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Background Metaconcrete is a new concept of concrete, showing marked attenuation properties under impact and blast loading, where traditional aggregates are partially replaced by resonant bi-material inclusions. In a departure from conventional mechanical metamaterials, the inclusions are dispersed randomly as cast in the material. The behavior of metaconcrete at supersonic frequencies has been investigated theoretically and numerically and confirmed experimentally. Objective The feasibility of metaconcrete to achieve wave attenuation at low frequencies demands further experimental validation. The present study is directed at characterizing dynamically, in the range of the low sonic frequencies, the—possibly synergistic—effect of combinations of different types of inclusions on the attenuation properties of metaconcrete. Methods Dynamic tests are conducted on cylindrical metaconcrete specimens cast with two types of spherical inclusions, made of a steel core and a polymeric coating. The two inclusions differ in terms of size and coating material: type 1 inclusions are 22 mm diameter with 1.35 mm PDMS coating; type 2 inclusions are 24 mm diameter with 2 mm layer natural rubber coating. Linear frequency sweeps in the low sonic range (< 10 kHz), tuned to numerically estimated inclusion eigenfrequencies, are applied to the specimens through a mechanical actuator. The transmitted waves are recorded by transducers and Fast-Fourier transformed (FFT) to bring the attenuation spectrum of the material into full display. Results Amplitude reductions of transmitted signals are markedly visible for any metaconcrete specimens in the range of the inclusion resonant frequencies, namely, 3,400-3,500 Hz for the PDMS coating inclusions and near 3,200 Hz for the natural rubber coating inclusions. Specimens with mixed inclusions provide a rather uniform attenuation in a limited range of frequencies, independently of the inclusion density, while specimens with a single inclusion type are effective over larger frequency ranges. With respect to conventional concrete, metaconcrete reduces up to 90% the amplitude of the transmitted signal within the attenuation bands. Conclusions Relative to conventional concrete, metaconcrete strongly attenuates waves over frequency bands determined by the resonant frequencies of the inclusions. The present dynamical tests conducted in the sonic range of frequencies quantify the attenuation properties of the metaconcrete cast with two types inclusions, providing location, range and intensity of the attenuation bands, which are dependent on the physical-geometric features of the inclusions.

This paper presents the characterization of the modal frequencies and the modal orientation of the axisymmetric resonators in Coriolis vibratory gyroscopes based on the approaches of the frequency sweep and the ring down. The modal frequencies and the orientation of the stiffness axis are the key parameters for the mechanical correction of the stiffness imperfections. The frequency sweep method utilizes the zero and the poles in the magnitude-frequency responses of the two-dimensional transfer function to extract the modal orientation information within the frequency domain. The ring down method makes use of the peak and the valley values of the beat signals at the readout electrodes to obtain the modal orientation and the coefficient of the nonlinear stiffness directly within the time domain. The proposed approaches were verified via a silicon ring resonator designed for gyroscopic sensing and the modal information from the experiments exhibited a good agreement between the methods of the frequency sweep and the ring down.

The objective of the study was to investigate and demonstrate the application of frequency-sweep dynamic acoustic fields for size-selective particle filtration on centimeter scale in a regulated continuous flow. The 3D-printed prototype of the acoustic separator has two inlets and two outlets, whereas the dynamic acoustic field is generated between a transducer, operating in the MHz range, and a reflector. The measured frequency response of the prototype was input to computer models, and simulations were carried out to explore the effects of the sweep period and the flow parameters on the filtration performance. A design-of-experiments study showed that the filtration performance is largely affected by the sweep period and the outlet flow rate. Lab experiments with model particle mixtures demonstrated the size selective filtration performance of the prototype with a total flow rate of 1 L h - 1 . A mixture with unknown properties was also used to demonstrate the selective filtration performance of the prototype.

Chinese lexical tones determine word meaning and are crucial in reading development. Reduced tone awareness is widely reported in children with reading difficulties (RD). Lexical-tone processing requires sensitivity to frequency-modulated sound changes. The present study investigates whether reduced tone awareness in children with RD is reflected in basic auditory processing and the level at which the breakdown occurs. Magnetoencephalographic techniques and an oddball paradigm were used to elicit auditory-related neural responses. Five frequency sweep conditions were established to mirror the frequency fluctuation in Chinese lexical tones, including one standard (level) sweep and four deviant sweeps (fast-up, fast-down, slow-up, and slow-down). A total of 14 Chinese-speaking children aged 9-12 years with RD and 13 age-matched typically developing children were recruited. The participants completed a magnetoencephalographic data acquisition session, during which they watched a silent cartoon and the auditory stimuli were presented in a pseudorandomized order. The results revealed that the significant between-group difference was caused by differences in the level of auditory sensory processing, reflected by the P1m component elicited by the slow-up frequency sweep. This finding indicated that auditory sensory processing was affected by both the duration and the direction of a frequency sweep. Sensitivity to changes in duration and frequency is crucial for the processing of suprasegmental features. Therefore, this sensory deficit might be associated with difficulties discriminating two tones with an upward frequency contour in Chinese.

The ability to rapidly encode the direction of frequency contour contained in frequency-modulated (FM) sweeps is essential for speech processing, music appreciation, and conspecific communications. Psychophysical evidence points to a common temporal window threshold for human listeners in processing rapid changes in frequency glides. No neural evidence has been provided for the existence of a cortical temporal window threshold underlying the encoding of rapid transitions in frequency glides. The present magnetoencephalography study used the cortical mismatch negativity activity (MMNm) to investigate the minimum temporal window required for detecting different magnitudes of directional changes in frequency-modulated sweeps. A deviant oddball paradigm was used in which directional upward or downward frequency sweep serves as the standard and the same type of sweep with the opposite direction serves as its deviant. Stimuli consisted of unidirectional linear frequency-sweep complexes that swept across speech-relevant frequency bands in durations of 10, 20, 40, 80, 160, and 320 ms (with corresponding rates of 50, 25, 12.5, 6.2, 3.1, 1.5 oct/s). The data revealed significant magnetic mismatch field responses across all sweep durations, with slower-rate sweeps eliciting larger MMNm responses. A greater temporally related enhancement in MMNm response was obtained for rising but not falling frequency sweep contours. A hemispheric asymmetry in the MMNm response pattern was observed corresponding to the directionality of frequency sweeps. Contrary to psychophysical findings, we report a temporal window as short as 10 ms sufficient to elicit a robust MMNm response to a directional change in speech-relevant frequency contours. The results suggest that auditory cortex requires extremely brief temporal window to implicitly differentiate a dynamic change in frequency of linguistically relevant pitch contours. That the brain is extremely sensitive to fine spectral changes contained in speech-relevant glides provides cortical evidence for the ecological importance of FM sweeps in speech processing.

In this paper, we realize a series of 2-GHz wide rectangular optical filters based on the stimulated Brillouin scattering (SBS) effect in optical fiber with a frequency-swept pump and gain feedback compensation scheme. The frequency sweep pump period is a key parameter to achieve acceptable signal performance in the frequency-swept pump based SBS gain filter. We evaluate the system performance of the signal, which is fed into the SBS filter based on frequency-swept pump with different sweep periods ranging from 0.1 to 100 μs, in terms of eye diagrams and bit-error rate (BER) after 12.5 and 25 km of fiber transmission, respectively. Both 500-Mb/s and 1-Gb/s on-off-keying (OOK) signals are used for real-time signal quality evaluation. The optimum eye diagram and BER performance are achieved after 25 km transmission under a 1 μs frequency sweep pump period, as well as after 12.5-km transmission under a 0.5 μs sweep period. The experimental results show that the optimal frequency sweep pump period is always around 1/120 of the signal propagation time in the fiber for different transmission length, providing a guideline on the design of the frequency-swept pump based SBS gain filter and its applications.

Heating energy represents a significant proportion of the total energy consumption of theFederal Republic of Germany. Thus, a reduction of heating energy demand in buildings is one of the central points of German energy saving and climate goals. Considering that the current rate of new building construction is approximately 1 %, the most significant energy saving potential lies in existing buildings. The analysis of existing buildings will thus become more important in the years to come. As a result, the development of new measurement systems to assess the need for renovation is required. In this context, detailed Information about heat insulation and airtightness is essential. The current approaches to detect air leakage in building envelopes are mostly time consuming and expensive. Therefore, the development of an advanced and more inexpensive method is a vital step. In this paper, we2 present a study about the feasibility and suitability of ultrasound technology to evaluate the size of air leakages in building envelopes. The advantage of ultrasound technology is that the corresponding wavelengths are small enough to penetrate small openings and that disturbing background noise is usually low. Moreover, the frequencies are above the human threshold of hearing; hence, working and living inside the building would be affected less by the measurement than by a blower door test or leakage detection with audible sound. To examine the suitability of this technology, we use an experimental setup of ultrasound microphones and a speaker in a test chamber. Within this setup, we measured different hole sizes and assessed whether they could be detected using ultrasonic frequency swept signals.

We introduce a novel technique that speeds up the computation of a frequency sweep or some parametric change of material properties—assumed uniform over the entire domain—around a nominal value in electroquasi-static problem or magnetoquasi-static problem. In place of using the usual practice of solving the complex systems arising at each frequency and at each material parameter value independently, our technique requires only one factorization of a real, symmetric, and positive definite matrix. The solution at each frequency and each value of material parameter is, then, found with a few back-substitutions only. The obtained speedup is sensible and the implementation is straightforward, showing the usefulness of the proposed technique in practical applications.

The viscoelastic properties of waterlogged wood (WLW) were investigated via dynamic mechanical analysis (DMA) at room temperature and under water saturated conditions, aiming at the investigation of the relationships between viscoelasticity and chemical composition. Different softwoods (SWs) and hardwoods (HWs) from several archaeological sites were sampled, which had different levels of decay (from highly-decayed to little changed). The analytical methods included lignin and holocellulose determination by Fourier transform infrared (FTIR) spectroscopy, moisture content (MC), basic density (BD), micromorphological observations, and the DMA was performed in three-point bending and submersion mode. Both HWs and SWs showed an exponential decrease of both storage modulus (E′) and loss modulus (E″), which are related to the amount of crystalline and paracrystalline cellulose left in the cell wall, respectively. The ratio E″/E′ (tanδ) varied with the frequency in different ways depending on the preservation state of the samples. Less decayed material had a higher tanδ than the fresh reference wood and lower (or similar) tanδ in the case of highly decayed samples. Accordingly, the long-term behaviour under a certain sustained load of WLW is decay dependent.

The effect of oleuropein on the gelation properties of whole egg yolk at different pHs (2, 4.5 and 6.4) was studied. Egg yolk solutions were added with increasing amount of pure oleuropein, gelled by either thermal (pHs 4.5 and 6) or acid gelation (pH 2) and submitted to frequency sweep and stress relaxation tests. The experimental data obtained by the frequency sweep tests were modeled with a power law equation in order to get the coordination number z and the proportional coefficient A, which describe the network extension and its strength, while data obtained from stress-relaxation tests were fitted by a generalized Maxwell model with 5 elements. The addition of oleuropein affected the gelation behavior as well as the rheological properties of the gel network, and the effect was influenced by the pH of the systems. A shift of the gel point towards lower temperatures was observed in the presence of the phenolic compound, and this effect was significant in the systems at pH 4.5 (from 72.55 ± 0.07 °C to 70.43 ± 0.06 °C). According to the results obtained from the modelling of the frequency sweep test, gels at pH 6.4 and 2 were characterized by a weak network; on the contrary, at pH 4.5 the network was characterized by a low number of flow units (lower z, z = 16.52 on average) interacting with one another in a more strictly way (higher A, A = 5362 Pa s1/z on average). Such findings were successively confirmed by the stress relaxation results where it was shown that firmer gels were obtained at pH 4.5 after oleuropein enrichment.

New applications of non-destructive techniques (NDT) with ultrasonic tests (attenuation and velocity by means of ultrasonic frequency sweeps) have been developed for the characterization of fibre-reinforced cementitious composites. According to new lines of research on glass-fibre reinforced cement (GRC) matrix modification, two similar GRC composites with high percentages of fly ash and different water/binder ratios will be studied. Conventional techniques have been used to confirm their low Ca(OH)(2) content (thermogravimetry), fibre integrity (Scanning Electron Microscopy), low porosity (Mercury Intrusion Porosimetry) and good mechanical properties (compression and four points bending test). Ultrasound frequency sweeps allowed the estimation of the attenuation and pulse velocity as functions of frequency. This ultrasonic characterization was correlated successfully with conventional techniques. (C) 2015 Elsevier B.V. All rights reserved., This work has been supported by the Government of Spain under Grant TEC2011-23403 01/01/2012

In this paper the study of frequency-dependent ultrasonic attenuation in strongly heterogeneous materials is addressed. To determine the attenuation accurately over a wide frequency range, it is necessary to have suitable excitation techniques. Three kinds of transmitted signals have been analysed, grouped according to their bandwidth: narrowband and broadband signals. The mathematical formulation has revealed the relation between the distribution of energy in their spectra and their immunity to noise. Sinusoidal and burst signals have higher signal-to-noise ratios (SNRs) but need many measurements to cover their frequency range. However, linear swept-frequency signals (chirp) improve the effective bandwidth covering a wide frequency range with a single measurement and equivalent accuracy, at the expense of a lower SNR. In the case of highly attenuating materials, it is proposed to use different configurations of chirp signals, enabling injecting more energy, and therefore, improving the sensitivity of the technique without a high time cost. Thus, if the attenuation of the material and the sensitivity of the measuring equipment allows the use of broadband signals, the combination of this kind of signal and suitable signal processing results in an optimal estimate of frequency-dependent attenuation with a minimum measurement time., This work has been supported by the Spanish Administration under grant BIA2014-55311-C2-2-P.

In this paper, we adapt a novel mode-matching and method-of-moments hybrid technique to efficiently analyze substrate integrated waveguide (SIW) based devices. The hybrid technique is formulated in terms of a single equivalent current. This fact is used to include the emergent modal weights, i.e., the scattering parameters, as unknowns of the method-of-moments system of equations. In this case, it is relatively easy to develop fast frequency sweep schemes that can be used to highly accelerate the solution of an arbitrary device and, as a result, a very efficient technique is obtained. This technique can be applied to the analysis and design of SIW devices, and it is highly competitive when compared to other method-of-moments and mode-matching hybrid formulations or when compared to reference commercial software. © 2006 IEEE., This work was supported by the Ministerio de Ciencia e Innovacion, Spanish Government, under Research Project TEC2007-67630-C03-01 and by the Autonomous Government of Castilla-La Mancha under Research Project PPII10-0047-0220.