• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.113-116
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• 2001

Reed-Solomon(RS) code is the most powerful burst error correcting code. In Ois paper, the architecture for the adaptive RS encoder adaptable for multi QoS requirements or time-varying channel environments has been designed. In the adaptive RS code, the message length k and the error correction capability t are allowed to be variable so that the block length n is also variable. We proposed the architecture of the adaptive RS encoder by designing the optimal structure of Galois fields multiplier with comparison of fixed multiplier and variable multiplier. The proposed architecture is implemented in VHDL and verified with the simulation tool

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.137-142
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• 2004

In this paper, we propose a new scheme for geometry coding of three-dimensional (3-D) mesh models using a fixed spectral basis. In order to code the mesh geometry information, we generate a fixed spectral basis using the dual graph derived from the 3-D mesh topology. After we partition a 3-D mesh model into several independent sub-meshes to reduce coding complexity, the mesh geometry information is projected onto the generated orthonormal bases which are the eigenvectors of the Laplacian matrix of the 3-D mesh. Finally, spectral coefficients are coded by a quantizer and a variable length coder. The proposed scheme can not only overcome difficulty of generating a fixed spectral basis, but also reduce coding complexity. Moreover, we can provide an efficient multi-resolution representation of 3-D meshes.

• 한국통신학회논문지
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• 제34권1C호
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• pp.113-119
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• 2009

The training sequence with the appropriate length for equalization and initial synchronization is necessary before sending the pure data in the burst transmission type DS-UWB system. The length of the training sequence is one of the factors which make throughput decreased. The noble structure with the variable length of the training sequence whose length can be adaptively tailored according to the channel conditions (CM1,CM2,CM3,CM4) in the DS-USB systems is proposed. This structure can increase the throughput without sacrificing the performance than the method with fixed length of training sequence considering the worst case channel conditions. Simulation results under IEEE 802.15.3a channel model show that the proposed scheme can achieve higher throughput than a conventional one with the slight loss of BER performance. And this structure can reduce the computation complexity and power consumption with selecting the short length of the training sequence.

• 한국통신학회논문지
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• 제15권8호
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• pp.698-707
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• 1990

현재 가장 널리 쓰이고 있는 압축알고리즘의 하나인 LZW 압축알고리즘은 이미 많은 연구에서 밝혀진 바 있듯이, 그 알고리즘 자체가 일련의 용장성은 내포하고 있다. 따라서 본 논문에서는 기존의 VF(Variable-to-Fixed)형 LZW 압축 알고리즘을 VV(Variable-to-Variable)형으로 개선함으로써, 그 용장성을 제거하였다. 결과적으로 본 개선알고리즘인 VV형이 VF형보다 압축효율, 특히 초기 압축효율에 있어서 더 우수함을 실험, 입증하였으며, 또 VV 형의 압축후 출력비트열이 VF형보다 용장성이 더 작기 때문에 암호화에 이용시 보다 효과적임을 보였다.

• The Journal of Advanced Prosthodontics
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• 제7권3호
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• pp.240-248
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• 2015

PURPOSE. To explore whether there is matching relation between the length and the tilting angle of terminal implants in the All-on-Four protocol by studying the effects of different implant configurations on stress distributions of implant, bone, and framework. MATERIALS AND METHODS. Four implants were employed to support a full-arch fixed prosthesis and five three-dimensional finite element models were established with CT images, based on the length (S and L) and distal tilt angle ($0^{\circ}$, $30^{\circ}$ and $45^{\circ}$) of terminal implants for an edentulous mandible, which named: Tilt0-S, Tilt30-S, Tilt30-L, Tilt45-S and Tilt45-L. An oblique 240 N was loaded at second molar. The von Mises Stresses were analyzed. The implants were consecutively named #1 to #4 from the loading point. RESULTS. 1) Tilt0-S had the greatest stress on the implants, with the other groups exhibiting variable reductions; the four implants of Tilt45-L demonstrated the greatest reduction in stress. 2) Tilt0-S had the greatest stress at bone around #1 implant neck, and Tilt45-L exhibited the least stress, which was a 36.3% reduction compared to Tilt0-S. 3) The greatest stress in the framework was found on the cantilevers distal to #1 implant. Tilt45-S exhibited the least stress. CONCLUSION. Matching different length and tilting angle of the terminal implants led to variable stress reductions on implants, bone and the superstructure. By optimizing implant configuration, the reduction of stress on implants and surrounding bone could be maximized. Under the present condition, Tilt45-L was the preferred configuration. Further clinical testings are required.

• Structural Engineering and Mechanics
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• 제73권2호
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• pp.109-121
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• 2020

This study aims to estimate crack location and crack length in damaged beam structures using transfer matrix formulations, which are based on analytical solutions of governing equations of motion. A single variable shear deformation theory (SVSDT) that considers parabolic shear stress distribution along beam cross-section is used, as well as, Timoshenko beam theory (TBT). The cracks are modelled using massless rotational springs that divide beams into segments. In the forward problem, natural frequencies of intact and cracked beam models are calculated for different crack length and location combinations. In the inverse approach, which is the main concern of this paper, the natural frequency values obtained from experimental studies, finite element simulations and analytical solutions are used for crack identification via plots of rotational spring flexibilities against crack location. The estimated crack length and crack location values are tabulated with actual data. Three different beam models that have free-free, fixed-free and simple-simple boundary conditions are considered in the numerical analyses.

• 대한전자공학회논문지SP
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• 제39권2호
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• pp.56-68
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• 2002

최근 표준화가 진행중인 H.26L에서 사용되는 Universal Variable Length Coding(UVLC) 부호화 기법은 오류에 강인하며 역방향으로 복호가 가능하다는 장점 등으로 인해 H.26L의 모든 심볼 부호화에 사용되고 있으나, 이 방법은 기존 Huffman 부호화 기법에 비해 부호화 효율이 떨어지는 단점을 가지고 있다. 본 논문은 UVLC의 장점을 모두 살리면서 부호화 효율을 높이기 위해 부호화 요소의 통계적 특성에 따라 부호화 요소와 부호어간의 관계를 동적으로 재배정하는 새로운 UVLC 방법을 제안한다. 고정된 재배정 테이블을 사용하므로 부호어 재배정 관계에 대한 부가 정보를 보내지 않아도 되는 장점이 있다. 실험 결과, 제안된 방법을 사용할 경우 저 비트율에서 매우 효율적이라고 알려진 H.26L 부호화 방법을 최소한으로 변형하며 inter 프레임에서 최대 8%, intra 프레임에서 최대 5%의 비트 감소율을 추가로 얻을 수 있음을 확인하였다.

• 인터넷정보학회논문지
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• 제6권5호
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• pp.45-56
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• 2005

컴퓨터 네트워크의 확대 및 인터넷 이용의 급격한 증가에 따라 네트워크 서비스 품질의 보장과 네트워크의 관리가 어려울 뿐만 아니라 네트워크 보안의 취약성으로 인하여 해킹 및 정보유출 등의 위협에 노출되어 있다. 특히 시스템 침입의 보안 위협에 대한 능동적인 대처 및 침입 이후에 동일하거나 유사한 유형의 사건 발생에 대해 실시간에 대응하는 것이 중요하므로 침임 탐지 시스템에 대한 많은 연구가 진행되고 있다. 본 논문에서는 시스템 호출을 이용하여 이상 침입 탐지 시스템의 성능을 향상시키기 위해, 특징 선택과 가변 길이 데이터를 고정 길이 학습 패턴으로 변환 생성하는 문제를 해결하기 위한 사운덱스 알고리즘을 적용한 신경망 학습을 통하여 이상 침입 탐지의 연구를 하고자 한다. 즉, 가변 길이의 순차적인 시스템 호출 데이터를 사운덱스 알고리즘에 의한 고정 길이의 행위 패턴을 생성하여 역전파 알고리즘에 의해 신경망 학습을 수행하였다. 역전파 신경망 기법을 UNM의 Sendmail Data Set을 이용하여 시스템 호출의 이상 탐지에 적용하여 성능을 검증하였다.

• Smart Structures and Systems
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• 제21권2호
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• pp.163-170
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• 2018

The dynamic response of a finite length thermo-piezoelectric rod with variable material properties is investigated in the context of the fractional order theory of thermoelasticity. The rod is subjected to a moving heat source and fixed at both ends. The governing equations are formulated and then solved by means of Laplace transform together with its numerical inversion. The results of the non-dimensional temperature, displacement and stress in the rod are obtained and illustrated graphically. Meanwhile, the effects of the fractional order parameter, the velocity of heat source and the variable material properties on the variations of the considered variables are presented, and the results show that they significantly influence the variations of the considered variables.

• 품질경영학회지
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• 제40권2호
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• pp.186-198
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• 2012

Since Duncan(1956) first proposed an economic design of $\bar{X}$-control charts, most of the succeeding works on economic design of control charts assumed the exponential failure model like Duncan. Hu(1984), however, assumed a more versatile Weibull failure model to develop an economic design of $\bar{X}$-control charts and Banerjee and Rahim(1988) further improved Hu's design by changing the assumption of fixed-length sampling intervals to variable-length ones. In this article we follow the approach of Banerjee and Rahim(1988) but include a pair of warning limits inside the control limits in order to search for a failure without stopping the process when the sample mean falls between warning and control limits. The computational results indicate that the proposed model gives a lower cost than Banerjee and Rahim's model unless the early failure probability of a Weibull distribution is relatively large. The reduction in cost is shown to become larger as the cost of production loss outweighs the cost of searches for a failure.