• 컴퓨터교육학회논문지
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• 제16권2호
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• pp.49-60
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• 2013

이 연구는 질적 접근에 기반하여 디지털교과서 활용수업에서 나타나는 핵심성공요인들을 귀납적으로 분석하고자 하였다. 연구대상은 디지털교과서 연구학교로 지정된 인천의 D초등학교 5학년 1개 학급으로 6차시 분의 수업을 촬영하였으며, 교사 1명과 학생 3명을 대상으로 심층 인터뷰를 실시하였다. 관찰한 수업내용과 인터뷰 자료를 통해 도출된 자료들의 내용분석 방법으로는 근거이론에 기반한 코딩 방법을 사용하였으며, 자료분석 도구로는 질적자료 분석도구인 Nvivo 8.0을 활용하였다. 연구결과, 디지털교과서 활용 수업의 핵심성공요인은 '멀티미디어 기능을 활용한 체계적이고 다양한 교수학습활동', '구체적 안내 및 도움', '정보 리터러시 관련 질의응답', '물리적인 시스템과 장비의 안정성', '활발한 협력학습과 상호작용', '개별적 자기주도학습', '정서적/신체적 변화의 고려', '가용자원을 고려한 선택과 집중 전략' 등으로 나타났다.

• Oncology Letters
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• 제17권3호
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• pp.3589-3598
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• 2019

Colorectal cancer (CRC) is a complex disease involving numerous genetic abnormalities. One of the major characteristics of CRC is enhanced Wnt signaling caused by loss-of-function mutations in the adenomatous polyposis coli (APC) gene. Previously, it has been demonstrated that the majority of malignant phenotypes following APC deletion in adult murine small intestines could be rescued when Myc, a downstream target of the Wnt pathway, was deleted. This indicated that Myc is a critical regulator of CRC development following APC loss. Previous studies reported that cyclic adenosine 3',5'-monophosphate (cAMP) can influence the AKT/mammalian target of rapamycin (mTOR) survival pathway in cancer and Myc is a critical downstream molecule of AKT/mTOR signaling. Phosphodiesterase 4D (PDE4D), a member of the cAMP-specific PDE4 family, has been associated with drug resistance in CRC. However, the association between PDE4D and Myc remains unclear. To investigate the potential role of PDE4D in Myc regulation in CRC, the present study evaluated the expression levels of PDE4 subtypes in DLD-1 CRC cells. Additionally, the effects of PDE4 inhibitors on Myc expression and oncogenic properties were analyzed by western blot analysis, reverse transcription-quantitative polymerase chain reaction, colony formation and soft agar assays. It was demonstrated that cAMP/PDE4D signals serve a critical role in regulating Myc expression in DLD-1 CRC cells. Furthermore, PDE4D was identified to be a main hydrolyzer of cAMP and suppression of PDE4D using selective inhibitors of PDE4 increased intracellular cAMP levels, which resulted in a marked decrease in the oncogenic properties of DLD-1 cells, including colony formation, cell proliferation and anchorage-independent growth. Notably, the current data imply that cAMP represses Myc expression via the downregulation of AKT/mTOR signaling, which was abolished by high PDE4D activities in DLD-1 cells. Additionally, a natural polyphenol resveratrol in combination with forskolin elevated the concentration of cAMP and enhanced the expression of Myc and the malignant phenotype of DLD-1 cells, reproducing the effect of known chemical inhibitors of PDE4. In conclusion, the present study identified that cAMP/PDE4D signaling is a critical regulator of Myc expression in DLD-1 and possibly other CRC cells.

• Asian-Australasian Journal of Animal Sciences
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• 제3권1호
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• pp.15-20
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• 1990

The nutritional status of trace minerals in cattle of Java in Indonesia was investigated by evaluating Cu, Fe, Mo, Zn and Mn concentrations in diets and livers, and Cu and Zn concentrations in blood plasma. Investigations were conducted on Jonggol (West Java), Malang (East Java) and Mojokerto (East Java) in both the rainy and the dry seasons in 1988. In Jonggol, low Cu concentrations in diets showing 7.1 mg/kg in the rainy season and 10.9 mg/kg in the dry season were observed and all plasma samples showed Cu concentrations below the critical level ($0.65{\mu}g/ml$). Thirty percent of the liver samples in Malang and 54% of those in Mojokerto showed lower Cu concentrations than the critical level (75 mg/kg on a dry matter basis). Fe concentrations in diets from the three regions showed a wide variation of values ranging from 249 to 30,000 mg/kg. A large amount of Fe was accumulated in livers from Malang and Mojokerto, giving average concentrations of 498 mg/kg. Zn concentration in diet and plasma samples were close to the borderline and some Zn concentration in these samples showed deficient levels. Mo and Mn concentrations in diets and livers showed normal levels.

• 한국수자원학회논문집
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• 제41권9호
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• pp.863-872
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• 2008

본 연구에서는 환형수조를 이용한 일련의 퇴적실험을 수행하여, 염수조건(32 %o)에서의 고령토 퇴적물의 퇴적특성 산정 및 퇴적특성에 미치는 초기농도의 영향을 분석 검토하였다. 바닥전단응력을 변화시키면서 각기 다른 3가지 초기농도조건(1000, 5000, 15000 ppm)에서 총 37회의 퇴적실험이 수행되었으며, 퇴적실험 결과로부터 염수조건에서 고령토 퇴적물의 최소전단응력(또는 퇴적한계전단응력; ${\tau}_{bmin}$)과 퇴적률 매개변수들(${\sigma}_1,\;({\tau}^*_b-1)_{50},\;{\sigma}_2,\;t_{50}$)의 정량적 산정 및 초기농도와 염도의 영향에 대한 정성적 분석이 수행되었다. 그 결과, ${\tau}_{bmin},\;{\sigma}_1$ 및 $({\tau}^*_b-1)_{50}$은 각각 0.147, 0.74, $0.65N/m^2$로 산정되었으며, 과거 타 연구결과와의 비교 검토를 통하여 본 실험에서 도출된 결과의 타당성이 입증되었다.

• 한국수자원학회논문집
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• 제32권6호
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• pp.741-749
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• 1999

본 연구에서는 TDR의 반향파의 특성과 총토양전기전도도의 관계를 이용한 비포화 토양에서의 용존오염원 농도를 측정하는 방법을 개발하였다. 본 연구에서 제안한 방법은 두 가지 중요한 관계를 결합한 것으로 첫 번째는 함수량이 일정할 경우 전기전도도와 토양수 농도는 선형관계를 유지한다는 것이며, 두 번째는 천이상태의 용존여염원의 농도를 측정할 수 있게 하기 위해 함수량과 전기전도도의 관계를 설정하는 것이다. 함수량과 전기전도도의 관계를 추정하는 식들이 여러 연구자들에 의하여 제안되었으나, 본 연구에서는 측정의 정확도를 높이기 위하여 한계함수량의 개념을 도입한 새로운 추정식을 제안하였다. 한계함수량 개념을 이용하여 실험자료를 선형, 비선형 구간으로 나누어 분석하였는데, 실험자료의 반영정도를 증가시킬 수 있어 본 연구에서 제안된 식을 이용하여 추정된 전기전도도와 함수량관계는 다른 제안식에 비하여 개선된 결과를 보여 주었다. 본 연구에서 제안된 전기전도도와 함수량관계 추정식을 이용한 천이상태의 오염원 농도 측정법은 함수량이 급하게 변하는 토양에도 적용할 수 있는 매우 유용한 방법으로 판단된다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2012년도 학술발표회
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• pp.1-10
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• 2012

Throughout much of the world, many ecological problems have arisen in watersheds where a significant portion of stream flows are diverted to support agriculture production. Within endorheic watersheds (watersheds whose terminus is a terminal lake) these problems are magnified due to the cumulative effect that reduced stream flows have on the condition of the lake at the stream's terminus. Within an endorheic watershed, any diversion of stream flows will cause an imbalance in the terminal lake's water balance, causing the lake to transition to a new equilibrium level that has a smaller volume and surface area. However, the total mass of Total Dissolved Solids within the lake will continue to grow; resulting in a significant increase in the lake's TDS concentration over time. The ecological consequences of increased TDS concentrations can be as limited as the intermittent disruption of productive fisheries, or as drastic as a complete collapse of a lake's ecosystem. A watershed where increasing TDS concentrations have reached critical levels is the Walker Lake watershed, located on the eastern slope of the central Sierra Nevada range in Nevada, USA. The watershed has an area of 10,400 sq. km, with average annual headwater flows and stream flow diversions of 376 million $m^3/yr$ and 370 million $m^3/yr$, respectively. These diversions have resulted in the volume of Walker Lake decreasing from 11.1 billion m3 in 1882 to less than 2.0 billion $m^3$ at the present time. The resulting rise in TDS concentration has been from 2,560 mg/l in 1882 to nearly 15,000 mg/l at the current time. Changes in water management practices over the last century, as well as climate change, have contributed to this problem in varying degrees. These changes include the construction of reservoirs in the 1920s, the pumpage of shallow groundwater for irrigation in the 1960s and the implementation of high efficiency agricultural practices in the 1980s. This paper will examine the impacts that each of these actions, along with changes in the region's climate, has had on stream flow in the Walker River, and ultimately the TDS concentration in Walker Lake.

• 한국수자원학회논문집
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• 제54권8호
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• pp.607-616
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• 2021

본 연구는 가는 모래로 이루어진 하상으로부터 침식된 부유사의 농도분포 계산결과에 차폐효과가 미치는 영향을 살펴보는 것을 목적으로 수행되었다. 하상재료의 입도분포를 고려하여 침식율을 산정할 수 있는 유사이동 모형을 개발하였으며, 측정자료와의 비교를 통해 수치모형의 적용가능성을 검토하였다. 수치모의결과로부터 하상재료 입도분포의 기하표준편차가 1.5보다 작은 경우 차폐효과가 부유사 농도의 연직방향 분포 계산결과에 미치는 영향은 매우 작은 것으로 나타났다. 또한 기하표준편차가 1.5이하인 가는 모래로 이루어진 하상으로부터 침식된 유사 농도를 계산하는 경우, 균일사로 가정 후 대표입경을 바탕으로 농도를 산정하여도 합리적인 결과가 얻어지는 것으로 확인되었다.

• Journal of Welding and Joining
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• 제34권6호
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• pp.42-46
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• 2016

Hydrogen assisted cracking (HAC) is one of the most complicated problem in welding. Huge amount of studies have been done for decades. Based on them, various standards have been established to avoid HAC. But it is still a chronic problem in industrial field. It is well known that the main causes of the hydrogen crack are residual stress, crack susceptible micro structures and a certain critical level of hydrogen concentration. Even though the exact generating mechanism is unclear till today, it has been reported that the hydrogen level in the weld metal should be managed less than a certain amount to prevent it. Matsuda studied that the residual hydrogen level in the weld metal can be varied even if the initial hydrogen content is same. It is also insisted in this report that the residual hydrogen concentration is in stronger correlation with hydrogen crack than the initial hydrogen content. But, in practical point of view, the residual hydrogen is still hard to consider because measuring hydrogen level is time and cost consuming process. In this regard, numerical analysis is the only solution for considering the residual hydrogen content. Meanwhile, Takahashi showed the possibility of predicting the residual hydrogen by a rigorous FE analysis. But, few commercial software suitable for solving the weld metal hydrogen has been reported yet. In this study, two dimensional thermal - hydrogen coupled analysis was developed by using the commercial FE software MARC. Since the governing equation of the hydrogen diffusion is similar to the heat transfer, it is shown that the heat transfer FE analysis in association with hydrogen diffusion property can be used for hydrogen diffusion analysis. A series of simulation was performed to verify the accuracy of the model. For BOP (Bead-On-Plate) and the multi-pass butt welding simulations, remaining hydrogen contents in the weld metal is well matched with measurements which are referred from Kim and Masamitsu.

• 한국결정성장학회지
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• 제26권3호
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• pp.121-125
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• 2016

The effect of temperature and pressure in the nitrogen ambient furnace on bulk micro defect (BMD) and denuded zone (Dz) is experimentally investigated. It is found that as pressure increases, Dz depth increases with a small decrease of BMD density in the range of temperature, $100{\sim}300^{\circ}C$. BMD density with hot isostatic pressure treatment (HIP) at temperature of $850^{\circ}C$ is higher than that without HIP while Dz depth is lower due to much higher BMD density. As the pressure increases, BMD density is increased and saturated to a critical value, and Dz depth increases even if BMD density is saturated. The concentration of nitrogen increases near the surface with increasing pressure, and the peak of the concentration moves closer to the surface. The nitrogen is gathered near the surface, and does not become in-diffusion to the bulk of the wafer. The silicon nitride layer near the surface prevents to inject the additional nitrogen into the bulk of the wafer across the layer. The nitrogen does not affect the formation of BMD. On the other hand, the oxygen is moved into the bulk of the wafer by increasing pressure. Dz depth from the surface is extended into the bulk because the nuclei of BMD move into the bulk of the wafer.

• Bulletin of the Korean Chemical Society
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• 제7권5호
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• pp.399-402
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• 1986

The critical micelle concentration (CMC) of sodium deoxycholate (NaDC) and the effects of amides on the micellization processes have been studied by fluorometric technique using pyrene as a probe. The addition of amides as cosolvent destabilized the NaDC micelle and increased the CMC. The order of effectiveness for the perturbation of NaDC micelle was N-methylacetamide ${\ge}$ DMF > acetamide > formamide, which is the order of hydrophobicity of the amines. This indicated that the effect of amides on the micellization processes of NaDC arises from diminution of the hydrophobic effect. The electrostatic repulsion between ionic head groups in the NaDC micelle appeared to be much less than that in aliphatic ionic micelle. This was also revealed in the weaker dependence of the CMC on ionic strength. The premicellar association of NaDC was not significantly involved in the micellization processes of the bile salt.