• Macromolecular Research
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• v.9 no.3
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• pp.171-178
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• 2001

We report the diffraction behavior of the functionalized sol-gel film composed of two different silanes. One silane (SGDR1) contains disperse red 1 (DR1) that is composed of an azobenzene unit. The other silane (SGCHC) bears a chalcone derivative that is photocrosslinkable under UV irradiation. Two-beam coupling method was employed for fabricating the diffraction gratings. The dynamics of formation and erasure of the gratings was studied in term of the variation of the diffraction efficiency. The decaying behavior of the polarization efficiency was also observed after turning off the two pump beams. For complete erasure of the diffraction gratings, we irradiated the linearly polarized single beam. During two-beam coupling, we irradiated UV light on the film surface. The effects of the photocrosslink between the double bonds in chalcone units on the value and dynamic properties of diffraction efficiency are mainly studied in this work.

• ETRI Journal
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• v.38 no.5
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• pp.896-902
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• 2016

Luby transform (LT) codes were the first practical rateless erasure codes proposed in the literature. The performances of these codes, which are iteratively decoded using belief propagation algorithms, depend on the degree distribution used to generate the coded symbols. The existence of degree-one coded symbols is essential for the starting and continuation of the decoding process. The absence of a degree-one coded symbol at any instant of an iterative decoding operation results in decoding failure. To alleviate this problem, we proposed a method used in the absence of a degree-one code symbol to overcome a stuck decoding operation and its continuation. The simulation results show that the proposed approach provides a better performance than a conventional LT code and memory-based robust soliton distributed LT code, as well as that of a Gaussian elimination assisted LT code, particularly for short data lengths.

• Structural Engineering and Mechanics
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• v.25 no.4
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• pp.423-444
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• 2007

By using the incremental form of the endochronic theory of plasticity, a model of material function is proposed in this paper to investigate plastic behavior. By comparing the stress-strain hysteresis loop, the theory is shown to agree well with the experimental results, especially in the evolution of peak stress values of SAE 4340 steel loaded by cyclic loading with various amplitudes. Depending on the choice of material parameters, the present model can substantially result in six categories of material function, each of which can behave differently with respect to an identical deformation history. In addition, the present model of material function is shown to be capable of describing the behavior of erasure of memory of materials, as experimentally observed by Lamba and Sidebottom (1978).

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.7-10
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• 2000

본 논문은 이동통신상에서 송신측의 송신 채널 에러정보를 수신측에서 송신측으로 전달하는 음성패킷을 이용하여 송신측에 알려주어 압축과정에 이용하게 할 수 있는 방법을 제안한다. ACELP(Algebraic CELP)구조 방식을 가지고 있는 음성압축기들 중 G.729을 사용하며 음성 패킷정보 중 Pitch Delay와 Fixed Codebook를 이용하여 전송음성 패킷안에 상대방의 송신 채널정보를 싣는다. 수신측에서 받은 패킷이 Erasure로 판단되었을 때 패킷정보들 중 Fixed Codebook Index를 만들게 되는 4개의 Optimal 펄스 중 2개의 펄스만 사용하며 나머지 2개의 펄스는 약속된 임의의 위치에 위치시킨 후 송신측에 전송시킨다. 상대방에서 약속에 맞는 위치의 펄스를 보내왔을 때를 체크함으로써 자신의 송신채널 상태를 알 수 있게 된다 송신채널에$5\%$ Erasure 채널 에러가 발생했을 때 채널정보를 가진 패킷의 음질은 약 0.1dB 정도 떨어지게 된다. 하지만 음성압축 전송 시 송신채널의 정보를 이용하여 무선채널에러에 강하게 할 수 있다.

• Journal of Information Processing Systems
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• v.15 no.1
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• pp.55-66
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• 2019

Storage system often applies erasure codes to protect against disk failure and ensure system reliability and availability. Liberation code that is a type of coding scheme has been widely used in many storage systems because its encoding and modifying operations are efficient. However, it cannot effectively achieve fast recovery from single disk failure in storage systems, and has great influence on recovery performance as well as response time of client requests. To solve this problem, in this paper, we present HRSF, a Hybrid Recovery method for solving Single disk Failure. We present the optimal algorithm to accelerate failure recovery process. Theoretical analysis proves that our scheme consumes approximately 25% less amount of data read than the conventional method. In the evaluation, we perform extensive experiments by setting different number of disks and chunk sizes. The results show that HRSF outperforms conventional method in terms of the amount of data read and failure recovery time.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.347-350
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• 2013

본 논문에서는 무선 인터넷이 대중화 되면서 프록시 서버의 역할의 중요성과 대용량 데이터 보안, 대용량 트래픽을 처리할 수 있는 확장성이 요구되어지고 있다. 무선 인터넷은 유선 인터넷과 달리 기술 환경과 그 특성상 여러가지 제약점들을 가지고 있다. 낮은 대역폭, 이동성 문제, 네트워크 프로토콜, 보안, 데이터 압축, 캐싱 방법 등 아직 기술적으로 해결하여야 문제점을 가지고 있다. 본 논문에서는 데이터 보안을 위하여 무선 인터넷 프록시 서버에 Erasure code 코드를 사용하여 기밀성, 무결성, 가용성 등을 강화하면서 서버의 성능 저하를 해결하기 위하여 서버 부하분산을 적용시키고자 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.2
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• pp.22-28
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• 2007

High PAPR (peak-to-average power ratio) is a major drawback of OFDM (orthogonal frequency division multiplexing) signals. In this paper, a modified SLM (selective mapping) technique that uses erasure decoding of RS (Reed-Solomon) codes is presented. At the transmitter a set of phase sequences are multiplied such that some portions of check symbols in RS-coded OFDM data blocks are phase-rotated. At the receiver, RS decoding is performed with the phase-rotated check symbols being treated as erasures. Hence, there is no need to send side information about the phase sequence selected to transmit for the lowest PAPR. In addition, the estimation process for the selected phase sequence is no longer needed at the receiver, leading to improvement in terms of complexity and performance. To evaluate the performance of this technique, the CCDF (complementary cumulative distribution function) of PAPR, the BER (bit error rate) and the decoding failure probability are compared with those of the previous SLM techniques.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.1
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• pp.62-77
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• 2010

Emerging applications with high data rates will need to transport bulk data reliably in wireless sensor networks. ARQ (Automatic Repeat request) or Forward Error Correction (FEC) code schemes can be used to provide reliable transmission in a sensor network. However, the naive ARQ approach drops the whole frame, even though there is a bit error in the frame and the FEC at the bit level scheme may require a highly complex method to adjust the amount of FEC redundancy. We propose a bulk data transmission scheme based on erasure-resilient code in this paper to overcome these inefficiencies. The sender fragments bulk data into many small blocks, encodes the blocks with LT codes and packages several such blocks into a frame. The receiver only drops the corrupted blocks (compared to the entire frame) and the original data can be reconstructed if sufficient error-free blocks are received. An incidental benefit is that the frame error rate (FER) becomes irrelevant to frame size (error recovery). A frame can therefore be sufficiently large to provide high utilization of the wireless channel bandwidth without sacrificing the effectiveness of error recovery. The scheme has been implemented as a new data link layer in TinyOS, and evaluated through experiments in a testbed of Zigbex motes. Results show single hop transmission throughput can be improved by at least 20% under typical wireless channel conditions. It also reduces the transmission time of a reasonable range of size files by more than 30%, compared to a frame ARQ scheme. The total number of bytes sent by all nodes in the multi-hop communication is reduced by more than 60% compared to the frame ARQ scheme.

• The Transactions of the Korea Information Processing Society
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• v.5 no.10
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• pp.2654-2662
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• 1998

Maximum single bus throughput of standard IEEE 802.6 DQDB(Distributed Queue Dual Bus) is not obtained over 1. Therefore, lots of studies for improving bus throughput have done by QA slot preuse/reuse. We propose three calculation cethods for network's utilization with preuse/reuse scheme based on erasure nodes. One is calculation method by traffic density function, other is calculation method for obtaining maximum throughput. The other is calculation method using probability concept which follows real DQDB operation mechanisms. The calculated throughputs are compared with each others. The results shows some favorite phenomena. The proposed calculation methods can be casily expanded in mumber of nodes or in number of erasure nodes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8C
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• pp.775-781
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• 2007

In this paper, a modified PTS(Partial Transmit Sequences) technique that uses erasure decoding of RS (Reed-Solomon) codes is presented. At the transmitter, some check symbols in a RS codeword partitioned into subblocks are phase-rotated by phase factors. The receiver decodes received codewords by regarding the phase-rotated check symbols as erasures. Hence, this technique does not need to transmit the side information about the phase factors chosen at the transmitter. The complexity of the receiver is also reduced since the estimation process for the phase factors is not required in the receiver. There is no performance degradation due to the transmission error of the side information or the estimation error of the phase factors. To evaluate the performance of the proposed PTS technique, the CCDF(Complementary Cumulative Distribution Function) of PAPR and the BER(Bit Error Rate) are compared with those of the conventional PTS techniques.