• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.750-754
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• 2003

본 논문에서는 X-선 관전류를 직접 검출하여 제어하는 2.4kW(80kv,30mA)급 최소형, 최경량 휴대용 X-선 발생 장치를 제안한다. 본 장치는 X-선발생을 위한 고전압 발생단에 모노탱크 블록 사용하였고, 고주파 고전압용 인버터에는 스위칭 전력소자로서 MOS-FET를 채용, 70kHz로 스위칭 함으로서 고전압 변압기를 비롯한 고전압 발생부의 크기와 무게를 최소화하였다. 또한, 설정 관전류에 대한 정밀한 제어를 위하여 2단계 모드로 필라멘트 예열을 행하여 관전류 응답특성을 개선하였으며 제안한 휴대용 X-선 발생장치의 부하변동에 따른 X-선 관전압과 관전류의 개선된 특징을 실험파형을 통하여 입증하였다.

• Journal of IKEEE
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• v.25 no.1
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• pp.95-100
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• 2021

If we know the location of the hull block and the welding feeder in the shipyard, we can easily obtain the location information of the worker. That data is very useful for implementing a workplace safety monitoring system. However, it is difficult to apply a fixed communication network to the workplace due to the specificity of the hull structure and welding process. In this study, inductive power line communication, which can replace dedicated communication line, was reviewed. A ferrite core was used as an inductive coupler to be installed on the power cable of the welding machine, and a nano-crystalline core was applied as a coupler to be fastened to the support rod of the metal block. In order to visualize the operating principle of the proposed couplers, 3D modeling and finite element analysis were performed with the COMSOL AC/DC module. In the communication performance test using an aluminum profile, when the communication channel was formed by the contact of the welding electrode, the bandwidth was kept above 6 Mbps.

• Tunnel and Underground Space
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• v.15 no.4 s.57
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• pp.305-315
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• 2005

DDA (Discontinuous Deformation Anlaysis) is one of the latest numerical analysis which has merits of both FEM and DEM. In this research a new edge-to-edge contact algorithm was applied on DDA. With adoption of new edge-to-edge contact state definition, sub-algorithm was improved about open-close iteration, contact state judge, contact detecting, and friction forces acting on joints. Newly applied DDA was verified based on two different cases. The DDA results show good agreement with numerically predicted one.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.152-158
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• 2008

In shallow water environment, the detection performance of an active sonar using matched filter with LFM(linear frequency modulation) pulse can be seriously degraded by reverberation which is considered as non-white noise. To reduce the effect of reverberation, a whitening filter preceding the matched fitter, is usually adopted. In the conventional pre-whitening filter, it is assumed that local stationarity is preserved between detection block and its right ahead block. And then by using the characteristics of the reverberation of preceding block, the reverberation of detection block is estimated and whitened. According to the environment of shallow water, the stationarity of reverberation may be preserved for more blocks. In this case, the reverberation of the detection block can be estimated more accurately if more blocks are used. In this paper, the real reverberation signal which is obtained from shallow sea is analyzed and its proper region of estimation block is examined. And the performance of pre-whitening matched filter is compared and analyzed according to the region of estimation block.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.2C
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• pp.121-128
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• 2003

In this paper, we propose a new disparity estimation method called object based block matching algorithm(OBMA) for stereoscopic images which is able to reduce the blocking artifact. In the proposed algorithm, edge information of the given image is first extracted and then we estimate the disparity of each segmented object to remove the blocking artifact. In the experimental results, it is proven that the proposed algorithm has about the same performance as the old BMA algorithm while it achieves much better subjective quality.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.3
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• pp.57-67
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• 1999

본 논문에서는 영상 부호화시 전처리 과정을 수행함으로써 잡음을 제거하는 새로운 알고리듬을 제안하였다. 제안한 알고리듬은 영상의 선명도를 유지할뿐아니라 전체적인 부호화 효율을 높여준다. 효율향상 과정은 다음과 같다. 첫째 블록 특성에 다라 영역을 분류하며, 둘째로는 Canny 연산자와 Sobel 연산자를 이용하여 경계선 방향을 얻는다. 세 번째로 블록 특성과 경계선 방향에 따라 방향성 형태학적 필터를 구한다. 형태학적 필터링은 영상내 존재하는 잡음을 제거하고, 표준 영상의 경우 인간이 시각적으로 느낄 수 없는 성분을 제거한다. 형태학적 필터링은 경계선 성분을 손실시키는 결과가 발생하지만, 제안한 알고리듬은 손실된 경계선 영역을 복원하는 과정을 거친다. 그러한 과정의 결과로, 전체적인 부호화 효율이 향상된다. 특히, 제안한 알고리듬을 적용한 표준영상의 경우, 약 50-50%의 비트 발생량이 줄어드는 결과를 나타내었다. 잡음 분산값을 달리하여 만든 잡음 영상에 제안한 방법을 적용한 결과, 영상의 선명도를 유지하였다. 제안한 알고리듬은 인간의 시각 특성을 고려한 미세한 잡음 제거 방법에서 우수한 성능을 나타내었으며, 영상의 선명도를 유지하는 것을 보여 주었다.

• The Journal of Korean Society for Radiation Therapy
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• v.31 no.1
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• pp.57-65
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• 2019

Purpose: The purpose is to clarify the effect of additional scattering ratio on the edge of the block according to the increasing block thickness with low melting point lead alloy and pure lead in electron beam therapy. Methods and materials: $10{\times}10cm^2$ Shielding blocks made of low melting point lead alloy and pure lead were fabricated to shield mold frame half of applicator. Block thickness was 3, 5, 10, 15, 20 (mm) for each material. The common irradiation conditions were set at 6 MeV energy, 300 MU / Min dose rate, gantry angle of $0^{\circ}$, and dose of 100 MU. The relative scattering ratio with increasing block thickness was measured with a parallel plate type ion chamber(Exradin P11) and phantom(RW3) by varying the position of the shielding block(cone and on the phantom), the position of the measuring point(surface ans depth of $D_{max}$), and the block material(lead alloy and pure lead). Results : When (depth of measurement / block position / block material) was (surface / applicator / pure lead), the relative value(scattering ratio) was 15.33 nC(+0.33 %), 15.28 nC(0 %), 15.08 nC(-1.31 %), 15.05 nC(-1.51 %), 15.07 nC(-1.37 %) as the block thickness increased in order of 3, 5, 10, 15, 20 (mm) respectively. When it was (surface / applicator / alloy lead), the relative value(scattering ratio) was 15.19 nC(-0.59 %), 15.25 nC(-0.20 %), 15.15 nC(-0.85 %), 14.96 nC(-2.09 %), 15.15 nC(-0.85 %) respectively. When it was (surface / phantom / pure lead), the relative value(scattering ratio) was 15.62 nC(+2.23 %), 15.59 nC(+2.03 %), 15.53 nC(+1.67 %), 15.48 nC(+1.31 %), 15.34 nC(+0.39 %) respectively. When it was (surface / phantom / alloy lead), the relative value(scattering ratio) was 15.56 nC(+1.83 %), 15.55 nC(+1.77 %), 15.51 nC(+1.51 %), 15.42 nC(+0.92 %), 15.39 nC(+0.72 %) respectively. When it was (depth of $D_{max}$ / applicator / pure lead), the relative value(scattering ratio) was 16.70 nC(-10.87 %), 16.84 nC(-10.12 %), 16.72 nC(-10.78 %), 16.88 nC(-9.93 %), 16.90 nC(-9.82 %) respectively. When it was (depth of $D_{max}$ / applicator / alloy lead), the relative value(scattering ratio) was 16.83 nC(-10.19 %), 17.12 nC(-8.64 %), 16.89 nC(-9.87 %), 16.77 nC(-10.51 %), 16.52 nC(-11.85 %) respectively. When it was (depth of $D_{max}$ / phantom / pure lead), the relative value(scattering ratio) was 17.41 nC(-7.10 %), 17.45 nC(-6.88 %), 17.34 nC(-7.47 %), 17.42 nC(-7.04 %), 17.25 nC(-7.95 %) respectively. When it was (depth of $D_{max}$ / phantom / alloy lead), the relative value(scattering ratio) was 17.45 nC(-6.88 %), 17.44 nC(-6.94 %), 17.47 nC(-6.78 %), 17.43 nC(-6.99 %), 17.35 nC(-7.42 %) respectively. Conclusions: When performing electron therapy using a shielding block, the block position should be inserted applicator rather than the patient's body surface. The block thickness should be made to the minimum appropriate shielding thickness of each corresponding using energy. Also it is useful that the treatment should be performed considering the influence of scattering dose varying with distance from the edge of block.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10d
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• pp.454-456
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• 2002

압축 방법에는 크게 손실(lossy)압축과 무손실(lossless)압축으로 나눌 수 있다. 그 중 프랙탈 이미지 압축은 lossy 압축의 한가지 방법으로서 개별적인 화소들에 대한 자료를 저장하기보다는, 영상 생성을 위한 명령이나 방식을 저장하는 방법이다. 특히 이미지의 내에 자기유사성(self-similarity)과 중복성(Redundancy)을 이용하여 관련성을 발견하고 수학적인 공식으로 표현하려는 방식이다. 그러나 이미지를 Domain과 Range로 블록화 한 후 유사한 이미지를 찾아내는 데 걸리는 시간이 상당히 길다. 여기에서는 Domain과 Range의 외곽선의 기울기의 부호를 이용하여 블록을 16가지로 클래스화 하여서, 전체의 Domain 블록을 탐색하는 데 걸리는 시간을 줄이고자 하였다. 전체 탐색을 하는 경우보다 10배 이상의 속도향상을 보였고, 이미지에 따라서는 PSNR 값의 손실도 없음을 보였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.4
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• pp.556-561
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• 2022

In this paper, we present a block media communication (BMC) system which employs powerline communication to the equipments used in the welding process for ship-assembly and uses metal block as a communication medium. Inductive couplers are installed on digital feeder and pin jig. Information signal is added to the current generated by the welding gun, and applied to the block. When the welding operation starts, information generated in the field is transmitted to the monitoring server in real-time. The field test on the BMC system confirms that the transmitted data are correctly received at the server. Since the proposed system can be built without any changes to the existing welding process, it is helpful to increase competitiveness of the shipbuilding industry through smart factory of shipyards. It is also possible to quickly respond to emergency situations that may occur to workers in an electromagnetic wave shielding environment or a closed space, the effect of preventing industrial accidents will be great.

• Journal of Broadcast Engineering
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• v.3 no.2
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• pp.111-117
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• 1998

Due to independent processing of image block, DCT-based block coding algorithms can produce the blocking effect qhich is gray-level discontinuity along block boundaries of the reconstructed image. In this paper, we have proposed two techniques to reduce the blocking effect: two-stage transform coding with variable quantizer and the globally optimum filtering. We have also compared performances of our algorithms and other conventional algorithms by applying optimal allocation.