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이정우,Ick-Hyun Jo,김장욱,홍치은,Kyong Hwan Bang,박영두 한국원예학회 2019 Horticulture, Environment, and Biotechnology Vol.60 No.5
Ginseng ( Panax ginseng ) has a low genetic diversity and a narrow pool of genetic resources. Mutagenesis is one of the mostpowerful methods for inducing genetic variation in this species, but little research has been performed in ginseng. In thisstudy, various tissues, including dehiscent seeds, 1-year-old roots, and somatic embryos were irradiated at diff erent dosesof gamma rays (20–400 Gy and zero dose as a control) to determine the most optimal concentration and tissues for the successfuluse of mutagenesis in ginseng breeding. The results revealed that high gamma doses (> 100 Gy) were detrimentalto all irradiated tissues. A gradual and signifi cant reduction in germination, emergence, and seedling growth were found asgamma irradiation dose increased. The reduction in survival rates and seedling growth by irradiation at serial doses showedthat the LD 50 of ginseng was 20–80 Gy, although the irradiation doses were tissue dependent. Based on our results, theoptimal doses of gamma rays for inducing mutation in ginseng are < 20, 40, and 60–80 Gy for 1-year-old roots, dehiscentseeds, and somatic embryos, respectively. Given the fact that ginseng somatic embryos are less sensitive to gamma rays thanother tissues, the combination of in vitro culture and mutagenesis could be more eff ective than the conventional methodfor mutation breeding in ginseng. These results provide a good basis for radiation sensitivity of ginseng and are useful as aguideline for ginseng mutation breeding.
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이정우,이정윤 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.1
This paper proposes a transfer matrix method for the bending vibration of two types of tapered beams subjected to axial force, and it is applied to analyze tapered beams with an edge or multiple edge open cracks. One beam type is assumed to be reduced linearly in the cross-section height along the beam length. The other type is a tapered beam in which the cross-section height and width with the same taper ratio is linearly reduced simultaneously. Each crack is modeled as two sub-elements connected by a rotational spring, and the method can evaluate the effect of cracking on the desired number of eigenfrequencies using a minimum number of subdivisions. Among the power series available for the solutions, the roots of the differential equation are computed using the Frobenius method. The computed results confirm the accuracy of the method and are compared with previously reported results. The effectiveness of the proposed methods is demonstrated by examining specific examples, and the effects of cracking and axial loading are carefully examined by a comparison of the single and double tapered beam results.
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