scholarly journals The analysis of dynamics of periodic fluid-loaded flexible tubes

2020 ◽  
Vol S-I (2) ◽  
pp. 272-275
Author(s):  
S. Avetisov ◽  
◽  
S. Sorokin ◽  
Keyword(s):  
Floquet Theory ◽  
Tensile Force ◽  
Stop Band ◽  
Periodicity Cell ◽  
Acoustic Metamaterial ◽  
Eigenmode Analysis ◽  
Soft Segments ◽  
Inner Diameter ◽  
Analysis Of Dynamics ◽  
Flexible Tubes

In this report, we consider a periodic tube consisting of absolutely rigid sections alternated with soft segments of the same inner diameter under the action of a tensile force. The purpose of this analysis is to explore possibilities to suppress wave propagation using this complex tube model as a muffler. Its waveguide properties are assessed by means of a mathematical model formulated in the framework of Floquet theory and the results are compared with the eigenfrequency and eigenmode analysis of a unit symmetric periodicity cell. The setup consisting of these alternating sections creates the stop band effect, so that it may be called a ‘macroscale acoustic metamaterial’.

scholarly journals EXPERIMENTAL INVESTIGATION OF AN ACOUSTIC METAMATERIAL BARRIER DESIGN COMPOSED OF A SQUARE PRISM WITHIN A HEXAGONAL RECESS

2021 ◽  
Vol 11 (3) ◽  
pp. 57-70
Author(s):  
Luo Mu ◽  
Zamir Aimaduddin Zulkefli ◽  
Nawal Aswan Abdul Jalil ◽  
Azma Putra ◽  
Muhammad Nur Othman ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Absorption Coefficient ◽  
Transmission Loss ◽  
Stop Band ◽  
Unit Cell ◽  
Acoustic Absorption ◽  
Acoustic Metamaterial ◽  
Square Prism ◽  
Peak Transmission ◽  
Single Material

This paper presents an experimental investigation of an acoustic barrier composed out of an acousticmetamaterial unit cell. The design of the unit cell consists of a square prism, acting as a resonator,within a hexagonal recess manufactured out of a single material. Two materials were used tomanufacture the unit cell: PolyMide Polycarbonate and Polylite Polylactic Acid. The acousticperformance of the unit cell was quantified for both materials using the acoustic absorptioncoefficient and acoustic transmission loss values for frequencies between 100 Hz and 5,000Hz. Theexperimental results indicate that the design reduced the peak absorption coefficient for bothmaterials while also introducing two additional peaks at around 1,500 Hz and at 4,000 Hz. Changesto the absorption coefficient values were observed for frequencies above 1,000 Hz while minimalchanges were observed for frequencies below 1,000 Hz. These results indicate that the proposeddesign, is able to widen the effective frequency band, or stop band for acoustic absorption forfrequencies above 1,000 Hz compared to the absorption coefficient of the material. The experimentalresults also indicate that the design increases the peak transmission loss by about 7 dB at 4,000 Hz.For sounds below 3,000 Hz, the design will only change the transmission loss by about 3 dB forfrequencies between 100 Hz to 3,000 Hz. These results indicate that the acoustic metamaterial design,consisting of resonator in a recess manufactured out of a single material, is able to broaden theeffective frequency range for sound absorption for frequencies between 1,000 Hz and 4,000 Hz andat increasing the transmission loss values for frequencies between 3,000 Hz and 5,000 Hz. It can beconcluded that the resonator in recess metamaterial design, manufactured out of a single material,can be used to increase the stop band for acoustic absorption for frequencies above 1,000 Hz and toincrease the transmission loss for frequencies above 3,000 Hz.

scholarly journals Control of Flow Limitation in Flexible Tubes

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Ruo-Qian Wang ◽  
Teresa Lin ◽  
Pulkit Shamshery ◽  
Amos G. Winter
Keyword(s):  
Flow Rate ◽  
Control Flow ◽  
Lumped Parameter Model ◽  
Needle Valve ◽  
Flow Limitation ◽  
Lumped Parameter ◽  
Inner Diameter ◽  
Series Of Experiments ◽  
Flexible Tubes ◽  
Tube Geometry

This paper proposes a new Starling resistor architecture to control flow limitation in flexible tubes by introducing a needle valve to restrict inlet flow. The new architecture is able to separately control the activation pressure and the flow rate: The tube geometry determines the activation pressure and the needle valve determines the flow rate. A series of experiments were performed to quantify the needle valve and the tube geometry's effect on flow limitation. The examined factors include the inner diameter, the length, and the wall thickness. A lumped-parameter model was developed to capture the magnitude and trend of the flow limitation, which was able to satisfactorily predict Starling resistor behavior observed in our experiments.

Can trust become a factor of economic growth? Dynamic changes in the level of trust of Russian youth

2020 ◽  
pp. 92-107 ◽  
Author(s):  
A. I. Bakhtigaraeva ◽  
A. A. Stavinskaya
Keyword(s):  
Institutional Environment ◽  
Negative Effects ◽  
Dynamic Changes ◽  
Generalized Trust ◽  
Level Of Education ◽  
Advantages And Disadvantages ◽  
The Future ◽  
Analysis Of Dynamics

The article considers the role of trust in the economy, the mechanisms of its accumulation and the possibility of using it as one of the growth factors in the future. The advantages and disadvantages of measuring the level of generalized trust using two alternative questions — about trusting people in general and trusting strangers — are analyzed. The results of the analysis of dynamics of the level of generalized trust among Russian youth, obtained within the study of the Institute for National Projects in 10 regions of Russia, are presented. It is shown that there are no significant changes in trust in people in general during the study at university. At the same time, the level of trust in strangers falls, which can negatively affect the level of trust in the country as a whole, and as a result have negative effects on the development of the economy in the future. Possible causes of the observed trends and the role of universities are discussed. Also the question about the connection between the level of education and generalized trust in countries with different quality of the institutional environment is raised.

Comparison of the Aditus ad Antrum Diameter on CT between Patients with Chronic Otitis Media and Healthy Individuals

2019 ◽  
Vol 15 (10) ◽  
pp. 990-993 ◽  
Author(s):  
Elif Gündoğdu ◽  
Uğur Toprak
Keyword(s):  
Computed Tomography ◽  
Otitis Media ◽  
Middle Ear ◽  
Healthy Subjects ◽  
Normal Values ◽  
Chronic Otitis Media ◽  
Healthy Individuals ◽  
Inner Diameter ◽  
Male Patients ◽  
The Right

Background: The middle ear cavity is ventilated through the aditus ad antrum. Aditus blockage contributes to the pathology of otitis media. Objective: To determine the normal values of the aditus ad antrum diameter on computed tomography and to investigate its relationship with chronic otitis media and related pathologies (tympanosclerosis and myringosclerosis). Methods: The temporal CT images of 162 individuals were evaluated retrospectively. In the axial sections, the inner diameter of the aditus was measured at the narrowest point at the cortex. The differences in diameter were compared between diseased and healthy ears. Results: In healthy individuals, the diameter was narrower in women. There was no difference between the right and left ears in healthy subjects. No correlation was found between age and diameter. In male patients with myringosclerosis, the diameter was slightly narrower on both sides but more marked on the left. In female patients with myringosclerosis, the diameter in both ears was slightly narrower. In cases of otitis media and tympanosclerosis, the diameter was less than that of healthy individuals, despite the lack of statistically significant result in all cases. Conclusion: The aditus ad antrum was narrower in diseased ears, indicating that a blocked aditus may contribute to the development of otitis media, as well as mucosal diseases.

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