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  • Open Access


    Computation of Stiffness and Damping Derivatives of an Ogive in a Limiting Case of Mach Number and Specific Heat Ratio

    Aysha Shabana1,2,*, Asha Crasta1, Sher Afghan Khan3, Abdul Aabid4, Muneer Baig4

    FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.5, pp. 1249-1267, 2023, DOI:10.32604/fdmp.2023.023158

    Abstract This work aims to compute stability derivatives in the Newtonian limit in pitch when the Mach number tends to infinity. In such conditions, these stability derivatives depend on the Ogive’s shape and not the Mach number. Generally, the Mach number independence principle becomes effective from M = 10 and above. The Ogive nose is obtained through a circular arc on the cone surface. Accordingly, the following arc slopes are considered λ = 5, 10, 15, −5, −10, and −15. It is found that the stability derivatives decrease due to the growth in λ from 5 More >

  • Open Access


    Research on VSG Frequency Characteristics and Energy Storage Device Capacity and Charge-Discharge Characteristics Based on Feedforward Branch

    Baoge Zhang1, Shanyan Ping1,*, Haoliang Shi2, Yi Long1, Boxiang Wu1, Yuemin Jiao1

    Energy Engineering, Vol.119, No.6, pp. 2347-2367, 2022, DOI:10.32604/ee.2022.021693

    Abstract Renewable energy is connected to the grid through the inverter, which in turn reduces the inertia and stability of the power grid itself. The traditional grid-connected inverter does not have the function of voltage regulation and frequency regulation and can therefore no longer adapt to the new development. The virtual synchronous generator (VSG) has the function of voltage regulation and frequency regulation, which has more prominent advantages than traditional inverters. Based on the principle of VSG, the relationship between the frequency characteristics and the energy storage capacity of the feedforward branch-based virtual synchronous machine (FVSG) More >

  • Open Access


    On the Dynamics of a Viscoelastic Fluid-Conveying Nanotube

    Ola Adil Ibrahim1, Gunawan Widjaja2, Abdulhussien N. Alattabi3, Krishanveer Singh4, Yasser Fakri Mustafa5, P. A. Krovopuskov6, Mustafa M. Kadhim7,*

    FDMP-Fluid Dynamics & Materials Processing, Vol.18, No.4, pp. 1137-1151, 2022, DOI:10.32604/fdmp.2022.019921

    Abstract The objective of the presented study is to perform a vibration analysis and investigate the stability of a viscoelastic-fluid conveying pipe with an intermediate support. The mathematical model is elaborated in the framework of the Euler-Bernoulli beam theory in combination with the Kelvin-Voight viscoelastic approach. The resulting differential equation of motion and the related boundary conditions and compatibility conditions in the mid-span support are solved analytically using a power series method. The results show that an intermediate support located at ξs = 0.1 and ξs = 0.5 increases the critical velocity up to 35% and 50.15%, More >

  • Open Access


    Corrected Statistical Energy Analysis Model in a Non-Reverberant Acoustic Space

    Al Munawir1, Azma Putra2,*, Iwan Prasetiyo3, Wan Mohd Farid Wan Mohamad2, Safarudin Herawan4

    Sound & Vibration, Vol.55, No.3, pp. 203-219, 2021, DOI:10.32604/sv.2021.015938

    Abstract Statistical Energy Analysis (SEA) is a well-known method to analyze the flow of acoustic and vibration energy in a complex structure. This study investigates the application of the corrected SEA model in a non-reverberant acoustic space where the direct field component from the sound source dominates the total sound field rather than a diffuse field in a reverberant space which the classical SEA model assumption is based on. A corrected SEA model is proposed where the direct field component in the energy is removed and the power injected in the subsystem considers only the remaining More >

  • Open Access


    Experimental Modal Damping Identification of a Mechanical Structure Using Video Magnification Technique

    Jaafar Hallal1,*, Mahmoud Fakih2, Hala Damerji3, Mohammad Hammoud4,5, Mehdi Chouman4,5

    Sound & Vibration, Vol.55, No.2, pp. 131-140, 2021, DOI:10.32604/sv.2021.015293

    Abstract Vibration can be introduced in all mechanical fields in our life. Engineers try to avoid its negative effect leading in some cases to deformation in the machines. Many researches are dedicated to study the identification of damping especially in multi degree of freedom systems with particular attention to the source of energy dissipation. They focus on developing new tools or methods which may be used in real problems to obtain accurate results about the amount (or value) and the location of energy dissipation in the structure. The aim of this paper is to present an… More >

  • Open Access


    Effect of Recycling Cycles on the Mechanical and Damping Properties of Flax Fibre Reinforced Elium Composite: Experimental and Numerical Studies

    Sami Allagui1,2,*, Abderrahim El Mahi1, Jean-Luc Rebiere1, Moez Beyaoui2, Anas Bouguecha2, Mohamed Haddar2

    Journal of Renewable Materials, Vol.9, No.4, pp. 695-721, 2021, DOI:10.32604/jrm.2021.013586

    Abstract This manuscript deals with the effects of recycling on the static and dynamic properties of flax fibers reinforced thermoplastic composites. The corresponding thermoplastic used in this work is Elium resin. It’s the first liquid thermoplastic resin that allows the production of recycled composite parts with promising mechanical behavior. It appeared on the resin market in 2014. But until now, no studies were available concerning how it can be recycled and reused. For this study, a thermocompression recycling process was investigated and applied to Elium resin. Flax fiber-reinforced Elium composites were produced using a resin infusion… More >

  • Open Access


    Test and Analysis of the Sound Insulation Performance of Four Types of Timber Structure Floors under Jumping Excitation

    Yujie Huang1, Hao Zhu2, Dauletbek Assima4, Zheng Wang1,*, Minmin Li3, Xinyue Zhao1

    Journal of Renewable Materials, Vol.9, No.4, pp. 829-840, 2021, DOI:10.32604/jrm.2021.014610

    Abstract To improve the impact sound insulation performance of building floors and meet the objective requirements for living comfort of residents, in this article, three kinds of elastic cushion materials, Portuguese cork board, BGL insulation sound insulation foam board, and EPP polypropylene plastic foam board, are applied to the sound insulation of a light frame wood floor structure of the same bedroom and compared to the ordinary floor. This study uses the transfer function method and transient excitation method to measure the sound insulation, damping ratio, and elastic modulus of materials, as well as the sound… More >

  • Open Access


    Dynamic Elastic Modulus and Damping Ratio of Lignin-Modified Loess

    Qian Wang1,#,*, Zhaozhao Liu1,2,#,*, Xiumei Zhong1, Zhongnan Gao1, Fuqiang Liu2

    Journal of Renewable Materials, Vol.9, No.3, pp. 523-540, 2021, DOI:10.32604/jrm.2021.014114

    Abstract To effectively improve the poor engineering properties of loess and enhance its seismic performance, the industrial by-product lignin is used as a modified material. Based on lots of dynamic triaxial tests, the dynamic elastic modulus and damping ratio of lignin-modified loess were tested. The effects of lignin content on the dynamic elastic modulus and damping ratio of lignin-modified loess were analyzed. Combined with scanning electron microscopy (SEM) and X-ray diffraction (XRD), the microscopic mechanism of lignin to improve the dynamic properties of loess was studied. The results show that lignin can effectively modify the dynamic… More >

  • Open Access


    Damping Analysis and Failure Mechanism of 3D Printed Bio-Based Sandwich with Auxetic Core under Bending Fatigue Loading

    Khawla Essassi1,2,*, Jean-Luc Rebiere1, Abderrahim El Mahi1, Mohamed Amine Ben Souf2, Anas Bouguecha2, Mohamed Haddar2

    Journal of Renewable Materials, Vol.9, No.3, pp. 569-584, 2021, DOI:10.32604/jrm.2021.012253

    Abstract Meta-sandwich composites with three-dimensional (3D) printed architecture structure are characterized by their high ability to absorb energy. In this paper, static and fatigue 3-point bending tests are implemented on a 3D printed sandwich composites with a re-entrant honeycomb core. The skins, core and whole sandwich are manufactured using the same bio-based material which is polylactic acid with flax fiber reinforcement. Experimental tests are performed in order to evaluate the durability and the ability of this material to dissipate energy. First, static tests are conducted to study the bending behaviour of the sandwich beams, as well… More >

  • Open Access


    Ambient Vibration Testings and Field Investigations of Two Historical Buildings in Europe

    Ehsan Noroozinejad Farsangi1,*, Aleksandra Bogdanovic2, Zoran Rakicevic2, Angela Poposka2, Marta Stojmanovska2

    Structural Durability & Health Monitoring, Vol.14, No.4, pp. 283-301, 2020, DOI:10.32604/sdhm.2020.010564

    Abstract In this study, the methodology and results of ambient vibration-based investigations of the historical Tash Mosque in Kosovo and a 3-story historical building in Bulgaria are presented. The investigations include full-scale in situ testing of both structures due to ambient vibrations induced by micro-seismic, wind, traffic, and other human activities. To this aim, Ranger seismometers and Kinemetric products were used. Measurements were performed in both horizontal directions in several points along the structures’ height utilizing a high-speed data acquisition device. All recorded data have been analyzed and processed by the software developed at IZIIS, and More >

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