• Kyungpook Mathematical Journal
• /
• 제55권2호
• /
• pp.301-311
• /
• 2015

In this paper, we present the error control techniques for the error correction methods (ECM) which is recently developed by P. Kim et al. [8, 9]. We formulate the local truncation error at each time and calculate the approximated solution using the solution and the formulated truncation error at previous time for achieving uniform error bound which enables a long time simulation. Numerical results show that the error controlled ECM provides a clue to have uniform error bound for well conditioned problems [1].

• Nuclear Engineering and Technology
• /
• 제16권1호
• /
• pp.21-28
• /
• 1984

수치확산을 포함한 truncation오차의 줄임은 수치해석의 중요한 과제가 되어왔다. Stream line방법이 교차수치 확산과 비확산형의 truncation 오차를 제거하기 위하여 고안되었다. 또한, stream line방법과 유한 차분법이 합쳐진 2단계 stream line방법이 비압축성 난류유동의 지배 방정식을 풀기 위하여 고안되었다. 이 방법은 유한 차분법과 비교되었으며, 두 방법 모두 실험자료와 비교되었다. 그리고, 두 방법의 truncation 오차를 비교하기 위하여 truncation 오차 분석이 행해졌다

• Structural Engineering and Mechanics
• /
• 제64권3호
• /
• pp.279-285
• /
• 2017

Modal expansion technique (MET) is a method to estimate the vibration fields of flexible structures by using eigenmodes of the structure and the signals of sensors. It is the useful method to estimate the vibration fields but has the truncation error since it only uses the limit number of the eigenmodes in the frequency of interest. Even though block-wise MET performed frequency block by block with different valid eigenmodes was developed, it still has the truncation error due to the absence of other eigenmodes. Thus, this paper suggested an improved block-wise modal expansion technique. The technique recovers the truncation errors in one frequency block by utilizing other eigenmodes existed in the other frequency blocks. It was applied for estimating the vibration fields of a cylindrical shell. The estimated results were compared to the vibration fields of the forced vibration analysis by using two indices: the root mean square error and parallelism between two vectors. These indices showed that the estimated vibration fields of the improved block-wise MET more accurately than those of the established METs. Especially, this method was outstanding for frequencies near the natural frequency of the highest eigenmode of each block. In other words, the suggested technique can estimate vibration fields more accurately by recovering the truncation errors of the established METs.

• Nuclear Engineering and Technology
• /
• 제44권7호
• /
• pp.755-766
• /
• 2012

A Binary Decision Diagram (BDD) is a graph-based data structure that calculates an exact top event probability (TEP). It has been a very difficult task to develop an efficient BDD algorithm that can solve a large problem since its memory consumption is very high. Recently, in order to solve a large reliability problem within limited computational resources, Jung presented an efficient method to maintain a small BDD size by a BDD truncation during a BDD calculation. In this paper, it is first identified that Jung's BDD truncation algorithm can be improved for a more practical use. Then, a more efficient truncation algorithm is proposed in this paper, which can generate truncated BDD with smaller size and approximate TEP with smaller truncation error. Empirical results showed this new algorithm uses slightly less running time and slightly more storage usage than Jung's algorithm. It was also found, that designing a truncation algorithm with ideal features for every possible fault tree is very difficult, if not impossible. The so-called ideal features of this paper would be that with the decrease of truncation limits, the size of truncated BDD converges to the size of exact BDD, but should never be larger than exact BDD.

• 한국항행학회논문지
• /
• 제15권5호
• /
• pp.850-856
• /
• 2011

오차 확산 방법은 디지털 하프토닝 방법 중 하나로 현재 처리하는 픽셀의 양자화 오차를 아직 처리하지 않은 주변 이웃 화소에 확산시켜 변환된 흑백 영상의 품질을 높이는 방법이다. 이러한 방법은 발생한 양자화 오차를 주변으로 분산하는 과정에서 부분적으로 오차의 합이 증가하거나 감소하는 경우가 발생하게 된다. 본 논문에서는 오차 확산의 대표적인 방법인 Floyd-Steinberg 방법과 Jarvis-Judice-Ninke의 방법, Stucki의 방법, Shiau-Fan의 방법을 분석하고 이에 대한 해결 방법을 제시한다.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1997년도 추계학술발표회논문집(1)
• /
• pp.79-84
• /
• 1997

동특성 분석 코드 시스템 PANBOX2는 시간에 대한 미분을 Implicit Euler 방법을 사용하여 근사한다. 이 경우 Local Truncation Error는 중성자속의 이차 미분에 비례한다. Time-Step-Doubling 기법을 이용하여 Local Truncation Error의 근사치를 구하고 이를 이용하여 Time Step Size를 조절해 주는 방법을 동특성 분석 코드 시스템 PANBOX2에 도입하였다. LRA와 NEACRP 제어봉 인출사고 검증문제에 대한 분석 결과, PANBOX2 시스템의 기존 방법에 비해 효과적으로 Time Step을 제어하였으며 보다 정확한 결과를 얻을 수 있었다.

• Investigative Magnetic Resonance Imaging
• /
• 제19권1호
• /
• pp.19-30
• /
• 2015

Purpose: A new compressed sensing technique by iterative truncation of small transformed coefficients (ITSC) is proposed for fast cardiac CINE MRI. Materials and Methods: The proposed reconstruction is composed of two processes: truncation of the small transformed coefficients in the r-f domain, and restoration of the measured data in the k-t domain. The two processes are sequentially applied iteratively until the reconstructed images converge, with the assumption that the cardiac CINE images are inherently sparse in the r-f domain. A novel sampling strategy to reduce the normalized mean square error of the reconstructed images is proposed. Results: The technique shows the least normalized mean square error among the four methods under comparison (zero filling, view sharing, k-t FOCUSS, and ITSC). Application of ITSC for multi-slice cardiac CINE imaging was tested with the number of slices of 2 to 8 in a single breath-hold, to demonstrate the clinical usefulness of the technique. Conclusion: Reconstructed images with the compression factors of 3-4 appear very close to the images without compression. Furthermore the proposed algorithm is computationally efficient and is stable without using matrix inversion during the reconstruction.

• 한국통신학회논문지
• /
• 제30권2A호
• /
• pp.129-136
• /
• 2005

지정된 비트 크기를 갖는 승산기 코어의 Verilog-HDL 모델을 생성하는 가변 정밀도 승산기 생성기 (VPM_Gen; Variable-Precision Multiplier Generator)에 대해 기술한다. 사용자의 필요에 따라 승수와 피승수의 비트 수를 8-비트${\sim}32$-비트 범위에서 1-비트 단위로 선택할 수 있으며, 승산결과는 $8-b{\sim}64-b$ 범위에서 2-비트 단위로 절사할 수 있도록 함으로써 총 3,455 가지 승산기 코어를 생성할 수 있다. 승산결과가 절사되는 경우, 절사되는 부분의 회로를 제거함으로써 게이트 수와 전력소모가 각각 최대 40%와 30% 감소되도록 하였으며, 이를 통해 효율적인 저전력 승산기 코어가 구현되도록 하였다. 또한, 절사 비트 수에 따른 적응 오차보상 방법을 적용함으로써 절사오차가 최소화되도록 하였다. VPM_Gen에 의해 생성되는 승산기 코어는 Xilinx FPGA 보드와 논리분석기를 통하여 그 기능을 검증하였다.

• ETRI Journal
• /
• 제31권1호
• /
• pp.42-50
• /
• 2009

A new method for simulating voltage and current distributions in transmission lines is described. It gives the time domain solution of the terminal voltage and current as well as their line distributions. This is achieved by treating voltage and current distributions as distributed state variables (DSVs) and turning the transmission line equation into an ordinary differential equation. Thus the transmission line is treated like other lumped dynamic components, such as capacitors. Using backward differentiation formulae for time discretization, the DSV transmission line component is converted to a simple time domain companion model, from which its local truncation error can be derived. As the voltage and current distributions get more complicated with time, a new piecewise exponential with controllable accuracy is invented. A segmentation algorithm is also devised so that the line is dynamically bisected to guarantee that the total piecewise exponential error is a small fraction of the local truncation error. Using this approach, the user can see the line voltage and current at any point and time freely without explicitly segmenting the line before starting the simulation.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2001년도 추계종합학술대회
• /
• pp.617-620
• /
• 2001

N-비트$\times$N-비트 승산에서 승산결과 2N-비트 중 상위 N-비트만을 출력하는 절사형(truncated) Booth 승산기의 절사오차 최소화를 위한 효율적인 오차보상 방법을 제안하였다. 제안된 방법을 적용하여 작은 칩 면적과 저전력 특성을 갖는 절사형 승산기를 설계하고 면적, 절사오차 등을 기존의 방식과 비교하였다. 제안된 절사형 Booth승산기는 승산결과의 하위 N-비트를 계산하는 회로를 생략하므로 절사되지 않은 일반 승산기에 비해 게이트 수가 약 35%~4o% 정도 감소한다. 본 논문에서 설계된 전사형 Booth 승산기는 기존의 고정 오차보상 방법을 적용한 경우에 비해 평균오차를 약 30%~40% 정도 줄일 수 있다.