• 기술사
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• 제16권4호
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• pp.15-19
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• 1983

Therefore the use of Hadamard transform in the image processing requires only the real number operations and results in the computational advantages. Recently, however, certain degradation aspects have been reported. In this paper we propose a WH matrixtwhich retains the main properties of Hadamard matrix. The actual improvement of the image transmission in the inner part of the picture has been demonstrated by the computer simulated image developments. The orthogonal transforms such as Hadamard transform offers a useful facility in the digital signal processing. As the size of the transmission block increases, however, the assignment of bits for each data must increase exponentially. Thus the SNR of the image tends to decline accordingly. As an attempt to increase the SNR, we propose the WH matrix whose elements are made of ${\pm}$1, ${\pm}$2, ${\pm}$3, ${\pm}$4, and the unitform is 8${\times}$8 matrix.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2005년도 춘계학술발표대회
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• pp.1481-1484
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• 2005

In this paper, we propose a novel OFDM-based system structure to reduce PAPR (Peak-to-Average Power Ratio) and improve BER for OFDM system in which BER enhancement is obtainable based on WH (Walsh-Hadamard) transform to transmit concurrently each data symbol on all subcarriers so as to take advantage of frequency diversity and remedy the effect of channel's frequency-selectivity. By doing so, we also attain a low PAPR. Moreover, DGT (Data Grouping Technique) that is independent on the side information is also applied to further reduce PAPR. The simulation programs have been also performed to verify the validity of the proposed system.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1983년도 추계학술발표회논문집
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• pp.68-72
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• 1983

The Hadamard matrix is a symmetric matrix made of plus and minus ones as entries. There fore the use of Hadamard transform in the image processing requires only the real number operations and results in the computational advantages. Recently, However, certain degradation aspects have been reported. In this paper we propose a WH matrix which retains the main properties of Hadamard matrix. The actual improvement of the image transmission in the inner part of the picture has been demonstrated by the computer simulated image developments. The orthogonal transform offers a useful facility in the digital signal processing. As the size of the transmission block increases, however, the assigment of bits for each data must increase exponentially. Thus the SNR of the image tends to decline accordingly. As an attempt to increase the SNR, we propose the WH matrix whose elements are made of $\pm$1, $\pm$2, $\pm$3, and the unitform is 8$\times$8 matrix.

• 정보처리학회논문지C
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• 제12C권4호
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• pp.511-518
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• 2005

왈시-하다마다 변환(Walsh-Hadamard Transform, WHT)을 적용한 OFDM(Orthogonal Frequency Division Multiplexing) 변조방법은 시스템의 PAPR(Peak-to-Average Power Ratio)을 줄여주고, 시스템의 BER(Bit Error Rate) 성능을 향상시키는 장점이 있다. 그러나 기존의 이러한 왈시-하다마다 변환에 기반한 OFDM 시스템은 여전히 비교적으로 높은 PAPR문제가 있다. 그러므로 본 논문에서는 DGT(Data Grouping Technique)이라고 부르는 기술을 제안하고, 이 기술과 왈시-하다마다 변환 기술을 적용하여 PAPR을 더욱 줄여주는 OFDM 시스템을 설계한다. 제안한 DGT기술은 WHT-OFDM뿐만 아니라 일반 OFDM에서 PAPR을 줄여주는 방법들 중에서 큰 단점이 되는 부가정보(side information)가 성능에 대해 독립성을 가진다는 특징이 있다. 컴퓨터 시뮬레이션을 통해 제안한 시스템의 유용성을 검사하고 성능을 검증하였다.

• Composites Research
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• 제29권4호
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• pp.167-172
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• 2016

$Co_9S_8/reduced$ graphene (CSRG) has been prepared by a facile two step hydrothermal method and used as a supercapacitor electrode material. It is anticipated that the $Co_9S_8$ and reduced graphene oxide (RGO) would serve as a spacer material to each other to stop the agglomeration and simultaneous contribution of electrical double layer capacitance (RGO) and pseudocapacitance ($Co_9S_8$) would provide high electrochemical properties. The chemical analysis has been done by Fourier transform infrared spectroscopy and the morphology is characterised by field emission scanning electron microscopy. CSRG shows a high electrical conductivity of $98S\;m^{-1}$. The symmetric supercapacitor shows a specific capacitance of ${\sim}728F\;g^{-1}$ with a current density of $2A\;g^{-1}$. CSRG also showed an energy density of $25.2Wh\;kg^{-1}$ with a power density of $1000W\;kg^{-1}$.