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  • 1
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    Noise Reduction Evaluation of Multi-Layered Viscoelastic Infinite Cylinder under Acoustical Wave Excitation (2008)
    Hindawi
    Details
    Publication Date: 2008-01-01
    Description: In this paper sound transmission through the multilayered viscoelastic air filled cylinders subjected to the incident acoustic wave is studied using the technique of separation of variables on the basis of linear three dimensional theory of elasticity. The effect of interior acoustic medium on the mode maps (frequency vs geometry) and noise reduction is investigated. The effects of internal absorption and external moving medium on noise reduction are also evaluated. The dynamic viscoelastic properties of the structure are rigorously taken into account with a power law technique that models the viscoelastic damping of the cylinder. A parametric study is also performed for the two layered infinite cylinders to obtain the effect of viscoelastic layer characteristics such as thickness, material type and frequency dependency of viscoelastic properties on the noise reduction. It is shown that using constant and frequency dependent viscoelastic material with high loss factor leads to the uniform noise reduction in the frequency domain. It is also shown that the noise reduction obtained for constant viscoelastic material property is subjected to some errors in the low frequency range with respect to those obtained for the frequency dependent viscoelastic material.Noise reduction analyses are also performed for the infinite cylinder subjected to the periodic incident wave with uniform and piecewise form.
    Print ISSN: 1070-9622
    Electronic ISSN: 1875-9203
    Topics: Mathematics
    Published by Hindawi
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  • 2
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    Solution of Lane-Emden Type Equations by Combination of the Spectral Method and Adomian Decomposition Method (2015)
    Hindawi
    Details
    Publication Date: 2015-04-29
    Description: The application of a new modified Adomian decomposition method for obtaining the analytic solution of Lane-Emden type equations is investigated. The proposed method, called the spectral Adomian decomposition method, is based on a combination of spectral method and Adomian decomposition method. A comparative study between the proposed method and Adomian decomposition method is presented. The obtained result reveals that method is of higher efficiency, validity, and accuracy.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 3
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    A Circuit-Model-Navigated Design Process and Efficiency Estimation for Short-Circuited Self-Excited EBG Resonator Antenna (2016)
    Hindawi
    Details
    Publication Date: 2016-06-01
    Description: The paper presents a circuit model for the computationally efficient design of a planar Short-Circuited Self-Excited EBG Resonator Antenna (SC SE-EBG-RA). To this purpose, the same circuit model previously presented for the Open-Circuited version of the antenna is modified to be applicable to the SC version. Detailed HFSS modeling and simulation corroborate the accuracy of the model in predicting the antenna resonance. The efficiency of the designed antenna is calculated by a simulated Wheeler Cap Method (WCM) and is compared with the standard efficiency given by the numerical analyzer. The EM modeling is arranged so as to incorporate the effects of the SMA connector, discontinuities, and the WC, emulating a real WC measurement and yielding a high degree of confidence in the results. Overall, a small antenna sized with 93% verified efficiency is achieved, which is also compiled with affordable manufacturing processes.
    Print ISSN: 1687-5869
    Electronic ISSN: 1687-5877
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 4
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    Cooperative Spectrum Sensing for Cognitive Heterogeneous Networking Using Iterative Gauss-Seidel Process (2015)
    Hindawi
    Details
    Publication Date: 2015-12-02
    Description: Heterogeneous networks with dense deployment of small cells can employ cognitive features to efficiently utilize the available spectrum resources. Spectrum sensing is the key enabler for cognitive radio to detect the unoccupied channels for data transmission. In order to deal with shadowing and multipath fading in sensing channels, cooperative spectrum sensing is designed to increase the accuracy of the sensed signal. In this paper, an optimized local decision rule is implemented for the case that the received data from primary users are possibly correlated due to the sensing channel impairments. Since the prior information is unavailable in the real systems, Neyman-Pearson criterion is used as the cost function. Then, a discrete iterative algorithm based on Gauss-Seidel process is applied to optimize the local cognitive user decision rules under a fixed fusion rule. This method with low complexity can minimize the cost using the golden section search method in a finite number of iterations. ROC curves are depicted using the achieved probability of detection and false alarm by numerical examples to illustrate the efficiency of the proposed algorithm. Simulation results also confirm the superiority of the proposed method compared to the conventional topologies and decision rules.
    Print ISSN: 1550-1329
    Electronic ISSN: 1550-1477
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 5
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    Combustion of Biogas Released from Palm Oil Mill Effluent and the Effects of Hydrogen Enrichment on the Characteristics of the Biogas Flame (2015)
    Hindawi
    Details
    Publication Date: 2015-03-24
    Description: Biogas released from palm oil mill effluent (POME) could be a source of air pollution, which has illustrated negative effects on the global warming. To protect the environment from toxic emissions and use the energy of POME biogas, POME is conducted to the closed digestion systems and released biogas is captured. Since POME biogas upgrading is a complicated process, it is not economical and thus new combustion techniques should be examined. In this paper, POME biogas (40% CO2 and 60% CH4) has been utilized as a fuel in a lab-scale furnace. A computational approach by standard k-ε combustion and turbulence model is applied. Hydrogen is added to the biogas components and the impacts of hydrogen enrichment on the temperature distribution, flame stability, and pollutant formation are studied. The results confirm that adding hydrogen to the POME biogas content could improve low calorific value (LCV) of biogas and increases the stability of the POME biogas flame. Indeed, the biogas flame length rises and distribution of the temperature within the chamber is uniform when hydrogen is added to the POME biogas composition. Compared to the pure biogas combustion, thermal NOx formation increases in hydrogen-enriched POME biogas combustion due to the enhancement of the furnace temperature.
    Print ISSN: 2090-1968
    Electronic ISSN: 2090-1976
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Hindawi
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  • 6
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    Exact Optimum Design of Segmented Thermoelectric Generators (2016)
    Hindawi
    Details
    Publication Date: 2016-04-12
    Description: A considerable difference between experimental and theoretical results has been observed in the studies of segmented thermoelectric generators (STEGs). Because of simplicity, the approximate methods are widely used for design and optimization of the STEGs. This study is focused on employment of exact method for design and optimization of STEGs and comparison of exact and approximate results. Thus, using new highly efficient thermoelectric materials, four STEGs are proposed to operate in the temperature range of 300 to 1300 kelvins. The proposed STEGs are optimally designed to achieve maximum efficiency. Design and performance characteristics of the optimized generators including maximum conversion efficiency and length of elements are calculated through both exact and approximate methods. The comparison indicates that the approximate method can cause a difference up to 20% in calculation of some design characteristics despite its appropriate results in efficiency calculation. The results also show that the maximum theoretical efficiency of 23.08% is achievable using the new proposed STEGs. Compatibility factor of the selected materials for the proposed STEGs is also calculated using both exact and approximate methods. The comparison indicates a negligible difference in calculation of compatibility factor, despite the considerable difference in calculation of reduced efficiency (temperature independence efficiency).
    Print ISSN: 1687-806X
    Electronic ISSN: 1687-8078
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Hindawi
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  • 7
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    Mathematical Modelling and Acoustical Analysis of Classical Guitars and Their Soundboards (2018)
    Hindawi
    Details
    Publication Date: 2018-03-05
    Description: Research has shown that the soundboard plays an increasingly important role compared to the sound hole, back plate, and the bridge at high frequencies. The frequency spectrum of investigation can be extended to 5 kHz. Design of bracings and their placements on the soundboard increase its structural stiffness as well as redistributing its deflection to nonbraced regions and affecting its loudness as well as its response at low and high frequencies. This paper attempts to present a review of the current state of the art in guitar research and to propose viable alternatives that will ultimately result in a louder and better sounding instrument. Current research is an attempt to increase the sound level with bracing designs and their placements, control of natural frequencies using scalloped braces, as well as improve the acoustic radiation of this instrument at higher frequencies by deliberately inducing asymmetric modes in the soundboard using the concept of “splitting board.” Various mathematical methods are available for analysing the soundboard based on the theory of thin plates. Discrete models of the instrument up to 4 degrees of freedom are also presented. Results from finite element analysis can be utilized for the evaluation of acoustic radiation.
    Print ISSN: 1687-6261
    Electronic ISSN: 1687-627X
    Topics: Physics
    Published by Hindawi
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  • 8
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    Solution of Lane-Emden Type Equations by Combination of the Spectral Method and Adomian Decomposition Method (2015)
    Hindawi
    Details
    Publication Date: 2015-01-01
    Description: The application of a new modified Adomian decomposition method for obtaining the analytic solution of Lane-Emden type equations is investigated. The proposed method, called the spectral Adomian decomposition method, is based on a combination of spectral method and Adomian decomposition method. A comparative study between the proposed method and Adomian decomposition method is presented. The obtained result reveals that method is of higher efficiency, validity, and accuracy.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 9
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    Solution of Temperature Distribution in a Radiating Fin Using Homotopy Perturbation Method (2009)
    Hindawi
    Details
    Publication Date: 2009-01-01
    Description: Radiating extended surfaces are widely used to enhance heat transfer between primary surface and the environment. The present paper applies the homotopy perturbation to obtain analytic approximation of distribution of temperature in heat fin radiating, which is compared with the results obtained by Adomian decomposition method (ADM). Comparison of the results obtained by the method reveals that homotopy perturbation method (HPM) is more effective and easy to use.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
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  • 10
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    Modeling and Quantification of Resilience in Complex Engineering Systems (2019)
    Hindawi
    Details
    Publication Date: 2019-12-10
    Print ISSN: 1076-2787
    Electronic ISSN: 1099-0526
    Topics: Computer Science , Mathematics
    Published by Hindawi
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