• Title/Summary/Keyword: Thermal stability

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Antimicrobial Activity of Ethanol Extract from Sargassum thunbergii (지충이(Sargassum thunbergii) 에탄올 추출물의 항균활성)

  • Lee, So-Young;Song, Eu-Jin;Kim, Koth-Bong-Woo-Ri;Yoon, So-Young;Kim, Seo-Jin;Lee, So-Jeong;Hong, Yong-Ki;Lim, Sung-Mee;Ahn, Dong-Hyun
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.38 no.4
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    • pp.502-508
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    • 2009
  • Antimicrobial activity of Sargassum thunbergii was determined by paper disc assay and minimum concentration inhibitor (MIC) test. A water extract of S. thunbergii did not show the antimicrobial activity, but an ethanol extract of S. thunbergii (SHE) inhibited Serratia liquefaciens, Salmonella Typhimurium, Pseudomonas aerogenosa and all of the tested gram-positive bacteria at 4 mg/mL. Especially, Bacillus subtilis, Clostridium perfringens and Listeria monocytogenes were susceptible to SHE. As the results of MIC test, SHE inhibited the growth of B. subtilis, Staphylococcus aureus and Listeria monocytogenes at concentration of $0.1{\sim}0.3%$, and inhibited C. perfringens at 0.01%. In the thermal and pH stability test for SHE, antibacterial activities of SHE were maintained when the SHE was treated at $121^{\circ}C$ for 15 minutes or under pH $2{\sim}8$. SHE was partitioned in the order of n-hexane, chloroform, ethyl acetate and butanol. As the results of the MIC test for each obtained fraction, no fraction exhibited higher antibacterial activity than that of the crude SHE. However, a mixture of chloroform, ethylacetate and ethanol fractions showed higher antibacterial activity than SHE.

Research Trend of Biomass-Derived Engineering Plastics (바이오매스 기반 엔지니어링 플라스틱 연구 동향)

  • Jeon, Hyeonyeol;Koo, Jun Mo;Park, Seul-A;Kim, Seon-Mi;Jegal, Jonggeon;Cha, Hyun Gil;Oh, Dongyeop X.;Hwang, Sung Yeon;Park, Jeyoung
    • Applied Chemistry for Engineering
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    • v.31 no.2
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    • pp.115-124
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    • 2020
  • Sustainable plastics can be mainly categorized into (1) biodegradable plastics decomposed into water and carbon dioxide after use, and (2) biomass-derived plastics possessing the carbon neutrality by utilizing raw materials converted from atmospheric carbon dioxide to biomass. Recently, biomass-derived engineering plastics (EP) and natural nanofiber-reinforced nanocomposites are emerging as a new direction of the industry. In addition to the eco-friendliness of natural resources, these materials are competitive over petroleum-based plastics in the high value-added plastics market. Polyesters and polycarbonates synthesized from isosorbide and 2,5-furandicarboxylic acid, which are representative biomass-derived monomers, are at the forefront of industrialization due to their higher transparency, mechanical properties, thermal stability, and gas barrier properties. Moreover, isosorbide has potential to be applied to super EP material with continuous service temperature over 150 ℃. In situ polymerization utilizing surface hydrophilicity and multi-functionality of natural nanofibers such as nanocellulose and nanochitin achieves remarkable improvements of mechanical properties with the minimal dose of nanofillers. Biomass-derived tough-plastics covered in this review are expected to replace petroleum-based plastics by satisfying the carbon neutrality required by the environment, the high functionality by the consumer, and the accessibility by the industry.

Study on Ventilation Efficiency of A Naturally Ventilated Broiler House-( I ) Summer Season (자연환기식 육계사내의 환기효율성 조사연구-( I )하절기)

  • 이인복;유병기;정문성;윤진하;전종길;김경원;성시흥
    • Journal of Animal Environmental Science
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    • v.9 no.1
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    • pp.9-18
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    • 2003
  • Most of broiler houses in Korea have the trouble of environmental control such as suitability, stability, and uniformity of internal climate, resulting in serious stress on chickens. Accordingly, it is very urgent to develop optimum designs of naturally and mechanically ventilated broiler houses for Korean climate. In this study, the internal climates such as air temperature, humidity, dust, ammonia gas, and air velocity were measured at a naturally ventilated broiler house. The data were collected during summer season including local weather data. It was found that the difference between measured and optimum air temperatures was $14.0^{\circ}C$ in maximum during the summer time. The daily maximum range of internal averaged air temperature was found $10.5^{\circ}C$ while the uniformity was $5.2^{\circ}C$ in maximum. The maximum, average, and minimum internal averaged relative humidity were 89.3%, 73.7%, and 49.2%, respectively while locally measured were 95.1% and 47.2%, respectively in maximum and minimum. Considering Temperature-humidity index, during summer season, over 97% of totally rearing period was shown that counter plan is needed for thermal stress while it was very dangerous situation for 22% of the rearing period. The ammonia gas and dust concentrations were seriously affected by the broilers activity, growth level, and relative humidity.

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Interpretation of the Manufacturing Characteristics and the Mineral and Chemical Composition of Neolithic Pottery Excavated from the Jungsandong Site, Yeongjong Island, South Korea (영종도 중산동 신석기시대 토기의 광물 및 화학조성과 제작특성 해석)

  • Lee, Chan Hee;Kim, Ran Hee;Shin, Sook Chung
    • Korean Journal of Heritage: History & Science
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    • v.51 no.1
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    • pp.4-31
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    • 2018
  • The Neolithic pottery excavated from the Jungsandong site has been classified into four types of pottery (I: feldspar type, II: mica type, III: talc type and IV: asbestos type) according to their mineral composition. These four types of potteries generally appear to have undergone incomplete firing, while the level of oxidation in the type I pottery objects, which have a relatively higher clay content, was found to be particularly low. The type III objects, which have a high talc content, are judged to have been somewhat slow in removing carbon because they contain saponite belonging to the smectite group. Of the four types of pottery, type IV showed the highest redness and the most uniform characteristics, thus indicating a good level of oxidation. In particular, fixed carbide (C; 33.7 wt.%) with a thickness of about 1mm, and originating from organic substances, was detected inside the walls of the type I pottery, while the deep radial cracks in the outer surfaces of the pottery are thought to have been caused by repeated thermal shocks. Given that all of the pottery except for the type I artifacts are considered to be have been made for storage purposes, those containing talc and tremolite are easy to done liquid storing vessels based on an analysis of their material characteristics. As for the type II relics, which are composed of various minerals and exhibit poor physical properties, they seem to have been used for simple storage purposes. As domestic talc and asbestos mines were concentrated in the areas of Gyeonggi, Gangwon, Chungbuk, and Chungnam, it seems likely that talc and tremolite were produced as contiguous minerals. Considering the distance between the remains in Jungsandong and these mines and their geographical distribution, there is a possibility - albeit somewhat slight - that these mines were developed for the mining of various minerals. Although ultramafic rock masses - such as serpentine capable of generating talc and tremolite - have not been found in the Jungsandong area, limestone and biotite granite containing mica schist have been identified in the northwestern part of Yeongjong Island, indicating that small rock masses might have formed there in the past. Therefore, it is judged necessary to accumulate data on pottery containing talc and tremolite, other than the remains in Jungsandong, and to investigate the rocks and soils in the surrounding area with greater precision. The firing temperatures of the pottery found at the Jungsandong site were interpreted by analyzing the stability ranges of the mineral composition of each type. As a result, they have been estimated to range from 550 to $800^{\circ}C$ for the type I artifacts, and from 550 to $700^{\circ}C$ for the type I, II and IV artifacts. However, these temperatures are not the only factors to have affected their physical properties and firing temperature, and the types, particle sizes, and firing time of the clay should all be taken into consideration.

Production of Poly (3-Hydroxybutyrate-co-3-Hydroxyvalerate) by Bacillus sp. EMK-5020 Using Makgeolli Lees Enzymatic Hydrolysate and Propionic Acid as Carbon Sources (막걸리 주박 가수분해 산물과 propionic acid를 탄소원으로 이용한 Bacillus sp. EML-5020 균주로부터 poly (3-hydroxybutyrate-co-3-hydroxyvalerate) 생합성)

  • Kwon, Kyungjin;Kim, Jong-Sik;Chung, Chung-Wook
    • Journal of Life Science
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    • v.32 no.7
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    • pp.510-522
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    • 2022
  • In this study, to biosynthesize PHA with properties more similar to polypropylene, a Bacillus sp. EMK-5020 strain that biosynthesized poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was isolated from soil. Bacillus sp. EMK-5020 strain biosynthesized PHBV containing 1.3% 3-hydroxyvalerate (3HV) using reducing sugar contained in Makgeolli lees enzymatic hydrolysate (MLEH) as a single carbon source. As the amount of propionic acid, which was added as a second carbon source, increased, the content of 3HV also increased. PHBV containing up to 48.6% of 3HV was synthesized when 1.0 g/l of propionic acid was added. Based on these results, the strain was cultured for 72 hr in a 3 l fermenter using reducing sugar in MLEH (20 g/l) and propionic acid (1 g/l) as the main and secondary carbon sources, respectively. As a result, 6.4 g/l DCW and 50 wt% of PHBV (MLEH-PHBV) containing 8.9% 3HV were biosynthesized. Through gel permeation chromatography and thermogravimetric analysis, it was confirmed that the average molecular weight and the decomposition temperature of MLEH-PHBV were 152 kDa and 273℃, respectively. In conclusion, the Bacillus sp. EMK-5020 strain could biosynthesize PHBV containing various 3HV fractions when MLEH and propionic acid were used as carbon sources, and PHBV-MLEH containing 8.9% 3HV was confirmed to have higher thermal stability than standard PHBV (8% 3HV).

Investigation on Diesel Injection Characteristics of Natural Gas-Diesel Dual Fuel Engine for Stable Combustion and Efficiency Improvement Under 50% Load Condition (천연가스-디젤 혼소 엔진의 50% 부하 조건에서 제동효율 및 연소안정성 개선을 위한 디젤 분무 특성 평가)

  • Oh, Sechul;Oh, Junho;Jang, Hyungjun;Lee, Jeongwoo;Lee, Seokhwan;Lee, Sunyoup;Kim, Changgi
    • Journal of the Korean Institute of Gas
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    • v.26 no.3
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    • pp.45-53
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    • 2022
  • In order to improve the emission of diesel engines, natural gas-diesel dual fuel combustion compression ignition engines are in the spotlight. In particular, a reactivity controlled compression ignition (RCCI) combustion strategy is investigated comprehensively due to its possibility to improve both efficiency and emissions. With advanced diesel direct injection timing earlier than TDC, it achieves spontaneous reaction with overall lean mixture from a homogeneous mixture in the entire cylinder area, reducing nitrogen oxides (NOx) and particulate matter (PM) and improving braking heat efficiency at the same time. However, there is a disadvantage in that the amount of incomplete combustion increases in a low load region with a relatively small amount of fuel-air. To solve this, sensitive control according to the diesel injection timing and fuel ratio is required. In this study, experiments were conducted to improve efficiency and exhaust emissions of the natural gas-diesel dual fuel engine at low load, and evaluate combustion stability according to the diesel injection timing at the operation point for power generation. A 6 L-class commercial diesel engine was used for the experiment which was conducted under a 50% load range (~50 kW) at 1,800 rpm. Two injectors with different spray patterns were applied to the experiment, and the fraction of natural gas and diesel injection timing were selected as main parameters. Based on the experimental results, it was confirmed that the brake thermal efficiency increased by up to 1.3%p in the modified injector with the narrow-angle injection added. In addition, the spray pattern of the modified injector was suitable for premixed combustion, increasing operable range in consideration of combustion instability, torque reduction, and emissions level under Tier-V level (0.4 g/kWh for NOx).