Добірка наукової літератури з теми "High frequency ultra-sound"

The auditory ossicles—malleus, incus and stapes—are the smallest bones in mammalian bodies and enable stable sound transmission to the inner ear. Sperm whales are one of the deepest diving aquatic mammals that produce and perceive sounds with extreme loudness greater than 180 dB and frequencies higher than 30 kHz. Therefore, it is of major interest to decipher the microstructural basis for these unparalleled hearing abilities. Using a suite of high-resolution imaging techniques, we reveal that auditory ossicles of sperm whales are highly functional, featuring an ultra-high matrix mineralization that is higher than their teeth. On a micro-morphological and cellular level, this was associated with osteonal structures and osteocyte lacunar occlusions through calcified nanospherites (i.e. micropetrosis), while the bones were characterized by a higher hardness compared to a vertebral bone of the same animals as well as to human auditory ossicles. We propose that the ultra-high mineralization facilitates the unique hearing ability of sperm whales. High matrix mineralization represents an evolutionary conserved or convergent adaptation to middle ear sound transmission.

The 22.2 multichannel sound system has been developed for an ultra high-definition television system. This system consists of twenty two loudspeakers and two sub-woofers called low frequency effects, and can reproduce three-dimensional sound image appropriate to the ultra high-definition television system. However, this system has a problem of high cost to install. On the other hand, the multichannel sound system with horizontal-arranged loudspeakers has lower cost to install than full scale one. However, this system cannot reproduce an upper sound image. Therefore, in this paper, we propose the upper sound image control with horizontal-arranged loudspeakers based on the parametric head-related transfer functions. The proposed method generates binaural signals to control the sound image elevationally based on the parametric head-related transfer functions in the median plane. Also, the proposed system uses the interaural level difference to control the sound image of binaural signals azimuthally. Finally, the proposed method generates output signals for horizontal-arranged loudspeakers from binaural signals by designing a multichannel inverse system based on multi-input / output inverse theorem. The experimental results show that the proposed method can control the sound image to elevation angle with the same accuracy as binaural lreproduction. The 22.2 multichannel sound system has been developed for an ultra high-definition television system. This system consists of twenty loudspeakers and two sub-woofers called low frequency effects, and can reproduce three-dimensional sound image appropriate to the ultra high-definition television system. However, this system has a problem of high cost to install. On the other hand, the multichannel sound system with horizontal-arranged loudspeakers has lower cost to install than full scale one. However, this system cannot reproduce an upper sound image. Therefore, in this paper, we propose the upper sound image control with horizontal-arranged loudspeakers based on the parametric head-related transfer functions. The proposed method generates binaural signals to control the sound image elevationally based on the parametric head-related transfer functions in the median plane. Also, the proposed system uses the interaural level difference to control the sound image of binaural signals azimuthally. Finally, the proposed method generates output signals for horizontal-arranged loudspeakers from binaural signals by designing a multichannel inverse system based on multi-input / output inverse theorem. The experimental results show that the proposed method can control the sound image to elevation angle with the same accuracy as binaural reproduction.

Recently, polyurethane materials are commonly used as engine room sound-absorbing materials to reduce the weight of automobiles. Polyurethane materials have excellent sound absorption performance in the 800~2,000 Hz frequency range due to the structural characteristics of the material, but the sound absorption performance of more than 2,000 Hz is insufficient. In the case of electric vehicles, it is important to improve the high frequency noise generated by the motor, and the need for modification of polyurethane materials has increased. High frequency performance can be improved by improving the air permeability of polyurethane cells through the bonding structure of polyurethane materials, optimization of blowing and gelling reactivity, and the amount of foaming gas. Increased air permeability of polyurethane materials reduces density and strength. In this study, Nano-cellulose is a highly functional new material with light and high mechanical properties through a chain bundle structure. The dispersibility is improved by optimizing the content and particle size of nano-cellulose. The goal is to develop ultra-low-density polyurethane with excellent sound absorption performance in high frequency areas over 2,000 Hz and improved strength. The strength of hood insulation and dash outer products can be improved by applying the developed polyurethane material. In addition, the quality of lightweight engine room sound absorbing materials for electric vehicles can be improved.

By exploring the mapping relationship between the multi-directional data and fault characteristics of bearings, a time-frequency analysis method for considering the multi-directional acoustic emission (AE) data of bearings is proposed. Firstly, using the full vector spectrum (FVS) theory, the full vector sound spectrogram of the dual-channel AE signal of a bearing is extracted to enhance the representation of the fault state using time-frequency characteristics. Then, the obtained full vector sound spectrogram is transformed into a specific size as the input feature map and a convolutional neural network (CNN) classifier model is established. Next, the Softmax classifier is used to classify the bearing faults in order to realise the intelligent fault diagnosis of an ultra-low-speed rolling bearing. The comparison of the different models shows that the average recognition accuracy using the full vector sound spectrogram CNN model can reach 95.61%, which is better than the other three methods. The feature extraction using the full vector sound spectrogram feature analysis method has a high degree of recognition for bearing faults in an ultra-low-speed state and can provide high accuracy and stability under noisy conditions.

Fiber-distributed optical fiber acoustic sensor (DAS) is generally used in distributed long-distance acoustic/vibration measurement. Recently, DAS is also used in weak airborne sound detection. To improve the sensitivity of DAS, using a state-of-the-art acoustic transducer or a special enhanced scattering fiber, which are uncommon in the industrial site, is often essential, according to the previous research. In this work, the fading of DAS is suppressed by the multi-frequency probes and polarization-diversity-receiver scheme. The self-noise of DAS is further lowered by the phase averaging of multiple acoustic channels wound on the transducer. We found that, supported by this high-performance DAS, even if the transducer is made with an ultra-simple plastic structure in daily life, the system can achieve high-sensitivity airborne sound sensing. The proposed simple acoustic transducer can reach the sensitivity level of −106.5 dB re. 1 rad/μPa at a sensing range of 5.1 km, which can meet many demands on the industrial site.

La biomasse fait partie des ressources renouvelables qui peuvent répondre durablement à nos besoins de production de carburants, de produits chimiques et de matériaux. En effet, la biomasse non comestible telle que la lignocellulose a attiré l'attention des chercheurs et des scientifiques au cours des dernières décennies en tant qu'alternative renouvelable. Le furfural et le 5-hydroxyméthylfurfural (HMF), dérivés de la déshydratation des pentoses et des hexoses respectivement, sont produits à plusieurs millions de tonnes par an. Ces derniers composés sont donc des molécules plateformes et représentent un intérêt majeur dans le cadre du développement durable. Ce travail vise à explorer des méthodes nouvelles et vertes pour l'oxydation sélective du furfural et de HMF afin de produire des produits biosourcés à haute valeur ajoutée tels que le 2,5-diformylfurane (DFF), l'acide maléique et l'acide succinique. Tout d'abord, un système alternatif d'oxydation de HMF a été présenté, sans l'utilisation de catalyseurs de métaux nobles, de hautes pressions et évitant la production de déchets toxiques. Dans ce contexte, l'oxydation à l'échelle du gramme de HMF conduit à la formation de DFF. Cette réaction a été catalysée par l'acide 2-iodobenzènesulfonique en présence d'Oxone®. Dans des conditions expérimentales optimisées, la conversion du HMF s'est avérée être de 100%, tandis que le rendement et la sélectivité du DFF étaient vers 90%. Par la suite, nous avons démontré un processus sans catalyseur pour la synthèse à l'échelle du gramme de l'acide maléique à partir de furfural en utilisant des irradiations ultrasonores à hautes fréquences. Une sélectivité de 70% en acide maléique avec 92% de conversion du furfural a été obtenue sans aucun catalyseur dans des conditions douces en utilisant H2O2 comme oxydant. Notre approche alternative permet l'utilisation de la biomasse au lieu du pétrole pour synthétiser l'acide maléique à partir du furfural dans un processus écologique et économe en énergie. Enfin, un nouveau procédé catalytique est développé en utilisant des nanoparticules de magnétite, comme catalyseur métallique bon marché et non noble, et du peroxyde d'hydrogène pour l'oxydation du furfural en acide succinique. La conversion totale du furfural a été obtenue avec 67% de rendement en acide succinique dans des conditions douces
Biomass is one of the renewable and green resources that can sustainably meet our needs for the production of fuels, chemicals and materials. Indeed, nonedible biomass such as lignocellulose has attracted attention of researchers and scientists in the last decades as a renewable alternative. Furfural and 5-hydroxymethylfurfural (HMF), derived from the dehydration of pentoses and hexoses respectively, are produced in multimillion ton-scale annually. The latter compounds are, therefore, platform molecules and represent a major interest in the context of sustainable development. This work aims to explore novel and green methods for the selective oxidation of furfural and HMF to produce high value-added bio-sourced products such as, 2,5-diformylfuran (DFF), maleic acid and succinic acid. First, an alternative system of HMF oxidation was presented, without the use of noble metal catalysts, high pressures and avoiding the production of toxic wastes. In this context, the gram-scale oxidation HMF leads to the formation of DFF. This reaction was catalyzed by 2-iodobenzenesulfonic acid in the presence of Oxone®. Under optimized experimental conditions, the HMF conversion was found to be 100%, while the DFF yield and selectivity were almost 90%. Subsequently, we demonstrated a catalyst-free process for the gram-scale synthesis of maleic acid from furfural using high frequency ultrasound irradiations. A 70% selectivity of maleic acid with 92% of furfural conversion were achieved without any catalyst under mild conditions using H2O2 as oxidant. Our alternative approach enables the use of biomass instead of petroleum to synthesize maleic acid from furfural in an eco-friendly and energy-efficient process. At last, a novel catalytic process is developed using magnetite nanoparticles, as a cheap and non-noble metal catalyst, and hydrogen peroxide for the oxidation of furfural into succinic acid. Total conversion of furfural was achieved with 67% of succinic acid yield under mild conditions

At the end of the last century, a dictionary could confidently define broadcasting as the transmission of a signal for television or radio. Within a decade, every element of that definition had changed. Transmission had branched out from the cumbersome business of placing masts bearing receivers and transmitters at the highest vantage points across the countryside. A signal was no longer confined to the band waves that the air could carry — invisible streams snaking their way across the landscape: Ultra High Frequency (UHF) carrying television, as long as the hills weren’t in the way; Very High Frequency (VHF or FM)carrying wonderful quality sound, as long as the same hills were not joined by chimneys, bodies, the wrong sort of cloud or stonework; Long Wave, unstoppable by anything except distance, it seemed,carrying cricket and the shipping forecast across Europe and far out to sea; Medium Wave(AM), the carrier of choice for hosts of daytime local music stations and great for listening in the car, but hopeless when night fell and the waves went bouncing around the ionosphere bringing martial music from Albania where the football commentary should have been; and Short Wave — the touchiest of the wave bands, that made catching the words as hard as catching fish, but finally gave national broadcasters a global reach.

In this study, we have demonstrated a particle separation device taking advantage of the ultra-high frequency sound waves. The sound waves, in the form of surface acoustic waves, are produced by an acoustofluidic platform build on top of a piezoelectric substrate bonded to a microfluidic channel. The particles’ mixture, pumped through the microchannel, is focused using a sheath fluid. A travelling surface acoustic wave (TSAW), propagating normal to the flow, interacts with the particles and deflect them from their original path to induce size-based separation in a continuous flow. We initially started the experiment with 40 MHz TSAWs for deflecting 10 μm diameter polystyrene particles but failed. However, larger diameter particles (∼ 30 μm) were successfully deflected from their streamlines and separated from the smaller particles (∼ 10 μm) using TSAWs with 40 MHz frequency. The separation of smaller diameter particles (3, 5 and 7 μm) was also achieved using an order of magnitude higher-frequency (∼ 133 MHz) TSAWs.

Abstract This paper describes an ultra high speed hydraulic turbo motor utilizing a negative damping flow force. The negative damping flow force is the main cause of the self-excited oscillation of a valve. The disk which was attached to the motor shaft was rotated with different loads which were determined by “ Eddy current method”. Rotational speed of the disk was measured by a non-contact revolution counter, and frequency characteristics of the sound pressure level were measured by a sound pressure level meter. We found that this ultra high speed improved hydraulic turbo motor had a 5 % higher rotational speed than the conventional one and it achieved 40,000 rpm under no load, 10 MPa, and 60 degree in C conditions. An theoretical analysis was conducted to explain these experimental results.

Measuring infrasonic sound sets high requirements on the instruments used. Typically the measurement chain consists of a microphone and a preamplifier. As the input resistance of the preamplifier forms a high pass filter with the capacitance of the microphone in the picofarad range, measuring ultra low frequencies becomes a challenge. The electric preamplifier presented in this paper together with a prepolarized condenser microphone form a measurement system. The developed preamplifier connects the microphone signal directly to the input of an operational amplifier with ultra high input impedance. The bias current for the preamplifier further complicates the signal amplification. A configuration of two diode-connected FETs provide the input bias current. The resulting input impedance of nearly 1 TΩ yields a total lower limiting −3 dB cutoff frequency of 8 mHz and a dynamic range of 95 dB. Being able to measure down to ultra low frequencies in the infrasonic frequency range will aid actors in the debate on wind turbine noise. Sonic booms from supersonic flights include frequencies down to 10 mHz and the preamplifier proposed in this paper will aid scientists trying to modify the N-shaped shock wave at high level which prohibits flights in land zones.