Mathematical and Computational Applications

4249 KiB

Open AccessArticle

Motor Input Voltage and Rectifier Firing Angle Variation with Load Torque in Constant Current Operated Induction Motors

by Mehmet Akbaba

Math. Comput. Appl. 2009, 14(1), 73-84; https://doi.org/10.3390/mca14010073 - 1 Apr 2009

Cited by 1 | Viewed by 1139

In current source inverter (CSI) fed induction motors (IM) operated under constant current, the input voltage changes within large limits as the load torque changes. In such an operation the motor mostly operates on the saturated portion of its magnetizing characteristic, and non-linear [...] Read more.

In current source inverter (CSI) fed induction motors (IM) operated under constant current, the input voltage changes within large limits as the load torque changes. In such an operation the motor mostly operates on the saturated portion of its magnetizing characteristic, and non-linear relation exists between the input voltage and the load torque. Therefore in this paper a numerical technique is presented for obtaining required input voltage corresponding to a given load torque, which can be used for estimating the firing angle of the input rectifier, which in tum can be used for predicting firing angle in terms of load torque. Proposed technique has been demonstrated with an example. Full article

199 KiB

Open AccessArticle

An Active Queue Management Algorithm for Reducing Packet Loss Rate

by Babek Abbasov and Serdar Korukoğlu

Math. Comput. Appl. 2009, 14(1), 65-72; https://doi.org/10.3390/mca14010065 - 1 Apr 2009

Cited by 8 | Viewed by 1479

Abstract

Among various active queue management schemes (AQM), random early detection (RED) is probably the most extensively studied. Unlike the existing RED enhancement schemes, we use hazard rate estimated packet dropping function in RED. We call this new scheme HERED. The underlying idea is [...] Read more.

Among various active queue management schemes (AQM), random early detection (RED) is probably the most extensively studied. Unlike the existing RED enhancement schemes, we use hazard rate estimated packet dropping function in RED. We call this new scheme HERED. The underlying idea is that, with the proposed packet dropping function, packet dropping becomes gentler than RED at light traffic load but more aggressive at heavy load. Simulations demonstrate that HERED achieves a higher and more stable throughput and performs better than current active queue management algorithms due to the lowest packet drops. Full article

153 KiB

Open AccessArticle

An Approach for Measuring Semantic Relatedness between Words via Related Terms

by Mehmet Ali Salahli

Math. Comput. Appl. 2009, 14(1), 55-63; https://doi.org/10.3390/mca14010055 - 1 Apr 2009

Cited by 18 | Viewed by 1451

Abstract

In this paper we propose a new approach for measuring semantic relatedness between words. The semantic relatedness between words are not measured directly, but are computed via set of words highly related to them, which we call the set of determiner words. Our [...] Read more.

In this paper we propose a new approach for measuring semantic relatedness between words. The semantic relatedness between words are not measured directly, but are computed via set of words highly related to them, which we call the set of determiner words. Our approach for evaluating relatedness belongs to web page counting based measurement methods. We take into account some information, which contains hierarchical and other type of relations between the words. The experimental results demonstrate the effectiveness of proposed method. Full article

216 KiB

Open AccessArticle

Profit Maximization Multi-item Inventory Models Considering Trade Credit and Sales Learning Curve

by Yu-Chung Tsao

Math. Comput. Appl. 2009, 14(1), 45-53; https://doi.org/10.3390/mca14010045 - 1 Apr 2009

Cited by 1 | Viewed by 1107

Abstract

In this paper we consider a multi-item distribution channel subject to supplier’s credit period and retailer’s promotional effort with sales learning curve. We determine the retailer’s promotional effort for each item and the joint replenishment cycle in both decentralized and centralized decision models. [...] Read more.

In this paper we consider a multi-item distribution channel subject to supplier’s credit period and retailer’s promotional effort with sales learning curve. We determine the retailer’s promotional effort for each item and the joint replenishment cycle in both decentralized and centralized decision models. We show that the profits for both parties increase under the centralized decision model when the credit period is kept within an appropriate range. The impacts of credit period and sales learning curve on the behavior of the channel are also discussed. We conclude with computation analyses that lead to a variety of management insights. Full article

231 KiB

Open AccessArticle

A New Perturbation Algorithm With Better Convergence Properties: Multiple Scales Lindstedt Poincare Method

by M. Pakdemirli, M. M. F. Karahan and H. Boyacı

Math. Comput. Appl. 2009, 14(1), 31-44; https://doi.org/10.3390/mca14010031 - 1 Apr 2009

Cited by 41 | Viewed by 1701

Abstract

A new perturbation algorithm combining the Method of Multiple Scales and Lindstedt-Poincare techniques is proposed for the first time. The algorithm combines the advantages of both methods. Convergence to real solutions with large perturbation parameters can be achieved for both constant amplitude and [...] Read more.

A new perturbation algorithm combining the Method of Multiple Scales and Lindstedt-Poincare techniques is proposed for the first time. The algorithm combines the advantages of both methods. Convergence to real solutions with large perturbation parameters can be achieved for both constant amplitude and variable amplitude cases. Three problems are solved: Linear damped vibration equation, classical duffing equation and damped cubic nonlinear equation. Results of Multiple Scales, new method and numerical solutions are contrasted. The proposed new method produces better results for strong nonlinearities. Full article

333 KiB

Open AccessArticle

Verification of a 3-D Numerical Model for Spillway Aerator

by Mualla Ozturk and M. Cihan Aydin

Math. Comput. Appl. 2009, 14(1), 21-30; https://doi.org/10.3390/mca14010021 - 1 Apr 2009

Cited by 9 | Viewed by 1352

Abstract

In this study, the results of CFD obtained by using Fluent with respect to the air entrainment at spillway aerators are compared to the data of the physical model study and the results of some empirical equations presented by other investigators. The air [...] Read more.

In this study, the results of CFD obtained by using Fluent with respect to the air entrainment at spillway aerators are compared to the data of the physical model study and the results of some empirical equations presented by other investigators. The air entrainment rates obtained from the CFD analyses are in reasonable good agreement with the values calculated by the empirical equations. However, the CFD results are better than the physical model data including considerable scale effects. The numerical verification procedure in this study is based on the ASME editorial policy statement, which provides a framework for computational fluid dynamics uncertainty analysis. So, the validation of the CFD model was discussed in this scope. Full article

139 KiB

Open AccessArticle

Figure of Merit of One-dimensional Resonant Transmission Systems in the Quantum Regime

by Mustafa Ali Ali Çipiloğlu and Sadi Turgut

Math. Comput. Appl. 2009, 14(1), 13-19; https://doi.org/10.3390/mca14010013 - 1 Apr 2009

Viewed by 1278

Abstract

The figure of merit, ZT, for a one-dimensional conductor displaying a Lorentzian resonant transmission probability is calculated. The optimum working conditions for largest ZT values are determined. It is found that, the resonance energy has to be adjusted to be several resonance widths [...] Read more.

The figure of merit, ZT, for a one-dimensional conductor displaying a Lorentzian resonant transmission probability is calculated. The optimum working conditions for largest ZT values are determined. It is found that, the resonance energy has to be adjusted to be several resonance widths away from the Fermi level. Similarly it is better for the temperature to be equal to several resonance widths. The approximate relationships, which can be a fairly good guide for designing devices, between different parameters under optimum working conditions are given. Full article

265 KiB

Open AccessArticle

Simple and U-type Assembly Line Balancing by Using an Ant Colony Based Algorithm

by Adil Baykasoğlu and Türkay Dereli

Math. Comput. Appl. 2009, 14(1), 1-12; https://doi.org/10.3390/mca14010001 - 1 Apr 2009

Cited by 16 | Viewed by 1637

Abstract

In this paper, an Ant Colony Optimization (ACO) based heuristic algorithm is proposed for solving simple (straight line) and U-shaped assembly line balancing problems (ALBP). The paper makes one of the first attempts to show how ACO heuristic can be used to solve [...] Read more.

In this paper, an Ant Colony Optimization (ACO) based heuristic algorithm is proposed for solving simple (straight line) and U-shaped assembly line balancing problems (ALBP). The paper makes one of the first attempts to show how ACO heuristic can be used to solve U-shaped ALBP. A new algorithm is proposed in this paper that seamlessly integrates COMSOAL algorithm, Ranked Positional Weight Heuristic (RPWH) and an ACO based heuristic in order to obtain good solutions to simple and U-shaped ALBPs. The result of the computational study has shown that the proposed algorithm is effective in solving simple/U-shaped line balancing problems. Full article

Journal Menu

Journal Browser

Math. Comput. Appl., Volume 14, Issue 1 (April 2009) – 8 articles , Pages 1-84

Further Information

Guidelines

MDPI Initiatives

Follow MDPI