• 대한전자공학회논문지SP
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• 제45권4호
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• pp.1-9
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• 2008

본 논문은 DC 영상을 이용하여 기하학적 변환에 강인하며 고속처리가 가능한 워터마킹 알고리즘을 제안한다. 제안하는 방법은 JPEG 및 MPEG 영상압축 기술에 널리 사용되는 $8{\times}8$ 블록 DCT를 기반으로 하며, DC 성분만으로 구성된 DC 영상에 DWT 수행 후 웨이블릿 계수에 워터마크를 삽입한다. DC 성분을 이용한 워터마크 삽입으로 야기될 수 있는 화질 열화를 극복하기 위하여 DWT의 서브밴드 마다 워터마크 삽입 강도와 삽입량을 차별화한다. 제안하는 알고리즘은 $8{\times}8$ 블록 DCT 영역의 부분적인 복호화(즉, DC 영상)를 수행함으로써 실시간 워터마크 삽입 및 추출을 위한 고속처리가 가능하다. 실험결과로부터 제안한 워터마킹 방법이 기존의 DC 성분을 이용한 알고리즘과 비교하여 82%의 계산시간을 단축하였으며 다양한 기하학적 공격과 JPEG 압축 등의 기타 공격에 강인한 것을 확인하였다.

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1633-1642
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• 2002

Uninterrupted power supply has become indispensable during the maintenance task of active electric power lines as a result of today's highly information-oriented society and increasing demand of electric utilities. The maintenance task has the risk of electric shock and the danger of falling from high place. Therefore it is necessary to realize an autonomous robot system using electro-hydraulic manipulator because hydraulic manipulators have the advantage of electric insulation. Meanwhile it is relatively difficult to realize autonomous assembly tasks particularly in the case of manipulating flexible objects such as electric lines. In this report, a discrete event control system is introduced for automatic assembly task of electric lines into sleeves as one of the typical task of active electric power lines. In the implementation of a discrete event control system, LVQNN (linear vector quantization neural network) is applied to the insertion task of electric lines to sleeves. In order to apply these proposed control system to the unknown environment, virtual learning data for LVQNN is generated by fuzzy inference. By the experimental results of two types of electric lines and sleeves, these proposed discrete event control and neural network learning algorithm are confirmed very effective to the insertion tasks of electric lines to sleeves as a typical task of active electric power maintenance tasks.

• 융합정보논문지
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• 제8권5호
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• pp.153-158
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• 2018

본 논문에서는 가시광 통신시스템에서 조명과 통신의 성능을 동시에 만족하기 위한 Dimming level control 기법을 연구하였다. 일반적으로 가장 많이 사용되는 OOK와 RZ-OOK변조 방식의 경우, 연속적인 Burst Zero Duration이 발생하면 조명 기능이 심각하게 저하된다. 이는 조명뿐만 아니라 시스템 전체의 성능을 열하시키는 원인이 된다. 본 연구를 통해, 기존 시스템의 Dimming level특성을 분석하고, Dimming level을 높이기 위한 기법으로 Illegal Pulse Insertion(IPI) 알고리즘을 제안하였다. 이를 통해, Dimming level을 효과적으로 제어하고 기존 변복조 시스템에서 나타나는 플리커(flicker) 현상과 Dimming level 감소를 해결하여 조명과 통신 양쪽 모두의 QoS를 향상 시킬 수 있다.

• 한국군사과학기술학회지
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• 제14권3호
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• pp.482-491
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• 2011

The purpose of this study is to design and implement a 2-level secret information transmission system which can be used for information hiding of images transmitted over various IT communication media. To increase the robustness of the hiding power, we combined the steganography method which inserts secret object into cover object to hide the very fact of information hiding itself, and the preprocessing stage to encrypt the secret object before the stego-insertion stage. As a result, even when the stego-image is broken by an attacker, the secret image is protected by encryption. We implemented the 2-level image insertion and extraction algorithm by using C++ programming language. Experiment shows that the PSNR values of stego-images of ours exceed 30.00db which is the threshold of human recognition. The methodology of this study can be applied broadly to the information hiding and protection of the military secret images.

• 대한전기학회논문지:전력기술부문A
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• 제52권12호
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• pp.675-683
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• 2003

This paper describes the correction strategy of an overcurrent relay applied in the linked line for interconnecting wind farm with utility power networks in order to improve the capability of a fault detection. The fault current measured in a relaying point might vary according to the fault conditions. Generally, the current of the line to line fault or the line to ground fault in the linked line is much higher than the set value of protective relay due to the large fault level. However, when the high impedance fault occurs in the linked line, we can't detect it by conventional set value because its fault level may be lower than the generating capacity of wind farm. And, the protective relay with conventional set value may generate a trip signal for the insertion of wind turbine generators due to the large transient characteristics. In order to solve above problems and improve protective relaying algorithms applied in the linked line, we propose a new correction strategy of the protective relay in the linked line. The presented method can detect the high impedance fault which can't be detected by conventional relay set value and may prevent the mis-operation of protective relay caused by the insertion of wind farm.

• ETRI Journal
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• 제36권6호
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• pp.931-941
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• 2014

Many methodologies for clock mesh networks have been introduced for two-dimensional integrated circuit clock distribution networks, such as methods to reduce the total wirelength for power consumption and to reduce the clock skew variation through consideration of buffer placement and sizing. In this paper, we present a methodology for clock mesh to reduce both the clock skew and the total wirelength in three-dimensional integrated circuits. To reduce the total wirelength, we construct a smaller mesh size on a die where the clock source is not directly connected. We also insert through-silicon vias (TSVs) to distribute the clock signal using an effective clock TSV insertion algorithm, which can reduce the total wirelength on each die. The results of our proposed methods show that the total wirelength was reduced by 12.2%, the clock skew by 16.11%, and the clock skew variation by 11.74%, on average. These advantages are possible through increasing the buffer area by 2.49% on the benchmark circuits.

• 정보보호학회논문지
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• 제20권3호
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• pp.135-140
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• 2010

중국인의 나머지 정리(Chinese Remainder Theorem)를 이용한 RSA 암호 시스템(RSA-CRT)에서의 연산은 기존의 일반 RSA 멱승 연산보다 빠르게 처리할 수 있어 디지털 서명이나 복호 과정에서 많이 사용된다. 그러나 RSA-CRT는 오류주입 공격에 매우 취약한 특성을 보여 많은 대응책이 제안되고 있다. 이 중에서 Yen 등은 오류 확산 기법을 사용한 두 가지 대응책을 제안하였는데 FDTC 2006에서는 그에 대한 새로운 공격 방법이 제시되었다. 그러나 Kim 등은 비트 연산 중 AND 연산의 특성을 이용하여 FDTC 2006에서 제시한 공격을 방어하는 방법을 제안하였다. 본 논문에서는 Kim 등이 제안한 AND 연산을 이용한 오류 확산 기법이 선택 메시지에 대한 오류주입 공격에 취약하여 안전하지 않음을 밝히고자 한다.

• 한국정밀공학회지
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• 제12권5호
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• pp.126-135
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• 1995

An exhaust muffler is one of the simple and effective means to meet the demand for a quiet vehicle, and it deserves a close attention to effectively reduce the engine noise. The transfer function technique is one of the tools that have been used to analyze the noise characteristics of the exhaust muffler. In this paper we obtained a transfer function using the forward-going and backward-going components of sound pressure in the exhaust muffler, which is compatible wiht lattice filter algorithm. This form of transfer function is obtained for the basic elements of a muffler, such as uniform tube, open termin- ation, closed termination, anechoic termination, expansion, contraction, extended-tube resonator, hole, Helmholtz resonator, and concentric hole-cavity resonator. The results are combined to produce the transfer function of various types of mufflers. With this transfer function we calculate the transmission and insertion losses of mufflers, and examined the effects of various design parameters. Comparisons were made between the calculation and experimental results, which showed a good agreement, and we conclude that the transfer function of lattice form can be used to analyze the noise characteristics of the exhaust mufflers.

• 한국정밀공학회지
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• 제11권1호
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• pp.80-88
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• 1994

In the automation of rigid parts mating process with the intelligent robots, Peg-In-Hole is the most available task since inserting is some analytic and needs suitable range of forces that can be controlled by induatrial manipulators. In this Peg-In-Hole process, it is very important to identify the contact state between tow parts, peg and hole, to build the strategies for robot motion that leads to avoid the jamming condition occurs during insertion process. In this paper, we adpopted 3 parameters for identification, lFzl, lFxy/Fzl, and lMxy/Fxyl, derived from axes value of Whitney's jamming diagram. Also, we defined the fuzzy membership functions for these parameters and developed the identification algorithm based on fuzzy inference method of max-product. As an experimental result, we obtained about 96% of identification ratio that could be raised up to industrial requirements by further research.

• International Journal of Control, Automation, and Systems
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• 제6권6호
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• pp.794-799
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• 2008

This paper presents a user identification method at H.264 streaming using watermarking with fingerprints. The watermark can efficiently reduce the potential danger of forgery or alteration. Especially a biometric watermark has convenient, economical advantages. The fingerprint watermark can also improve reliability of verification using automated fingerprint identification systems. These algorithms, however, are not robust against common video compression. To overcome this problem, we analyze H.264 compression pattern and extract watermark after restoring damaged watermark using various filters. The proposed algorithm consists of enhancement of a fingerprint image, watermark insertion using discrete wavelet transform and extraction after restoring. The proposed algorithm can achieve robust watermark extraction against H.264 compressed videos.