Work in unfavorable, changing environmental conditions negatively affects people working on scaffoldings used on construction sites, which may increase the risk of occurrence of dangerous situations. The purpose of this article is to show the scale of temperature changes which workers are exposed to. The paper compares examples of temperature measurements obtained from a metrological station and during tests on scaffoldings located in the Lodz and Warsaw regions. This article also presents the methodology of examining environmental parameters of the surroundings where employees work on scaffoldings. Analysis results show that high temperatures and significant temperature variations frequently occur on the scaffoldings, which leads to a lack of adaptability and consequently to tiredness or decreased alertness. Unfavorable environmental conditions can lead to behaviors which, in turn, can cause accidents.
Polyvinylidene fluoride (PVDF) is one of the most important piezoelectric polymers. Piezoelectricity in PVDF appears in polar b and ɣ phases. Piezoelectric fibers obtained by means of electrospinning may be used in tissue engineering (TE) as a smart analogue of the natural extracellular matrix (ECM). We present results showing the effect of rotational speed of the collecting drum on morphology, phase content and in vitro biological properties of PVDF nonwovens. Morphology and phase composition were analyzed using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR), respectively. It was shown that increasing rotational speed of the collector leads to an increase in fiber orientation, reduction in fiber diameter and considerable increase of polar phase content, both b and g. In vitro cell culture experiments, carried out with the use of ultrasounds in order to generate electrical potential via piezoelectricity, indicate a positive effect of polar phases on fibroblasts. Our preliminary results demonstrate that piezoelectric PVDF scaffolds are promising materials for tissue engineering applications, particularly for neural tissue regeneration, where the electric potential is crucial.
The paper presents analysis of the vibrational environment on scaffoldings. It is based on the results obtained in the project considering workers safety on scaffoldings. The total number of 120 façade scaffoldings was analysed over a period of two years. One of the issues considered in this project was the vibrations influence on scaffoldings and workers safety. The values of natural frequencies were obtained based on in-situ measurements of free vibrations. Analysis of the tests results made it possible to verify the elaborated numerical models. Values of natural frequencies and displacements in mode shaped from numerical modal analyses were compared with test results. Measurements of forced vibrations were also made with various sources of vibrations active at scaffoldings. The detailed numerical dynamic analysis was performed considering excitation forces variable in time. The obtained results were compared with allowable values according to the appropriate Polish standards. Most influential sources of vibrations for human comfort were indicated in the conclusions.
The article presents the results of research, the aim of which was to determine the qualitative and quantitative structure of the causes of accidents that were a result of falling from scaffolding. An original methodology for the classification of accidents with regards to their causes was developed and was based on cluster analysis. An example of using the proposed methodology is provided. 187 post-accident protocols of occupational accidents involving construction scaffolding, which occurred between 2010 and 2017 in selected Polish voivodeships, were analyzed. Afterwards, the matrix of accident causes, for which the calculations were made, was created. Five subsets of accidents were obtained and the accidents were classified to a subset with similar causes.
This paper presents an analysis of natural vibrations of typical façade scaffolding. Three Finite Element Method models with different levels of accuracy of the real structure of the scaffolding representation were used. Modal analysis was carried out for each of these models. The obtained frequencies and mode shapes were compared with the results from the measurements performed on the full-scale scaffolding. The authors of the paper point out the difficulties arise while modelling such structures, and suggest ways to improve the accuracy of scaffolding computational models.
In this study, a simple and effective way to fabricate highly porous scaffolds with controlled porosity and pore size is demonstrated. Ti-7Zr-6Sn-3Mo shape memory alloy fibers were prepared through a melt overflow process. The scaffolds with porosity of 65-85% and large pores of 100-700 μm in size were fabricated by sintering the as-solidified fibers. Microstructures and transformation behaviors of the porous scaffolds were investigated by means of SEM, DSC and XRD. The scaffolds were composed of β phase at room temperature. Superelasticity with the superelastic recovery strain of 7.4% was achieved by β↔α” phase transformation. An effect of porosity on mechanical properties of porous scaffolds was investigated by using compressive test. As the porosity increased from 65% to 85%, elastic modulus and compressive strength decreased from 0.95 to 0.06 GPa and from 27 to 2 MPa, respectively.
The process of cognitive aging in global sense can be characterised by changes of the fluid and crystallised intelligence. In the context of this explanation the basic question is which cognitive functions and regulatory mechanisms play the basic role of the determinants for cognitive aging. Probable, mechanism of associative memory play a central role in top-down direction of cognitive processing. This type of memory connect the resources/networks of long term memory with the current processing in working memory. Another set of mechanisms concerns with bottom-up direction based on procedural memory, which is fundamental for the functioning of the mind as whole (Tulving theory,1985). Unfortunately, our knowledge about associative memory and its relations to working and procedural memory is incomplete and unclear. The importance of associative memory are partly, empirically supported by classic research on decreasing the cognitive components of intelligence aging, since the fluid and crystallized intelligence where discovered (Horn, Cattell, 1967). Changes of the mind functioning and its cognitive growth/aging can be characterised as a complex chain from primary, biologically determined mind, through Piagetian and Vygotsky’s type of mind to relatively balanced mind.
The article analyses the issue of the potential development of theoretical thinking in young children. The context for this discussion is found in the cultural and historical development theory of L.S. Vygotsky which constitutes the basis for assumptions regarding the thinking about development and education of children. It highlights the elementary education stage as a very important area of designing „developmental teaching” as understood by Vygotsky. The article emphasizes the role of an adult who builds the scaffolding for the child’s thinking and acting, and establishes the conditions and teaching environment necessary for the performance of a cognitive process directed at the development of theoretical thinking. In the author’s opinion building the foundation for theoretical thinking will be possible when teachers set „the right developmental and educational tasks” for a child who is constructing knowledge.