer which was not removed by backwashing was less than direct UF membrane filtration of surface water. Moreover, the loading rate of fouling induced substances, such as humic substances and suspended substances, on membrane surface decreased drastically through JMS process. As a result, the accumulation amount of irreversible cake on membrane surface was decreased.

• Korean Chemical Engineering Research
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• 제60권2호
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• pp.217-222
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• 2022

고분자 전해질 연료전지(PEMFC) 고분자 막의 전기화학적 내구성을 가속적으로 평가하는 개회로 전위 유지(OCV holding) 과정에서 OCV 변화 거동을 해석하는 것은 매우 중요하다. 본 연구에서는 내구성이 각기 다른 세 종류의 MEA(membrane electrode assembly)의 실험데이터를 이용한 실험식을 만들어 비교 및 검토하였다. 막 내부에 라디칼 제거제가 없는 강화막 MEA의 내구 평가시간은 383 h, 막 내부에 라디칼 제거제가 있는 강화막 MEA의 내구 평가시간은 각각 1,000, 1,650 h이었다. 고분자 막의 열화는 활성화에 의해 회복이 가능한 가역적 열화와 회복이 되지 않은 비가역적 열화로 구분했다. 고분자 막의 비가역적 열화는 수소투과도 증가로 나타나는데 수소투과도 변화가 세 MEA 모두 비가역적 열화 상수 c와 유사한 형태를 보였다. 회복이 되지 않은 비가역적 열화가 시작되는 것은 수소투과도 증가로 나타나고, 수소투과도 증가로 인해 OCV가 회복되지 않아서 OCV 회복선의 기울기가 감소하고 이를 실험식의 상수 c 값의 증가로 확인할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제10권6호
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• pp.600-604
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• 1989

In order to find the rational methods for improving the thermal stability of subtilisin Carlsberg, the mechanisms of irreversible thermoinactivation of the enzyme were studied at $90^{\circ}C.$ At pH 4, the main process was hydrolysis of peptide bond. This process followed first order kinetics, yielding a rate constant of $1.26\;{\times}\;10^{-1}h^{-1}$. Hydrolysis of peptide bond of PMS-subtilisin occurred at various sites, which produced new distinct fragments of molecular weights of 27.2 KD, 25.9 KD, 25.0 KD, 22.3 KD, 19.0 KD, 17.6 KD, 16.5 KD, 15.7 KD, 15.0 KD, 13.7 KD, and 12.7 KD. Most of the new fragments originated from the acidic hydrolysis at the C-side of aspartic acid residues. However 25.0 KD, 15.7 KD, and 13.7 KD which could not be removed in purification steps stemmed from the autolytic cleavage of subtilisin. The minor process at pH 4 was deamidation at asparagine and/or glutamine residues and some extend of aggregation was also observed. However, the aggregation was main process at pH 7 with a first order kinetic constant of $16 h^{-1}.$ At pH 9, the main process seemed to be combination of deamidation and cleavage of peptide bond.

• 경영과학
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• 제11권1호
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• pp.39-50
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• 1994

Carousel systems can be classified into unidirectional and bidirectional carousel, depending on the hardware structure. Bidirectional carousels again can be classified into reversible and irreversible carousel, depending on whether the reversal of direction is allowed or not during the process of an order. In this study, single carousel served by one operator is considered. Analytical models for the rotation distance to process an order of size are developed for unidirectional and irreversible bidirectional cases. For reversible bidirectional and Nearest Neighbor Heuristic cases, simulation results of the average rotation distance are presented. Since the throughput capacity of carousel systems also depends upon the picking time of the operator; order size; and the rotation speed of carousel, the model considers the above three factors to express the throughput capacity of single carousel systems.

• 대한설비공학회지:설비저널
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• 제16권3호
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• pp.305-314
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• 1987

Thermodynamic analysis of a mixed refrigerant refrigeration cycle has been performed by computing thermodynamic properties of various refrigerants. The analyses are carried cut to identify the sources and distribution of the energy degradation by irreversible processes. Heat exchange process with the surroundings produces the entropy and the irreversible loss can be reduced by the mixed refrigerant whose phase change temperature varies during the phase change processes in the evaporator and the condenser. The concept has been applied to find the minimum compression work and thus the minimum energy loss in the overall system, specifically in the case of the mixed refrigerant of R12 and R114. Parametric studies have been added to recognize the various factors affecting the system performance.