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Found 6289 publications

A bullwhip type of instability induced by time varying target inventory in production chains

Peter Foldesi Árpád Csík

Publication Name: International Journal of Innovative Computing Information and Control

Publication Date: 2012-08-01

Volume: 8

Issue: 8

Page Range: 5885-5897

Description:

We present an analytic investigation of the bullwhip effect developing in production-distribution chains. All common considered causes of the effect are excluded and the only mean to induce a bullwhip type of instability is the adoption of an inventory replenishment policy involving a variable target level. The policy is designed to maintain a safety stock that is proportional to the actual demand. In order to achieve our goals we develop a particular discrete model of supply chains by introducing some fresh concepts into the field of supply chain stability. The basic idea is to derive an update scheme describing the status of the whole chain over the entire time-space (period-stage) domain of interest. We prove that the strategy of demand driven target inventory inherently leads to an instability developing in the chain, which is precisely a manifestation of the bullwhip effect. Following the identification of the source and the nature of the instability, we propose a new production plan, which is stable and does not exhibit the bullwhip effect at all. Thus, the amplitude of the variation of the production rate never exceeds the amplitude of the oscillation of the market demand within the entire supply chain. © 2012 ICIC International.

Open Access: Yes

DOI: DOI not available

Parametric approximation of fuzzy exponent for computationally intensive problems

No authors available

Publication Name: International Journal of Innovative Computing, Information and Control

Publication Date: 2012-08-01

Volume: 8

Issue: 8

Page Range: 5725-5744

Description:

The paper deals with the investigation of the critical non-linear factors and NP-hard problems of real-life decision-making processes. When using non-linear utility/objective functions to represent the value of various options in the search space or when NP-hard problems arise, often soft computing techniques must be applied for optimization. Many times significant uncertainty must be handled as well, so the use of fuzzy numbers can be an efficient method to cope with ambiguity and lack of information. The fuzzy extensions for heuristic based optimizing algorithms often face the problem of an increased number of calculations required to find the solutions. Appropriate representation of the fuzzy power function for non-linear cases is to be used so that it can keep the required computation time and resources at a reasonable level. © 2012 ICIC International.

Open Access: No

DOI: DOI not available

A bullwhip type of instability induced by time varying target inventory in production chains

No authors available

Publication Name: International Journal of Innovative Computing, Information and Control

Publication Date: 2012-08-01

Volume: 8

Issue: 8

Page Range: 5885-5897

Description:

We present an analytic investigation of the bullwhip effect developing in production-distribution chains. All common considered causes of the effect are excluded and the only mean to induce a bullwhip type of instability is the adoption of an inventory replenishment policy involving a variable target level. The policy is designed to maintain a safety stock that is proportional to the actual demand. In order to achieve our goals we develop a particular discrete model of supply chains by introducing some fresh concepts into the field of supply chain stability. The basic idea is to derive an update scheme describing the status of the whole chain over the entire time-space (period-stage) domain of interest. We prove that the strategy of demand driven target inventory inherently leads to an instability developing in the chain, which is precisely a manifestation of the bullwhip effect. Following the identification of the source and the nature of the instability, we propose a new production plan, which is stable and does not exhibit the bullwhip effect at all. Thus, the amplitude of the variation of the production rate never exceeds the amplitude of the oscillation of the market demand within the entire supply chain. © 2012 ICIC International.

Open Access: No

DOI: DOI not available

Parametric approximation of fuzzy exponent for computationally intensive problems

János Botzheim Peter Foldesi

Publication Name: International Journal of Innovative Computing Information and Control

Publication Date: 2012-08-01

Volume: 8

Issue: 8

Page Range: 5725-5744

Description:

The paper deals with the investigation of the critical non-linear factors and NP-hard problems of real-life decision-making processes. When using non-linear utility/objective functions to represent the value of various options in the search space or when NP-hard problems arise, often soft computing techniques must be applied for optimization. Many times significant uncertainty must be handled as well, so the use of fuzzy numbers can be an efficient method to cope with ambiguity and lack of information. The fuzzy extensions for heuristic based optimizing algorithms often face the problem of an increased number of calculations required to find the solutions. Appropriate representation of the fuzzy power function for non-linear cases is to be used so that it can keep the required computation time and resources at a reasonable level. © 2012 ICIC International.

Open Access: Yes

DOI: DOI not available

Fuzzy Flip-Flop based Neural Networks as a novel implementation possibility of multilayer perceptrons

László Gál Rita Lovassy D. Tóth László T. Kóczy Imre J. Rudas

Publication Name: 2012 IEEE I2mtc International Instrumentation and Measurement Technology Conference Proceedings

Publication Date: 2012-07-30

Volume: Unknown

Issue: Unknown

Page Range: 280-285

Description:

Fuzzy Flip-Flop based Neural Networks (FNN) constructed from fuzzy D flip-flops are studied as a novel technique to implement multilayer perceptrons. The starting point of this approach is the concept of fuzzy flip-flop (F 3), as the extension of the binary counterpart. Fuzzy D flip-flop based neurons are viewed, as sigmoid function generators. Their characteristic equations contain simple fuzzy operations, thus enabling easy implementability. FNNs have an interconnected fuzzy neuron structure composed from a large number of neurons acting in parallel which are capable of learning, and are suitable for function approximation. In this paper we propose the FPGA implementation of ukasiewicz operations, furthermore of fuzzy D flip-flop neurons based on Łukasiewicz norms. © 2012 IEEE.

Open Access: Yes

DOI: 10.1109/I2MTC.2012.6229326

Editorial

Aaron Gazley László Józsa Kim Shyan Fam

Publication Name: International Review of Retail Distribution and Consumer Research

Publication Date: 2012-07-01

Volume: 22

Issue: 3

Page Range: 241-242

Description:

No description provided

Open Access: Yes

DOI: 10.1080/09593969.2012.683326

Parallel solution of an electrostatic field problem-case study

Miklós Kuczmann Daniel Marcsa

Publication Name: Pollack Periodica

Publication Date: 2012-07-01

Volume: 7

Issue: 2

Page Range: 25-34

Description:

The paper presents a parallel approach for the efficient solution of a simple 1D Laplace-Poisson equation problem by parallel finite element method. This problem is a case study. The non-overlapping domain decomposition method has been used to cut the problem into sub-regions or also called sub-domains, and it reduces the large mass matrix into smaller parts. The independent subdomains, and the assembling of these equation systems can be handled by the independent processors of a supercomputer, i.e. in a parallel way. The results of parallel finite element method have been compared to the results of serial finite element method as well as the analytical results.

Open Access: Yes

DOI: 10.1556/Pollack.7.2012.2.2

Performance parameters and stress sensitivity of bitumen at high temperature

Kálmán Adorjányi Peter Fuleki

Publication Name: Pollack Periodica

Publication Date: 2012-07-01

Volume: 7

Issue: 2

Page Range: 109-116

Description:

Permanent deformation in the form of rutting is the most frequently occurring defect of asphalt pavements. This paper gives a short overview of bitumen performance parameters used for characterization of resistance against permanent deformation in the USA and Europe. Investigation of relationships between rheological parameters measured with dynamic shear rheometer using different test modes is presented. The test program consisted of measuring of performance parameters of paving grade, hard, polymer modified and rubber bitumen binders. They were tested in the linear viscoelastic range and beyond. Correlations between complex shear modulus, combined with phase angle, complex viscosity, stress sensitivity, and zero-shear viscosity are given. However, the correspondence of binder parameters with relevant performance parameters of asphalt mixes have to be further investigated.

Open Access: Yes

DOI: 10.1556/Pollack.7.2012.2.10

Fractal based wire antenna impedance simulation by the method of moments

Miklós Kuczmann Zoltán Pólik

Publication Name: Pollack Periodica

Publication Date: 2012-07-01

Volume: 7

Issue: 2

Page Range: 69-81

Description:

Koch curve based dipole antennas have been built up, have been simulated and measured to examine the reachable size reduction.The simulations have been performed by the method of moments (MoM) and the results have been checked by the finite element method (FEM) and by measurements. The Pocklington' integral equation has been implemented in MATLAB environment to simulate the input impedance of dipole antennas. The ATW EFIE method has been implemented and solved by the 4NEC2 software to examine the behavior of arbitrary shaped thin wire antennas. In COMSOL Multiphysics software environment a finite element model has been set up to solve the Helmholtz equation and to simulate the antennas under examination. Koch curve based dipole antennas have been measured in a full anechoic chamber, as well and finally the numerical and the experimental results have been compared.

Open Access: Yes

DOI: 10.1556/Pollack.7.2012.2.6