• Title/Summary/Keyword: 수학적 모형

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The effect of the revolution and forwarding speed of the rotary blade on the tilling power requirement (로우터리 경운(耕耘)날의 회전속도(回轉速度) 및 작업속도(作業速度)가 경운소요동력(耕耘所要動力)에 미치는 영향(影響))

  • Kwon, Soon Goo;Kim, Soung Rai
    • Korean Journal of Agricultural Science
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    • v.11 no.1
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    • pp.160-175
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    • 1984
  • This study was carried out to analyze the effects of the revolution and forwarding speed of the rotary blade and the edge curves which were $30^{\circ}$ and $40^{\circ}$, on the power requirement of rotary tillage. In this study, the revolutions of the rotary blade considered were 204, 243, 285, 360 rpm, and the forwarding speeds of the rotary system considered were 29.40cm/sec, 46.93em/sec. The power requirements of rotary blade were measured by a dynamic strain gage systems at the soil bin which was filled with artificial soil. The results of the study were summarized as follows: 1. The response surface analysis showed that the revolution and forwarding speed of the rotary shaft had an interacting influence on the torque requirement of the rotary blade. The mathematical model developed by the above was repersented as follow. $$T=a_0+a_1V+a_2R +a_3VR+a_4VR^2$$ where, $a_0=constant$ $a_1,\;a_2,\;a_3,\;a_4=coefficients$ V=forwarding speed of the rotary system. (em/sec) R=revolution of the rotary shaft. (rpm) T=tilling torque requirement. (kg-m) 2. When the maximum tilling torque requirement was analyzed, ${\partial}T/{\partial}R$ was decreased with the increasing revolution of rotary shaft, while ${\partial}T/{\partial}V$ was increased, which was minimum at 200~220 rpm. When the forwarding speeds were increased, ${\partial}T/{\partial}R$ was decreased with increasing rate. 3. When the mean tilling torque requirement was analyzed, ${\partial}T/{\partial}V$ was constant at 320~360 rpm and ${\partial}T/{\partial}R$ was decreased with increasing rate along with the increasing revolution of rotary shaft. 4. When the mean tilling torgue requirement per unit volume of soil was analyzed, ${\partial}T/{\partial}V$ was minimum at 270~300 rpm. ${\partial}T/{\partial}R$ for the forwarding speeds of 29.40cm/sec and 46.93cm/sec was same as that for 280~290 rpm. 5. Increasing the edge curves of the rotary blades, the tilling torque requirement was increased. But other studies showed that the smaller the edge curve, the more straw could be wrapped on blades which resulted in increasing torque requirements. Therefore, the edge curve of rotary blade should be considered for the future study.

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Scientific Practices Manifested in Science Textbooks: Middle School Science and High School Integrated Science Textbooks for the 2015 Science Curriculum (과학 교과서에 제시된 과학실천의 빈도와 수준 -2015 개정 교육과정에 따른 중학교 과학 및 통합과학-)

  • Kang, Nam-Hwa;Lee, Hye Rim;Lee, Sangmin
    • Journal of The Korean Association For Science Education
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    • v.42 no.4
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    • pp.417-428
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    • 2022
  • This study analyzed the frequency and level of scientific practices presented in secondary science textbooks. A total of 1,378 student activities presented in 14 middle school science textbooks and 5 high school integrated science textbooks were analyzed, using the definition and level of scientific practice suggested in the NGSS. Findings show that most student activities focus on three practices. Compared to the textbooks for the previous science curriculum, the practice of 'obtaining, evaluating, and communicating information' was more emphasized, reflecting societal changes due to ICT development. However, the practice of 'asking a question', which can be an important element of student-led science learning, was still rarely found in textbooks, and 'developing and using models', 'using math and computational thinking' and 'arguing based on evidence' were not addressed much. The practices were mostly elementary school level except for the practice of 'constructing explanations'. Such repeated exposures to a few and low level of practices mean that many future citizens would be led to a naïve understanding of science. The findings imply that it is necessary to emphasize various practices tailored to the level of students. In the upcoming revision of the science curriculum, it is necessary to provide the definition of practices that are not currently specified and the expected level of each practice so that the curriculum can provide sufficient guidance for textbook writing. These efforts should be supported by benchmarking of overseas science curriculum and research that explore students' ability and teachers' understanding of scientific practices.

Correlation Between the Parameters of Radiosensitivity in Human Cancer Cell Lines (인체 암세포주에서 방사선감수성의 지표간의 상호관계)

  • Park, Woo-Yoon;Kim, Won-Dong;Min, Kyung-Soo
    • Radiation Oncology Journal
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    • v.16 no.2
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    • pp.99-106
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    • 1998
  • Purpose : We conducted clonogenic assay using human cancer cell lines (MKN-45, PC-14, Y-79, HeLa) to investigate a correlation between the parameters of radiosensitivity. Materials and Methods : Human cancer cell lines were irradiated with single doses of 1, 2, 3, 5, 7 and 10Gy for the study of radiosensitivity and subrethal damage repair capacity was assessed with two fractions of 5Gy separated with a time interval of 0, 1, 2, 3, 4, 6 and 24 hours. Surviving fraction was assessed with clonogenic assay using $Sperman-H\"{a}rbor$ method and mathematical analysis of survival curves was done with linear-quadratic (LQ) , multitarget-single hit(MS) model and mean inactivation dose$(\v{D})$. Results : Surviving fractions at 2Gy(SF2) were variable among the cell lines, ranged from 0.174 to 0.85 The SF2 of Y-79 was lowest and that of PC-14 was highest(p<0.05, t-test). LQ model analysis showed that the values of $\alpha$ for Y-79, MKN-45, HeLa and PC-14 were 0.603, 0.356, 0.275 and 0.102 respectively, and those of $\beta$ were 0.005, 0.016, 0.025 and 0.027 respectively. Fitting to MS model showed that the values of Do for Y-79. MKN-45, HeLa and PC-14 were 1.59. 1.84. 1.88 and 2.52 respectively, and those of n were 0.97, 1.46, 1.52 and 1 69 respectively. The $\v{D}s$ calculated by Gauss-Laguerre method were 1.62, 2.37, 2,01 and 3.95 respectively So the SF2 was significantly correlated with $\alpha$, Do and $\v{D}$. Their Pearson correlation coefficiencics were -0.953 and 0,993. 0.999 respectively(p<0.05). Sublethal damage repair was saturated around 4 hours and recovery ratios (RR) at plateau phase ranged from 2 to 3.79. But RR was not correlated with SF2, ${\alpha}$, ${\beta}$, Do, $\v{D}$. Conclusion : The intrinsic radiosensitivity was very different among the tested human cell lines. Y-79 was the most sensitive and PC-l4 was the least sensitive. SF2 was well correlated with ${\alpha}$, Do, and $\v{D}$. RR was high for MKN-45 and HeLa but had nothing to do with radiosensitivity parameters. These basic parameters can be used as baseline data for various in vitro radiobiological experiments.

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The Design of Wireless Underwater Telephone -Analysis of Underwater Background Noise for Wireless Underwater Telephone Design - (수중 무선 전화기의 설계 - 수중무선전화기 설계를 위한 수중소음분석을 중심으로-)

  • 박문갑;윤갑동;김석제;윤종락
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.37 no.4
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    • pp.302-307
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    • 2001
  • The underwater background noise measured in Geoje and Tongyoung diving fishing ground from May to December, 2000 and analyzed to get optimum carrier frequency and transmitter power level for underwater wireless telephone design. The results obtained are summarized as follows: 1. At the Geoje and Tongyoung diving fishing ground, the lowest ambient noise band was 25~30kHz with 57dB and 52dB re 1$\mu$Pa, respectively. 2. At the Geoje and Tongyoung diving fishing ground, the lowest noise band during fishing activity was 67dB and 62dB re 1$\mu$Pa, respectively. 3. At the Geoje diving fishing ground, the noise of water jetter which is a digging machine for subbottom shells was 102dB re 1$\mu$Pa. 4. Considering the design parameters of underwater wireless telephone, it is found that the optimum carrier frequency band is around 30kHz and the transmitter source level should be at least 131dB re 1$\mu$Pa for 500m range telephone.

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