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Publications - 6278

Dem modeling of crushable grain material under different loading conditions

Majid Movahedi Rad M. Amine Benmebarek

Publication Name: Periodica Polytechnica Civil Engineering

Publication Date: 2021-07-13

Volume: 65

Issue: 3

Page Range: 935-945

Description:

This paper deals with the effect of contact conditions on the crushing mechanisms and the strength of granular materials. The computation of crushable grain material under different loading conditions is performed using 3D model of discrete element method (DEM). The crushable macro-grain is generated from a large number of identical spherical micro-grains which are connected according to the bonded particle model. First, the parameters of the proposed DEM model are calibrated to match the force-displacement curve obtained from Brazilian Tests performed on cylinders made of artificially crushable material. The damage profile right at the point when the force-displacement curve reaches its maximum is seen to replicate the same crack patterns observed in Brazilian test experiments. Then, parametric investigations are performed by varying the coordination number, the contact location distribution, and the contact area. The results show that these parameters play a significant role in determining the critical contact force and fracture mechanism of crushable particles compared to a traditional macro-grain crushing test. Increasing distribution and coordination number of the macro-grain increases particle strength when large area contact is permitted. However, for linear contact area, the effect of increasing coordination number on particle strength is marginal.

Open Access: Yes

DOI: 10.3311/PPci.17948

A Fuzzy Framework for Assessing and Prioritizing Railway Infrastructure Retrofitting against Seismic Hazards – A Case Study

Szabolcs Fischer Amir Hajimirzajan Milad Kazemian

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2025-01-01

Volume: 22

Issue: 4

Page Range: 263-283

Description:

The railway system plays a crucial role in a nation's economy and society, extending beyond mere transportation. In earthquake-prone regions like Razavi Khorasan in Iran, railway infrastructure is highly vulnerable to natural disasters, which can severely disrupt train operations. Ensuring the safety of critical infrastructure, including stations, bridges, tunnels, and railway lines, is essential for maintaining operational integrity and public safety. This study evaluates and prioritizes seismic retrofitting measures for railway infrastructures in Razavi Khorasan. The fuzzy Delphi method is used to gather expert opinions, while the Fuzzy VIKOR method facilitates the prioritization process. Key assessment criteria include seismic intensity potential, vulnerability potential of the zone in terms of distance from the fault, the degree of criticality of the infrastructure in terms of the possibility of continuing transportation operations and the current state of the infrastructure in terms of the state of retrofitting against seismic hazards. The findings reveal critical railway segments that require immediate retrofitting interventions and highlight overall vulnerabilities within the system. This paper underscores the effective application of fuzzy logic methodologies in complex decision making scenarios, offering actionable recommendations to enhance the seismic retrofitting of railway infrastructures.

Open Access: Yes

DOI: 10.12700/APH.22.4.2025.4.16

Soft Magnetic Composites Prepared by 3D Laser Printing

I. Fekete L. K. Varga István Hatos B. Kocsis

Publication Name: Acta Physica Polonica A

Publication Date: 2020-01-01

Volume: 137

Issue: 5

Page Range: 886-888

Description:

In this study, iron and inorganic insulator powders have been used for preparing soft magnetic metal-insulator type composites by 3D laser printing. These samples have been compared with those obtained by traditional pressing and sintering method. Considering the permeability spectra, an increase of the frequency limit has been found for the laser printed samples. In addition to the AC and DC magnetic parameters, the results of XRD and SEM investigations are also presented.

Open Access: Yes

DOI: 10.12693/APhysPolA.137.886

Dynamical system algorithm specification analysis and stabilization

János Botzheim Zhaojie Ju Honghai Liu Cristina Valle Charles C. Phiri Honghai Liu

Publication Name: Lecture Notes in Computer Science Including Subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics

Publication Date: 2017-01-01

Volume: 10462 LNAI

Issue: Unknown

Page Range: 560-569

Description:

This paper investigates approaches to deliberately designing systems whose controllability can be quantified. Preliminary findings of ongoing research are presented on complex dynamical system control algorithms. The specification analysis and quality of the pressure control algorithm applied to a Topical Negative Pressure Wound Therapy device are conducted, with further discussion on self-regulation mechanism and characterization of both the partially observable and partially controllable workspace represented by the negative pressure chamber. Statistical methods are employed to understand the device physics and fuzzy logic and bacterial memetic algorithm are utilised to explore and optimize the existing algorithms and also extract the rule base.

Open Access: Yes

DOI: 10.1007/978-3-319-65289-4_53

Investigation of the Track Gauge in Straight Sections, Considering Hungarian Railway Lines

Szabolcs Fischer Attila Németh Majid Movahedi Rad Henriett Horváth Dalma Németh

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2022-01-01

Volume: 19

Issue: 3

Page Range: 155-166

Description:

In this work, considering the MÁV’s (i.e., the Hungarian Railways) five small and five high-traffic railway lines, the statistical distribution and change of the track gauge parameter were analyzed, under a ten year, on time-series analysis, related to straight track sections. The analysed data, were bottom track gauge measurements, of the FMK-004 and FMK-007 type railway track geometry, measuring and recording car & wagon. Taking into account the railway tracks, the track gauge parameter cannot be controlled and improved upon by large machine methods, but its permitted value depends on the allowed speed (and vice versa). The main independent variables were the elapsed time and the through-rolled axle tons (as a function of time, i.e., the MGT). To generate the statistical analyses, Vaszary-like shape numbers were computed, considering the distribution functions of the measured data series of the track gauge parameter every 25 cm. The authors examined the change of the shape numbers, the average and standard deviation values of the track gauge, and the shape of the distribution functions (skewness and kurtosis properties). In the end, a spectrum analysis of the measured data series was produced. In conclusion, the Authors provide relevant statements regarding the track gauge parameter.

Open Access: Yes

DOI: DOI not available

Stability of fuzzy cognitive maps with interval weights

István Harmati László T. Kóczy

Publication Name: Proceedings of the 11th Conference of the European Society for Fuzzy Logic and Technology Eusflat 2019

Publication Date: 2020-01-01

Volume: Unknown

Issue: Unknown

Page Range: 756-763

Description:

In fuzzy cognitive maps (FCMs) based modelling paradigm, the complex system's behaviour is gathered by the causal connections acting between its main characteristics or subsystems. The system is represented by a weighted, directed digraph, where the nodes represent specific subsystems or features, while the weighted and directed edges express the direction and strength of causal relations between them. The state of the complex system represented by the so-called activation values of the nodes, that is computed by an iterative method. The FCM based decision-making relies on the assumption that this iteration reaches an equilibrium point (fixed point), but other types of behaviour, namely limit cycles and chaotic patterns may also show up. In practice, the weights of connections are estimated by human experts or machine learning methods. Both cases have their own uncertainty, which can be represented by using intervals as weights instead of crisp numbers. In this paper, sufficient conditions are provided for the existence and uniqueness of fixed points of fuzzy cognitive maps that are equipped with interval weights, which also ensure the global asymptotic stability of the system.

Open Access: Yes

DOI: DOI not available

Comparison of the effects and efficiency of vertical and side tamping methods for ballasted railway tracks

Szabolcs Fischer Ulf Gerber Vitalii Kovalchuk Mykola Sysyn Michał Przybyłowicz

Publication Name: Construction and Building Materials

Publication Date: 2022-01-03

Volume: 314

Issue: Unknown

Page Range: Unknown

Description:

The relatively high maintenance costs of the ballast track are related to the short lifecycle of the ballast layer. The current vertical ballast tamping technology (e.g., Plasser & Theurer, Matisa, etc.) causes high ballast destruction and is neither applicable for unconventional sleepers’ designs nor slab tracks. The side tamping method presents an alternative, ballast saving, and sleeper form independent ballast tamping technology. This paper compares the ballast layer compaction and its resistance to permanent settlements accumulation after the vertical and the side tamping methodologies. Scaled models of ballast layer and tamping units and scaled simulation with discrete element method (DEM) were applied for the comparison. In the laboratory tests, the ballast compaction along the sleeper was estimated using the measurements of elastic wave propagation. The settlements resistance for both tamping methods was estimated under the vibration loading. The tests’ results show 5–7% higher compactness of the ballast layer under the sleeper ends for the side tamping method. The settlement intensity of the ballast layer after the vertical tamping is higher than for the side tamping method. In discrete element modeling, the performed laboratory tests were simulated. The compactness of the ballast bed, as well as the residual stresses, were determined in MATLAB. The side tamping technology provided five times higher residual stresses in the ballast layer below the sleeper than in the case of vertical tamping, which can be explained by the more stable and dense layer resulting from the side tamping ensures higher interlocking between the grains. The simulation of the wave propagation shows an influence of the residual stresses on the wave propagation velocities. The simulated wave propagation velocity was more than two times higher for the side tamping than for the vertical one.

Open Access: Yes

DOI: 10.1016/j.conbuildmat.2021.125708

Evaluation of Questionnaires by Combining Fuzzy Signatures, Factor Analysis and Least Squares Method

Dalia Susniene Marta Konczosne Szombathelyi Szabolcs Ramhap Ojaras Purvinis László T. Kóczy

Publication Name: Ines 2020 IEEE 24th International Conference on Intelligent Engineering Systems Proceedings

Publication Date: 2020-07-01

Volume: Unknown

Issue: Unknown

Page Range: 215-218

Description:

A survey based on a standard questionnaire on employee satisfaction was carried out in Hungary. The questionnaire was developed by international university research consortium. The qualitative data were collected from 1159 respondents. The subjective and therefore inexact answers represented in the Likert scale were mapped into fuzzy membership degrees. The article presents a method that consists of the combination of factor analysis and the least square method, applied for developing the fuzzy signature characterizing the employees' behavioural engagement.

Open Access: Yes

DOI: 10.1109/INES49302.2020.9147125

DOES TYPE OF CAPITAL MATTER FOR ECONOMIC GROWTH? A STUDY OF THE CHINESE ECONOMY

Laszlo Vasa Md Abdullah Al Mamun Jin Hu Md Kamal Hossain Jin Hu Md Abdullah Al Mamun Md Abdullah Al Mamun

Publication Name: Investment Management and Financial Innovations

Publication Date: 2025-01-01

Volume: 22

Issue: 1

Page Range: 469-480

Description:

The impact of different types of capital flows on China’s economic growth has been widely studied to determine whether the type of capital significantly affects the Chinese economy. The purpose of this study is to investigate the relationship between long-term capital flows and economic growth in China, considering factors such as Foreign Direct Investment (FDI), portfolio equity, portfolio bonds, and external debt. All secondary data were collected from the World Bank database. The paper also investigates which type of capital flow has the most significant relation with the economic growth of China. A quantitative approach was chosen for the study. Moreover, to overcome the bias output of ordinary least squares, this paper deployed a Two-Stage Least Squares (2SLS) estimation method. This study has found a relatively stable positive relationship between FDI and growth, where the coefficient of 0.9699 indicates that a 1% increase in FDI is associated with a 0.97% growth in Gross Domestic Product (GDP). Similar to FDI, portfolio equity has a positive impact on GDP growth, with a coefficient of 2.1419. In contrast, portfolio bond and debts have a negative coefficient of –1.7752 and –0.2831. These findings contribute to a deeper understanding of China’s development experience, particularly regarding the role of capital flow. The paper explores two key limitations that need to be explored in the future, i.e., the causal relation between each type of long-term capital flow and economic growth, and the impact of COVID-19 on the economic growth relationship.

Open Access: Yes

DOI: 10.21511/imfi.22(1).2025.35