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Found 6289 publications

Overall imperfection method for flexure and compression steel beam-columns

Achim Rubert G. Hajdú Ferenc Papp

Publication Name: Stahlbau

Publication Date: 2017-06-01

Volume: 86

Issue: 6

Page Range: 483-496

Description:

Overall imperfection method for flexure and compression steel beam-columns. The principles and applications of the overall (global) imperfection method (OIM) for beam-columns are presented in this paper. The buckling resistance of a beam-column member is determined by the resistance of its critical cross-section taking into account second-order effect of the eigenform equivalent initial imperfection. The maximum amplitude of this initial imperfection, in the shape of elastic buckling mode, is determined from fundamental cases, which are simply fork supported members with uniform cross-section under uniformly distributed normal force or bending moment. The standardized buckling resistance of the fundamental cases is based on theoretical and empirical background. The proposed global imperfection method is adequate for computer-aided design method using advanced elastic beam-column finite element method including the warping behavior of the cross section. The accuracy of the presented method is illustrated step-by-step with numerical examples.

Open Access: Yes

DOI: 10.1002/stab.201710471

The effect of mold temperature on chemical foaming of injection molded recycled polyethylene-terephthalate

Ferenc Ronkay Bela Molnar Gabor Dogossy

Publication Name: Thermochimica Acta

Publication Date: 2017-05-10

Volume: 651

Issue: Unknown

Page Range: 65-72

Description:

Foam injection molded samples were produced from recycled polyethylene-terephthalate using endothermic and exothermic foaming agents at different mold temperatures. The foam structure was analyzed by computer tomography and optical microscopy. The morphological properties of samples were analyzed by differential scanning calorimetry, using the three-phase model. Viscosities of the melts were changed during processing by endothermic and exothermic foaming agents, and as a result different foam structures were formed. Relationships between mold temperature and porosity were found. Morphologies of the samples made with different foaming agents were different, also due to the different cooling rates caused by the endothermic and exothermic foaming reactions.

Open Access: Yes

DOI: 10.1016/j.tca.2017.02.013

On a translated frame-based approach to geometric modeling of robots

Claudiu Radu Pozna Radu Emil Precup

Publication Name: Robotics and Autonomous Systems

Publication Date: 2017-05-01

Volume: 91

Issue: Unknown

Page Range: 49-58

Description:

The geometric modeling gives the structure configuration and enables the derivation of the kinematic or dynamic models of robots, it involves a procedure for reference frames definition and a specific formalism that allows the poses transformations from a reference frame to another one. This paper proposes a new geometrical modeling approach, referred to as the translated frame-based approach, which has two main advantages over the state-of-the art, namely the reference frames definition is intuitive and it eliminates the computation of the transformation operators. The frames definitions are reduced to apparent translations of the base frame and the computation is replaced with choosing an operator from a collection of six operators that cover all transformation possibilities. The suggested approach is validated by the computation of the geometric models of a PUMA robot and a redundant robot.

Open Access: Yes

DOI: 10.1016/j.robot.2017.01.004

The probability of obstructive sleep apnea disorders emergence by odds ratio of main risk factors

Ferenc Ihász Krisztina Szabó

Publication Name: Orvosi Hetilap

Publication Date: 2017-05-01

Volume: 158

Issue: 21

Page Range: 823-828

Description:

Introduction: The quality of sleep plays a serious role in the individual's daytime performace and state of health, there by it has a strong influence on the society. Aim: The present study measures the probability developing and severity of obstructive sleep apnea syndrome, - which belongs to group of disorders of the respiratory - through odds ratio of leading risk factors. Method: 127 persons were examined in the test. The sleep structure test data were processed by polysomnographic screening device. Results: The nutritional level of body in mass index (BMI), and the neck circumferences data were recorded in cm. On the basis of the examination the gender as a risk factor it can be said that the odds ratio for men compared to women, more than three times higher of emergence of disease. Conclusions: Men's chance of the emergence of serious disease is more than four times higher than women's chance. In the men's test group the most significant predictor of obstructive sleep apnea amongst the risk factors is the circumference according to odds ratio. In women's group the leader odds ratio is BMI. More than 50% of test goup don't report about daytime sleepiness, and this fact draws our attention to the role of risk factors' odds ratio in selection.

Open Access: Yes

DOI: 10.1556/650.2017.30742

Phase-field modeling of eutectic structures on the nanoscale: the effect of anisotropy

László Környei László Rátkai Tamás Pusztai László Gránásy Gyula I. Tóth

Publication Name: Journal of Materials Science

Publication Date: 2017-05-01

Volume: 52

Issue: 10

Page Range: 5544-5558

Description:

A simple phase-field model is used to address anisotropic eutectic freezing on the nanoscale in two (2D) and three dimensions (3D). Comparing parameter-free simulations with experiments, it is demonstrated that the employed model can be made quantitative for Ag–Cu. Next, we explore the effect of material properties and the conditions of freezing on the eutectic pattern. We find that the anisotropies of kinetic coefficient and the interfacial free energies (solid–liquid and solid–solid), the crystal misorientation relative to pulling, the lateral temperature gradient play essential roles in determining the eutectic pattern. Finally, we explore eutectic morphologies, which form when one of the solid phases are faceted, and investigate cases, in which the kinetic anisotropy for the two solid phases is drastically different.

Open Access: Yes

DOI: 10.1007/s10853-017-0853-8

Contribution to the multi-machine pedestal scaling from the COMPASS tokamak

M. Berta M. Aftanas J. Varju M. Komm J. Havlicek D. Naydenkova M. Peterka P. Hacek O. Grover M. Imrišek J. Urban P. Vondráček E. Stefanikova O. Bogár J. Krbec K. Mitošinková M. Sos P. B. Snyder P. Bilková M. Hron P. Böhm R. Pánek V. Weinzettl J. Stöckel L. Frassinetti

Publication Name: Nuclear Fusion

Publication Date: 2017-04-06

Volume: 57

Issue: 5

Page Range: Unknown

Description:

First systematic measurements of pedestal structure during Ohmic and NBI-assisted Type I ELMy H-modes were performed on the COMPASS tokamak in two dedicated experimental campaigns during 2015 and 2016. By adjusting the NBI heating and a toroidal magnetic field, the electron pedestal temperature was increased from 200 eV up to 300 eV, which allowed reaching pedestal collisionality v∗ ped < 1 at q95 ∼3. COMPASS has approached conditions for the Identity experiment done at JET and DIII-D, complementing the range of scanned p∗ ped. The pedestal pressure was successfully reproduced by the EPED model. The dependence of pedestal pressure width on v∗ ped and βpol ped is discussed.

Open Access: Yes

DOI: 10.1088/1741-4326/aa6659

A concept reduction approach for fuzzy cognitive map models in decision making and management

Miklós F. Hatwágner Adrienn Buruzs Elpiniki I. Papageorgiou L. T. Kóczy

Publication Name: Neurocomputing

Publication Date: 2017-04-05

Volume: 232

Issue: Unknown

Page Range: 16-33

Description:

Policy making, strategic planning and management in general are complex decision making tasks, where the formulation of a quantitative mathematical model may be difficult or impossible due to lack of numerical data and dependence on imprecise verbal expressions. For such systems, knowledge representation graphs and cognitive maps are most familiar and often used for modelling complexity and aiding decision making. Fuzzy Cognitive Maps (FCM), as graph-based cognitive models, have been successfully used for knowledge representation and reasoning. In modelling complex systems usually a large number of concepts need to be considered. However, it is often difficult in real applications to find the appropriate number of concepts. Using only a few concepts is not enough to represent the modelled system with the required precision, and increasing the number of concepts increases the complexity of the model quadratically; it is burdensome to work with for the experts. The contribution of this paper is two-fold: (i) to propose a new concept reduction approach for FCM and (ii) to apply it on developing less complex FCM for management and decision making. The behaviour of reduced models is analysed through a number of scenarios with respect to the original complex system. The main idea of the reduction is a clustering based on fuzzy tolerance relations. The new approach is focused on reducing complexity in the modelling process, which provides a more transparent and easy to use model for policy makers. The applicability of the proposed method is demonstrated via literature examples and a solid waste management case study that initiated this research. The results clearly show the advantageous characteristics of the proposed concept reduction method for FCM and its aid in policy making.

Open Access: Yes

DOI: 10.1016/j.neucom.2016.11.060

Methodology development on aquatic environmental assessment

László Dióssy József Németh Viktor Sebestyén Péter Huszka Tatjana Juzsakova Cuong Le Phuoc Ákos Rédey Endre Domokos

Publication Name: Environmental Science and Pollution Research

Publication Date: 2017-04-01

Volume: 24

Issue: 12

Page Range: 11126-11140

Description:

The Water Framework Directive aims at reaching the good ecological status of the surface and ground water bodies (László et al. Microchem J 85(1):65–71, 2007). The paper deals with quality evaluation of waters with special focus on the water chemistry parameters as defined in the Water Framework Directive and pertaining legal regulations. The purpose of this paper is to devise a quantitative type of water quality assessment method which could provide rapid, accurate, and reliable information on the quality of the surface waters by using water chemistry parameters. Quality classes have been defined for every water chemistry parameter in light of the legal limit values of the water parameters. In addition to this, weight indices were calculated on the basis of the outcome of the paired comparison of water chemistry parameters and normalized matrix. This was followed by the parametric level analysis of the water chemistry parameters, and finally, the aquatic environment index (AEI) was calculated, which provided general information on the quality of water regarding the water chemistry parameters. The method was illustrated on Lake Balaton, Hungary in which case water samples taken from Balatonfüred City lake area were analyzed and evaluated with the method devised.

Open Access: Yes

DOI: 10.1007/s11356-016-7941-1

A novel unified approach to invariance conditions for a linear dynamical system

Yunfei Song Tamás Terlaky Zoltán Horváth

Publication Name: Applied Mathematics and Computation

Publication Date: 2017-04-01

Volume: 298

Issue: Unknown

Page Range: 351-367

Description:

In this paper, we propose a novel, simple, and unified approach to explore sufficient and necessary conditions, i.e., invariance conditions, under which four classic families of convex sets, namely, polyhedra, polyhedral cones, ellipsoids, and Lorenz cones, are invariant sets for a linear discrete or continuous dynamical system. For discrete dynamical systems, we use the Theorems of Alternatives, i.e., Farkas lemma and S-lemma, to obtain simple and general proofs to derive invariance conditions. This novel method establishes a solid connection between optimization theory and dynamical system. Also, using the S-lemma allows us to extend invariance conditions to any set represented by a quadratic inequality. Such sets include nonconvex and unbounded sets. For continuous dynamical systems, we use the forward or backward Euler method to obtain the corresponding discrete dynamical systems while preserves invariance. This enables us to develop a novel and elementary method to derive invariance conditions for continuous dynamical systems by using the ones for the corresponding discrete systems. Finally, some numerical examples are presented to illustrate these invariance conditions.

Open Access: Yes

DOI: 10.1016/j.amc.2016.10.007