https://rjav.sra.ro/index.php/rjav/issue/feed Romanian Journal of Acoustics and Vibration 2020-12-30T20:39:02+02:00 Ovidiu VASILE office@sra.ro Open Journal Systems <p>The&nbsp;<strong>Romanian Journal of Acoustics and Vibration (Print ISSN 1584-7284;&nbsp; Online ISSN 2602-0351)</strong> is the referred journal of the Romanian Society of Acoustics (<strong>SRA</strong>).</p> https://rjav.sra.ro/index.php/rjav/article/view/233 CHALLENGES OF ETHICS IN CURRENT RESEARCH 2020-12-30T14:43:35+02:00 Zoltan Iosif KORKA zoltan.korka@ubbcluj.ro <p>Nowadays, we experience a worldwide upward trend in the requirements of ethics in scientific research represented by a series of international treaties and pacts. All these demands are an expression of the involvement and commitment of international bodies at the highest levels regarding the assumption of a set of ethical rules.<br>Thus, following international bodies have developed documents that reflect ethical issues in scientific research: the European Commission, the Organization for Economic Co-operation and Development (OECD), the United Nations Educational, Scientific and Cultural Organization<br>(UNESCO), the World Health Organization (WHO), Food and Agriculture Organization of the United<br>Nations (FAO) and the Forum of National Ethics Councils (NEC Forum).</p> 2020-12-30T00:00:00+02:00 ##submission.copyrightStatement## https://rjav.sra.ro/index.php/rjav/article/view/97 Enhancement of Vibration Characteristics of an Air Filter Box Utilizing Numerical Analysis 2020-12-30T14:42:47+02:00 Sajjad BEIGMORADI s.beigmoradi@email.kntu.ac.ir Mehrdad VAHDATI vahdati@kntu.ac.ir <p>Air intake system (AIS) that prepares clean air for engine aspiration, plays an important role in internal combustion engines.&nbsp; It contributes in different aspects of engine’s attributes such as fuel consumption, engine power, Engine pollution and engine noise and vibration. Powertrain system is known as one the main source of the noise and vibration in the vehicle. So, enhancement of the engine NVH characteristics provides passenger’s comfort. AIS is one of the component that generates significant noise and vibration due to connecting to the engine and passing transient air flow. Therefore, tuning this system decreases vehicle sound and vibration level noticeably. In this paper, in the first step modal analysis of a concept filter box is conducted and some modifications is proposed to enhance vibration performance of this system. At the next stage, frequency response function (FRF) analysis is performed to survey sensitivity of the air box structure due to these modifications and finally suitable air filter box is chosen. To this end, finite element method (FEM) is applied.</p> 2020-12-30T14:42:47+02:00 ##submission.copyrightStatement## https://rjav.sra.ro/index.php/rjav/article/view/92 Evaluation of a New Balancing Technique for Overhang Impellers through Frequency Response Function 2020-12-30T14:53:32+02:00 Ahmed A. IBRAHEEM Ahmed.naem0@gmail.com Nouby M. GHAZALY Nouby.ghazaly@eng.svu.edu.eg Gamal T. ABD EL- JABER Nouby.ghazaly@eng.svu.edu.eg <p>The main objective of this research paper is to evaluate the new suggested balancing method and compare it with three conventional methods. In this research paper, the details of the test rig facility for the experimental balancing simulator are discussed. It starts by describing the test rig components and summarizing the main specifications of the unit configuration under the test of mass unbalance conditions. Then, it explains the instrumentation of the balancing and vibration measurement by describing each component involved. Finally, four balancing methods namely; Conventional software method, four-run methods, mathematical method, and frequency response function method are conducted under different operating conditions. It is found that the new balancing using frequency response function method comparing with other conventional methods has some advantages like less downtime required, less risk as no trial weight required, low cost and easy to use.</p> 2020-12-30T14:53:32+02:00 ##submission.copyrightStatement## https://rjav.sra.ro/index.php/rjav/article/view/103 Evaluation of Optimum Model and Conditions Providing Increasing Ultrasonic Cavitation Area in High-Viscous and Non-Newtonian Fluids 2020-12-30T15:05:50+02:00 Roman Nikolaevich GOLYKH romangl90@gmail.com Andrey SHALUNOV shalunov@bti.secna.ru Vladimir KHMELEV vnh@bti.secna.ru Roman LOPATIN Exsecrabilis01@yandex.ru Vyacheslav MINAKOV slava2926@mail.ru Vladislav SHAKURA shakura.va@bti.secna.ru <p>The aim of this work is to improve the efficiency of chemical technology processes implemented in high viscosity or non-Newtonian fluids by identifying modes and conditions of ultrasonic action, which provide an increase in the volume of the cavitation area formed. As a result of the research, a phenomenological model of cavitation area formation in the non-Newtonian medium has been developed. The analysis of the model allows to calculate the optimal intensity of ultrasonic action (for linear-viscous fluids, the optimal intensity ranges from 1.6 to 80 W/cm<sup>2</sup>; for nonlinear-viscous fluids up to 120 W/cm<sup>2</sup>) and the distance (60-125 cm) between the irradiating surface and the reflecting boundary providing the maximum cavitation area volume. In finish the model was confirmed experimentally.</p> 2020-12-30T15:05:50+02:00 ##submission.copyrightStatement## https://rjav.sra.ro/index.php/rjav/article/view/122 The Effects of Number and Location of Bracing Bays on Redundancy of Eccentrically-Braced Steel Moment Frames 2020-12-30T15:13:53+02:00 Alireza FAROUGHI faroughi@gmail.com Abdolreza S. MOGHADAM Moghdam@iiees.ac.ir Mohammd GHANOONIBAGHA ghanoonibagha@alumni.iust.ac.ir <p>Steel braced frames are among the most effective lateral load resisting systems. The eccentrically braced frame has a higher ductility, less stiffness, and a better serviceability (limited retrofitting needed after the seismic excitations) compared to concentrically braced ones. Static indeterminacy is generally considered as the number of extra constraints or members in a structural system. In other words, redundancy is the ability of a structure to keep its stability after the onset of the failure or removal of its lateral load resisting elements, preventing it from collapse in the initial stages of loading. The redundancy of a system depends on the “dynamic” characteristics of its structure and properties of the applied earthquake excitations as well as its structural geometric features and details. This indeterminacy is called dynamic redundancy.</p> <p>In this study, the effects of the number and location of braced bays on redundancy were investigated to obtain the best pattern for regular 5 and 8-story buildings using nonlinear analysis. It also develops a relationship for the redundancy factor of the dual structural systems. Results show that position of braced bays is more effective on redundancy than the number of bays. It is also concluded that the building’s height affects the required number of bracing bays. The study also showed that the dynamic redundancy is different from the over-strength. According to the results of this research, for dual structural systems, it is recommended not to arrange the braces only in the perimeter of the plan.</p> 2020-12-30T15:13:53+02:00 ##submission.copyrightStatement## https://rjav.sra.ro/index.php/rjav/article/view/123 Calibration and Uncertainty Estimation for The Reference Sound Source in Reverberation Room 2020-12-30T15:19:36+02:00 Tarek Mohamed El-Basheer Hussein tarek31.uv@gmail.com <p>Since room acoustic parameters require the sound power of the sound source. Few trials to publish the way of calibration and uncertainty estimation in details for the reference sound source.&nbsp; So, it is very interesting to find a way to calibrate the reference sound source that can be used in different acoustic measurements. Also, there is a need to find the value uncertainty of due to the calibration of reference sound source. Sound power level of any sound source can be determined by means of sound pressure level measurements performed in accordance to relevant ISO standards. The calibration of reference sound source according to ISO 6926 in a hemi-anechoic or reverberation room. In this case I only have the access to reverberation room, so the decision was to perform measurements at reverberation room. Kinds of measurement surfaces, enveloping the noise source, number of microphones and their positions over the measurement and the method for calculations of sound power are stated .Measurements of sound pressure level, reverberation time and background noise level were performed using traceable instruments by direct method in ISO3741. Then the calculation of sound power level in 1/3 octave band frequency was carried out for the reference sound source side by side with uncertainty contributions resulting from measurements. The values of uncertainty (Sigma&nbsp;<sub>R0 ,</sub>&nbsp;Sigma&nbsp;<sub>omc</sub>)&nbsp; respectively are in order of magnitude of&nbsp; 0.4 and 0.07 dB. The total uncertainty lies within the range of 0.7-1.0dB in the 1/3 octave band frequency from 125Hz to 10000Hz.&nbsp;</p> 2020-12-30T15:19:36+02:00 ##submission.copyrightStatement## https://rjav.sra.ro/index.php/rjav/article/view/136 Frequency Dependence Studies of Acoustical and Thermo-Dynamical Parameters of The Binary Mixtures of Isopropyl Sulphide And Acetic Acid 2020-12-30T20:18:51+02:00 Arun UPMANYU arunupmanyu@gmail.com Monika DHIMAN monika.dhiman@chitkara.edu.in Dev Priya GUPTA dp.gupta@chitkara.edu.in Mohit Kumar KAKKAR mohit.kakkar@chitkara.edu.in Kuljeet SINGH chakkal.ks@gmail.com Devinder Pal SINGH drdpsn@gmail.com <p>Using thermal expansivity and ultrasonic velocity data for the binary mixtures of isopropyl sulphide and acetic acid, at room temperature, a number of acoustical and thermo-dynamical parameters such as Moelwyn-Hughes parameter (<em>C<sub>1</sub></em>)<em>, </em>reduced volume ( ), fractional free volume (<em>f</em>)<em>, </em>repulsive exponent (<em>n</em>)<em>, </em>Sharma’s constants (<em>S<sub>0</sub></em>)<em>, </em>isobaric (<em>G<sub>b</sub></em>)<em>, </em>isochoric <em>&nbsp;</em>(<em>G<sub>c</sub></em>)<em>, </em>isothermal Gruneisen parameters (<em>G<sub>T</sub></em>), Bayer’s non-linear parameter (<em>B/A</em>), Lattice Gruneisen parameters (<em>G¢</em>), cohesive energy density (<em>e<sub>i</sub></em>) and interaction parameter (<em>z ) </em>has been evaluated. The frequency dependence of these parameters has been investigated at various concentrations of the binary mixture under study, within the frequency range 1-7 MHz. The variations of these parameters with change in the composition of the mixture and variation of frequency of the ultrasonic waves, propagating in the medium, have been used to explain the molecular interactions, anharmonicity and structural information about the systems under study. The obtained results indicate a decrease in intramolecular modes of vibration and anharmonicity in liquid mixture at higher frequency. These also suggest that binary mixture of isopropyl sulphide and acetic acid becomes less associative and hence weak interaction forces dominate at higher frequency.</p> 2020-12-30T20:18:51+02:00 ##submission.copyrightStatement## https://rjav.sra.ro/index.php/rjav/article/view/166 Vibration and Stability Analysis of Multi Walled Piezoelectric Nanoresonator 2020-12-30T20:31:12+02:00 Sayyid H. HASHEMI KACHAPI sha.hashemi.kachapi@gmail.com <p>In this work, vibration and stability analysis of multi walled piezoelectric nanoresonator (MWPENR) based on cylindrical nano-shell is investigated using the Gurtin–Murdoch surface/interface theory and also other nonclassical theories such as nonlocal (NLT) and nonlocal strain gradient (NSGT) approaches. The nanoresonator is embedded in visco-Pasternak medium, the nonlinear van der Waals (vdW) and electrostatic forces. Hamilton’s principle is used for deriving of the governing equations and boundary conditions and also the assumed mode method is used for changing the partial differential equations into ordinary differential equation. The influences of the surface/interface effect, piezoelectric voltage, boundary conditions, the length to radius ratio, the nanoresonator gap width and other parameters are studied on the frequency and stability analysis of MWPENR. It is found that in all boundary conditions, higher surface/interface densities leads to reduction of MWPENR stiffness, as a result cause to decreasing of the dimensionless natural frequency and pull in voltage compared to case of without S/I effects. Also, with increasing of &nbsp;ratio and the piezoelectric voltage , and decreasing of &nbsp;ratio, due to increasing of MWPENR stiffness, the pull-in voltages of the piezoelectric nanoresonator is increased.</p> 2020-12-30T20:31:12+02:00 ##submission.copyrightStatement## https://rjav.sra.ro/index.php/rjav/article/view/178 A Method for Signal Stationarity Estimation 2020-12-30T20:39:02+02:00 Hristo ZHIVOMIROV hristo_car@abv.bg Ivaylo NEDELCHEV iynedelchev@abv.bg <p>In the paper, a novel estimation method is proposed, concerning the wide-sense stationarity test of the signals. Background information is given about the concept of stationarity of the processes and signals. The problem of the signal stationarity estimation is addressed along with criticism of the available stationarity tests. Further, a new wide-sense stationarity estimation method is described, involving estimation of the mean-, variance- and autocovariance- stationarity of a signal. Finally, a few representative signals are tested and the results clearly indicate the consistence of the proposed test method. It is implemented in Matlab<sup>®</sup>-environment and can be download and use for free.</p> 2020-12-30T20:36:20+02:00 ##submission.copyrightStatement##