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

Analyzing the current state of the road infrastructure in Bulgaria, it should be emphasized that it is the result of the long-term preferential and large-scale industrialization of the national economy. This policy, until the beginning of democratic changes in the country, put the development of the road infrastructure on the back burner, due to the limited resources and the set priority. Investment during the transition years is characterized by irrationality, mainly due to the lack of a justified, detailed developed and provided with financial resources long-term plan in this area. Bulgaria’s accession to the European Union led to a rethinking of the content of the state infrastructure policy, a change of views and the need for rapid integration of the national transport system with the European one. The development of the transport infrastructure plays an important role in strengthening the ties between European countries and in the inclusion of new member states of the European Union. The country’s road infrastructure affects the competitiveness, economic growth and employment of the working population. This report examines and analyzes the changes and modifications that have occurred in the structure, condition and density of Bulgaria’s road infrastructure for the period 2007 – 2024. The main goal is to derive recommendations and guidelines for the future sustainable development of the country’s road network based on the analysis of the development of the road infrastructure during the first eighteen years of Bulgaria’s membership in the European Union.

The work presents a study of an upper limb exoskeleton designed for rehabilitation and training. While in the first stages of rehabilitation, when the patient is unable to move alone, the exoskeleton must be rigid, in the next stages it should be able to respond to any movement made by the patient. The key feature here is transparency: the robot must be able to “hide” if the patient is able to make the movement without assistance. The aim of the work is to identify and evaluate an appropriate solution of the upper limb exoskeleton that provides transparency and natural safety on the one hand, and force impact and performance on the other. In the paper, the mechanical model of the exoskeleton was shown. The mechanical structure is similar to the structure of the human arm. Through the kinematic model, the direct and inverse tasks of kinematics are solved using the Octave matrix software. The upper limb exoskeleton is designed as a haptic device that can perform tasks in virtual reality. Simulations of the interaction force between the patient and the exoskeleton were conducted also using the Octave software. Here, an assessment of the interaction force was made as a result of the exoskeleton passive impedance and the active control of the exoskeleton. Finally, conclusions and development recommendations are given.

This study presents the rehabilitation project for the Francis turbine runner of Kepez 1 Hydroelectric Power Plant (HEPP) in Antalya, Turkey. The aim of rehabilitation is to increase the power and efficiency of the plant and solve the existing problems such as cavitation. Initially, the head and flow rate of the turbine are estimated. Within the scope of this study, the design parameters which are necessary to obtain better cavitation characteristics and higher power and efficiency, are determined and computational fluid dynamics (CFD) is utilized to design a new runner geometry for better performance. The results of the CFD simulations are compared to the simulation results of the existing runner geometry which was obtained from the plant and scanned using laser scanning. The results show that cavitation characteristics and the efficiency, as well as the power of the HEPP are improved.