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This paper aims to Separation and sorting of biological cells is desirable in many applications for analyzing cell properties, such as disease diagnostics, drugs delivery, chemical processing and therapeutics.

Acoustic energy-based bioparticle separation is a simple, viable, bio-compatible and contact-less technique using, which can separate the bioparticles based on their density and size, with-out labeling the sample particles.

Conventionally available bioparticle separation techniques as fluorescence and immunomagnetic may cause a serious threat to the life of the cells due to various compatibility issues. Moreover, they also require an extra pre-processing labeling step. Contrarily, label-free separation can be considered as an alternative solution to the traditional bio-particle separation methods, due to their simpler operating principles and lower cost constraints. Acoustic based particle separation methods have captured a lot of attention among the other reported label-free particle separation techniques because of the numerous advantages it offers.

This study tries to briefly cover the developments of different acoustic-based particle separation techniques over the years. Unlike the conventional surveys on general bioparticles separation, this study is focused particularly on the acoustic-based particle separation. The study would provide a comprehensive guide for the future researchers especially working in the field of the acoustics, in studying and designing the acoustic-based particle separation techniques.

The study insights a brief theory of different types of acoustic waves and their interaction with the bioparticles is considered, followed by acoustic-based particle separation devices reported till the date. The integration of acoustic-based separation techniques with other methods and with each other is also discussed. Finally, all major aspects like the approach, and productivity, etc., of the adopted acoustic particle separation methods are sketched in this article.

Limitations in traditional manufacturing methods currently employed in the production of acoustic devices, restricts the development of design led performance improvements. These devices are used to control sound energy and are commonly employed for tailoring room acoustics. solid freeform fabrication allows the production of acoustic structures more complex than traditionally manufactured devices. This paper aims to focus on a novel absorber based on destructive interference, considering performance, design and manufacture.

Selective laser sintering has been used in the investigation of the performance and manufacturing possibilities and limitations of a novel destructive interference absorber. Validation of the absorber performance is benchmarked against a conventional resonant absorber and compared to published results. The implications for acoustic devise design, the advances and limitations in manufacture using solid freeform fabrication techniques and potential applications are discussed.

An original absorber design has been shown to exhibit comparable acoustic absorption to that of a traditional solution. The nature of the geometry of the novel absorber demonstrates that the design flexibility afforded by solid freeform fabrication processes holds potential for applications incorporating new types of acoustic absorber. The use of solid freeform fabrication has demonstrated its potential to the application of acoustics, and has highlighted limitations due to post‐processing, material strength and the precision of the selectivity process.

Solid freeform fabrication techniques enable a new family of specifically engineered acoustic absorbers capable of incorporating performance benefits over conventional absorbers.

This paper focuses on room acoustic applications, the creation of high performance, conformal absorbers, applicable to a wide range of applications within the aerospace, automotive and construction industries, where space, weight and performance are key criteria.

The bulk of jet engine noise developed at high powers arises from the turbulent mixing of the jet efflux in the surrounding air, as judged from model experiments, and has a continuous spectrum with a single flat maximum. The high frequency sound arises from fairly close to the orifice, and reaches its maximum intensity at fairly large acute angles to the jet direction. Lower frequency noise arises from lower down stream and its maxima make smaller acute angles with the jet axis. The possible origins are briefly discussed in view of Lighthill's theory and refraction effects. The most intensesound has a wave‐length of the order of three or four exit diameters, and originates between five and ten diameters from the orifice. A semi‐empirical rule of noise energy depending on the jet velocity to the eighth power and the jet diameter squared gives a rough estimate of the noise level for both cold and heated jets. Further noise from heated or supersonic jets may occur through eddies travelling at supersonic speed and so producing small Shockwaves. Model experiments have shown that interaction between shock‐wave configurations in choked jets and passing eddy trains generates sound and this initiates further eddies at the orifice. The directional properties of this sound are quite distinctive, the maximum being in the upstream direction. Methods of reducing jet noise are briefly discussed.

The objective of this study is to model the influence of free gas, in the form of size‐distributed fine bubbles, on sound attenuation and dispersion in a thin‐walled elastic cylindrical tube filled with viscoelastic polymeric liquid.

Sound wave propagation in the system is described within a three‐phase interaction scheme, based on a quasi‐homogeneous approach to liquid‐gas mixture dynamics in the wave. Coupled equations of tube wall deformations and viscoelastic liquid dynamics in the tube are solved using a long‐wave approximation. The dissipative losses, stemming from flow gradients in the wave, as well as from non‐equilibrium bubble‐liquid interaction, are accounted for. The dispersion equation for the waveguide is obtained and studied numerically.

The results of the study indicate that bubble‐size distribution in viscoelastic liquid has an essential impact on sound propagation in the tube at sufficiently high frequencies. The frequency range in which the mixture heterogeneity influences the acoustic properties of the system is sensitive to both the distribution parameters and the rheological properties of the liquid. As distinct to polydispersity features, the viscoelastic properties of liquid are also relevant in the low‐frequency range, where they lead to an increase of the wave speed and a decrease of its attenuation.

A model of sound wave propagation in a tube filled with a heterogeneous viscoelastic liquid‐bubble mixture is formulated. The study provides a basis for modeling transient processes in tubes filled with polymeric liquids containing free gas, and for acoustic control of certain processes in polymer technologies.

The purpose of this article is to investigate the propagation characteristics (such as particle motion, attenuation and phase velocity) of a Rayleigh wave in a nonlocal generalized thermoelastic media.

The bulk waves are represented with Helmholtz potentials. The stress-free insulated and isothermal plane surfaces are taken into account. Rayleigh wave dispersion relation has been established and is found to be complex. Due to the presence of radicals, the dispersion equation is continuously computed as a complicated irrational expression. The dispersion equation is then converted into a polynomial equation that can be solved numerically for precise complex roots. The extra zeros in this polynomial equation are eliminated to yield the dispersion equation’s roots. These routes are then filtered for inhomogeneous wave propagation that decays with depth. To perform numerical computations, MATLAB software is used.

In this medium, only one mode of Rayleigh wave exists at both isothermal and insulated boundaries. The thermal factors of nonlocal generalized thermoelastic materials significantly influence the particle motion, attenuation and phase velocity of the Rayleigh wave.

Numerical examples are taken to examine how the thermal characteristics of materials affect the existing Rayleigh wave’s propagation characteristics. Graphical analysis is used to evaluate the behavior of particle motion (such as elliptical) both inside and at the isothermal (or insulated) flat surface of the medium under consideration.

The purpose of this study is to investigate the reflection of plane waves in a double-porosity (DP) thermoelastic medium.

To derive the theoretical formulas for elastic wave propagation velocities through the potential decomposition of wave-governing equations. The boundary conditions have been designed to incorporate the unique characteristics of the surface pores, whether they are open or sealed. This approach provides a more accurate and realistic mathematical interpretation of the situation that would be encountered in the field. The reflection coefficients are obtained through a linear system of equations, which is solved using the Gauss elimination method.

The solutions obtained from the governing equations reveal the presence of five inhomogeneous plane waves, consisting of four coupled longitudinal waves and a single transverse wave. The energy ratios of reflected waves are determined for both open and sealed pores on the stress-free, the thermally insulated surface of DP thermoelastic medium. In addition, the energy ratios are compared for the cases of a DP medium and a DP thermoelastic medium.

A numerical example is considered to investigate the effect of fluid type in inclusions, temperature and inhomogeneity on phase velocities and attenuation coefficients as a function of frequency. Finally, a sensitivity analysis is performed graphically to observe the effect of the various parameters on propagation characteristics, such as propagation/attenuation directions, phase shifts and energy ratios as a function of incident direction in double-porosity thermoelasticity medium.

This paper presents a new approach for estimating the discretization error of finite element analysis of generalized eigenproblems. The method uses smoothed gradients at nodal points to derive improved element‐by‐element interpolation functions. The improved interpolation functions and their gradients are used in the Rayleigh quotient to obtain an improved eigenvalue. The improved eigenvalue is used to estimate the error of the original solution. The proposed method does not require any re‐solution of the eigenproblem. Results for 1‐D and 2‐D C° eigenproblems in acoustics and elastic vibrations are used as examples to demonstrate the accuracy of the proposed method.

Invasive transit-time ultrasonic flow measurement involves the use of ultrasonic transducers, which sense the flowing fluid and are the most important parts of an ultrasonic flowmeter. In this study, two ultrasonic transducers were designed, numerically simulated and fabricated to be used in an ultrasonic gas flowmeter.

PZT-5H piezoceramic elements with specific dimensions were designed and used as beating heart inside the transducers. Different methods, including impedance-frequency analysis, optical emission spectroscopy and performance tests in pressurized chambers were used to evaluate the piezoelectric elements, ultrasonic transducer housings and the fabricated transducers, respectively. In addition, finite element method results showed its ability for design stages of ultrasonic transducer.

Experimental results for transit time difference (TTD) and the normalized received voltage were compared with simulation results at the same conditions. There was a quite good agreement between the two method results. Extensive simulation results showed that under the considered range of environmental conditions, the change of acoustic path length has the most impact on TTD, with respect to temperature and pressure. A change of 1 mm in acoustic path length leads to 0.74 per cent change in TTD, approximately. In addition, for normalized received voltage, 1 bar change in pressure has the most impact and its value is as high as 3.76 per cent.

This method is possibly used in ultrasonic gas flowmeter fabrication.

In this work, design, fabrication, experimental tests and numerical simulation of ultrasonic transducers are presented.

Presents the scientific methodology from the enlarged cybernetical perspective that recognizes the anisotropy of time, the probabilistic character of natural laws, and the entry that the incomplete determinism in Nature opens to the occurrence of innovation, growth, organization, teleology communication, control, contest and freedom. The new tier to the methodological edifice that cybernetics provides stands on the earlier tiers, which go back to the Ionians (c. 500 BC). However, the new insights reveal flaws in the earlier tiers, and their removal strengthens the entire edifice. The new concepts of teleological activity and contest allow the clear demarcation of the military sciences as those whose subject matter is teleological activity involving contest. The paramount question “what ought to be done”, outside the empirical realm, is embraced by the scientific methodology. It also embraces the cognitive sciences that ask how the human mind is able to discover, and how the sequence of discoveries might converge to a true description of reality.

The propagation of free vibrations in microstretch thermoelastic homogeneous isotropic, thermally conducting plate bordered with layers of inviscid liquid on both sides subjected to stress free thermally insulated and isothermal conditions is investigated in the context of Lord and Shulman (L‐S) and Green and Lindsay (G‐L) theories of thermoelasticity. The secular equations for symmetric and skewsymmetric wave mode propagation are derived. The regions of secular equations are obtained and short wavelength waves of the secular equations are also discussed. At short wavelength limits, the secular equations reduce to Rayleigh surface wave frequency equations. Finally, the numerical solution is carried out for magnesium crystal composite material plate bordered with water. The dispersion curves for symmetric and skew‐symmetric wave modes are computed numerically and presented graphically.