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Found 5164 publications

Nonlinear finite element method in magnetism

Miklós Kuczmann

Publication Name: Pollack Periodica

Publication Date: 2009-08-01

Volume: 4

Issue: 2

Page Range: 13-24

Description:

The paper presents and compares three potential formulations to solve nonlinear static magnetic field problems by applying the fixed-point technique and the Newton-Raphson scheme. Nonlinear characteristics have been handled by the polarization method in the two algorithms. The proposed combination of Newton-Raphson scheme and the polarization formulation result in a very effective nonlinear solver, because only the derivate of the characteristics, i.e. only the permeability or the reluctivity has to be used. That is why, this method can be prosperous to solve nonlinear problems with hysteresis, and it is faster than the classical fixed-point method.

Open Access: Yes

DOI: 10.1556/Pollack.4.2009.2.2

Randomized, double-blind, placebo-controlled, proof-of-concept study of the cortical spreading depression inhibiting agent tonabersat in migraine prophylaxis

M. D. Ferrari P. J. Goadsby J. G. Mills A. Csanyi J. Olesen

Publication Name: Cephalalgia

Publication Date: 2009-07-01

Volume: 29

Issue: 7

Page Range: 742-750

Description:

Tonabersat is a novel putative migraine prophylactic agent with an unique stereospecific binding site in the brain. Tonabersat has been shown, in animal models, to inhibit experimentally induced cortical spreading depression, the likely underlying mechanism for migraine aura, and cerebrovascular responses to trigeminal nerve stimulation. The aim was to study the potential for tonabersat as a migraine preventive. A randomized, double-blind, placebo-controlled, multicentre, parallel group study recruited patients with migraine with and without aura experiencing between two and six migraine attacks per month. After a 1-month baseline they received tonabersat 20 mg daily for 2 weeks and 40 mg daily for a further 10 weeks. The primary end-point was the change in mean number of migraine headache days between the third month and the baseline period in the intention-to-treat population comparing the placebo (n = 65) and tonabersat (n = 58) groups. At the primary end-point there was a 1.0-day (95% confidence interval -0.33, 2.39; P = 0.14) difference in reduction in migraine days between tonabersat and placebo. There were 10 secondary efficacy end-points, of which two were statistically significant. In month 3 of treatment, the responder rate, defined as a 50% reduction in migraine attacks, was 62% for tonabersat and 45% for placebo (P < 0.05), and the rescue medication use was reduced in the tonabersat group compared with placebo by 1.8 days (P = 0.02). Placebo responses were particularly high for all end-points. At least one treatment-emergent adverse event was reported in the tonabersat group in 61% of patients compared with 51% in the placebo group; none was worrisome. Placebo responses were unexpectedly high in this trial, complicating straightforward interpretation of the study results. The good tolerability and promising efficacy results support further exploration of higher doses of tonabersat in larger controlled trials. © Blackwell Publishing Ltd.

Open Access: Yes

DOI: 10.1111/j.1468-2982.2008.01804.x

Universal autonomous robot navigation using quasi optimal path generation

Gábor Pék P. Várlaki Áron Lászka A. R. Várkonyi-Kóczy

Publication Name: Icara 2009 Proceedings of the 4th International Conference on Autonomous Robots and Agents

Publication Date: 2009-06-05

Volume: Unknown

Issue: Unknown

Page Range: 458-463

Description:

Autonomous robot navigation is an important research field because these robots can solve problems where the human presence is impossible, dangerous, expensive, or uncomfortable. In this paper, a new hybrid autonomous navigation method is introduced. The algorithm is composed of visibility graph based global navigation and simple potential field based local navigation parts. It applies a new automated graph generation method which may become necessary if, because of the observed new obstacles, a new path should be generated. The quasi optimal route is found by applying the well known A* algorithm on the graph. The presented technique offers a quasi optimal universal navigation technique which can successfully be used in all, known, unknown, and dynamically changing environments. ©2009 IEEE.

Open Access: Yes

DOI: 10.1109/ICARA.2000.4804008

Health capital in the 'cis-elbanian' vs. 'trans-elbanian' grand regions: Frame disputes about framing ambiguities and misframings

Károly Varga Miklós Losoncz Sára Jeges

Publication Name: European Journal of Mental Health

Publication Date: 2009-06-01

Volume: 4

Issue: 1

Page Range: 3-26

Description:

The present study forms an operational variation of the task undertaken in the outlook paragraph of the authors' earlier article to study with the help of the Sense of Coherence (SOC) as a group property, the health and general well-being of the Hungarian national community (in an international comparison). With Hungary being the only Eastern Central European ('Trans-Elbanian') country joining the EU-project with the title Corporate Culture and Regional Embeddednes (CURE), we Hungarians tried to help achieve this goal by making the following proposal to the researchers of the five Western-European ('Cis-Elbanian') countries partaking in the project: the drastically different Health Capital level of the Grand Regions situated on the two sides of the Elbe-Leitha boundary ('centrum versus semi-periphery') should be inserted as a control variable into the original research model of the project, which has propounded the hypothesis that the interaction between the organisational culture of the corporations operating in the sample region of the individual countries and the national culture of the respective regions has had an impact on the development of the region. We have presumed that this enormous difference between the Health Capital levels can bring to light the true underlying historical-social-economical impact factors which appear to be 'cultural' when approached for the first time. The leadership of the project allowed the Hungarian team to check, beyond the qualitative research design of the project, with the quantitative method of the research, the model variation enriched with a Health Capital variable. The conclusive results thus gained anticipate an affirmation of the results achieved in the original qualitative variation of the project design and may serve as an example for the whole research team to also implement an internationally exact investigation of the effect of the Health Capital as a control variable of the cultural impact in a possible follow up. The present study displays the first, pilot study results of this research undertaking, to be implemented in our country within the frame of the CURE project, and to be transferred into the international comparison if it proves successful. These preliminary results illustrate the interdependency of the cultural dimensions and the Health Capital apprehended in a salutogenic cross section. © 2009 Akadémiai Kiadó, Budapest.

Open Access: Yes

DOI: 10.1556/EJMH.4.2009.1.1

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 P. 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

Multi-level meshless methods based on direct multi-elliptic interpolation

Csaba Gáspár

Publication Name: Journal of Computational and Applied Mathematics

Publication Date: 2009-04-15

Volume: 226

Issue: 2

Page Range: 259-267

Description:

A short overview on the direct multi-elliptic interpolation and the related meshless methods for solving partial differential equations is given. A new technique is proposed which produces a biharmonic interpolation along the boundary and solves the original problem inside the domain. An error estimation is also derived. To implement the method, quadtree-based multi-level methods are used. The approach avoids the use of large, dense and ill-conditioned matrices and significantly reduces the computational cost. © 2008 Elsevier B.V. All rights reserved.

Open Access: Yes

DOI: 10.1016/j.cam.2008.08.005

Simulation of Two-Dimensional supersonic flows on emulated-digital CNN-UM

Sándor Kocsárdi Zoltán Nagy Árpád Csík P. Szolgay

Publication Name: Eurasip Journal on Advances in Signal Processing

Publication Date: 2009-04-09

Volume: 2009

Issue: Unknown

Page Range: Unknown

Description:

Computational fluid dynamics (CFD) is the scientific modeling of the temporal evolution of gas and fluid flows by exploiting the enormous processing power of computer technology. Simulation of fluid flow over complex-shaped objects currently requires several weeks of computing time on high-performance supercomputers. A CNN-UM-based solver of 2D inviscid, adiabatic, and compressible fluids will be presented. The governing partial differential equations (PDEs) are solved by using first- and second-order numerical methods. Unfortunately, the necessity of the coupled multilayered 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.

Open Access: Yes

DOI: 10.1155/2009/923404

Input parameters of transdanubian clay for the hardening soil and soft soil models

Edina Koch

Publication Name: Pollack Periodica

Publication Date: 2009-04-01

Volume: 4

Issue: 1

Page Range: 93-104

Description:

In recent years, finite element modeling has become an important design tool. Advanced programs make it possible to use more complex soil models in addition to standard elasto-plastic models with Mohr-Coulomb failure criteria. These new models can follow nonlinear behavior and complicated loading sequences. The two most promising new models are: the Hardening Soil Model (HS) and the Soft Soil Model (SS). This paper focuses on the behavior of Transdanubian Clay, common in Hungary. Sampling, laboratory testing, and evaluation of data aiming at determining parameters for HS and SS models are described. Results based on oedometer tests using unloading/reloading sequences proved to be adequate for input to these models. © 2009 Akadémiai Kiadó.

Open Access: Yes

DOI: 10.1556/Pollack.4.2009.1.10