• 한국통신학회논문지
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• 제34권4C호
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• pp.414-423
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• 2009

본 논문은 최대 전송률에 가까운 성능을 보이는 선형 preceding 기법을 제안한다. MMSE preceding은 ZF preceding 방식보다 우수한 평균 자승 오차 성능을 가진다. 반면 MMSE preceding 방식의 전송률은 낮은 SNR 범위에서는 ZF 방식에 비해 개선된 성능을 보여주지만 높은 SNR에서는 오히려 성능 열화현상을 보인다. 이와 같은 사실에 착안하여 본 논문에서는 최대 전송률에 근접하는 선형 preceding 기법을 제안한다. 제안된 방식은 ZF precoding방식에서 사용되는 역행렬 연산을 전송율이 최대화될 수 있도록 정규화하는 방식이고 이를 위한 간단한 수치 알고리즘이 제안된다. 또한 그 과정에서 낮은 복잡도를 가지는 간단한 전력 재할당에 의한 정규화 방식이 제안된다. 시뮬레이션과 성능분석을 통해 제안된 방식이 모든 SNR 범위에서 기존의 ZF preceding 방식과 MMSE preceding방식보다 높은 전송률을 가짐을 보인다. 또한 제안된 방식은 채널 추정 오차가 존재하는 경우에도 기존의 선형 preceding 방식들과 비교하여 성능 이득을 유지하면서 채널 추정 오차에 강인함을 가진다.

• Investigative Magnetic Resonance Imaging
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• 제9권1호
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• pp.36-42
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• 2005

목적 : 위상 배열(phased array) 코일의 sensitivity profile을 추정하는 알고리즘을 제시하고, 이로부터 위상 배열 코일 영상에서 나타나는 밝기 비균등성 문제를 해결하고자 한다. 대상 및 방법 : 코일의 sensitivity profile을 추정하기 위해, 우선 그 영상을 여러 각도에 대해 회전을 시켜가면서 projection 데이터를 얻는다. 영상의 해부학적인 구조, 즉 고주파 성분을 제거하기 위해, 앞에서 구한 projection 데이터에 적절한 curve fitting을 적용하여, projection profile을 부드럽게 변하는 곡선으로 만든다. Fitting된 projection profile에 filtered back projection 알고리즘을 적용하면, 원하는 코일의 sensitivity profile을 얻을 수 있다. 추정된 코일의 sensitivity profile 정보를 이용하여 획득한 위상 배열 코일 영상의 밝기를 균등화시킨다. 제안된 알고리즘은 각각, 8채널 및 4채널 위상 배열 코일을 사용하여 얻은 phantom과 사람 뇌 영상에 대해 적용해 봤다. 결과 : 알고리즘의 성능을 측정하기 위해, 본 알고리즘으로부터 얻어진 결과와 단순히 위상 배열코일 영상에 sum-of-square를 취하여 얻어진 결과의 밝기 균등성을 서로 비교해 보았다. 이때, 본 알고리즘으로부터 얻어진 영상의 밝기 균등성이 sum-of-square의 경우보다 더 높음을 확인할 수 있었다. 정량적으로는 밝기 변화량이 제안한 알고리즘에 의해 $13.1\%$에서 $6.1\%$로 감소되었다. 결론 : 제안한 알고리즘은 위상 배열 코일로부터 얻어진 영상의 밝기 비균등성을 효과적으로 보정할 수 있었다.

• Communications for Statistical Applications and Methods
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• 제31권3호
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• pp.349-363
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• 2024

Compositional data refers to data where the sum of the values of the components is a constant, hence the sample space is defined as a simplex making it impossible to apply statistical methods developed in the usual Euclidean vector space. A natural approach to overcome this restriction is to consider an appropriate transformation which moves the sample space onto the Euclidean space, and log-ratio typed transformations, such as the additive log-ratio (ALR), the centered log-ratio (CLR) and the isometric log-ratio (ILR) transformations, have been mostly conducted. However, in scenarios with sparsity, where certain components take on exact zero values, these log-ratio type transformations may not be effective. In this work, we mainly suggest an alternative transformation, that is the square-root transformation which moves the original sample space onto the directional space. We compare the square-root transformation with the log-ratio typed transformation by the simulation study and the real data example. In the real data example, we applied both types of transformations to the USG% data obtained from NBA, and used a density based clustering method, DBSCAN (density-based spatial clustering of applications with noise), to show the result.

• 한국수자원학회논문집
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• 제33권S1호
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• pp.3-10
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• 2000

A newly developed heuristic algorithm, Harmony Search, is applied to the parameter calibration problem of the nonlinear Muskingum model. The Harmony Search could, mimicking the improvisation of music player, find better parameter values for in the nonlinear Muskingum model than five other methods including another heuristic method, genetic algorithm, in the aspect of SSQ(the sum of the square of the deviations between the observed and routed outflows) as well as in the aspects of SAD(the sum of the absolute value of the deviations), DPO(deviations of peak of routed and actual flows) and DPOT(deviatios of peak time of routed and actual outflow). Harmony Search also has the advantage that it does not require the process of asuming the initial values of desing parameters. The sensitivity analysis of Harmony Memory Considering Rate showed that relatively large values of Harmony Memory Considering Rate makes the Harmony Search converge to a better solution.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2000년도 학술발표회 논문집
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• pp.3-10
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• 2000

A newly developed heuristic algorithm, Harmony Search, is applied to the parameter calibration problem of the nonlinear Muskingum model. The Harmony Search could, mimicking the improvisation of music players, find better parameter values for in the nonlinear Muskingum model than five other methods including another heuristic method, genetic algorithm, in the aspect of SSQ (the sum of the square of the deviations between the observed and routed outflows) as well as in the aspects of SAD (the sum of the absolute value of the deviations), DPO (deviations of peak of routed and actual flows) and DPOT (deviations of peak time of rented and actual outflow). Harmony Search also has the advantage that it does not require the process of assuming the initial values of design parameters. The sensitivity analysis of Harmony Memory Considering Rate showed that relatively large values of Harmony Memory Considering Rate makes the Harmony Search converse to a better solution.

• Kyungpook Mathematical Journal
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• 제59권2호
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• pp.335-340
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• 2019

The energy of a graph G is the sum of the absolute values of the eigenvalues of the adjacency matrix of G. Some variants of energy can also be found in the literature, in which the energy is defined for the Laplacian matrix, Distance matrix, Commonneighbourhood matrix or Seidel matrix. The Seidel matrix of the graph G is the square matrix in which $ij^{th}$ entry is -1 or 1, if the vertices $v_i$ and $v_j$ are adjacent or non-adjacent respectively, and is 0, if $v_i=v_j$. The Seidel energy of G is the sum of the absolute values of the eigenvalues of its Seidel matrix. We present here some families of pairs of graphs whose Seidel matrices have different eigenvalues, but who have the same Seidel energies.

• 반도체디스플레이기술학회지
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• 제8권4호
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• pp.95-100
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• 2009

This paper presents an efficient disparity matching, using sum of absolute difference (SAD) and dynamic programming (DP) algorithm. This algorithm makes use of one of area-based algorithm which is the absolute sum of the pixel difference corresponding to the window size. We use the information of the right eye brightness (B) and the left eye brightness to get an best matching results and apply the results to the left eye image using the window go by the brightness of the right eye image. This is that we can control the brightness. The major feature of this algorithm called SAD+DP+B is that although Root Mean Square (RMS) performance is slightly less than SAD+DP, due to comparing original image, its visual performance is increased drastically for matching the disparity map on account of its matching compared to SAD+DP. The simulation results demonstrate that the visual performance can be increased and the RMS is competitive with or slightly higher than SAD+DP.

• 대한수학회지
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• 제48권2호
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• pp.267-288
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• 2011

In this paper, we construct eight infinite families of ternary linear codes associated with double cosets with respect to certain maximal parabolic subgroup of the special orthogonal group $SO^-$(2n, q). Here q is a power of three. Then we obtain four infinite families of recursive formulas for power moments of Kloosterman sums with square arguments and four infinite families of recursive formulas for even power moments of those in terms of the frequencies of weights in the codes. This is done via Pless power moment identity and by utilizing the explicit expressions of exponential sums over those double cosets related to the evaluations of "Gauss sums" for the orthogonal groups $O^-$(2n, q).

• Advances in concrete construction
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• 제3권3호
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• pp.161-185
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• 2015

FRP confining is a widely used method for seismic retrofitting of concrete columns. Several studies investigated the stress-strain behavior of FRP confined concrete prisms with square and rectangular sections both experimentally and analytically. In some studies, the monotonic stress-strain behavior of confined concrete was investigated and compressive strength models were developed. To study the reliability of these models, thorough statistical tests are required. This paper aims to investigate the reliability of the presented models using statistical tests including t-test, wilcoxon rank sum test, wilcoxon signed rank test and sign test with a level of significance of 5%. Wilk Shapiro test was also employed to evaluate the normality of the data distribution. The results were compared for different cross section and confinement types. To see the accuracy of the models when there were no significant differences between the results, the coefficient of confidence was used.

• Advances in aircraft and spacecraft science
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• 제3권1호
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• pp.45-59
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• 2016

In this paper, the condensation method which is based on the Rayleigh-Ritz method, is described for the free vibration analysis of axially loaded slightly curved beams subject to partial axial restraints. If the longitudinal inertia is neglected, some of the Rayleigh-Ritz minimization equations are independent of the frequency. These equations can be used to formulate a relationship between the weighting coefficients associated with the lateral and longitudinal displacements, which leads to "connection coefficient matrix". Once this matrix is formed, it is then substituted into the remaining Rayleigh-Ritz equations to obtain an eigenvalue equation with a reduced matrix size. This method has been applied to simply supported and partially clamped beams with three different shapes of imperfection. The results indicate that for small imperfections resembling the fundamental vibration mode, the sum of the square of the fundamental natural and a non-dimensional axial load ratio normalized with respect to the fundamental critical load is approximately proportional to the square of the central displacement.