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Found 6319 publications

Stability of Fixed-Point Values in Reduced Fuzzy Cognitive Map Models

Miklós F. Hatwágner Ĺaszĺo T. Ḱoczy

Publication Name: Studies in Fuzziness and Soft Computing

Publication Date: 2021-01-01

Volume: 393

Issue: Unknown

Page Range: 359-372

Description:

The authors have already presented their method for reducing oversized FCM models, and also have analyzed the prediction error of the reduced models. These investigations assumed that models have a single fixed-point attractor. The novelty of this paper is that it deals with the stability behavior of the fixed-point attractor value of original-reduced model pairs and compares the number of fixed-point attractors found, the asymptotic values of the concepts, and also checks if any limit cycles or chaotic behavior occur. The method of comparison and also the first results made with two real-life and one synthetic model are presented and some conclusions are taken.

Open Access: Yes

DOI: 10.1007/978-3-030-47124-8_29

Counterhegemony: Radical Economics and the Appeal of State Socialism in Cold War Era Nigeria (1946–1990)

Adam Mayer

Publication Name: International Journal of African Historical Studies

Publication Date: 2021-01-01

Volume: 54

Issue: 3

Page Range: 377-397

Description:

Normative state socialist economic theory appeared in the mid-1920s with Soviet economist Preobrazhensky. In Nigeria, many economic thinkers were influenced by Soviet and other Eastern European economic theory during the Cold War years. Bala Usman and Segun Osoba focused on the destruction of feudal land law and on delinking from the capitalist world economy; Bade Onimode and Ola Oni on emulating state socialist Eastern European economic theory and practice in an effort to overcome structural underdevelopment; Claude Ake in his Marxist phase made use of the Hungarian economist Tamás Szentes’s heterodox socialist development theory that the latter developed while the two were colleagues at the University of Dar-es-Salaam in Tanzania. Nigeria’s oil incomes were to be used in all these plans to kick-start heavy industry in the country. As the USSR’s alternative globalization path disappeared and then the Nigerian compradores’ share of profits grew by the early 21st century, interest in these radical classics reappeared in Nigeria.

Open Access: Yes

DOI: DOI not available

Experimental Investigation of Vibroacoustic Behaviour of an Automotive Turbocharger with Semi-floating Bearing

Balázs Rácz Péter Sass Márk Pesthy J. Rohde-Brandenburger

Publication Name: Lecture Notes in Mechanical Engineering

Publication Date: 2021-01-01

Volume: 22

Issue: Unknown

Page Range: 245-255

Description:

Due to the strict European emission standards and the constant aspiration for the higher power density, turbochargers became essential components of the modern internal combustion engines. Turbochargers are high-speed operating machines thus the design of the rotor and the bearing system requires special attention. The motions of the rotor are affected by several parameters, such as bearing design, clearances, structure of the surface and also the quality and the physical properties of the used lubricant. If the motions of the rotor are intensive in a wide rotational speed range, the bearing load increases, resulting in a reduced lifespan. The motion of the rotor induces vibrations, which leads to audible noise emission to the environment. In this article, the vibrations of a four-cylinder spark ignition engine’s turbocharger are presented, based on component test-bench experiments. Furthermore, the main vibration components and their influencing factors are briefly introduced. During the experiments, the noise and vibrations of the turbocharger have been measured with different viscosity grade oils from 20 °C to 140 °C inlet temperature. The results showed that the amplitudes of both the synchronous and subsynchronous vibrations changed significantly and the volumetric flow is highly dependent on the temperature. The effect of the changing oil temperature will be analyzed with an emphasis on the subsynchronous vibrations and the possible cause of the phenomenon will be presented. Finding the optimal parameters with the lowest possible vibration response could result in an extended lifetime and provides important information for the balancing process during production.

Open Access: Yes

DOI: 10.1007/978-981-15-9529-5_21

Sternbergia lutea, a new host of Narcissus late season yellows virus

László Palkovics János Ágoston Asztéria Almási Katalin Salánki

Publication Name: Phytopathologia Mediterranea

Publication Date: 2021-01-01

Volume: 60

Issue: 3

Page Range: 403-407

Description:

In autumn 2017, autumn daffodil plants with yellow-green stripes on the leaves were observed at a botanical garden in Budapest, Hungary. Indicator plants wereinoculated, but symptoms did not develop. RT-PCR tests of the indicator plants werealso negative for the viruses. Potyvirus specific ACP-ELISA and RT-PCR were carriedout on the symptomatic S. lutea leaf samples. RT-PCR with universal potyvirusprimers resulted in one, approx. 1700 base pair PCR product. Phylogenetic analysis ofthe nucleotide sequence of the coat protein demonstrated 98.78-99.51% identity withthree Japanese isolates of Narcissus late season yellows virus. While unidentified potyvirusinfection of autumn daffodil has been previously reported, sequence data havenot been published. Therefore, this is the first report of Sternbergia lutea as a host ofNarcissus late season yellows virus

Open Access: Yes

DOI: 10.36253/phyto-12709

FACTORS EFFECTING FEMALE STARTUPPERS IN HUNGARY

Marta Konczosne Szombathelyi Petra Kinga Kézai

Publication Name: Economics and Sociology

Publication Date: 2021-01-01

Volume: 14

Issue: 4

Page Range: 186-203

Description:

The present paper focuses on female startup founders in Hungary. Numerous studies examine female entrepreneurship, but the topic of female startups is a less explored area. The research was carried out in two stages: at first in 2019 through an online survey and in-depth interviews, and then in May 2021 with in-depth interviews due to the delays caused by the COVID-19 pandemic. Mixed research methodology was used and comprised of an online questionnaire administered in startup-themed closed social media groups (n=113) and in-depth interviews among experts and members of the ecosystem (n=7+7). The aim was to conclude how potential female startup founders could be encouraged and what form of support should be given to them, as well as to explore the effects of the Covid-19 pandemic on female startup entrepreneurs. The results show that 70 percent of respondents have their own business, these were set up by both sexes between the ages of 24 and 35. The respondents mostly use equity when starting their businesses. Although the proportion of women among startup founders is very low, a positive entrepreneurial attitude can be observed among them. The startup ecosystem is centralised in Hungary; it is only emerging in some major university cities outside the capital. The strengthening role of startup communities and social media is unquestionable. Furthermore, the results reveal limiting factors, especially complex ones hindering female start-ups, which can typically be traced back to family and social reasons. To overcome these obstacles governments should continue facilitating startup development. The pandemic was considered as an opportunity to promote new ideas and features, concentrate on design and finetune their startup businesses.

Open Access: Yes

DOI: 10.14254/2071-789X.2021/14-4/11

Design and Testing of a Water Injection System of a Turbocharged Spark Ignition Engine in Testbench Environment

Máté Tóth Balázs Rácz Attila Gyuris Péter Sass J. Rohde-Brandenburger

Publication Name: Lecture Notes in Mechanical Engineering

Publication Date: 2021-01-01

Volume: 22

Issue: Unknown

Page Range: 321-333

Description:

In the scope of this article, the design and testing of a water injection system applicable for a spark ignition engine are presented. Increasingly stringent emission standards within the framework of EURO7 require either directly or indirectly the internal combustion engines to be optimized across the entire field of an engine map, therefore they must comply with the emission standards at each operating point. The greatest challenge is expected to be the Lambda = 1 operation on the full field. The conversion efficiency of the exhaust gas after treatment systems is the highest at this point, therefore it is foreseeable that no deviation can be made. As a result, fuel enrichment for performance enhancement and to protect components against thermal load will not be tolerated, so the resulting thermal loads will need to be reduced in other ways. It is possible to reduce the excess thermal loads by using water injection. Evaporation of water in the intake system and combustion chamber takes off heat and the temperature of the contacting components and fluids decreases. The affected components include pistons, combustion chamber, cylinder head, exhaust valves, exhaust manifold, turbine wheel, turbine housing, and as a medium, the temperature of the intake air. Reducing the temperature of some components is important in the aspect of mechanical strength, while for some components the knock limit can be extended. This article presents the detailed design process and testing phase of a water injection system. An important aspect in system design is compatibility with different engine layouts in a cost-effective manner. Injector nozzle testing also includes analysis of mass flow, dispersion and spray pattern. The scope of the work is the implementation of a water injection system, which is capable of performing measurements in testbench environment at the Department of Internal Combustion Engines and Propulsion Technology of Széchenyi István University. The result of the measurements is the successful cylinder selective application of water injection to the intake system, whereby the addition of water reduces the temperature of the intake air and the exhaust gas, which can be reduced to standard calibration temperature in Lambda 1, without fuel enrichment.

Open Access: Yes

DOI: 10.1007/978-981-15-9529-5_29

Investigation of the influencing soil parameters on the air entry values in soil-water characteristic curve of compacted heaving soils

Elizabeth Theron Armand Augustin Fondjo R. P. Ray

Publication Name: Civil Engineering and Architecture

Publication Date: 2021-01-01

Volume: 9

Issue: 1

Page Range: 91-114

Description:

The air-entry value (AEV) is a fundamental parameter of the soil-water characteristic curve (SWCC). AEV is the minimum matric suction value required for entry of air into soil voids. The primary objective of this research work is to assess the impact of geotechnical index properties, swelling properties, mineral composition on AEV of compacted heaving soils, and discuss how they affect AEV. Soil properties were investigated through lab tests such as grain size distribution (GSD), specific gravity, Atterberg limits, linear shrinkage, free swell index, free swell ratio, X-ray diffraction, compaction test, and soil suction measurement. SWRC Fit program was used to perform non-linear fitting of the SWCC based on models VG, DB, FX, LN, and BL. Surface plot of data was used to characterize the impact of soil properties on AEV. It was observed that AEV is ranging from 10 kPa to 20.20 kPa, models DB and BL gives the best fitting SWCC. The percent of smectite mineral exhibits a significant impact on AEV. Swelling properties such as free swell index and free swell ratio influence the AEV with a respective determination coefficient of 85.72%, 88.68%. The plasticity index, linear shrinkage, specific gravity, and dry unit weight impact the AEV with a respective determination coefficient of 95%, 95.45%, 90.43%, 94.29%. The fine-grained content, clay fraction, void ratio, and water content influence the AEV with a respective determination coefficient of 97.95%, 84.89%, 80%, 94.31%. The finer the soil, the higher the AEV. The activity of clay and percent of illite mineral exhibit a marginal effect on the AEV.

Open Access: Yes

DOI: 10.13189/cea.2021.090108

Alternative Propulsion Buses in the Metropolitan Public Transport

István Lakatos Dániel Pup Andor Nagy Ferenc Szauter

Publication Name: Lecture Notes in Mechanical Engineering

Publication Date: 2021-01-01

Volume: 22

Issue: Unknown

Page Range: 49-66

Description:

The lecture is analysing the possibility of an optimal energy mix through the example of a Hungarian metropolis. Using the city bus routes, we analyse and compare the traditional Diesel, CNG, and electric propulsion. An optimal energy mix is provided by using SWOT analysis.

Open Access: Yes

DOI: 10.1007/978-981-15-9529-5_5

Simulations of poroelastic materials in a complex acoustic system using frequency-dependent parameters in the mid-frequency range

Dániel Feszty Janos Kun

Publication Name: Proceedings of Inter Noise 2021 2021 International Congress and Exposition of Noise Control Engineering

Publication Date: 2021-01-01

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

Efficiency requirements prompt manufacturers to develop ever lighter acoustic packages in vehicles. Poroelastic materials are essential to achieve the desired interior noise level targets and thus the simulation of their effects is of utmost importance in NVH analyses. However, it is challenging to achieve good validation between finite element method (FEM) based simulation results and measurements in the mid-frequency range (400-1000 Hz). One possible reason could be the lack of using frequency-dependent Biot-paremeters describing the poroelastic materials (PEM) characteristics of trims. The present research aims to employ frequency-dependent Biot-parameters for the PEM materials to investigate the acoustic response of a scaled car-like steel structure composed of flat plates and U-section stiffeners enclosing an air cavity. Porous acoustic material is applied to the walls of the cavity. The focus of the study is to understand the effect of applying frequency-dependent Young's modulus and damping values for the PEM parameters in the 100-1000 Hz range. Simulation results obtained from ESI VPS FEM solver are compared with measurements, with particular focus on the interior sound pressure levels. The simulation methodology, including discretization techniques, structural damping and fluid damping applications are described in detail.

Open Access: Yes

DOI: 10.3397/IN-2021-2869