Search in Publications

Found 6423 publications

Navigating Inflation Challenges: AI-Based Portfolio Management Insights

Tibor Bareith László Vancsura Tatay Tibor

Publication Name: Risks

Publication Date: 2024-03-01

Volume: 12

Issue: 3

Page Range: Unknown

Description:

After 2010, the consumer price index fell to a low level in the EU. In the euro area, it remained low between 2010 and 2020. The European Central Bank has even had to take action against the emergence of deflation. The situation changed significantly in 2021. Inflation jumped to levels not seen for 40 years in the EU. Our study aims to use artificial intelligence to forecast inflation. We also use artificial intelligence to forecast stock index changes. Based on the forecasts, we propose portfolio reallocation decisions to protect against inflation. The forecasting literature does not address the importance of structural breaks in the time series, which, among other things, can affect both the pattern recognition and prediction capabilities of various machine learning models. The novelty of our study is that we used the Zivot–Andrews unit root test to determine the breakpoints and partitioned the time series into training and testing datasets along these points. We then examined which database partition gives the most accurate prediction. This information can be used to re-balance the portfolio. Two different AI-based prediction algorithms were used (GRU and LSTM), and a hybrid model (LSTM–GRU) was also included to investigate the predictability of inflation. Our results suggest that the average error of the inflation forecast is a quarter of that of the stock market index forecast. Inflation developments have a fundamental impact on equity and government bond returns. If we obtain a reliable estimate of the inflation forecast, we have time to rebalance the portfolio until the inflation shock is incorporated into government bond returns. Our results not only support investment decisions at the national economy level but are also useful in the process of rebalancing international portfolios.

Open Access: Yes

DOI: 10.3390/risks12030046

Exploring the impact of compressibility on reconstructed porous materials: A numerical study

H. Szűcs

Publication Name: Journal of Engineering Research Kuwait

Publication Date: 2025-09-01

Volume: 13

Issue: 3

Page Range: 1987-2003

Description:

This study underscores fluid density's significance in CFD simulations for porous materials, addressing its impact on accuracy and computational efficiency. The paper proposes a tailored form of Navier-Stokes equations that accounts for fluid density's influence on CFD analyses of porous materials in industrial contexts, including cases where the solid phase is deformable. Numerical analyses demonstrate fluid density's significance (ρ≠constant) and explore the importance of the energy equation in governing equations. The energy equation is essential in setting up the governing equations, as it calculates thermal characteristic length based on cell temperatures. By examining various porous material samples, the study suggests a streamlined approach: employing a single coupled CFD-FEM simulation to directly determine each geometrical parameter. Additionally, the study investigates the capability to accurately simulate turbulent fluid motion at the pore scale and analyze the flow field characterization within porous media. Computational cost analyses underscore the advantages of coupled simulations, establishing their profitability over separate parameter-specific simulations.

Open Access: Yes

DOI: 10.1016/j.jer.2024.07.018

Comparative Analysis of Field Oriented Control and Direct Torque Control Through Simulation in MATLAB Simulink for an Automotive Drive Motor †

Miklós Gábor Simon Denes Fodor

Publication Name: Engineering Proceedings

Publication Date: 2024-01-01

Volume: 79

Issue: 1

Page Range: Unknown

Description:

Field oriented control (FOC) and direct torque control (DTC) are two strategies used in electric motor control, both with their respective advantages and disadvantages. This paper presents a comparative analysis of these two control methodologies, focusing on their application and performance within a MATLAB Simulink (R2024b) environment for an automotive Permanent Magnet Synchronous Motor (PMSM) drive. The models are created with a focus on realistic drive and test parameters. The simulation results are analyzed to highlight the strengths and weaknesses of each strategy and identify use cases where one method may be superior to the other. In conclusion, this paper contributes to the understanding of FOC and DTC by offering a systematic comparison of their features, performance characteristics, and application scenarios for automotive use.

Open Access: Yes

DOI: 10.3390/engproc2024079033

Environment Protection - Monument Preservation

András Veöreös

Publication Name: Epites Epiteszettudomany

Publication Date: 2023-01-01

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

The preservation of existing buildings is desirable not only for the purpose of saving architectural values, but equally important is that it is an environmentally friendly-environmentally conscious activity as well, since by renovating existing houses less waste is generated, the environmental impact from transport decreases, the material and energy invested in the structures already built do not get lost and no additional energy is needed for demolition.

Open Access: Yes

DOI: 10.1556/096.2023.00081

Intelligent wavelet based pre-filtering method for ultrasonic sensor fusion inverse algorithm performance optimization

György Kovács Szilvia Nagy

Publication Name: Inventions

Publication Date: 2021-06-01

Volume: 6

Issue: 2

Page Range: Unknown

Description:

Certain obstacle mapping applications require the live evaluation of the measured data to prevent collision with obstacles. The fusion of different or similar sensors usually has a high calculation demand, which increases significantly with the area to be evaluated and the number of sensors. In the present considerations, we propose a wavelet-based adaptive optimization method, which can greatly decrease the number of grid points to be evaluated, and thus the necessary computation time. The basis of the method is to use the fact that the areas to be evaluated mostly face a rather small number of obstacles, which cover a smaller percentage of the whole environment. The first step in a pre-filtering process is the determination of the zones where no obstacles are present. This step can already result in a considerable decrease in the computation time, however with the transformation to polar coordinates, the method will not only be more fitted to the problem to be solved, but the area of the evaluation can also be increased with the same number of grid points. As a last step, we applied wavelet transformation to identify the regions of interest, where the application of a refined raster is necessary, and thus further decreasing the number of grid points where the calculation has to be carried out. We used our previously developed probability-based ultrasonic sensor fusion inverse algorithm to demonstrate the efficiency of the proposed method.

Open Access: Yes

DOI: 10.3390/inventions6020030

Investigating the Effect of Gear Ratio in the Case of Joint Multi-Objective Optimization of Electric Motor and Gearbox

György Istenes József Polák

Publication Name: Energies

Publication Date: 2024-03-01

Volume: 17

Issue: 5

Page Range: Unknown

Description:

In this paper, a software framework is presented through an application that is able to jointly optimize an electric motor and a gearbox for the design of a drive system for electric vehicles. The framework employs a global optimization method and uses both analytical and finite element method (FEM) models to evaluate the objective functions. The optimization process is supported by a statistical surrogate model, which allows a large reduction of runtime. An earlier version of this framework was only suitable for electric motor optimization. In the application presented in a previous paper, the motor of a belt-driven electric drive system was optimized. In this paper, the optimization of the same drive system is shown, but now with a combined optimization of a gear drive and motor. The objective functions of optimization are minimizing the total loss energy and the weight of the drive system. The optimization results are compared with previous results to demonstrate the further potential of joint optimization.

Open Access: Yes

DOI: 10.3390/en17051203

Impact of the COVID-19 on the destination choices of hungarian tourists: A comparative analysis

Eszter Szemerédi Marcell Kupi

Publication Name: Sustainability Switzerland

Publication Date: 2021-12-01

Volume: 13

Issue: 24

Page Range: Unknown

Description:

The pandemic caused by the SARS-CoV-2 virus (COVID-19) has transformed the tourism sector to an unprecedented extent, creating new challenges and new development paths. Although the recovery of tourism is fraught with uncertainties, the changes in tourists’ travel habits offer a unique opportunity for tourism to recover in a way that respects the principles of sustainable development. Several international studies suggest that the pandemic has significantly transformed tourists’ travel habits and destination choices, making them more environmentally conscious and shifting their preferences towards inland destinations close to nature. To test these claims, we examined tourists’ destination choices and the factors influencing them in a sample of 500 respondents in Hungary before the pandemic and after the restrictions on travel, businesses, gatherings, and mask requirements were lifted in the summer of 2021. Our results show that there was no significant change in the destination choices of the tourists surveyed. The main influences were the aspects of safety and comfort; the consideration of environmental concerns, despite our assumptions, did not play a significant role.

Open Access: Yes

DOI: 10.3390/su132413785

Study of the antifungal effect of a copper-containing foliar fertilizer

Balázs Ásványi Renato Kalocsai E. Lakatos Viktoria Vona Tamás Szakál Zsolt Giczi

Publication Name: Cereal Research Communications

Publication Date: 2021-06-01

Volume: 49

Issue: 2

Page Range: 337-341

Description:

Winter wheat (Triticum aestivum L.) is one of the most important arable crops. Copper-containing fertilizers are used in crop production to treat or reduce the negative effects of copper deficiency. Various copper compounds are also widely used as effective fungicide agents. The influence of a copper-containing foliar fertilizer prepared from a copper solution and sucrose had been tested on the yield and raw protein content of winter wheat in previous field experiments. In this work, we studied the antifungal effect of this particular foliar fertilizer in an in vitro trial, wherein the fungicide effect on growth and reproduction of specific plant pathogens, i.e., Fusarium graminearum and Drechslera sorokiniana, was evaluated with the agar well diffusion method. The results showed that doses of the foliar fertilizer corresponding to field applications of at least 1 kg ha−1 had antifungal effects, which were significant (P < 0.01) above the concentration level of 3337 mg L−1, corresponding to 2 kg ha−1 application, against both fungal pathogens. A linear correlation (r2 > 0.95) was found between copper concentration and fungicide efficiency in the concentration range studied. The fungicide efficiency of the foliar fertilizer was lower than that of the commercially available copper-oxychloride fungicide. The sole use of the foliar nutrient tested probably cannot replace fungicide treatments. However, in addition to its plant nutrition effect, its antifungal properties should also be taken into consideration.

Open Access: Yes

DOI: 10.1007/s42976-020-00108-y

Representation of loss aversion and impatience concerning time utility in supply chains

János Botzheim Péter Földesi Edit Süle

Publication Name: Smart Innovation Systems and Technologies

Publication Date: 2011-12-01

Volume: 10 SIST

Issue: Unknown

Page Range: 273-282

Description:

The paper deals with the investigation of the critical time factor of supply chain. The literature review gives a background to understand and handle the reasons and consequences of the growing importance of time, and the phenomenon of time inconsistency. By using utility functions to represent the value of various delivery-times for the different participants in the supply chain, including the final customers, it is shown that the behaviour and willingness of payment of time-sensitive and non time-sensitive consumers are different for varying lead times. Longer lead times not only generate less utility but impatience influences the decision makers, that is the time elasticity is not constant but it is function of time. For optimization soft computing techniques (particle swarm optimization in this paper) can be efficiently applied. © 2011 Springer-Verlag Berlin Heidelberg.

Open Access: Yes

DOI: 10.1007/978-3-642-22194-1_28