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Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Issue Info: 
  • Year: 

    2019
  • Volume: 

    7
  • Issue: 

    1
  • Pages: 

    1-9
Measures: 
  • Citations: 

    0
  • Views: 

    253
  • Downloads: 

    0
Abstract: 

In this paper, a new method is proposed for DOA estimation of correlated acoustic signals, in the presence of unknown spatial correlation noise. By generating a matrix from the signal subspace with the Hankel-SVD method, the correlated resource information is extracted from each eigenvector. Then a joint-diagonalization structure is constructed of the signal subspace and basis it, independent linear component, related to sources are recovered. Simulation results and comparisons with other commonly presented methods show the capability of this algorithm in low signal-to-noise ratio and close sources.

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Author(s): 

MAHMOODI M. | MONTAZERIN N.

Issue Info: 
  • Year: 

    2019
  • Volume: 

    7
  • Issue: 

    1
  • Pages: 

    10-18
Measures: 
  • Citations: 

    0
  • Views: 

    182
  • Downloads: 

    0
Abstract: 

The Research has shown that the primary sound source in centrifugal turbomachines is the blade passing frequency noise, which is caused by due to impac rotor exit flow with the volute and the wild pressure fluctuations. In this paper, a centrifugal blower with forward facing blades has been selected and the sound created by it in the output channel has been investigated in different operating conditions. Also, to study the relationship between the pressure fluctuations on the volute and the radiated sound, the amplitude of the pressure fluctuations in different volutes areas (from the cutt-off to the near-outlet channel) has been investigated. The results show remarkable noise at the blade passing frequency in all fan state modes. It also increases by increasing the fan outlet flow. The pressure fluctuations on the volute are also evidence of pressure in the blade passing frequency. The intensity of this pressure is reduced far from the volute tongue, which means that the flow of jet in those areas is lower. Also, at 300 degrees from the cut-off, a strong pressure fluctuation was observed that is the second primary source of the tonal sound (other than the cut-off).

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Author(s): 

MAHMOODI M. | MONTAZERIN N.

Issue Info: 
  • Year: 

    2019
  • Volume: 

    7
  • Issue: 

    1
  • Pages: 

    19-28
Measures: 
  • Citations: 

    0
  • Views: 

    452
  • Downloads: 

    0
Abstract: 

The widespread use of squirrel cage fans, especially in ventilation and home and industrial environments, has led to the formation of many research efforts to improve performance and reduce the sound produced by this type of fan. In the literature, the most important factor in generating sound in this category of fans is the confrontation between the rotor exit flow and the volute of the fan. In this research, a numerical study was conducted to solve the unsteady fluid flow inside the fan, calculate the pressure fluctuations on the fan body and the intensity of this pressure field in different areas of the body, the study of the contribution of different areas of the body to the sound field fan and, and estimate the sound field pattern of fan. The results show a fluctuating pressure on the volute that is due to the collision of the jet-wake rotor exit flow with the volute. Also, the maximum contribution of the cut-off adjacent regions was observed in the formation of a dipole sound radiation pattern. Another main observation was the insignificant rotor's contribution in sound filed compared to the volute.

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Issue Info: 
  • Year: 

    2019
  • Volume: 

    7
  • Issue: 

    1
  • Pages: 

    29-39
Measures: 
  • Citations: 

    0
  • Views: 

    436
  • Downloads: 

    0
Abstract: 

The purpose of this article is to provide an analytical model of the vibroacoustic for an elastic beam submerged in low subsonic flows with mean velocities. In general, vibroacoustic modeling refers to the combined effects of sound propagation and mechanical vibration of the structure. Sound radiations from submerged structures are coupled with physical phenomena because the sound pressures acting on structure surfaces and the dynamic responses of structures will impact each other. The Rayleigh Theory has been used to derive the beam vibration equations, and Green's functions are used to find the response of vibrations and the propagation of sound waves from the elastic beam. Initially, we solve the differential equation governing the Rayleigh beam under harmonic load. Then, the sound wave propagation equation around the beam is solved. The solution of the vibration and sound propagation differential equations must be done in the form of couplings so that at first distinct Green's function is obtained for each of the differential equations, and then by combining these two Green's functions, a coupled response function is found to solve the problem. Further, the vibroacoustic response of the beam was obtained by applying the boundary conditions at the interface between the beam and the fluid. In order to evaluate the process of analysis and validation, the results are compared with the results of other researchers and a good match between the results is observed; then, the effects of fluid velocity and useful parameters on the sound field have been investigated.

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Issue Info: 
  • Year: 

    2019
  • Volume: 

    7
  • Issue: 

    1
  • Pages: 

    40-49
Measures: 
  • Citations: 

    0
  • Views: 

    269
  • Downloads: 

    0
Abstract: 

Since it is too vital to the prevention of carotid disease in the vascular system, it seems necessary to the estimation of the elastic behavior of the carotid artery in head and neck external radiotherapy. In the present study, a total of 24 neck carcinoma patients treated with external radiotherapy had been studied. The carotid mean dose values were determined for each case by contouring the common carotid artery in consecutive CT scan images. Ultrasonography was performed from the wall region of each subject before and after the radiotherapy process. The instantaneous changes of intima-media thickness and radial movements in the arterial wall were extracted by the implementation of a maximum gradient algorithm. The results indicate that the normalized rate of absorbed dose of carotid from prescriptive dose is about 0. 82± 0. 24. Moreover, the normalized value of Young modulus of radiation-induced carotids compared to non-irradiated carotid arteries along with increasing the intima-media-thickness is 1. 58± 0. 21. These changes may be lead to stroke symptoms in the future.

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Author(s): 

TAGHAVI N.S. | AFZALZADEH R.

Issue Info: 
  • Year: 

    2019
  • Volume: 

    7
  • Issue: 

    1
  • Pages: 

    50-57
Measures: 
  • Citations: 

    0
  • Views: 

    182
  • Downloads: 

    0
Abstract: 

In this research, MoS2 nanoflakes were prepared via the Liquid Phase Exfoliation method by utilizing an ultrasonic probe. We changed the power of our sonicator and the sonication time to investigate their effects on the thickness of obtained flakes. Our findings from UV-Visible Spectra and the SEM images have indicated that the minimum thickness for these samples has been acquired at the power of 65 watts and the optimal irradiation duration is one hour.

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Issue Info: 
  • Year: 

    2019
  • Volume: 

    7
  • Issue: 

    1
  • Pages: 

    58-63
Measures: 
  • Citations: 

    0
  • Views: 

    300
  • Downloads: 

    0
Abstract: 

In this paper, the coating on glass slides by ultrasonic irradiation in the aqueous ZnO solution is discussed. We investigate the effect of irradiation location on the amount coating, and the role of heat on the coated slide. The structure and morphology of the thin film were obtained by using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The results showed that average diameter deposited particles on the glass slides (In beside and front of the ultrasonic probe), before and after heating is in the nanometer range.

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Author(s): 

SALEHI H. | Shojaienezhad F.

Issue Info: 
  • Year: 

    2019
  • Volume: 

    7
  • Issue: 

    1
  • Pages: 

    64-69
Measures: 
  • Citations: 

    0
  • Views: 

    266
  • Downloads: 

    0
Abstract: 

In this paper, a two-dimensional phononic crystal comprising of steel rod in water is investigated. Three cross-sections for this rod are considered using finite element method (EFM). We plot the equifrequency surface of the first band, because of equifrequency surface convex around the edge of the first Brillouin Zone, we guess the negative effective phononic mass and so negative refraction. Moreover, the negative refraction behaviors are demonstrated by the simulation of a phononic crystal slab. The results show the maximum intensity for the phononic crystal with the circle, square, and triangle cross-section, of 1. 15 MHz, 1. 11MHz and 1. 27MHz, respectively. The dependence of intensity and focal point distance on the slab thickness and between the source and the slab on the negative refractive is investigated. The results are in good agreement with other works.

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