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The control of a quadrotor unmanned aerial vehicle (UAV) is a challenging problem because of its highly nonlinear dynamics, under-actuated nature and strong cross-couplings. To solve this problem, this paper aims to propose a robust control strategy, based on a concept of active disturbance rejection control (ADRC).

The altitude/attitude dynamics of a quadrotor is reformulated into the ADRC framework. Three distinct variations of the error-based ADRC algorithms, with different structures of generalized extended state observers (GESO), are derived for the altitude/attitude trajectory-following task. The convergence of the observation part is proved based on the singular perturbation theory. Through a frequency analysis and a quantitative comparison in a simulated environment, each design is shown to have certain advantages and disadvantages in terms of tracking accuracy and robustness. The digital prototypes of the proposed controllers for quadrotor altitude and attitude control channels are designed and validated through real-time hardware-in-the-loop (HIL) co-simulation, with field-programmable gate array (FPGA) hardware.

The effects of unavailable reference time-derivatives can be estimated by the ESO and rejected through the outer control loop. The higher order ESOs demonstrate better performances, but with reductions of stability margins. Time-domain simulation analysis reveals the benefits of the proposed control structure related to classical control approach. Real-time FPGA-based HIL co-simulations validated the performances of the considered digital controllers in typical quadrotor flight scenarios.

The conducted study forms a set of practical guidelines for end-users for selecting specific ADRC design for quadrotor control depending on the given control objective and work conditions. Furthermore, the paper presents detailed procedure for the design, simulation and validation of the embedded FPGA-based quadrotor control unit.

In light of the currently available literature on error-based ADRC, a comprehensive approach is applied here, which includes the design of error-based ADRC with different GESOs, its frequency-domain and time-domain analyses using different simulation of UAV flight scenarios, as well as its FPGA-based implementation and testing on the real hardware.

The purpose of this paper is to explain what determines the influence of reverse logistics onto green supply chain competitiveness and to find out if that influence is always uniform.

The paper contains an empirical research conducted using a survey-based study, which encompassed a sample size of 228 participants and final consumers that have experience in buying/using products derived from the reverse logistics process.

The results indicate that the influence of reverse logistics onto green supply chain competitiveness is dependent on the product return option and is mainly negative with Serbian consumers, since the perceived quality of each of the three return options is considered to be inferior compared to new products.

The study's empirical results show the there is a generally negative perception among consumers regarding the perceived quality of each of the three product return options, thus directly questioning the general justification of using reverse logistics in Serbian business practice. That is a sign for Serbian managers to enhance their efforts to raise future awareness of the green initiatives importance among business partners, but also final consumers.

The study`s contribution is twofold: first, it helps to additionally test the established and known methodology created by Hazen et al. (2011), thus contributing to the practical dimension of international comparability concerning consumer perceptions. Second, the study adds to research by addressing the gap in practical surveys regarding the reverse logistics practices.

The purpose of this study is to show that social relations in a corporate governance platform between members of supervisory boards and between members of supervisory and executive board tiers can serve as an alternative viewpoint for understanding mechanisms of social selection in corporate governance networks. The study shows that through the lenses of social network analysis, it is possible to identify and understand how the process of corporate governance member selection unfolds within companies and how that selection process may have been potentially influenced by the cross-board relations, such as interlocking directorships.

To estimate network parameters and attribute effects of network tie emergence, this study has used exponential random graph models (ERGMs) on corporate governance data of Danish publicly listed companies. Econometric models are applied to estimate parameter statistics which serve further to explain tendencies of tie emergence.

The results of this study reveal that the process of selection of both supervisory boards and executive directors is interdependent. Also, the study showed that board members are more likely to select popular supervisory board members and top managers who have their expertise gained through multiple companies affiliated with multiple industries. However, these conditions for CEO selection apply only to the extent to which they have their experience gained from multiple companies but not multiple industries.

On one hand, this study demonstrates that being a dynamic practitioner who is exposed to diverse corporate environments by being affiliated with different companies belonging to different industries generally increases practitioners visibility in the corporate governance network, and therefore their attractiveness to boards of directors. On the other hand, the results show that the research on board assemblage, nowadays, should be rather observed through the methodology of social network analysis as the method gives an opportunity to understand structures through relations, from which the executive tier should not be exempted as well.

The paper examines the role and significance of gastronomic manifestations in the context of destination branding, within the framework of image transfer mechanisms and the Associative Network Memory Model.

The research was conducted on a sample of 53 gastronomic events in the tourist destination of Vojvodina.

The results indicate that gastronomic manifestations image has a positive impact on the brand image and brand identity of the destination, as well as the destination's overall image. Furthermore, the study found that the food experience has a positive influence on the image of gastronomic events and the destination.

The study contributes to the advancement of research on tourist destination branding.

Reflecting on recent empirical developments as well as insights from regulatory state theory, the paper considers directions in which the regulatory state could develop in the post-COVID-19 era.

This is a de-contextualised analysis of regulatory developments drawing on the prior regulatory state literature and literature on post-crisis responses. Taking into account recent empirical developments related to the COVID-19 pandemic, the paper sets out, in a comparative context, scenarios for the future development of the regulatory state.

Predicting the direction in which the regulatory state will develop is challenging, particularly at this early stage. Yet, we provide a conceptual framework for thinking about possible futures of the regulatory state and how domestic and international factors might mediate these futures.

The paper provides a structured approach to the analysis of the regulatory state bringing together insights from the literature on the regulatory state, public management reform, and global regulatory shifts.

This study aims to explore the use of evolutionary and institutionalization models to understand the technical progression of sustainability in political organizations and their contribution to sustainable effectiveness. It describes the evolution of mass media, political marketing, in the organization’s strategy and design and the methods it is using to institutionalize this political and transition change.

The study describes models of sustainability evolution and political and technical change, in political and social life in transition state Montenegro.

Online and internet presentations of political programs, political blogs, sites that promote the national history and culture of the desired perception – the achievements have already risen in Montenegro in the first decade of the new millennium and beyond. Internet presentation of political subjects are reduced mainly to a brief presentation of history and of political parties, and mostly during the current election campaign, serving to inform the public about the program and promotion announcements.

The findings of this study will help senior executives with responsibility for transition states. The aim of this paper is to show the transformation of the media during the transition period from one political system to another. With the use of descriptive methodological postulates and numerous case studies. With a wealth of facts and examples, which contributes to the originality and value of the article. The significance and originality of this research and article is reflected in a comprehensive and multidisciplinary approach to the transition process and quantitative and qualitative development of the media.

The paper aims to deal with the education for sustainable development (ESD) competences of university educators. The purpose of this paper is to provide a comparative analysis of opportunities for the development of ESD competences in higher education (HE) institutions in Serbia, Croatia and Macedonia. In addition, the paper explores the drivers and barriers experienced in this area using a process-oriented approach.

For the purpose of collecting data, internet and desktop research was carried out, which was then followed by interviews with key respondents and experts in HE. The interviews were carried out face-to-face or via telephone. In addition, information collected from the interviews was compared with both data found in the literature and official documents.

The comparative analysis indicated how specific institutional and cultural contexts affect the development of ESD competences in HE in the region. There were differences but also common opportunities for developing the ESD competences of university educators in the countries analysed. For each country, the drivers and barriers, as well as their relevance, were manifested differently and specific key constructs were identified to explain the implementation process for developing ESD competences of university educators.

This paper tried to respond to this diversity of perspectives, contexts and initiatives and attempted to extract the benefits of different approaches to the ESD professional development of university educators in Serbia, Croatia and Macedonia. It is hoped that this paper will provide valuable insights into the development of ESD in HE and support the development of ESD competences in the region.

This is one of the first papers that provide a comparative analysis of the ESD professional development of university educators in Balkan countries. The value of the paper lies in its potential to help us to understand the role that different drivers and barriers play in different patterns of implementation for developing the ESD competences of university educators.

The purpose of this study is to show which filler metal is the best for hard facing. Because the quality of the surface layer has a great influence on the working life of parts, the purpose was to extend the working life of parts exposed to intensive wear. The tested hard-faced models were made of low carbon steel to save the expensive base metal and to analyze the possibilities of extending the service life of existing structural parts.

Samples were prepared from plates hard faced with various filler metals. Samples were then subjected to experimental testing – testing of tribological properties and hardness and microstructure. Testing was done in conditions similar to real ones – with a sliding speed of 0.25, 0.5 and 1 m/s and with a load of 50, 75 and 100 N and in most rigorous dry conditions. Research was done by using a combination of experimental and theoretical approaches.

The paper shows the results of the experimental testing of four different filler metals aimed for hard facing of parts exposed to highly intensive wear. Results shown that CrWC 600 alloy is the most favorable filler metal for hard facing of parts such as those of construction mechanization and those subjected to intensive abrasive wear at stone mines.

All obtained results are real and fully applicable, as there is a huge industrial need for these types of technologies. With the application of these technologies, beside money savings, the working life of parts can be significantly extended.

The research presented in this paper was conducted because of the lack of results from this area in Serbia and because of the necessity for application of obtained results in companies for road maintenance and stone excavation in the region of Šumadija, Serbia.

The Internet has had an unprecedented impact on the ready availability of information to the public. The conflict in Yugoslavia and Kosovo is an excellent example of how information sources can proliferate around a current, hot topic. However, as is true with any controversial topic, although much of the information available on the Internet is reliable, much of it is propaganda or disinformation. The user must be wary when weighing up the relative merits of these sources. This essay presents a very small, select set of Internet sources devoted to the Kosovo crisis. The author has attempted to present selections that span a range of ideological perspectives reflecting the views of all the major players in the crisis.