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21 pages, 8854 KB

Open AccessArticle

An Effective Framework Using Spatial Correlation and Extreme Learning Machine for Moving Cast Shadow Detection

by Yugen Yi, Jiangyan Dai, Chengduan Wang, Jinkui Hou, Huihui Zhang, Yunlong Liu and Jin Gao

Appl. Sci. 2019, 9(23), 5042; https://doi.org/10.3390/app9235042 - 22 Nov 2019

Cited by 7 | Viewed by 2712

Abstract

Moving cast shadows of moving objects significantly degrade the performance of many high-level computer vision applications such as object tracking, object classification, behavior recognition and scene interpretation. Because they possess similar motion characteristics with their objects, moving cast shadow detection is still challenging. In this paper, we present a novel moving cast shadow detection framework based on the extreme learning machine (ELM) to efficiently distinguish shadow points from the foreground object. First, according to the physical model of shadows, pixel-level features of different channels in different color spaces and region-level features derived from the spatial correlation of neighboring pixels are extracted from the foreground. Second, an ELM-based classification model is developed by labelled shadow and unlabelled shadow points, which is able to rapidly distinguish the points in the new input whether they belong to shadows or not. Finally, to guarantee the integrity of shadows and objects for further image processing, a simple post-processing procedure is designed to refine the results, which also drastically improves the accuracy of moving shadow detection. Extensive experiments on two publicly common datasets including 13 different scenes demonstrate that the performance of the proposed framework is superior to representative state-of-the-art methods. Full article

(This article belongs to the Section Optics and Lasers)

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13 pages, 15389 KB

Open AccessArticle

Wear Resistance Mechanism of ZTA_P/HCCI Composites with a Honeycomb Structure

by Mojin Zhou, Yudong Sui, Xiaoyu Chong and YeHua Jiang

Metals 2018, 8(8), 588; https://doi.org/10.3390/met8080588 - 28 Jul 2018

Cited by 37 | Viewed by 5046

Abstract

The abrasive wear resistance of zirconia toughened alumina (ZTA) ceramic particle reinforced high chromium cast iron (HCCI) composites has been systematically investigated using a moving wedge type of apparatus. The results of three-body abrasive wear show that the wear resistance of the composites with honeycomb is three times higher than that of the high chromium cast iron. The wear resistance of the composites with a honeycomb structure is close to that of the layer structure and is higher than that of the HCCI because the honeycomb wall in the cell honeycomb structure is prominent and because the honeycomb core is depressed. The wear mechanisms of the composites are mainly microcutting and fatigue fractures. The honeycomb structure forms a “macrocosmic shadow protection effect” and a “microcosmic shadow protection effect” to protect each composite and to improve the wear resistance of the composites. Full article

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27 pages, 9177 KB

Open AccessArticle

Background Subtraction for Moving Object Detection in RGBD Data: A Survey

by Lucia Maddalena and Alfredo Petrosino

J. Imaging 2018, 4(5), 71; https://doi.org/10.3390/jimaging4050071 - 16 May 2018

Cited by 71 | Viewed by 12976

Abstract

The paper provides a specific perspective view on background subtraction for moving object detection, as a building block for many computer vision applications, being the first relevant step for subsequent recognition, classification, and activity analysis tasks. Since color information is not sufficient for dealing with problems like light switches or local gradual changes of illumination, shadows cast by the foreground objects, and color camouflage, new information needs to be caught to deal with these issues. Depth synchronized information acquired by low-cost RGBD sensors is considered in this paper to give evidence about which issues can be solved, but also to highlight new challenges and design opportunities in several applications and research areas. Full article

(This article belongs to the Special Issue Detection of Moving Objects)

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12 pages, 821 KB

Open AccessArticle

Visual Sensor Based Abnormal Event Detection with Moving Shadow Removal in Home Healthcare Applications

by Young-Sook Lee and Wan-Young Chung

Sensors 2012, 12(1), 573-584; https://doi.org/10.3390/s120100573 - 5 Jan 2012

Cited by 40 | Viewed by 8627

Abstract

Vision-based abnormal event detection for home healthcare systems can be greatly improved using visual sensor-based techniques able to detect, track and recognize objects in the scene. However, in moving object detection and tracking processes, moving cast shadows can be misclassified as part of objects or moving objects. Shadow removal is an essential step for developing video surveillance systems. The goal of the primary is to design novel computer vision techniques that can extract objects more accurately and discriminate between abnormal and normal activities. To improve the accuracy of object detection and tracking, our proposed shadow removal algorithm is employed. Abnormal event detection based on visual sensor by using shape features variation and 3-D trajectory is presented to overcome the low fall detection rate. The experimental results showed that the success rate of detecting abnormal events was 97% with a false positive rate of 2%. Our proposed algorithm can allow distinguishing diverse fall activities such as forward falls, backward falls, and falling asides from normal activities. Full article

(This article belongs to the Section Physical Sensors)

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15 pages, 300 KB

Open AccessArticle

The Park 51/Ground Zero Controversy and Sacred Sites as Contested Space

by Jeanne Halgren Kilde

Religions 2011, 2(3), 297-311; https://doi.org/10.3390/rel2030297 - 25 Jul 2011

Cited by 15 | Viewed by 15263

Abstract

The Park 51 controversy swept like wildfire through the media in late August of 2010, fueled by Islamophobes who oppose all advance of Islam in America. Yet the controversy also resonated with many who were clearly not caught up in the fear of Islam. This article attempts to understand the broader concern that the Park 51 project would somehow violate the Ground Zero site, and, thus, as a sign of "respect" should be moved to a different location, an argument that was invariably articulated in “spatial language” as groups debated the physical and spatial presence of the buildings in question, their relative proximity, and even the shadows they cast. This article focuses on three sets of spatial meanings that undergirded these arguments: the site as sacred ground created through trauma, rebuilding as retaliation for the attack, and the assertion of American civil religion. The article locates these meanings within a broader civic discussion of liberty and concludes that the spatialization of the controversy opened up discursive space for repressive, anti-democratic views to sway even those who believe in religious liberty, thus evidencing a deep ambivalence regarding the legitimate civic membership of Muslim Americans. Full article

(This article belongs to the Special Issue Islam in America: Zeroing in on the Park51 Controversy)

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