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Found 6289 publications

Optimal design of extrusion dies in metal forming using the finite element method

Lotfi Abdelhakim

Publication Name: Proceedings of the 13th International Conference on Civil Structural and Environmental Engineering Computing

Publication Date: 2011-12-01

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

In this paper, a method for calculation of the optimal shapes of axisymmetrical converging dies using the finite element method is presented. The shape optimization problem considered in this paper is to find the best shape of the die such that the flow rate will be uniform at the die exit. The optimization problem is to minimize an objective function by varying a part of boundary (ie: the shape of die) subject to constraints imposed by the metal forming problem. In this method, B-spline functions allow us to determine the shape of the die, using its control points as design variables. © Civil-Comp Press, 2011.

Open Access: Yes

DOI: DOI not available

Spectral properties of fullerene graphs

Tomislav Došlić Tamás Réti

Publication Name: Match

Publication Date: 2011-12-01

Volume: 66

Issue: 3

Page Range: 733-742

Description:

We use a result from the theory of geometric representation of graphs to show that the separator of a fullerene graph on n vertices cannot exceed 24/n, thus improving the best currently known upper bound of 1-3/n. The result is then combined with a recently established upper bound on the smallest eigenvalue of fullerene graphs to show that there are only finitely many Ramanujan fullerenes. That settles down a conjecture on fullerenes made by the Graffiti software.

Open Access: Yes

DOI: DOI not available

Case study of unscented state estimation for batch distillation processes

András Edelmayer Adriana Encinoza Moira Miranda

Publication Name: IEEE International Conference on Control and Automation Icca

Publication Date: 2011-12-01

Volume: Unknown

Issue: Unknown

Page Range: 919-924

Description:

In this paper a comparative study on the use of extended and unscented Kalman filters for state estimation in nonlinear systems is presented. This is done to reveal the differences, and congruencies, in filters' synthesis in view of real plant implementation on embedded platforms. One of the objectives is to validate the usual performance measures of the filters, meant by state estimation, experimentally. Design features, such as the complexity of implementation and the sensitivity of the state initialization process on uncertain covariance information at regular filters startup are evaluated in a variety of real plant scenarios. A pilot plant of batch distillation process has been used for experimentation. © 2011 IEEE.

Open Access: Yes

DOI: 10.1109/ICCA.2011.6137937

Efficient numerical models for electro-mechanical analysis

Lotfi Abdelhakim

Publication Name: Aip Conference Proceedings

Publication Date: 2011-11-28

Volume: 1389

Issue: Unknown

Page Range: 1996-1999

Description:

In this paper, we present a numerical procedure that can be used to model the electro-mechanical coupled behavior of the dielectric actuator domain. The equation describing the electrostatical part is given by the reduced form of the Maxwell equation and the electrostatic potential [1]. The mechanical problem is described by the constitutive equations and equilibrium equations. Using the finite element method, this technique is to divide a whole problem into sub-problems. The complexity of the original problem is therefore reduced by focusing only on areas most relevant. A finite element analysis is then performed by applying the electrostatic Maxwell pressure as Neumann boundary conditions to compute the displacements. Once the displacement is computed, the electrostatic domain or the conductor is updated. Electrostatic analysis is performed on the updated geometry and the finite element method is then used to determine the change in potential due to geometric perturbations. Once the surface charge densities are known, the new electrostatic Maxwell pressure is computed. The mechanical and electrostatic analysis is repeated until an equilibrium state is computed. The procedure is demonstrated in the paper by the solution of some two-dimensional and three-dimensional problems. © 2011 American Institute of Physics.

Open Access: Yes

DOI: 10.1063/1.3637006

Topology analysis of scanning microscope images with structural entropy and discrete wavelet transform

András Fehér Szilvia Nagy

Publication Name: International Conference on Systems Signals and Image Processing

Publication Date: 2011-11-02

Volume: Unknown

Issue: Unknown

Page Range: 101-104

Description:

Topology free structure of scanning electron microscopy images of heat treated, metallized compound semiconductor surfaces are studied using structural entropy based analysis. The scale dependence and the possible superstructures are determined by wavelet transforming the images before the localization type detection. The studied images are taken in-situ during a thermalization experiment, using GaAs as a substrate and gold, zinc and SiO2 layers of 60 to 100 nm thickness. © 2011 Univ of Sarajevo.

Open Access: Yes

DOI: DOI not available

Topology analysis of scanning microscope images with structural entropy and discrete wavelet transform

No authors available

Publication Name: International Conference on Systems, Signals, and Image Processing

Publication Date: 2011-11-02

Volume:

Issue:

Page Range: 101-104

Description:

Topology free structure of scanning electron microscopy images of heat treated, metallized compound semiconductor surfaces are studied using structural entropy based analysis. The scale dependence and the possible superstructures are determined by wavelet transforming the images before the localization type detection. The studied images are taken in-situ during a thermalization experiment, using GaAs as a substrate and gold, zinc and SiO2 layers of 60 to 100 nm thickness. © 2011 Univ of Sarajevo.

Open Access: No

DOI: DOI not available

Thermoplastic starch composites reinforced by agricultural by-products: Properties, biodegradability, and application

T. Czigany Gabor Dogossy

Publication Name: Journal of Reinforced Plastics and Composites

Publication Date: 2011-11-01

Volume: 30

Issue: 21

Page Range: 1819-1825

Description:

This article focuses on the development of starch-based biodegradable polymer composites reinforced by agricultural byproducts. Maize hull and sugarcane bagasse were used as reinforcements in maize starch, which was plasticized by glycerol and maltitol. Compounds with different compositions were produced by compounding in a twin screw extruder. The mechanical (tensile-, three point bending-, and Charpy-impact) properties and shrinkage were determined on injection-molded specimens and compared with those of commercial HDPE. The mechanical properties of thermoplastic starch increased with the addition of both maze hull and sugarcane bagasse, but only the latter ensured comparable results with reference HDPE. This was traced to differences in the interfacial adhesion between filler and matrix as observed by scanning electron microscopy. Distance spacers for pizza boxes, usually made from HDPE, were injection molded from these biodegradable composites and subjected biodegradation in soil. The related results indicated that this biodegradable spacer is a good and environmentally benign alternative for the HDPE counterpart.

Open Access: Yes

DOI: 10.1177/0731684411429728

Cooperation in multiagent systems

Claudiu Radu Pozna Peter Foldesi Radu Emil Precup Janos Kovacs

Publication Name: Sisy 2011 9th International Symposium on Intelligent Systems and Informatics Proceedings

Publication Date: 2011-10-26

Volume: Unknown

Issue: Unknown

Page Range: 195-200

Description:

This paper gives aspects related to a cooperation scenario in the framework of multiagent systems. The presentation is focused on a multiagent system that consists of two agents, the Master and the Apprentice. The theoretical basis of the cooperation scenario is the definition of the most probable process, and two algorithms are used with this regard. The formulation of the cooperation scenario is exemplified for a case study that builds an architecture of successively placed bricks in the workspace. © 2011 IEEE.

Open Access: Yes

DOI: 10.1109/SISY.2011.6034321

Enhanced slip control performance using nonlinear passive suspension system

J. O. Pedro Claudiu Radu Pozna S. John

Publication Name: IEEE ASME International Conference on Advanced Intelligent Mechatronics AIM

Publication Date: 2011-10-17

Volume: Unknown

Issue: Unknown

Page Range: 277-282

Description:

Antilock Brake System (ABS) controller maintains or controls the slip between tyre and road to maximize the braking torque to achieve a shorter braking distance and control of the steering wheel. This paper presents a PID slip controller performance that incorporates nonlinear passive suspension dynamics. Three scenarios were compared The first scenario is the performance of the controller in a vehicle model without any suspension dynamics, the second scenario incorporates linear passive vehicle suspension system (LPVSS) and the third scenario incorporates nonlinear passive vehicle suspension system (NLPVSS). The incorporation of the passive suspension dynamics enhanced the ABS performance. © 2011 IEEE.

Open Access: Yes

DOI: 10.1109/AIM.2011.6027054