• 한국기계기술학회지
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• 제13권3호
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• pp.7-16
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• 2011

This study proposes the compensation method for the mechanical deflection error of a SCARA robot. While most studies on the related subject have dealt with the development of a control algorithm for improvement of robot accuracy, this study presents the control method reflecting the mechanical deflection error which is predicted in advance. The deflection at the end of the gripper of SCARA robot is caused by the self-weights and payloads of Arm 1, Arm 2 and quill. If the deflection is constant even though robot's posture and payload vary, there may not be a big problem on robot accuracy because repetitive accuracy, that is relative accuracy, is more important than absolute accuracy in robot. The deflection in the end of the gripper varies as robot's posture and payload change. That's why the moments $M_x$, $M_y$ and $M_z$ working on every joint of a robot vary with robot's posture and payload size. This study suggests the compensation method which predicts the deflection in advance with the variations in robot's posture and payload using neural network. To do this, I chose the posture of robot and the payloads at random, found the deflections by the FEM analysis, and then on the basis of this data, made compensation possible by predicting deflections in advance successively with the variations in robot's posture and payload through neural network learning.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권6호
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• pp.2817-2834
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• 2016

The existing reversible data hiding methods for block truncation coding (BTC) compressed images often utilize difference expansion or histogram shifting technique for data embedment. Although these methods effectively embed data into the compressed codes, the embedding operations may swap the numerical order of the higher and lower quantization levels. Since the numerical order of these two quantization levels can be exploited to carry additional data without destroying the quality of decoded image, the existing methods cannot take the advantages of this property to embed data more efficiently. In this paper, we embed data by shifting the higher and lower quantization levels in opposite direction. Because the embedment does not change numerical order of quantization levels, we exploit this property to carry additional data without further reducing the image quality. The proposed method performs no-distortion embedding if the payload is small, and performs reversible data embedding for large payload. The experimental results show that the proposed method offers better embedding performance over prior works in terms of payload and image quality.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권6호
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• pp.1619-1637
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• 2024

In today's highly digitized landscape, securing digital communication is paramount due to threats like hacking, unauthorized data access, and network policy violations. The response to these challenges has been the development of cryptography applications, though many existing techniques face issues of complexity, efficiency, and limitations. Notably, sophisticated intruders can easily discern encrypted data during transmission, casting doubt on overall security. In contrast to encryption, steganography offers the unique advantage of concealing data without easy detection, although it, too, grapples with challenges. The primary hurdles in image steganography revolve around the quality and payload capacity of the cover image, which are persistently compromised. This article introduces a pioneering approach that integrates image steganography and encryption, presenting the BitPatternStego method. This novel technique addresses prevalent issues in image steganography, such as stego-image quality and payload, by concealing secret data within image pixels with identical bit patterns as their characters. Consequently, concerns regarding the quality and payload capacity of steganographic images become obsolete. Moreover, the BitPatternStego method boasts the capability to generate millions of keys for the same secret message, offering a robust and versatile solution to the evolving landscape of digital security challenges.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.389-392
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• 2000

Electronics and Telecommunications Research Institute (ETRI) developed the Ka-band satellite communications payload. This system is able to provide a high data rate communication service with a bandwidth of 200 MHz, a wideband digital flunking services up to 155 Mbps and asymmetrical internet multimedia service. The system employs the common receive/transmit antenna and the 2-for-1 redundant scheme for the LNA-Downconverters. The different types of high power amplification, TWTA for one chain and SSPA for the other chain, are used lot the variety of experimental options. For the reliable test of the payload, EGSE was also developed. The parametric RF tests were carried out in order to measure the performance of Ka-band communication subsystem, in most case the results of RF performance test complied the payload requirement.

• 한국컴퓨터정보학회논문지
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• 제8권3호
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• pp.144-149
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• 2003

멀티미디어 데이터는 실시간 제약을 갖고 있기 때문에 암호화/복호화로 인한 지연이 실시간 제약에 미치는 영향을 최소로 하면서 암호화를 하기 위해서는 네트워크 트래픽과 부하에 적응하여 암호화 알고리즘을 변경하기 위한 방법이 필요하다. 또한 다수가 참여하는 멀티미디어 서비스 진행 중에 서비스 이용을 중지한 사용자는 RTP payload의 암호화 키를 알고 있기 때문에 이 사용자로부터 RTP payload를 보호하기 위해서는 암호화 키를 변경하기 위한 방법이 필요하다. 따라서 본 논문에서는 RTP payload의 암호화를 위해 암호화 알고리즘과 암호화 키를 변경하기 위한 RPT 보안제어 프로토콜을 설계하고 구현하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.101-101
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• 2000

MSC(Multispectral Camera), which will be a unique payload on KOMPSAT-II, is designed to collect panchromatic and multi-spectral imagery with a ground sample distance of 1m and a swath width of 15km at 685km altitude in sun-synchronous orbit. The instrument is designed to have an orbit operation duty cycle of 20% over the mission life time of 3 years. MSC electronics consists of three main subsystems; PMU(Payload Management Unit), CEU(Camera Electronics Unit) and PDTS(Payload Data Transmission Subsystem). PMU performs all the interface between spacecraft and MSC, and manages all the other subsystems by sending commands to them and receiving telemetry from them with software protocol through RS-422 interface. CEU controls FPA(Focal Plane Assembly) which contains TDI(Timc Delay Integration) CCD(Charge Coupled Device) and its clock drivers. PMU provides a Master Clock to synchronize panchromatic and multispectral camera. PDTS performs compression, storage and encryption of image data and transmits them to the ground station through x-band.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.258-261
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• 2006

The structure of small launch vehicle can be divided into engine section and payload section. This paper introduces modal test of the payload section of small launch vehicle which is composed to satellite, PLA (Payload Adapter), VEB (Vehicle Equipment Bay), KMS (Kick Motor Support) and KM (Kick Motor). From this test, dynamic properties of the 2nd stage structure of small launch vehicle can be obtained. In this test, to simulate free-free boundary condition, test object was hung by 4 bungee cords and excited by using impact hammer Modal test data are analyzed by using TDAS(Test Data Analysis Software). As the result, modal parameters and mode shapes below 100Hz of the 2nd stage of small launch vehicle were identified.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.907-909
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• 1995

The SaTReC is to develop, deploy, and operate a low Earth orbiting small satellite system, KITSAT-3, carrying a remote sensing payload, a space science payload, and a data collection system. Through the development of KITSAT-3, the SaTReC is to demonstrate the small satellite system which provides highly accurate attitude control, high speed data transmission, and a unique spacecraft configuration and to provide educational opportunities to Korean space industries and research institute. The KITSAT-3 is expected to be launched in the beginning of 1997 by Chinese Long March IV as a secondary payload into about 800 km's sunsynchronous orbit.

• 한국항행학회논문지
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• 제9권2호
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• pp.140-146
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• 2005

본 논문에서는 HDR-WPAN 시스템에 적합한 주파수 옵셋 보상과 누적 위상오차를 개선할 수 있는 트래킹 알고리즘을 제안하고 이에 대해 분석하였다. 주파수 옵셋 보상 알고리즘은 CAZAC sequence의 자기상관 특성을 이용하여 각 심벌 내 샘플 간 위상오차를 통해 coarse 주파수 옵셋과 fine 주파수 옵셋을 추정하게 된다. 그러나 HDR-WPAN 시스템은 payload에 pilot 심벌이 없기 때문에 payload 길이가 길어질수록 샘플 간 미소 위상오차가 누적되어 수신단의 성상도가 회전하게 된다. 따라서 트래킹 알고리즘을 통해 틀어진 누적 위상오차를 보상해야 한다. 트래킹은 성상도내 들어온 신호가 일정 영역을 벗어나게 되면, 벗어난 만큼의 크기 ${\theta}$을 곱해 누적된 미소 위상오차를 보상하게 된다.

• 드라이브 ㆍ 컨트롤
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• 제19권2호
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• pp.11-16
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• 2022

It is important to measure the excavator's work productivity that estimates the bucket's payloads on a process. If the bucket isn't filled at every working cycle, the excavator's operator has to drive the machine more to achieve his work quota. If bucket is filled over with the load, the other way around, the transferred object has to spread out on the workplace. That causes additional work to clean the site. This paper proposes a method that can estimate the bucket's payload to improve the excavator's work productivity. This method assumes that the excavator is a lumped mass system. And it uses a 3 points angle (boom link, arm link, swing) and 2 points pressure (boom cylinder's input port and output port) of measurable data. Depending on assumptions, the bucket's payload can be calculated by the payload's motion equation. And this suggested method can be verified by simple experiments.