• 대한기계학회논문집A
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• 제23권7호
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• pp.1120-1128
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• 1999

An elastic-viscoplastic finite element analysis is performed to investigate detailed growth behavior of creep cracks and the numerical results are compared with experimental results. In Cr-Mo steel stress fields obtained from the crack growth method by mesh translation were compared with both cases that the secondary creep rate is only used as creep material property and the primary creep rate is included. Analytical stress fields, Riedel-Rice(RR) field, Hart-Hui-Riedel(HR) field and Prime(named in here) field, and the results obtained by numerical method were evaluated in details. Time vs. stress at crack tip was showed and crack tip stress fields were plotted. These results were compared with analytical stress fields. There is no difference of stress distribution at remote region between the case of 1st creep rate+2nd creep rate and the case of 2nd creep rate only. In case of slow velocity of crack growth, the effect of 1st creep rate is larger than the one of fast crack growth rate. Stress fields at crack tip region we, in order, Prime field, HR field and RR field from crack tip.

• 한국작물학회지
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• 제51권1호
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• pp.48-52
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• 2006

Naturally occurring soybean isoflavones are known to be influenced by various genetic and environmental conditions. Growth, yield, and isoflavone content were determined in four different cultivars of soybean grown under drained paddy and upland fields. Most of growth characteristics and yield components of four different soybean cultivars harvested in drained paddy field were greater than those in upland field, regardless of cultivar. By means of high performance liquid chromatography, total daidzein and genistein contents of soybean in drained paddy field were increased up to 40 and 35%, respectively, compared with those in drained paddy field. Besides isoflavone contents, the growth and yield of soybean were significantly affected by cultivar and field conditions, indicating the necessity of genetic program for soybean cultivars appropriate to drained paddy field conditions. In conclusion, converting paddy field into upland may effectively improve soybean cropping system, especially in terms of isoflavone increment under paddy field conditions.

• 한국작물학회지
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• 제48권2호
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• pp.81-88
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• 2003

Soybeans [Glycine max (L.) Merr.] are frequently exposed to unfavorable environments during growing seasons and water is the most important factor limiting for the production system. The purpose of this study was to determine the leaf water potential changes by irrigation, and to evaluate the relationships of leaf water potential, growth and yield in soybeans. Three soybean cultivars, Hwangkeumkong, Shinpaldalkong 2, and Pungsannamulkong, were planted in growth chamber and field with irrigated treatments. Leaf water potential of three soybean cultivars was positively correlated with leaf water content during vegetative and reproductive growth stages in growth chamber and field experiments. Leaf water potentials measured for three soybean cultivars under growth chamber were higher than those of under field conditions. Higher leaf water potential with irrigated plots under field was observed compared to conventional plots during reproductive growth stages. Leaf water potentials of three soybean cultivars were continually decreased during reproductive growth stages under field and there was no significant difference among them. Number of leaves, leaf water content, pod dry weight, number of seeds and seed dry weight with irrigated plots were higher than those of conventional plots. The results of this study suggested that leaf water potential could be used as an important growth indicator during the growing season of soybean plants.

• 한국결정성장학회지
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• 제19권5호
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• pp.215-222
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• 2009

Many concepts of external magnetic field applications in crystal growth processes have been developed to control melt convection, impurity content and growing interface shape. Especially, travelling magnetic fields (TMF) are of certain advantages. However, strong shielding effects appear when the TMF coils are placed outside the growth vessel. To achieve a solution of industrial relevance within the framework of the $KRISTMAG^{(R)}$ project inner heater-magnet modules(HMM) for simultaneous generation of temperature and magnetic field have been developed. At the same time, as the temperature is controlled as usual, e.g. by DC, the characteristics of the magnetic field can be adjusted via frequency, phase shift of the alternating current (AC) and by changing the amplitude via the AC/DC ratio. Global modelling and dummy measurements were used to optimize and validate the HMM configuration and process parameters. GaAs and Ge single crystals with improved parameters were grown in HMM-equipped industrial liquid encapsulated Czochralski (LEC) puller and commercial vertical gradient freeze (VGF) furnace, respectively. The vapour pressure controlled Czochralski (VCz) variant without boric oxide encapsulation was used to study the movement of floating particles by the TMF-driven vortices.

• 한국정보통신학회논문지
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• 제17권1호
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• pp.242-247
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• 2013

심각한 기후변화로 인한 농업의 생산성 약화에 대비하기 위해 식물 성장을 촉진할 수 있는 방안에 대한 연구가 요구되고 있다. 식물성장을 촉진하는 방법으로 자기장을 이용하는 방법이 소개되고 있지만, 식물에 자기장을 인가하는 효과적인 방법에 대해서는 아직까지 자세히 연구된 문헌이 없다. 본 논문에서는 인가하는 정적 자기장의 세기, 자기장의 인가 방향, 자기장 노출 시간 변화에 따른 무순(radish sprouts)의 성장과 초기발아 효과에 대해 실험을 하고. 효과적인 자기장 노출 방법에 대해 조사하였다. 실험의 결과를 종합하면 자기장에 노출되지 않은 무순 보다 자기장에 노출된 무순의 초기발아가 약 3~4일정도 빠른 것으로 나타났고, 효율적인 무순의 성장을 위해서는 자기장의 세기를 적절히 선택해야 함을 알 수 있었고, 자기장의 인가 방향에 따라서는 큰 영향을 받지 않는 것을 알 수 있었다.

• 한국정밀공학회지
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• 제20권11호
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• pp.142-149
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• 2003

Domain switching effect on crack growth in ferroelectric ceramics under combined electric and mechanical loading is investigated. The shape and size of the switching zone is shown to depend strongly on the relative magnitude between the applied electric field and stress field as well as on the ratio of the coercive electric field to the yield electric field. The toughening mechanism is thought to be ferroelectric domain switching leading to the development of a process zone around the crack. Crack-tip stress intensity factor induced by domain switching for the steady state crack growth is numerically obtained.

• 대한기계학회논문집B
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• 제23권3호
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• pp.388-397
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• 1999

Numerical simulations are carried out for the magnetic Czochralski single crystal growth system. It Is shown that a magnetic field significantly suppresses the convective flow and as the strength of magnetic field becomes to be stronger, the heat transfer in the melt is dominated by conduction rather than convection. By imposing a cusp magnetic field, the growth interface shape becomes convex toward the melt. When the axial magnetic field is imposed, there occurs an inversion of the interface shape with increase of the magnetic field strength. The oxygen concentration near the interface decreases with increasing cusp magnetic field strength while axial field causes an increase of an oxygen concentration at the central region and decrease of that at the edge of the crystal. The results show that the cusp magnetic field has advantages over an axial magnetic field In the radial uniformity of oxygen as well as in the additional degree of control.

• 한국유기농업학회지
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• 제12권4호
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• pp.437-450
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• 2004

This study was conducted with two objectives ; one was to select the suitable soybean cultivars for cultivation in paddy field and the other was to establish the environment-friendly rotational cropping system of soybean instead of rice in paddy field. In order to evaluate growth adaptation and yields, Eve soybean cultivars were cultivated in Yeoncheon, Keonggi province, with two cultivation methods such as level row and high ridge. Growth of the top plants, such as stem length, number of branches, diameter of stem, were higher in high ridge than in level row, however, the differences among the cultivars were bigger than those between the cultivation methods. Dry weight of top plant was significantly different among the cultivars during whole growth stages, however, it was higher in level row than in high ridge at V5 stage while it became higher in high ridge as growth progressed. Roots were more developed in high ridge than in level row during whole growth stages. T/R ratio in level row was higher than that in high ridge. During whole growth stages, significant differences were observed among the cultivars in growth and yields in each cultivation method and yields of Eunhakong was the highest. In results, number of nodules and T/R ratio at V5 stage, number of pods at R2 stage, and number of seeds and T/R ratio at R5 stage had highly correlated with yields, respectively.

• 대한기계학회논문집A
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• 제20권4호
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• pp.1177-1185
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• 1996

The crack growth under creep condition is one of the major damage mechanisms which determines remaining life of the component operating at high temperatures. In this paper, the creep crack growth by grain boundary cavitation is studied, which is frequently observed failure mechanism for creep brittle materials. As a result of diffusive growth of creep cavities, it is shown that the crack-tip stress field is modified from the original stress distribution by the amount of singularity attenuation parameter which is function of crack growth rate and material properties. Also, the stress relaxation at crack-tip results in the extension of cavitating area by the load dump effect to meet the macroscopic force equilibrium conditdion.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 춘계학술대회
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• pp.375-377
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• 2012

1930년 초에 자기장과 식물의 성장률이 관계가 있음이 보고된바 있다. 이것은 자기장이 세포의 활성화를 촉진시키기 때문인 것으로 알려져 있다. 그러나 아직 식물의 성장에 자기장의 세기가 미치는 영향에 대한 연구가 미흡하다. 이에 본 연구에서는 무순(radish sprouts)을 이용하여 자기장이 무순(radish sprouts)의 성장에 미치는 영향력을 관찰하였다. 인가하는 자기장의 세기가 20, 40, 60mT 일 때 무순의 성장 변화를 측정하였고, 60mT 일 때 가장 빠르게 성장하는 것을 확인하였다.