In this study, a numerical simulation of a single pass welding of two thick-walled pipes with the buried-arc method was performed in order to determine the residual stresses caused by welding. The numerical simulation procedure in the thermal analysis was performed by the element birth and death method while the structural analysis was performed simultaneously, without the application of the element birth and death technique in order to reduce the duration of the numerical simulation. The simulation results were validated by experimental residual stress measurements on the outside surfaces of the welded model using the X-ray diffraction technique. A good agreement between the results of the numerical simulation and experimental measurements was confirmed.

The paper presents the methodology that should be used to optimize hybrid power system configurations, i.e., the chosen microgrid scenario. The methodology was developed with the aim of evaluating the different production capacities of a system and comparing them with alternative connections to the main grid. It has a step-by-step structure and includes part of the steps performed by simulations in a computer program. It provides us with not only a basic but also a representative idea of an actual microgrid configuration, which is further used as support in the system’s design. An algorithm has been developed to check the energy flows and correct the selling price. The program HOMER Pro is used as the program support in performing the hybrid optimization simulation. In the analysis, it was found that the maximum share of generation from renewable energy sources in relation to the power grid is 143%, while the share of renewable energy sources in the generated energy is 65.3%. Greenhouse gas emissions are reduced by 40.75% compared to energy generated only from the power grid. In the optimization process, four configurations of the microgrid model with 990 solutions were taken, all of which are feasible.

In this study, numerical and experimental research of residual stresses was carried out on an I-profile structure model and welded by using the Metal-cored Arc Welding (MCAW) technique. The numerical research was carried out by sequential simulation, using the birth and death element in the thermal analysis, while the same was omitted in the mechanical analysis in order to speed up the calculation process. The measurement of residual stresses was conducted on the outer surfaces of the model at a depth of 0.015 mm below the surface. It was determined that the longitudinal stresses in the weld and its immediate surroundings are tensile, while towards the ends of the model, they change to compressive. Transversal residual stresses exist mainly around the weld itself, and the immediate surroundings and decrease towards the ends of the model. A high agreement between the numerical and experimental results was found.

This paper aims to present the approach to the creation and rendering of a detailed solution for cooling plants including all supporting documents. The paper presents all steps and specific sub steps of the presented approach and the approach has been verified on an example of a cooling plant with water-cooled chillers in the pharmaceutical industry. The authors were motivated to use such approach to find an expedient and high-quality solution for the system architecture. They believe that optimal cooling plant system architecture can be provided by an adequate selection of the required equipment and all system parameters it needs to comply with, through two phases of evaluation analysis, including all supporting technical documents. The approach is based on the designers' engineering knowledge and years of experience in this field. It is based on a so-called Configuration and Change Management (CCM) approach where the required/acceptable solution is provided by configuring the product and changing product properties through several loopback steps. The approach is quite comprehensive and complex; however it produces a satisfactory solution with well presented results, which makes it applicable to the creation of new cooling plants.

The research objective of this article was to develop a multi-attribute approach as a tool for group decision-making processes based on the Modular Function Deployment method (MFD) and fuzzy Analytical Hierarchy Process (AHP) method. The first method is used to develop possible product alternatives. The second is used to evaluate the alternatives and select the best one. This approach allows for decision-makers, who are in different locations, to participate in group decisions over the Internet. It also allows for finite choice alternatives that are best in terms of the overall goal. Various priorities should be considered when determining the overall plan. The resulting complexity of the evaluation task requires an approach that, on the one hand, makes it possible to assign a weighting profile to the individual sub-goals and thus shift priorities, but on the other hand also ensures that very different criteria are considered. Since the Analytical Hierarchy Process (AHP) method can handle complexity, while fuzzy logic allows dealing with uncertainty factors, the proposed method combines these techniques in an integrated approach. The verification of the research results was carried out on a real example of a complex technical system - an air-cooled chiller. According to the first method, two product alternatives were identified, which were then further evaluated using the second method.