• 제어로봇시스템학회논문지
• /
• 제7권4호
• /
• pp.304-308
• /
• 2001

The increase of video data makes the demand of efficient retrieval, storing, and browsing technologies necessary. In this paper, a video segmentation method (scene change detection method, or shot boundary detection method) for the development of such systems is proposed. For abrupt cut detection, inter-frame similarities are computed using luminance and edge histograms and a cut is declared when the similarities are under th predetermined threshold values. A gradual scene change detection is based on the similarities between the current frame and the previous shot boundary frame. A correlation method is used to obtain universal threshold values, which are applied to various video data. Experimental results show that propose method provides 90% precision and 98% recall rates for abrupt cut, and 59% precision and 79% recall rates for gradual change.

• Communications for Statistical Applications and Methods
• /
• 제18권6호
• /
• pp.751-759
• /
• 2011

The method of generalized estimating equations(GEE) is widely used in the analysis of a correlated dataset that consists of repeatedly observed responses within subjects. The GEE uses a quasi-likelihood equations to find the parameter estimates without assuming a specific distribution for the correlated responses. In this paper we study the importance of specifying the working correlation structure appropriately in fitting GEE for correlated counts data. We investigate the empirical coverages of confidence intervals for the regression coefficients according to four kinds of working correlations where one structure should be specified by the users. The confidence intervals are computed based on the asymptotic normality and the sandwich variance estimator.

• 대한기계학회논문집B
• /
• 제29권7호
• /
• pp.837-845
• /
• 2005

In this paper, an investigation on high-Schmidt number (Sc=1670) mass transfer in turbulent flow around a rotating circular cylinder is carried out by Direct Numerical Simulation. The concentration field is computed for three different values of low Reynolds number, namely 161, 348 and 623 based on the cylinder radius and friction velocity. Statistical study reveals that the thickness of Nernst diffusive layer is very small compared with that of viscous sub-layer in the case of high Sc mass transfer. Strong correlation of concentration field with streamwise and vertical velocity components is observed. However, that is not the case with the spanwise velocity component. Instantaneous concentration visualization reveals that the length scale of concentration fluctuation typically decreases as Reynolds number increases. Statistical correlation between Sherwood number and Reynolds number is consistent with other experiments currently available.

• 대한전자공학회논문지TC
• /
• 제48권11호
• /
• pp.83-88
• /
• 2011

FDTD 수치해석법을 이용하여 모드가 변화하는 레버버레이션 챔버(RC) 내의 관측 평면내에서 파수 영역에서의 필드값의 계산이 가능하다. 이 필드 값은 RC 내의 모든 여기되는 모드의 방향성을 나타내어 준다. 스터링 효과를 계산하기 위하여 코릴레이션 계수를 구하였으며, 이를 3개의 상이한 스터러의 구조에 적용하여 그 결과를 상호 비교하였다. 이 결과를 통계적인 분석에 의한 표준편차와 비교하여 그 정당성을 입증하였다.

• Computers and Concrete
• /
• 제17권6호
• /
• pp.831-848
• /
• 2016

This study aims to characterize the multiple cracking behavior of HTPP-ECC (High tenacity polypropylene fiber reinforced engineered cementitious composites) by Digital Image Correlation (DIC) Method. Digital images have been captured from a dogbone shaped HTPP-ECC specimen exhibiting 3.1% tensile ductility under loading. Images analyzed by VIC-2D software and ${\varepsilon}_{xx}$ strain maps have been obtained. Crack widths were computed from the ${\varepsilon}_{xx}$ strain maps and crack width distributions were determined throughout the specimen. The strain values from real LVDTs were also compared with virtual LVDTs digitally attached on digital images. Results confirmed that it is possible to accurately monitor the initiation and propagation of any single crack or multiple cracks by DIC at the whole interval of testing. Although the analysis require some post-processing operations, DIC based crack analysis methodology can be used as a promising and versatile tool for quality control of HTPP-ECC and other strain hardening composites.

• 대한의용생체공학회:의공학회지
• /
• 제33권1호
• /
• pp.8-14
• /
• 2012

The purpose of this study was to evaluate how much effect to accuracy when measuring abdominal fat by Computed Tomography (CT) under different respiration movements. The study volunteer composed of 66 normal adults ($50.4{\pm}11.2$ years, 33 males, 33 females). We measured their obesity by using Broca index, body mass index (BMI) and CT and have investigated the correlation. The CT scanning for the obesity measurement have done in two ways, one was done in stopping breath after exhaling and the other was holding a breath after inhaling. The results showed no statistically significant difference among the three measuring techniques. And, the error in two ways of inhaling and exhaling was showed 24.2% of volunteers. The two ways of respiration movements made different result in visceral fat area (P = 0.044), subcutaneous fat area (P = 0.636) and abdominal obesity value (P = 0.012). This study demonstrates that the two ways of respiration movements when scanning CT makes change in accuracy in visceral fat area, and in abdominal obesity quantitative measure. Therefore, our study suggests that CT should take twice in two ways while a patient stops breath after exhaling and holds a breath after inhaling when measuring abdominal obesity using CT equipments.

• Journal of Korean Dental Science
• /
• 제11권1호
• /
• pp.1-4
• /
• 2018

Purpose: The aim of this study was to evaluate the ossification and maturation of the midpalatal suture in young Koreans using cone-beam computed tomography (CBCT). Materials and Methods: The study sample consisted of 40 patients with ages from 8.2 to 23.6 years who visited the Department of Orthodontics, Chung-Ang University Dental Hospital. CBCT images were taken for diagnosis. From the CBCT image, morphological stages and Hounsfield units (HU) of midpalatal suture were obtained to evaluate the midpalatal suture maturation. Spearman's correlation coefficients were calculated to analyze relationships between chronological age, morphological stage, and HU. Result: There was a wide variation in the morphology of the midpalatal suture in each age group. It showed a modest relationship between the chronological age and the degree of morphological stages. Also there was a modest relationship between the chronological age and HU. In contrast, there was a significant relationship between morphological stages and HU of midpalatal suture (P<0.01). Conclusion: CBCT images can be used for the evaluation of midpalatal suture maturation. For the estimation of the prognosis of rapid maxillary expansion, CBCT may be reliable for the assessment of the maturation of the midpalatal suture.

• Journal of Information Science Theory and Practice
• /
• 제8권2호
• /
• pp.6-17
• /
• 2020

Word similarity is often measured to enhance system performance in the information retrieval field and other related areas. This paper reports on an experimental comparison of values for word similarity measures that were computed based on 50 intentionally selected words from a Reuters corpus. There were three targets, including (1) co-occurrence-based similarity measures (for which a co-occurrence frequency is counted as the number of documents or sentences), (2) context-based distributional similarity measures obtained from a latent Dirichlet allocation (LDA), nonnegative matrix factorization (NMF), and Word2Vec algorithm, and (3) similarity measures computed from the tf-idf weights of each word according to a vector space model (VSM). Here, a Pearson correlation coefficient for a pair of VSM-based similarity measures and co-occurrence-based similarity measures according to the number of documents was highest. Group-average agglomerative hierarchical clustering was also applied to similarity matrices computed by individual measures. An evaluation of the cluster sets according to an answer set revealed that VSM- and LDA-based similarity measures performed best.

• Imaging Science in Dentistry
• /
• 제49권3호
• /
• pp.209-212
• /
• 2019

Purpose: Fossa navicularis is a bone defect in the clivus. Familiarity with this anatomical variant is important because it is close to vital anatomical structures in the base of the skull. The aim of this study was to determine the prevalence and morphometric properties of fossa navicularis within the clivus in a Turkish subpopulation using cone-beam computed tomography (CBCT). Materials and Methods: A total of 168 CBCT scans (female: 96, male: 71) were evaluated. High-quality CBCT images of patients without a syndromic condition or a history of neurological disease or surgery were included in the study. The prevalence, depth, length, and width of the fossa navicularis were performed. Results: The prevalence of fossa navicularis was 27.5% (n=46 patients). Sex was not associated with the depth, length, or width of the fossa navicularis (P>0.05). A significant positive correlation was found between age and length of the fossa navicularis(P>0.05). Conclusion: Fossa navicularis was found to be rare (27.5%). Anatomical variants of the skull base can also be clearly identified on CBCT images. The results of this study may be useful to radiologists, anatomists, and surgeons interested in the skull base.

• Imaging Science in Dentistry
• /
• 제52권2호
• /
• pp.123-131
• /
• 2022

Purpose: The aim of this study was to characterize the cone-beam computed tomographic (CBCT) imaging features of central giant cell granuloma (CGCG) of the jawbone. Materials and Methods: This study retrospectively reviewed 26 CBCT studies of histologically proven cases of CGCG during a period of 20 years, from 1999 to 2019. Patients' demographic data were recorded, and radiographic features were assessed (location, border, cortication, appearance of the internal structure, locularity, septation, expansion, cortical perforation, effects on surrounding tissue, whether the lesion crossed the midline, and lesion volume). Results: In this study, CGCGs were seen almost twice as often in the mandible than in the maxilla, and 64.7% of mandibular lesions involved the anterior region. Only 26.9% of lesions crossed the midline, a feature that was considered characteristic of CGCG. Furthermore, 65.4% of lesions were unilocular and 34.6% were multilocular. The correlation between a lesion's size and its locularity was statistically significant, and larger lesions showed a multilocular appearance. The mean volume of multilocular lesions was greater than that of unilocular lesions. Conclusion: CGCGs showed variable radiographic features on CBCT, and this imaging modality is highly effective at demonstrating the radiographic spectrum and lesional extent of CGCGs in the jawbone.