The tonal noise or vibration of air-cooled or water-cooled chillers with rotary twin screw compressors is crucial for environmental concerns. This work aims to perform the receiver tests regarding the radiated noise and structural vibration due to the compressor in different operating conditions. The sound pressure near the compressor is recorded by the one-third octave and narrow band frequenc...

Materials and structures that strongly discriminate electromagnetic radiation based on one, or more of its properties (e.g. polarization, frequency) play an enabling role for a wide range of physical phenomena. For example, polarizers can selectively transmit light based on its polarization [1] over a wide range of frequencies; photonic crystals [2] (PhCs) can reflect light of certain frequenci...

air spindles are one of the main elements of precise machine tools. vibration of these spindles is one of the vital issues necessary for investigation. among parameters which influence air spindle vibrations are rotational speed, compression air method, input nozzle diameter, air gap pressure. in this study using ansys, the effects of air gap thickness on air spindle vibrations have been invest...

The analogy between electromagnetic wave propagation in multidimensionally periodic structures and electronwave propagation in real crystals has proven to be a fruitful one. Initial efforts were motivated by the prospect of a photonic band gap, a frequency band in three-dimensional dielectric structures in which electromagnetic waves are forbidden irrespective of the propagation direction in sp...

To analyze the rheological and mechanical properties as well vibration-mechanical forbidden zone effect of row pile foundations, this paper employs time-dependent modulus to examine mechanics soil. Drawing from viscoelastic theory, we derive expression deformation in frequency domain dependence shear soils. We construct a continuous medium dynamics model pile-soil periodic structure, taking int...

Periodic piezoelectric beams have been used for broadband vibration energy harvesting in recent years. In this paper, a periodic folded piezoelectric beam (PFPB) is introduced. The PFPB has special features that distinguish it from other periodic piezoelectric beams. The Adomian decomposition method (ADM) is used to calculate the first two band gaps andtwelve natural frequencies of the PF...

The structure and the electronic properties of single-walled zigzag BN and B3C2N3 nanotubes (n, 0; n=4–10) were investigated using first-principles calculations based on a density functional theory. A plane–wave basis set with periodic boundary conditions in conjunction with Vanderbilt ultrasoft pseudo-potential was employed. The energy gap of ZB3C<su...

This paper studies the potential of a periodic grid of vibration absorbers to achieve global plate vibration reduction. The global plate vibration reduction is pursued by applying the principles of resonance based stop bands. This principle is investigated both by infinite structure theory and by an example of a finite plate with a periodic grid of tuned resonators. Specific attention is paid t...

5% Fe- and Mn-doped nano-ZnS (Zn0.95A0.05S, A?=?Fe or Mn) was prepared using the thermolysis technique. The effect of Fe Mn doping on lattice parameter, crystallite size, microstrain examined applying Rietveld refinement. analysis showed incorporation substitutionally for Zn ions; a result confirmed by Fourier transforms infrared spectroscopy spectra from shift in vibration bands upon doping. e...