Hasil untuk "Acoustics. Sound"

Paul J. Gendron, Kenneth T. Bowers

A Bayes factor discriminant is constructed for active sonar detection of a scattering body in an underwater refractive environment about which there is some depth uncertainty. The scenarios of interest here are associated with relatively high-frequency broadband waveforms and with reception along vertical arrays. The approach properly accounts for environmental information regarding the refractive media, as well as surface and volume reverberation models or in situ observations of the same. Uncertainty, both in the reverberation field and the scatterers' depth, is incorporated through proper marginalization rather than maximization as in more conventional generalized likelihood ratio tests. Bayes factor active sonar (BFAS) yields a set of time-varying quadratic forms in beam-delay space, optimally balancing uncertainty in the object of interest with reverberation and noise subspaces in the minimum average risk sense. By utilizing waveguide information, BFAS combines multi-path arrivals, optimally attenuating reverberation subspaces while preserving the target subspace, thereby effectively increasing signal-to-reverberation plus noise ratios despite uncertainty in target depth. Depth-invariant modes are leveraged to provide a valuable expansion of the discriminating information of the BFAS, thereby providing lower bounds on the performance of the BFAS. These bounds illustrate that even under depth uncertainty, the BFAS outperforms a single specular arrival detector with perfect knowledge of the scattering body's depth. Performance across various refractive and shallow-water environments is demonstrated, lending credence to the multi-path combining approach.

Hyeonbin Oh, Jung-Hyun Nam, Bo-Ram Park et al.

This study evaluated the physical and rheological properties of whole rice flour treated for different sonication times (0–15 min). Ultrasonication reduces the particle size of rice flour and improves its solubility. Viscosity tests using RVA and steady shear showed a notable decrease in the viscosity of the rehydrated pregelatinized rice flour. Although no unusual patterns were observed in the XRD analysis, the FT-IR and microstructure morphology findings suggest that ultrasonication led to structural changes in the rice flour. Overall, the study indicates that ultrasonication is a practical and clean method for producing plant-based drinks from rice flour, which could expand its limited applications in the beverage industry.

Singh Thapa Devendra, Najah Zahraa, Khosla Vivek et al.

The development of metamaterials promises to enable smallscale, worldwide industry-wide acoustic, electromagnetic, mechanical, and solar energy harvesting. Engineered structures surpass natural material limitations, offering capabilities unattainable in traditional counterparts. This paper explores metamaterials' manipulation of acoustic, electromagnetic, mechanical, and solar energy. Mechanical metamaterials convert strain into electrical energy, applicable from interstellar travel to terrestrial infrastructure. Precision-configured acoustic metamaterials efficiently harness dispersed acoustic energy, improving renewable energy methodologies. Integration into photovoltaic cells showcases metamaterials' solar potential, with innovative designs enhancing solar energy conversion efficiency. “Metamaterials” is a word used to describe artificial structures whose properties are based on the aggregate expression of individual components. Acoustic metamaterials are the term used for such constructions intended for the manipulation of acoustic waves. Controlled wave propagation is made possible by acoustic metamaterials, which is frequently not possible with bulk materials created chemically. This indicates that the wave propagation in acoustic metamaterials is directed and produces desired acoustic effects, independent of the mass-density properties of the material. The distinct properties of acoustic metamaterials have paved the way for the creation of practical solutions for a variety of uses, such as passive destructive interference, acoustic cloaking, sound focusing, low-frequency sound insulation, and biomedical acoustics. The kind of sound modification determines the general properties of an acoustic metamaterial. The properties of several of the most promising acoustic metamaterials from passive to active are introduced in this work. In order to achieve a sustainable future, it is necessary to combine environmentally friendly technologies with renewable energy sources for their final application. This is demonstrated by highlighting both the fundamental concepts and the physical models that were assessed.

Anuj Kaushik, Bachir A. Abeid, Jonathan B. Estrada et al.

Acoustic droplet vaporization (ADV) offers a dynamic approach for generating bubbles on demand, presenting new possibilities in biomedical applications. Although ADV has been investigated in various biomedical applications, its potential in tissue characterization remains unexplored. Here, we investigated the effects of surrounding media on the radial dynamics and acoustic emissions of ADV bubbles using theoretical and experimental methodologies. For theoretical studies, bubble dynamics were combined with the Kelvin-Voigt material constitutive model, accounting for viscoelasticity of the media. The radial dynamics and acoustic emissions of the ADV-bubbles were recorded via ultra-high-speed microscopy and passive cavitation detection, respectively. Perfluoropentane phase-shift droplets were embedded in tissue-mimicking hydrogels of varying fibrin concentrations, representing different elastic moduli. Radial dynamics and the acoustic emissions, both temporal and spectral, of the ADV-bubbles depended significantly on fibrin elastic modulus. For example, an increase in fibrin elastic modulus from ≈0.2 kPa to ≈6 kPa reduced the maximum expansion radius of the ADV-bubbles by 50%. A similar increase in the elastic modulus significantly impacted both linear (e.g., fundamental) and nonlinear (e.g., subharmonic) acoustic responses of the ADV-bubbles, by up to 10 dB. The sensitivity of ADV to the surrounding media was dependent on acoustic parameters such as driving pressure and the droplets concentration. Further analysis of the acoustic emissions revealed distinct ADV signal characteristics, which were significantly influenced by the surrounding media.

Hongyue Lin, Yiyang Qian, Jia Chen et al.

In order to analyze the sound production mechanism and the acoustic characteristics of <i>Haliotis discus hannai</i> during feeding, this paper proposes a multi-source information fusion approach combining passive acoustics with videos. In the experiments, abalones with a shell length of 60 ± 2.7 mm were divided into two groups: Group A was fed with fresh macro algae <i>Gracilaria lemaneiformis</i> as food once each day; Group B was placed on a small amount of sand as impurities at the bottom of the tank. As control groups, Group C did not have abalone or food and Group D did not have abalones but food was added. The eating acoustic signals of abalone were mainly concentrated in the frequency range between 9.49 kHz and 44.36 kHz, wherein the peak frequency is 37.86 ± 2.55 kHz, with the maximum energy −66.43 ± 5.17 dBm/Hz. Each pulse sequence is with a duration of 119.12 ± 70.51 ms and consists of several sub-pulses. Nearly 70% of the pulse sequences consist of 1~2 sub-pulses and the duration of the pulse containing one sub-pulse is 42.62 ± 19.72 ms. The eating rate was kept at 0.61 ± 0.04 times/min at the beginning and was decreased significantly to 0.48 ± 0.08 times/min after 60 min. Note that the characteristic analysis of abalone acoustic signals during feeding are first reported in this manuscript to the best of our knowledge, and this paper also demonstrates that the sound of abalone is produced by scraping and grinding food with radula. Because the eating rate decreases with the reduction in the abalone’s level of hunger, the results may be used as an acoustic indicator of feeding strategy for the abalone aquaculture industry.

Islam M Elbaz, MA Sohaly, H El-Metwally

In this paper, we study a stochastic SIS epidemic model with distributed delays. The positiveness of the solutions is established. We obtain sufficient conditions for the extinction of the disease through the study of stochastic stability of the disease-free equilibrium and stability of the same equilibrium in the mean. Compared to many works on the deterministic and stochastic SIS models and their stability, the distributed delays involved in the model offer new conditions with much more boundedness on the rate of losing immunity. The disease is extinct for small and large enough values of the intensity of noise and regardless of the initial history functions and the magnitude of the basic reproductive number R 0 .

Linyu Ni, Wei-kuan Lin, Amy Kasputis et al.

In our previous studies, we demonstrated the ability of an interstitial all-optical needle photoacoustic (PA) sensing probe and PA spectral analysis (PASA) to assess the aggressiveness of prostate cancer. In this clinical translation investigation, we integrated the optical components of the needle PA sensing probe into a 18G steel needle. The translational needle PA sensing probe was evaluated using intact human prostates in a simulated ultrasound-guided transperineal prostate biopsy. PA signals were acquired at 1220 nm, 1370 nm, 800 nm and 266 nm at each interstitial measurement location and quantified by PASA within the frequency range of 8–28 MHz. The measurement locations were stained for establishing spatial correlations between the quantitative measurements and the histological diagnosing. Most of the quantitative PA assessments reveal statistically significant differences between the benign and cancerous regions. Multivariate analysis combining the PASA quantifications shows an accuracy close to 90% in differentiating the benign and cancerous regions in the prostates.

Xin Xu, Lei Zhang, Yabin Feng et al.

Vacuum freeze-drying is a new and high technology on agricultural product dehydrating dry, but it faces the high cost problem caused by high energy consumption. This study investigated the effect of ultrasound (US), freeze-thawing (including the freeze-air thawing (AT), freeze-water thawing (WT), freeze-ultrasound thawing (UST), and freeze-air ultrasound thawing (AT + US)) pretreatments on the vacuum freeze-drying efficiency and the quality of dried okra. The results indicated that the application of ultrasound and different freeze-thawing pretreatments reduced the drying time by 25.0%–62.50% and the total energy consumption was 24.28%–62.35% less. The AT pretreatment reduced the time by of okra slices by 62.50% and the total energy consumption was 62.35% less. The significant decrease in drying time was due to a change in the microstructure caused by pretreatment. Besides, the okra pretreated with the US retained most of the quality characteristics (flavor, color, hardness, and frangibility) among all methods, while, AT + US had the most changeable characteristics in quality, which is deprecated in our study. The okra pretreated with the US and AT, separately, had the best dry matter content loss (9.008%, 5.602%), lower chlorophyll degradation (5.05%, 5.44% less), and higher contents of total phenolics, total flavonoids, and pectin, with strong antioxidant capacity, compared to other methods. The pretreatments did not have a large effect on the functional groups and the structure of pectin, but slightly affected the viscosity. It can be concluded that AT and US pretreatment methods are better than others.

L. Astráin-Redín, J. Abad, A. Rieder et al.

Nowadays, rapid freezing is sought to favor the formation of small ice crystals. Several studies have shown that the application of ultrasounds (US) accelerates the processes of energy and mass transfer when they are applied through immersion systems. However, there are hardly any studies on its application in direct systems without the use of a liquid medium for its transmission. Therefore, the objective of this work was to evaluate the potential of the application of US for improving the freezing process of chicken breast samples. First, the application of intermittent US treatments at different net sonication times of 7, 17, 37, 50 and 67% during the freezing of distilled water samples in a conventional freezer was evaluated. It was observed that net sonication times of 37, 50 and 67% reduced the phase change period by 30.0, 21.4, 27.0%, respectively. The effective freezing time was also reduced by 12.4 and 12.8% by applying net sonication times of 37 and 50%. Considering these results, an intermittent US treatment with a net sonication time of 37% was chosen for chicken breast freezing in an air-forced cooling tunnel at ambient temperatures from −13 to −22 °C. The length of all the freezing phases was reduced upon application of US, leading to an overall process time reduction of approx. 11%. On the other hand, no significant differences were found either in the Water Holding Capacity (WHC) or Cooking Loss (CL) values between control and US assisted frozen chicken breast samples. Furthermore, in vitro experiments showed that US-assisted freezing did not influence protein digestibility of chicken meat samples.This study demonstrates the potential of the application of US by direct contact to favor energy transfer processes during freezing of water and chicken breasts samples. However, its effect on the quality of the frozen products should be further studied.

Moorthy Maruthapandi, Arumugam Saravanan, Shanmugasundaram Manoj et al.

Polypyrrole (PPY) spherical particles synthesized using carbon dots as an efficient catalyst were strongly embedded on fluorinated nonwoven fabric by ultrasonication to form a membrane with high hydrophilicity. An optimal amount of PPY adhered to the membrane after 30 min of sonication enhanced the overall membrane area with high hydrophilicity. Oil with high hydrophobicity was repelled by the resulting membrane, whereas water was freely penetrated and diffused from the membrane. The membrane exhibited good reusability and efficiency for the recovery of oil from a cooking oil–water mixture within 30 s. The incorporation of PPY in the fluorinated fabric imparts significant antibacterial properties against two common pathogens, Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The anti-biofouling membrane could pave the way for its potential application to separate spilled oil from contaminated waters, comprising different microorganisms and living species. The novelty of this manuscript is described in a new system, the fabrication of PPY membranes with two important properties: biocidal and oil/water separation.

Rongkang Gao, Zhiqiang Xu, Yaguang Ren et al.

Many nonlinear effects have been discovered and developed in photoacoustic imaging. These nonlinear mechanisms have been explored for different utilizations, such as enhancing imaging contrast, measuring tissue temperature, achieving super-resolution imaging, enabling functional imaging, and extracting important physical parameters. This review aims to introduce different nonlinear mechanisms in photoacoustics, underline the fundamental principles, highlight their representative applications, and outline the occurrence conditions and applicable range of each nonlinear mechanism. Furthermore, this review thoroughly discusses the nonlinearity rule concerning how the mathematical structure of the nonlinear dependence is correlated to its practical applications. This summarization is useful for identifying and guiding the potential applications of nonlinearity based on their mathematical expressions, and is helpful for new nonlinear mechanism discovery or implementation in the future, which facilitates further breakthroughs in nonlinear photoacoustics.

Zhixia Wang, Wei Wang, Fengshou Gu et al.

Global orbits connect the saddle points in an infinite period through the homoclinic and heteroclinic types of manifolds. Different from the periodic movement analysis, it requires special strategies to obtain expression of the orbit and detect the associated profound dynamic behaviors, such as chaos. In this paper, a global dynamic frequency method is applied to detect the homoclinic and heteroclinic bifurcation of the complicated nonlinear systems. The so-called dynamic frequency refers to the newly introduced frequency that varies with time t , unlike the usual static variable. This new method obtains the critical bifurcation value as well as the analytic expression of the orbit by using a standard five-step hyperbolic function-balancing procedure, which represents the influence of the higher harmonic terms on the global orbit and leads to a significant reduction of calculation workload. Moreover, a new homoclinic manifold analysis maps the periodic excitation onto the target global manifold that transfers the chaos discussion of non-autonomous systems into the orbit computation of the general autonomous system. That strategy unifies the global bifurcation analysis into a standard orbit approximation procedure. The numerical simulation results are shown to compare with the predictions.

Denis Sergeevich RAKOV, Aleksandr S. RAKOV, Andrey N. KUDRYAVTSEV et al.

The paper presents results of numerical calculations and experimental data on the directional pattern of two 38-element parametric arrays composed of ultrasound sources. Two types of antenna arrays are considered, namely with parallel and coaxial connections of ultrasonic transducers (elements). The results of selecting and functional testing of unit elements are described in this paper. It is found that in the coaxial element connection of the antenna array, the level of side lobes is higher than that in the parallel element connection.

M. URBAŃCZYK

The paper suggests a way of analysis of the operation of the SAW oscillator basing on a computer simulation programme of the electronic systems of the SPICE type. In compliance with the requirements of this programme, an equivalent diagram of a surface wave filter has been presented in a form convenient for computer analysis.

Tadeusz Wszołek

Accordingly to the regulations contained in the European Noise Directive (END) and also in some legal acts being currently under legislative process in Poland, in the nearest future the $L_{\textrm{DEN}}$ and $L_{\textrm{N}}$ levels will be used as the basis for evaluation of corona noise from UHV power lines. The paper presents an example of combined uncertainty evaluation for estimation of long-term level ($L_{\textrm{A, LT}}$) and $L_{\textrm{DEN}}$ level for corona noise from UHV overhead power lines. Some specific features of that noise – large time variation of its level and spectral structure, dependent on the atmospheric conditions, and on the other hand often small distance from the background noise – are the reason that the evaluation of its estimation uncertainty is more difficult then for some other, better “determined” noise sources. The partial uncertainties related to the measurement system and prediction method according to the reference methods for industry noise were dealt with. The effect of the environment on the system and the measured quantity have been distinguished and quantitatively determined.

Wiesław WSZOŁEK

In this work, parts of the research concerning a new concept of applying computer technique in pathological speech analysis have been presented. This new concept assumes that during the pathological speech analysis we are not aiming neither at the establishing of such or other signal parameters nor at the trying to classify them, but we tend to understand automatically the causes of deformation, which can be observed in the considered signal. Therefore the concept presented postulates the replacing the well known process of the pathological speech acoustic signal recognition by a more advanced method of analysis, which means a confrontation of the features, which are revealed in the signal during its transformation with features that could be expected basing on the knowledge gathered in the system concerning pathological factors deforming the true form of the signal. In the meaning of the term "automated understanding", this denotes a signal analysis of a deformed speech, which is oriented towards revealing the sources of the observed signal distortions, and not towards bare analysis of their patterns and diagnostic deduction based on their typology. In the work the basic elements of the proposed method are presented. Examples showing its essence were derived basing on the selected larynx pathology analysis.

Long WEI, Min LI, Qiang FU et al.

In the acoustic fatigue experiment for hypersonic vehicle in simulated harsh service environment on ground, acoustic loads on the surface of test pieces of the vehicle need to be measured. However, for the normal microphones without high temperature resistance ability, the near field sound measurement cannot be achieved. On the basis of previous researches, in this work, an acoustic tubes array is designed to achieve the near field measurement of acoustic loads on the surface of the test piece in the supersonic airflow with high temperature made by coherent jet oxygen lance. In this work, the process of designing this acoustic tubes array is firstly introduced. Then the equivalence between phase differences of microphones mounted at exit of tubes and those at entrances of tubes are proved, which ensure the reasonability of substituting the phase differences of signals acquired by microphones directly into beamforming algorithm to acquire the distribution and intensity of the acoustic load source. Finally, with this designed acoustic tubes array, a measurement of acoustic loads on the surface of the test piece in the supersonic airflow made by coherent jet oxygen lance is conducted, and the measurement result is analyzed.

Monika DUKAT, Aldona ZARYCKA

A technological process to obtain ceramic materials by the sol-gel method replaces gradually conventional methods, based on a simple oxide synthesis as a result of high temperature sintering. The materials obtained by the sol-gel method are characterized by high density and better chemical purity. A powder with the Pb(Zr0:52Ti0:48)O3 chemical composition was obtained as a result of a synthesis by the sol-gel method and it was formed and sintered by a hot pressing method (HP). The specimens obtained were subjected to examinations of the dielectric properties, the tangent of dielectric loss angle, the piezoelectric properties and their micro-photographs were taken (SEM). A course of the technological process by the sol-gel method was described, the dielectric and piezoelectric parameters were determined and a microstructure and a domain structure were examined in the work.

Vytautas J. Stauskis

Investigations of acoustics of halls of different types and volumes have disclosed good or acceptable values of the music sound clarity index C80, while the reverberation times of these halls were found to be either very short or very long. Subjectively, the acoustics of these halls are considered to be unsatisfactory. For example, the reverberation time measured in the hall of the Vilnius Opera and Ballet Theatre is about 1 s, while the values of the C"n index are either good or acceptable. A church the volume of which is 22 650 m3 has acceptable C80 values both in the performers's places and in the front rows. Similar results were obtained in other halls too. First Published Online: 14 Oct 2010