• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.350-354
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• 2018

Lifetime study of blue phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes was carried out to understand the dominant degradation process during electrical operation of the devices. Doping concentration dependence of the phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes was studied, which demonstrated long lifetime at low doping concentration in the phosphorescent devices and at high doping concentration in the thermally activated delayed fluorescent devices. Detailed mechanism study of the two devices described that triplet-triplet annihilation is the main degradation process of phosphorescent organic light-emitting diodes, whereas triplet-polaron annihilation is the key degradation factor of the thermally activated delayed fluorescent devices.

• 한국터널공학회:학술대회논문집
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• 한국터널공학회 2005년도 학술발표회 논문집
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• pp.251-258
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• 2005

In this study, a new concept for simulating a long-term mechanical degradation mechanism of shotcrete in tunnels has been proposed. In fact, it is known that the degradation takes place mainly by internal cracks and reduced stiffness, which results mainly from volume expansion of shotcrete and corrosion of cement materials, respectively. This degradation mechanism of shotcrete in tunnels appears similar to those of the most kinds of chemical reactions in tunnels. Therefore, the mechanical degradation induced by a kinds of chemical reaction was generalized and mathematically formulated in the framework of thermodynamics. The numerical model was implemented to a 3D finite element code, which can be used to simulate behaviour of shotcrete structures undergoing external forces as well as chemical degradation in time. A number of illustrative examples were given to show the feasibility of the model in tunnel designs with consideration of long-term degradation effect of shotcrete quantitatively for increase of long-term safety of tunnels.

• Parasites, Hosts and Diseases
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• 제44권2호
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• pp.127-131
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• 2006

The furcocercus cercariae of Neodiplostomum seoulense (Digenea: Neodiplostomidae) penetrate the skins of tadpoles and shed their tails. The speculated mechanism of this tail loss was physical efforts required to produce a vigorous zigzag motion during skin penetration; no other mechanism has been proposed. We examined the relationship between the host serum and cercarial tail loss. Cercariae of N. seoulense were collected from experimentally infected Segmentina hemisphaerula, and lots of 300 cercariae were cultured in medium 199 contained several types of sera. Cercarial tail degradation was induced in all media, but all the cercariae cultured except those cultured in media containing fetal bovine serum (FBS) died within 48 hr. After 72 hr cultivation in media containing FBS, cercarial tail degradation was induced in 67.0%; in continuous cultivation 13.3% of larvae survived for 7 days. Tail degradation did not occur in the absence of serum and when serum was heat inactivated at $56^{\circ}C$ for 30 min. The addition of 20 mM ethylenediaminetetraacetic acid (EDTA) blocked cercarial tail degradation completely. Moreover, the addition of 20 mM $MgCl_2$ restored tail degradation blocked by EDTA. These results suggest that the alternative complement pathway is related with the N. seoulense cercarial tail degradation induced by serum.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.833-838
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• 2012

The thermal degradation products of polytrimethylene terephthalate (PTT) obtained by heating the sample in the temperature range of $250-360^{\circ}C$ under non-oxidative conditions was characterized using MALDI-TOF (matrix assisted laser desorption/ionization) mass spectrometry. The structures of the degradation products were determined and the relative compositions were estimated. The MALDI-TOF mass spectra of the thermally degraded PTT sample showed three main series of oligomer products with different end groups, which were carboxyl/carboxyl, carboxyl/allyl, and allyl/allyl. In contrast to the thermal degradation of polyethylene terephthalate (PET), the oligomers containing terephthalic anhydrides were not detected, whereas the formation of oligomers containing the unsaturated allyl ester group was confirmed by mass assignment. From these results, it was concluded that the thermal degradation of PTT proceeds exclusively through the ${\beta}$-CH hydrogen transfer mechanism, which is in accordance with the proposed reaction mechanism for the thermal degradation of polybutylene terephthalate (PBT).

• 한국동물학회지
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• 제32권2호
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• pp.134-141
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• 1989

본 연구는 온열처리에 의한 세포치사의 mechqnism을 밝히기 위해서 heat sensitizer인 low pH와 heat protector인 glycerol을 이용하여 cell lethlity와 단백질의 분해 kinetics를 검토한 것이다. 41-45도씨의 온열처리 중에서 41도씨를 제외한 전 온도범위에서 sensitizer와 protector의 효과가 뚜렷이 나타났으며, protector이 효과는 cell lethality와 단백질분해 모두에서 sensitizer의 효과에 비해서 현저히 나타나서 sensitizer와 protector의 작용기작은 서로 다를 것으로 생각되었다. 즉, 43-44도씨에서 cell inactivation energy는 정상, low pH, glycerol 상태에서 각각 239, 190, 317 kcal/mole의 값을 보였다. 단백질분해 kinetics의 경우에도 대체적인 경향성은 cell inactivation kinetics와 유사하였으나, 직접적인 연관성은 발견할 수 없었다. 이와 같은 결과로 미루어 볼 때, cell lethality와 단백질 분해의 mechanism 사이에 직접적인 관계는 없고, 주로 막단백질로 추정되는 단백질의 inactivation에 의한 세포내 환경의 변화에 의해서 2차적으로 세포치사가 일어나는 것으로 추정할 수 있으며, 정확한 mechanism을 밝히기 위해서는 DNA polymerase를 비롯한 몇가지 가능한 표적에 대한 연구가 이루어져야 할 것으로 사료된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.433-436
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• 1998

Hot carrier induceed the performance degradation of sense amplifier circuit in DRAM has been measured and analyzed using 0.8.mu.m CMOS process. Simulation and experimental results show that the degradation of the MOS devices affects the decrease of the half-Vcc, voltage gain and the increase of the sensing voltage gain and the increase of the sensing voltage. The dominant degradation mechanism is the capacitance imblance in the bit-line pair. We carried out the spice simulation to investigate the degradation of the sense amplifier circuit.

• 대한전기학회논문지
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• 제43권7호
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• pp.1121-1127
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• 1994

The accelerated degradation phenomena in amorphous silicon thin film transistors due to both electrical stress and visible light illumination under the elevated temperature have been investigated systematically as a function of gate bias, light intensity, and stress time. It has been found that, in case of electrical stress, the thrshold voltage shifts of a-Si:H TFT's may be attributed to the defect creation process at the early stage, while the charge trapping phenomena may be dominant when the stressing periods exceed about 2 hours. It has been also observed that the degradation in the device characteristics of a-Si:H TFT's is accelerated due to multiple stress effects, where the defect creation mechanism may be more responsible for the degradation rather than the charge trapping mechanism.

• 약학회지
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• 제31권5호
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• pp.280-285
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• 1987

There are three plausible bioconversion pathways in biodegradation mechanism of capsaicinoids; first, side chain degradation through $\omega$-hydroxylation and $\beta$-oxidation, secondly, aromatic ring hydroxylation, and lastly, hydrolysis on the acidaraide linkage. In microbes, it was reported that capsaicin and its synthetic, analog, nonoylvanillylamide(NVA), could be metabolized to N-vanillylcarbamoylbutyric acid via $\omega$-hydroxylation and consecutive $\beta$-oxidations by Aspergillus niger. In order to broaden the scope of microbial degradation of capsaicinoids, over thirty strains of various fungi including Aspergillus, Penicillum, Mycotypha, Gliocladium, Paecilomyces, Byssoclamys, Conidiobolus, Thamnidium, and Entomophthora. It was observed that almost all the strains examined oxidized, the side chain of capsaicids as A. niger did. These observations strongly support the notion that side chain degradation is the most dominant pathway in the microbial degradation of capsaicinoids.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.138-144
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• 2000

원자력발전소 분기관에 설치되어 있는 6" swing check valve 중 일부에서 seat 면이 다소 손상되어 O/H 기간중에 시트면 연마정비 또는 밸브 교체정비를 수행하였다. 본 논문에서는 실험적 및 이론적 연구를 통하여 밸브 시트면 손상 원인을 분석하였으며, 분석 결과 구조공진 및 음향공진의 복합적인 작용에 의한 밸브 chattering이 손상 원인임을 규명하였다.

• 한국염색가공학회지
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• 제29권4호
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• pp.181-194
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• 2017

The biodegradability of polylactic acid(PLA) fabrics was evaluated by two methods: enzyme and soil degradation. Three different enzymes were selected to evaluate. Degradation times were measured at optimal enzyme treatment conditions. Biodegradation by enzymatic hydrolysis was compared with soil degradation. As a result, biodegradation created cracks on the fiber surface, which led to fiber thickening and shortening. In addition, new peak was observed at $18.5^{\circ}$ by degradation. Moreover, cracks indicating biofragmentation were confirmed by enzyme and soil degradation. By enzyme and soil degradation, the weight loss of PLA fabrics was occurred, there through, the tensile strength decreased about 25% by enzyme hydrolysis when 21 days after, and 21.67% by soil degradation when 60 days after. Furthermore, the biodegradability of PLA fabrics by enzymatic and soil degradation was investigated and enzymatic degradation was found to be superior to soil degradation of PLA fabrics. Among the three enzymes evaluated for enzymatic degradation, alcalase was the most efficient enzymes. This study established the mechanism of biodegradation of PLA nonwovens, which might prove useful in the textile industry.