• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.769-772
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• 2014

비정질 InGaZnO 박막트랜지스터의 Gate Overlap 길이에 따른 NBS(Negative Bias Stress) 및 hot carrier 스트레스 후 시간별 문턱전압의 변화에 의한 소자신뢰도를 분석하였다. 측정에 사용된 소자는 비정질 InGaZnO TFT이며 채널 폭 $W=104{\mu}m$, 게이트 길이 $L=10{\mu}m$이며 Gate Overlap 길이는 $0,1,2,3{\mu}m$를 사용하였다. 소자 신뢰도는 전류-전압을 측정하여 분석하였다. 측정 결과, hot carrier 스트레스 후 Gate Overlap 길이가 증가할수록 문턱전압의 변화가 증가하였다. 또한, NBS 후에는 Gate Overlap 길이가 증가할수록 문턱전압의 변화가 감소하였고 장시간 스트레스 후에 hump가 발생하였다.

• 전자공학회논문지B
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• 제32B권10호
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• pp.1280-1285
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• 1995

In this paper the optimized overlap driving scheme for improving the reduction problem of the operating voltage range occured by the overlap driving scheme proposed precedently and increasing the contrast ratio of screen image in the simple matrix LCDs is proposed. The characteristic estimation of the proposed method was performed in a condition that the number of scan electrodes was 120 and the threshold voltage of LC pixel was 2V and the overlap rate of scan signal was varied from 0% to 40% . As a result of estimation compared with the overlap driving scheme proposed precedently, this new method was certified as a method which it could increase the operating voltage range of the LC pixel by 16% in 20% overlap condition and it's operating voltage range was also increased very much with the increase of the overlap rate. Consequently this newly proposed method was certified as a method which it could maintain the improvement effect of the operating characteristics obtained by the overlap driving scheme proposed precedently with the big improvement in the contrast ratio of screen image.

• 한국인터넷방송통신학회논문지
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• 제12권3호
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• pp.29-35
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• 2012

본 논문에서는 MPEG(Moving Picture Experts Group) 영상 디코더에서 영상을 압축, 비교, 복원, 저장한후 디코딩 처리하는 방법을 종래의 픽셀 단위로 처리하는 방법과는 다르게 영상의 단위 화소 주변을 군집화소로 분류한 후 이를 클러스터링하여 오버랩정도를 결정 한다. 오버랩 정도의 임계치값을 결정하는데는 패턴식별을 취한후 샘플 패턴에 대한 기하구조의 파악과 결정함수의 도출로 활용된다. 특징공간이 4차원 이상이면 주어진 패턴 구조를 시각적으로 관찰할 수 없다. 이 때, 분포구조를 고찰해 볼수 있는 방법은 군집중심간의 거리, 군집별 패턴의 수 및 표준편차 등을 이용하는 방법이다. 임계치 값을 넘는 중복화면은 소거되고 넘지않는 군집화면은 패턴인식으로 복원된후 동영상으로 구현된다. 이방법이 기존의 픽셀 단위 처리하는 방법 과는 20%정도의 메모리 감축과 15%정도의 화면 복원에 성능이 향상된 것으로 판정된다.

• Journal of the Optical Society of Korea
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• 제18권6호
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• pp.650-656
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• 2014

We propose a novel active fiber design for selectively generating cylindrical vector beams (CVBs) or cylindrical vector modes (CVMs) which can be applied to conventional fiber lasers. A fiber is designed to have a ring-shaped core refractive index profile which can lead to the best overlap between the active dopant distribution profile and the lowest-order CVM (LCVM) field profile. Therefore, the overlap factor (OVF) of the LCVM becomes even higher than that of the fundamental mode. We emphasize that this condition cannot be satisfied by a conventional step-index core fiber (SICF) but by the ring-doped core fiber (RDCF). Because the lasing threshold is inversely proportional to the OVF, the LCVM can predominantly be stimulated even without going through special procedures to impose extra loss mechanisms to the fundamental mode. We numerically verify that the OVF of the LCVM with the doped ions can significantly exceed that of the fundamental mode if the proposed fiber design is applied. In addition, an RDCF of the proposed fiber design can also operate in a regime containing no higher-order modes besides the LCVM, so that it can selectively and efficiently generate the LCVM without being disrupted by the parasitic lasing of the higher-order modes. We highlight that an optimized RDCF can lead to a >30 % higher OVF ratio than a SICF having the same doped area. The proposed model is expected to be useful for enhancing the efficiency of generating CVBs in an all-fiber format.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제27권2호
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• pp.146-159
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• 2023

This paper proposes a hybrid algorithm combining K-means clustering and watershed algorithms for flower segmentation and counting. We use the K-means clustering algorithm to obtain the main colors in a complex background according to the cluster centers and then take a color space transformation to extract pixel values for the hue, saturation, and value of flower color. Next, we apply the threshold segmentation technique to segment flowers precisely and obtain the binary image of flowers. Based on this, we take the Euclidean distance transformation to obtain the distance map and apply it to find the local maxima of the connected components. Afterward, the proposed algorithm adaptively determines a minimum distance between each peak and apply it to label connected components using the watershed segmentation with eight-connectivity. On a dataset of 30 images, the test results reveal that the proposed method is more efficient and precise for the counting of overlapped flowers ignoring the degree of overlap, number of overlap, and relatively irregular shape.

• 한국레이저가공학회지
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• 제2권3호
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• pp.52-61
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• 1999

The laser induced forward transfer(LIFT) technique employs a pulsed laser to transfer parts of a thin metal film from an optically transparent target onto an arbitrary substrate in close proximity to the metal film on the target. In this work, a two-step method, the combination of LIFT process, in which a Au film deposited on the $Al_2$O$_3$ substrate by Nd:YAG laser and subsequent Au electroless metal plating on the by LIFT process generated Au seed, was presented. The influence of laser parameters, wavelength, laser power, film thickness and overlap ratio of pulse tracks, on the shapes of deposit and conductor line after electroless plating is experimentally studied. As a results, the threshold power densities for ablation, deposition and metallization were determined and comparison of threshold value between the wave length 1064nm and the second harmonic generated 532nm. In odor to determine a possible application in the electronic industry, a smallest conduct spot size, line width and isolated line space were generated.

• 대한전자공학회논문지SP
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• 제39권3호
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• pp.42-48
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• 2002

다중 채널을 위한 다중 기술 부호화는 복호기가 채널의 일부분의 정보만 수신함으로서 유용한 영상 복원을 할 수 있다. 본 논문에서는 새롭게 설계된 EZW 부호기를 이용하여 효율적인 다중 기술 부호기를 제안한다. 먼저 확장된 문턱값과 두 번의 부과정을 거치는 EZW 부호기를 설계하고, 이 부호기를 이용하여 두 개의 부호 채널을 가지는 다중 기술 부호기를 제안한다. 제안된 부호기의 성능을 평가하기 위하여 두 개의 채널과 두 개의 기술을 가지는 영상 압축 실험을 행하고 이를 최근에 보고된 결과와 비교하였다. 폴리 페이즈 변환을 사용한 결과와 비교하여 제안 부호기의 성능이 더 우수함을 볼 수 있었다.

• 반도체디스플레이기술학회지
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• 제8권4호
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• pp.31-36
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• 2009

In this paper, the laser cutting characteristics of the flexible PCB using high power Nd:YAG UV laser were investigated. A specific FPCB model was selected for the experiment. Test sheets were made, which had equal materials and layer structure to those of the outline (OL) region and the contact pad (CP) region in the FPCB. The experiment is made up of two stages. In the first stage of the experiment, the laser cutting fluence was found, which is the threshold fluence to cut the test sheets completely. The laser cutting fluence of the OL sheet is $1781.26{\sim}1970.16\;J/cm^2$ and that of the CP sheet is $2109.34{\sim}2134.34\;J/cm^2$. In the second stage, cutting performance and its qualities were analyzed by the experiment. The laser cutting performance remained almost unchanged for all laser and process parameter sets. The average cutting width (top side/bottom side) of the OL sheet was $40.45\;{\mu}m/11.52\;{\mu}m$ and that of the CP sheet was $22.14\;{\mu}m/10.93\;{\mu}m$. However, the laser cutting qualities were different according to the parameters. The adjacent region of the cutting line on the OL sheet was carbonized as the beam speed was low and the overlap coefficient was high. The surface quality around the cutting line of the CP sheet was about the same. Carbonization and debris occurred on the surface of the cutting line. As a result of the experiment, the cutting qualities were better as the overlap coefficient was made low and beam speed high. Therefore, the overlap coefficient 2 or 3 is proper for the FPCB laser cutting.

• 한국멀티미디어학회논문지
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• 제14권10호
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• pp.1287-1302
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• 2011

무선 센서 네트워크에서 사용하는 클러스터링 기법은 전체 네트워크의 수명을 연장시키는 효율적인 방법이다. 그러나 이 방법은 기상감시 네트워크와 같이 센서 노드의 수집 데이터가 중복되기 쉬운 환경에 적용할 경우 노드가 불필요하게 소모하는 에너지가 많다. 문턱값(threshold)을 이용해 동작하는 클러스터링 기법의 경우 네트워크의 수명은 연장되었으나 수집하는 데이터의 정확도가 낮아 신뢰하기 어려운 문제점이 있어 이에 대한 개선이 필요하다. 또한 멀티 홉 전송을 이용하는 클러스터링 기법은 클러스터 헤드 노드 선정이 확률적으로 발생하므로 노드들의 링크가 단절되는 현상이 자주 일어나 데이터의 정상적인 수집이 어렵다. 이에 본 논문은 불필요한 에너지 소모를 줄이고 링크 단절 현상이 완화된 클러스터 형성 알고리즘을 제안하였다. 성능분석 결과에 의하면 제안하는 방법은 기존의 클러스터링 방법에 비해 노드들의 에너지 소모가 줄어들었으며 전송 효율이 증가하였고 수집 데이터의 정확도가 높아졌으며 전체 수명이 30% 정도 향상되었다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.359-364
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• 2006

Interference can seriously degrade the performance of GPS receiver because GPS signal has extremely low power at earth surface. This paper presents a Narrowband Interference Excision Filter (NIEF) in frequency domain that removes narrowband interferences with small signal loss. A NIEF transforms the received GPS signals with interferences into the frequency domain with FFT and then compute statistics such as mean and standard deviation to determine an excision threshold. All spectrums exceeding the threshold are removed and the remaining spectrums are restored by IFFT. A NIEF effectively can remove various and strong interferences with a simple structure. However, the signal power loss is unavoidable during FFT and IFFT. Besides the hamming window and overlap technique, a threshold-whitening technique and an adaptive detection threshold are adopted to effectively reduce the signal power loss. The performance of implemented NIEF is evaluated using real signals obtained by 12 bit GPS signal acquisition board. The output of NIEF is fed into the Software Defined Receiver to evaluate the acquisition and tracking performance. Experimental results shows that many types of interference such as single-tone CWI, AM, FM, swept CWI and multi-tones CWI are effectively mitigated with small signal power loss.