• 한국자기학회지
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• 제6권6호
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• pp.411-416
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• 1996

본 연구에서는 dc magnetron sputtering 방법으로 Corning glass 위에 자성층 Co와 비자성층 Cu의 계면에 얇은 Fe 자성층을 삽입하여 다층박막 $Fe(50\;{\AA})/[Co(17\;{\AA})/Fe(t\;{\AA})/Cu(24\;{\AA})]_{20}$을 제작하고 Fe 두께와 열처리 온도에 따른 자기저항 변화를 관찰하였다. 시료진동형자기계로 자기이력곡선을 측정하여 자기적 성질을 조사하였고 구조 및 표면 분석을 위해 각각 X-선 회절장치와 AFM(Atomic Force Microscope)을 이용하였다. 얇은 Fe 사이층을 삽입하지 않은 Co/Cu 다층박막에서 자기저항비가 22%인데 비해 얇은 Fe층을 삽입하였을때는 자기저항비가 26%까지 증가하였고 Fe 사이층의 두께가 점차 두꺼워짐에 따라 자기저항비는 다시 감소함을 나타냈다. $300^{\circ}C$ 까지 열처리한 결과 자기저항비는 증가하였으나 그 이상의 온도에서는 감소하였다.

• 한국재료학회지
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• 제21권12호
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• pp.655-659
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• 2011

An ultrafine grained complex aluminum alloy was fabricated by an accumulative roll-bonding (ARB) process using dissimilar aluminum alloys of AA1050 and AA5052 and subsequently annealed. A two-layer stack ARB process was performed up to six cycles without lubricant at an ambient temperature. In the ARB process, the dissimilar aluminum alloys, AA1050 and AA5052, with the same dimensions were stacked on each other after surface treatment, rolled to the thickness reduction of 50%, and then cut in half length by a shearing machine. The same procedure was repeated up to six cycles. A sound complex aluminum alloy sheet was fabricated by the ARB process, and then subsequently annealed for 0.5h at various temperatures ranging from 100 to $350^{\circ}C$. The tensile strength decreased largely with an increasing annealing temperature, especially at temperatures of 150 to $250^{\circ}C$. However, above $250^{\circ}C$ it hardly decreased even when the annealing temperature was increased. On the other hand, the total elongation increased greatly above $250^{\circ}C$. The hardness exhibited inhomogeneous distribution in the thickness direction of the specimens annealed at relatively low temperatures, however it had a homogeneous distribution in specimens annealed at high temperatures.

• Asian Journal of Atmospheric Environment
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• 제6권4호
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• pp.304-313
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• 2012

In this study, the ${\AA}$ngstrom exponent for polydispersed aerosol during dynamic processes was investigated. Log-normal aerosol size distribution was assumed, and a sensitivity analysis of the ${\AA}$ngstrom exponent with regards the coagulation and condensation process was performed. The ${\AA}$ngstrom exponent is expected to decrease because of the particle growth due to coagulation and condensation. However, it is difficult to quantify the degree of change. In order to understand quantitatively the change in the ${\AA}$ngstrom exponent during coagulation and condensation, different real and imaginary parts of the refractive index were considered. The results show that the ${\AA}$ngstrom exponent is sensitive to changes in size distribution and refractive index. The total number concentration decreases and the geometric mean diameter of aerosols increase during coagulation. On the while, the geometric standard deviation approaches monodispersed size distribution during the condensation process, and this change in size distribution affects the ${\AA}$ngstrom exponent. The degree of change in the ${\AA}$ngstrom exponent depends on the refractive index and initial size distribution, and the size parameter changes with the ${\AA}$ngstrom exponent for a given refractive index or chemical composition; this indicates that the size distribution plays an important role in determining the ${\AA}$ngstrom exponent as well as the chemical composition. Subsequently, this study shows how the ${\AA}$ngstrom exponent changes quantitatively during the aerosol dynamics processes for a log-normal aerosol size distribution for different refractive indices; the results showed good agreement with the results for simple analytic size distribution solutions.

• 대한화학회지
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• 제36권2호
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• pp.205-211
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• 1992

아세트아미드(AA)의 CO기와 희토류 금속이온(Ln(II))을 포함하는 몇 가지 lanthanide shift reagent(LSR) 사이의 상호작용을 이해하기 위하여 AA의 $2{\nu}_{C=0}$ + amide III 조합띠를 $15^{\circ}$ ${\sim} 45^{\circ}C$에서 조사하였다. 묽은 $CCl_4$ 용액속에서 하나의 AA가 사용된 LSR에 배위되어 1 : 1 AA-LSR 복합체를 이루며, Ln(Ⅲ)이온에 대한 AA의 배위 위치는 카르보닐의 산소임을 알았다. 온도 및 농도에 따른 이 조합띠의 변화로부터 Ln(III)${\cdot}$O=C 결합에 대한 여러가지 열역학적 함수들을 구했다. Eu$(dpm)_3$, Yb$(dpm)_3$ 및 Pr$(dpm)_3$에 대한 AA의 결합의 세기를 나타내는 ${\Delta}H^{\circ}$는 각각 -39.1, -28.4 및 -25.5kJ/mol이다. 이들 값을 비교해보면 AA 분자가 배위될 때 중심금속이온의 ionic potential 효과보다는 이미 배위되어 있는 커다란 dpm 분자에 의한 입체장애효과가 더 큼을 알 수 있다.

• 대한화장품학회지
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• 제47권1호
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• pp.23-30
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• 2021

본 연구는 개똥쑥(Artemisia annua L., AA), 유자(Citrus junos Sieb. ex TANAKA, CJ), 산국화(Chrysanthemum boreale Makino, CB), 잣나무(Pinus koraiensis, PK), 금강송(Pinus densiflora for. erecta, PD) 총 5 종의 자생식물 essential oil의 항 아토피 효능을 확인하기 위한 실험이다. 항균 효과를 확인하기 위해 자생식물 essential oil 5 종을 Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans 총 4 종류의 균에 처리했다. 항염증 효과를 확인하기 위해 TNF-α와 IFN-γ (TI)를 처리한 HaCaT 세포에 5 종의 자생식물 essential oil을 처리했다. AA, CJ, CB, PK, PD은 10 mg/mL 농도에서 Candida albicans에 대한 항균 효과를 나타냈다. AA (1 ㎍/mL), CB (1 ㎍/mL), PK (0.1, 1 ㎍/mL)에서 thymus and activation-regulated chemokine (TARC) 생성량이 억제되었고, AA 및 PK (1 ㎍/mL)에서 macrophage-derived chemokine (MDC) 생성량이 억제되었으며, AA (0.1, 1 ㎍/mL), PK (0.1, 1 ㎍/mL)에서 IL-6 생성량이 억제되었다. AA, CB, PK essential oil의 항균 및 항염증 효과가 확인되었으며, 이에 아토피 피부염 완화에 기여할 수 있음을 기대한다.

• Asian-Australasian Journal of Animal Sciences
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• 제7권1호
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• pp.137-145
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• 1994

Amino acid (AA) substituted diets had no influence on rumen levels of total volatile fatty acids (VFA), ammonia and ${\alpha}$-amino-N, but tended to increase molar proportions of isovalerate and counts of total viable AA utilizing and celluloytic bacteria in the rumen as compared with the control urea diet. The AA diets did not affect daily flow to the duodenum of dry matter (DM), organic mater (OM) and acid detergent fibre (ADF), and rumen digestibility of these nutrients. However, the AA diets, in particular the 10 essential AA (EAA) diet improved total digestibility of DM, OM and ADF by decreasing faecal output of these fractions. Although N flow to the duodenum and N retention were not affected with the dietary treatments, duodenal bacterial flow appeared to increase by the AA diets when it was estimated by means of 2,6-diaminopimelic acid (DAP) and nucleic acid-purine bases (PB) as markers. The results suggest that AA supplements to a urea diet could improve feed utilization by stimulating microbial activity and proliferation in the rumen but and increased microbial activity per se is not necessarily associated with improvement of feed conversion.

• Corrosion Science and Technology
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• 제22권5호
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• pp.322-329
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• 2023

There are a variety of heat exchangers used in automobiles, such as shell and tube heat exchangers, double tube heat exchangers, and plate heat exchangers. Most of them are water-cooled to prevent engine overheating. There have been reports of corrosion damage to these heat exchangers due to continuous wetting caused by external temperature differences, road pollutants, and snow removal. In addition, galvanic corrosion, which occurs when two dissimilar materials come into contact, has been identified as a major cause. In this study, corrosion characteristics and galvanic corrosion behavior of Al alloy (AA3003, AA4045 and AA7072) used in automobile heat exchangers were analyzed. Effective clad materials for heat exchanger tubes and fins were also evaluated. It was found that AA7072 should be applied as the cladding material for fin AA3003 and that AA4045 was suitable as a cladding material for tube AA3003 because this clad materials application was the most effective clad design to delay the occurrence of pinhole in the tube. Main factors influencing galvanic corrosion dissolution were found to be galvanic corrosion potential difference and galvanic corrosion current density.

• 한국연초학회지
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• 제16권2호
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• pp.181-190
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• 1994

Various active carbons were made from plant sources of coconut shell, pine tree, oak tree and lignite coal. Pore characteristics of these adsorbents were investigated. 1, With increasing activation time, specific surface area and pore volume increased, but the development of micropores was limited at a certain level. The average pore diameter, by BET, of coconut active carbon was 15.5-21.8$\AA$ and that of lignite carbon was 15.6-31.3$\AA$. The pore diameters of silica-gel, sepiolite and zeolite was 30.9$\AA$, 58.6$\AA$ and 55.7$\AA$, respectively. 2. The Horvath - Kawazoe micropore diameter of coconut shell active carbon was under 10.5$\AA$ and that of the other active carbon was under 20.9$\AA$ but silica-gel 33$\AA$, sepiolite 103 $\AA$ and zeolite was unexpectedly large to be 175$\AA$. From the difference between BET micropore diameter and Howath - Kawazoe diameter, it could be said that silica - gel has comparatively uniform pore diameter but sepiolite and zeolite have very uneven diameter. 3. Total pore volume of coconut shell active carbon was 0.27-1.04 cm3/g but that of the other active carbon, 0.23-0.62 cm3/g, was much lower than that of coconut shell active carbon. Hydrophilic adsorbent silica - gel and sepiolite showed big difference in specific surface area, but pore volumes of these were 0.47 and 0.56 cm3/g showing similar value and micropore volumes of these were, respectively, 0.06 cm3/g and 0.04 cm3/g. Total pore volume of zeolite was 0.1 cm3/g and that of micropore was only 0.02 cm3/g.

• 한국식품저장유통학회지
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• 제31권2호
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• pp.315-323
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• 2024

현재 항염증 활성에 대한 효능이 검증된 acemannan과 aloesin을 다양한 비율로 혼합하여 비율에 따른 항염증 효능을 확인하고자 본 연구를 진행하였다. 항염증 활성은 NO, PGE₂, TNF-α 및 IL-6 생성량 및 염증 관련 단백질인 iNOS, COX-2의 발현량에 대한 효능을 검증하였다. Acemannan과 aloesin 각각의 NO 생성 저해 활성 결과와 혼합 시료인 AA-1, AA-2, AA-3, AA-4, AA-5의 NO 생성 저해 활성 결과를 비교하였을 때, 혼합 시료가 더 우수한 NO 생성 저해 활성을 나타내는 것을 확인하였다. 이후 최적의 배합 비율을 찾기 위해 PGE₂, TNF-α 및 IL-6 생성량에 대해 측정하였다. 그 결과, 시료 5종 모두 최종농도인 100 ㎍/mL 농도에서 LPS 단독 처리군 대비 저해 효과가 나타났으며, 이 중 AA-2의 저해 효과가 가장 높은 것을 확인하여 western blot을 통한 염증 관련 단백질 발현량은 AA-2를 이용하여 실험을 진행하였다. 염증 관련 단백질인 iNOS 및 COX-2의 발현량을 측정 결과, AA-2는 농도 의존적으로 감소하였으며, 최종 농도인 100 ㎍/mL 농도에서 LPS 단독 처리군 대비 각각 25% 이상의 억제 효과가 나타나는 것을 확인하였다. 이러한 결과들을 토대로 acemannan과 aloesin을 다양한 비율로 배합하였을 때, 항염증 활성을 가진 것을 확인하였으며, 이 중 acemannan과 aloesin이 1:2의 비율로 혼합되었을 때 가장 높은 항염증 활성을 나타내었다. 결론적으로 acemannan과 aloesin을 혼합한 시료는 다양한 기능성 소재로써 활용이 가능하며, 이후 항염증 활성 실험들의 기초자료로도 활용이 가능한 것을 확인하였다.

• 한국임상수의학회지
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• 제14권2호
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• pp.308-318
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• 1997

The present experiment was performed in order to know the treatment effect of aquapuncture with hepatonics on recovery in artificially induced hepatic damaged dogs by carbon tetrachloride. The animals were divided into a control and two experimental groups (aquapuncture with taurine into Gan-su acupoint: Aa-I group and aquapuncture with taurine into blank acupoint in the thigh: Aa-II group). The changes of serum enzyme activities (ALT, AST and ALP), serum total protein contents, protein fractions and pathohistological findings of the liver were examined after application of aquapunctiuf treauent The results obtained through this experiment were summarized as follows : The serum ALT activities tendeded to decrease in experimental group compared with those of control group. Significances were detected at 5th (p<0.05) and 7th (p<0.05) day in Aa-I group and 7th day (p<0.05) in Aa-II group, respectively. Low value was fecund in Aa-I group compared with Aa-II groups but significance was not observed between two experimental groups. The serum AST activities in experimental group showed decreasing tendency compared with those of control group. Significances were observed at 2nd (p<0.05) and 5th (p<0.05) day in Aa-I group and 2nd (p<0.05) day in Aa-II groups respectively. Aa-I group showed lower values than those of Aa-II groups however, no significance was detected between experimental groups. The serum ALP activities of experimental group showed a slight decrease compared with those of control group, however, significance was not detected among all groups. The serum total protein content in experimental group showed tendency of increase compared with control group. Significance was found at 2nd day (p<0.05) in Aa-I group, but there was no significance in Aa-II group. Further significant increase of total protein content was seen at 1st day (p<0.05) in Aa-I group compared with Aa-II group. The change of serum albumin content in experimental group showed tendency of increase compared with control. Significant increases were detected at 1st (p<0.01) and 2nd (p<0.01) day in Aa-I group, respectively. Aa-II group showed increase compared with control groups but significance was not observed. Further significant increase was at 1st day (p <0.05) in Aa-I group compared with Aa-II group. The change of ${\beta} $-globulin in Aa-I group was slightly decreased compared with control group. Aa-II group was similar to controls but significance was not observed among all groups. The change of P-globulin content in Aa-I group showed tendency of increase compared with control and Aa-II group showed the tendency of decrease compared with control. The change of ${\gamma}$-globulin content experimental group showed tendency of increase compared with control, however, significance was not detected among groups. The change of A/G ratio in Aa-I group showed tendency of increase compared with control group and Aa-II group was similar to controls but no significance was found among groups. As for pathohistological observations the grade of hepatocellular vacuolized degeneration and necrosis in Aa-I group was milder than those of control and Aa-II groups and the change of Aa-II group was similar to that of control. Considering above finding collectively, it was thought that aquapuncture of Gan-su acupoint with hepatonics was more effective than aquapuncture of blank acupoint for the recovery of hepatic damage.