• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.159-159
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• 2016

Vertically-aligned carbon nanotubes (VCNT) have attracted much attention due to their unique structural, mechanical and electronic properties, and possess many advantages for a wide range of multifunctional applications such as field emission displays, heat dissipation and potential energy conversion devices. Surface modification of the VCNT plays a fundamental role to meet specific demands for the applications and control their surface property. Recent studies have been focused on the improvement of the electron emission property and the structural modification of CNTs to enable the mass fabrication, since the VCNT considered as an ideal candidate for various field emission applications such as lamps and flat panel display devices, X-ray tubes, vacuum gauges, and microwave amplifiers. Here, we investigate the effect of surface morphology of the VCNT by water vapor exposure and coating materials on field emission property. VCNT with various height were prepared by thermal chemical vapor deposition: short-length around $200{\mu}m$, medium-length around $500{\mu}m$, and long-length around 1 mm. The surface morphology is modified by water vapor exposure by adjusting exposure time and temperature with ranges from 2 to 10 min and from 60 to 120oC, respectively. Thin films of SiO2 and W are coated on the structure-modified VCNT to confirm the effect of coated materials on field emission properties. As a result, the surface morphology of VCNT dramatically changes with increasing temperature and exposure time. Especially, the shorter VCNT change their surface morphology most rapidly. The difference of field emission property depending on the coating materials is discussed from the point of work function and field concentration factor based on Fowler-Nordheim tunneling.

• Safety and Health at Work
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• 제13권2호
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• pp.227-234
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• 2022

Background and Purpose: In 2021, lung cancer in school food workers was first recognized as an occupational cancer. The classification of the carcinogenicity of cooking fumes by International Agency for Research on Cancer (IARC) was based on Chinese epidemiological data. This study aimed to determine the hazard levels of school cooking fumes in Korea. Materials and Methods: Based on public school cafeterias in one area, 25 locations were selected for the survey according to the number per school type, ventilation states, and environmental pre-assessments of cafeterias. Two inside cooking areas using a heat source and one outside cooking area were selected as control measurement points. Measurements of CO, CO₂, polycyclic aromatic hydrocarbons (PAHs), and total volatile organic compounds (TVOCs), including benzene, formaldehyde, and particulate matter (PM10, PM2.5, PM1, respectively), were taken. The concentrations and patterns of each substance in the kitchens were compared with the outdoor air quality. Result: Known carcinogens, such as the concentrations of PAHs, formaldehyde, TVOC (benzene), and particulate matter in school cooking fumes, were all detected at similar or slightly higher levels than those found outside. Additionally, substances were detected at relatively low concentrations compared to the Chinese cooking fumes reported in the literature. However, the short-term exposure to high concentrations of CO (or composite exposure with CO₂) and PM2.5 in this study were shown. Conclusion: The school cooking fumes in South Korea was a relatively less harmful than Chinese cooking fumes, however short-term, high exposure of toxic substances can cause a critical health effect.

• 한국식품과학회지
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• 제40권6호
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• pp.712-716
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• 2008

Salmonella로부터 식품 안전성을 높이기 위한 보존법의 병용처리에 의한 효과를 평가하고자 S. Typhimurium을 열과 산, 산화제 등으로 연속 처리한 후 생균수를 측정하여 효과를 분석하였다. 그리고 열충격에 의하여 S. Typhimurium 내에 발현되거나 억제되는 단백질을 이차원 전기영동과 MALDI-TOF 질량분석기로 분석하였다. 열처리된 S. Typhimurium은 초산과 염산의 pH 4에서의 생균수가 1.3-1.8 log CFU/mL가 줄었고 비열처리 S. Typhimurium은 생균수가 약 5 log CFU/mL가 감소하였다. 열처리 S. Typhimurium은 butyl hydrogen peroxide와 과산화수소에서 생균수가 1.1-1.7 log CFU/mL가 줄었으나 비열처리 S. Typhimurium은 5.4-5.6 log CFU/mL 감소하였다. 충분하지 않은 사멸 열처리는 S. Typhimurium의 생존력을 증가시키고 산과 산화제 등의 보존제에서 저항성이 커지는 것을 알 수가 있었다. 이차원 전기영동과 MALDI-TOF 질량분석에 의한 발현 단백질 분석 결과 비열처리 S. Typhimurium은 17개의 단백질이 검출되었고 열처리 S. Typhimurium에는 13개의 단백질만 검출되었다. 이들 중에 열충격 단백질로 알려진 DnaK, small heat shock protein 등이 검출되었고 이들이 산과 산화제에서의 생존 저항성 증가와 관련이 있을 것으로 보인다. 그러므로 열처리를 포함하는 hurdle technology를 적용하여 식품을 보존처리할 때 다른 보존제에 대한 교차보호성이 증가되는 사실을 고려하여 적절한 열처리가 고려되어야 된다는 것을 알 수 있었다.

• 대한한방부인과학회지
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• 제27권3호
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• pp.1-11
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• 2014

Objectives: Hwangryunhaedok-tang (HH) is a representative heat clearing multiherb prescription. We evaluated the protective effect of HH against heat stress exposure in mice. Methods: Six weeks old ICR mice were used for this study. After $43^{\circ}C$ heat stress for 15 minutes, we evaluated the changes of motor activity and c-fos expression level to determine the proper heat stress and evaluation time. The subjects were divided into 4 groups (1. control group, 2. heat stress group with normal saline, 3. heat stress group with administration of 100 mg/kg, and 4. heat stress group with administration of 1000 mg/kg). After oral administration of HH once a day for 3 days, 2, 3, 4 groups were exposed to $43^{\circ}C$ heat stress for 15 minutes. Then, we evaluated the motor activity for 120 minutes and analyzed the c-fos expression using western blot. We investigated the effect of HH and its ingredients on c-fos expressions after heat stress. The mice were administrated HH, Scutellariae Radix, Coptidis Rhizoma, Phellodendri Cortex, and Gardeniae Fructus for 3 days. After one hour of last treatment, the mice were exposed to heat stress at $43^{\circ}C$ for 15 min. After two hours, the hypothalamus was dissociated and lysed to measure c-fos expression. Results: After oral administration of HH for 3 days, motor activity was recovered insignificantly. 100 mg/kg HH treatment reduced the c-fos expression after heat stress but insignificantly. Among the ingredients of HH, Coptidis Rhizoma and Scutellariae Radix treatment groups significantly reduced the c-fos after stress. Conclusions: These results show that Hwangryunhaedok-tang may be effective to reduce the heat stress response.

• Food Science and Biotechnology
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• 제16권5호
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• pp.828-831
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• 2007

We evaluated the effects of heat treatment on various properties of onion extracts (Allium cepa). Onion was heated at various temperatures ($110-150^{\circ}C$) for various times (1-5 hr), and the total polyphenol, flavonoid, and free sugar contents, and antioxidant activity were investigated. With increased heating temperatures and exposure times, the total contents of polyphenols and flavonoids, as well as antioxidant activity increased. The highest total polyphenol content (189.80 mg/100g) occurred after heating for 2 hr at $140^{\circ}C$. The highest total flavonoid content (252.51 mg/100g) occurred after heating for 3 hr at $150^{\circ}C$. The antioxidant activity assessed using the DPPH method was highest, at 2.1 mg/mL ($IC_{50}$ value), after heating for 2 hr at $150^{\circ}C$. Correlations between antioxidant activity and the total polyphenol, total flavonoid, and fructose contents were highly significant (all p<0.01). The optimal heating time and temperature were 2 hr and $130^{\circ}C$.

• 센서학회지
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• 제20권1호
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• pp.64-69
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• 2011

Porous manganese oxide porous nanostructures were prepared by amino-acid-mediated solvothermal self assembly reaction and subsequent heat treatment at $600^{\circ}C$. When Mn-precursors were heat-treated at $400-550^{\circ}C$, the sensors did not show significant gas responses. In contrast, the manganese oxide heat-treated at $600^{\circ}C$ showed the significant gas responses, that is, the resistance decrease to 100 ppm $C_3H_8$ ($R_a/R_g$ = 2.17, $R_a$ : resistance in air, $R_g$ : resistance in gas) and the resistance increase to 100 ppm $C_2H_5OH$ ($R_g/R_a$ = 1.92). The opposite change of resistance upon exposure to $C_3H_8$ and $C_2H_5OH$ was discussed in relation to the mixed phases of manganese oxides with different valences.

• Asian-Australasian Journal of Animal Sciences
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• 제31권8호
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• pp.1244-1251
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• 2018

Objective: The objective of the present study was to elucidate the mechanism underlying liver metabolic perturbations in dairy cows exposed to heat stress (HS). Methods: Liquid chromatography massabl spectrometry was used to analyze metabolic differences in livers of 20 dairy cows, with and without exposure to HS. Results: The results revealed 33 potential metabolite candidate biomarkers for the detection of HS in dairy cows. Fifteen of these metabolites (glucose, lactate, pyruvate, acetoacetate, ${\beta}$-hydroxybutyrate, fumaric acid, citric acid, choline, glycine, proline, isoleucine, leucine, urea, creatinine, and orotic acid) were previously found to be potential biomarkers of HS in plasma or milk, discriminating dairy cows with and without HS. Conclusion: All the potential diagnostic biomarkers were involved in glycolysis, amino acid, ketone, tricarboxylic acid, or nucleotide metabolism, indicating that HS mainly affected energy and nucleotide metabolism in lactating dairy cows.

• Elastomers and Composites
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• 제55권3호
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• pp.222-228
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• 2020

Rubber materials, used in nuclear power plants, need high heat-oxidation resistance to curing or cracking under a heat aging environment. This is because they are applied to environments with high temperature, high humidity, and radiation exposure. Nuclear radiation causes additional hardening or degradation, therefore, rubber materials need radiation resistance that satisfies the general and any accidental conditions produced in the power plant. Therefore, in this study, we developed a rubber material with excellent heat and radiation resistance for the diaphragm seal of a nuclear steam generator nozzle dam. The rubber material greatly improved the reliability of the steam generator nozzle dam. In addition, 30 inch and 42 inch diaphragm seals were manufactured using the developed rubber material. A nozzle dam was installed in a nuclear power plant and tested under the same conditions as a steam generator to evaluate safety and reliability. In the future, the performance and safety of diaphragm seals developed through field tests of nuclear power plants will be evaluated and applied to currently operating and new nuclear power plants.

• 한국전기전자재료학회논문지
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• 제33권4호
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• pp.249-254
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• 2020

An 80 nm thick zinc aluminate thin film was deposited on a glass substrate via radio-frequency (rf) magnetron sputtering and heat treated to analyze changes in the wetting angles due to a surface modification. The thin films were modified from hydrophilic to hydrophobic by a simple thermal treatment. The surface modification from a heat treatment increased the wetting angles up to 111°, which was explained by the relationship with the excess surface area. The wetting angles of the annealed thin films decreased with increasing exposure time under ambient conditions, which was attributed to the oxygen vacancies in the films that were introduced during deposition. The annealed thin films were treated by ionized oxygen via oxygen plasma. After the oxygen plasma treatment, the decreased wetting angles were maintained at ~95° for 11 days.

• Food Science and Biotechnology
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• 제17권6호
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• pp.1387-1390
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• 2008

This study evaluated the effects of heat treatment on antioxidant activity of Rehmannia radix Libosch (RRL). RRL was heated at various temperatures ($110-150^{\circ}C$) for various times (1-5 hr), and the total polyphenol, flavonoid content, and antioxidant activity were investigated. With increased heating temperature and exposure time, total content of polyphenol, flavonoid, as well as antioxidant activity increased. The highest total polyphenol and flavonoid contents were 21.65 and 3.56 mg/g, respectively, these values were occurred after heating for 3 hr at $150^{\circ}C$ (RRL was 5.09 and 0.83 mg/g, respectively). The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was highest value of 83.46% after heating for 3hr at $150^{\circ}C$. The 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) cation radical scavenging activity was highest value of 20.43mg ascorbic acid (AA) eq/g after heating for 2 hr at $150^{\circ}C$. There were highly significant differences in the total polyphenol, flavonoid content, and antioxidant activity among heating temperatures and times (p<0.001), with heating temperature having the greater effect.