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Publications - 6374

Meshfree vectorial interpolation based on the generalized stokes problem

Csaba Gáspár

Publication Name: Lecture Notes in Computational Science and Engineering

Publication Date: 2011-01-01

Volume: 79 LNCSE

Issue: Unknown

Page Range: 65-80

Description:

A vectorial interpolation problem is considered. In addition to the interpolation conditions taken at discrete points, a global, divergence-free condition is also prescribed. Utilizing the idea of the multi-elliptic interpolation, the divergencefree interpolation problem is converted to a generalized Stokes problem. To numerically solve this new problem, an Uzawa-type method and the method of fundamental solutions are proposed. In the second method, a linear system with large and dense matrix is to be solved, while in the first method, this problem is avoided. © 2011 Springer-Verlag Berlin Heidelberg.

Open Access: Yes

DOI: 10.1007/978-3-642-16229-9_4

Developing fuzzy cognitive maps for modeling regional waste management systems

Claudiu Radu Pozna Adrienn Buruzs Laszlo T. Koczy

Publication Name: Civil Comp Proceedings

Publication Date: 2009-01-01

Volume: 92

Issue: Unknown

Page Range: Unknown

Description:

Sustainable waste management systems necessarily include environmental, economic, social, institutional, legal and technical aspects. As a result of the incompleteness and multiple uncertainties occurring in sustainable waste management systems, we propose the use of fuzzy cognitive maps (FCM) to support the planning and decision making process. It is obvious that uncertainties involved with waste management represent vagueness rather than probability. Fuzzy sets and fuzzy logic are suitable to construct a formal description and a mathematically manageable model of systems and processes with such uncertainties. In the research described in this paper the FCM model of the Gyor RWMS is established and implemented in such a structure that its parameters and weights were flexibly variable. By observation of the model and its time dependent behaviour we determined under what conditions the long-term sustainability of a regional waste management system could be ensured. In this paper, the interpretation of the results obtained by the FCM model for the actual waste management system are presented. © Civil-Comp Press, 2013.

Open Access: Yes

DOI: DOI not available

Conservative Method for the Calculation of Thermal Forces in Reinforced Concrete Tunnel Wall During Fire

Éva Lublóy Zoltán Major János Szép

Publication Name: Advances in Transdisciplinary Engineering

Publication Date: 2024-01-01

Volume: 59

Issue: Unknown

Page Range: 455-463

Description:

This article builds on the author's existing knowledge of the heating of reinforced concrete tunnel linings and deals with the structural analysis of tunnel linings under fire exposure. Due to space constraints, the issue of designing for earth pressure and surface loads is not address. Since the analysis of thermal stresses due to restrained deformations is insufficient in the available literature, we complement the existing theoretical knowledge with the knowledge provided by the relevant standards for reinforced concrete tunnel linings. In addition, we add our own individual reflections to the theory where we have identified gaps. In determining the additional stresses due to inhibited thermal expansion, we use a numerical model based on our own ideas. The reason for this is that the heating of reinforced concrete tunnel lining during fire is extremely uneven and it is almost impossible to take this into account in the finite element programs commonly used. The other important reason is that this uneven temperature change that causes the colder zones of the wall to inhibit deformation. Thus, a solution implemented in MS Excel environment is presented, which allows an approximate accurate determination of the force effects due to inhibited deformation. The solution used and the values proposed are based on the authors' individual ideas and are not the result of an accepted professional consensus. In all cases where more precise data are required, it is recommended that a more accurate test be carried out. Advanced finite element modelling can provide the necessary support for designers and experts.

Open Access: Yes

DOI: 10.3233/ATDE240579

An application of the greedy heuristic of set cover to traffic checks

Pál Pusztai

Publication Name: Central European Journal of Operations Research

Publication Date: 2008-12-01

Volume: 16

Issue: 4

Page Range: 407-414

Description:

Let us suppose that X is a given, finite, not empty set and F is a given collection of subsets of X such that their union equals X, in other words F covers X. Set cover is the problem of selecting as few as possible subsets from F such that their union covers X. Max k-cover is the problem of selecting k subsets from F such that their union has maximum cardinality. Both problems are NP-hard. There is a polynomial time greedy heuristic that iteratively selects the subset from F that covers the largest number of yet uncovered elements. We implemented this greedy algorithm to support the planning of a checking system that is aimed to check the vehicles in a road network. We would like to answer such questions: - How many and which links are sufficient to check a given percentage of all traffic flow? - What percentage of traffic can be checked with given links? This paper defines the necessary data and basic knowledge, gives algorithms to answer the previous questions and also shows the results of an implementation in a road network that contains about 11,000 junctions, 3,000 origin-destination junctions and 26,000 links. © 2008 Springer-Verlag.

Open Access: Yes

DOI: 10.1007/s10100-008-0067-x

On the measurement and evaluation of bass enhanced in-ear phones

Gyorgy Wersenyi

Publication Name: 20th International Congress on Acoustics 2010 Ica 2010 Incorporating Proceedings of the 2010 Annual Conference of the Australian Acoustical Society

Publication Date: 2010-12-01

Volume: 4

Issue: Unknown

Page Range: 2849-2854

Description:

Measurements of the transfer function of headphones and earphones are made on dummy-heads or on ear simulators. This paper introduces measurement problems of newly designed in-ear phones, often called as micro-driver equipment. These earphones have smaller transducer diameter and are equipped with rubber or spongy material to fit in the ear canal. This coupling may create an increased sound isolation, less sound pressure and a better low frequency transmission to the eardrum. The paper presents subjective evaluation of listeners who evaluated five different kinds of in-ear phones as well as transfer function measurements using a dummy-head. Measurement problems are highlighted pointing on new aspects of a revised dummy-head standard. Copyright © (2010) by the International Congress on Acoustics.

Open Access: Yes

DOI: DOI not available

Preparation of soft magnetic composite from Fe-6.9wt%Si by different heat treatment strategies.

Ibolya Zsoldos L. K. Varga B. Kocsis

Publication Name: Iop Conference Series Materials Science and Engineering

Publication Date: 2020-08-25

Volume: 903

Issue: 1

Page Range: Unknown

Description:

Present study investigated the effect of isothermal heat treatment strategies between 800 °C and 1150 °C on the magnetic properties of toroidal samples made from Fe-6.9wt%Si powder. The samples were prepared by classical powder metallurgy method since the classical sheet forming methods no longer work with the high silicon content. Our results presented here are part of a series of comparative experiments where we study the effectiveness of the insulating layers created during and before the compacting of soft magnetic composites (SMCs). Our goal was to create a soft magnetic composite made of ferromagnetic and inorganic insulating material with a frequency limit already in the megahertz range and a Snoek limit of few gigahertz. In the case of samples made from Fe-6.9wt%Si powder, the computed tomography results showed that significant porosity is to be expected after pressing. Its positive effect occurred during the heat treatment in the atmospheric agent, where silicon is precipitated and deposited on the surface of the particle. This coating is an electrically insulating layer at the grain boundaries. Depending on the heat treatment strategy, 1 or 2 ferromagnetic phases were observed. The frequency limit approached the target values, but due to the low value of static permeability, the Snoek limit did not reach the gigahertz range. However, there is a significant improvement in magnetic properties compared to the heat-treated samples in a protective gas.

Open Access: Yes

DOI: 10.1088/1757-899X/903/1/012042

Approximation of the stiffness of laminate stacks of electric motors subjected to cyclic loads

Dániel Feszty Balázs Pere Viktor Szabó

Publication Name: Materialpruefung Materials Testing

Publication Date: 2023-08-01

Volume: 65

Issue: 8

Page Range: 1202-1208

Description:

Electric motors in automotive applications are subjected to high thermal and structural loads, while having strict requirements regarding dimensions, mass, and costs. The design of such motors requires sophisticated simulation models. The laminate stack in the rotor of such a motor is made of steel sheets and behaves transversally isotropic: the radial stiffness is equivalent to steel, and in the axial direction, it has a highly progressive nonlinear stiffness characteristic. The loading and unloading stiffness curves change from cycle to cycle when subjected to repetitive loads. In this paper, the usage of a single approximating curve to describe the longitudinal stiffness of the laminate stack is proposed. This approximation can be used in FEM models to reproduce the structural nonlinear behavior of such a laminate stack using a simpler approach than implementing the full loading and unloading curves in a material model, at a price of negligible loss of precision.

Open Access: Yes

DOI: 10.1515/mt-2022-0382

SISTER CITY NETWORK’S DEVELOPMENT IN CENTRAL-EASTERN EUROPEAN REGIONAL CENTRES

Ádám Páthy Petra Kinga Kézai

Publication Name: Theoretical and Empirical Researches in Urban Management

Publication Date: 2023-08-01

Volume: 18

Issue: 3

Page Range: 5-26

Description:

In recent years, the analysis of contact networks has become increasingly popular in academia. Originally built on cultural understanding and peace through civil diplomacy, twinning, however, is in a state of flux in today's society. This study aims to analyse the network of sister cities in the Central and Eastern European region. This co-operation emerged in Europe in the early 1900s and spread worldwide after the Second World War. The research seeks to answer the question: what kind of sister city networks have developed between Central and Eastern European cities in contemporary times? The analysis focuses on regional centres with spatial functions at NUTS2 level in ten regional countries, with a total of 95 cities with a population of between 100,000 and 1 million inhabitants. The research is based on the Eurostat Urban Audit and the database on twinning and partnership published on the official websites of the cities. The data were analysed using IBM SPSS Statistics 21 software and the network relationships were examined using the network graphing software Gephi 0.9.5. The research results revealed that twinning partnerships are concentrated mainly in small towns in the Central European geographical region of the continent, and within this region between Hungarian, Polish and Romanian cities. The development of twinning relations is seen as a major opportunity for cities of international importance and macro-regional centres to maintain their competitiveness.

Open Access: Yes

DOI: DOI not available

SELECTION OF AGRICULTURAL PRODUCT SALES CHANNELS USING FUZZY DOUBLE MEREC AND FUZZY RAWEC METHOD

Dragan Marinković Dragan Pamucar Adis Puška Miroslav Nedeljković

Publication Name: Agriculture and Forestry

Publication Date: 2024-09-30

Volume: 70

Issue: 3

Page Range: 45-58

Description:

When selling food products, it's important to choose the appropriate sales channel. These channels connect producers with consumers. The aim of this study was to select a channel for the sale of cabbage to end customers. In this paper, six different sales channels that are used in the Semberija region for the sale of cabbage were observed. These sales channels were evaluated using 11 different criteria. In order to choose the sales channel that best meets the set objectives, a fuzzy set approach was used. This approach was chosen because qualitative criteria were used and expert ratings were in the form of linguistic values. Based on the input of seven experts who are professors at agricultural faculties in Bijeljina, it was found that consumer habits were the most important criterion, followed by the criterion compliance with environmental standards, while the smallest weight value was given to the criterion delivery method. Using the RAWEC (Ranking of Alternatives with Weights of Criterion) method, it was shown that online sales yield the best results, after that follows Producer-sales agent-consumer, while according to experts, the sales channel is the best rated Producer-wholesaler-retailer-consumer. This is because various tools can be utilized on the Internet for selling agricultural products. Based on the conducted research, the contribution of this study lies in the selection of sales channels using the integration of the MEREC and RAWEC methods.

Open Access: Yes

DOI: 10.17707/AgricultForest.70.3.03