• 제목/요약/키워드: Reaction stability

검색결과 1,618건 처리시간 0.026초

한국산 달맞이꽃 종자유의 산화안정성에 관한 연구 (Study on the Oxidative Stability of Korean Evening Primrose Oil)

  • 표영희;김인숙;안명수
    • 한국식품조리과학회지
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    • 제5권2호
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    • pp.27-34
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    • 1989
  • In the present study, the oxidative stability of Korean evening primrose oil (EPO) stored in various conditions, i.e., dark, cool, fluorescent light and daylight irradiation were investigated. Furthermore difference between the compositional content of gamma-linolenic acid (GLA) of EPO and that of alpha-linolenic acid of soybean oil (SOY) undergoing various modes of oxidation was observed. The results of the present study were as follows: More rapid autoxidative reations of EPO than that of SOY in vairous conditions increased in order of daylight, fluorescent light, cool and dark. Espectially, autoxidative rates of EPO increased rapidly on exposure to daylight and fluorescent light. This probably was due to chlorophyll functioned as a photosensitizer resulting in rapid oxidation of the EPO during irrdadiation of light. However, there was no difference between compositional content of GLA in EPO and alpha-linolenic acid in SOY undergoing various modes of oxidation. Therefore, theripid oxidative rate of EPO could be due to the catalytic effect of the chlorophyll on the photoxidation and the free radical reaction of PUFA.

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DYNAMICAL BEHAVIOR OF A HARVEST SINGLE SPECIES MODEL ON GROWING HABITAT

  • Ling, Zhi;Zhang, Lai
    • 대한수학회보
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    • 제51권5호
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    • pp.1357-1368
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    • 2014
  • This paper is concerned with a reaction-diffusion single species model with harvesting on n-dimensional isotropically growing domain. The model on growing domain is derived and the corresponding comparison principle is proved. The asymptotic behavior of the solution to the problem is obtained by using the method of upper and lower solutions. The results show that the growth of domain takes a positive effect on the asymptotic stability of positive steady state solution while it takes a negative effect on the asymptotic stability of the trivial solution, but the effect of the harvesting rate is opposite. The analytical findings are validated with the numerical simulations.

CrN 소결체의 고온 안정성 (High Temperature Stability of Sintered Bulk CrN)

  • 최정호;이동복
    • 한국표면공학회지
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    • 제40권1호
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    • pp.39-43
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    • 2007
  • The pure CrN powders oxidized to $Cr_2O_3$ noticeably above $850^{\circ}C$ in air. When these powders were sintered into bulk samples at $1500^{\circ}C$ under 40 atm of $N_2$ pressure, the CrN phase partly changed into the $Cr_2N$ phase, owing to the partial loss of nitrogen from CrN. When the bulk sample was heated at $1000-1200^{\circ}C$ for 100 hr under vacuum, the CrN phase also progressively changed into $Cr_2N$. At the same time, a relatively thin $Cr_2O_3$ layer formed on the bulk sample due to the reaction of chromium with residual oxygen in vacuum.

알루미나수화물(水和物)의 침전(沈澱)pH가 물성(物性)에 미치는 영향(影響) (Effect of pH of Precipitation on Physical and Chemical Properties of Hydrous Aluninum Oxide)

  • 이계주
    • Journal of Pharmaceutical Investigation
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    • 제6권2호
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    • pp.95-100
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    • 1976
  • A study on the effect of the pH of precipitation on the acid consuming capacity, aging stability, physical and chemical properties of hydrous aluminum oxide prepared by the reaction of aluminum chloride and ammonium hydroxide solution was carried out by means of X-ray diffraction, IR spectra and differential thermal analysis. The results from these experiments are as follows: 1. Hydrous aluminum oxide precipitated at lower pH showed better acid consuming capacity, higher stability and more anion contained in the structure than that prepared at higher pH. 2. The hydrous aluminum oxide prepared at lower pH is amorphous and that prepared at higher pH is crystalline hydrated hydrous aluminum oxide, i.e., Bayerite and these results are conformed to Rhee's hypothesis. 3. The rate of loss of reactivity and the end-point reactivity are related to the pH of precipitation.

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Cyclodextrin 수용액중(水溶液中)에서의 Aspirin의 분해(分解)에 관(關)한 연구(硏究) (Studies on the Decomposition of Aspirin in Aqueous Cyclodextrin Solution)

  • 박재영;박종훈;김신근;우종학;한세호
    • Journal of Pharmaceutical Investigation
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    • 제2권2호
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    • pp.5-17
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    • 1972
  • It was reported that cyclodextrin has a distinctive ability to form inclusion compound with a wide variety of compounds. The authors studied the stability of acetylsalicylic acid in cyclodextrin solution. From the results of this experiment, the decomposition of Aspirin in cyclodextrin solution was progressed according to the pseudofirt order reaction and its degradation rate constant was decreased and the thermodynamic activation energy of the degradation of aspirin was accetrated with the increase of cyclodextrin Conclusively, it was considered that cyclodextrin increased the stability of aspirin in aqueous solution by its inclusion compound formation.

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전통 대나무 악기재의 아세틸화 (Acetylation of Traditional Bamboo Flute)

  • 강호양;이종신;허종윤;이관영;심준오
    • Journal of the Korean Wood Science and Technology
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    • 제24권3호
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    • pp.5-11
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    • 1996
  • It has been reported that acetylation reduces the sorption of wood, thereby increasing the stability of the acoustic and dimensional properties of wood under conditions of changing humidity. Bamboos used for making a Korean traditional flute were acetylated and their dimensional properties were evaluated by measuring Weight Percent Gain and thickness swelling in water. Before acetylation bamboos were vacuum-dried to 3~6% at $50{\sim}80^{\circ}C$ without degradation. The optimum reaction temperature and time for bamboo acetylation were found to be $120^{\circ}C$ and 8 hours, respectively.

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$IO_4$-산화전분 변형에 의한 효소의 안정성 증가 (Stabilization of Aspergillus sp. $\alpha$-Amylase by Modification with $IO_4$-oxidized Starch)

  • 안용근
    • 한국식품영양학회지
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    • 제12권3호
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    • pp.265-270
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    • 1999
  • The stabilization of Aspergillus sp. $\alpha$-amylase was attained by modification with periodate-oxidized sol-uble starch. The pH stability of modified enzyme was increased at pH 3~4 and 9~11 in the presence of $\alpha$-cyclodextrin($\alpha$-CD) compared with that of native enzyme. Thermal stability of the modified enzyme was increased. After treatment at 6$0^{\circ}C$ for 30min the activity remained 20% for the enzyme modified at pH 9.7 in the presence of $\alpha$-CD and tested in the presence of $\alpha$-CD 10% for the enzyme modified at pH 9.7 in the presence of $\alpha$-CD 0% for the native enzyme. The native enzyme and modified enzyme showed one peak in HPLC. The substrate specificity of the modified enzyme was not changed in HPLC analysis of reaction product.

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부자재가 돼지 사체 퇴비화에 미치는 영향 (The Effects of Amendments on Composting of Swine Carcass)

  • 홍지형;최병민
    • 한국축산시설환경학회지
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    • 제5권1호
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    • pp.45-52
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    • 1999
  • The purpose of this study is to provide information for the livestock for the livestock carcass composting operation in agricultural waste management. Burial, landfilling and incineration of livestock carcass may have environmental regulatory and economic liabilities. Dead animals amended with agricultural residues can be composted and used to promote soil fertility and reduce environmental pollution. In this study we evaluated the effect of amendments on the primary and secondary composting reaction and stability of compost. The full-scale composting bin of swine carcass in roofed system with three amendments was adequate in reaching sufficient temperature above 55$^{\circ}C$ long enough to kill the pathogen. The average temperature of the compost material in dead swine amended with corn stover increased rapidly to 64$^{\circ}C$ on the 2nd day after primary composting and dropped to near ambient temperature on the 140th day of composting. The composting with of corn stover and wheat straw are more efficient for swine carcass composting than that of sawdust. Therefore, the amendment property is an important factor in the design of composting facility.

Study of the Photo-alignment Technique through the Surface Modification

  • Song, Dong-Mee;Shin, Dong-Myung
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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    • pp.197-198
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    • 2000
  • A surface-assisted photo-control of the liquid crystal (LC) alignment has been achieved by modifying the topmost surface of the polyimide film with photo-reactive molecules. Recently, photo-alignment technique using a thin film of poly(vinyl cinnamates) have been reported. However their commercial potentiality is limited by their low thermal stability. To enhance thermal stability, we synthesized the chalcone derivatives as the photo-reactive molecules and introduced the materials on the surface-modified polyimide film.. We identified that the photo-chemical reaction of the chalcone derivatives occur in few minutes with irradiation of UV light. The photo-alignment characteristics of the modified polyimide films treated by polarized UV light and their LC cells are investigated as a function of exposure dose.

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Thermally Stable and Processible Norbornene Copolymers

  • Yoo Dong-Woo;Yang Seung-Jae;Lee Jin-Kyu;Park Joohyeon;Char Kookheon
    • Macromolecular Research
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    • 제14권1호
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    • pp.107-113
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    • 2006
  • Processible norbornene copolymers were realized by judiciously designing norbomene comonomers, which were themselves prepared by the Diels-Alder reaction of cyclopentadiene and benzoquinone followed by the isomerization and alkylation of alcohols. The norbornene copolymers containing these derivatized comonomers, prepared by [Pd($x_{2}CH-{3} $)$_{4}$][$SbF_{6}$]$_{2}$ catalyst, exhibited excellent solubility in many organic solvents as well as good thermal stability, as evidenced by their high glass transition ($T_{g}$) and decomposition ($\∼$350$^{circ}C$) temperatures. In addition, fairly strong adhesion to substrates such as glasses and silicon wafers was also achieved with these copolymers to overcome the limitations experienced by polynorbornene homopolymers and to make them attractive for many important industrial applications.