• Structural Engineering and Mechanics
• /
• 제53권6호
• /
• pp.1127-1141
• /
• 2015

The optimum design of liquid column dampers in seismic vibration control considering system parameter uncertainty is usually performed by minimizing the unconditional response of a structure without any consideration to the variation of damper performance due to uncertainty. However, the system so designed may be sensitive to the variations of input system parameters due to uncertainty. The present study is concerned with robust design optimization (RDO) of liquid column vibration absorber (LCVA) considering random system parameters characterizing the primary structure and ground motion model. The RDO is obtained by minimizing the weighted sum of the mean value of the root mean square displacement of the primary structure as well as its standard deviation. A numerical study elucidates the importance of the RDO procedure for design of LCVA system by comparing the RDO results with the results obtained by the conventional stochastic structural optimization procedure and the unconditional response based optimization.

• 한국음향학회지
• /
• 제18권6호
• /
• pp.57-64
• /
• 1999

본 논문에서는 잡음이 포함된 음성의 시작점과 끝점을 효율적으로 검출할 수 있는 알고리듬에 대하여 연구하였다. 이를 위해, 웨이브렛 영역에서의 에너지 분포를 고려함으로써 잡음환경하에서도 음성을 검출할 수 있는 새로운 검출 파라미터를 제안하였다. 제안된 끝점검출 파라미터는 웨이브렛 영역에서 세 번째 coarsed 스케일의 표준편차와 가중치를 곱한 첫 번째 detailed 스케일의 표준편차의 합으로 정의하였다. 제안된 끝점검출기의 성능평가를 위해서 다양한 SNR에서 기존방식과 비교하여 시작점과 끝점의 정확도 실험을 수행하였고 HMM 음성인식시스템을 이용하여 인식실험도 수행하였다.

• 로봇학회논문지
• /
• 제6권3호
• /
• pp.292-300
• /
• 2011

Global positioning system (GPS) is widely used to measure the position of a vehicle. However, the accuracy of the GPS can be severely affected by surrounding environmental conditions. To deal with this problem, the GPS and odometry data can be combined using an extended Kalman filter. For stable navigation of an outdoor mobile robot using the GPS, this paper proposes two methods to evaluate the reliability of the GPS data. The first method is to calculate the standard deviation of the GPS data and reflect it to deal with the uncertainty of the GPS data. The second method is to match the GPS data to the traversability map which can be obtained by classifying outdoor terrain data. By matching of the GPS data with the traversability map, we can determine whether to use the GPS data or not. The experimental results show that the proposed methods can enhance the performance of the GPS-based outdoor localization.

• ETRI Journal
• /
• 제36권4호
• /
• pp.617-624
• /
• 2014

Through-silicon via (TSV) technology provides much of the benefits seen in advanced packaging, such as three-dimensional integrated circuits and 3D packaging, with shorter interconnection paths for homo- and heterogeneous device integration. In TSV, a destructive cross-sectional analysis of an image from a scanning electron microscope is the most frequently used method for quality control purposes. We propose a quantitative evaluation method for TSV etch profiles whereby we consider sidewall angle, curvature profile, undercut, and scallop. A weighted sum of the four evaluated parameters, nominally total score (TS), is suggested for the numerical evaluation of an individual TSV profile. Uniformity, defined by the ratio of the standard deviation and average of the parameters that comprise TS, is suggested for the evaluation of wafer-to-wafer variation in volume manufacturing.

• 품질경영학회지
• /
• 제26권1호
• /
• pp.108-125
• /
• 1998

The EWMA(Exponentially Weighted Moving Average) has recently received a great deal of attention in the quality control literature as a process monitoring tool on the shop floor of manufacturing industires, since it is easy to plot, to interpret, and its control limits are easy to obtain. Most a, pp.ications of the EWMA for process monitoring have concentrated on the problem of detecting shifts of a process mean and a process standard deviation with ARL(Average Run Length) properties. But there may be the necessity of controlling linearity on product quality such as the correlation coefficient to the process operator. Control managers may want to protect the increase of a process correlation coefficient value, such as 0, between two variables of interest. However, there are few studies concerned on this part. Therefore, we propose EWMA models for a process correlation coefficient using two transformed statistics, T-statistic and (Fisher's) Z-statistic. We also present some results of simulation by SAS/IML and compare two models.

• 한국터널지하공간학회 논문집
• /
• 제24권1호
• /
• pp.1-13
• /
• 2022

본 연구에서는 기존에 개발된 개착식 철도 터널의 지진취약도 모델들을 가중 조합하여 새로운 모델을 제시하고 제시한 모델의 적정성을 평가하였다. 지진취약도 함수의 형태는 최대지반가속도의 대수정규분포형태로, 누적확률분포로 표현된다. 독립적으로 개발된 각 모델을 선형 가중 조합하는 것으로 모델의 불확실성을 줄일 수 있기에 4개의 모델에 대하여 25%씩 동등하게 선형가중을 부여하였다. 조합된 지진취약도 곡선에 최대 지반가속도에 대한 피해발생확률을 이용하여 지진취약도 곡선의 중앙값과 표준편차를 결정하여 새로운 지진취약도 함수를 개발하였다. 개발된 지진취약도 함수의 적합성을 평가하기 위하여 다양한 터널의 지진취약도 곡선과 비교 분석을 진행하였다. 개발된 곡선은 상대적으로 지진피해에 안전한 굴착식 터널의 지진취약도 함수와 비슷한 취약도를 갖는 것으로 나타나는데, 대상 터널은 국내 고속철도 개착식 터널로 높은 내진설계 기준에 의해 기인하는 것으로 판단된다.

• 한국정보통신학회논문지
• /
• 제21권11호
• /
• pp.2029-2036
• /
• 2017

현재, 디지털 시대의 급속 발전과 함께 멀티미디어 서비스에 대한 수요가 증가되고 있다. 영상 데이터는 다양한 잡음에 의해 훼손되며, 주로 AWGN, salt and pepper 잡음, 이 두 잡음이 혼합된 복합잡음 등이 대표적이다. 따라서, 본 논문에서는 잡음 판단을 통해 AWGN 및 salt and pepper 잡음으로 분류하여 처리한다. AWGN인 경우, 공간 가중치 필터 및 화소 변화 가중치 필터의 출력을 합성하여 처리하며, 국부 마스크의 표준편차에 따라 합성 가중치를 다르게 적용한다. salt and pepper 잡음인 경우, 3차원 스플라인 보간법 및 국부 히스토그램 가중치 필터를 합성하여 처리하며, 국부 마스크의 salt and pepper 잡음 밀도에 따라 합성 가중치를 다르게 적용하여 처리하는 다중 영상복원 필터 알고리즘을 제안하였다.

• Journal of Yeungnam Medical Science
• /
• 제36권3호
• /
• pp.231-240
• /
• 2019

Background: We sought to determine the value of combining diffusion-weighted (DW) and perfusion-weighted (PW) sequences with a conventional magnetic resonance (MR) sequence to assess solid components of borderline ovarian tumors (BOTs) and stage I carcinomas. Methods: Conventional, DW, and PW sequences in the tumor imaging studies of 70 patients (BOTs, n=38; stage I carcinomas, n=32) who underwent surgery with pathologic correlation were assessed. Two independent radiologists calculated the parameters apparent diffusion coefficient (ADC), $K^{trans}$ (vessel permeability), and $V_e$ (cell density) for the solid components. The distribution on conventional MR sequence and mean, standard deviation, and 95% confidence interval of each DW and PW parameter were calculated. The inter-observer agreement among the two radiologists was assessed. Area under the receiver operating characteristic curve (AUC) and multivariate logistic regression were performed to compare the effectiveness of DW and PW sequences for average values and to characterize the diagnostic performance of combined DW and PW sequences. Results: There were excellent agreements for DW and PW parameters between radiologists. The distributions of ADC, $K^{trans}$, and $V_e$ values were significantly different between BOTs and stage I carcinomas, yielding AUCs of 0.58 and 0.68, 0.78 and 0.82, and 0.70 and 0.72, respectively, with ADC yielding the lowest diagnostic performance. The AUCs of the DW, PW, and combined PW and DW sequences were $0.71{\pm}0.05$, $0.80{\pm}0.05$, and $0.85{\pm}0.05$, respectively. Conclusion: Combining PW and DW sequences to a conventional sequence potentially improves the diagnostic accuracy in the differentiation of BOTs and stage I carcinomas.

• 한국농공학회논문집
• /
• 제61권1호
• /
• pp.131-144
• /
• 2019

The purpose of study was to determine the hygrophyte index of each plant(HIP) considering the moisture environment condition (MEC) of the native plants on the downstream slope of the fill dam and evaluate its applicability which to develop a method to search for leaks and saturated zones of the fill dam for status evaluation of precision safety diagnosis. The HIP was weighted average and consisted of 19 ranks. The weighted average was calculated according to the following three procedures: First, the linear assumption was made according to the actual habitat environmental conditions, the second one was weighted to 10% of the optimal habitat condition, and finally the average value of the distribution range values. The Hygrophyte index of vegetation at each plot (HIV) was obtained from the Sinheung reservoir (Yesan-gun, Chungcheongnam-do) using the results of vegetation survey of the Sinheung reservoir with precision safety diagnosis and suggested the use of the hygrophyte index of the cultivated vegetation. The average HIP range of plant species that emerged in 50 survey sites on the downstream slope of the Sinheung reservoir is 2.99 to 3.56. The coefficient of variation showed a large difference depending on the appearance of the leakage indicator plant(LIP) species. The range of HIV is 2.80 to 4.26, the mean value is 3.37, standard deviation is 0.37 and the coefficient of variation is 9.7%. As a result, the value of the coefficient of variation showed a large difference depending on the appearance of the plant species.

• Investigative Magnetic Resonance Imaging
• /
• 제25권2호
• /
• pp.118-128
• /
• 2021

Purpose: To investigate the value of MR textural analysis, including use of diffusion-weighted imaging (DWI) to differentiate malignant from benign soft-tissue tumors on 3T MRI. Materials and Methods: We enrolled 69 patients (25 men, 44 women, ages 18 to 84 years) with pathologically confirmed soft-tissue tumors (29 benign, 40 malignant) who underwent pre-treatment 3T-MRI. We calculated MR texture, including mean, standard deviation (SD), skewness, kurtosis, mean of positive pixels (MPP), and entropy, according to different spatial-scale factors (SSF, 0, 2, 4, 6) on axial T1- and T2-weighted images (T1WI, T2WI), contrast-enhanced T1WI (CE-T1WI), high b-value DWI (800 sec/mm²), and apparent diffusion coefficient (ADC) map. We used the Mann-Whitney U test, logistic regression, and area under the receiver operating characteristic curve (AUC) for statistical analysis. Results: Malignant soft-tissue tumors had significantly lower mean values of DWI, ADC, T2WI and CE-T1WI, MPP of ADC, and CE-T1WI, but significantly higher kurtosis of DWI, T1WI, and CE-T1WI, and entropy of DWI, ADC, and T2WI than did benign tumors (P < 0.050). In multivariate logistic regression, the mean ADC value (SSF, 6) and kurtosis of CE-T1WI (SSF, 4) were independently associated with malignancy (P ≤ 0.009). A multivariate model of MR features worked well for diagnosis of malignant soft-tissue tumors (AUC, 0.909). Conclusion: Accurate diagnosis could be obtained using MR textural analysis with DWI and CE-T1WI in differentiating benign from malignant soft-tissue tumors.