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This research paper aims to investigate the interdependent influences of barriers to implementing reverse logistics in the broad spectrum of processing activities in the conditions of an emerging economy. An effort was made to approach these barriers (i.e., organizational and management barriers, technical and technological barriers, and economic, financial, and market barriers) based on the relevant literature, predominant attitudes, and experts’ opinions, thus contributing to the body of knowledge in this domain. Determining the intensity of interdependent influences and the importance of barriers for implementing reverse logistics was performed to determine the most important (key) barriers that can be practically applied as guidelines for decision making. The Fuzzy DEMATEL method was used to determine the intensity of these influences on a sample of manufacturing companies in the Republic of Serbia. The results indicate that the most critical barriers to the successful implementation of reverse logistics are a lack of management support and cooperation with scientific institutions and professional associations to acquire knowledge and follow trends in the field.

The study identifies critical factors influencing companies’ operational and sustainability performance utilising fluid power systems. Firstly, the study performs Machine Learning (ML) modelling using variables extracted from survey instruments in the West Balkan region. The dataset comprises 115 companies (38.75% response rate). The survey data consist of 22 predictors, including meta-data and three target variables. The K-Nearest Neighbours algorithm offers the highest predictive accuracy compared to the other seven ML models, including Ridge Regression, Support Vector Regression, and ElasticNet Regression. Next, using a model-agnostic interpretation, we assess feature importance using mean dropout loss. After extracting the most essential features, we test hypotheses to understand individual variables’ local and global interpretation of maintenance performance metrics. The findings suggest that Failure Analysis Personnel, data analytics, and the usage of advanced technological solutions significantly impact the availability and sustainability of these systems.

As a consequence of the application advanced maintenance practices, the theoretical probability of failures occurring is relatively low. However, observations of low levels of market intelligence and maintenance management have been reported. This comprehensive study investigates the determinants of maintenance practices in companies utilising hydraulic machinery, drawing on empirical evidence from a longitudinal questionnaire-based survey across the West-Balkan countries. This research identifies critical predictors of technical and sustainable maintenance performance metrics by employing the CA-AHC (Correspondence Analysis with Agglomerative Hierarchical Clustering) method combined with non-parametric machine learning models. Key findings highlight the significant roles of the number of maintenance personnel employed; equipment size, determined on the basis of nominal power consumption; machinery age; and maintenance activities associated with fluid cleanliness in influencing hydraulic machine maintenance outcomes. These insights challenge current perceptions and introduce novel considerations with respect to aspects such as equipment size, maintenance skills and activities with the aim of preserving peak performance. However, the study acknowledges the variability resulting from differing operational conditions, and calls for further research for broader validation. As large-scale heterogeneous datasets are becoming mainstream, this research underscores the importance of using multidimensional data analysis techniques to better understand operational outcomes.

The research on Bus Fleet Management (BFM) has undergone significant changes. It is unclear whether these changes are accepted as technological change or as a paradigm shift. Perhaps unintentionally, BFM is still perceived as routing and scheduling by some, and by others as maintenance and replacement strategy. Therefore, the authors conducted a Systematic Literature Review (SLR) to overview the existing concepts and school of thoughts about how stakeholders perceive the BFM. The SLR post-study exposed that BFM should be acknowledged as a multi-realm system rather than a uniform dimension of fulfilling timely service. Nonetheless, the work encapsulates BFM evolution which shows the need for the multi-realm research abstracted as "Bus Fleet Mobility Management" and "Bus Fleet Asset Management". The difficulties of transport agencies and their ability to switch from conventional to Zero-Emission Buses (ZEBs) illustrates why we propose such an agenda, by which the research is validated through needs both in academia and in practice.

Computed tomography is a method that has been used for many years in medicine and material analysis, and recently it has also been introduced in dimensional measurements. The method has a lot of advantages compared to other 3D measurement methods, with the largest one being the possibility to perform a non-destructive measurement of an object’s inner geometry. However, it is a complex method with a large number of parameters that influence measurement results. Some of these parameters are image artefacts that occur in the scanning and reconstruction process. An artefact is any artificial feature which appears on the CT image, but does not correspond to the physical feature of an object. In order to achieve metrological traceability, it is necessary to eliminate and minimize the influence of image artefacts on measurement results. This paper presents and explains image artefacts in industrial computed tomography as the consequences of different influence parameters in the CT system.

Part II presents the structural design of a high-capacity adjustable stacker mechanism for thermoforming machines which enables the receival, transport and stacking of cup-like products. It was previously established (please see Part I) that a four-bar linkage mechanism with a one-way clutch is the optimal solution for realizing the intermittent motion of the stacker conveyor. The main objective here is to enable the change of the stacker work parameters, with the goal of changing and adjusting the work stroke of the conveyor. Accordingly, there are two main requirements the solution needs to fulfill. The first is that of the regulation characteristic’s function – the relationship between the change of the work stroke and the change of the regulation parameter, must be linear, and the second is that it allows for regulation within a wide range. Due to this, the adopted solution proposed that two links have variable lengths. The input link should have discreet length values which correspond to different values of the conveyor work stroke, while the output link length should be continuously variable, within a narrow range thus ensuring linear regulation characteristic. Finally, it should be noted that this solution makes the stacker compatible with a wide array of products, which increases the productivity and flexibility, adjusting the stacker to receive a different product can be done quickly and easily and avoiding a halt in the production as it takes less time to adjust the stacker than the thermoforming machine.

The paper presents the type and dimensional synthesis of intermittent mechanisms for use in a thermoforming machine high-capacity stacking apparatus. The aim of this paper is to realize the intermittent motion of the working part of the stacker – conveyor, with a completely mechanical system that should enable the adjustment of the operating parameters of the stacker at a constant motor speed. Mechanical control ensures high positioning accuracy of the product ejection panel, as well as high repeatability of the motion cycle of the conveyor, which is key. Based on the set requirements, the concept of a planar mechanism of simple structure was chosen, which enables oscillatory movement of the output link for continuous motion of the input link, in combination with a one-way clutch (OWC). Four types of intermittent mechanisms have been proposed. However, multiple configurations of the same mechanism type can achieve the same output link motion interval, which is why 3 configurations for each mechanism type are considered, with a total of 4 output link motion intervals, which is 12 potential solutions for only one mechanism type. Afterwards, dimensional synthesis was performed for each type of mechanism by using the optimization method. Based on the analysis of the results, all of the mechanism types are potentially usable. After additional analyses, the optimal solution was chosen.

This paper shows the structure of a mechanical system with 9 DOFs for driving robot eyes, as well as the system’s ability to produce facial expressions. It consists of three subsystems which enable the motion of the eyeballs, eyelids, and eyebrows independently to the rest of the face. Due to its structure, the mechanical system of the eyeballs is able to reproduce all of the motions human eyes are capable of, which is an important condition for the realization of binocular function of the artificial robot eyes, as well as stereovision. From a kinematic standpoint, the mechanical systems of the eyeballs, eyelids, and eyebrows are highly capable of generating the movements of the human eye. The structure of a control system is proposed with the goal of realizing the desired motion of the output links of the mechanical systems. The success of the mechanical system is also rated on how well it enables the robot to generate non-verbal emotional content, which is why an experiment was conducted. Due to this, the face of the human-like robot MARKO was used, covered with a face mask to aid in focusing the participants on the eye region. The participants evaluated the efficiency of the robot’s non-verbal communication, with certain emotions achieving a high rate of recognition.

On average, approximately 22 thousand tons of new lubrication oil were marketed annually in Serbia in the period 2015–2019. Less than 20% of the waste lubrication oil (WLO) generated was treated, whereas the remainder was mostly uncollected or improperly disposed of. The purpose of this study is to examine different WLO management scenarios that could be implemented in Serbia in the future and to quantify their potential environmental benefits. Different WLO treatment processes (namely the re-refining of used oil for base oil recovery, the use of WLO as a substitute to fossil fuels in cement kilns, and the combustion of WLO in waste incinerators with energy recovery) were evaluated using the life cycle assessment (LCA) and ReCiPe 2016 impact assessment methods. The LCA results obtained indicate that no single WLO treatment process consistently exerts diminished environmental impacts according to all the impact categories considered. From a human health perspective, the incineration of WLO in waste incinerators was found more favourable than the other treatment processes considered, whereas the combustion in cement kilns was the most favourable approach with regard to ecosystem protection. In terms of fossil fuel savings, re-refining technologies performed slightly better than the other processes considered. This can be accounted for by significant amounts of marketable co-products generated in the re-refining process, which can be used as a substitute to fossil-based primary products. Furthermore, a total of four possible WLO management scenarios were developed on the basis of the annual quantities of untreated WLO and a mix of treatment options. The results obtained indicate that up to 22,100 t CO2 equivalent and 34,300 t oil equivalent could be saved annually in Serbia provided the most favourable WLO management scenario is considered.

In this multidisciplinary research, an LCA/LCC model is developed for assessing the costs, energy consumption, and greenhouse gas (GHG) emissions during the pump unit lifecycles in drinking water distribution systems (WDS). The presented methodology includes the pump, motor, and variable frequency drive monitoring as a system (pump unit), through their life-cycle stages: the manufacturing stage, the exploitation stage, and the disposal stage at the end of their life-cycle. The developed model also analyses other processes such as the maintenance, testing, and reconstruction of the pump unit. Demonstration of the presented methodology was performed using the pump unit of an operating WDS system in different scenarios, in order to illustrate the proper application of this model. The obtained results show that the application of pump units is justified in terms of energy consumption. The results also show that 93%−94% of the consumed energy and the LCC costs are related to the pump operating costs, while the rest are related to auxiliary operations. The findings show that various countries can have considerably different prices of electrical energy and different GHG emissions that depend on the source of electric energy. The implemented model incorporates some of the symmetries that are commonly found in the mathematical models of water distribution systems. Finally, the results of pump unit exploitation within the WDS have been used to show the impact of such plants on different levels of energy consumption, GHG emissions, and LCC production.