International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

This publication analyses the process of transforming the online economy into a circular one. The focus of the analysis is on the progress of the European Union member states in reducing waste. Member States’ progress towards a circular economy is slow. The circular business model should not be seen as wishful thinking, because it will be crucial for companies in the future. The circular economy is at the heart of the European Green Deal and plays a key role in decarbonisation and achieving climate neutrality by 2050 and in the fight against pollution. Circular economy means smarter use of resources. The circular economy is built using sustainable economic models based on innovation and technology to allow the repeated use of the same resources. Achieving a zero carbon footprint on the natural environment by 2050. is the top priority. This would only be possible if the world moves towards a circular economy, and this is one of the highlights of the Green Deal, while also aiming to increase the competitiveness of the economy.

The surface water resource determination is an important issue related to most reliable water management, which in some districts of Bulgaria in some periods are not enough. In this aspect, the present work is part of the effort to create an operational tool to assess the annual resource. Annual, because this is one of the periods of planning the water use, on the other hand annual averaging significantly simplifies the water balance equation.
There are several methods in world practice for this purpose: modeling the process “rainfall – runoff”; regionalization in typical water quantities depending on physico-geographic factors; balance approach. The first one require a serious resource of information and time, mainly used to analyze the impact of decay factors and climate change rather than on operational purposes. The method of hydrological regionalization is already operational in use, but as far as it is based on registered river flow, it is important to clarify the influence of anthropogenic factors. The water balance method is widely used for the purposes of the Water Framework Directive, both for the assessment of the water bodies’ resources influenced by human activity, as well as for analysis of pressure and water stress, for water economic balances, for the management of water abstractions and river basins. It applies to WB category “lake” – large dams; WB with resource dependent on technological input from dams or derivations; WB with additional flow of water transfer, etc. Vit is one of the main bays in Northern Bulgaria, combining a mountainous, hilly and plain area, on average in area, presenting relatively well the characteristics of formation of the river flow. There are three significant dams, two irrigation systems, derivations and water transfers and a significant number of smaller consumers. In this sense, the basin is chosen as representative, with the opportunity to demonstrate the methods. The balance method is applied to typical sub-basins for the period 2015 -2017.
As a result, a hydrological evaluation of the surface water resource was made for the selected sub-basins based on the registered flow and the water balance assessment of the surface water resource for the same sub-basins. A comparison was made, conclusions were drawn about the advantages and disadvantages of the methods and their applicability in practice.

The intensity of aging and wear of the components /aggregates and assemblies/ of the machines is different and hence the necessity of carrying out repair service interventions has different periodicity and volume.
A model has been developed to optimize the periodicity of maintenance of machine components, taking into account the losses from the underuse of their resource.
The influence of the parameters of the law and the economic indicators on the optimal periodicity of the maintenance was examined at the density of the distribution of work until failure to the Weibull distribution.

Due to volatile and fast moving markets, increasing competition or more complex product solutions, industrial companies are facing increasingly intricate challenges. High energy consumption, emissions output, resource scarcity and waste are just some of the issues enterprises have to manage. Industry 4.0 focuses on an intelligent and interconnected world in which smart factories represent the connection between digital and physical production networks. This interconnection can lead to a variety of environmental benefits, such as consuming fewer resources by means of intelligent connectivity of objects. The energy consumption of a company can be reduced by using start-stop technologies or big data transparency concerning resource and energy consumption to reach optimization potential in production.