• 한국초등수학교육학회지
• /
• 제20권2호
• /
• pp.283-309
• /
• 2016

본 연구는 초등수학영재를 대상으로 곱셈의 문제 상황에 따른 곱셈 개념에 대한 이해 정도를 분석한 것으로, 초등수학영재의 수학적 개념 지도와 나아가 초등수학에서의 곱셈 개념을 지도하는 방법에 대한 시사점을 이끌어내기 위한 것이다. 이를 위해 곱셈의 도입과 관련된 초등수학의 내용을 교육과정별로 분석하여 학생들이 초등수학에서 곱셈의 개념을 어떻게 학습하고 있는지를 먼저 살펴보았다. 또한 곱셈의 문제 상황과 그 개념에 대한 초등수학영재의 이해를 알아보기 위해 B대학교 과학영재교육원 초등수학반 영재사사과정 학생 10명을 대상으로 곱셈에서의 문장제 설정의 과정을 포함하는 검사와 면담을 실시하였다. 그 결과 학생들은 2007 개정 교육과정에서 배 개념을 중심으로 곱셈을 학습했음에도 불구하고 배 개념보다는 동수누가의 곱셈 상황을 제시하는데 보다 익숙했으며, 개념 이해에서 곱셈을 동수누가로만 이해하고 있는 학생의 비율 또한 높게 나타났다. 이에 따라 초등수학을 지도하는 과정에서 기본적인 연산 개념에 대한 지도 방법을 재검토해볼 필요가 있으며, 곱셈 개념 지도에서 다양한 곱셈의 문제 상황을 통해 학생들이 곱셈의 개념을 정확하게 이해하는 것이 요구된다.

• Journal of Microbiology and Biotechnology
• /
• 제16권12호
• /
• pp.1874-1881
• /
• 2006

Flocculation of Candida tropicalis HY200 was systemically investigated to elucidate its mechanism, and used for cell cycles in repeated-batch cultivations for the production of xylitol from xylose. Flocculation occurred only after the late exponential phase of growth in the culture media and buffer within the narrow pH range of 3.0-5.0. The flocculation was completely inhibited by treatments of cells with proteases and partially reduced by treatments with carbohydrate-hydrolyzing enzymes and by the presence of mannose and glucose. The addition of calcium ions significantly enhanced the flocculation during cultivation, which was completely abolished by the addition of EDTA. The flocculent yeast HY200 provided repeated-batch cultivations employing cell recycles by flocculation over 6 rounds of cultivation for the production of xylitol from xylose, resulting in a relatively high productivity of averaged 4.6 g xylitol/l h over six batches and maximal 6.3 g xylitol/l h in the final sixth batch. Cell recycle by flocculation was fast and convenient, which could be applicable for the industrial scale of xylitol production.

• Journal of Microbiology and Biotechnology
• /
• 제21권9호
• /
• pp.972-978
• /
• 2011

In this study, we investigated the performance of an immobilized ${\beta}$-galactosidase inclusion bodies-containing Escherichia coli cell reactor, where the cells were immobilized in alginate beads, which were then used in repeated-batch operations for the hydrolysis of o-nitrophenyl-${\beta}$-D-galactoside or lactose over the long-term. In particular, in the Tris buffer system, disintegration of the alginate beads was not observed during the operation, which was observed for the phosphate buffer system. The o-nitrophenyl-${\beta}$-D-galactoside hydrolysis was operated successfully up to about 80 h, and the runs were successfully repeated at least eight times. In addition, hydrolysis of lactose was successfully carried out up to 240 h. Using Western blotting analyses, it was verified that the ${\beta}$-galactosidase inclusion bodies were sustained in the alginate beads during the repeated-batch operations. Consequently, we experimentally verified that ${\beta}$-galactosidase inclusion bodies-containing Escherichia coli cells could be used in a repeated-batch reactor as a biocatalyst for the hydrolysis of o-nitrophenyl-${\beta}$-D-galactoside or lactose. It is probable that this approach can be applied to enzymatic synthesis reactions for other biotechnology applications, particularly reactions that require long-term and stable operation.

• Biomolecules & Therapeutics
• /
• 제19권1호
• /
• pp.45-51
• /
• 2011

These experiments were designed to use typical makers from behaviors and molecular basis in addicted animals of morphine and cocaine. Morphine has been widely abused with a high physical dependence liability. Morphine withdrawal activates the intracellular cAMP signaling pathway and further leads to changes in the expression of the cAMP response element binding protein (CREB), which may be important to the development and expression of morphine dependence. From these experiments, repeated morphine (10 mg/kg, twice per day for 7 days) developed physical dependence. Withdrawal signs were precipitated by naloxone and also increased the expression of the CREB. In addition, repeated exposure of cocaine (15 mg/kg) to mice develops locomotor sensitization and produced lasting behavioral sensitivity. Cocaine- and amphetamine-regulated transcript peptide (CART) peptide was up-regulated by repeated administration of cocaine in the striatum. Therefore, repeated morphine induced the development of physical dependence and increased pCREB. In addition, repeated cocaine induced locomotor sensitization and over-expressed CART peptide. In conclusion, the development of physical dependence and pCREB for morphine, and locomotor sensitization and CART peptide over-expression for cocaine would be useful markers to predict the abuse potential of opioid analgesics and pychostimulant drugs in animals, respectively.

• 한국발생생물학회지:발생과생식
• /
• 제25권4호
• /
• pp.213-223
• /
• 2021

Controlled ovarian hyperstimulation (COH) is routinely used in the in vitro fertilization and embryo transfer (IVF-ET) cycles to increase the number of retrieved mature oocytes. However, the relationship between repeated COH and ovarian function is still controversial. Therefore, we investigated whether repeated ovarian stimulation affects ovarian aging and function, including follicular development, autophagy, and apoptosis in follicles. Ovarian hyperstimulation in mice was induced by intraperitoneal injection with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG). Mice subjected to ovarian stimulation once were used as a control group and 10 times as an experimental group. Repeated injections with PMSG and hCG significantly reduced the number of primary follicles compared to a single injection. The number of secondary and antral follicles increased slightly, while the number of corpus luteum increased significantly with repeated injections. On the other hand, repeated injections did not affect apoptosis in follicles associated with follicular atresia. The expression of autophagy-related genes Atg5, Atg12, LC3B, and Beclin1, cell proliferation-related genes mTOR, apoptosis-related genes Fas, and FasL was not significantly different between the two groups. In addition, the expression of the aging-related genes Dnmt1, Dnmt3a, and AMH were also not significantly different. In this study, we demonstrated that repeated ovarian stimulation in mice affects follicular development, but not autophagy, apoptosis, aging in ovary. These results suggest that repetition of COH in the IVF-ET cycle may not result in ovarian aging, such as a decrease in ovarian reserve in adult women.

• 대한토목학회논문집
• /
• 제10권1호
• /
• pp.125-134
• /
• 1990

본연구(本硏究)는 집중대량(集中大量)으로 부산(副産)되어 막대한 경비(經費)를 들여 폐기(廢棄)처리 되고 있는 석탄회(石炭灰)를 도로로반재(道路路盤材)로서 활용하고자 시멘트를 첨가(添加)하여 반복하중(反復荷重)을 가하였을 때의 변형특성(變形特性)에 대해서 영동화력발전소(嶺東火力發電所)와 영월화력발전소(寧越火力發電所)에서 발생(發生)되는 석탄회(石炭灰)를 대상으로 검토(檢討)한 것이다. 석탄회(石炭灰)에 시멘트 첨가율(添加率)이 증가(增加)할 수록 일축압축강도(一軸壓縮强度)는 직선적(直線的)으로 증가(增加)하였고, 시험 조건인 재하회수(載荷回數)에서는 탄성계수(彈性係數)가 감소하였으며, 압축강도(壓縮强度)는 약 21% 정도의 증가를 보였다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제14권4호
• /
• pp.148-153
• /
• 2010

각종 건설현장에서 구조재료로 사용되고 있는 콘크리트는 레미콘 공장에서 배합되어 레미콘 트럭에 의해 현장까지 운송 타설되는 형태로 공급되고 있다. 그러나 콘크리트가 현장까지 운송되는 동안 교통 체증, 기후 및 기타 여러 영향으로 인해 적정한 슬럼프의 유지가 곤란한 경우를 겪게 된다. 이럴 경우 콘크리트의 적정한 슬럼프 유지를 위해 혼화제를 첨가하게 된다. 그러나 실제 현장에 배달되는 레미콘의 경우는 트럭기사들이 레미콘을 쏟아 낼 때 슬럼프치가 부족하면 혼화제 대신 물을 추가로 넣어 비빈 후 타설을 하여 강도저하의 치명적 원인을 제공하는 경우가 발생되기도 한다. 이는 설계시 결정되어 모든 구조물 설계에 사용된 설계강도에 크게 미달하는 콘크리트 사용하게 됨으로써 추후 심각한 문제를 야기할 수 있다. 따라서 본 연구에서는 레미콘에 추가로 물을 첨가하는 문제를 해결하고자, 콘크리트에 현장에서 많이 사용되고 있는 혼화제를 정해진 시간간격으로 추가하는 것이 굳은 혹은 굳지 않은 콘크리트의 역학적 특성에 미치는 영향을 검토하여 콘크리트의 슬럼프 유지를 위한 적정한 혼화제 사용에 대한 근거자료를 제시하고자 한다.

• Journal of information and communication convergence engineering
• /
• 제20권4호
• /
• pp.235-241
• /
• 2022

A dispersion map was proposed to improve the compensation effect of a distorted WDM (wavelength division multiplexed) channel in a dispersion-managed link coupled with optical phase conjugation. The dispersion map is an origin-symmetric structure around the optical phase conjugator in the middle of the transmission path. In addition, the dispersion map has a form in which a constant dispersion accumulation pattern is repeated regularly. Through simulation, we confirmed that the application of the origin-symmetric dispersion map with a repetitively shaped configuration was more effective in compensating for the distorted WDM channel than in the dispersion-managed link with a conventional dispersion map. In addition, we confirmed that the compensation effect could be increased when the cumulative dispersion distribution of the origin-symmetric distribution map had a positive value in the first half section and a negative value in the second half section. Further, we observed that as the number of repeated dispersion accumulation patterns increased, the residual dispersion per span should also be increased.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2005년도 생물공학의 동향(XVII)
• /
• pp.319-323
• /
• 2005

This study is concerned with development of efficient culture methods for lactic acid fermentation of Lactobacillus sp. RKY2. The cell-recycle repeated batch fermentation using cheese whey and corn steep liquor as raw materials was tried in order to further enhance the productivity of lactic acid. In addition, fermentation efficiencies could be considerably enhanced by cell-recycle continuous culture. Through the cell-recycle repeated batch fermentation, lactic acid productivity was maximized to 6.34 $g/L{\cdot}h,$ which corresponded to 6.2 times higher value than that of the batch fermentation. During the cell-recycle continuous fermentation, the last dry cell weight at the end of fermentation could be increased to 25.3 g/L.

• 한국도로학회논문집
• /
• 제10권1호
• /
• pp.49-62
• /
• 2008

본 논문은 대표적인 도로상 지반재료에 대한 반복하중 작용시 변형특성을 평가하였다. 회복변형과 영구변형의 중요한 두 가지 계수를 반복재하 삼축시험의 결과를 통하여 추정하였다. 또한 응력상태와 환경조건, 그리고 재료특성을 각각 고려하여 영향을 비교 분석하였다. 국내 도로지반재료는 억물림과 변형후 회복적인 특성으로 인해 재료의 영구변형은 일정한 증가율을 가지며 이후 거의 일정변형율로 수렴하는 것으로 관측되었다. 연구결과선정된 영구변형 모델과 계수는 일정한 회수의 반복하중이 가해진 이후 변형을 예측하는데 적합함을 알 수 있었다.