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Found 6289 publications

Integrated experimental design and nonlinear optimization to handle computationally expensive models under resource constraints

János D. Pintér Zoltán Horváth

Publication Name: Journal of Global Optimization

Publication Date: 2013-09-01

Volume: 57

Issue: 1

Page Range: 191-215

Description:

In many real-world applications of optimization, the underlying descriptive system model is defined by computationally expensive functions: simulation modules, numerical models and other "black box" model components are typical examples. In such cases, the model development and optimization team often has to rely on optimization carried out under severe resource constraints. To address this important issue, recently a Regularly Spaced Sampling (RSS) module has been added to the Lipschitz Global Optimizer (LGO) solver suite. RSS generates non-collapsing space filling designs, and produces corresponding solution estimates: this information is passed along to LGO for refinement within the given resource (function evaluation and/or runtime) limitations. Obviously, the quality of the solution obtained will essentially depend both on model instance difficulty and on the admissible computational effort. In spite of this general caveat, our results based on solving a selection of non-trivial global optimization test problems suggest that even a moderate amount of well-placed sampling effort enhanced by limited optimization can lead at least to reasonable or even to high quality results. Our numerical tests also indicate that LGO's overall efficiency is often increased by using RSS as a presolver, both in resource-constrained and in completed LGO runs. © 2012 Springer Science+Business Media, LLC.

Open Access: Yes

DOI: 10.1007/s10898-012-9882-7

Improving system reliability in optical networks by failure localization using evolutionary optimization

Peter Balazs Soproni Krisztián Balázs L. T. Kóczy

Publication Name: Syscon 2013 7th Annual IEEE International Systems Conference Proceedings

Publication Date: 2013-08-30

Volume: Unknown

Issue: Unknown

Page Range: 394-399

Description:

This paper proposes a novel approach for cost-effective link failure localization in optical networks in order to improve the reliability of telecommunication systems. In such failure localization problems the optical network is usually represented by a graph, where the task is to form connected edge sets, so-called monitoring trails (m-trails), in a way that the failure of a link causes the failure of such a combination of m-trails, which unambiguously identifies the failed link. Every m-trail consumes a given amount of resources (like bandwidth, detectors, amplifiers, etc.). Thus, operators of optical network may prefer a set of paths, whose paths can be established in an easy and cost-effective way, while minimizing the interference with the route of the existing demands, i.e. may maximize the revenue. In this paper, unlike most existing techniques dealing with failure localization in this context, the presently proposed method considers a predefined set of paths in the graph as m-trails. This way the task can also be formulated as a special Set Covering Problem (SCP), whose general form is a frequently used formulation in a certain type of operations research problems (e.g. resource assignment). Since for the SCP task evolutionary algorithms, like Ant Colony Optimization (ACO), has been successfully applied in the operations research field, in this work the failure localization task is solved by using ACO on the SCP formulation of the described covering problem, which is a rather unique combination of approaches of different fields (telecommunication, operations research and evolutionary computation) placing our investigation in the multi-field scope of complex systems. © 2013 IEEE.

Open Access: Yes

DOI: 10.1109/SysCon.2013.6549912

Occurrence and distribution of polycyclic aromatic hydrocarbons in surface water of the Raba River, Hungary

István Vass Andrea Szabó Nagy János Szabó

Publication Name: Journal of Environmental Science and Health Part A Toxic Hazardous Substances and Environmental Engineering

Publication Date: 2013-08-24

Volume: 48

Issue: 10

Page Range: 1190-1200

Description:

The objective of this study was to investigate the concentration level and distribution of polycyclic aromatic hydrocarbons (PAHs) in surface water of the Raba River; the largest Danube tributary in Hungary. A total of 54 water samples were collected in the period of 2008-2011 and analysed for PAHs by gas chromatography-mass spectrometry (GC/MS) method. The total PAH concentrations (sum of the concentrations of 17 individual PAH compounds) ranged from 41 to 437 ng/L with the mean value of 111 ± 69.4 ng/L. Phenanthrene and naphthalene were the dominant species in the surface water. Using TEF approaches on the mean concentration PAH data, benzo[a]pyrene and dibenz[ah]anthracene contributed the highest carcinogenic exposure equivalent. A selected number of concentration ratios of specific PAH compounds were calculated to evaluate the possible sources of PAH contamination. The ratios reflected a pattern of pyrogenic input as a major source of PAHs. The comparison of the total PAH concentrations observed for Raba River with other surface waters of the world confirmed that the Raba River could not be regarded as a contaminated river according to the levels of PAHs. © 2013 Taylor & Francis Group, LLC.

Open Access: Yes

DOI: 10.1080/10934529.2013.776455

Performance analysis and comparison of different DNS64 implementations for Linux, OpenBSD and FreeBSD

Sándor Répás Gábor Lencse

Publication Name: Proceedings International Conference on Advanced Information Networking and Applications AINA

Publication Date: 2013-08-08

Volume: Unknown

Issue: Unknown

Page Range: 877-884

Description:

The transition mechanisms for the first phase of IPv6 deployment are surveyed and the most important DNS64 solutions are selected. The test environment and the testing method are described. As for the selected DNS64 implementations, the performance of both BIND9 and TOTD running under Linux, OpenBSD and FreeBSD are measured and compared. The stability of all the tested DNS64 solutions was analyzed under serious overload conditions to test if they may be used in production environments with strong response time requirements. © 2013 IEEE.

Open Access: Yes

DOI: 10.1109/AINA.2013.80

Application of PETSC and other useful packages in finite element simulation

Miklós Kuczmann Daniel Marcsa Gergely Kovács György Tomozi Péter Prukner Gergely Friedl Tamás Budai Tamás Unger

Publication Name: Pollack Periodica

Publication Date: 2013-08-01

Volume: 8

Issue: 2

Page Range: 141-148

Description:

In the frame of the project TÁMOP 4.2.2.A, at the Széchenyi István University, the goal is to work out a new finite element package for the simulation and optimization of permanent magnet synchronous motors. These motors are then used to drive new electric cars. The aim of the two dimensional package is the fast numerical modeling of these electric devices by the use of free tools presented in the paper. Of course, the software is aimed to use it in the simulation of other devices, and three dimensional problems, as well.

Open Access: Yes

DOI: 10.1556/Pollack.8.2013.2.15

The Interpretive Practice of the Hungarian Constitutional Court: A Critical View

Zoltán Szente

Publication Name: German Law Journal

Publication Date: 2013-08-01

Volume: 14

Issue: 8

Page Range: 1591-1614

Description:

No description provided

Open Access: Yes

DOI: 10.1017/S2071832200002418

Assessing uncertainty of driver's distinguishing between built-up and nonbuilt up areas

Gabriella Kosztolanyi-Ivan

Publication Name: Pollack Periodica

Publication Date: 2013-08-01

Volume: 8

Issue: 2

Page Range: 87-96

Description:

The safe speeds and also the general speed limits are quite different outside and within built-up areas. If it does not follow from the road design, whether the given scene is within or outside built-up area, drivers are uncertain about their appropriate speed.This paper shows two approaches to assess the degree of uncertainty of the drivers. The first was a questionnaire survey of requested speeds at various road scenes. In the second method, the recognition process of drivers was simulated by image classification software.Output indicators of these methods (standard deviation of speeds and certainty score) can serve as tools to identify road scenes and road elements leading to uncertain and therefore risky situations.

Open Access: Yes

DOI: 10.1556/Pollack.8.2013.2.10

Magnet losses of fractional number slots per pole PMSM in flux weakening operation

I. Szenasy

Publication Name: Proceedings of the International Conference on Power Electronics and Drive Systems

Publication Date: 2013-08-01

Volume: Unknown

Issue: Unknown

Page Range: 761-766

Description:

An applied control the PMSM is the flux weakening operation for extending the region over nominal speed but on nominal voltage. This paper deals with these questions and its impacts. The proved method is increasing the torque angle and with this the d axis directed component of the stator current vector for reduce the main flux, but the loss developing in magnets became significant. These impacts and its reduction need several investigations. Our work indicates the possibilities and limits of flux-weakening for a given PMSM, and a usable control strategy. © 2013 IEEE.

Open Access: Yes

DOI: 10.1109/PEDS.2013.6527119

Modeling laterally loaded piles

János Szép

Publication Name: Pollack Periodica

Publication Date: 2013-08-01

Volume: 8

Issue: 2

Page Range: 117-129

Description:

Single row pile groups are gaining popularity as foundation system for both buildings and bridges. They are a reasonable and economical solutions for structures with low vertical loads e.g. bridge abutments. The lateral resistance of a pile group is the result of contact pressure between the individual pile shafts and the soil. When designing this kind of structure, the estimation of displacements and bending moments is the main focus of the calculation. In most cases single piles are modeled by assuming a Winkler material. For their calculations, designers typically employ one of the commonly-used structural FEM codes (e.g. AxisVM, Fem-Design). On the other hand, advanced, truly 3D FEM packages (like MIDAS GTS, Plaxis 3D) are available, allowing for realistic modeling of the soil environment and soil-structure interaction. As an intermediate solution, packages based on traditional approaches are also available (GEO5, CGU). In this paper, results obtained using three different calculation methods and packages are compared.

Open Access: Yes

DOI: 10.1556/Pollack.8.2013.2.13