• KSBB Journal
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• 제20권2호
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• pp.129-132
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• 2005

본 연구는 헛개열매 추출물의 pH를 산성으로 조절한 산 가수분해 방법에 의하여 헛개열매 추출물에 배당체 형태로 존재하는 알코올분해 효능을 가진 생리활성물질 ((+)-dihydromyricetin)의 양을 증가시켰다. 반응온도 $80^{\circ}C$, 반응시간 4hr, 반응 pH 2.0에서 $124\%$의 알코올분해 효능이 증가하여 최적임을 알 수 있었다. 산 가수분해 전 후에 생리활성물질인 (+)-dihydromyricetin의 양이 $30\%$ 증가함을 알 수 있었으며, 또한 헛개열매 추출물에 포함되어 있는 고분자 물질이 분해됨을 확인할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제27권4호
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• pp.556-562
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• 2006

Studies on Ag nanoparticles grown on Highly Ordered Pyrolytic Graphite (HOPG) using HREELS provide different results for smaller and larger particle sizes corresponding to Ag coverages below and above 4 monolayers, respectively. For the larger particles, a positive frequency shift with decreasing particle size and a broadening of the plasmon resonance were observed with decreasing particle size, in line with previous studies on Ag on alumina. For the smaller particles, in contrast, a shift to lower energy with decreasing particle size, and a narrowing of the plasmon resonance with decreasing particle size can be found. The asymmetry of the Ag-features present for Ag coverages above 4 monolayers disappears for Ag coverages below 4 monolayers. The result for the smaller particles can be rationalized in terms of change of the particle growth mode with increasing particle size, which corroborates our STM data, as well as electronic effects due to the metal/support charge transfer.

• 수산경영론집
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• 제36권1호
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• pp.155-166
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• 2005

Since 1980's, fishery household population have been continuously in a down slope with a 5$\%$ annual decreasing rate in Korea. With a particular situation that the scale of over 60s population has been soaring compared with that of under 16 aged population plunging, some difficulties have been raised with the respect of labor supply into fishery communities. This study is aimed at analyzing the tendency of fisheries population with the change of economic development rates and prospect a future fisheries population with the consideration of present decreasing rate. Model results indicate that the tendency of future fishery household population would be decreased by 4.96$\%$ annually through a decade from 2000. Interestingly, it is predicted that the decreasing rate of male fishery household population would be faster than that of female. Consequently, women would hold a greater part in Fishery household population in 2010. In addition, the fishery household population of 40s and 50s would increase from 36$\%$ to 49$\%$, that of over 60s from 21$\%$ to 37$\%$. In conclusion, as a population over 40's encompass almost 90$\%$ in the total population, the fishing communities have a difficulty in shortage of the young workforce.

• 대한기계학회논문집
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• 제13권4호
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• pp.670-679
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• 1989

본 연구에서는 항공기 구조용 재료로서 널리 사용되는 국산 고장력 7075-T73 알류미늄 합금을 준비하고 일정진폭하중 및 단일과대하중에 의한 피로균열 진전거동에 미치는 두께의 영향과 이의 기구를 검토하였다.

• 한국안전학회지
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• 제17권4호
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• pp.45-51
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• 2002

In this study, the fracture characteristics of carbonized silicon grinding wheels were examined with tensile, compression, impact and bending test. The experiment was performed for the various grinding wheels with grain size #46, #80, and grade H, L, P, and one vitrified bond and one structure No.7. Also the centrifugal fracture rpm of carbonized silicon grinding wheels were measured and compared with the calculated values for the various wheel diameters and thicknesses. The results showed that the fracture tensile strength was $1.5~2.0Kg_f/mm^2$, and it was increased by decreasing grain size and increasing grade. The fracture compression loads were $1,600~3,000Kg_f$, and the inner stress was higher than outer's. And the absorption energy of impact test was 3.3~4.7 J, and it was increased by decreasing grain size but it was not effected by grade. The fracture bending stress was $0.1~0.2Kg_f/mm^2$, and it was increased by decreasing grain size and increasing grade. The centrifugal fracture rpm of carbonized silicon grinding wheel was about 8,500~12,000 and agreed well with the calculated value, and it was increased by decreasing diameter. However, it was almost constant for the reduction of wheel thickness.

• 열처리공학회지
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• 제3권2호
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• pp.20-31
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• 1990

This investigation has been carried out to make clear the effect of deformation temperature, strain rate and grain size on the tensile properties of 304L stainless steel. Tensile properties of the metastable austenitic 304L steel remarkably influenced by deformation temperature. Tensile strength increased with decreasing deformation temperature and the elongation showed maximum value near $40^{\circ}C$. In order to obtain the high elongation, a large amount of deformation is available in austenite before martensitic transformation and the martensite has to be induced gradually. Tensile strength and elongation increased with decreasing grain size. The temperature representing the maximum elongation shifted to low temperature and the peak width of elongation became broaden with decreasing austenite grain size. The volume fraction of strain induced martensite decreased with decreasing austenite grain size. As the strain rate increase, the temperature representing the maximum elongation value shifted to high temperature and volume fraction of strain induced martensite decreased.

• 융합경영연구
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• 제6권3호
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• pp.10-13
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• 2018

Purpose - On the basis of discussing the network economy concept and the commentary of the marginal revenue decreasing of traditional economic theory, The concept of network economy has just been put forward in recent years. The reason why such a concept appears is that the information technology, marked by computer network, plays an increasingly important role in economic activities. Some people define network economy as an economic form based on network technology and human capital. this paper points out network economy existing the marginal revenue increasing and analyzes the reasons that influencing the marginal revenue increasing. Research design, data, methodology - The network economy has fundamentally changed the traditional economic laws. The economic basis of industrial society is the law of incremental marginal cost, which reflects the socialization of high cost in industrial society. Results - As the number of network members increases, the value of the network increases explosively, and the value increases attract more members to join, resulting in more returns. Conclusion - In conclusion, network economy has changed many aspects of traditional economy, resulting in decreasing marginal cost, decreasing transaction cost in and out of enterprise organizations, and making the effect of increasing scale compensation more prominent. This is of great significance to the information construction in China.

• 상하수도학회지
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• 제21권4호
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• pp.421-428
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• 2007

Many engineering problems on the pipeline flow use continuity, energy, friction loss head equation. To calculate friction loss head in a pipeline, Darcy-Weisbach and many average velocity equations can be used and Hazen-Williams equation is used frequently in the pipe network for the water supply systems. Darcy-Weisbach equation is a general one acquired from applying Bernoulli's equation in the pipeline flow and Hazen-Williams equation is a experimental one in case that pipe velocity is below 3m/sec and pipe diameter is over 50mm. In this study, comparing Darcy-Weisbach with Hazen-Williams equation, relation f and C that are expressed as roughness coefficients of those equations is explained. Next, head losses calculated from using those equations are compared and those are applied in realistic pipelines. Comparing f with C, the f is decreasing linearly according to increase of the Reynolds number Re and increasing in case the C is decreasing. additionally, the C is increasing up to a point and then is decreasing according to increase of the Re. Next, the C is increasing and Re's range for increase of the C lengthens in case of decreasing of the relative roughness ${\varepsilon}/d$. Comparing head losses acquired from the two equations, head loss appears large in case that the C is decreasing and the ${\varepsilon}/d$ is increasing. additionally, Head loss calculated by the Darcy-Weisbach equation varies larger than one by Hazen-Williams equation in regard of the Re. Next, change aspect of head loss acquired by the C is distinguished more clearly than the one by the ${\varepsilon}/d$.

• 한국환경과학회지
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• 제25권2호
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• pp.295-310
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• 2016

In this study, changes in daily temperature range were investigated using daily maximum and minimum temperatures of Busan and Daegu for last 81 years (1934-2014), and also characteristics of daily temperature range and seasonal fluctuations by urbanization were examined. First, elapsing changes showed a lower decreasing trend in Busan ($0.32^{\circ}C$) than Daegu ($1.28^{\circ}C$) for last 81 years. Daily temperature range showed the highest rise in winter in both Busan and Daegu. Second, daily temperature range due to urbanization showed that Busan had a pronounced decreasing trend before urbanization meanwhile Daegu showed the same trend after urbanization. On seasonal changes, the results of Busan showed a decreasing trend in summer before urbanization, and in autumn after urbanization. For Daegu, the results showed a decreasing trend in spring before urbanization, and in winter after urbanization. Seasonal fluctuations of Busan showed little difference in the pre and post-urbanization, except in winter and summer. There was large difference in daily temperature range in winter after urbanization, and in summer before the urbanization. The results in Daegu showed that there was decreasing trend of daily temperature range in all seasons after urbanization.

• 대한한의학회지
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• 제16권1호통권29호
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• pp.403-418
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• 1995

In order to study the effects of Chungsimgangwhawhan on blood pressure in normal rats and rabbits, and hyperlipidemia induced by 1% cholesterol diet, triton WR-1339, and 75% fructose in mice and rats, the amount of total cholesterol, triglyceride, phospholipid and blood pressure were measured. The results were as follows : 1. After per os medication of Chungsimgangwhawhan, blood pressure in rats were increased but were not significant. 2. Chungsimgangwha-Whan showed strong effects on decreasing blood pressure, depending on the concentration in blood vessels of rabbits. 3. In the model of hyperlipidemia induced by 1% cholesterol diet in mice, Chungsimgangwhawhan showed decreasing effects on total cholesterol level in serum significantly (p<0.05) depending on the concentration, and on triglyceride (p<0.01) and phospholipid level (p<0.001) in serum. 4. In the model of hyperlipidemia induced by triton WR-1339 in rats, Chungsimgangwhawhan showed mild decreasing effects on total cholesterol level in serum, but was not significant. 5. In the model of hyperlipidemia induced by 75% fructose in rats, Chungsimgangwhawhan showed decreasing effects on total cholesterol and triglyceride level in serum significantly(p<0.01) depending on the concentration. According to the above results, Chungsimgangwhawhan showed significant decreasing effects on blood pressure and hyperlipidemia, and it is considered that it is appropriate to apply for hypertension and hyperlipidemia.