• 전기화학회지
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• 제11권1호
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• pp.42-46
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• 2008

연료전지는 수소를 직접 사용하는 것이 가장 효율이 높지만 가정이나 사무실에서는 수소 저장탱크를 사용하기보다는 도시가스(메탄가스)를 연료 source로 하여 수소를 생산하는 것이 유리하다. 연료전지에 사용하는 수소는 천연가스나 바이오가스, 탄화수소계열의 연료를 개질하여 생산하며 개질반응과정에서 필연적으로 여러 성분의 불순물이 포함되어 있다. CO, $CO_2$, $H_2S$, $NH_3$, $CH_4$등의 불순물이 포함된 수소연료가 PEM fuel cell에 공급되면 연료전지 성능에 영향을 준다고 보고되어 있다. 이러한 영향에는 전극 촉매의 피독에 의한 kinetic losses, 전해질막과 촉매이온층의 양이온 전도성 감소에 의한 ohmic losses 그리고 촉매층의 구조나 소수성 감소에 의한 mass transport losses가 있다. 개질기에서 생산된 수소연료는 약 73%의 $H_2$와 20% 이하의 $CO_2$, 5.8% 이하의 $N_2$, 2% 이하의 $CH_4$, 10ppm 이하의 CO로 최종 공급된다. 본 연구에서는 연료 중에 $CO_2$가 고분자전해질 연료전지 anode측 성능에 미치는 영향을 조사하였다. 실험은 연료전지에 공급되는 연료중에 $CO_2$농도를 10%, 20%, 30%로 전류와 전압의 성능곡선과 장시간(10시간)실험 그리고 임피던스를 측정하였다. 또한 가스크로마토그래피를 이용하여 순수한 수소와 $CO_2$가 함유된 수소의 혼합을 통해 나온 연료전지 inlet에서의 불순물의 농도를 검증하였다.

• Journal of Radiation Protection and Research
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• 제42권2호
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• pp.83-90
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• 2017

Background: Different cases exist in the measurement of thyroid radiobioassays owing to the individual characteristics of the subjects, especially the potential variation in the counting efficiency. An In situ Object Counting System (ISOCS) was developed to perform an efficiency calibration based on the Monte Carlo calculation, as an alternative to conventional calibration methods. The purpose of this study is to evaluate the applicability of ISOCS to thyroid radiobioassays by comparison with a conventional thyroid monitoring system. Materials and Methods: The efficiency calibration of a portable high-purity germanium (HPGe) detector was performed using ISOCS software. In contrast, the conventional efficiency calibration, which needed a radioactive material, was applied to a scintillator-based thyroid monitor. Four radioiodine samples that contained $^{125}I$ and $^{131}I$ in both aqueous solution and gel forms were measured to evaluate radioactivity in the thyroid. ANSI/HPS N13.30 performance criteria, which included the relative bias, relative precision, and root-mean-squared error, were applied to evaluate the performance of the measurement system. Results and Discussion: The portable HPGe detector could measure both radioiodines with ISOCS but the thyroid monitor could not measure $^{125}I$ because of the limited energy resolution of the NaI(Tl) scintillator. The $^{131}I$ results from both detectors agreed to within 5% with the certified results. Moreover, the $^{125}I$ results from the portable HPGe detector agreed to within 10% with the certified results. All measurement results complied with the ANSI/HPS N13.30 performance criteria. Conclusion: The results of the intercomparison program indicated the feasibility of applying ISOCS software to direct thyroid radiobioassays. The portable HPGe detector with ISOCS software can provide the convenience of efficiency calibration and higher energy resolution for identifying photopeaks, compared with a conventional thyroid monitor with a NaI(Tl) scintillator. The application of ISOCS software in a radiation emergency can improve the response in terms of internal contamination monitoring.

• Asian-Australasian Journal of Animal Sciences
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• 제19권1호
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• pp.72-79
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• 2006

1,225 healthy day-old avian broiler chicks were used to investigate the effects of activated charcoal (AC, made from willow tree), hydrated sodium calcium aluminosilicates (HSCAS) and esterified glucomannan (EGM) supplementation on broiler performance, blood profiles and meat characteristics when less moldy or moldy corn was included to formulate seven isocaloric and isonitrogenous diets: Positive Control (less moldy corn diet, PC), PC+2% AC, Negative Control (moldy corn, NC), NC+0.05% EGM, NC+0.1% EGM, NC+0.5% HSCAS and NC+1% AC. PC+2% AC resulted in lower growth rate, poorer feed conversion ratio (FCR), more leg problems and higher mortality of birds than those fed PC diet (p<0.05). Inclusion of 0.05% EGM, 0.1% EGM, 0.5% HSCAS and 1% AC in NC diet did not improve average daily weight gain (ADG) or affect feed intake of birds during the first or the second three-week periods. However, 0.05% EGM tended to (p>0.05) and 0.1% EGM significantly (p<0.05) improved FCR during the first three-week period. Breast meat of NC birds had higher Minolta $L^*$ values (white) but lower $a^*$ (reddish) and $b^*$ (yellowish) values (p<0.01) than the PC birds. Addition of 0.05% EGM and 0.1% EGM in NC diet reduced the $L^*$ values (p<0.05), improved $a^*$ and $b^*$ values (p<0.05) of breast meat of birds fed NC diet, but had no effect on meat color when 0.5% HSCAS or 1% AC was included (p>0.05). Relative weight of liver to body was reduced by feeding NC diet (p<0.05) and could not be normalized by different mycotoxin adsorbents (p>0.05) to the ratio of the PC birds. Relative weight of cholecyst of NC birds was increased compared with PC birds and could only be normalized by addition of 0.05% EGM and 1% AC (p<0.05) in NC diet. NC birds had lower serum albumin level than the PC birds (p<0.05) and addition of 0.05% EGM or 1% AC in NC diet did normalize serum albumin level. Addition of 0.5% HSCAS in NC diet further reduced serum albumin, globulin, total protein and uric acid levels (p<0.05). It was concluded that lower FCR during the first three-week period of growth and deterioration of meat quality observed in bird fed moldy corn with moderate T2 and fuminisin contamination and damaged nutrients and pigment availability, might be improved by dietary supplementation of 0.05% to 0.1% EGM, but not by 1% AC or 0.5% HSCAS supplementation.

• 한국항공우주학회지
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• 제47권9호
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• pp.649-657
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• 2019

대표적인 단일추진제로 사용되는 하이드라진은 극독성의 물질이므로 인체에 유해할 뿐만 아니라 취급이 매우 어렵다는 단점을 가지고 있다. 이를 대체하고자 최근에는 무독성의 친환경 추진제 개발 연구가 많은 관심을 받고 있다. 그중에서 스웨덴 우주공사(Swedish Space Corporation)에서 개발한 ammonium dinitramide(ADN) 계열 추진제는 하이드라진보다 우수한 성능을 가질 뿐만 아니라 우주환경에서의 성능검증을 통해 현재 상용화 단계에 이르렀다. 한편, 추력기 노즐에서 배출된 배기가스는 고진공의 우주 공간에서 확산하는 동안 위성체와 충돌할 경우 열 하중 및 표면 오염 등을 발생시켜 위성체의 성능과 수명을 감소시킬 수 있다. 하지만 친환경 추진제 추력기의 배기가스가 위성체에 미치는 영향에 대한 연구는 아직까지 본격적으로 수행되지는 않은 것으로 조사되었다. 따라서 본 연구에서는 Navier-Stokes 방정식과 직접모사법을 이용하여 ADN 계열 친환경 추진제에 대해 우주 공간에서의 배기가스 거동을 해석하고 하이드라진과 비교하였다. 이를 통해 향후 ADN 계열 친환경 추진제를 사용하는 위성체 개발 시 설계 검증자료로서 활용될 수 있을 것으로 기대된다.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.355-363
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• 2015

HVDC technology has become popular as an economic mode of bulk power transmission over very long distances. Polymeric insulators in HVDC power transmission lines are affected by surface tracking and erosion problems due to contamination deposit, which pose a greater challenge in maintaining the reliability of the HVDC system. In addition, polymeric insulators are also naturally affected by aging due to various environmental stresses, which in turn accelerates the surface tracking and erosion problems. Research works towards the improvement of tracking and erosion resistance of polymeric insulators by adding nano-sized fillers in the base material are being carried out worldwide. However, surface tracking and erosion performance of nano-filled aged polymeric insulators for HVDC applications are not well reported. Hence, in the present work, tracking and erosion resistance of the nano $Al(OH)_3$ filled silicone rubber insulation material has been evaluated under DC voltages at different filler concentrations and aged conditions, as per IEC 60587 test procedures. Leakage current and contact angle measurements were carried out to understand the surface hydrophobicity. Moving average technique was used to analyze the trend followed by leakage current. Water aged specimen shows less tracking resistance when compared with thermal aged specimen. It is observed that nano-filler concentration of 5% is even sufficient to get better tracking/erosion resistance under DC voltages.

• 대한영양사협회학술지
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• 제19권3호
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• pp.209-222
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• 2013

This study examined the hygiene practices of contract foodservice employees and investigated the influence of education and work environment on these hygienes practices. A questionnaire was distributed to 250 contract foodservice employees and a total of 232 responses were received and analyzed. The overall score for hygiene practices of contract foodservice employees was 3.89 based on a 5-point scale. Cross-contamination was prominent (highest score at 4.46) and the heating temperature was less prominent (lowest score at 3.49). The factors most affecting contract foodservice employees were their work period, the size of the contract foodservice management company, the number of meals served daily, the frequency of meal service per day and the frequency of hygiene education. Compared to small and medium-sized contract foodservice management companies, the major contract foodservice management companies showed higher scores for refrigerator/freezer control (P<0.001), vegetable/fruit disinfection (P<0.001), thawing (P<0.001), heating temperature (P<0.001), cleaning/disinfection (P<0.01), and personal hygiene (P<0.05). The frequency of hygiene education had a significant effect on the performance levels for refrigerator/freezer control (P<0.001), vegetable/fruit disinfection (P<0.001), thawing (P<0.001), heating temperature (P<0.001), cleaning/disinfection control (P<0.001), food supply control (P<0.05), and personal hygiene (P<0.05). From these results, to increase the sanitation quality of contract foodservice operations, hygiene practice levels need to increase and hygiene education systematically should be enforced for foodservice employees.

• 한국미생물·생명공학회지
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• 제39권1호
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• pp.86-92
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• 2011

3가지 종류의 생물정화법인 natural attenuation (NA), biostimulation (BS) 및 bioaugmentation (BA) 방법을 디젤로 오염된 토양을 정화하기 위해 적용하여, 각 방법에 의한 정화효율과 미생물 활성을 계면활성제 첨가 유무(Tween 80)에 따라 비교하였다. 토양 정화 초기 단계에서는 Rhodococcus sp. EH831을 접종원으로 이용하는 BA 방법에 의한 토양 정화효율이 가장 좋았다. 3가지 생물정화방법 모두에서 계면활성제 첨가는 토양 정화효율에 영향을 미치지 않았다. 토양의 탈수소활성(DHA)과 잔류 총석유계탄화수소(TPHs) 농도는 음의 상관관계를 보였다: DHA (${\mu}g-TPF{\cdot}g$-dry $soil^{-1}\;d^{-1}$) = -0.02 ${\times}$ TPHs concentration ($mg-TPHs{\cdot}kg$-dry $soil^{-1}$) + 425.76 (2500 ${\leq}$ TPHs concentration ${\leq}$ 20000, p < 0.01).

• 복식문화연구
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• 제28권2호
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• pp.265-284
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• 2020

This study aimed to analyze the performance of Disney-collaborated fashion lines based on online consumer reviews. To do so, the researchers employed text mining and network analysis to identify key words in the reviews of these products. Blogs, internet cafes, and web documents provided by Naver, Daum, and YoutTube were selected as subjects for the analysis. The analysis period was limited to one year after for the 2019. Data collection and analysis were conducted using Python 3.7, Textom, and NodeXL. The research terms in question were as follows: 'Disney fashion collaboration' and 'Frozen fashion collaboration'. Preliminary survey results indicated that 'Elsa's dress' was the most frequently mentioned term and that the domestic fashion brand Eland Retail was the most active in selling Disney branded clothing through its own brand. The writers of reviews for Disney-collaborated fashion products were primarily mothers with daughters. Their decision to purchase these products was based upon the following factors; price, size, stability of decoration, shipping, laundry, and retailer. The motives for purchasing the product were the positive response of the consumer's child and the satisfaction of the parents due to the child's response. The problems to be solved included insufficient quantity of supply, delay in delivery, expensive price considering the number of times children's clothes are worn, poor glitter decoration, faded color, contamination from laundry, and undesirable smells immediately after the purchase.

• Geomechanics and Engineering
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• 제12권5호
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• pp.753-770
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• 2017

The coagulation or flocculation of cohesive clay suspensions is one of the most widely used treatment technologies for contaminated water. Flocculated clay can transport pollutants and nutrients in ground water. Coagulants are used to accelerate these mechanisms. However, existing coagulants (e.g., polyacrylamide, polyaluminum chloride) are known to have harmful effects in the environment and on human health. As an alternative, eco-friendly coagulant, this study suggests ${\varepsilon}-polylysine$, a cationic biopolymer fermented by Streptomyces. A series of sedimentation experiments for various ${\varepsilon}-polylysine$ concentrations were performed, and the efficiency of sedimentation with ${\varepsilon}-polylysine$ was estimated by microscopic observation and light absorbance measurements. Two types of sedimentation were observed in the experiments: accumulation sedimentation (at 0.15%, 0.20%, 0.25% ${\varepsilon}-polylysine$) and flocculation sedimentation (at 0%, 0.1%, 0.5%, 1.0%, 2.0% ${\varepsilon}-polylysine$). These sedimentation types occur as a result of the concentration of counter ions. Additionally, the performance of ${\varepsilon}-polylysine$ was compared with that of a previously used environmentally friendly coagulant, chitosan. The obtained results indicate that flocculation sedimentation is appropriate for contamination removal and that ${\varepsilon}-polylysine$ functions more efficiently for clay removal than chitosan. From the experiments and analysis, this paper finds that polylysine is an alternative eco-friendly coagulant for removing chemical contaminants in groundwater.

• 한국미생물·생명공학회지
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• 제48권1호
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• pp.12-23
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• 2020

Edible films containing antimicrobial agents can be used as safe alternatives to preserve food products. Essential oils are well-recognized antimicrobials. However, their low water solubility, volatility and high sensitivity to oxygen and light limit their application in food preservation. These limitations could be overcome by embedding these essential oils in complexed product matrices exploiting the encapsulation efficiency of β-cyclodextrin. This study focused on the maximization of β-cyclodextrin production using cyclodextrin glucanotransferase (CGTase) and the evaluation of its encapsulation efficacy to fabricate edible antimicrobial films. Response surface methodology (RSM) was used to optimize CGTase production by Brevibacillus brevis AMI-2 isolated from mangrove sediments. This enzyme was partially purified using a starch adsorption method and entrapped in calcium alginate. Cyclodextrin produced by the immobilized enzyme was then confirmed using high performance thin layer chromatography, and its encapsulation efficiency was investigated. The clove oil/β-cyclodextrin inclusion complexes were prepared using the coprecipitation method, and incorporated into chitosan films, and subjected to antimicrobial testing. Results revealed that β-cyclodextrin was produced as a major product of the enzymatic reaction. In addition, the incorporation of clove oil/β-cyclodextrin inclusion complexes significantly increased the antimicrobial activity of chitosan films against Staphylococcus aureus, Staphylococcus epidermidis, Salmonella Typhimurium, Escherichia coli, and Candida albicans. In conclusion, B. brevis AMI-2 is a promising source for CGTase to synthesize β-cyclodextrin with considerable encapsulation efficiency. Further, the obtained results suggest that chitosan films containing clove oils encapsulated in β-cyclodextrin could serve as edible antimicrobial food-packaging materials to combat microbial contamination.