bluuebunny/crossref_metadata_2025_split huggingface dataset:
Research on regional difference mechanism of circulation innovation based on panel regression model
Authors: Li Chongyan , Li Xianke 
Published: August 2024

Abstract
The panel regression model is remarkably persuasive in exploring the causal relationship. Therefore, combined with China’s macroeconomic data from 2004 to 2021, this paper uses a panel regression model to reveal the influence mechanism of regional differences affecting innovation flow. Using the improved Theil index to construct panel data of regional differences, this paper explores the reasons for the unbalanced development of technological innovation circulation in China. The empirical results of the fixed effects model show that after controlling for the differences in economic opening environment and firm profit space, the differences in government support and circulation environment significantly affect the regional differences in technological innovation circulation level. This result helps to verify the existence of a “double wheel drive” mechanism in the construction of China’s circulation innovation system, that is, the dual leading role of “effective government” and “efficient market” with Chinese characteristics.
Harnessing RES Potential in Balkan Peninsula
Authors: Vokshi Adi , Zgureva-Filipova Denitza , Markov Detelin 
Published: August 2024

Abstract
The Balkan Peninsula presents a unique and compelling case study for the harnessing of renewable energy sources (RES) to meet growing energy demands sustainably. This paper investigates the current status and future potential of RES deployment across eleven countries in the region: Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Greece, Kosovo, Montenegro, North Macedonia, Romania, Serbia, and Slovenia. In this comprehensive analysis, we begin by providing an overview of the installed capacity of RES in these countries for the year 2021, drawing upon data from reputable sources such as the International Renewable Energy Agency (IRENA) and national energy agencies. Building upon this foundation, we delve into an in-depth examination of the wind and solar energy potential in the region, utilizing geographic information system (GIS) data and modelling techniques to assess resource availability and feasibility. Furthermore, we explore two distinct scenarios for maximizing solar energy deployment in the Balkans. Firstly, we analyse the implications of covering the entire territory of each country with solar panels, estimating the potential electricity production and its relation to current consumption levels. Secondly, we use a more pragmatic approach, focusing on the strategic deployment of solar panels in areas with the highest energy generation potential, while considering land use constraints and environmental considerations. In addition to evaluating the technical and economic aspects of RES deployment, we also quantify the environmental benefits in terms of carbon emissions reduction. By comparing emissions from renewable sources with those from conventional fossil fuel-based electricity generation, we highlight the significant contribution of RES to mitigating climate change and achieving sustainability goals. In conclusion, this paper underscores the immense potential of renewable energy in the Balkans and emphasizes the importance of strategic planning and policy interventions to unlock this potential. By leveraging the region’s abundant natural resources and embracing innovative technologies, the Balkan countries can chart a course towards a more resilient, equitable, and sustainable energy future.
An initial evaluation of humidified discharge cycle for liquid air energy storage
Authors: Borissova Ana , Hristov Kaloyan , Popov Dimityr 
Published: August 2024

Abstract
The research community is becoming more interested in liquid air energy storage among the leading innovative technologies for long duration and grid-scale energy storage. Practical Uses of liquid air energy storage are currently somewhat limited, though, mostly due to the intricate design of LAES plants and the poor “roundtrip efficiency” that is the ratio of the energy recovered from the LAES system during the discharge cycle to the total energy input. With so many components already present in the LAES plant, nearly every research project underway adds even more complexity to the mix. The objective of the work that is being presented aims to increase the use of the heat of compression that has been stored during the charging without adding additional complexity. A mixture of water vapour and air, or humidified air, serves as the working fluid in the presented concept. Thermodynamic performance of the proposed discharge configuration is evaluated and compared on a consistent basis with the stand alone LAES system. The results demonstrate significant increase in the roundtrip efficiency.
Investigation and Mathematical Modelling of Anaerobic Biofermentation of Dairy Cattle Manure: Influence of Addition of Citrus Peel Waste and Lycoperdon Perlatum Spores
Authors: Tzanova Anelia I. , Koparanov Kiril A. , Antonova Elena V. , Minkovska Daniela V. , Antonov Svetlin , Stefanov Bozhidar I. 
Published: August 2024

Abstract
The production of biogas from organic and carbon-neutral sources through biomethanization is essential for achieving the goals of the circular economy and reducing carbon emissions. Crucial for the optimal efficiency of anaerobic biofermentation processes is the influence of organic substrate and the application of methanogenesis enhancement additives. This study explores the possibilities of using a substrate of citrus biomass (waste peelings) for methane production from dairy cattle manure, as well as the influence of an addition of puffball mushroom (Lycoperdon perlatum) spores on the process. Experimental data obtained over a period of 31 days were mathematically modelled using a Verhulst logistic growth model to forecast their future development. The results indicate an inhibitory effect of citrus biomass on methanogenesis processes with a 20% lower yield, but a positive effect of Lycoperdon perlatum spores with nearly double the amount of biogas produced and higher methane content.
Study of the thermal behavior of pellets made from different waste materials
Authors: Mileva N , Radenkov V , Zlateva P 
Published: August 2024

Abstract
The study of waste materials pellets by some thermal analysis methods represents an important area of research and industrial practice. Thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTG) were used for this study. Five different types of pellets were analyzed at heating rates of 5°C/min and 10°C/min up to a temperature of 750°C. The results of this study contribute to a better understanding of the thermal properties of pellets and their behavior under different temperature conditions. This analytical approach not only provides important information for improving the quality and efficiency of pellets but also can be beneficial for optimizing their production processes. The results obtained are expected to be relevant for the development of innovative solutions in areas such as the energy sector, manufacturing, and biomass industries while helping to achieve sustainable resource use and waste reduction.
Simulation of winter heat fluxes through a clay wall with added wheat straw using the finite element method
Authors: Tashkov L , Zlateva P 
Published: August 2024

Abstract
This study focuses on the simulation of heat transfer through a brick wall using an experimental model of unfired ceramic bricks with different additions of wheat straw. A digital model of the wall was created using computer software. Using the finite element method, the behavior of the external brick wall of a residential building is analyzed under changing external temperatures and constant internal temperature. The analysis process is divided into two main parts. The first part covers the stationary problem, which determines the temperature distribution in the wall. In the second part, this solution serves as an initial condition for dynamic analysis. This approach allows investigating how the wall responds to heat by analyzing the dynamic temperature distribution, heat flow and stored energy in the wall. The analyzes will serve to improve the energy efficiency and comfort of residential buildings.
Modelling of hydrocarbon synthesis process using barrier discharge
Authors: Iliev I.K. , Gizzatullin A. R. , Filimonova A. A. , Chichirova N. D. , Malanichev V.E. , Kangalov Plamen G. 
Published: August 2024

Abstract
A computational model for hydrocarbon synthesis by natural gas decomposition using barrier discharge is presented. The model describes the kinetics of the main reactions occurring in the plasma and accounts for the following processes: excitation/relaxation by direct electron impact, decomposition and ionization by electron impact, charge loss due to diffusion to the walls, and 92 chemical reactions. The rates of hydrocarbon production under various discharge parameters and changes in the composition of the starting gas have been calculated. The calculated rates of hydrocarbon production and discharge parameters were correlated with experimental data. The deviation of the calculated electrical parameters from the experiment does not exceed 7%. The model also demonstrated high accuracy in terms of product selectivity and their production rates. The calculations showed a promising result that the synthesis process efficiency depends on the signal shape while maintaining constant power input into the discharge.
A direct coupled photovoltaic - electrolyser system for producing green hydrogen
Authors: Gavrailov D Y , Boycheva S V , Gao Xin 
Published: August 2024

Abstract
This study focuses on the direct coupling between photovoltaic modules (PV) and Proton Exchange Membrane Electrolysers (PEMEC) through data collection to ascertain an optimal and highly efficient operational configuration. The objective is to align the maximum power point line (MPPL) of PV panels with the current-voltage (I-V) characteristic curve of the electrolyser, thereby obviating the need for a DC to DC converter and simplifying the connection while reducing costs and losses. We utilized a polarization curve of Proton Exchange Membrane Electrolyser modelled in COMSOL Multiphysics software and a single PV module with a peak power of 220W. This arrangement necessitates thorough sizing and investigation to achieve maximum system efficiency and green hydrogen production.
Audit of opportunities for improving the energy performance of office buildings by renewable sources
Authors: Penev A D , Rusev S B 
Published: August 2024

Abstract
This paper represents a simple approach to an energy audit for using different types of renewable sources integrated into office buildings. Regression analysis of the results of the simulations with the baseline of the building’s energy consumption and identifying the significant energy use of the buildings were done. It studied various options for building facilities for producing energy from renewable sources on the roof structures and options for a covered parking lot with photovoltaic (PV) panels around the buildings. The technical-economic analysis of the financial indicators of the different types of renewable sources was made and in conclusion were calculated the best payback period (PB), internal rate of return (IRR), net present value (NPV), net present value coefficient (NPVQ), etc.
Model predictive control design for axial-piston pump
Authors: Mitov A , Kralev J , Slavov Ts 
Published: August 2024

Abstract
The article presents model predictive control (MPC) design of the displacement volume control of a variable displacement axial-piston pump. The pump is intended for application in open loop circuit hydraulic drive system. The authors are developed a real-time control system contains two basic components: an electro-hydraulic proportional valve and an industrial controller. The proportional valve replaced the conventional hydro-mechanical controller that changes the swash plate swivel angle, and hence the displacement volume, respectively the flow rate of the pump. The system was developed as a laboratory test bench enabling experimental investigation. The authors are performed system identification based on experimental data and obtained a state space mathematical model of the system. This model was used to synthesize the MPC controller. The behaviour of the controller has been studied both in simulation and in experimental conditions. The analysis of the control performance is carried out comparing transients’ response at different flow rates reference and pump load modes.
Toward detailed modeling of tires with linear elastic rubber compounds using finite element method
Authors: Tchuigwa Baurice Sylvain Sadjiep , Krmela Jan , Pokorny Jan 
Published: August 2024

Abstract
Against a backdrop of increasing depletion of natural and energy resources and worsening global warming, the tire industry, like many other industries, is currently confronted with the pressing need to enhance not only its resilience but also the sustainability and cost-effectiveness of its products through advanced numerical simulations. Numerical simulation is a valuable tool in the tire development process that provides manufacturers with in-depth insights into their products from design to mass production. This paper aims to introduce a detailed finite element-based modeling process for tires that can be used for a wide range of simulations, including steady state, transient rolling, and failure scenarios such as layer delamination, blowout, and part breakage. The selected tire for the implementation in this study is designated 175/75R14 and was modeled in a static loading setup in ABAQUS standard with an implicit scheme considering linear elastic rubber compounds and other assumptions. Unlike the commonly used homogenized approach for reinforced layers, the proposed method takes into account the real physical and mechanical properties of the tire structure. In addition, important information pertaining to the creation of mesh and the interactions between elements is provided. The obtained results align with the assumptions and can serve as a proof of concept for more detailed and advanced tire modeling and enhancement in the future.
A numerical study of the influence of the choice of rubber material behavior on the static response of tires
Authors: Tchuigwa Baurice Sylvain Sadjiep , Krmela Jan , Pokorný Jan 
Published: August 2024

Abstract
Considering the present-day environmental and energy objectives set forth by governments and aiming at minimizing carbon footprints and fuel consumption in the transportation sector, it is of utmost importance for manufacturers to enhance tire design. This is because doing so has the potential to revolutionize the automotive industry by promoting advancements in structural performance and fuel efficiency while reducing environmental impact and ensuring safer, more dependable vehicle structural performance. Moreover, such an approach has the advantage that the choice of model’s features such as the geometry and material mechanical properties, is done in a more detailed manner. The mechanical behavior of rubber compounds used in tire manufacturing has a direct impact on the static as well as the dynamic response of tires in various operating scenarios, such as steady state and transient dynamic. However, in the literature, there is a plethora of works that often consider basic rubber constitutive laws without a consistent study of the impact on the model results. Therefore, this paper proposes a comparative study of the static response of a radial tire using finite element method for different choices of incompressible rubber material behavior ranging from elastic(EL), hyperelastic(HE), visco-hyperelastic(VH) to hyper-pseudoelastic(HM). Simulations of an inflated tire and vertically loaded were conducted in ABAQUS Explicit, and the resulting radial deformation, maximum Von Mixes stress, CPU time, contact patch, and contact pressure were selected as four consistent comparisons. The results show that among the four material cases, the VH and HM material models lead to the most accurate result with a shorter CPU time with the latter. Also, their contact pressure and body stress are higher than those of the elastic and hyperelastic models, and this brings an important solution to the disparity between the calculated and experimentally measured contact pressure in previous works.
Comparison of VVER1000 plant respond during MSLB scenario using TRACE and RELAP computer codes
Authors: Stefanova Antoaneta , Groudev Pavlin 
Published: August 2024

Abstract
This paper presents a comparison of the results from simulation of „Main steam line break (MSLB) “accident using RELAP5/mod3.3 and TRACE50p5 computer codes. The work is based on the VVER-1000 MSLB OECD benchmark. The main purpose of this work was to demonstrate the capability of the TRACE computer code for modelling of 3D thermal hydraulic reactor vessel at the integral VVER 1000 model and to predict correctly the plant respond and spatial disturbance in the reactor vessel. In addition, this investigation was focused on validation of the correct predictability of the important integral parameters in VVER1000 TRACE 50p5 models. The other objectives were to provide the elements for the safety, to validate the safety analysis tools and to improve codes and methods for VVER comprehensive safety assessment. The investigated scenario is a “Main steam line break (MSLB) with inside diameter (ID) 580 mm” in a VVER1000 between the steam generator (SG) and the steam isolation valve (SIV), outside of the containment. This event is characterized with significant spatial effects in the core caused by asymmetric cooling and assumed stuck-out of control rods after SCRAM. One of the major concerns for this case is the possible return of power and criticality after SCRAM, as a result of the reactor core overcooling. The reactor state is at the beginning of 1st fuel campaign. For the purpose of the investigation, the simulation of MSLB accident with RELAP5/MOD3.3 and TRACE50p5 computer codes with modelling of reactor physics using point kinetics has been performed initially. Additionally, the 3D thermal hydraulic reactor vessel model with a point kinetic physics has been developed at the integral VVER1000 TRACE 50p5 model. The newly developed integral model of VVER1000 with 3D reactor vessel of TRACE50p5 has been validated with simulation of MSLB accident by code to code comparison with already validated VVER1000 models of RELAP5/MOD3.3 and 1D TRACE50p5 codes. The comparison between the results predicted by the codes demonstrates good agreement, except some of the parameters. The newly developed integral VVER1000 with 3D vessel model of TRACE50p5 predicts reasonable results. The predicted results by used computer codes demonstrate the stability of the reactor system during the accident progression of “Main steam line break”.
Evaluation of Minor Actinides Build-up in VVER Power Reactors’ Fuel Assemblies
Authors: Mitev M , Filipov K , Nedelchev L 
Published: August 2024

Abstract
The recent developments in the electricity production policies suggest major increase in the share of the nuclear power in the following decades. This trend will pull the nuclear spent fuel storage and handling from the current populist rhetoric to a real political and engineering task to be solved. One of the main challenges is the minor actinides build-up in the fuel during its use in the reactor core. These, together with the plutonium build-up are the main sources of residual heating and radiotoxicity of the spent nuclear fuel. Therefore a long-term solution for their further utilization should be found. The good knowledge of the isotopes content in the spent fuel is vital for investigation of the further handling possibilities. Three fuel assemblies for reactors of VVER type are studied in this paper by means of theoretical modelling. Modern codes and contemporary crossections are used for the calculations. Results for regular and extended fuel cycles are obtained for the minor actinides build-up during their operation. The obtained results provide sound basis for discussion on the further approaches for spent fuel utilization.
Regarding extension of the lifetime of lined clothing
Authors: Atanasova Radka , Pavlova Magdalena 
Published: August 2024

Abstract
This study focuses on sustainable fashion and a method for extending the life of lined garments. Three models of women’s jackets with a classic design, made from high-quality fabric, were selected for the study. The jackets had reached the end of their useful life due to worn lining. In the context of sustainable fashion, a sequence of actions for replacing the lining is proposed. The lining details are unstitched and digitized using a digitizer. This way they are entered into a specialized CAD system for clothing to be used as production patterns for cutting out a new lining. Fabrics with interesting patterns are chosen for the new lining. The resulting garments have a renewed design and are attractive to wear again. A survey confirms that consumers are motivated to wear the repaired garments again instead of throwing them away. This approach slows down the “fast fashion” process and reduces the environmental impact of the clothing industry.
Towards Sustainable Jeans Production: Experimental Evaluation of a Denim Fabric to Abrasion Resistance by Dry Fabric-to-Fabric Rubbing
Authors: Sofronova Daniela 
Published: August 2024

Abstract
Initially renowned for its durability and utility in work clothing, denim fabric has now gained global popularity and is mass-produced worldwide. Unfortunately, despite their widespread use, some denim products lack long-term wear resistance and become textile waste within a short period, deepening environmental pollution. To fight against textile waste and transition to sustainable production methods, stricter regulations regarding the quality of manufactured textile products need to be implemented. The most used test method for evaluation of abrasion resistance applies Martindale tester according to DIN EN ISO 12947-1:2007 and ASTM D4966-22, where a special abradant fabric is used. A more realistic assessment of the abrasion resistance of trouser fabrics, for example, is achieved by performing fabric-to-fabric rubbing. In the paper, these two test methods are performed using 2 types of denim fabrics. One is made of 100% cotton, while the other contains 98% cotton and 2% elastane. Both denim structures showed approximately the same abrasion resistance by fabric-to-fabric rubbing, up to about 80,000 cycles, while the difference between the cycles in the standard test reached about 2 times (18000 and 42000 cycles respectively). The end point of testing was evaluated by the appearance of 2 or more broken threads. The mass and colour loss were also measured as well as the changes in the thickness and air permeability.
Predicting the thermophysiological response in hot environment when using protective clothing
Authors: Angelova Radostina A. 
Published: August 2024

Abstract
The present study investigates thermophysiological comfort and heat stress management in hot working environments when using protective clothing of 1.2 clo. Ten cases are examined with five values of air temperature and two values of air relative humidity. Through an analysis of key parameters such as the Predicted Mean Vote (PMV) index, Predicted Percentage Dissatisfied (PPD) index, climatic condition categories, final sweat rates, and recommended water consumption guidelines, the study examines the interplay between environmental conditions and human physiology. Findings indicate that while protective clothing may offer comfort at lower temperatures, higher temperatures and humidity levels exacerbate discomfort and pose health risks. This research contributes to a better understanding of heat stress management and informs practical strategies for enhancing workplace safety in hot environments.