Periodica Polytechnica (Budapest University of Technology and Economics)
Not a member yet
22160 research outputs found
Sort by
Observer-based Implementation of Discrete Gabor Transform
Get PDFThe most commonly used technique in time-frequency analysis is the short-time Fourier transform. It can be used to determine the spectral components as they change over time by computing the Fourier transform of a windowed segment of the signal. A fundamental constraint of this method is that the frequency resolution of the representation in the time-frequency domain will be linear by design. The frequency adaptive nonstationary discrete Gabor transform offers an alternative that does not have this limitation. A Luenberger observer is capable of the implementation of the short-time Fourier transform, and its numerical advantages are already established based on the work of Hostetter and Péceli. Here, we introduce the family of discrete Gabor transforms and its properties along with a constructive method to define such transforms. Furthermore, we show that they are realizable by Luenberger observers which are capable of the error-free reconstruction of the observed signal in finite steps. The dead-beat property is derived for the state variables as well which estimate the transform of the windowed signal
Formation Control Design of Fixed-wing UAVs Based on Model Reference Adaptive Control
Get PDFFormation control is currently a popular field of research due to the increasing application areas of unmanned aerial vehicles. Of concern is the stability of unmanned aerial vehicles (UAVs) formation while tracking especially under the influence of disturbances, and model parameter uncertainty. Since formation of the UAV formation while tracking, especially flying involves a mutual cooperation, consensus-based techniques are more suited such that a group of UAVs are collectively coordinated to perform some tasks. In this paper, a leader–follower formation control of homogeneous fixed wing UAVs based on model reference adaptive control with an integral error control compensation is presented. Model reference adaptive control is powerful and effective for handling uncertain and varying dynamics. This proposed distributed composite control strategy with a directed graph topology, although model-dependent can be effective to suppress disturbances affecting the vehicles, while achieving consensus-based tracking of a reference path. The numerical simulation results given show the applicability of this proposed control strategy
The Comparison of Attributes of Social Intelligence and Machiavellianism in Managerial Work
Get PDFThis paper aims to contribute on a theoretical and empirical level to the solution of questions related to the use of social intelligence and Machiavellianism in the management profession, based on the theoretical treatment of the issue. It sets out to specify mutual differences and relationships relating to selected attributes of methodologies used to determine social intelligence and Machiavellianism in the conditions of managerial work. The research sample consisted of 234 participants (131 women) aged 28 to 40 (mean = 28.72; SD = 6.67). The respondents worked in both the private and public sectors in managerial and non-managerial positions. The data from the respondents were obtained by questionnaire methods, processed and analysed by mathematical-statistical methods at the descriptive and inductive statistical level, as well as more advanced statistical methods. The methods provided data on basic sociodemographic characteristics, social intelligence (MESI questionnaires) and Machiavellianism (VYSEDI). The results of the project contribution brought knowledge at the level of theoretical, empirical, as well as in the practical application of the acquired knowledge. Within the established hypotheses, we found statistically significant differences in selected attributes of social intelligence and Machiavellianism within the managers' workplace setting, as well as differences between managers and non-managers. We also identified mutual correlations between selected attributes in relation to age. On the basis of the presented results, findings and knowledge, as well as the summary and refinement of the results for practical applications, it can be concluded that the goal of the contribution has been fulfilled
Enhancing 3D Precision: Point Cloud Upsampling Methods — A Review
Get PDFEnhancing the resolution of point clouds is crucial in achieving detailed and precise 3D representations for various applications. Factors such as sensor calibration, scanning range, and environmental capability play a pivotal role in determining the overall quality of the captured point cloud data. Moreover, issues related to noise, occlusions, and sensor limitations can further impact the accuracy of the modelling outcome, underscoring the importance of optimizing point cloud resolution. Thus, researchers started to build new architectures with the aim of produce more dense and complete representation with higher resolution. Different methods have been created to achieve successful upsampling, such as interpolation techniques, deep learning strategies, and optimization algorithms. In this paper, we take a closer look at this exceptionally fast-developing field of science. According to this aim, the reader will better understand point cloud upsampling technology
Harmonizing Sustainable Tourism and Mobility: A Framework for Integrated Co-planning
Get PDFThe integration of sustainable tourism and mobility planning is crucial for addressing the complex challenges of environmental conservation, socio-economic development, and community well-being in touristic destinations. This paper introduces the SUSTOURMOB (Sustainable Tourism and Mobility) cycle, a strategy designed to support common sustainable development goals through a transnational approach. Drawing on principles of collaboration and stakeholder engagement, the strategy aims to facilitate co-planning processes that incorporate sustainable mobility solutions into tourism development initiatives. The SUSTOURMOB planning cycle, initially generated for serving Adriatic – Ionian Region destinations, is characterized by iterative analysis, development, testing, evaluation, monitoring, and improvement stages, provides a structured framework for decision-makers to navigate challenges and capitalize on opportunities in the sustainable tourism and mobility sectors. Market trends, technological advancements, policy changes, and crisis management considerations underscore the importance of periodic strategy updates to ensure alignment with evolving circumstances. The strategy's mission statement emphasizes the symbiotic relationship between sustainable tourism and mobility, with a commitment to achieving sustainable development goals. Through ongoing collaboration and adaptation, the SUSTOURMOB strategy offers a pathway towards sustainable tourism development that benefits communities, economies, and the environment
Optimizing Biogas Production from Food Waste and Cow Dung: Impact of Mixing Ratios
Get PDFOptimizing biogas production from organic waste is crucial for sustainable energy and waste management. This study explores the optimal mixing ratio of food waste (FW) and cow dung (CD) in anaerobic digestion (AD) to enhance biogas yield. The 70:30 (w/w) FW and CD ratio achieved the highest biogas yield of 266.4 ± 1.55 mL CH4/g volatile solids (VS) at 32 °C. Both the modified Gompertz (R2 = 0.99) and Logistic Function models (R2 = 0.99) effectively predicted biogas yields, confirming the robustness of this ratio. Fourier-transform infrared spectroscopy (FTIR) analysis indicated significant solubilization of cellulose and lignin, enhancing biogas production. This 70:30 ratio maintained process stability with low volatile fatty acid (VFA) and ammonia levels. The biogas production rate (Rm) ranged from 12.0 to 12.5 mL CH4 with a 7.27-day lag phase, shorter than reported in previous studies. An integrated purification process efficiently removed gaseous pollutants and moisture, increasing methane content by 75%. This enhanced both the yield and quality of the biogas, making it more suitable for energy applications. The study highlights a commercially viable approach for sustainable biogas production, with significant environmental and economic benefits. The optimized co-digestion and purification process offer a scalable solution for renewable energy generation and effective organic waste management
Experimental Verification of a Fuzzy Adaptive Sliding Mode Control Design for IM Speed Control
Get PDFThis article aims to develop a fuzzy adaptive SMC technique that incorporates a variable boundary layer and adaptive switching gain for speed control of a three-phase induction motor (IM) drive. The boundary-layer characteristics are chosen to offer the best compromise between control robustness and chattering elimination or reduction. In addition, this technique offers many advantages for uncertain dynamic systems. The chattering phenomenon, a well-known problem in classical SMC, arises when the switching function attracts the state trajectory toward the sliding surface. Several methods and approaches have been tried to eliminate this phenomenon. We propose here an approach that involves fuzzy logic to avoid this undesirable effect so that the stability condition according to Lyapunov is verified. This fuzzy adaptation system associated with the SMC (FASMC) towards the obtained results forms a robust tool for chattering reduction. Finally, an experimental prototype setup tests the robustness of the fully developed control structure. The experimental results obtained from the FASMC for speed IM drives demonstrate the highest effectiveness and robustness when compared to the conventional SMC controller
An Experimental Investigation of Natural-fibre/Rubber Reinforced Bio-composites under Low-velocity Impact Analysis
Get PDFNatural fibers are renewable, inexpensive, and environmentally friendly; they have become a viable material for a wide range of uses. These composites consist of a natural fibre matrix modified with flax, hemp, sisal, jute, and bamboo. The aim of this present investigation is to explore the existing research, which focuses on examining the influence of natural fibre's absorbed energy and peak force on hemp rubber hemp (HRH), jute rubber jute (JRJ), hemp rubber jute (HRJ), and glass rubber glass (GRG) composite laminates under Low-velocity impact (LVI) analysis. The LVI test results affirmed that the HRH laminates have more energy absorption and elastic energy by 44.34%, 10.6%, and 80% as compared to other configurations due to their stiffness and robustness. The free vibrational analysis shows that the HRH samples have the highest natural frequency of 526.9 Hz compared to JRJ, HRJ, and GRG. The Field Emission Scanning Electron Microscopy (FESEM) discloses the failure mechanisms of the tested samples, including interlaminar failure, delamination, and matrix cracking due to the stress concentration in the impacted region
System-theory Approach to the Operation of Heat Exchangers in District Heating Systems
Get PDFIn this study, the systematic analysis, design, and operation of district heating systems (DHS) are investigated. Particular emphasis is placed on the characterization of the heat transfer processes occurring between the primary and secondary circuits in indirect district heating configurations, with special attention given to the modeling of heat substations. The governing heat transfer equations applicable to heat substations are derived, and both the direct (fundamental) and inverse problem formulations are established. Based on the developed models, operational working points are defined in accordance with varying consumer-side heat demands. The fundamental heat balance equations are derived, input and output variables are identified, and solutions for the output variables are obtained, thereby determining the system's operating point under known boundary conditions. The analysis is limited to steady-state operation and steady-state operating points. Furthermore, an optimization framework is proposed, applicable from both the service provider's and the end-user's perspectives. The presented models are inherently adaptable to both viewpoints
Review of Vehicle Heating and Ventilation Systems Development Techniques
Get PDFThis paper focuses on the potential for improving vehicle heating and ventilation systems. The automotive industry has undergone a complete technological transformation, introducing various environmentally friendly solutions. In particular, electrification poses further challenges in the context of studies to control and improve internal heat flows around the vehicle's energy source, the battery, so optimum power can be obtained with long battery life. The appropriate level of control of air flows and heat losses is a priority. It is therefore addressed in this publication by discussing the battery thermal management systems (BTMSs), part of HVAC systems, that have been recently used to cope with such thermal issues that affect the vehicle's battery. For example, such systems control the battery temperature to be within 15–35 °C for Li-type batteries. Moreover, new measurement techniques for improving vehicles' HVAC systems and their integration into these systems are highlighted and will be considered for further research. For instance, particle image velocimetry (PIV) and background-oriented Schlieren (BOS) measurements have been developed substantially in the last few years. They become more compact and can be integrated into the vehicle's HVAC systems with minimal effect on the process. Furthermore, they produce high data rates and real-time flow field visualization. This paper explores future development directions for automotive heating and ventilation systems