A country’s competitiveness depends primarily on its economic development which in turn is affected by a number of factors. Some of these, such as investment, favorable business conditions, legal environment, etc., promote economic development, while others, such as low labor productivity, insufficient staff qualification that fails to meet the requirements of the labor market, etc., slow down the pace of economic development. The latter category describes the phenomenon of the shadow economy (SE). Research into shadow economies is dominated by the analysis of the local impact factors. Nevertheless, the results of such analyses do not reveal the general patterns of the shadow economy, without the knowledge of which it is difficult to develop effective preventive measures. The basic determinants of the shadow economy must first and foremost reflect national economic development, as these particular determinants have the most significant impact on the size of the phenomenon of the shadow economy. National economic development can be expressed by employing various indicators, but recently it has most commonly been expressed by GDP per capita. GDP reflects national competitiveness, integrates a number of domestic factors, and is easily accessible and publicly available in national and international statistical sources. In addition, this indicator is calculated by employing a unified methodology, which makes it universal, allowing the comparison of countries in different situations. As presented in this article, the analysis of the relationship between economic development and the size of the shadow economy allows the division of all the EU member states into characteristic groups by the level of their economic development as well as size of the country’s SE. Our research attempts to reveal the regularity of the above-mentioned relationship: the higher the level of national economic development, the lower the size of the shadow economy.

In the last years, the fact of anthropogenic impact on climate change taking place in the world has become indisputable. Both countries and international organizations have taken steps to reduce GHG emissions, move to a low-carbon economy and implement solutions that reduce human impact on the environment. The EU, by intensifying its activities, has also prepared a strategy known as the European Green Deal. In implementing the EGD, it is important to analyze the impact of energy development in energy-intensive sectors of the economy (industry, transport, agriculture, services and other cores) on atmospheric pollution. Energy development is understood as the energy consumption percentage from all its consumption. In the article, complex correlation–regression analysis was implemented, which included not only energy development impact on the CO₂ emissions level (i.e., production-based CO₂ efficiency), but also its impact on economic growth. The research was conducted for the EU euro area countries. It was determined that the strongest positive correlation is to be found in the transport sector, which implies that with an increase in energy consumption in that sector, production-based CO₂ efficiency is increasing. On the other hand, this increment in efficiency was relatively small and was achieved with the rapid growth of the energy consumption. The implemented research confirmed that the transportation sector is the one which is polluting the atmosphere the most with CO₂ emissions in the Eurozone. The results of the implemented research could be used for the formation of targeted measures for the green growth strategy implementation, and also for ECB and EIB to support “green” projects.

A growing interest in the circular economy, which is seen in the intensification of public discourse, could lead to a danger of blurring the concept and introducing inefficiency in implementing circular economy-based solutions. This study explores the trend in concomitant or accompanying concepts of the discussion about the circular economy themes understanding regarding scientific publications (3,486 publications from Web of Science and Scopus) and popular (non-scientific) domain (represented by 106,504 tweets) in the years 2011–2018. By employing text mining, we calculated the Jaccard similarity index divided into years. The results reveal changes over time in themes accompanying the circular economy discussion and a trend of rising recognition of research-related keywords in general public discussion, with unweighted similarity reaching 39.44% in 2018. Our Twitter keyword research perspective indicates the need to consider the consumer’s role in the development of the circular economy – through keywords that are closely related to consumers’ daily activities.

Some of the issues connected to timber structures are caused by wood-destroying insects. The sterilization of timber elements affected by wood-destroying insects with the help of microwaves removes the deficiencies of other available methodologies. Hence the given paper deals with the experimental sterilization of wood-destroying insect by the application of microwave radiation. It explains the principles behind heating with microwaves and also describes the biological effects of microwave radiation in a simplified manner. The following chapter introduces the equipment required for microwave sterilization to take place and the actual experimental sterilization process. In the final part of the paper are the results of the experimental activity. Throughout the experiments it was found out that microwave radiation seems to be an effective methodology to sterilize wood-destroying beetles. Within the conclusion the intensity of microwave radiation needed for a successful and effective sterilization process is recommended together with the time along which the timber element must have a constant temperature achieved by heating in the primary phase

Multicriteria evaluation methods were applied in Lithuania for the evaluation of construction projects by various aspects more than thirty years ago. It appeared to be a universal technique to reflect the condition of any socioeconomic system quantitatively. Such methods have been used successfully for such kind of problems solving for some tens of years, therefore it is significant to generalize the experience of many years and on its basis to bring to light problematic questions and those ones which should be solved.The critical analysis of the multicriteria evaluation stages revealed the following shortcomings. First, while forming the indexes list, it is a rare case when all possible sources are used. Second, the system of the examined expression indexes is formed on the ground of this list subjectively and without applying scientific methods. Third, the determination of indexes weights is incorrect, especially when a big number of indexes is evaluated. Fourth, there is no solution of the question what multicriteria evaluation method should be applied for a concrete problem solving

The aim of this work was to verify the behavior of hybrid hardwood glue-laminated beams and the possibility of replacing Norway spruce (Picea abies) construction elements, especially in roof and ceiling structures. The samples were six lamellae homogeneous beech (Fagus sylvatica) beams and six-lamellae hybrid beech-poplar (Fagus sylvatica–Poplar spp.) beams; each beam had a cross-section of 60 × 120 mm and was glued with polyurethane adhesive. The samples were loaded using destructive four-point bending tests according to EN 408; the obtained bending strength and modulus of elasticity were statistically evaluated and compared to each other in both types of samples. The results showed that the examined properties of the hybrid beams (with a 16% weight reduction) are comparable to the properties of homogeneous beech glue-laminated beams. Based on the obtained data, the timber elements that are currently used can be successfully replaced by hardwood glue-laminated elements. Based on their higher load-bearing capacity, the cross-section depth can be reduced compared to a larger cross-section depth in spruce beams; this means that hardwood could be suitable in building renovations.