Automated Aircraft Dent Inspection via a Modified Fourier Transform Profilometry Algorithm

The search for dents is a consistent part of the aircraft inspection workload. The engineer is required to find, measure, and report each dent over the aircraft skin. This process is not only hazardous, but also extremely subject to human factors and environmental conditions. This study discusses the feasibility of automated dent scanning via a single-shot triangular stereo Fourier transform algorithm, designed to be compatible with the use of an unmanned aerial vehicle. The original algorithm is modified introducing two main contributions. First, the automatic estimation of the pass-band filter removes the user interaction in the phase filtering process. Secondly, the employment of a virtual reference plane reduces unwrapping errors, leading to improved accuracy independently of the chosen unwrapping algorithm. Static experiments reached a mean absolute error of ∼0.1 mm at a distance of 60 cm, while dynamic experiments showed ∼0.3 mm at a distance of 120 cm. On average, the mean absolute error decreased by ∼34%, proving the validity of the proposed single-shot 3D reconstruction algorithm and suggesting its applicability for future automated dent inspections.

The Influence of the Mandibular Chin Angle on the Occurrence of Mandibular Condylar Fracture: A Retrospective Study

Background. Condylar fractures are commonly associated with symphysis/parasymphysis fractures. Condylar fractures have been attributed to direct and indirect traumatic forces, the direction and magnitude of the forces, and the condylar anatomy. The chief aim of this study was to determine the association between the newly defined mandibular chin angle and the occurrence of condylar fractures. Materials and Methods. A retrospective study was conducted to analyze two-dimensional computed tomography (2D CT) scans of patients with a history of chin trauma. The outcome was a symphysis/parasymphysis fracture with or without fracture of the mandibular condyle. The Mediff InstaRISPACS web-based platform was used to measure the chin angle. The cerebral aqueduct of Sylvius in the corresponding 2D CT midsagittal image was the standard reference plane to measure the chin angle. The SPSS Version 20 (IBM Corp, Armonk, NY) was used for data analysis. Results. The sample size included 120 2D CT scans of patients with symphysis/parasymphysis fractures (60 associated with condylar fractures and 60 without condylar fractures). The mean chin angle in the group without condylar fracture was 133.35 ± 3.87°, which was approximately 15° lesser than in the condylar fracture group (mean, 148.56 ± 5.49°), and these findings were statistically significant P < 0.05 . Conclusion. Individuals with a high chin angle are potentially at a higher risk of sustaining associated condylar fractures.

Postural regulation of teenagers performing pop dance, according to stabilometry data

Knowledge of postural regulation in different sports is useful for sports selection and for improvement of postural stereotypes.Objective: to reveal postural regulation features of teenagers involved in pop dance.Materials and methods: 15 pop dancers involved in dance more than 10 years performed Romberg and optokinetic tests on computer stabilograph “Trust-M Stabilo”.Results: the area and length of the dancers’ statokinesiogram were less than in general sample, statokinesiogram’s pressure center had been dextrally dislocated. Visual disturbances as well as vision deprivation led to statistically significant increase in speed of center of pressure movement along reference plane and in the ratio of statokinesiogram’s length to its area. All these changes were less pronounced than in the general sample.Conclusions: postural regulation of dancers proved to be better than that of healthy people who were not involved in sports.

Real-Time Double-Layer Thin Film Thickness Measurements Using Modified Sagnac Interferometer with Polarization Phase Shifting Approach

This paper describes a modified Sagnac interferometer with a self-referenced polarization and phase-shifting technique for real-time thickness measurement of single- and double-layer transparent thin films. The proposed interferometric setup generated outstanding rotating linearly polarized light with a degree of polarization (DOP) of 99.40%. A beam splitter placed at the interferometer output separated the beam into two identical linearly polarized beams. One of the beams served as a reference, while the other served as a sensing arm. The output linear polarizer set at 45° relative to a reference plane was positioned anterior to the photodetectors to get rotating light intensities for phase shift measurement; hence, the intensities at various polarizations of 0°, 45°, and 90° were automatically acquired without any polarizing device adjustments. These intensities were then transformed into a phase retardation introduced by a sample, and the resulting phase shift was eventually converted into film thickness. The samples were properly prepared, with pure BK7 substrate being deposited by WO3-, Ta2O5-, and WO3/Ta2O5 films of known thicknesses. The thickness measurement obtained from the proposed system yielded reading errors of 1.3%, 0.2%, and 1.3/2.5% for WO3-, Ta2O5-, and WO3/Ta2O5 films, respectively. The mathematical theory was effectively demonstrated and empirically confirmed. The experimental results show that the proposed setup has a lot of potential for real-time, non-destructive thickness assessment of transparent thin films without the need to modify polarizing device orientations.

Determination of the refractive index profile and surface topography of optically smooth objects using interference of optical vortices

In this paper, we present the results of the propagational dynamics of vortex beams in the scope of their possible applications for interferometric non-contact robust and precision optical surface profilometry with nanoscale longitudinal resolution. The result of coaxial superposition of the reference plane wave with singly charged vortex beams represents a dynamically changing intensity distribution. The nature of this changes, namely, rotational effects of intensity zeros, allows to determine directly the optical path difference which is introduced by the surfaces and internal structure of test object. We have proposed the experimental setup for examination of reflecting and transmitting objects.

Experiences using EN 17037 in evaluation of daylighting of dwellings in Slovakia

The daylighting of indoor spaces depends particularly on the urban and architectural parameters of the building environment. The new standard EN 17037, Daylight in Buildings, has brought several changes and uncertainties in design process of daylighting for buildings. The submitted paper is focused on analysis of the philosophy of the new standard criteria in relation to the daylighting of dwellings along with the criteria that have been used in Central European countries for decades. EN 17037 does not distinguish between differences in the functional use of indoor spaces in terms of daylight provision. The new European standard requires at the half of subjectively determined reference plane to achieve the same value of illumination for half of daylight hours per year for any occupied room. The EN standard does not sufficiently respect the specifics of daylighting of dwellings.

Development of the scheme and method for measuring the characteristics of the friction areas in the car wheel contact

The aim of the research is to develop and implement a scheme and method for measuring the characteristics of static and sliding friction areas in the contact patch of an elastic wheel with a solid support when they appear, exist and disappear. The characteristics are understood as: the relative location of static and sliding friction in relation to the vector of the translational speed of the wheel axis; their size and location in the contact patch when they appear, spread and disappear; the values of the moments on the wheel, corresponding to the appearance, spread and disappearance of static and sliding friction. A scheme and a method for measuring these characteristics have been developed and implemented. The measurements are indirect. It has been experimentally established that, in the general case, the geometric center of static friction in the contact patch moves towards the moment acting in the plane of the wheel rotation relative to the rotation axis by an amount proportional to the moment. The maximum value of this displacement according to the moment that is maximum in terms of sliding conditions, and is one third of the contact patch length for all types and conditions of a solid support. The research results are valid for elastic wheels with a radial stiffness not exceeding 12000000 N/m, the main plane of which is perpendicular to the reference plane. The research results can find application in design modeling of stability and controllability of vehicles.