There is no consensus among researchers on the biomechanics of wheelchair propulsion concerning the bilateral symmetry assumption. On one hand, the assumption is advantageous, as it allows for the simplification of data collection, processing, and analysis. It also facilitates the modelling of wheelchair propulsion biomechanics. On the other hand, there are reports that the validity of the bilateral symmetry assumption is unclear. Therefore, the present study aims to analyse the biomechanics of wheelchair propulsion for side-to-side differences. Motion capture techniques based on ArUco with the use of OpenCV libraries were used for this purpose. The research was carried out on a group of 10 healthy and inexperienced volunteers with a semi-circular propulsion pattern, who declared right-handedness. The tests were carried out on a hard, even surface, without an additional load, within the frequency of the propelling phases dictated by sound signals, amounting to 30 BPM. The positions of markers on the hand, elbow, and wrist were analysed. As a result, a cloud of points of the markers’ displacement on the sagittal plane in the propulsion push progress function was obtained. The results were averaged with a breakdown by the right and left hand for individual persons, but also for the entire group of volunteers. A comparative analysis and the mutual position of the confidence intervals of the determined mean values were also performed. The collected data suggest that the mean values for individual participants show greater asymmetry than the mean positions of the markers for the entire group of participants. Therefore, the assumption about the symmetry of upper limb propulsion may not be true when analysing the biomechanics of propulsion for individuals, although it may be accurate when analysing larger groups of persons (participants free of upper-extremity pain or impairment).

Objectives The paper presents preliminary results on the assessment of algorithms used in image processing of the grain damage degree. The purpose of the work is developing a tool allowing to analyse sample cross-sections of rye germs. Methods The analysis of the grain cross-sections was carried out on the basis of a series their photos taken at equal time intervals at a set depth. The cross-sections will be used to create additional virtual cross-sections allowing to analyse the whole sample volume. The ultimate plan is to generate two cross-sections perpendicular to each other. Based on volumetric data read from the sample section, a three-dimensional model of an object will be generated. Results The analysis of model surface will allowed us to detect possible grain damage. The developed method of preparing the research material and the proprietary application allowed for the identification of internal defects in the biological material (cereal grains). Conclusions The presented methodology may be used in the agri-food industry in the future. However, much research remains to be done. These works should primarily aim at significantly reducing the time-consuming nature of individual stages, as well as improving the quality of the reconstructed image.

The aim of this research was to define the compression strength of polylactic acid bolts produced using the fused deposition modelling method. In accomplishing this, static and cyclic compression tests for different metric thread sizes were carried out in accordance with ISO 4014. Tests were conducted on M42, M48, M56, M60, and M64 threads, while samples with three different types of pitch—one nominal and two fine threads—were prepared for each diameter. Standard ISO 604 for defining the compression modulus Ec was implemented as the test basis. Accordingly, the mean compression modulus value Ec for all measurements was 917.79 ± 184.99 MPa. Cyclic compression tests were then carried out on samples with the M64 × 4 thread. Fifty thread loading cycles were carried out for each variant to obtained different strain amplitude values and strain frequencies. Our work indicated that the values of the storage modulus defined in cyclic tests E′ increased, while the values of the loss modulus E″ decreased when the value of the strain frequency increased. We found it not possible to determine the nature of the changes in the value of the storage modulus E′ in the function of the strain amplitude. We did, however, observe an increase in the value of the loss modulus E″, together with the increase in the tested range of the strain amplitude. The determined mechanical values can be therefore be used for designing threaded connections made of polylactic acid using the fused deposition modelling method.