scholarly journals Defect localization by an extended laser source on a hemisphere

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daniel Veira Canle ◽  
Joni Mäkinen ◽  
Richard Blomqvist ◽  
Maria Gritsevich ◽  
Ari Salmi ◽  
...  
Keyword(s):  
Acoustic Waves ◽  
Line Source ◽  
3D Model ◽  
Scattering Problem ◽  
Laser Line ◽  
Experimental Results ◽  
Laser Source ◽  
Fem Simulations ◽  
Specific Direction ◽  
Defect Localization

AbstractThe primary goal of this study is to localize a defect (cavity) in a curved geometry. Curved topologies exhibit multiple resonances and the presence of hotspots for acoustic waves. Launching acoustic waves along a specific direction e.g. by means of an extended laser source reduces the complexity of the scattering problem. We performed experiments to demonstrate the use of a laser line source and verified the experimental results in FEM simulations. In both cases, we could locate and determine the size of a pit in a steel hemisphere which allowed us to visualize the defect on a 3D model of the sample. Such an approach could benefit patients by enabling contactless inspection of acetabular cups.

Experimental Study on the Detection of Surface-Breaking Defects on Metal with the Scanning Laser Line Source Technique

2007 ◽  
Vol 364-366 ◽  
pp. 1117-1122
Author(s):  
Gang Yan ◽  
Chen Yin Ni ◽  
Yi Fei Shi ◽  
Zhong Hua Shen ◽  
Jian Lu ◽  
...  
Keyword(s):  
Acoustic Waves ◽  
Line Source ◽  
Surface Acoustic Waves ◽  
Interaction Mechanism ◽  
Experimental System ◽  
Laser Line ◽  
Scanning Laser ◽  
Electric Signal ◽  
Inspection Method ◽  
Small Surface

The scanning laser line source (SLLS) technique is a novel laser-based inspection method for the ultrasonic detection of small surface-breaking defects. The SLLS approach is based on monitoring the change in laser generated ultrasound as a laser line source is scanning over a defect. It has provided enhanced signal-to-noise performance compared to the traditional pitch-catch or pulse-echo ultrasonic methods. In this paper, an experimental method is presented to detect surface acoustic waves (SAW) with polyvinylindene fluoride(PVDF) transducer. The ultrasonic signal is converted into electric signal by piezoelectricity of the PVDF, which is attached to a micro-knife edge clamped on a metal device. The SAW are excited by employing a pulsed Nd:YAG laser on aluminum plate with artificial surface-breaking defects. The laser line source is accurately shifted by the motorized translation stage, while the PVDF is located at a fixed position on the specimen. When the laser line source is scanning over the defect, the ultrasonic signals are monitored, meanwhile the characteristic changes in the amplitude and frequency content are observed. Consequently, the position of the defect can be determined by analyzing the obtained signals. The experimental system with high sensitivity provides a detection method of small surface-breaking defects on metal and gives convincing experimental evidence for the interaction mechanism between the SAW and the surface-breaking defects.

Laser optoacoustic detection of trace concentration levels of ethylene, vinylchloride, and styrene in the atmosphere

1989 ◽  
Vol 54 (10) ◽  
pp. 2667-2673 ◽  
Author(s):  
Vojtěch Steiner ◽  
Pavel Engst ◽  
Zdeněk Zelinger ◽  
Milan Horák
Keyword(s):  
Detection Limit ◽  
Emission Line ◽  
Laser Line ◽  
Laser Source ◽  
Trace Concentration ◽  
Selective Determination ◽  
Hygienic Standard ◽  
Trace Concentrations ◽  
Concentration Levels

The optoacoustic analyzer with a tunable CO2 laser source employed in the present work permits a selective determination of ethylene in trace concentrations higher than 5 ppb (=detection limit for the 10P(14) emission line of the CO2 laser, ν = 949.5 cm-1) and of vinylchloride higher than 42 ppb (= detection limit for the 10P(22) CO2 laser line, ν= 942.4 cm-1). this method covers for both compounds the concentration range corresponding to the hygienic standard. It can be also used for the determination of styrene vapour with concentrations higher than 1.5 ppm.

Solvable model of a quantum particle in a detector

2019 ◽  
Vol 17 (08) ◽  
pp. 1941004
Author(s):  
David Gaspard ◽  
Jean-Marc Sparenberg
Keyword(s):  
3D Model ◽  
Quantum Particle ◽  
Scattering Problem ◽  
Solvable Model ◽  
Forward Direction ◽  
Perturbative Calculation ◽  
Spherical Waves ◽  
Track Formation ◽  
Small Influence ◽  
Stationary Scattering

The interaction of a quantum particle with a gaseous detector is studied in the quantum-mechanical state space of the particle-detector system by means of a simple stationary scattering 3D model. The particle is assumed to interact with [Formula: see text] two-level point-like scatterers depicting the atoms of the detector. Due to the contact interaction, the particle scatters off the atoms in isotropic spherical waves. Remarkably, the Lippmann–Schwinger equation of this multiple scattering problem can be exactly solved in a nonperturbative way. The aim is to analyze the influence of the initial microstate of the detector on the observed outcome, and to understand the mechanism of track formation in gaseous detectors. It is shown that the differential cross-section of excitation must be large enough in the forward direction to get the formation of tracks. In addition, the relatively small influence of atomic positions is highlighted. These results are explained through a perturbative calculation.

scholarly journals Marching Cubes and Histogram Pyramids for 3D Medical Visualization

2020 ◽  
Vol 6 (9) ◽  
pp. 88
Author(s):  
Porawat Visutsak
Keyword(s):  
Feature Extraction ◽  
Smooth Surface ◽  
3D Model ◽  
Good Choice ◽  
Experimental Results ◽  
Marching Cubes ◽  
Surface Rendering ◽  
Medical Visualization ◽  
Hierarchical Order ◽  
Volumetric Rendering

This paper aims to implement histogram pyramids with marching cubes method for 3D medical volumetric rendering. The histogram pyramids are used for feature extraction by segmenting the image into the hierarchical order like the pyramid shape. The histogram pyramids can decrease the number of sparse matrixes that will occur during voxel manipulation. The important feature of the histogram pyramids is the direction of segments in the image. Then this feature will be used for connecting pixels (2D) to form up voxel (3D) during marching cubes implementation. The proposed method is fast and easy to implement and it also produces a smooth result (compared to the traditional marching cubes technique). The experimental results show the time consuming for generating 3D model can be reduced by 15.59% in average. The paper also shows the comparison between the surface rendering using the traditional marching cubes and the marching cubes with histogram pyramids. Therefore, for the volumetric rendering such as 3D medical models and terrains where a large number of lookups in 3D grids are performed, this method is a particularly good choice for generating the smooth surface of 3D object.

Sign in / Sign up

Export Citation Format

Share Document