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An algorithm for fatigue crack growth applied to mixed and biaxial mode loadings

Procedia Structural Integrity 2019年 17卷 547-554页

作者： R. Baptista V. Infante M. Freitas CDP2T and Department of Mechanical Engineering Setúbal School of Technology Instituto Politécnico de Setúbal 2910-761 Setúbal Portugal IDMEC Escola Superior de Tecnologia de Setúbal Instituto Politécnico de Setúbal 2910-761 Setúbal Portugal IDMEC Instituto Superior Técnico Universidade de Lisboa Lisboa Portugal

Fatigue is still one of the main concerns when dealing with mechanical components failure. While it is fundamental to experimentally determine the fatigue material behavior using standard specimens, testing large and complex component geometries can be complicated. In these cases, the Finite Element Method can be a cost-effective solution but developing fatigue crack growth models is still a complicated task. In order to solve this problem, an algorithm for automatic crack propagation was developed. Using three different modules, the algorithm can generate a complex Finite Element Method model including a fatigue crack; solve this model considering complex loading conditions, by applying the superposition method; and calculate the fatigue crack propagation rate, using it to update the original model. In order to benchmark this solution two different problems were analyzed, a modified compact tension specimen and a cruciform specimen. By modifying the compact tension specimen hole location and simulating an initial crack, it was possible to understand how mixed mode conditions influence the fatigue crack path. Different load ratios and initial crack directions on the cruciform specimen were analyzed. Increasing the load ratio will increase the crack deflecting angle. The obtain solutions were compared with experimental results, showing good agreement. Therefore the developed algorithm can be used to predict the fatigue crack growth behavior on complex geometries and when different types of loads are applied to the component.

关键词： Fatigue Crack propagation Mixed mode automatic algorithm

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Adaptive beamforming with automatic diagonal loading in medical ultrasound imaging 25

Adaptive beamforming with automatic diagonal loading in medi...

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25th Iranian Conference on Biomedical Engineering / 3rd International Iranian Conference on Biomedical Engineering (ICBME)

作者： Salari, Ali Asl, Babak Mohammadzadeh Tarbiat Modares Univ Dept Biomed Engn Tehran Iran

ISBN: (纸本)9781538679524

In medical ultrasound imaging, the most famous adaptive beamforming algorithm is the minimum variance (MV). Diagonal loading (DL) method is usually used to improve the robustness of the MV. Conventional DL methods have a critical problem which is determining the loading factor ignoring the input data. To address this problem, in this paper, using the shrinkage algorithm is proposed in which the loading coefficient is completely automated and determined by the input data. The performance of the proposed algorithm is evaluated by simulated ultrasound data in Field II. In point targets simulation, it has been shown that the proposed method improves the resolution about 87% and 20%, compared to delay and sum (DAS) and MV algorithms (with a fixed loading coefficient of), respectively. In addition, in anechoic cyst simulation, the contrast and relative contrast of the proposed method has been retained, in comparison to those of the MV beamformer, while they are improved about 5% and 18%, in comparison to the DAS ones, respectively.

关键词： Medical ultrasound imaging minimum variance beamformer diagonal loading coefflcient automatic algorithm

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Verification of new method for automatic thickness measurement of melanocytic skin tumours by high frequency ultrasound

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JOURNAL OF VIBROENGINEERING 2018年第1期20卷 651-661页

作者： Linkeviciute, Gintare Raisutis, Renaldas Sakalauskiene, Kristina Makstiene, Jurgita Guzaitis, Jonas Pilipaityte, Loreta Valiukeviciene, Skaidra Lithuanian Univ Hlth Sci Dept Skin & Venereal Dis Kaunas Lithuania Kaunas Univ Technol Ultrasound Inst Kaunas Lithuania Lithuanian Univ Hlth Sci Dept Pathol Anat Kaunas Lithuania Kaunas Univ Technol Kaunas Lithuania Lithuanian Univ Hlth Sci Dept Plast & Reconstruct Surg Kaunas Lithuania

Histological thickness of cutaneous melanoma (CM), known as the Breslow index (pT), represents the most important prognostic factor. The objective of this study is to evaluate the reliability of automatic algorithm based on B-scan image processing of 22 MHz ultrasound (US) for measuring the thickness of CM and melanocytic nevi (MN). The thickness of CM (n = 54) and MN (n = 91) has been measured manually (mT) and automatically (aT) using an algorithm based on B-scan image processing of 22 MHz US. All melanocytic skin tumours (MST) were surgically excised and their histological thicknesses (pT) according to Breslow were evaluated. The investigated parameters were expressed as medians with interquartile range (IQR) because of their asymmetric distribution, Spearman's correlation coefficient was determined as well. An agreement between values of mT/aT and mT/pT was evaluated by using the Bland-Altman plots. We found a good agreement of aT and mT with the moderate bias of 0.08 mm and relatively small range (95 % CI -0.01 to 0.18) in CM, accordingly 0.03 mm (95 % CI 0.00 to 0.07 mm) regarding MN. The medians of mT/pT in cases of CM and MN were 0.96 mm (IQR: 0.65-1.52)/0.97 (IQR: 0.66-1.62) and 0.51 mm (IQR: 0.37-0.67) /0.69 mm (IQR: 0.46-1.01) respectively. The parameters of the thickness correlated better in CM (r = 0.86) than in MN (r = 0.64) cases. The difference between manual (mT) and automatic (aT) measurements while evaluating the thickness of MST was non-significant. Therefore, automatic algorithm based on B-scan image processing of 22 MHz US is a reliable tool for measuring the thickness of MST by less experienced operators.

关键词： melanoma thickness melanocytic skin tumors ultrasound automatic algorithm histology

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A new auroral boundary determination algorithm based on observations from TIMED/GUVI and DMSP/SSUSI

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JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 2017年第2期122卷 2162-2173页

作者： Ding, Guang-Xing He, Fei Zhang, Xiao-Xin Chen, Bo Chinese Acad Sci Changchun Inst Optic Fine Mech & Phys Changchun Peoples R China Univ Chinese Acad Sci Daheng Coll Beijing Peoples R China Chinese Acad Sci Inst Geol & Geophys Key Lab Earth & Planetary Phys Beijing Peoples R China China Meteorol Adm Natl Ctr Space Weather Key Lab Space Weather Beijing Peoples R China

An automatic auroral boundary determination algorithm is proposed in this study based on the partial auroral oval images from the Global Ultraviolet Imager (GUVI) aboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite and the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) aboard the Defense Meteorological Satellite Program (DMSP F16). This algorithm based on the fuzzy local information C-means clustering segmentation can be used to extract the auroral oval poleward and equatorward boundaries from merged images with filled gaps from both GUVI and SSUSI. Both extracted poleward and equatorward boundary locations are used to fit the global shape of the auroral oval with a off-center quasi-elliptical fitting technique. Comparison of the extracted auroral oval boundaries with those identified from the DMSP SSJ observations demonstrates that this new proposed algorithm can reliably be used to construct the global configuration of auroral ovals under different geomagnetic activities at different local times. The statistical errors of magnetic latitudes of the fitted auroral oval boundaries were generally less than 3 degrees at 2 sigma and indicate that the the fitted boundaries agree better with b2e and b5e than b1e and b6 boundaries. This proposed algorithm provides us with a useful tool to extract the global shape and position of the auroral oval from the partial auroral images.

关键词： auroral boundary auroral images automatic algorithm quasi-elliptical fitting

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Automated JTpeak analysis by BRAVO

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JOURNAL OF ELECTROCARDIOLOGY 2017年第6期50卷 752-757页

作者： Badilini, Fabio Libretti, Guido Vaglio, Martino AMPS LLC New York NY 10025 USA

Using BRAVO algorithm (AMPS-LLC, NY, v4.4.0), 5223 ECGs from a publicly available annotated dataset from a randomized clinical trial on four different compounds and placebo were analyzed. ECGs were automatically processed and JTp interval was computed on: 12 standard ECG leads, Vector Magnitude (VM),.and root mean square (RMS) leads. On VM and RMS, JTp intervals were nearly identical (228 +/- 29 vs. 227 +/- 30 ms respectively, with correlation of 0.99, p < 0.0001). On lead II, JTp interval was about 10 ms longer, but highly correlated with that measured on VM (0.94, p < 0.0001). Similarly, on lead V5, JTp was about 8 ms longer than on VM, with a correlation of 0.95, p < 0.0001. When compared to the public available annotations, JTp by BRAVO generated longer (about 8 ms) measurement and evidenced outliers conducible to both the T-wave peak (in few ECGs presenting notched shapes) and, to a lesser degree, to the J point, due to variability of the two algorithms. Differences on the drug-induced effect from the four compounds were negligible. (C) 2017 Elsevier Inc. All rights reserved.

关键词： T-wave morphology T-wave peak JTp automatic algorithm PhysioNet ISCE

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A new thresholding approach for automatic generation of polygonal approximations

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JOURNAL OF VISUAL COMMUNICATION AND IMAGE REPRESENTATION 2016年 35卷 155-168页

作者： Fernandez-Garcia, N. L. Del-Moral Martinez, L. Carmona-Poyato, A. Madrid-Cuevas, F. J. Medina-Carnicer, R. Univ Cordoba Dept Comp & Numer Anal Maimonides Inst Biomed Res IMIBIC Cordoba Spain

The present paper proposes a new algorithm for automatic generation of polygonal approximations of 2D closed contours based on a new thresholding method. The new proposal computes the significance level of the contour points using a new symmetric version of the well-known Ramer, Douglas-Peucker method, and then a new Adaptive method is applied to threshold the normalized significance level of the contour points to generate the polygonal approximation. The experiments have shown that the new algorithm has good performance for generating polygonal approximations of 2D closed contours. Furthermore, the new algorithm does not require any parameter to be tuned. (C) 2015 Elsevier Inc. All rights reserved.

关键词： Digital planar curves Polygonal approximation Dominant points Significance of contour points Thresholding techniques Object recognition Assessment of polygonal approximations Corner points automatic algorithm

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Innovative ultrasound approach to estimate spinal mineral density: diagnostic assessment on overweight and obese women

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IET SCIENCE MEASUREMENT & TECHNOLOGY 2016年第1期10卷 1-9页

作者： Casciaro, Sergio Pisani, Paola Conversano, Francesco Renna, Maria Daniela Soloperto, Giulia Casciaro, Ernesto Quarta, Eugenio Grimaldi, Antonella Muratore, Maurizio CNR Inst Clin Physiol Lecce Italy Echolight Srl Lecce Italy Galateo Hosp OU Rheumatol ASL LE Lecce Italy

The aim of this study is to assess the accuracy of a novel ultrasound (US) approach for lumbar spine densitometry on overweight and obese women of variable age through a clinical validation study. The US method was originally developed in women with body mass index (BMI) < 25 kg/m(2). In this study, 382 female patients were recruited (45-80 years, BMI > 25 kg/m(2)) and underwent dual X-ray absorptiometry (DXA) of lumbar spine (L1-L4) and an US scan of the same vertebrae L1-L4, performed with a dedicated device providing both echographic images and raw' radiofrequency signals. Acquired US data were analysed through a novel automatic algorithm that performed a series of spectral and statistical analyses to calculate bone mineral density employing an innovative method. Diagnostic accuracy of US investigations was quantitatively assessed through a direct comparison with DXA results. The average agreement between US and DXA diagnoses was acceptable for patients aged 45-65 years (81.5%), while a slight decrement was observed for older patients (69.6%), which can be partially due to a decrease in DXA accuracy because of age-related degenerations. The adopted method has a potential for early osteoporosis diagnosis in people younger than 65 years, independent of their BMI.

关键词： biomedical ultrasonics bone density measurement patient diagnosis diseases age 45 yr to 65 yr early osteoporosis diagnosis diagnostic accuracy raw radiofrequency signals lumbar spine DXA body mass index spinal mineral density estimation automatic algorithm echographic images vertebrae dual X-ray absorptiometry lumbar spine densitometry obese women overweight women diagnostic assessment ultrasound approach

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automatic Brain Morphometry and Volumetry Using SPM on Cognitively Impaired Patients

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IEEE LATIN AMERICA TRANSACTIONS 2015年第4期13卷 1077-1082页

作者： Cutanda, V. Moratal, D. Arana, E. Univ Politecn Valencia Ctr Biomat & Ingn Tisular E-46022 Valencia Spain Fdn Inst Valenciano Oncol Valencia Spain

Alzheimer disease (AD) is the most common type of dementia and mild cognitive impairment (MCI) is a syndrome with an increased risk of developing dementia. As neuroimaging is relevant in their diagnosis, the purpose of this paper is to develop an automatic classification methodology of AD, MCI and control patients. A total of 83 subjects provided by ADNI (Alzheimer's Disease Neuroimaging Initiative) were studied (26 controls, 24 MCI and 33 AD patients) to develop an automatic method. It allows voxel-based morphometry (VBM) optimized by Dartel coregistration and complemented with a volumetric quantification subalgorithm. The developed algorithm implements VBM automatically and segments the three main brain tissues accurately. Difference between controls and AD increased during follow-up (Anova, p = 0,001). Finally statistical parametric maps were created from output images, where morphometric and volumetric differences can be appreciated. This algorithm automates brain imaging volumetry in cognitive impaired patients and control subjects. Even with the described limitations, the developed methodology is fast and user independent and it improves the traditional voxel-based morphometry algorithm.

关键词： voxel based morphometry magnetic resonance imaging volumetry Alzheimer disease mild cognitive impairment automatic algorithm neuroimaging SPM

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Automated Object Extraction from MLS Data: a Survey 10

Automated Object Extraction from MLS Data: a Survey

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10th International Conference on Intelligent Systems and Knowledge Engineering (ISKE)

作者： Chen Kunyuan Cheng Ming Zhou Menglan Chen Xinqu Chen Yifei Jonathan, Li Nie Hongshan Xiamen Univ Sch Informat Sci & Engn Fujian Key Lab Sensing & Comp Smart City Xiamen 361005 Fujian Peoples R China Univ Waterloo Dept Geog & Environm Management GeoSTARS Lab Waterloo ON N2L 3G1 Canada Hunan Intelligent Things Technol Co Ltd Changsha 410000 Hunan Peoples R China

ISBN: (纸本)9781467393232

Realistic 3D city modeling using Mobile Laser Scanning (MLS) technique experienced a remarkable revolution in aiding urban planning, regulation design, city management, navigation, and emergency responses. This paper focuses on thoroughly examining the advance of automated MLS object extraction techniques over the last five years. Categorized as either on-road or off-road, mainly six objects are included in this paper (road curbs, road markings, pavement cracks, building facades, pole-like objects and trees). MLS extraction techniques applied on typical objects is evaluated according to their method design, degree of automation, precision, and computational efficiency. Recent researches mostly focus on developing accurate object extraction algorithms and most of the reviewed methods can achieve high precision;however, optimizing the trade-off between computational cost and accuracy remains a big challenge. In addition, there is still no general standardized approach to deal with MLS objects extractions to date;most algorithms reviewed in this paper still need some artificial interference to ensure accuracy and efficiency.

关键词： MLS technique automatic algorithm object extraction literature review

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Semi-automatic segmentation of myocardium at risk from contrast enhanced SSFP images - validation against manual delineation and SPECT

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Journal of Cardiovascular Magnetic Resonance 2015年第SUPPL 1期17卷 Q127-Q127页

作者： Jane Tufvesson Marcus Carlsson Anthony H Aletras Henrik Engblom Jean-Francois Deux Sasha Koul Peder Sörensson John Pernow Dan Atar David Erlinge Håkan Arheden Einar Heiberg Cardiac MR group Lund Dept. of Clinical Physiology Lund University Lund Sweden Dept of Numerical Analysis Faculty of Engineering Lund University Lund Sweden Dept of Cardiology Henri Mondor Hospital Creteil France Dept of Cardiology Lund University Lund Sweden Dept of Medicine Karolinska Institutet Karolinska University Hospital Stockholm Sweden Dept of Cardiology B Oslo University Hospital Ullevål and Faculty of Medicine University of Oslo Oslo Norway

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