• 한국초지조사료학회지
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• 제1권1호
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• pp.2-9
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• 1978

A review of factors influencing grass and clover establishment, survival and yield at oversowing was made from the experimental results of home and abroad. The following conclusions are considered: (1) The existing vegetation present at oversowing appeared to be the most critical factor reducing establishment and survival of grass. Therefore, it is essential to check competition from the native vegetation before oversowing. (2) Although lime had comparatively little effect on yield of grassland, the general effect of lime should be more emphasized under our acid soil conditions to promote the availability of all the essential elements and the growth of microorganisms, and to reduce the toxic effects of nutrients. One to two tons of lime per ha at oversowing would be useful. (3) Phosphorus is one of the nutrients most generally deficient in grassland soils of Korea, consequently, this nutrients applied at oversowing is very effective. Application as much as 200kg of phosphorus per ha would be essential. (4) The effect of nitrogen on the establishment and survival of grass depends on the amount and density of the herbage present. The use of nitrogen in dense herbage adversely affected grass establishment and survival, possible because the fertilizer stimulated the growth of the eisting herbage. Around 40kg of nitrogen per ha may be enough at oversowing (5) Potassium is not as universally deficient in soils of native grassland as phosphorus. Therefore, it cannot be over-emphasized at oversowing. Studies determinig the optimum amount of potassium at of oersowing are needed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.31-35
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• 2004

The speed competition of optical disk drive has been accelerated with the fast advancement of its storage density and data transmission technology. The continuous increase of the spinning speed of CD meets the unexpected and catastrophic failure of disk during the operation. The effect of its thickness and outer radius of disk were investigated to reduce stresses and J-integral around the crack tip. The effect of its thickness was considered ahead of the crack tip. In the effect of outer radius of disk, linear elastic fracture mechanics was used to obtain the critical crack length, which indicates the onset length for unstable crack growth. This approach is so significant as to detect the growing crack by disk drive before the catastrophic failure, which will provide the standard size of its safety for high-speed disk drive.

• 한국주조공학회지
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• 제17권3호
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• pp.302-308
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• 1997

In spite of the fact that magnesium has low density and good machinability, its applications are restricted as a structural engineering material because of the poor strength, ductility, and corrosion resistance of the conventional ingot metallurgy alloys. Such properties can be improved by microstructural refinement via rapid solidification processing. In this study, Mg-5wt%Zn alloys have been produced as continuous strips by the melt overflow technique. In order to evaluate the influence of the cooling rate on the grain refinement and mechanical properties, seven different thickness strips were produced by means of controlling the speed of the cooling wheel. Then the microstructual observations were undertaken with the objective of evaluating the grain refinement as function of the cooling rate. The tremendous increase in hardness of Mg-Zn alloy was mainly due to the refinement of the grain structure by the effect of rapid solidification. The formation of intermetallic phases on the grain boundaries may have a positive effect on the corroion resistance. Therefore, despite competition from many other developments, the rapid solidification process emerges as a valuable method to develop superior and commercially acceptable magnesium alloys.

• Molecules and Cells
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• 제26권4호
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• pp.409-414
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• 2008

The cholesteryl ester transfer protein (CETP), a key player in cholesterol metabolism, has been shown to promote the transfer of triglycerides from very low density lipoprotein (VLDL) and low density lipoprotein (LDL) to high density lipoprotein (HDL) in exchange for cholesterol ester. Here we demonstrate that farnesoid X receptor ${\alpha}$ ($FXR{\alpha}$; NR1H4) down-regulates CETP expression in HepG2 cells. A $FXR{\alpha}$ ligand, chenodeoxycholic acid (CDCA), suppressed basal mRNA levels of the CETP gene in HepG2 cells in a dose-dependent manner. Using gel shift and chromatin immunoprecipitation (ChIP) assays, we found that $FXR{\alpha}$ could bind to the liver X receptor ${\alpha}$ ( $LXR{\alpha}$; NR1H3) binding site (LXRE; DR4RE) located within the CETP 5' promoter region. $FXR{\alpha}$ suppressed $LXR{\alpha}$-induced DR4RE-luciferase activity and this effect was mediated by a binding competition between $FXR{\alpha}$ and $LXR{\alpha}$ for DR4RE. Furthermore, the addition of CDCA together with a $LXR{\alpha}$ ligand, GW3965, to HepG2 cells was shown to substantially decrease mRNA levels of hepatic CETP gene, which is typically induced by GW3965. Together, our data demonstrate that $FXR{\alpha}$ down-regulates CETP gene expression via binding to the DR4RE sequence within the CETP 5' promoter and this $FXR{\alpha}$ binding is essential for $FXR{\alpha}$ inhibition of $LXR{\alpha}$-induced CETP expression.

• 한국산림과학회지
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• 제89권1호
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• pp.49-54
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• 2000

임분수준(林分水準) 생존예측모형(生存豫測模型)이 개발(開發)되었으며, 이 모형(模型)은 녹병(綠病)(Cronartium quercuum [Berk.] Miyabe ex Shirai f. sp. fusiforme)의 발생율(發生率)을 모형(模型)에 포함하였으며 그리고 녹병(綠病)에 감염(感染)되지 않은 단계(段階)의 임목(林木)들이 감염(感染)되는 단계(段階)로의 전이(轉移)가 허용(許容)되는 특징(特徵)을 가지고 있다. 12년간(年間) 장기적(長期的)으로 매년(每年) 측정(測定)된 영구적(永久的)인 실험(實驗)plots의 다양(多樣)한 데이터베이스를 이용(利用)하였으며, 인공조림(人工造林)된 테에다소나무임분(林分) 내에서 자연적(自然的)으로 발생(發生)된 활엽수(闊葉樹)들과의 종간경쟁(種間競爭)이 소나무임분(林分)의 생존예측(生存豫測)에 미치는 영향(影響)을 분석(分析)하였다. 본(本) 연구(硏究)의 결과(結果)로서 임분수준(林分水準)의 생존예측모형(生存豫測模型)은 지위지수(地位指數)와 활엽수(闊葉樹)의 흉고단면적(胸高斷面績) 밀도(密度)와의 유의(有意)한 영향(影響)이 생존예측모형(生存豫測模型)에서 나타났다. 지위지수(地位指數)와 활엽수(闊葉樹)의 밀도(密度)가 증가(增加)함에 따라서 조림(造林)된 테에다소나무임분(林分)의 미래(未來) 생존(生存) 본(本) 수(數)는 뚜렷히 감소(減少)하는 경향을 나타내었다.

• 대한환경공학회지
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• 제22권2호
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• pp.251-264
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• 2000

합성폐수의 전기분해에 의한 전류밀도, 체류시간, 전극간격 및 $Cl^-/COD_{Cr}$ 비에 대한 유기물질 제거 특성을 조사하기 위한 실험을 수행하였다. 양극판은 티타늄에 이산화이리듐을 전착한 $Ti/IrO_2$ 극판으로 하였으며, 음극판은 스테인리스 스틸판을 사용하였다. 판형태와 망형태의 전극을 사용한 경우 $COD_{Cr}$ 제거율은 비슷하게 나타났으나, 전력비는 판형태보다 망형태의 전극에서 저렴한 것으로 나타났다. $COD_{Cr}$ 제거율 70 %를 얻는데 소요되는 $Cl^-/COD_{Cr}$ 비는 약 $1.3kgCl^-/kgCOD_{Cr}$으로 나타났으며, $COD_{Cr}$을 완전히 제거하는데 약 $2.2kgCl^-/kgCOD_{Cr}$이 필요하였다. 유기물질의 제거는 전류밀도, 체류시간 및 $Cl^-/COD_{Cr}$ 비에 따라 높게 나타났고, 전극간격에는 반비례하였으며, 운전인자와 제거율과의 관계는 아래와 같이 나타났다. $$COD_{Cr}(%)=80.0360(Current\;density)^{0.4451}{\times}(HRT)^{0.8102}{\times}(Gap)^{-0.4915}{\times}(Cl^-/COD_{Cr})^{0.5805}$$ 유기물질과 질소를 동시에 전기분해할 경우 두 물질의 산화는 경쟁관계에 있으며, 암모니아성 질소를 산화하는데 우선적으로 작용하여 유기물질의 제거는 낮아지지만, 알칼리도 첨가에 의해 유기물질 제거가 증가하였다.

• Macromolecular Research
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• 제11권2호
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• pp.104-109
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• 2003

A microcellular, which combines a rubber with the conventional formulation of styrene/divinylbenzene/sorbitan monooleate/water system, was prepared using high internal phase emulsion (HIPE) polymerization. Although the open microcellular foam with low density from the conventional HIPE polymerization shows highly porous characteristics with fine, regular and isotropic structure, the one having much smaller cell size is desirable for various applications. In this study, a polybutadiene was introduced to reduce the cell size with comparable properties. Major interests were focused on the effects of rubber concentration and agitation speed on the cell sizes and compression properties. Scanning electron microscopy was used to observe the microcellular morphology and compression tests were conducted to evaluate the stress-strain behaviors. It was found that the cell size decreased as rubber concentration increased, reflecting a competition between the higher viscosity of continuous phase and the lower viscosity ratio of dispersed to continuous phases due to the addition of high molecular weight rubber into the oil phase of emulsion. A correlation for the average cell size depending on agitation speed was attempted and the result was quite satisfactory.

• 한국광물학회지
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• 제11권2호
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• pp.106-116
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• 1998

The adsorption of Cs-137 and Sr-90 onto kaolinite in prescence of major groundwater cations (Ca2+, K+, Na+) with different concentrations was simulated by using triple-layer surface complexation model (TL-SCM). The site density (8.73 sites/nm2) of kaolinite used for TL-SCM was calculated from it's CEC and specific surface area. TL-SCM modeling results indicate that concentrations dependence on 137Cs and 90Sr adsorption onto kaolinite as a function of pH is best modeled as an outer-sphere surface reaction. This suggests that Cs+ and Sr2+ are adsorbed at the $\beta$-layer in kaolinite-water interface where the electrolytes, Nacl, KCl and CaCl2, bind. However, TL-SCM results on Sr adsorption show a discrepancy between batch data and fitting data in alkaline condition. This may be due to precipitation of SrCO3 and complexation such as SrOH+. Intrinsic reaction constants of ions obtained from model fit are as follows: Kintcs=10-2.10, KintSr=10-2.30, KintK=10-2.80, KintCa=10-3.10 and KintNa=10-3.32. The results are in the agreement with competition order among groundwater ions (K+>Ca2+>Na+) and sorption reference of nuclides (Cs-137>Sr-90) at kaolinite-water interface showed in batch test.

• 한국BIM학회 논문집
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• 제11권2호
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• pp.43-53
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• 2021

The 'public agency oil joint purchase system' was introduced to lower public sector oil prices and contribute to the stability of the overall consumer oil market. The present study used spatial regression to analyze the factors affecting domestic gasoline price, focusing on the impact of potential implicit collusion among gas stations in determining domestic gasoline prices. Also, this study investigated the effect the location characteristics of the market convention gas stations and government offices on the pressure of price competition in the market and the gasoline price at general gas stations. To summarize the results of the spatial lag model (SLM), the individual characteristics of gas stations such as convenience stores (+), self-fuelling (-), commercial areas (+), subway stations (+), population density (-), and sales (-) are correlated to gasoline prices at gas stations, and the institutional location factors of gas stations (+) affected the average of 9 won per liter, 11 won per liter. In order to solve these problems, the establishment of a monitoring system reflecting the location characteristics of the region and the ongoing review of the system should be carried out. In addition, separate, expanded and promotional measures should be prepared for the convenience of general and public oil buyers.

• 한국작물학회지
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• 제49권4호
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• pp.284-288
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• 2004

The response of dissolved oxygen (DO) concentrations caused significant change in root number, root length, coleoptile length, shoot length and leaf age of seedlings. The genotypic difference in the effect of DO also highly significant (P<0.01) for all of the seedling traits. The number and length of root were extremely inhibited at the condition of $0.39\pm0.09$ DO concentration. While the coleoptile elongated markedly in the lowest DO concentrations, the shoot did not develop. The root growth was improved slightly at the $1.39\pm0.27mg L^{-1}$, however, there were no difference among genotypes at these two low DO concentrations. As the DO concentration become higher, the growth of root and shoot was improved remarkably. Root number, root length and shoot length was significantly different between $20\;and\;30^{\circ}C$ in DO rich and normal conditions, the development of those traits were apparently accelerated in high water temperature, however those traits of seedlings in DO deficiency were not different between the two temperatures except for shoot length. On the other hand the coleoptile length was not affected by the stagnant water temperature; it was stimulated by the low DO concentration. The competition of DO was greater as the seedling density was increased in the stagnant water, therefore the seedlings grown under high density have long and white coleoptiles, and the growth of roots and shoots was retarded severely.