• Journal of Nutrition and Health
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• v.9 no.4
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• pp.54-58
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• 1976

Deterioration of ascorbic acid content is the important factor in the food quality. The degradation of ascorbic acid undergoes as a first-order of reaction in the presence of excess oxygen content. However, under the limited oxygen content, ascorbic acid decomposes as a psudo-first order of reaction. The ascorbic acid, in this study, under the limited dissolved oxygen content in the presesce of iron(III) and copper(II) decomposed as first-order reaction with a little influence in rate constant and the light was an accelerating factor on the ascorbic acid degradation.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.759-767
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• 1995

This paper examines the electrical properties according to a curing time and a corona degradation in epoxy composites which are used for transformers. To consider these phenomena, the electrets were formed by appling high voltages to five kinds of specimens designed according to a constant mixing rate and then TSC(Thermally Stimulated Current) values at the temperature range of -160-200[>$^{\circ}C$] were measured from a series of experiments. The behaviour of carrier and its possible origins in epoxy composites were studied. Various effects of curing time and electric field on epoxy composites were also investigated.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.4
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• pp.173-179
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• 2023

This paper analyzes the time-dependent dielectric breakdown(TDDB) degradation mechanism for each stress region of Peri devices manufactured by 4th generation VNAND process, and presents a complementary lifetime prediction model that improves speed and accuracy in a wider reliability evaluation region compared to the conventional model presented. SiON dielectric nMOSFETs were measured 10 times each under 5 constant voltage stress(CVS) conditions. The analysis of stress-induced leakage current(SILC) confirmed the significance of the field-based degradation mechanism in the low electric field region and the current-based degradation mechanism in the high field region. Time-to-failure(TF) was extracted from Weibull distribution to ascertain the lifetime prediction limitations of the conventional E-model and 1/E-model, and a parallel complementary model including both electric field and current based degradation mechanisms was proposed by extracting and combining the thermal bond breakage rate constant(k) of each model. Finally, when predicting the lifetime of the measured TDDB data, the proposed complementary model predicts lifetime faster and more accurately, even in the wider electric field region, compared to the conventional E-model and 1/E-model.

• Journal of Environmental Science International
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• v.10 no.5
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• pp.359-364
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• 2001

Pseudomanas sp. EL-04J was previously isolated from phenol-acclimated activated sludge. This bacterium was capable of degrading phenol and cometabolizing trichloroethylene (TCE). After precultivation in the mineral salts medium containing phenol as a sole carbon source, Pseudomonas EL-04J degraded 90% of TCE $25 \mu\textrm{M}$ within 20 hours. Thus, phenol-induced Pseudomonas sp. EL-04J cells can bdegrade TCE. Followsing a transient lag period, Pseudomonas sp. EL-04J cells degraded TCE at concentrations of at least $250 \mu\textrm{M}$ with no apparent retardation in rate, but the transformance capacity of such cells was limited and depended on the cell concentration. The degradation rate of TCE followed the Michaelis-Menten kinetic model. The maximum degradation ratio ($V_{max}$) and saturation constant ($K_{m}$) were $7nmo {\ell}/min{\cdot}mg$ cell protein and $11 \mu\textrm{M}$, respectively. Cometabolism of TCE by phenol fed experiment was evaluated in $50m {\ell}$ serum vial that contained $10m {\ell}$ of meneral sals medium supplemented with $10 \mu\textrm{M}$ TCE degradation was inhibited in the initial period of 1 mM phenol addition, but after that time Pseudomonas sp. EL-04J cells degraded TCE and showed cell growth.

• Asian-Australasian Journal of Animal Sciences
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• v.1 no.1
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• pp.21-25
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• 1988

The rumen degradability of rice straw (untreated, urea-sprayed, urea-treated), grasses (Panicum maximum, Pennisetum clandestinum) and rice bran was compared. The mean in vivo organic matter digestibility of the untreated (US), urea-supplemented (SS) and urea-ammonia treated (TS) rice straw were 50.9, 53.9 and 57.4%, respectively. Rice bran contained extremely high levels of acid-insoluble ash (25.2% DM), and its OMD was 36.1%. Grasses had OMD values around 66%. Degradability measurements were performed with buffaloes using the nylon bag technique. The organic matter (OM) disappearance data were fitted to an model which was used to describe degradation pattern. The mean potentially degradable fraction for US, SS and TS was 61.5, 61.9 and 69.4%, respectively. Urea-ammonia treatment increased both the amount of OM degraded and the rate at which it was degraded in the rumen. Both grasses had similar values for degradable fraction (around 65%) and for rate constant for degradation (0.04). Rice bran contained high proportions of readily soluble material (23.9%), but the degradable OM fraction was only 13.2%. The low quality of rice bran is attributed to the contamination of rice hulls during processing.

• Fisheries and Aquatic Sciences
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• v.15 no.2
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• pp.91-97
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• 2012

To isolate a nonylphenol (NP)-degrading bacterium, we isolated a single colony from the NP-degrading microbial consortium SW-3, which was previously isolated from an aqueous environment. Ten colonies that exhibited different cell morphologies were isolated and the strains were named SW-3-A, -B, -C, -D, -E, -F1, -F2, -G, -H, and -I. The ability of isolates to degrade NP was evaluated by kinetic analysis by the constant of NP degradation rate ($k_1$) and the half-life time of NP degradation ($t_{1/2}$). SW-3-F1, -F2, -G, and -I strains were superior at degrading NP. The $k_1$ and $t_{1/2}$ values of the four strains were sixfold higher and one-sixth lower, respectively, than those of the consortium strain. Additionally, SW-3-F1, -G, and -I strains were tested for their ability to degrade NP during coculture. NP degradation by coculture with a combination of all three strains was inferior to that of culture conducted with single isolates, suggesting that the three strains are antagonistic toward each other during NP degradation.

• Microbiology and Biotechnology Letters
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• v.30 no.4
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• pp.395-401
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• 2002

Methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK) have been widely used as solvents in various industries. Biodegradation of MEK and MIBK by Pseudomonas putida KT-3, which could utilize MEK or MIBK as a sole carbon source, was characterized, and the cosubstrate interaction in MEK/MIBK mixture was also studied. Within the range of initial MEK concentration (from 0.5 to 5.5 mM), an increased substrate concentration increased the specific degradation rate of MEK by P putida KT-3 (from 3.15 to 10.58 mmol/g DCW$\cdot$h), but the rate sightly increased at 11.0 mM of initial MEK concentation (11.28 mmol/g DCW$\cdot$h). The similar degradation rates of MIBK (4.69-4.92 mmol/g DCW$\cdot$h) were obtained at more than 3.0 mM of initial MIBK concentation. Kinetic analysis on the degradation of MEK/MIBK mixture by P. putida KT-3 showed that MEK or MIBK acted as a competitive inhibitor. Maximum degradation rate ($V_{max}$), saturation constant ($K_{m}$) and inhibition constant ($K_{1}$) were as follows: $V_{max,MEK}$=12.94 mmol/g DCW$\cdot$h; $K_{m,MEK}$=1.72 mmol/L; $K_{l,MEK}$=1.30 mmol/L; $V_{max,MIBK}$=5.00 mmol/g-DCW$\cdot$h; $K_{m,MIBK}$=0.42 mmol/L; $K_{l,MEK}$=0.77 mmol/L.

• Korean Chemical Engineering Research
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• v.45 no.5
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• pp.460-465
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• 2007

Endosulfan-${\alpha}$ endosulfan-${\beta}$ and endosulfan-sulfate, which are classified as pesticides, were degraded by use of UV energy and ultrasonic irradiation. The degradation residuals were analysed by gas chromatography with an electron capture detector and TOC (total oragnic carbon) analysis. The reactions were conducted in a quartz annular reactor equipped with a low pressure mercury multilamp (8Wx2) and a sonic generator. All the aqueous solutions were concentrated as 10 mg/L initially. Endosulfans were degraded each to result in 48.2% (${\alpha}$), 50.0% (${\beta}$) and 76.5% (sulfate) of removal efficiency by UV energy, and 66.9% (${\alpha}$), 55.8% (${\beta}$) and 72.7% (sulfate) by ultrasonic irradiation, respectively. In contrast to the results of the single-component solutions, degradation of the endosulfan-sulfate was greatly suppressed to result in the lowest degradation rate and removal efficiency in the three-component solutions. This finding suggests that there should be a reversible reaction with a substantially low equilibrium constant between endosulfan-${\alpha}$ or -${\beta}$ and -sulfate in the coexistence of the three endosulfans. TOC data showed the endosulfans were decomposed by 20%~40% toward complete mineralization, producing a quantity of intermediates induced by the radical reactions. We found that all the decay reactions considered in this study nicely fell into pseudo first-order rate.

• Journal of Food Hygiene and Safety
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• v.14 no.4
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• pp.339-345
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• 1999

The present study was performed to investigate photodegradation rate constants and degradation products of dichlorvos and methidathion by the USEPA method. The two pesticides were very stable in sunlight for 16 days from September 2 to 18, 1998 and humic acid had no sensitizing effect on the photolysis of each pesticide in sunlight. The photolysis rate was fast-est for methidathion, followed by dichlorvos in the presence of UV irradiation. Photodegradation rate constant and half-life of dichlorvos were 0.0208 and 33.3 min, respectively. Photodegradation rate constant and half-life of methidathion were 0.6789 and 1.0min, respectively. The two pesticides were degraded completely in the presence of UV irradiation and UV irradiation with TiO$_2$in about 3 hours. Therefore, it is suggested that UV treatment will be effective for the degradation of pesticides in the process of drinking water purification. In case of dichlorvos and methidathion, UV irradiation with TiO$_2$was more effective for degradation than W irradiation. In order to identify photolysis products, the extracts of degradation products were analyzed by GC/ MS. The mass spectrum of photolysis products of dichlorvos was at m/z 153, those of the photolysis of methidathion were at m/z 198 and 214, respectively. Photolysis products of dichlorvos was Ο, Ο-dimethyl phosphate(DMP), those of methidathion were Ο, Ο-dimethyl phosphorothioate(DMTP) and Ο, Ο-dimethyl phosphorodithioate (DMDTP).

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.19-25
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• 2023

Although a lot of research and development has been conducted on the performance improvement of PEM (Proton Exchange Membrane) water electrolysis, the research on durability is still in early stage. This study investigated effect of temperature on the water electrolysis durability when driving temperature of the PEM water electrolysis was increased to improve performance. Voltage change, I-V, CV (Cyclic Voltammetry), LSV (Linear Sweep Voltammetry), Impedance, and FER (Fluoride Emission Rate) were measured while driving under a constant current condition in a temperature range of 50~80 ℃. As the operating temperature increased, the degradation rate increased. At 50~65 ℃, the degradation of the IrO₂ electrocatalyst mainly affected the durability of the PEM water electrolysis cell. At 80 ℃, the polymer membrane and electrode degradation proceeded similarly, and the short resistance decreased to 1.0 kΩ·cm² or less, and the performance decreased to about 1/3 of the initial stage after 144 hours of operation due to the shorting phenomenon.