• Title/Summary/Keyword: weighted center

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Comparison of Two Meta-Analysis Methods: Inverse-Variance-Weighted Average and Weighted Sum of Z-Scores

  • Lee, Cue Hyunkyu;Cook, Seungho;Lee, Ji Sung;Han, Buhm
    • Genomics & Informatics
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    • v.14 no.4
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    • pp.173-180
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    • 2016
  • The meta-analysis has become a widely used tool for many applications in bioinformatics, including genome-wide association studies. A commonly used approach for meta-analysis is the fixed effects model approach, for which there are two popular methods: the inverse variance-weighted average method and weighted sum of z-scores method. Although previous studies have shown that the two methods perform similarly, their characteristics and their relationship have not been thoroughly investigated. In this paper, we investigate the optimal characteristics of the two methods and show the connection between the two methods. We demonstrate that the each method is optimized for a unique goal, which gives us insight into the optimal weights for the weighted sum of z-scores method. We examine the connection between the two methods both analytically and empirically and show that their resulting statistics become equivalent under certain assumptions. Finally, we apply both methods to the Wellcome Trust Case Control Consortium data and demonstrate that the two methods can give distinct results in certain study designs.

Case Study of the Immediate Gait Improvement in a Post-Stroke Gait Disturbance Patient Equipped with a Weighted Vest (중량조끼를 착용한 뇌졸중으로 인한 보행장애 환자의 즉각적인 보행 개선 효과 1례)

  • Kim, Cheol-hyun;Hong, Hae-jin;Lee, Sang-kwan
    • The Journal of Internal Korean Medicine
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    • v.37 no.5
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    • pp.763-769
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    • 2016
  • Objective: To confirm the immediate gait improvement in a post-stroke gait disturbance patient equipped with a weighted vest. Methods: We selected a patient who was able to walk without another’s help or with tools. The selected patient had an unstable gait because she had only started an independent gait within the past week, so we thought that a weighted vest could be very helpful for her. We first collected gait parameters using a treadmill gait analysis system while the patient walked on the treadmill without the weighted vest. After a 10-minute break, gait parameters were collected again while the patient walked on the treadmill while wearing the weighted vest. The gait parameters we collected included step length (cm), stance phase (%), swing phase (%), SW/ST, and gait line length (mm). For objective evaluation of gait improvement, we calculated the ratio of gait parameters of the right and left limbs. Results: The gait of the post-stroke patient was more symmetrical when wearing the weighted vest than without the weighted vest. Without the weighted vest, her step length ratio was 0.78, stance phase ratio was 0.88, swing phase ratio was 1.50, SW/ST ratio was 1.70, and gait line length ratio was 0.91. With the weighted vest, her step length ratio was 0.88, stance phase ratio was 0.90, swing phase ratio was 1.38, SW/ST ratio was 1.54, and gait line length ratio was 0.98. No side effects were observed due to the weighted vest.

Supratentorial Gangliocytoma Mimicking Extra-axial Tumor: A Report of Two Cases

  • Ho Sung Kim;Ho Kyu Lee;Ae Kyung Jeong;Ji Hoon Shin;Choong Gon Choi;Shin Kwang Khang
    • Korean Journal of Radiology
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    • v.2 no.2
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    • pp.108-112
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    • 2001
  • We report two cases of supratentorial gangliocytomas mimicking an extra-axial tumor. MR imaging indicated that the tumors were extra-axial, and meningiomas were thus initially diagnosed. Relative to gray matter, the tumors were hypointense on T1-weighted images and hyperintense on T2-weighted images. On contrast-enhanced T1-weighted images, homogeneous enhancement was observed, while CT scanning revealed calcification in one of the two cases.

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WEIGHTED COMPOSITION OPERATORS ON NACHBIN SPACES WITH OPERATOR-VALUED WEIGHTS

  • Klilou, Mohammed;Oubbi, Lahbib
    • Communications of the Korean Mathematical Society
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    • v.33 no.4
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    • pp.1125-1140
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    • 2018
  • Let A be a normed space, ${\mathcal{B}}(A)$ the algebra of all bounded operators on A, and V a family of strongly upper semicontinuous functions from a Hausdorff completely regular space X into ${\mathcal{B}}(A)$. In this paper, we investigate some properties of the weighted spaces CV (X, A) of all A-valued continuous functions f on X such that the mapping $x{\mapsto}v(x)(f(x))$ is bounded on X, for every $v{\in}V$, endowed with the topology generated by the seminorms ${\parallel}f{\parallel}v={\sup}\{{\parallel}v(x)(f(x)){\parallel},\;x{\in}X\}$. Our main purpose is to characterize continuous, bounded, and locally equicontinuous weighted composition operators between such spaces.

A study on improvement of the weighted median filter in low noise (저잡음하에서 WM 필터의 개선에 관한 연구)

  • 이용환;서민형;우상근;박장춘
    • Proceedings of the Korean Information Science Society Conference
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    • 1998.10c
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    • pp.467-468
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    • 1998
  • Impulsive noise appears as black and/or white spots in an image. It is usually caused by errors during the image acquisition or transmission through communication channels. This paper presents a study on the impulsive noise reduction filter of digital image. A much more effective method for removing impulse noise is weighted median filtering. But it loses some information by changing center value with no condition. We propose some new technique to change center value with some conditions. In this paper, the performance of conditional weighted median filter is compared to the commonly used median filter, mean filter, max/min filter, and weighted median filter. A quantitative comparison is performed on MSE (Mean Square Error), RMSE (Root Mean Square Error), and SNR (Signal to Noise Ratio). Proposed conditional weighted median filter can yield better performance than regular filters.

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Weighted Hadamard Transform Image Coding (하중 Hadamard 변환의 영상부호화)

  • Lee, Moon-Ho
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.24 no.2
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    • pp.301-308
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    • 1987
  • In this paper, we have defined the Weighted Hadamard Transform (WHT) and developed efficient algorithms for the fast computation of the WHT. The WHT is applied to digital image processing and compared with Hadamard Transform (HT). We have weighted at the center spatial frequency domains of the Hadamard Transform and transmitted a image and then center high frequencies are neglected at the receiving. The WHT of signal to noise ratio(SNR) and image quality are enhanced than the HT.

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A Note on the Population Center of Korea (인구중심의 변천에 관한 연구)

  • Yang, Jae Young;Lee, Nak Young
    • Journal of Applied Reliability
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    • v.15 no.3
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    • pp.192-196
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    • 2015
  • It is important to obtain the information of population center for establishing the balanced development policy of a nation. In this note, the population center of Korea is obtained using 2010 Census data and compared with the past population centers. The weighted average method is used for calculating the population center. The results of this note will be able to contribute in the regional population distribution policies.

Evaluation of the Image Blurring in the Fast Spin Echo Technique ccording to Variation of the ETL (고속스핀에코기법을 이용한 MRI검사에서 ETL 변화에 따른 영상 blurring의 평가)

  • Kwon, Soon-Yong;Lim, Woo-Taek;Kang, Chung-Hawn;Kim, Kyeong-Soo;Kim, Soon-Bae;Kim, Hyun-Soo
    • Korean Journal of Digital Imaging in Medicine
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    • v.15 no.2
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    • pp.55-61
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    • 2013
  • The purpose of this study is to evaluate image blurring according to variation of the ETL and propose the clinically appropriate ETL range. SIEMENS MAGNETOM Skyra 3.0T and 20 channel head coil were used for the study. MRI phantom was kept the lines horizontally to three direction(X,Y,Z) of the coil and T1, T2 weighted images that used the fast spin echo technique acquired. The ETL with increase of 10 was applied from 10 to 80. In addition, the ETL with increase of 1 was applied in the interval statistically significant differences occurred. And T1, T2 weighted images that used the conventional spin echo technique acquired to compare image blurring of the images that used the fast spin echo technique. The slope of lattice in the images was measured using Image J 1.47v program to evaluate image blurring. And image blurring was determined by the degree of the slope. The statistical significance of both techniques was evaluated by the Kruskal-Wallis test of the SPSS 17.0v. And the correlation of the ETL and image blurring was evaluated quantitatively by regression analysis. The slope of the T1, T2 weighted images that used fast spin echo technique decreased as contrasted with conventional spin echo technique. In the result of the Kruskal-Wallis test, the T1, T2 weighted images that used fast spin echo technique made a significant difference with conventional spin echo technique. Particularly, in the Tomhane' T2 test, the T1, T2 weighted images made a significant difference from ETL 22 and 31 respectively. In the result of the regression analysis, the R-squared of the T1, T2 weighted images are 0.762 and 0.793. It is difficult to apply the long ETL in the T1 weighted image caused by the short TR and multi-slices study. Therefore, clinical impact according to variation of the ETL is very slight in the T1 weighted images. But the application of the proper ETL is demanded in T2 weighted images using the fast spin echo technique in order to prevent image blurring.

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Adaptive Directional Filtering Techniques for Image Sequences (동영상을 위한 적응 방향성 필터링 기술)

  • 고성제
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.18 no.7
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    • pp.922-934
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    • 1993
  • In this paper, statistical properties of the spatiotemporal center weighted median(CWM) filter for image sequences are investigated. It is statistically shown that the CWM filter preserves image structures under motion at the expense of noise suppression. To improve the CWM filter, a filter which can be effectively used in image sequence processing, the adaptive directional center weighted median filter (ADCWM), is proposed. This filter utilizes a multistage filtering structure based on adaptive symmetric order statistic(ASOS) operators which produce a pall of order statistics symmetric about the median. The ASOS's are selected by using adaptive parameters adjusted by local image statistics. It is shown experimentally that the proposed filter can preserve image structures while attenuating noise without the use of motion estimation.

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Site Assessment Using Habitat Suitability Index for Manila Clam Ruditapes philippinarum in Geunso Bay Tidal Flats (서식지 적합지수를 이용한 근소만 갯벌 바지락(Ruditapes philippinarum)의 어장적지평가)

  • Choi, Yong-Hyeon;Hong, SokJin;Jeon, Seung-Ryul;Cho, Yoon-Sik
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.52 no.5
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    • pp.511-518
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    • 2019
  • Evaluating the habitat suitability of potential aquaculture sites for cultured species is critical to the sustainable use of tidal flats. This study evaluated the habitat suitability index (HSI) of 12 sites in a tidal flat aquaculture farm at Geunso Bay, Taean, in June 2016. The parameters used to model the suitability index were Growth (water temperature, chlorophyll ${\alpha}$, hydrodynamics), Survival (sediment-sand, mean size, air exposure), and Environment (DO, salinity). The HSI was calculated using weighted and No weighted geometric means. The results showed high habitat suitability at the bay's entrance (HIS; No weighted, 0.60-0.70; weighted, 0.60). Hydrodynamics, air exposure, sediment-sand and mean size are thought to have a significant impact on habitat selection by Manila clams Ruditapes philippinarum. This study explored the optimum habitat for Manila clams by calculating the HSI, providing basic data for tidal flat management.