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Publications - 6374

Extension of isothermal time-temperature parameters to non-isothermal conditions: Application to the simulation of rapid tempering

No authors available

Publication Name: Strojniski Vestnik/Journal of Mechanical Engineering

Publication Date: 2010-04-28

Volume: 56

Issue: 2

Page Range: 84-92

Description:

A phenomenological method for constructing non-isothermal, generalized time-temperature parameters (GTT parameters) is presented. An analysis of the relationship between the various traditional isothermal time-temperature parameters has verified that the generalized Dorn-parameter is regarded to be the sole non-isothermal complex parameter to which a rigorous, physically well-founded interpretation is attributed. Possible applications of GTT parameters are illustrated by examples concerning the prediction of hardness change in quenched steels during rapid tempering treatments. © 2010 Journal of Mechanical Engineering. All rights reserved.

Open Access: No

DOI: DOI not available

Evaluation Of hardening performance of cooling media by using inverse heat conduction methods and property prediction

No authors available

Publication Name: Strojniski Vestnik/Journal of Mechanical Engineering

Publication Date: 2010-04-28

Volume: 56

Issue: 2

Page Range: 77-83

Description:

A sequential numerical method for characterization of hardening performance of quenchants applied for steel quenching is outlined here. This novel method is based on the specific processing of measured time-temperature samples performed as a result of cooling curve tests. As a function of surface temperature the heat transfer coefficient, characterises the heat transfer during cooling and is calculated using an iterative inverse algorithm. The heat transfer coefficient is used for the calculation of the microstructural constituents and the hardness profile of cylindrical samples of arbitrary diameters. The hardening performance of the media is evaluated by the estimated hardness of the specimen obtained by heat treatment. © 2010 Journal of Mechanical Engineering. All rights reserved.

Open Access: No

DOI: DOI not available

Impact of Climate Change on Electric Energy Production from Medium-Size Photovoltaic Module Systems Based on RCP Climate Scenarios

Norbert Bozsik András Szeberényi Nándor Bozsik

Publication Name: Energies

Publication Date: 2024-08-01

Volume: 17

Issue: 16

Page Range: Unknown

Description:

The impact of climate change is increasingly evident in various domains today and is gaining prominence in scientific inquiries. Climate change also affects the utilisation of renewable energies. The article examines the effects of 21st-century climate change on the annual electric energy production of medium-sized photovoltaic module systems. The study bases its analysis on three possible scenarios: a pessimistic (RCP 8.5), a less pessimistic (RCP 4.5), and an optimistic (RCP 2.6) scenario. The applied Representative Concentration Pathways (RCP) scenarios were developed by the Intergovernmental Panel on Climate Change (IPCC) to enhance comparability in analyses related to climate change. Compared to older linear models, an innovation utilises a more flexible and multidirectional model. One of the article’s key findings is that, for all three examined settlements, the annual yield of the studied photovoltaic systems will surpass the levels of the base year 2010 by the middle and end of the century. Another significant outcome is that, under the three scenarios analysed, the ratio of annual performance variation to annual global radiation variation shows substantial differences by the middle and end of the century compared to the 2010 baseline. In the optimistic scenario, this ratio exceeds 1, whereas in the pessimistic and less pessimistic scenarios, it falls below 1. This ratio does not directly inform about the annual production—which increases in all cases—but rather about the changes in efficiency. These efficiency changes are influenced by the rise in annual average temperatures and the fluctuation in sunny hours yearly. The third finding reveals that under the climate change pessimistic scenario (RCP 8.5), the efficiency decrease is less adverse than in the less pessimistic scenario (RCP 4.5).

Open Access: Yes

DOI: 10.3390/en17164009

The kinetic energy operator in the subspaces of wavelet analysis

János Pipek Szilvia Nagy

Publication Name: Journal of Mathematical Chemistry

Publication Date: 2009-06-01

Volume: 46

Issue: 1

Page Range: 261-282

Description:

At any resolution level of wavelet expansions the physical observable of the kinetic energy is represented by an infinite matrix which is "canonically" chosen as the projection of the operator - Δ/2 onto the subspace of the given resolution. It is shown, that this canonical choice is not optimal, as the regular grid of the basis set introduces an artificial consequence of its periodicity, and it is only a particular member of possible operator representations. We present an explicit method of preparing a near optimal kinetic energy matrix which leads to more appropriate results in numerical wavelet based calculations. This construction works even in those cases, where the usual definition is unusable (i.e., the derivative of the basis functions does not exist). It is also shown, that building an effective kinetic energy matrix is equivalent to the renormalization of the kinetic energy by a momentum dependent effective mass compensating for artificial periodicity effects. © 2008 Springer Science+Business Media, LLC.

Open Access: Yes

DOI: 10.1007/s10910-008-9458-4

Simulation of 2D inviscid, adiabatic, compressible flows on emulated digital CNN-UM

Sándor Kocsárdi Zoltán Nagy Árpád Csík Péter Szolgay

Publication Name: International Journal of Circuit Theory and Applications

Publication Date: 2009-05-01

Volume: 37

Issue: 4

Page Range: 569-585

Description:

In the area of mechanical, aerospace, chemical and civil engineering the solution of partial differential equations has been one of the most important problems in mathematics for a long time. In this field, one of the most exciting areas is the simulation of fluid flow, which involves for example, problems of air, sea and land vehicle motion. In this paper a CNN-UM based solver of 2D inviscid, adiabatic, compressible fluids will be presented. The governing equations are solved by using first- and second-order numerical methods. Unfortunately the necessity of the coupled multi-layered computational structure with nonlinear, space-variant templates does not make it possible to utilize the huge computing power of the analog CNN-UM chips. To improve the performance of our solution emulated digital CNN-UM implemented on FPGA has been used. Properties of the implemented specialized architecture is examined in terms of area, speed and accuracy. Copyright © 2008 John Wiley and Sons, Ltd.

Open Access: Yes

DOI: 10.1002/cta.565

Machine translation: Can it be a way of communication in a workgroup?

No authors available

Publication Name: IDIMT 2010: Information Technology - Human Values, Innovation and Economy - 18th Interdisciplinary Information Management Talks

Publication Date: 2010-01-01

Volume:

Issue:

Page Range: 387-395

Description:

This paper focuses on the quality of machine translation and post-editing. Machine translation and post-editing proved to be useful in an enterprise environment as a fast and inexpensive way of translation. A software tool has been made to detect the edit distance between an orginal, raw machine translated text and its post-edited version. After detecting the edit operations (insertion, deletion, substitution and move) the editions have been (and will be further) analyzed to attempt to scale these editions according to frequency and gravity, so that later these results can be used for a tool for semi- or completely automatic post-editing.

Open Access: No

DOI: DOI not available

Multi-robot cooperation by fuzzy signature sets

No authors available

Publication Name: IMCIC 2010 - International Multi-Conference on Complexity, Informatics and Cybernetics, Proceedings

Publication Date: 2010-01-01

Volume: 2

Issue:

Page Range: 154-159

Description:

This paper presents a novel method for control cooperating robots without any explicit communication line. Fuzzy signatures are used as complex state description method for intention guessing and action selection. Finally a possible cooperative robot application on a realistic example with missing data components will be shown.

Open Access: No

DOI: DOI not available

On the Use of Quaternions, in the Translated Reference Frame Formalism

Claudiu Radu Pozna Radu Emil Precup

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2023-01-01

Volume: 20

Issue: 6

Page Range: 195-214

Description:

The approaches dedicated to the geometric model of the object, in the object-oriented modeling framework, specific to robots, are focused on the computation of the position of the elements, relative to a global reference frame. One important problem, in this regard, is the direct geometry, which starts with the initial data represented by the generalized coordinates and parameters of each element (in its own reference frame) and calculates the configuration of the structure in the global reference frame. This paper extends the Authors’ geometrical modeling approach, referred to as the translated reference frame formalism, by changing the mathematical apparatus of homogeneous transformations with that specific to quaternions. This new approach has three main advantages over the state-of-the art, namely, it simplifies substantially the configuration modeling, the transformation parameters are intuitive, and the computation is substituted with the operation of choosing a suitable transformation that belongs to a set of six homogeneous transformations. The suggested approach is validated by the computation of the geometric models of two illustrative robotic examples. The source codes are available in a public repository.

Open Access: Yes

DOI: 10.12700/APH.20.6.2023.6.11

Analysis of Plane Poiseuille flow of non-isothermal couple stress fluid between two parallel inclined plates using two reliable methods

Ilker Ozsahin Rashid Nawaz Hijaz Ahmad Alamgeer Khan Muhammad Farooq Faisal Zia Waleed Mohammed Abdelfattah

Publication Name: International Journal of Thermofluids

Publication Date: 2026-01-01

Volume: 31

Issue: Unknown

Page Range: Unknown

Description:

This study is motivated by the need to understand complex thermal and hydrodynamic behaviors of couple stress fluids, which commonly occur in lubrication systems, microfluidic devices, and polymeric material processing. Its significance lies in modeling non-isothermal couple stress fluid flow through an inclined Poiseuille channel bounded by two heated parallel plates, a configuration relevant to advanced heat and mass transfer applications. The aim is to determine the velocity profile, temperature distribution, volumetric flow rate, average velocity, and shear stress for the incompressible fluid. To achieve this, the highly nonlinear coupled ordinary differential equations governing the system are solved using the Optimal Homotopy Asymptotic Method and the Homotopy Perturbation Method, which provide accurate approximate solutions without linearization. The major findings show excellent agreement between the two approaches, confirming their validity, while parametric studies reveal how physical factors such as couple stress effects, plate inclination, and thermal gradients influence the flow. The specific applications of this work include lubrication processes, thermal energy devices, and fluid transport systems requiring precise control of flow and heat transfer.

Open Access: Yes

DOI: 10.1016/j.ijft.2025.101520