• 한국전자파학회논문지
• /
• 제17권12호
• /
• pp.1172-1180
• /
• 2006

본 논문은 풀이 없는 지표면에서의 후방 산란 계수(backscattering coefficients)를 측정하고, 이 측정 결과를 이용하여 여러 표면 산란 모델들과 inversion 알고리즘의 성능을 비교, 분석하였다. 우선, R-밴드 주파수($1.7{\sim}2.0GHz$)에서 완전 편파 scatterometer를 이용하여 풀 층이 없는 지표면에 대해서 편파별로 후방 산란 계수를 측정하고, 동시에 수분 함유량과 표면 거칠기를 측정하였다. 그런 다음 측정된 지표면 변수들을 표면 산란 모델들에 입력하여 후방 산란 계수를 계산하고, 이 계산 결과를 측정 결과와 비교 분석하였다. 또한, inversion 알고리즘들을 적용하여 측정된 편파별 후방 산란 계수로부터 수분 함유량을 추출하고, 이 추출된 수분 함유량이 현장에서 측정한 수분 함유량과 잘 맞는지 여부를 확인하였다. 표면 산란 모델들 중에서 정확도가 높은 모델들을 제시하였으며, inversion 모델들의 계산 결과도 나타내었다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권4호
• /
• pp.1504-1526
• /
• 2018

For uplink multi-user massive MIMO systems, conventional minimum mean square error (MMSE) linear detection method achieves near-optimal performance when the number of antennas at base station is much larger than that of the single-antenna users. However, MMSE detection involves complicated matrix inversion, thus making it cumbersome to be implemented cost-effectively and rapidly. In this paper, we first summarize in detail the state-of-the-art simplified MMSE detection algorithms that circumvent the complicated matrix inversion and hence reduce the computation complexity from ${\mathcal{O}}(K^3)$ to ${\mathcal{O}}(K^2)$ or ${\mathcal{O}}(NK)$ with some certain performance sacrifice. Meanwhile, we divide the simplified algorithms into two categories, namely the matrix inversion approximation and the classical iterative linear equation solving methods, and make comparisons between them in terms of detection performance and computation complexity. In order to further optimize the detection performance of the existing detection algorithms, we propose more proper solutions to set the initial values and relaxation parameters, and present a new way of reconstructing the exact effective noise variance to accelerate the convergence speed. Analysis and simulation results verify that with the help of proper initial values and parameters, the simplified matrix inversion based detection algorithms can achieve detection performance quite close to that of the ideal matrix inversion based MMSE algorithm with only a small number of series expansions or iterations.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제17권3호
• /
• pp.425-437
• /
• 2017

For efficient hardware (HW) implementation of elliptic curve cryptography (ECC), various sub-modules for the underlying finite field operations should be implemented efficiently. Among these sub-modules, modular inversion (MI) requires the most computation; therefore, its performance might be a dominant factor of the overall performance of an ECC module. To determine the most efficient MI algorithm for an HW ECC module, we implement various classes of MI algorithms and analyze their performance. In contrast to the common belief in previous research, our results show that the right-shift binary inversion (RS) algorithm performs well when implemented in hardware. In addition, we present optimization methods to reduce the area overhead and improve the speed of the RS algorithm. By applying these methods, we propose a new RS-variant that is both fast and compact. The proposed MI module is more than twice as fast as the other two classes of MI: shifting Euclidean (SE) and left-shift binary inversion (LS) algorithms. It consumes only 15% more area and even 5% less area than SE and LS, respectively. Finally, we show that how our new method can be applied to optimize an HW ECC module.

• 지구물리와물리탐사
• /
• 제10권2호
• /
• pp.138-146
• /
• 2007

이 연구에서 복소 전기비저항을 이용한 2차원 IP 모델링 알고리듬과 이를 이용한 역산 알고리듬을 개발하였다. 복소 전기비저항을 이용한 IP 탐사기법은 크기인 전기비저항과 위상정보를 제공함으로써 지하의 수리지질학적인 특성 및 내부 공극수 종류 등 다양한 정보의 제공이 가능하여 활용성이 확대되고 있다. IP 탐사 모델링 및 역산 알고리듬은 기존의 전기비저항 모델링 및 역산 알고리듬을 복소 연산을 포함하도록 확장함으로써 개발되었다. IP 모델링은 유한요소법을 이용한 2.5차원 모델링 알고리듬을, 역산 알고리듬으로는 평활화 제한을 가한 감쇠 최소자승법을 이용하였다. 모델링의 검증에는 슐럼버저 배열에 대하여 3차원 층서모형에 수치필터링을 이용한 1차원 모델링 결과와 비교하였으며, 쌍극자 배열에 대하여 고립이상체 모형에 3차원 적분방정식 IP 모델링 알고리듬과 비교하여 그 타당성을 확인하였다. 역산의 타당성을 확인하기 위하여 전기비저항 및 위상 중 하나는 배경매질과 동일하고 다른 물성 하나만 차이를 가지는 모델에 대하여 역산 실험을 수행하였으며, 전기비저항 및 위상 이상체를 정확히 영상화하고 있음을 확인하였다. 역산의 실제 복잡한 지질모델에의 적용성을 확인하기 위해, 3차원 층서구조 내에 두 번째 층의 일부에 위상 이상체가 존재하는 모형을 설정하여 수치실험을 수행한 결과 전기비저항 단면에서는 이상체가 잘 확인되지 않으나, 위상 단면에서 그 이상체가 명확히 나타나는 것을 확인하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제3권2호
• /
• pp.121-135
• /
• 1999

This paper studies the problem of inverting minimal path sets to obtain minimal cut sets for complex system. We describe efficiency of inversion algorithm by the use of boolean algebra and we develop inclusion-exclusion algorithm and pivotal decomposition algorithm for reliability calculation of complex system. Several examples are illustrated and the computation speeds between the two algorithms are undertaken.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(II)
• /
• pp.1195-1198
• /
• 1987

This paper develops algorithms of element generation, addition, multiplication and inversion based on GF($2^m$). Since these algorithms are implemented by general purpose computer, these are more efficient than the conventional algorithms(Table Lookup, Euclid's Algorithm) in each operation. It is also implied that they can be applied to not only the normally defined elements but the arbitrarily defined ones for constructing multi-valued logic function.

• 자원환경지질
• /
• 제28권4호
• /
• pp.425-431
• /
• 1995

Genetic algorithms are so named because they are analogous to biological processes. The model parameters are coded in binary form. The algorithm then starts with a randomly chosen population of models called chromosomes. The second step is to evaluate the fitness values of these models, measured by a correlation between data and synthetic for a particular model. Then, the three genetic processes of selection, crossover, and mutation are performed upon the model in sequence. Genetic algorithms share the favorable characteristics of random Monte Carlo over local optimization methods in that they do not require linearizing assumptions nor the calculation of partial derivatives, are independent of the misfit criterion, and avoid numerical instabilities associated with matrix inversion. An additional advantage over converntional methods such as iterative least squares is that the sampling is global, rather than local, thereby reducing the tendency to become entrapped in local minima and avoiding the dependency on an assumed starting model.

• 한국통신학회논문지
• /
• 제35권3A호
• /
• pp.260-268
• /
• 2010

Channel inversion is one of the simplest techniques for multiuser downlink systems with single-antenna users. In this paper, we extend the regularized channel inversion technique developed for the single-antenna user case to multiuser multiple-input multiple-output (MIMO) channels with multiple-antenna users. We first employ the multiuser preprocessing to project the multiuser signals near the null space of the unintended users based on the MMSE criterion, and then the single-user preprocessing is applied to the decomposed MIMO interference channels. In order to reduce the complexity, we focus on non-iterative solutions for the multiuser transmit beamforming and use a linear receiver based on an MMSE criterion. Simulation results show that the proposed scheme outperforms existing joint iterative algorithms in most multiuser configurations.

• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
• /
• pp.130-134
• /
• 2007

Classical full waveform inversion for velocity estimation defines the objective function as the $l^2$ -norm of differences between the modeled and the observed wavefields. Although widely used, the results of this method have been less than satisfactory. A moderate improvement of this method is to define the objective function as the $l^2$ -norm of differences between the logarithms of the modeled and observed wavefields. In this paper we propose new objective functions of waveform inversion. They produce better results in sub-salt imaging than those of the classical and the logarithmic objective functions. One objective function defines the residual as the difference between $L^{th}$ power of the modeled wavefields and that of the observed wavefields. Another defines the residual as the difference between the integral of the $L^{th}$ power of the modeled wavefields and that of the observed wavefields. We apply these new objective functions to the synthetic SEG/EAGE salt model, and show that our new waveform inversion algorithms provide more accurate results than those of the classical and logarithmic waveform inversion methods.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1996년도 춘계학술대회 논문집
• /
• pp.419-423
• /
• 1996

These days, industrial robots are required to have high speed and high precision in doing various tasks. Recently, the adaptive control algorithms for those nonlinear robots have been developed. With spatial vector space, these adaptive algorithms including recursive implementation are simply described. Without sensing joint acceleration and computing the inversion of inertia matrix, these algorithms which include P.D. terms and feedforward terms have global tracking convergence. In this paper, the feasibility of the proposed control method is illustrated by applying to 2 DOF SCARA robot in DSP(Digital Signal Processing).