• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.76-76
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• 2013

Scanning Tunneling Microscopy는 개인용컴퓨터가 보급되고, 저잡음 아날로그 칩들을 구할 수 있으며, 압전세라믹 기술이 발달하기 시작한 1981년 스위스 IBM Zurich 연구소에서 H. Rohrer와 G. Binnig 박사에 의하여 발명되었다. 이 발명 7~8년 이전 미국 표준연구원의 R. Young 박사도 비슷한 시도를 하였지만, 이 때는 제어할 수 있는 컴퓨터가 없었고, 조절 회로의 잡음 레벨도 컸으며, 역학적 진동도 커서 목적을 달성할 수 없었다. STM의 발명 후 32년이 지난 지금, 조절용 컴퓨터의 발전은 물론, 조절용 역되먹임 회로 또한 digital signal processor나 FPGA를 사용하는 형태로 변화하여 전기적 잡음도 현저히 감소하였다 [1,2]. 동시에 측정 에너지 해상도를 개선하기 위하여 세계적으로 여러 그룹이 장치를 1 K 이하에서 작동할 수 있게 제작하였고, 0.3 K에서 작동하는 상업용 제품도 등장하였다. 이 결과 에너지 해상도는 30 meV 에서 2~3 ${\mu}eV$ 감소하였고, 온도변화에 따른 측정 위치의 변화도 피할 수 있게 되었다. 터널링 검침의 화학적 성분을 흡착과 같은 방법으로 조절하여, 공간 해상도는 물론 에너지 해상도도 더욱 줄일 수 있게 되었고, 스핀에 민감한 터널링 제어도 가능하게 되었다. 이제는 금속, 반도체, 초전도체는 물론 분자, 거대분자, 나노 크기의 양자점등도 측정이 가능하게 되었다. 분자진동 측정이 가능하며, 분자의 성분 분석이 가능하게 되었고, 스핀의 전도와 관련된 제반 문제들을 연구할 수 있게 되었다. 지금부터 10년 동안에는 포논의 측정과 전자와 포논 exciton 등이 관여된 다체계 현상, 이들의 동역학적 현상이 측정 가능하게 되었다. 핵자기 공명도 시도되고 있으며 화학적 구명 및 원자들 사이의 결합도 측정 가능하게 될 것이다. 이제 STM은 초고 진공에서 작동하는 Atomic Force Microscopy와 함께 지금까지 고체물리학 실험 장치가 만들어 내지 못하던 새로운 결과를 도출해 낼 것으로 기대한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제18권5호
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• pp.663-674
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• 1993

In this paper, a DCT image coding algorithm using the human visual property is proposed. Human visual is relatively sensitive to noise in the darker region, insensitive to noise in the brighter region. This property was proved by Weber's law through psycovisual experiment. Weber's law states that the just noticeable difference (j.n.d.) is proportional to intensity. Therefore, the implication of this observation for image processing is that reducing noise in the darker region is more important than reducing noise in the brighter region. In this proposed coding scheme AC coefficients in the darker region are more finely quantized than those in the brighter region. Results showed that, at low bit rate, the subjective quality of reconstructed images by proposed coding scheme is improved than that of coding scheme without considering human visual property.

• The KIPS Transactions:PartC
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• 제9C권4호
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• pp.459-466
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• 2002

This paper proposes a robust speaker identification algorithm based on the wavelet filter banks and multiple decision-making scheme. Since the proposed speaker identification algorithm has a structure performing the identification algorithm independently for each subband, the noise effect of an subband can be localized. Through this process, we can obtain more robust results for the environmental noises which generally have band limited frequency. In the experiments, the proposed method showed more 15∼60% improvement than the vector quantization method for the various noisy environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제28권6C호
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• pp.570-579
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• 2003

The performance of turbo codes is investigated in the direct detection optical PPM channel. We assume that an ideal photon counter is used as an optical detector and that the channel has background noise as well as quantum noise. Resulting channel model is M-ary PPM Poisson channel. We propose the structure of the transmitter and receiver for applying turbo codes to this channel. We also derive turbo decoding algorithm for the proposed coding system, by modifying the calculation of the branch metric inherent in the original turbo decoding algorithm developed for the AWGN channel. Analytical bounds are derived and computer simulation is performed to analyze the performance of the proposed coding scheme, and the results are compared with the performances of Reed-Solomon codes and convolutional codes.

• Journal of the Korean Institute of Telematics and Electronics
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• 제27권3호
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• pp.13-20
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• 1990

This paper describes an interframe image coding using motion compensated and classified vector quantizer (MC-CVQ). It is essential to carefully encode blocks with significant pels in motion compensated vector quantizers (MCVQ). In this respect, we propose a new CVQ algorithm which is appropriate to the coding of interframe prediction error after motion compensation. In order to encode an image efficiently at a low bit rate, we partition each block, which is the processing element in MC, into equally sized 4 vectors, and classify vectors into 15 classes according to the position of significant pels. Vectors in each class are then encoded by the vector quantizer with the codebook independently designed for the class. The computer simulation shows that the signal-to-noise ratio and the average bit rate of MC-CVQ are 35-37dB and 0.2-0.25bit/pel, respectively, for the videophone or video conference type image.

• Journal of the Institute of Electronics Engineers of Korea SD
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• 제40권5호
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• pp.335-344
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• 2003

The image compression based on discrete wavelet transform has been widely accepted in industry since it shows no block artifacts and provides a better image quality when compressed to low bits per pixel, compared to the traditional JPEG. The coefficients generated by discrete wavelet transform are quantized to reduce the number of code bits to represent them. After quantization, lossless coding processes are usually applied to make further reduction. This paper presents a new and efficient lossless coding algorithm for quantified wavelet coefficients based on the statistical properties of the coefficients. Combined with discrete wavelet transform and quantization processes, our algorithm has been implemented as an image compression chip, using 0.5${\mu}{\textrm}{m}$ standard cells. The experimental results show the efficiency and performance of the resulting chip.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제19권5호
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• pp.822-832
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• 1994

DSC-HDTV image compression algorithm removes spatial, temporal, and amplitude redundancies of an image by using transform coding, motion-compensated predictive coding, and adaptive quantization, respectively. In this paper, leak processing method which is used to recover image quality quickly from scene change and transmission error and adaptive quantization using perceptual weighting factor obtained by HVS are proposed. Perceptual weighting factor is calculated by contrast sensitivity, spatio-temporal masking and frequency sensitivity. Adaptive quantization uses the perceptual weighting factor and global distortion level from buffer history state. Redundant bits according to adaptation of HVS are used for the next image coding. In the case of scene change, DFD using motion compensated predictive coding has high value, large bit rate and unstabilized buffer states since reconstructed image has large quantization noise. Thus, leak factor is set to 0 for scene change frame and leak factor to 15/16 for next frame, and global distortion level is calculated by using standard deviation. Experimental results show that image quality of the proposed method is recovered after several frames and then buffer status is stabilized.

• Journal of Convergence for Information Technology
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• 제11권9호
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• pp.124-129
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• 2021

A time-interpolation technique has been applied to the conventional FLASH analog-to-digital converter (ADC) to increase a number of quantization level, thus it reduces not only a power dissipation, but also minimize an active chip area. In this work, we demonstrated 5-bit ADC which has 31 quantization levels consisting of 16 conventional voltage-mode comparators and 15 time-mode comparators. As a result, we have achieved about 48.4% voltage-mode comparator reductions. The ADC is fabricated in a 14nm fin Field-effect transistor (FinFET) process with an active die area of 0.0024 mm2 while consuming 0.82 mW through a 0.8 V supply. At 400-MS/s conversion rate, the ADC performs 28.03 dB SNDR (4.36 ENOB) at 21MHz input frequency.

• Journal of the Korean Institute of Telematics and Electronics S
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• 제35S권11호
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• pp.144-151
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• 1998

In this paper, it is applied the analysis properties of mathematical morphology in order to process MIN/MAX operation on the basis of combination of predefined and weighted structuring element to FCNN having the structure of CNN combined with fuzzy logic between template and input/output. In this paper, as the fuzzy estimator is applied to the image including noise, thus it could be found the noise removal as well as the edge detection in the process of computer simulation. We could analyze and compare the results of edge detection using FCNN, CNN and median filter to which the erosion operation of morphology is applied. This paper could apply the static template and the variable template to FCNN using the quantization fuzzy function, in result we could confirm that the performance of FCNN got to improve in the process of computer simulation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• 제38권4호
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• pp.442-452
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• 2001

In this paper, we proposed a postprocessing algorithm for quantization effects reduction in block coded images using the block classification and adaptive filtering. The proposed method consists of classification, adaptive inter-block filtering, and intra-block filtering. First, each block is classified into one of seven classes based on the characteristics of 8$\times$8 DCT coefficients. Then each block boundary is filtered by adaptive inter-block fitters according to the block classification. finally for blocks which are classified into edge block, intra-block filtering is performed. Experimental results show that the proposed method gives better results than the conventional methods from both a subjective and an objective viewpoint.