scholarly journals GEODYNAMICS

GEODYNAMICS ◽  
2011 ◽  
Vol 2(11)2011 (2(11)) ◽  
pp. 185-187
Author(s):  
Z.-Yu. Majbuk ◽  
Keyword(s):  
Noise Reduction ◽  
Electric Fields ◽  
Fault Zones ◽  
Experimental Investigations ◽  
Mechanical Tensions ◽  
Deflected Mode

Experimental investigations of fault zones in the polymetallic indications zone had shown the effectiveness of rocks deflected mode measurements control through observations and analysis of natural electric fields (NF) variations. Application of 4-electrodes compensated method of NF registration upraises sensitivity and noise reduction during measurements of local signals on the background of significant natural and artificial disturbances. Areas with increased non-stable mechanical tensions can be defined with this method.

Application of compact silencers as a noise barrier to a naturally ventilated double-skin façade

2021 ◽  
Vol 69 (3) ◽  
pp. 220-228
Author(s):  
Jeehwan Lee ◽  
Jae D. Chang ◽  
Robert Coffeen
Keyword(s):  
Noise Reduction ◽  
Surface Area ◽  
Natural Ventilation ◽  
Experimental Investigations ◽  
Test Case ◽  
Open Surface ◽  
Low Frequencies ◽  
Noise Barrier ◽  
Double Skin ◽  
Air Vent

A prior study of the acoustical performance of a double-skin facade (DSF) as a noise barrier was carried out based on the percentage of the air vent open surface area, shading louver configurations, and shading louver surface materials. Earlier research findings led to experimental investigations of the acoustical performance capabilities of compact silencers to replace DSF air vents as both noise barriers and air channels because DSF air cavities, which contribute to natural ventilation performance (e.g., wind-driven or buoyancy-driven performance), are acoustically vulnerable to noise transmitted through the air vents. This experimental investigation aims to explore noise reduction (NR) through compact silencers applied to DSF air vents. Double-skin facade mock-up test cases were designed based on three test scenarios of a ventilation open surface area: (1) a 100%air vent open surface area (open mode), (2) a 0% air vent open surface area (closed mode), and (3) a compact silencer. From a data analysis of DSF mock-up test results, the overall NR values of a DSFmock-up ranged from20 to 37 dB(A) depending on the number of compact silencers and the shading louver orientation used. Configurations of compact silencers and shading louvers helped the DSF mock-up achieve additionalNR values of 5 to 10 dB(A) depending on the test case. Moreover, applying compact silencers to a naturally ventilated DSF mock-up led to significant noise reduction at low frequencies (125Hz).

PRACTICAL METHODS OF ACOUSTIC MATERIALS PATTERNING FOR INCREASE OF THEIR EFFECTIVENESS

Akustika ◽  
2021 ◽  
pp. 107-111
Author(s):  
Aleksandr Krasnov ◽  
Igor Deryabin
Keyword(s):  
Noise Reduction ◽  
Laboratory Scale ◽  
Experimental Investigations ◽  
Passenger Cars

This article includes the results of experimental investigations of patterned noise-reducing materials and components, carried out using special-purpose laboratory-scale bench plants (Alpha Cabin, Torre di Pisa, RTC-3, Oberst). Illustrative examples of constructive-technological structurization of the components (gaskets, panels and upholstery) providing noise reduction of passenger cars are given.

scholarly journals Role of the magnetospheric and ionospheric currents in the generation of the equatorial scintillations during geomagnetic storms

2004 ◽  
Vol 22 (9) ◽  
pp. 3195-3202 ◽  
Author(s):  
L. Z. Biktash
Keyword(s):  
Solar Wind ◽  
Electric Fields ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Equatorial Ionosphere ◽  
Experimental Investigations ◽  
Polar Regions ◽  
Ionospheric Currents ◽  
Geomagnetic Variations ◽  
Activity Effect

Abstract. The equatorial ionosphere parameters, Kp, Dst, AU and AL indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the geomagnetic activity effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict near 70% of scintillations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of electron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind - magnetosphere - ionosphere during magnetic storms have progressed greatly. According to present view, the intensity of the electric fields and currents at the polar regions, as well as the magnetospheric ring current intensity, are strongly dependent on the variations of the interplanetary magnetic field. The magnetospheric ring current cannot directly penetrate the equatorial ionosphere and because of this difficulties emerge in explaining its relation to scintillation activity. On the other hand, the equatorial scintillations can be observed in the absence of the magnetospheric ring current. It is shown that in addition to Aarons' criteria for the prediction of the ionospheric scintillations, models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere currents and the solar wind.

scholarly journals Experimental investigations on electrorheological properties of lubricating oils containing ionic liquid. Part. 1. Investigations with modified Brookfield DV-III Ultra Viscosimeter

2019 ◽  
Vol 68 (3) ◽  
pp. 35-63
Author(s):  
Jarosław Juda ◽  
Tomasz Jan Kałdoński ◽  
Tadeusz Kałdoński
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Electric Fields ◽  
Experimental Investigations ◽  
Lubricating Oils ◽  
Liquid Part ◽  
Special Stand ◽  
Electrorheological Properties ◽  
Selection Of

The results of experimental investigations on electrorheological (ER) properties of lubricating oils which contain ionic liquids, are presented in this article. The investigations were carried out on the special stand which was projected for this aim. On this stand there was used the modified Brookfield viscosimeter. Electrorheological properties of two mixtures were tested, i.e., silicone damping liquid GP-1 which is polimethylsiloksane mixture containing 2% (v/v) of ionic liquid CJ 001, i.e., tetrafluoroboran 1-methyl-3-octyloxymethylimidazolium as well as base polialfaolefine oil PAO-6 which contains 2% (v/v) of ionic liquid CJ 008, i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide. Selection of components of both mixtures was based on the results of investigations of miscible and on evaluation of basic phys-chem properties. The investigations showed that the made mixtures have generated the ER effect, but it was short-lived effect, suggesting the changes of inner structure of these mixtures. Therefore, we have planned the next investigations, among others dielectric spectroscopy and microscope observations in situ of these mixtures in external electric fields. The aim of those investigations will be to record the fading ER effect and to understand this mechanism. Keywords: electrorheological effect, homogenous mixtures, lubricants, ionic liquids

Sample Flow Switching Technique Based on Combined Effect of Hydrodynamic and Electroosmosis

2009 ◽  
Author(s):  
Haiwang Li ◽  
Teck Neng Wong ◽  
Nam-Trung Nguyen
Keyword(s):  
Fluorescence Imaging ◽  
Electric Fields ◽  
Imaging Technique ◽  
Combined Effect ◽  
Experimental Investigations ◽  
Rectangular Microchannel ◽  
Silicon Oil ◽  
External Electric Fields ◽  
Sample Stream ◽  
Microfluidic Switch

This paper presents theoretical and experimental investigations on valveless microfluidic switch using the coupled effect of hydrodynamics and electroosmosis. In the experiment, two sheath streams (aqueous NaCl and glycerol) and the sample stream (silicon oil) are introduced by syringe pumps to flow side by side in a straight rectangular microchannel. External electric fields are applied on the two sheath streams. Under the constant inlet volumetric flowrates, the sample stream is delivered to the desired outlet ports using electroosmotic effect. The liquid fractions of sheath streams are measured using fluorescence imaging technique. The results indicate that under suitable cooperation of electric fields, the sample stream can be delivered to the desired outlet ports.

scholarly journals Prediction of noise from serrated trailing edges

2016 ◽  
Vol 793 ◽  
pp. 556-588 ◽  
Author(s):  
B. Lyu ◽  
M. Azarpeyvand ◽  
S. Sinayoko
Keyword(s):  
Noise Reduction ◽  
Analytical Model ◽  
Leading Edge ◽  
Experimental Investigations ◽  
Destructive Interference ◽  
Trailing Edge ◽  
Trailing Edges ◽  
Mach Numbers ◽  
Trailing Edge Serrations ◽  
High Mach

A new analytical model is developed for the prediction of noise from serrated trailing edges. The model generalizes Amiet’s trailing-edge noise theory to sawtooth trailing edges, resulting in a complicated partial differential equation. The equation is then solved by means of a Fourier expansion technique combined with an iterative procedure. The solution is validated through comparison with the finite element method for a variety of serrations at different Mach numbers. The results obtained using the new model predict noise reduction of up to 10 dB at 90$^{\circ }$ above the trailing edge, which is more realistic than predictions based on Howe’s model and also more consistent with experimental observations. A thorough analytical and numerical analysis of the physical mechanism is carried out and suggests that the noise reduction due to serration originates primarily from interference effects near the trailing edge. A closer inspection of the proposed mathematical model has led to the development of two criteria for the effectiveness of the trailing-edge serrations, consistent but more general than those proposed by Howe. While experimental investigations often focus on noise reduction at 90$^{\circ }$ above the trailing edge, the new analytical model shows that the destructive interference scattering effects due to the serrations cause significant noise reduction at large polar angles, near the leading edge. It has also been observed that serrations can significantly change the directivity characteristics of the aerofoil at high frequencies and even lead to noise increase at high Mach numbers.

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