Characteristics In Frequency Range Research Articles

Amplitude-selective filtering for remote-PPG.

Biometric signatures of remote photoplethysmography (rPPG), including the pulse-induced characteristic color absorptions and pulse frequency range, have been used to design robust algorithms for extracting the pulse-signal from a video. In this paper, we look into a new biometric signature, i.e., the relative pulsatile amplitude, and use it to design a very effective yet computationally low-cost filtering method for rPPG, namely "amplitude-selective filtering" (ASF). Based on the observation that the human relative pulsatile amplitude varies in a specific lower range as a function of RGB channels, our basic idea is using the spectral amplitude of, e.g., the R-channel, to select the RGB frequency components inside the assumed pulsatile amplitude-range for pulse extraction. Similar to band-pass filtering (BPF), the proposed ASF can be applied to a broad range of rPPG algorithms to pre-process the RGB-signals before extracting the pulse. The benchmark in challenging fitness use-cases shows that applying ASF (ASF+BPF) as a pre-processing step brings significant and consistent improvements to all multi-channel pulse extraction methods. It improves different (multi-wavelength) rPPG algorithms to the extent where quality differences between the individual approaches almost disappear. The novelty of the proposed method is its simplicity and effectiveness in providing a solution for the extremely challenging application of rPPG to a fitness setting. The proposed method is easy to understand, simple to implement, and low-cost in running. It is the first time that the physiological property of pulsatile amplitude is used as a biometric signature for generic signal filtering.

Tinnitus in Normal-Hearing Participants after Exposure to Intense Low-Frequency Sound and in Ménière's Disease Patients.

Tinnitus is one of the three classical symptoms of Ménière’s disease (MD), an inner ear disease that is often accompanied by endolymphatic hydrops. Previous studies indicate that tinnitus in MD patients is dominated by low frequencies, whereas tinnitus in non-hydropic pathologies is typically higher in frequency. Tinnitus of rather low-frequency (LF) quality was also reported to occur for about 90 s in normal-hearing participants after presentation of intense, LF sound (120 dB SPL, 30 Hz, 90 s). LF sound has been demonstrated to also cause temporary endolymphatic hydrops in animal models. Here, we quantify tinnitus in two study groups with chronic (MD patients) and presumably transient endolymphatic hydrops (normal-hearing participants after LF exposure) with a psychophysical procedure. Participants matched their tinnitus either with a pure tone of adjustable frequency and level or with a noise of adjustable spectral shape and level. Sensation levels of matching stimuli were lower for MD patients (mean: 8 dB SL) than for normal-hearing participants (mean: 15 dB SL). Transient tinnitus after LF-exposure occurred in all normal-hearing participants (N = 28). About half of the normal-hearing participants matched noise to their tinnitus, the other half chose a pure tone with frequencies below 2 kHz. MD patients matched their tinnitus with either high-frequency pure tones, mainly above 3 kHz, or with a noise. Despite a significant proportion of MD patients matching low-pass (roaring) noises to their tinnitus, the range of matched stimuli was more heterogeneous than previous data suggested. We propose that in those participants with noise-like tinnitus, the percept is probably generated by increased spontaneous activity of auditory nerve fibers with a broad range of characteristic frequencies, due to an impaired ion balance in the cochlea. For tonal tinnitus, additional mechanisms are conceivable: focal hair cell loss can result in decreased auditory nerve firing and a central auditory overcompensation. Also, normal-hearing participants after LF-exposure experience alterations in spontaneous otoacoustic emissions, which may contribute to a transient tonal tinnitus.

A Robust Speaker Identification System Using the Responses from a Model of the Auditory Periphery.

Speaker identification under noisy conditions is one of the challenging topics in the field of speech processing applications. Motivated by the fact that the neural responses are robust against noise, this paper proposes a new speaker identification system using 2-D neurograms constructed from the responses of a physiologically-based computational model of the auditory periphery. The responses of auditory-nerve fibers for a wide range of characteristic frequency were simulated to speech signals to construct neurograms. The neurogram coefficients were trained using the well-known Gaussian mixture model-universal background model classification technique to generate an identity model for each speaker. In this study, three text-independent and one text-dependent speaker databases were employed to test the identification performance of the proposed method. Also, the robustness of the proposed method was investigated using speech signals distorted by three types of noise such as the white Gaussian, pink, and street noises with different signal-to-noise ratios. The identification results of the proposed neural-response-based method were compared to the performances of the traditional speaker identification methods using features such as the Mel-frequency cepstral coefficients, Gamma-tone frequency cepstral coefficients and frequency domain linear prediction. Although the classification accuracy achieved by the proposed method was comparable to the performance of those traditional techniques in quiet, the new feature was found to provide lower error rates of classification under noisy environments.

Reference-Free Assessment of Speech Intelligibility Using Bispectrum of an Auditory Neurogram.

Sensorineural hearing loss occurs due to damage to the inner and outer hair cells of the peripheral auditory system. Hearing loss can cause decreases in audibility, dynamic range, frequency and temporal resolution of the auditory system, and all of these effects are known to affect speech intelligibility. In this study, a new reference-free speech intelligibility metric is proposed using 2-D neurograms constructed from the output of a computational model of the auditory periphery. The responses of the auditory-nerve fibers with a wide range of characteristic frequencies were simulated to construct neurograms. The features of the neurograms were extracted using third-order statistics referred to as bispectrum. The phase coupling of neurogram bispectrum provides a unique insight for the presence (or deficit) of supra-threshold nonlinearities beyond audibility for listeners with normal hearing (or hearing loss). The speech intelligibility scores predicted by the proposed method were compared to the behavioral scores for listeners with normal hearing and hearing loss both in quiet and under noisy background conditions. The results were also compared to the performance of some existing methods. The predicted results showed a good fit with a small error suggesting that the subjective scores can be estimated reliably using the proposed neural-response-based metric. The proposed metric also had a wide dynamic range, and the predicted scores were well-separated as a function of hearing loss. The proposed metric successfully captures the effects of hearing loss and supra-threshold nonlinearities on speech intelligibility. This metric could be applied to evaluate the performance of various speech-processing algorithms designed for hearing aids and cochlear implants.

Development of a Dual-PIV system for high-speed flow applications

A new Dual-particle image velocimetry (Dual-PIV) system for application in supersonic flows was developed. The system was designed for shock wave/turbulent boundary layer interactions with separation. This type of flow places demanding requirements on the system, from the large range of characteristic frequencies O(100 Hz–100 kHz) to spatial and temporal resolutions necessary for the measurement of turbulent quantities (Dolling in AIAA J 39(8):1517–1531, 2001; Dupont et al. in J Fluid Mech 559:255–277, 2006; Smits and Dussauge in Turbulent shear layers in supersonic flow, 2nd edn. Springer, New York, 2006). While classic PIV systems using high-resolution CCD sensors allow high spatial resolution, these systems cannot provide the required temporal resolution. Existing high-speed PIV systems provide temporal and CMOS sensor resolutions, and even laser pulse energies, that are not adapted to our needs. The only obvious solution allowing sufficiently high spatial resolution, access to high frequencies, and a high laser pulse energy is a multi-frame system: a Dual-PIV system, consisting of two synchronized PIV systems observing the same field of view, will give access to temporal characteristics of the flow. The key technology of our system is frequency-based image separation: two lasers of different wavelengths illuminate the field of view. The cross-pollution with laser light from the respective other branches was quantified during system validation. The overall system noise was quantified, and the prevailing error of only 2 % reflects the good spatial and temporal alignment. The quality of the measurement system is demonstrated with some results on a subsonic jet flow including the spatio-temporal inter-correlation functions between the systems. First measurements in a turbulent flat-plate boundary layer at Mach 2 show the same satisfactory data quality and are also presented and discussed.

Radial profile measurements of plasma pressure-like fluctuations with the heavy ion beam diagnostic on the tokamak ISTTOK.

The Heavy Ion Beam Diagnostic (HIBD) on the tokamak ISTTOK (Instituto Superior Técnico TOKamak) has been modified, in terms of signal conditioning, to measure the local fluctuations of the neσ1,2(Te) product (plasma density times the effective ionization cross-section) along the tokamak minor diameter, in 12 sample volumes in the range of -0.7a < r < 0.7a, with a maximum delay time of 1 μs. The corresponding signals show high correlation with the magnetic Mirnov coils in the characteristic MHD frequency range of ISTTOK plasmas and enable the identification of tearing modes. This paper describes the HIBD signal conditioning system and presents a preliminary analysis of the radial profile measurements of local neσ1,2(Te) fluctuations.

Parallel pathways at the auditory periphery

We should consider the possibility that Low- and High- spontaneous rate (SR) auditory nerve fibers (ANFs) [1] constitute two different parallel pathways at the auditory periphery. The present study used a computational model of the auditory periphery [2] to demonstrate that Low- and High- SR ANFs have contrasting response properties. Anatomical studies suggest that Low- and High- SR ANF types have separate innervation sites (Figure ​(Figure1A)1A) on the same inner hair cell; lower-SR fibers synapse on the modiolar side and high-SR fibers synapse on the pillar side [3]. My hypothesis, prior to modeling the tuning curves (Figure ​(Figure1B),1B), was that Low Spontaneous Rate (Low-SR) fibers have a higher threshold for simulation and thus will have demonstrably sharper frequency selectivity than High-SR fibers. The results of the simulation support this framework; Low-SR ANFs were shown to have sharper frequency tuning (Figure ​(Figure1B)1B) than High-SR ANFs throughout a range of characteristic frequencies (CFs). While Low-SR ANFs have sharper frequency selectivity (Figure ​(Figure1B),1B), High-SR ANFs have finer temporal resolution, as the rate of change of the mean firing rate in High-SR ANFs was well above that of Low-SR fibers in the simulation (Figure ​(Figure1C).1C). It would seem that Low-SR and Medium-SR fibers (i.e. Lower-SR fibers) are optimized for “place theory” frequency coding and High-SR fibers are optimized for “volley-theory” synchronous phase locking. Future modeling efforts might maintain the integrity of these two parallel pathways, optimized for fine spectral (Lower-SR) and fine temporal (High-SR) resolution, by separating rather than summing their respective outputs. Figure 1 Innervation sites (A), tuning curves (B) and temporal response properties for Low- and High- SR ANFs

Knock Detection and Evaluation of Kerosene Piston Engine

In this paper, knock detection and analysis methods of the gasoline engine are applied to a modified kerosene engine. Two kinds of signals, the cylinder pressure signal and the vibration signal, are acquired by a pressure sensor mounted in a spark plug and an accelerometer mounted on the cylinder block separately. Due to the influence of noise, such as cam shocks, piston up-and-down motion, crank rotation and so on, the vibration signal should be processed to extract knock feature. Firstly, FFT, a frequency analysis approach, is used to determine the characteristic frequency range of knock. Then, combining the sampling frequency, the vibration signal is divided into different frequency sub-bands, and the characteristic sub-band of DWT, a time-frequency analysis method, is determined. After that, DWT is applied to extract knock feature from the vibration signal. At last, the knock energy evaluation index is used to judge knock intensity. The reference knock energy is chosen by the researchers, and it is not absolutely suitable for the engine operating condition, so intuitive cylinder pressure signal is applied to supplement for knock judgment.

Features of the two-component decomposition of monosilane molecules on a silicon surface under epitaxial-process conditions

Using the results of technological experiments based on a two-component kinetic model (SiH4 → SiH3 + SiH), the range of characteristic decomposition frequencies of silicon-hydride molecule radicals adsorbed by the layer growth surface in the temperature range of 450–700°C is determined; the degree of silicon surface coverage by SiH radicals under epitaxial-growth conditions is estimated. The behavior of the temperature dependences of the factor of surface filling by individual molecule fragments and the rate of their decomposition on the silicon surface are determined under various conditions corresponding to a constant concentration ratio of monosilane radicals (SiH = gSiH3) or constant rates of their decomposition \(\left( {v_{SiH_3 } = \xi v_{SiH} } \right)\) in the entire temperature range. It is shown that the observed shape of the temperature dependence of the molecule decomposition rate on the growth surface is not described by simple activation-type curves, which is associated with features of the interaction of the molecular hydride beam with the Si surface under conditions of low and high levels of surface-bond saturation with hydrogen. The effect of the mechanism of the adsorption of hydrogen atoms and various conditions of their transfer from the molecule to the growth surface on the temperature dependences is considered.

Experimental Research about the Current Characteristic of the Fault Arc in Series based on Wavelet Analysis

In order to solve the fire detection problem of the electrical fault arc in series, it is introduced in this paper to decompose and reconstruct current waveforms of the fault arc in series, based on MALLAT arithmetic of the wavelet transform, which were obtained by the experimental device of the electrical fault arc in different resistance loads and different frequencies. By introducing the wavelet transform method in the data analysis, current waveforms of the fault arc in series are processed with intercalating the wavelet parameter, and the characteristic parameter and frequency range of the fault arc current signal can be distilled. And then, the special frequency range of the fault arc current signal in series, based on different electric loads and different frequencies, can be regarded as the judgment of the fire detecting alarm, which could provide the technical base with the efficient detection method of the electric fault arc in series.

Six-Helix Bundle and Triangle DNA Origami Insulator-Based Dielectrophoresis

Self-assembled DNA nanostructures have large potential for nanoelectronic circuitry, targeted drug delivery, and intelligent sensing. Their applications require suitable methods for manipulation and nanoscale assembly as well as adequate concentration, purification, and separation methods. Insulator-based dielectrophoresis (iDEP) provides an efficient and matrix-free approach for manipulation of micro- and nanometer-sized objects. In order to exploit iDEP for DNA nanoassemblies, a detailed understanding of the underlying polarization and dielectrophoretic migration is essential. Here, we explore the dielectrophoretic behavior of six-helix bundle and triangle DNA origamis with identical sequence but large topological difference and reveal a characteristic frequency range of iDEP trapping. Moreover, the confinement of triangle origami in the iDEP trap required larger applied electric fields. To elucidate the observed DEP migration and trapping, we discuss polarizability models for the two species according to their structural difference complemented by numerical simulations, revealing a contribution of the electrophoretic transport of the DNA origami species in the iDEP trapping regions. The numerical model showed reasonable agreement with experiments at lower frequency. However, the extension of the iDEP trapping regions observed experimentally deviated considerably at higher frequencies. Our study demonstrates for the first time that DNA origami species can be successfully trapped and manipulated by iDEP and reveals distinctive iDEP behavior of the two DNA origamis. The experimentally observed trapping regimes will facilitate future exploration of DNA origami manipulation and assembly at the nano- and microscale as well as other applications of these nanoassemblies with iDEP.

EPR and NMR spectroscopy of transformer oil

EPR spectra in the characteristic frequency range and 1H, 13C, and 17O NMR spectra of fresh, used, and aged (under model conditions) GK grade transformer oil are recorded and analyzed. The EPR spectra show signals from Er3+, Yb3+, Fe2+, and Fe+ in the oxygen environment, and Ti3+ in the sulfur environment. It is shown that 1H NMR spectroscopy is a fast, informative, and reliable method of determination of moisture content of transformer oil. The data obtained confirmed high efficiency of EPR and NMR spectroscopy for analyzing transformer oil and monitoring its hydration processes.

유용방향법 최적화 알고리즘을 사용한 고유진동수에 대한 구조 최적설계 FEA 모듈 개발

In order to find the optimum design of structures that have characteristic natural frequency range, a numerical optimization method to solving eigenvalue problems is a widely used approach. However in the most cases, it is difficult to decide the accurate thickness and shape of structures that have allowable natural frequency in design constraints. Parallel analysis algorithm involving the feasible direction optimization method and Rayleigh-Ritz eigenvalue solving method is developed. The method is implemented by using finite element method. It calculates the optimal thickness and the thickness ratio of individual elements of the 2-D plane element through a parallel algorithm method which satisfy the design constraint of natural frequency. As a result this method of optimization for natural frequency by using finite element method can determine the optimal size or its ratio of geometrically complicated shape and large scale structure.

Field Test of Wellbore Anti-Collision Monitoring System

Avoiding well collision has become an increasingly critical challenge for the drilling industry in recent years. The wellbore Anti-collision Monitoring system is developed because the vibrations caused by an approaching drill bit can be monitored from the existing well casing and used to pre-alarm the wellbore collision. By analyzing the time-domain signal collected by the system in different drilling conditions, the influences of the drilling parameters (RPM and WOB) on drill bit signal are identified; and by analyzing the frequency-domain signal, the characteristic frequency range (200-400Hz) of the drill bit signal is determined. When the drill bit is approaching to the adjacent well, the reconstruction bit signal after band-pass filter changes significantly and agrees well with the on-site situation. The field test results show that the monitoring system is effective and provides a new way to the anti-collision techniques.

Parametric Electrochemical Impedance Spectroscopy Analysis on High Pressure In-Plane SOFC

Electrochemical Impedance Spectroscopy (EIS) analysis was conducted using various cell geometries at different operating conditions including fuel composition, pO2, temperature, and pressure in order to study the characteristics of Rolls-Royce in-plane SOFC. Parametric tests and RC circuit modeling facilitated EIS peak deconvolution to understand each parameter's effect on performance. By comparing EIS peak responses from symmetric button cell and unit cell geometry, four primary processes were identified which are related to 1) anodic activation, 2) fuel diffusion in porous layer, 3) cathodic activation, and 4) cathodic gas diffusion in porous layer. Polarization resistance (Rp) of cathodic activation (process2, p2) with a characteristic frequency range of about 100 to 600 Hz demonstrates (pO2)^-0.6 dependence throughout 1 to 6.4 bar range of operating pressure

Across-Channel Timing Differences as a Potential Code for the Frequency of Pure Tones

When a pure tone or low-numbered harmonic is presented to a listener, the resulting travelling wave in the cochlea slows down at the portion of the basilar membrane (BM) tuned to the input frequency due to the filtering properties of the BM. This slowing is reflected in the phase of the response of neurons across the auditory nerve (AN) array. It has been suggested that the auditory system exploits these across-channel timing differences to encode the pitch of both pure tones and resolved harmonics in complex tones. Here, we report a quantitative analysis of previously published data on the response of guinea pig AN fibres, of a range of characteristic frequencies, to pure tones of different frequencies and levels. We conclude that although the use of across-channel timing cues provides an a priori attractive and plausible means of encoding pitch, many of the most obvious metrics for using that cue produce pitch estimates that are strongly influenced by the overall level and therefore are unlikely to provide a straightforward means for encoding the pitch of pure tones.

Pushing the Envelope of Sound

Normal hearing depends on the amplification of sound in the cochlea. In this issue of Neuron, Fettiplace and colleagues show that prestin-based amplification is a viable mechanism as it is not limited by the outer hair cell's membrane time constant as previously surmised.

Prestin-Driven Cochlear Amplification Is Not Limited by the Outer Hair Cell Membrane Time Constant

SummaryOuter hair cells (OHCs) provide amplification in the mammalian cochlea using somatic force generation underpinned by voltage-dependent conformational changes of the motor protein prestin. However, prestin must be gated by changes in membrane potential on a cycle-by-cycle basis and the periodic component of the receptor potential may be greatly attenuated by low-pass filtering due to the OHC time constant (τm), questioning the functional relevance of this mechanism. Here, we measured τm from OHCs with a range of characteristic frequencies (CF) and found that, at physiological endolymphatic calcium concentrations, approximately half of the mechanotransducer (MT) channels are opened at rest, depolarizing the membrane potential to near −40 mV. The depolarized resting potential activates a voltage-dependent K+ conductance, thus minimizing τm and expanding the membrane filter so there is little receptor potential attenuation at the cell's CF. These data suggest that minimal τm filtering in vivo ensures optimal activation of prestin.

Evaluating Adaptation and Olivocochlear Efferent Feedback as Potential Explanations of Psychophysical Overshoot

Masked detection threshold for a short tone in noise improves as the tone's onset is delayed from the masker's onset. This improvement, known as "overshoot," is maximal at mid-masker levels and is reduced by temporary and permanent cochlear hearing loss. Computational modeling was used in the present study to evaluate proposed physiological mechanisms of overshoot, including classic firing rate adaptation and medial olivocochlear (MOC) feedback, for both normal hearing and cochlear hearing loss conditions. These theories were tested using an established model of the auditory periphery and signal detection theory techniques. The influence of several analysis variables on predicted tone-pip detection in broadband noise was evaluated, including: auditory nerve fiber spontaneous-rate (SR) pooling, range of characteristic frequencies, number of synapses per characteristic frequency, analysis window duration, and detection rule. The results revealed that overshoot similar to perceptual data in terms of both magnitude and level dependence could be predicted when the effects of MOC efferent feedback were included in the auditory nerve model. Conversely, simulations without MOC feedback effects never produced overshoot despite the model's ability to account for classic firing rate adaptation and dynamic range adaptation in auditory nerve responses. Cochlear hearing loss was predicted to reduce the size of overshoot only for model versions that included the effects of MOC efferent feedback. These findings suggest that overshoot in normal and hearing-impaired listeners is mediated by some form of dynamic range adaptation other than what is observed in the auditory nerve of anesthetized animals. Mechanisms for this adaptation may occur at several levels along the auditory pathway. Among these mechanisms, the MOC reflex may play a leading role.

Equilibrium states of a test particle coupled to finite-size heat baths

We report on numerical simulations of the dynamics of a test particle coupled to competing Boltzmann heat baths of finite size. After discussing some features of the single bath case, we show that the presence of two heat baths further constrains the conditions necessary for the test particle to thermalize with the heat baths. We find that thermalization is a spectral property in which the oscillators of the bath with frequencies in the range of the test particle characteristic frequency determine its degree of thermalization. We also find an unexpected frequency shift of the test particle response with respect to the spectra of the two heat baths. Finally, we discuss implications of our results for the study of high-frequency nanomechanical resonators through cold damping cooling techniques and for engineering reservoirs capable of mitigating the back action on a mechanical system.