• Journal of the Korean Society for Precision Engineering
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• v.21 no.8
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• pp.14-18
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• 2004

우리나라의 공작기계 산업은 IMF 이후 높은 성장을 보이고 있다. 뿐만 아니라 조립공정에서의 정밀 측정기술 또한 많은 발전을 거듭해오고 있다. 또한 최근에는 정밀 측정기와 측정기술의 수출향상으로 괄목할 만한 성장을 보이고 있고, 신기술개발과 연구활동이 활발히 진행되고 있다.(중략)

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.94-100
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• 1998

Microstep characteristics largely depends on the variation of friction force induced by the geometric accuracy of ballscrew, guide rail and the control characteristics of servo unit. In this paper, for improving the microstep characteristics of hydrostatic table with ballscrew, microstep resolution according to the control mode of servo amplifier and response characteristic by the variation of integral gain are tested and compared. Relationship between micro motion behavior of hydrostatic table and the output torque is also tested for acquiring the effective variables on control characteristics. From the results. it is confirmed that the torque control mode has a advantage in microstep resolution, and more stable than velocity control mode in low feed rate, and by the increase of integral gain in the elastic motion realm, response characteristics can be improved.

• Journal of the Korean Society of Radiology
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• v.10 no.3
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• pp.215-222
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• 2016

X-ray mammography is the most effective method for the diagnosis of calcified lesions of various breast diseases. To reduce patient dose and to obtain optimal image required for diagnosis, the performance of the mammography system should be maintained continuously. Because the target (anode) angle of the X-ray tube is measured from the central X-ray, the effective angle can be slightly different in view of the position on the detector, which can result in degrading spatial resolution of the imaging within the field of view. In this study, we measured the MTF to examine spatial resolution for positions on the detector in the digital mammography system. For a tungsten wire of $50{\mu}m$ diameter, the highest spatial frequency was obtained. It meant that a wire diameter for measuring MTF through LSF should be small compared to the pixel size of the detector used in the mammography system. The spatial resolution showed slightly different performance according to positions on the detector. The center position gave the best spatial resolution and positions away from the center showed the degraded performance although the difference of the spatial resolution was small. The effective focal spot size of the full width at half maximum also showed similar result. It concluded that the slightly increase of the effective focal spot size gave the degradation of the spatial resolution for positions on the detector.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.4
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• pp.314-321
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• 1992

To study the seasonal variation of heterotrophic bacteria on the blades of Porphyra species, samples were collected In the intertidal zone near Mokp'o of the Yellow Sea from February to December, 1990 Annual distribution of heterotrophic bacteria on the blades of Porphyra species ranged from $6.9\times10^2\;to\;1.04\times10^5\;cfu/cm^2$ at site 1, and from $9.4\times10^3\;to\;2.93\times10^5\;cfu/cm^2$ at site 2. Average sixty-five percent of isolates from the blades of Porphyra species were rods and $52.1-82.7\%$ of isolates were Gram-negative. Most isolates showed starch hydrolysis$(68\%)$ on March, but showed Poor utilization of carbon sources and no $H_2S$ production. Dominant genus isolated from the baldes of Porphyra species were Alcaligenes spp., Moraxella spp., on March and Micrococcus spp., Moraxella spp., Corynebacterium spp., on November.