A new Doppler-effect–based method for nondestructive testing of the condition of the inner walls of pipelines using a flowing fluid is considered. An optical method has been used to reveal specific features in the structure of the fluid-medium flow in a circular-section pipeline. A new technique that makes use of laser radiation scattered on flowing-fluid particles has been proposed for determining the coordinates of a flawed zone on the inner pipeline wall. The technique makes it possible to determine the zone coordinates along the length and diameter of the pipeline.

A Contactless Method for Testing Inner Walls of Pipelines

Tomographic particle image velocimetry (PIV) has become a standard tool for 3D velocity measurements in non-reacting flows. However, the majority of the measurements in flows with combustion are limited to small resolved depth compared to the size of the field of view (typically 1 : 10). The limitations are associated with inhomogeneity of the volume illumination and the non-uniform flow seeding, the optical distortions and errors in the 3D calibration, and the unwanted flame luminosity. In the present work, the above constraints were overcome for the tomographic PIV experiment in a laminar axisymmetric premixed flame. The measurements were conducted for a 1 : 1 depth-to-size ratio using a system of eight CCD cameras and a 200 mJ pulsed laser. The results show that camera calibration based on the triangulation of the tracer particles in the non-reacting conditions provided reliable accuracy for the 3D image reconstruction in the flame. The modification of the tomographic reconstruction allowed a posteriori removal of unwanted bright objects, which were located outside of the region of interest but affected the reconstruction quality. This study reports on a novel experience for the instantaneous 3D velocimetry in laboratory-scale flames by using tomographic PIV.

https://iopscience.iop.org/article/10.1088/0957-0233/26/6/064001/pdf

3D velocity measurements in a premixed flame by tomographic PIV

Application of parametric discrete Fourier transform in nondestructive testing of composite materials with a free oscillation method

This paper considers the problems of development and application of digital technologies in non-destructive testing (NDT). Conducting NDT is represented as some generalized information process. A specific object is represented in the form of digital stages: obtaining accessible, reliable and sufficient information about the properties and state of the object of testing, processing the received primary information, analyzing the processed information, making decisions about further actions with the testing object. In the paper at the system level, the formalization of an urgent and important scientific problem is proposed-the problems of developing digital technology (technologies) for each of the stages of the NDT information process. It is shown that a systematic approach to resolving a problem allows one to formulate a morphological, functional and informational description of the problem, as well as to find hypotheses for solving the problem by carrying out a sequence of operations that solve the problem. A universal structural scheme has been developed for solving scientific problems in the development of digital technologies at the stages of the NDT information process. An example of the practical application of the above approach for one of the NDT methods-functional vibro-acoustic diagnosis of objects is given.

https://iopscience.iop.org/article/10.1088/1742-6596/1327/1/012038/pdf

Digital technologies in non-destructive testing

The depth of two-dimensional plane images spaced apart along the visual axis of the eye for stimulating accommodation in 3D displays is considered. The diffraction depth of the plane images is determined, and it is demonstrated to increase with decreasing image resolution acuity.

Diffraction depth of three-dimensional images stimulating eye accommodation

A 3D image in the form of a linear combination of two two-dimensional images located at different depths along the line of vision of the eye is considered. The loss of contrast and nonlinearity of accommodation over the depth with a high resolution acuity of 3D images are demonstrated in computer experiments with different eye models.

Quality of a three-dimensional image stimulating eye accommodation

Calculations of a dedicated optical system for the quality inspection of cylindrical surfaces are presented. Peculiarities of imaging a cylindrical surface by means of specially enhanced inherent field curvature are considered. Results of using the system for the inspection of quality of fuel pellets are provided.

A dedicated optical system for the quality inspection of cylindrical surfaces

Optoelectronic methods for controlling the appearance of nuclear reactor fuel pellets are considered. In the proposed methods, reflected images of pellet surfaces are taken by digital cameras, which provides high contrast of defective areas against the frame background. Image processing algorithms for identification of defective products are given. An experimental model of a system with a capacity of up to 10 pellets per second was designed. A database containing surface images of simulators and real pellets was designed to train the system. Results of real time processing of the obtained images show that the probability of detection of defective pellets is not less than 95%.

Multichannel high-performance optoelectronic control of the surface of fuel pellets

The contrast of a combination of two plane images spaced along the visual axis of the eye for stimulating the accommodation in 3D displays is analyzed. Two methods of normalization based on individual and group calculations of optimal coefficients of combinations for different eye pupil diameters with a specified image resolution are proposed.

E. V. Vlasov

Papers

Diffraction depth of three-dimensional images stimulating eye accommodation

Quality of a three-dimensional image stimulating eye accommodation

A dedicated optical system for the quality inspection of cylindrical surfaces

Multichannel high-performance optoelectronic control of the surface of fuel pellets

Methods of Improving the Contrast of Combined Images and the Linearity of the Eye Accommodation Stimulus in Multifocal Three-Dimensional Displays