Constructing a Mesh Model of the Construction for Finite Element Method (FEM) Simulation from the Point Cloud Data Collected by Terrestrial Laser Scanning (TLS)

In recent years, there has been a significant increase in inspecting and evaluating transport infrastructure. Traditionally, these structural data were collected manually by measuring and redrawing the construction against design documents. In recent decades, laser scanning technology can help collect 3D data rapidly and accurately. The 3D point clouds can provide detailed texture and shape information of complex construction such as bridges. This study aims to develop a 3D mesh model for a finite element simulation from a 3D point cloud of a bridge's Pier collected by Terrestrial Laser Scanning (TLS). The point cloud is structured, and the object boundary points are generated using the marching cube algorithm. The boundary and inside points, which imply the vertex of the solid element in the 3D mesh model, are grouped as a new point cloud. The generated point cloud is input into 3D CAD, and the 3D solid model is manually created. As a result, the 3D mesh model is developed and successfully imported to ANSYS software for the structural behavior simulation. The accuracy of generated mesh model is good, with the relative error of geometric parameters being less than 4%. The distance from the point cloud to the mesh model is approximately 5 mm.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Optical and Laser Remote Sensin

Generating 2D Building Floors from 3D Point Clouds

Laser scanning (LS) is an effective technology for accurately capturing point clouds of visible surfaces of objects in 3D scenes. The point clouds were subsequently used for various applications, for example, generating 2D drawings of the floor or building information models (BIM) and structural inspection. However, in practice, the products from point cloud are created mainly by using commercial software, in which the quality primarily depends on users’ experiences and may contain the error caused by technician carelessness. This paper proposed a new method to automatically extract the point clouds of the floor and create a 2D drawing of floor slabs. This method analyses features of the points within cells of a 2D cell grid in the xy plane to extract candidate points of the building and each floor, while the cell- and point-based region growing segmentations were employed to extract the final points of the floor and each edge of the floor, respectively. The proposed method was successfully tested on 7.5 million points of a concrete, two-story building with 17 m long x 7m width x 7m height.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Optical and Laser Remote Sensin

Automatically Create Digital Elevation Model from Photos Captured by a Low-Cost UAV-Based System

Unmanned aerial vehicles (UAVs) are commonly utilized as cost-effective devices for data collection by capturing photos of target objects. UAV images have been used for many applications, such as civil engineering, transportation, architecture, surveying, and mapping. Although commercial UAV image data processing software is suitable for generating orthoimages and dense point clouds of surfaces, it still requires extensive labor to prepare the appropriate point cloud to create a digital elevation model (DEM). This study proposes a method to automatically create DEM from a point cloud generated from UAV images. The proposed method composes of three main steps: (1) Candidate ground points, (2) Ground points extraction, and (3) Creation of a DEM model. The proposed method was tested on three datasets, covering a total area of approximately 45 hectares from 200 images captured by DJI Phantom 4 drone. As a result, the DEMs are successfully created with a spatial resolution of 1.0 m.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Optical and Laser Remote Sensin

Conservative treatment using laser diode and systemic chemotherapy for early-stage bilateral retinoblastoma: A 14-year prospective cohort study

Background: Solid evidence of the safety and effectiveness of retinoblastoma (RB) conservative treatment using thermotherapy and systemic chemotherapy with long-term follow-up is scarce, especially in low-resource countries. Aims: This study examined the outcomes of this treatment and associated predictors in Vietnam to strengthen the current RB treatment protocol focusing on preserving eye and vision in low-resource settings. Methods and results: A prospective cohort study was conducted at Ho Chi Minh City Eye Hospital in Vietnam from 2005 to 2019. All eligible patients with bilateral RB (one eye already removed and another eye classified as group A or B) and without previous treatment were recruited. All patients received thermotherapy and six cycles of systemic three-agent chemotherapy repeated every 4 weeks. A standardized questionnaire was used to collect information on study participants' age, symptoms, tumor characteristics, treatment, and outcomes. Among 50 eyes of all 50 patients with a median age of 9 (4–20) months, 34 eyes were in group B (68%). The median follow-up time was 60 (60–84) months. All 139 preserved tumors regressed mostly to type 4 (70.4%) and type 3 (23.7%) scars. Kaplan–Meier analysis found the overall globe-salvage rate at 5 years of 91.9% (95% CI: 80.1%–97.7%). Most eyes (41/50, 82%, 95% CI: 69.2%–90.2%) had a final visual acuity ≥0.1. The visual acuity is higher when tumors regressed to a type 4 scar (p =.007, AOR = 8.098, 95% CI: 1.79–36.53) which also shows less enucleation than a type 3 scar (p =.002, AOR = 0.06, 95% CI: 0.01–0.37%). Gender effect on visual acuity after treatment was significant and may be due to discrimination. No major complications were recorded. Conclusion: Conservative treatment of early-stage RB is safe and effective. Long-term, thorough follow-ups of patients post-treatment are needed. The regression patterns of scars could be a useful indicator of treatment failure.Statistic