• Journal of Korean Orthopaedic Sports Medicine
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• v.9 no.1
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• pp.41-47
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• 2010

Purpose: To compare the obliquity of femoral tunnels prepared with transtibial (TT) versus anteromedial portal technique (AM) using x-ray in single-bundle anterior cruciate ligament (ACL) reconstruction. Materials and Methods: Among one-hundred thirty two patients who were undergoing ACL reconstruction from January 2007 to December 2009, thirty patients using TT and twenty patients using AM, those who had single-bundle ACL reconstruction, were evaluated with plain radiographs including anteroposterior, intercondylar notch and lateral view to compare the obliquity of bone tunnels. Results: The mean coronal obliquity of femoral tunnel for TT was $71^{\circ}$ (range; $65^{\circ}{\sim}77^{\circ}$), while for AM was $51^{\circ}$ (range; $39^{\circ}{\sim}60^{\circ}$) and the mean sagittal obliquity of femoral tunnel for TT was $22.7^{\circ}{\pm}7.8$, while for AM was $30.2^{\circ}{\pm}6.9$, their differences between them were statistically significant (P<0.05). However, there were no differences between two techniques on the tibial tunnel obliquity in coronal and sagittal plane. Conclusion: Anterior cruciate ligament reconstruction using AM portal technique allows more horizontally oriented and divergent femoral tunnel compared to that of transtibial technique. This seems to enable the graft placement into the femoral footprint and preserve the posterior cortical wall.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.319-323
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• 2005

연속적인 유량자료의 생산을 위해 일반적으로 단일 곡선 형태의 수위-유량관계가 사용되고 있다. 그러나 홍수수문곡선 상승부와 하강부의 기울기, 조도계수, 하상경사 등 흐름에 영향을 미치는 여러 인자에 의해 수위-유량곡선은 단일 형태가 아니라 복잡한 루프형태로 나타나게 된다. 지금까지 이론적으로는 이와 같은 수위-유량관계의 특성이 알려져 있긴 하였지만 복잡한 특성을 규명하는 것이 곤란하여 구체적으로 분석되지 못한 것이 현실이다. 이와 같은 특성의 분석을 위해서는 하천형상과 더불어 하천 흐름의 동역학적인 분석이 필요하다. 본 연구에서는 댐 직하류 지점의 수위와 유량의 분석을 통하여 실제 발생하고 있는 수위-유량관계의 복잡성을 확인하였고, 수치모형에 의해 복잡한 수위-유량관계를 재현하였다. 분석 결과 모든 지점에서 수위-유량관계가 매우 복잡한 형태로 나타나 일반적으로 사용되는 단일곡선과는 많은 차이가 있는 것으로 나타났다. 또한 수치모형에 의해 이와 같은 복잡한 수위-유량관계가 잘 재현될 수 있음을 증명하였다. 이와 같은 결과는 기존에 사용되고 있는 단일 곡선형 수위 -유량관계가 많은 오차를 포함하고 있음을 나타내며, 적절한 수치모형에 의해 이와 같은 한계를 극복할 수 있는 것을 나타낸다고 할 수 있다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.2
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• pp.50-59
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• 2000

In this paper, a new preprocessing method is proposed to speedup the watershed-based image segmentation In the proposed method, the gradient correction values of ramp edges are calculated from the positions and width of the ramp edges using Laplacian operator, and then, unlike the conventional method in which the monoscale or multi scale gradient image is directly used as a reference iImage, the reference image is obtained by adding the threshold value to each position of the ramp edges in the monoscale gradient image And the marker image is reconstructed on the reference image by erosion By preprocessing the image for the watershed transformation in such a manner, we can reduce the oversegmentations far more than those of applying the conventional morphological filter to the simple monoscale or multiscale gradient-based reference image Thus, we can reduce the total image segmentation time by reducing the time of postprocessing of region merging, which consumes most of the processing time In the watershed-based image segmentation, Experimental results indicate that the proposed method can speedup the total image segmentation about twice than those of the conventional methods, without the loss of ramp edges and principal edges around the dense-edge region.

• Korean Journal of Optics and Photonics
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• v.34 no.1
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• pp.22-30
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• 2023

The use of segmented mirrors is one of the ways to make the primary mirror of a spaceborne satellite larger, where several small mirrors are combined into a large monolithic mirror. To align multiple segmented mirrors as one large mirror, there must be no discontinuity in the x, y-axis (tilt) and axial alignment error (piston) between adjacent mirrors. When the tilt and piston are removed, we can collect the light in one direction and get an expected clear image. Therefore, we need a precise wavefront sensor that can measure the alignment error of the segmented mirrors in nm scale. The tilt error can be easily detected by the point spread image of the segmented mirrors, while the piston error is hard to detect because of the absence of apparent features, but makes a downgraded image. In this paper we used an optical testing interferometer such as a Fizeau interferometer, which has various advantages when aligning the segmented mirror on the ground, and focused on measuring the axial displacement error of a segmented mirror as the basic research of measuring the piston errors between adjacent mirrors. First, we calculated the relationship between the axial displacement error of the segmented mirror and the surface defocus error of the interferometer and verified the calculated formula through experiments. Using the experimental results, we analyzed the measurement uncertainty and obtained the limitation of the Fizeau interferometer in detecting axial displacement errors.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.1
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• pp.60-68
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• 2010

In case of sensorineural hearing loss, auditory perception can be activated by electrical stimulation of the nervous system via electrode implanted into the cochlea or auditory nerve. Since the tonotopic map of the human auditory nerve has not been definitively identified, the recording of auditory nerve signal with microelectrode is desirable for determining the tonotopic map. This paper proposes the multi-channel analog front-end for auditory nerve signal detection. A channel of the proposed analog front-end consists of an AC coupling circuit, a low-power 4th-order Gm-C LPF, and a single-slope ADC. The AC coupling circuit transfers only AC signal while it blocks DC signal level. Considering the bandwidth of the auditory signal, the Gm-C LPF is designed with OTAs adopting floating-gate technique. For the channel-parallel ADC structure, the single-slope ADC is used because it occupies the small silicon area. Experimental results shows that the AC coupling circuit and LPF have the bandwidth of 100 Hz - 6.95 kHz and the ADC has the effective resolution of 7.7 bits. The power consumption per a channel is $12\;{\mu}W$, the power supply is 3.0 V, and the core area is $2.6\;mm\;{\times}\;3.7\;mm$. The proposed analog front-end was fabricated in a 1-poly 4-metal $0.35-{\mu}m$ CMOS process.

• Journal of the Korea Society of Computer and Information
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• v.14 no.7
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• pp.41-47
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• 2009

A solution to the problems of recognizing as one spot or detection failures for complex regions, in which many spots representing proteins are overlapped and saturated, is suggested. The accumulated gradients of each point in complex regions are calculated, and the resulting accumulated gradient image segmented using watershed technique. The suggested solution show better and efficient result than existing method for spot separation, detects more protein spots hidden in the image of 2-dimensional electrophoresis, and expands the scope of prediction.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.326-327
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• 2000

May(1945)에 의하여 임팩터가 개발된 이후 임팩터의 단별 분리입경의 정확성을 증가시키고, 기판에서 입자의 채취량을 늘리며, 임팩터 내부의 입자손실과 기판에서 입자가 충돌하여 튀어나오는 것(bounce)을 줄일 수 있는 방법 등이 꾸준히 연구되고 있다. 가속 노즐의 형상을 사각형에서 원형으로 변경하여 분리효율곡선의 기울기(stiffness)를 증가시킬 수 있었고(Mitchell and Filcher, 1959), 임팩터의 한 단에 여러 개의 가속 노즐을 가공한 다중 노즐(multi-jet) 임팩터를 사용함으로써 단의 분리입경을 낮추고, 입자의 채취량을 늘릴 수 있게 되었다(Anderson, 1958). (중략)

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.51.2-52
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• 2021

Pulsar Wind Nebula(PWN)는 radio부터 TeV band까지 넓은 파장에 걸쳐 복사를 하며 이 복사는 Spectral Energy Distribution(SED)으로 측정된다. 관측된 SED는 두 개의 주요한 bump를 보이는데 low-energy emission bump는 synchrotron radiation에 의해 만들어지고 high-energy emission bump는 inverse Compton scattering에 의해 만들어진다. 대부분 PWN들의 SED는 단일 전자 분포로 설명이 가능하지만 최근 연구 결과에 의하면 Crab nebula, G21.5-0.9 같은 일부 young pulsar wind nebula의 X-ray SED에서 단차나 기울기의 변화 등 단일 전자 분포로 설명하기 어려운 부분이 관측되기도 한다. 이런 PWN에 대하여 우리는 이중 전자 분포를 이용해서 broadband SED가 잘 설명이 되는지 확인하고 이를 통하여 PWN 입자 가속의 특성을 이해해보고자 한다.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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• pp.145-152
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• 2000

X-ray diffraction method detects change of crystal lattice distance under material surface using diffraction angle 2$\theta$. This technique can be applied to the behavior on slip band and micro crack due to material degradation. The relation between half-value breadth and number of cycle has three stages which constitute rapid decrease in initial number of cycles, slight decrease in middle number of cycles and rapid decrease in final number of cycles. The ratio of half-value breadth takes a constant value on B/B$_{0}$-N diagram with loading condition except early part of fatigue life. The ratio of half-value breadth B/B$_{0}$ with respect to number of cycle to failure N$_{f}$ has linear behavior on B/B$_{0}$-log N$_{f}$ diagram. Therefore, in this paper the estimation of fatigue life by average gradient method has much less estimated mean error than the estimation of fatigue life by log B/B$_{0}$-log N/N$_{f}$ relation.elation.ation.

• Korean Journal of Optics and Photonics
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• v.31 no.1
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• pp.7-12
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• 2020

In this paper, we experimentally investigate the fiber fuse in single-mode 2-kW-class high-power fiber amplifiers, depending on the cooling method at the splicing point. We measured the temperature of the splicing point between the pump-signal combiner and gain fiber as a function of laser output power. The temperature of the splicing point increased from 20 to 32℃ with a slope of 0.01℃/W, up to 1.2 kW of laser output power. At higher powers the temperature of the splicing point increased dramatically, with a slope of 0.08℃/W. After that, the fiber amplifier was destroyed during operation at 1.96 kW of output power by fiber fuse. The bullet shape, a common feature of fiber fuse, was observed in the damaged passive fiber core of the pump-signal combiner. Later, we adopted an improved water-cooled cold plate to increase the cooling efficiency at the splicing point, and investigated the laser output power. The temperature at the splicing point was 35.8℃ with a temperature-rise slope of 0.007℃/W at the maximum output power of 2.05 kW. The beam quality M² was measured to be less than 1.3, and the output beam's profile was a stable Gaussian shape. Finally, neither fiber fuse nor mode instability was observed in the fiber amplifier at the maximum output power of 2.05 kW.