• 한국통신학회논문지
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• 제27권5C호
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• pp.486-495
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• 2002

본 논문에서는 프레임 기반 패킷 전송 스케쥴링을 위한 지연 감축 방안을 제안한다. ATM과 같은 초고속 통신망은 사용자에게 대역폭과 패킷 지연과 같은 성능을 보장하여야 한다. 스케쥴링 방법에 있어 프레임 기반 구조는 사용자에게 요구되는 대역폭의 지원과 간단한 레이트-제어 방법을 제공하지만 나쁜 지연 특성을 가지게 된다. 본 논문에서 제안한 지연 감축 방법은 HRR (Hierarchical Round-Robin)과 같은 계층적 프레임 구조를 사용하지만 지연 특성을 좋게 하기 위해 고정된 우선순위를 갖는 라운드 로빈 방식을 사용하지 않고, 동적으로 우선순위를 변화시킴으로써 광대역과 협대역 연결간의 지연에 있어서의 불평등을 해소하였다. 해석적 비교 및 모의실험 결과 제안된 HFIFO 방법이 기존의 HRR과 같은 프레임 구조의 장점을 그대로 따르면서, 연결간 공정한 지연품질 제공하며 전체 지연 값을 줄일 수 있음을 알 수 있었다.

• Molecules and Cells
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• 제21권1호
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• pp.63-75
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• 2006

The 5′-region of Potato virus X (PVX) RNA, which contains an AC-rich, single-stranded region and stem-loop structure 1 (SL1), affects RNA replication and assembly. Using Systemic Evolution of Ligands by EXponential enrichment (SELEX) and the electrophoretic mobility shift assay, we demonstrate that SL1 interacts specifically with tobacco protoplast protein extracts (S100). The 36 nucleotides that correspond to the top region of SL1, which comprises stem C, loop C, stem D, and the tetra loop (TL), were randomized and bound to the S100. Remarkably, the wild-type (wt) sequence was selected in the second round, and the number of wt sequences increased as selection proceeded. All of the selected clones from the fifth round contained the wt sequence. Secondary structure predictions (mFOLD) of the recovered sequences revealed relatively stable stem-loop structures that resembled SL1, although the nucleotide sequences therein were different. Moreover, many of the clones selected in the fourth round conserved the TL and C-C mismatch, which suggests the importance of these elements in host protein binding. The SELEX clone that closely resembled the wt SL1 structure with the TL and C-C mismatch was able to replicate and cause systemic symptoms in plants, while most of the other winners replicated poorly only on inoculated leaves. The RNA replication level on protoplasts was also similarly affected. Taken together, these results indicate that the SL1 of PVX interacts with host protein(s) that play important roles related to virus replication.

• 소성∙가공
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• 제7권5호
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• pp.496-504
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• 1998

The eccentric extrusion and bending process for the forming of the curved rectangular hollow tube is newly developed. Generally the bending process of hollow tube is the secondary process followed by the extrusion process of the hollow tube from the round billet. So many defects such as wrinkling and the difference of wall thickness can be happened during the secondary bending process. In order to avoid the defects the new process named as "the eccentric extrusion and bending process" is suggested and applied to the U-bending of rectangular hollow tube. In this paper the kinematically admissible velocity field between the dies surface and the internal plug boundary surface s developed for the curving velocity. By the using of this curving velocity field the curvature of extruded products can be calculated with the parameters such as eccentricity dies length friction constant aspect ratio.

• 대한기계학회논문집A
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• 제28권6호
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• pp.791-798
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• 2004

Fatigue crack initiation lives of round cylindrical notch specimen were investigated. Firstly, local strain approximation methods, such as the modified incremental Neuber's rule and the modified incremental Glinka's equivalent strain energy density(ESED) rule, were used to get multiaxial stress and strain state components at the notch tip. Based on the history of local stress and strain, multiaxial fatigue models were used to obtain fatigue crack initiation lives. Because the solution of Neuber's rule and Glinka's ESED rule make the upper and lower bound of local strain approximations, fatigue crack initiation lives are expected to place between life predictions by two local strain approximations. Experimental data were compared with the fatigue crack initiation life prediction results.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.21-26
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• 2003

The well-conditioned observer in a stochastic system is designed so that the observer is less sensitive to the ill-conditioning factors in transient and steady-state observer performance. These factors include not only deterministic issues such as unknown initial estimation error, round-off error, modeling error and sensing bias, but also stochastic issues such as disturbance and sensor noise. In deterministic perspectives, a small value in the L$_2$ norm condition number of the observer eigenvector matrix guarantees robust estimation performance to the deterministic issues and its upper bound can be minimized by reducing the observer gain and increasing the decay rate. Both deterministic and stochastic issues are considered as a weighted sum with a LMI (Linear Matrix Inequality) formulation. The gain in the well-conditioned observer is optimally chosen by the optimization technique. Simulation examples are given to evaluate the estimation performance of the proposed observer.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.210-213
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• 1998

A kinematically admissible velocity field is developed for the analysis of twisting of extruded products. The twisting of extruded product is caused by the linearly increased rotational velocity from the center on the cross-section of the workpiece at the die exit. In the analysis, the rotational velocity in angular direction is assumed by the multiplication of radial distance and angular velocity. The angular velocity is zero at the die entrance and is increased linearly by axial distance from die entrance. The increase rate of angular velocity is determined by the minimization of plastic work. The results of the analysis show that the angular velocity of the extruded product increase with the die twisting angle and the aspect ratio of product and friction condition and reduction area and show that angular velocity increases with the decreases in die length.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.130-135
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• 1997

A kinematically admissible velocity field is developed for the analysis of twisting of extruded products. The twisting of extruded product is caused by the linearly increased rotational velocity from the center on the cross-section of the workpiece at the die exit. In the analysis, the rotational velocity in angular direction is assumed by the multiplication of radial distance and angular velocity. The angular velocity is zero at the die entrance and is increased linearly by longitudinal distance from die entrance. The increase rate of angular velocity is determined by the minimization of plastic work. The results of the analysis show that the angular velocity of the extruded product changes with the aspect ratio of product and increases with the decreases in die length and in eccentricity of gravity center of the cross-section of workpiece at die entrance from that of the cross-section at the die exit.

• 한국경영과학회지
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• 제27권4호
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• pp.1-10
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• 2002

The ring routing and wavelength assignment problem arose in the planning of optical communication networks which use WDM rings. Traffic demands are given for each pair of nodes in an ring : each demand must be routed one of the two possible connections round the ring and the wavelength assignments must be made so that there are no conflicts : that is. no two connections whose routes share a link can be assigned the same wavelength along that link. The objective is to minimize the number of used wavelengths. We propose the local optimal routing for the problem and show that there always exists an optimal solution satisfying it. Furthermore we suggest a new lower bound for the problem and show that it is very efficient for the worst case example.

• 전자공학회논문지B
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• 제30B권6호
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• pp.49-58
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• 1993

Extended reduced difference pyramid (ERDP) is proposed for lossless progressive image transmission, which is based on a new transform called rounded-transform(RT). The RT is a nonlinear and reversible transform of integers into integers utilizing two kinds of the rounding operations such as round up and down. The ERDP can be obtained from an N-poing RT or a series of RTs of both. For the performance evaluation, the entropy of the difference images to be transmitted is used as a lower bound transmission rate. Two examples of the ERDP can be easily shown, which is more effective in the entropy than the ordinary RDP.

• 한국산림과학회지
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• 제90권3호
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• pp.373-379
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• 2001

본 연구는 UR농산물협상에서 우리 나라가 약속한 시장개방(市場開放)에 대한 이행실적(履行實績)을 평가하고 UR에 의한 시장개방이 국내 주요 단기소득임산물 시장에 미친 영향(影響)을 분석하였다. WTO농업협정의 이행실적 등은 관련자료 및 통계치를 이용하여 분석하였고, UR이후 수입개방이 밤, 대추, 잣, 호도, 표고시장에 미친 영향은 선행연구의 수요(需要) 및 공급탄성치(供給彈性値)와 UR이후의 수입량, 생산량 소비량 등의 자료를 이용하여 추정(推定)하였다. 1995년부터 1999년까지 5년동안 관세할당제도(關稅割當制度)에 의한 밤, 잣, 대추의 수입물량은 우리나라가 약속한 최소시장접근(最小市場接近) 물량(物量)을 초과하지 않았다. 현재 단기소득임산물의 실행관세율(實行關稅率)도 양허관세율(讓許關稅率)에 비해 상당히 낮으며 이러한 관계는 2004년까지 유지될 것이다. UR이후 단기소득임산물의 수입증가로 잠재적(潛在的) 국내가격(國內價格)이 하락되었고 이에 따라 소비지출액(消費支出額)이 감소되고 소비자잉여(消費者剩餘)가 증가된 것으로 추정되었다. 그러나 단기소득임산물의 수업증가로 인해 생산량이 큰 폭 감소된 것으로 추정되었으며 생산에 미친 부정적(否定的)연 효과(效果)가 소비에 미친 긍정적(肯定的)인 효과(效果)를 상회(上廻)한 것으로 추정되었다. 단기소득임산물은 UR의 결과 낮은 관세율로 수출시장에 접근할 수 있었음에도 불구하고 대부분의 수출(輸出)이 감소(減少)되었다.