Simulation-expertise analysis of ropes used in the horizontal belaying system

This article deals with a dynamic simulation of the movement and fall of persons working at a height, using the rope belaying system. The input data, which are necessary for a created simulation model, were obtained from experimental measurements realised from the concrete belaying system. The simulation analyses were performed for three different values of the rope pre-load level. Consequently, the outputs from the simulations presented in this article were applied in a real design proposal of the rope anchoring arrangement for a horizontal belaying system.Web of Science103675

Vertical forces acting on the lock-off element of the pallet brake system

The paper presents an experimental device that was created in order to obtain the real values of the forces acting in the vertical direction on the lock-off element, the so-called brake body, the 2nd design option. The lock of this design is used in the automated parking garage, designed by KOMA-Industry. s.r.o, to lock the parked vehicles on pallets in the units of the rack parking system. The forces acting in the vertical direction on the body of the fixation lock when pushing the brake pulley into the circular recess in the brake ramp are theoretically calculated for two design variants of the brake ramp used in practice, i.e. "without" and "with" a rounded (filleted) circular recess segment in the brake ramp. The experimentally determined forces acting in the vertical direction on the brake body were determined for two types of compression coil springs with a rectangular cross section of the spring wire.Web of Science14111710

Objective speckle displacement: an extended theory for the small deformation of shaped objects

This paper describes an extended and improved theory of the displacement of the objective speckle pattern resulting from displacement and/or deformation of a coherently illuminated diffuse object. Using the theory developed by Yamaguchi [Opt. Acta 28, 1359 (1981)], extended expressions are derived that include the influence of surface shape/gradients via the first order approximation of the shape as linear surface gradients. Both the original Yamaguchi expressions and the extended form derived here are shown experimentally to break down as the detector position moves away from the z-axis. As such, improved forms of the expressions are then presented, which remove some of the approximations used by Yamaguchi and can be used to predict the objective speckle displacement over a wide range of detector positions and surface slopes. Finally, these expressions are then verified experimentally for the speckle shifts resulting from object translations

Objective speckle displacement resulting from the deformation of shaped objects

This paper describes an extended theory of the displacement of the objective speckle pattern resulting from displacement and/or deformation of a coherently illuminated diffuse object where the influence of the surface shape is included via the linear surface gradients. An experimental system capable of measuring the translational scaling factors, the ratios of speckle shift to object translations, to an accuracy of ± 0.02 and a repeatability of approximately ± 0.008 is described which was used to experimentally measure the speckle shift for a range of detector positions and surface gradients. The original expressions developed by Yamaguchi1 and the new extended expressions2 are then compared with experimental results for measurements on zero surface gradients, i.e. the mean surface lying in the x-y plane. The divergence of Yamaguchi’s expressions from experimental results for off-axis detector positions that was first observed by Světlík3 was confirmed, and the new expressions shown to successfully predict translational scaling factors for off-axis positions. The new expressions are then compared to the experimental results for a range of surface gradient magnitudes and directions, as well as detector positions both on and off-axis, and shown to successfully predict the observed speckle shift.EPSR

New coupled thermoelectric link finite element for FGM materials

The paper deals with derivation process of new FEM equations for steady thermoelectric two-way coupled analysis of link conductor made of Functionally Graded Material (FGM). One example of coupled analysis will be introduced to demonstrate accuracy and effectiveness of our new approach in computer modelling of such systems

Theoretical and Experimental Analysis of Chain Transfer Agents Behaviors in Photopolymer Material

The Non-local Photo-Polymerization Driven Diffusion (NPDD) model indicates how a material’s performance might be improved, and provides a tool for quantitive comparison of different material compositions and to predict their fundamental limits. In order to reduce the non-locality of polymer chain growth (i.e the non-local response parameter, σ) and to improve the spatial frequency response of a photopolymer material, we introduce the chain transfer agent (CTA). In the literature, extensive studies have been carried out on the improvements of the non-local response modifying by the CTA, sodium formate, in the polyvinyl alcohol-acrylamide (PVA/AA) material. In this article, i) based on the chemical reactions of CTA, we extended the CTA model in the literature; ii) we compare two different CTA materials, sodium formate and 1-mercapto-2-propanol without cross-linker in order to obtain the experimental confirmation of the reduction in the average polymer molecular weight is provided using a diffusion-based holographic technique; iii) we examine the non-local responses of several spatial frequencies with the two CTAs. Using the extended CTA model it is demonstrated that the CTA has the effect of decreasing the average length of the polyacrylamide (PA) chains formed, thus reducing the non-local response parameter, especially, in the high spatial frequency case

NPDD model: A tool for photopolymer enhancement

The use of theoretical models to represent the photochemical effects present during the formation of spatially and temporally varying index structures in photopolymers, is critical in order to maximise a material’s potential. One such model is the Non-local Photo-Polymerization Driven Diffusion (NPDD) model. Upon application of appropriate physical constraints for a given photopolymer material, this model can accurately quantify all major photochemical processes. These include i) non-steady state kinetics, (ii) non-linearity iii) spatially non-local polymer chain growth, iv) time varying primary radical production, v) diffusion controlled effects, vi) multiple termination mechanisms, vii) inhibition, (viii) polymer diffusion and ix) post-exposure effects. In this paper, we examine a number of predictions made by the NPDD model. The model is then applied to an acrylamide/polyvinylalcohol based photopolymer under various recording conditions. The experimentally obtained results are then fit using the NPDD model and key material parameters describing the material’s performance are estimated. The ability to obtain such parameters facilitates material optimisation for a given application

Limit states of steel supporting structure for bridge cranes

This paper describes a question of evaluation necessity of bridge cranes using the method of limit deformation state and oscillation damping. The solution was performed by means of theoretical analysis and an experimental verification at the selected bridge crane. The final result sounds that in the case of a correct strength computing of given bridge crane, it is not necessary to also check deformation and damping of oscillation as well.Web of Science10815814

Comparison of the differences in the composition of ruderal flora between conventional tram tracks and managed green tram tracks in the urban ecosystem of the city of Bratislava

Green infrastructure (GI) brings many benefits to urban ecosystems (e.g. better air and water quality) and it presents a helpful tool in the effort to reduce the consequences of climate change. Green tram tracks can be considered to be a part of GI. The presented study is focused on the comparison of the frequency of ruderal plant species, as well as species composition when comparing conventional tram tracks with green tram tracks (with planted succulents and ornamental plants) in Bratislava, Slovakia, Central Europe. This comparison also provides an insight into the changes of the flora of tram tracks over time, as we compare the results of the older research (from the years 2014–2019) with recent research on green tram tracks, which were built in Bratislava in 2020. The data were analysed by cluster analysis, Sign test and Wilcoxon two-sample test in the R 3.5.1. The results revealed significant differences in the composition of flora between conventional tram tracks and green tram tracks. In particular, the total number of species has decreased over time, as green tram tracks host fewer spontaneously growing taxa than conventional ones. The frequency of occurrence of archaeophytes and neophytes has decreased on the strict rail yard (covered by planted succulents) while on the tracksides (covered by non-succulent ornamental plants) it has increased. Green tram tracks deliver positive features to ecosystems, but may also have negative aspects because they present a pool of alien, potentially invasive plants. &nbsp