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1
Pinheiro, Ricardo Bressan, and José Roberto C. Piqueira. "Designing All-Pole Filters for High-Frequency Phase-Locked Loops." Mathematical Problems in Engineering 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/682318.
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Since the phase-locked loop (PLL) circuit was proposed in the 1930s, it is being used for a lot of situations when precise frequency and phase references are required. Among these applications, synchronous telecommunication networks experienced a strong development in order to support the explosive information traffic that the modern society demands. Consequently, bandwidth became a decisive parameter, implying higher and higher frequencies for the clock signals exchanged between the nodes of the networks and detected by PLLs. The necessity to improve clock precision that follows the bandwidth increase provoked the improvement of the filter component of the PLLs, avoiding instability and high-frequency components in the reference signals. Here, a technique of designing this kind of filter is presented, considering second-order filters, implying third-order PLLs. Simulations show that following this technique produces very fast tracking processes, enabling precise operation even for very high frequencies.
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Yagan, Rawana, Ferhat Katmis, and Mehmet C. Onbaşlı. "Engineered Magnetization Dynamics of Magnonic Nanograting Filters." Magnetochemistry 7, no. 6 (June 3, 2021): 81. http://dx.doi.org/10.3390/magnetochemistry7060081.
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Magnonic crystals and gratings could enable tunable spin-wave filters, logic, and frequency multiplier devices. Using micromagnetic models, we investigate the effect of nanowire damping, excitation frequency and geometry on the spin wave modes, spatial and temporal transmission profiles for a finite patterned nanograting under external direct current (DC) and radio frequency (RF) magnetic fields. Studying the effect of Gilbert damping constant on the temporal and spectral responses shows that low-damping leads to longer mode propagation lengths due to low-loss and high-frequency excitations are also transmitted with high intensity. When the nanowire is excited with stronger external RF fields, higher frequency spin wave modes are transmitted with higher intensities. Changing the nanowire grating width, pitch and its number of periods helps shift the transmitted frequencies over super high-frequency (SHF) range, spans S, C, X, Ku, and K bands (3–30 GHz). Our design could enable spin-wave frequency multipliers, selective filtering, excitation, and suppression in magnetic nanowires.
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Sengar, Kanchan, and Arun Kumar. "Fractional Order Capacitor in First-Order and Second-Order Filter." Micro and Nanosystems 12, no. 1 (January 21, 2020): 75–78. http://dx.doi.org/10.2174/1876402911666190821100400.
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Background: Fractional order Butterworth and Chebyshev (low-pass filter circuits, highpass filter circuits and band-pass filters circuits) types of first and second order filter circuits have been simulated and their transfer function are derived. The effect of change of the fractional order α on the behavior of the circuits is investigated. Objective: This paper presents the use of fractional order capacitor in active filters. The expressions for the magnitude, phase, the quality factor, the right-phase frequencies, and the half power frequencies are derived and compared with their previous counterpart. Methods: The circuits have been simulated using Orcad as well as MATLAB for the different value of α. We have developed the fractional gain and phase equations for low pass filter circuits, high pass filter circuits and band pass filter circuits in Sallen-Key topology. Results: It is observed that the bandwidth increases significantly with fractional order other than unity for the low pass as well as high pass and band pass filters. Conclusion: We have also seen that in the frequency domain, the magnitude and phase plots in the stop band change nearly linearly with the fractional order. If we compare the fractional Butterworth filters for low-pass and high-pass type with conventional filters then we find that the roll-off rate is equal to the next higher order filter.
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Yiannakopoulos, G., and P. J. van der Schaaf. "Evaluation of Accelerometer Mechanical Filters on Submerged Cylinders Near an Underwater Explosion." Shock and Vibration 5, no. 4 (1998): 255–65. http://dx.doi.org/10.1155/1998/513249.
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An accelerometer, mounted to a structure near an explosion to measure elasto-plastic deformation, can be excited at its resonant frequency by impulsive stresses transmitted within the structure. This results in spurious high peak acceleration levels that can be much higher than acceleration levels from the explosion itself. The spurious signals also have higher frequencies than the underlying signal from the explosion and can be removed by a low pass filter. This report assesses the performance of four accelerometer and filter assemblies. The assessment involves measurements of the response of a mild steel cylinder to an underwater explosion, in which each assembly is mounted onto the interior surface of the cylinder. Three assemblies utilise a piezoresistive accelerometer in which isolation is provided mechanically. In the fourth assembly, a piezoelectric accelerometer, with a built-in filter, incorporates both mechanical and electronic filtering. This assembly is found to be more suitable because of its secure mounting arrangement, ease of use, robustness and noise free results.
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Fursov, V. A. "Constructing a quadratic-exponential FIR-filter with an extended frequency response midrange." Computer Optics 42, no. 2 (July 24, 2018): 297–305. http://dx.doi.org/10.18287/2412-6179-2018-42-2-297-305.
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This article is concerned with synthesizing filter with finite impulse response (FIR-filters) employed to correct radially symmetric distortions such as defocusing. We propose a new parametric class of finite impulse response filters (FIR-filters) based on a model of the one-dimensional radially symmetric frequency response. In the proposed method, the one-dimensional frequency response is composed of quadratic and exponential functions. The two-dimensional impulse response of the filter is constructed by sampling one-dimensional impulse responses for all directions. The development consists in introducing an extended mid-frequency region of the frequency response, thus increasing the contribution of the frequencies to image correction. Examples are given in order to illustrate the possibility of the high-quality distortion correction. In particular, it is shown that the proposed method provides the restoration quality higher than that obtained when using an optimal Wiener filter (taken from OpenCV).
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Smirnov, A. V. "The analysis of conditions for preservation of gain-frequency and phase-frequency characteristics optimality under analog and digital filters transformation." Russian Technological Journal 8, no. 2 (April 14, 2020): 43–58. http://dx.doi.org/10.32362/2500-316x-2020-8-2-43-58.
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Prototype filters have wide usage for the design of filters with required quality indexes (QI) of gain-frequency response (GFR). The designed filter is obtained from a prototype filter b means of frequency transformation, which preserves these QI. But most of employed frequency transformations result in variations of QI of phase-frequency response (PFR). In this paper we proposed to use prototype filters that are Pareto-optimal for QI of GFR and PFR. Transfer functions of these filters may be found by means of heuristic optimization algorithms. This method will be efficient if the frequency transformation preserves the optimality of filters. It was shown that frequency transformation has this feature if it preserves the result of QI comparison (more or less) for filters with equal orders. Compliance of this criterion was checked for bilinear transformation of analog low pass filters (LPF) into digital LPF and for Konstantinidis transformation of digital LPF into other digital LPF. The analysis showed that Pareto-optimality for QI of GFR and PFR is preserved if the delay-frequency characteristic of the filter has a minimum at zero frequency and has a maximum at the upper boundary of the pass band. These conditions are complied for LPF with sufficiently small unevenness of GFR in the pass band and sufficiently fast decline of GFR at higher frequencies. Examples confirming these conclusions are given.
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Astel, Aleksander, Marcin Stec, and Iwona Rykowska. "Occurrence and Distribution of UV Filters in Beach Sediments of the Southern Baltic Sea Coast." Water 12, no. 11 (October 28, 2020): 3024. http://dx.doi.org/10.3390/w12113024.
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The interest in UV filters’ occurrence in the environment has increased since they were recognized as “emerging contaminants” having potentially adverse impacts on many ecosystems and organisms. Increased worldwide demand for sunscreens is associated with temperature anomalies, high irradiance, and changes in the tourist market. Recently, it has been demonstrated that personal care products, including sunscreens, appear in various ecosystems and geographic locations causing an ecotoxicological threat. Our goal was to determine for the first time the presence of selected organic UV filters at four beaches in the central Pomeranian region in northern Poland and to assess their horizontal and vertical distribution as well as temporal variation at different locations according to the touristic pressure. In this pioneering study, the concentration of five UV filters was measured in core sediments dredged from four exposed beaches (Darłowo, Ustka, Rowy, and Czołpino). UV filters were detected in 89.6% of collected cores at detection frequencies of 0–22.2%, 75–100%, 0–16.7%, and 2.8–25% for benzophenone-1 (BP-1), benzophenone-2 (BP-2), benzophenone-3 (BP-3), and enzacamene (4-MBC), respectively. In terms of seasonality, the concentration of UV filters generally increased in the following order: summer > autumn > spring. No detectable levels of 3-BC (also known as 3-benzylidene camphor) were recorded. No differences were found in the concentration of UV filters according to the depth of the sediment core. During the summer and autumn seasons, all UV filters were detected in higher concentrations in the bathing area or close to the waterline than halfway or further up the beach. Results presented in this study demonstrate that the Baltic Sea coast is not free from UV filters. Even if actual concentrations can be quantified as ng·kg−1 causing limited environmental threat, much higher future levels are expected due to the Earth’s principal climatic zones shifting northward.
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Zhang, Xin, Wensheng Hou, Xiaoying Wu, Lin Chen, and Ning Jiang. "Enhancing Detection of SSMVEP Induced by Action Observation Stimuli Based on Task-Related Component Analysis." Sensors 21, no. 16 (August 4, 2021): 5269. http://dx.doi.org/10.3390/s21165269.
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Action observation (AO)-based brain-computer interface (BCI) is an important technology in stroke rehabilitation training. It has the advantage of simultaneously inducing steady-state motion visual evoked potential (SSMVEP) and activating sensorimotor rhythm. Moreover, SSMVEP could be utilized to perform classification. However, SSMVEP is composed of complex modulation frequencies. Traditional canonical correlation analysis (CCA) suffers from poor recognition performance in identifying those modulation frequencies at short stimulus duration. To address this issue, task-related component analysis (TRCA) was utilized to deal with SSMVEP for the first time. An interesting phenomenon was found: different modulated frequencies in SSMVEP distributed in different task-related components. On this basis, a multi-component TRCA method was proposed. All the significant task-related components were utilized to construct multiple spatial filters to enhance the detection of SSMVEP. Further, a combination of TRCA and CCA was proposed to utilize both advantages. Results showed that the accuracies using the proposed methods were significant higher than that using CCA at all window lengths and significantly higher than that using ensemble-TRCA at short window lengths (≤2 s). Therefore, the proposed methods further validate the induced modulation frequencies and will speed up the application of the AO-based BCI in rehabilitation.
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Lee, Hyeon Kyu, and Young-Seok Choi. "Enhancing SSVEP-Based Brain-Computer Interface with Two-Step Task-Related Component Analysis." Sensors 21, no. 4 (February 12, 2021): 1315. http://dx.doi.org/10.3390/s21041315.
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Among various methods for frequency recognition of the steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) study, a task-related component analysis (TRCA), which extracts discriminative spatial filters for classifying electroencephalogram (EEG) signals, has gathered much interest. The TRCA-based SSVEP method yields lower computational cost and higher classification performance compared to existing SSVEP methods. In spite of its utility, the TRCA-based SSVEP method still suffers from the degradation of the frequency recognition rate in cases where EEG signals with a short length window are used. To address this issue, here, we propose an improved strategy for decoding SSVEPs, which is insensitive to a window length by carrying out two-step TRCA. The proposed method reuses the spatial filters corresponding to target frequencies generated by the TRCA. Followingly, the proposed method accentuates features for target frequencies by correlating individual template and test data. For the evaluation of the performance of the proposed method, we used a benchmark dataset with 35 subjects and confirmed significantly improved performance comparing with other existing SSVEP methods. These results imply the suitability as an efficient frequency recognition strategy for SSVEP-based BCI applications.
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Smith, A. T., and C. M. Baker-Short. "Pharmacological separation of mechanisms contributing to human contrast sensitivity." Visual Neuroscience 10, no. 6 (November 1993): 1073–79. http://dx.doi.org/10.1017/s095252380001018x.
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AbstractTwo basic types of cholinergic receptor have been identified in nervous systems: nicotinic and muscarinic. In the mammalian visual system, the balance of evidence suggests that nicotinic activity is associated primarily with transmission and processing of information while muscarinic activity reflects modulatory influences arising in the brainstem and basal forebrain. We have measured contrast sensitivity functions using a two-alternative forced-choice procedure in young human volunteers with and without administration of nicotine (1.5 mg by buccal absorption) or the muscarinic antagonist scopolamine (1.2 mg orally). Scopolamine elevates contrast-detection thresholds uniformly at all spatial frequencies, consistent with blocking of a nonspecific arousal system. Nicotine, in contrast, improves sensitivity at low spatial frequencies (below about 4 cycle/deg); at higher spatial frequencies sensitivity is, if anything, impaired. Using counterphase gratings, we find that scopolamine elevates thresholds uniformly at all temporal frequencies. Nicotine lowers thresholds at high but not low temporal frequencies. The results obtained with nicotine suggest that contrast sensitivity reflects the activity of two mechanisms, or sets of spatiotemporal filters, that are pharmacologically distinct, the contrast sensitivity function reflecting the envelope of their sensitivities.
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Miek, Daniel, Fynn Kamrath, Patrick Boe, and Michael Höft. "WR-3 Band Waveguide Filter Tolerance Analysis and Surface Metallization Comparison." Journal of Infrared, Millimeter, and Terahertz Waves 41, no. 12 (August 22, 2020): 1576–90. http://dx.doi.org/10.1007/s10762-020-00735-w.
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AbstractIn this paper, a fifth-order WR-3 band waveguide filter with two transmission zeros (TZs) is presented. The design process is described and manufacturing issues are addressed. The filter is designed to fulfill a center frequency of 237.9 GHz and a fractional bandwidth of 2.64%. Three identical filters are manufactured with the classical computerized numerical control (CNC) milling technique in order to obtain information about the manufacturing repeatability for filter structures in the WR-3 band. The comparison shows that even in very high frequency regions a good repeatability can be achieved, if modern high-speed cutting (HSC) CNC milling machines are used. A comprehensive tolerance analysis is accomplished to classify the obtained results. The filters were manufactured from brass to ensure a meaningful comparability and due to the good machining qualities in CNC machines. In order to reduce the losses, the filters are afterwards sputtered with different materials (gold, silver, copper) to evaluate the effect on the insertion loss at very high frequencies. In comparison with the literature, it is shown that even narrow-band filters, which show a high sensitivity to machining tolerances, can be manufactured with high reliability and manufacturing repeatability in modern CNC milling machines. One of the measured filters shows a return loss higher than 20 dB over the whole passband.
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Wood, Debra E., Melissa Varrecchia, Michael Papernov, Denise Cook, and Devon C. Crawford. "Hormonal Modulation of Two Coordinated Rhythmic Motor Patterns." Journal of Neurophysiology 104, no. 2 (August 2010): 654–64. http://dx.doi.org/10.1152/jn.00846.2009.
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Neuromodulation is well known to provide plasticity in pattern generating circuits, but few details are available concerning modulation of motor pattern coordination. We are using the crustacean stomatogastric nervous system to examine how co-expressed rhythms are modulated to regulate frequency and maintain coordination. The system produces two related motor patterns, the gastric mill rhythm that regulates protraction and retraction of the teeth and the pyloric rhythm that filters food. These rhythms have different frequencies and are controlled by distinct mechanisms, but each circuit influences the rhythm frequency of the other via identified synaptic pathways. A projection neuron, MCN1, activates distinct versions of the rhythms, and we show that hormonal dopamine concentrations modulate the MCN1 elicited rhythm frequencies. Gastric mill circuit interactions with the pyloric circuit lead to changes in pyloric rhythm frequency that depend on gastric mill rhythm phase. Dopamine increases pyloric frequency during the gastric mill rhythm retraction phase. Higher gastric mill rhythm frequencies are associated with higher pyloric rhythm frequencies during retraction. However, dopamine slows the gastric mill rhythm frequency despite the increase in pyloric frequency. Dopamine reduces pyloric circuit influences on the gastric mill rhythm and upregulates activity in a gastric mill neuron, DG. Strengthened DG activity slows the gastric mill rhythm frequency and effectively reduces pyloric circuit influences, thus changing the frequency relationship between the rhythms. Overall dopamine shifts dependence of frequency regulation from intercircuit interactions to increased reliance on intracircuit mechanisms.
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B, Pattabhiram, and Sai Veerraju. M. "Harmonic Analysis of Fuzzy Logic Controller Based Active Filter Unit Using Resonant Current Control in Distributed Power System." International Journal of Engineering & Technology 7, no. 3.31 (August 24, 2018): 45. http://dx.doi.org/10.14419/ijet.v7i3.31.18199.
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Wide-ranging utilize of nonlinear loads creates harmonic resonance issues in radial distribution system. Harmonic amplification occurring at different locations in the radial line are due to the behavior of active filter as a harmonic admittance rather conductance. This paper presents fuzzy logic controlled active filter by using resonant current control to damp a harmonic resonance. For controlling active filter as an approximately pure harmonic conductance, collections of different parallel band-pass filters are tuned for resonant current controller at harmonic frequencies. A MATLAB/SIMULINK results illustrate that the fuzzy logic controller based active filter improves higher damping performance correlated with alternative techniques.
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Sipkin, Stuart A., and Arthur L. Lerner-Lam. "Pulse-shape distortion introduced by broadband deconvolution." Bulletin of the Seismological Society of America 82, no. 1 (February 1, 1992): 238–58. http://dx.doi.org/10.1785/bssa0820010238.
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Abstract The availability of broadband digitally recorded seismic data has led to an increasing number of studies using data from which the instrument transfer function has been deconvolved. In most studies, it is assumed that raw ground motion is the quantity that remains after deconvolution. After deconvolving the instrument transfer function, however, seismograms are usually high-pass filtered to remove low-frequency noise caused by very long-period signals outside the frequency band of interest or instabilities in the instrument response at low frequencies. In some cases, data must also be low-pass filtered to remove high-frequency noise from various sources. Both of these operations are usually performed using either zero-phase (acausal) or minimum-phase (causal) filters. Use of these filters can lead to either bias or increased uncertainty in the results, especially when taking integral measures of the displacement pulse. We present a deconvolution method, based on Backus-Gilbert inverse theory, that regularizes the time-domain deconvolution problem and thus mitigates any low-frequency instabilities. We apply a roughening constraint that minimizes the long-period components of the deconvolved signal along with the misfit to the data, emphasizing the higher frequencies at the expense of low frequencies. Thus, the operator acts like a high-pass filter but is controlled by a trade-off parameter that depends on the ratio of the model variance to the residual variance, rather than an ad hoc selection of a filter corner frequency. The resulting deconvolved signal retains a higher fidelity to the original ground motion than that obtained using a postprocess high-pass filter and eliminates much of the bias introduced by such a filter. A smoothing operator can also be introduced that effectively applies a low-pass filter. This smoothing is useful in the presence of blue noise, or if inferences about source complexity are to be made from the roughness of the deconvolved signal.
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Njegić, Jovan, Dejan Živkov, and Jelena Damnjanović. "Business cycles synchronisation between the EU-15 and selected Eastern European Countries – The wavelet coherence approach." Acta Oeconomica 67, no. 4 (December 2017): 539–56. http://dx.doi.org/10.1556/032.2017.67.4.3.
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This paper strives to investigate the level of business cycles synchronisation between 8 Central and Eastern European Countries (CEEC) and the EU-15. We use wavelet coherence and phase difference methodology as a very suitable tool that observes simultaneously the strength of business cycles’ co-movement in the aspect of time as well as in the aspect of frequency. The results indicate that the business cycles of CEECs are generally synchronised with the EU-15 business cycles, whereas distinct differences existed before, during, and after the financial crisis (2008–2009) and during the European sovereign debt crisis (2010–2011). In other words, we demonstrate that very strong business cycles synchronisation occurred in almost all CEECs during crisis periods and at higher wavelet scales, while only moderate synchronisation is recorded in relatively tranquil periods at higher frequencies. The results suggest that smaller CEECs, but also larger countries such as the Czech Republic, Hungary, and to some extent Slovakia as well have a higher level of business cycles synchronisation with the EU-15, particularly in the crisis period at short-run as well as at long-run fluctuations. However, we do not find strong business cycles co-movement in cases of Poland and Latvia via HP and BP filters at higher frequencies during the crisis, which might indicate a higher resistance of these countries to external systemic shocks.
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Mabrouk, Mohamed, Sreeraman Rajan, Miodrag Bolic, Mohamad Forouzanfar, Hilmi R. Dajani, and Izmail Batkin. "Human Breathing Rate Estimation from Radar Returns Using Harmonically Related Filters." Journal of Sensors 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/9891852.
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Radar-based noncontact sensing of life sign signals is often used in safety and rescue missions during disasters such as earthquakes and avalanches and for home care applications. The radar returns obtained from a human target contain the breathing frequency along with its strong higher harmonics depending on the target’s posture. As a consequence, well understood, computationally efficient, and the most popular traditional FFT-based estimators that rely only on the strongest peak for estimates of breathing rates may be inaccurate. The paper proposes a solution for correcting the estimation errors of such single peak-based algorithms. The proposed method is based on using harmonically related comb filters over a set of all possible breathing frequencies. The method is tested on three subjects for different postures, for different distances between the radar and the subject, and for two different radar platforms: PN-UWB and phase modulated-CW (PM-CW) radars. Simplified algorithms more suitable for real-time implementation have also been proposed and compared using accuracy and computational complexity. The proposed breathing rate estimation algorithms provide a reduction of about 81% and 80% in the mean absolute error of breathing rates in comparison to the traditional FFT-based methods using strongest peak detection, for PN-UWB and PM-CW radars, respectively.
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Taghvaeipour, Afshin, Jorge Angeles, and Larry Lessard. "Elastodynamics of a two-limb Schönflies motion generator." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 4 (June 12, 2014): 751–64. http://dx.doi.org/10.1177/0954406214538781.
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The elastodynamic analysis of a two-limb Schönflies motion generators is the subject of this paper. This analysis calls for the calculation of the stiffness and mass matrices. By resorting to the generalized spring concept, the posture-dependent stiffness matrix of the robot is computed. With the motors locked, the motion caused by the flexible components leads to the robot mass matrix. The generalized springs help to simplify the model. Although this simplification filters out the higher natural frequencies, it eases the computation of the posture-dependent stiffness and mass matrices. This provides a valuable tool to simplify the evaluation of the robot performance from an elastodynamic point of view, while the robot executes a given task. Finally, the modal analysis of the McGill Schönflies motion generator, while executing a pick-and-place operation, is conducted; under these conditions, the evolution of the first six natural frequencies is obtained. The elastodynamic performance of the robot for the given task is assessed using the results of the analysis.
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Wrona, Grzegorz, and Marek Jasinski. "AC-DC Converter with Asymmetrical Higher Harmonics Compensation Function in Sustainable AC Grid." Electrical, Control and Communication Engineering 2, no. 1 (April 1, 2013): 5–13. http://dx.doi.org/10.2478/ecce-2013-0001.
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AbstractIn this paper the grid current higher harmonic compensation method for two level AC-DC converters in sustainable AC grid is described. The algorithm is based on Direct Power Control with Space Vector Modulator (DPC-SVM), which was extended by additional Higher Harmonics Compensation (HHC) module. The HHC block is composed of several resonant filters tuned to appropriate frequencies. Both, symmetrical and asymmetrical types of grid currents distortions are analyzed. Operation of the HHC module in stationary αβ coordinates and rotating dq coordinates is discussed. Selected waveforms illustrating operation of the developed algorithm are presented. It is shown that in dq coordinates asymmetrical voltage distortions needs additional effort for its compensation in comparison to symmetrical higher harmonics. The subject is important because in practice asymmetrical higher harmonics usually can appear when one phase nonlinear load is connected to the grid. Even within such conditions the grid connected ACDC converter (GCC) should provide sinusoidal-like current. This assumption provides the reduction of negative impact of the GCC in power quality in Point of Common Coupling (PCC) in sustainable AC grid
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Douglas, A. "Bandpass filtering to reduce noise on seismograms: Is there a better way?" Bulletin of the Seismological Society of America 87, no. 3 (June 1, 1997): 770–77. http://dx.doi.org/10.1785/bssa0870030770.
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Abstract Short-period (SP) P waves at low signal-to-noise ratios (S/Ns) usually appear as signals of about 1 Hz or higher frequencies riding on background noise with frequencies of 0.5 Hz or less. Often bandpass filtering is used to further attenuate the noise relative to the signal to improve the S/N. However, bandpass filtering introduces significant distortion into the signal. Here the use of optimum filters is described, such filters being constructed using autocorrelation functions of the signal and noise derived from noise and signal models. The autocorrelation of the impulse response of the recording system is used to describe the signal. For the noise, a tapered cosine wave is used that has the frequency of the main noise component. To compute the filter, the relative sizes of the signal and noise correlations should be proportional to the square of the S/N. Now, the noise can be estimated by subtracting the estimated signal from the observed seismogram. This property can be used to decide by trial and error on the S/N. The optimum S/N is found by gradually reducing the trial ratio starting from too high a value, until the noise has the amplitude expected and there is no evidence of significant signal in the noise estimate. Examples are given showing how the method can lift observed signals off the background noise with less distortion to the signal than usually occurs with bandpass filtering.
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Baek, Seonghyeon, and Iljae Lee. "Effect of leakage and blockage on the acoustic behavior of particle filters." Noise Control Engineering Journal 67, no. 6 (November 1, 2019): 483–92. http://dx.doi.org/10.3397/1/376744.
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The effects of leakage and blockage on the acoustic performance of particle filters have been examined by using one-dimensional acoustic analysis and experimental methods. First, the transfer matrix of a filter system connected to inlet and outlet pipes with conical sections is measured using a two-load method. Then, the transfer matrix of a particle filter only is extracted from the experiments by applying inverse matrices of the conical sections. In the analytical approaches, the one-dimensional acoustic model for the leakage between the filter and the housing is developed. The predicted transmission loss shows a good agreement with the experimental results. Compared to the baseline, the leakage between the filter and housing increases transmission loss at a certain frequency and its harmonics. In addition, the transmission loss for the system with a partially blocked filter is measured. The blockage of the filter also increases the transmission loss at higher frequencies. For the simplicity of experiments to identify the leakage and blockage, the reflection coefficients at the inlet of the filter system have been measured using two different downstream conditions: open pipe and highly absorptive terminations. The experiments show that with highly absorptive terminations, it is easier to see the difference between the baseline and the defects.
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Sun, Xu, Pengfei Zhu, Yunxia Ping, Kun Zhu, Chaomin Zhang, Xiaohui Sun, and Pei Song. "Transmission and reflection characteristics of normal incidence on silicon-metal-silicon interface." International Journal of Modern Physics B 34, no. 13 (May 20, 2020): 2050135. http://dx.doi.org/10.1142/s0217979220501350.
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We investigate transmission and reflection properties of a broadband pulse with normal incidence on silicon-metal-silicon (SMS) for the first time, to the best of our knowledge. The results show that in lower frequency range, the transmission is close to zero, and the reflection and loss are in the range 0.50–0.90, 0.10 to 0.50, respectively. In higher frequency range, the transmission spectrum has two peaks, with transmittance 0.69, 0.90, and at same frequencies as the transmission peaks, the reflection spectrum has two troughs with reflectance 0.00, 0.02 and corresponding losses are 0.10, 0.29, respectively. This simple waveguide structure may have potential applications in silicon photonics, such as filters and laser oscillation cavities.
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Sugchai, Tantiviwat, Intarawiset Nattapong, and Chanthong Apirun. "Design of Microstrip Triplexer Using Common Dual-Mode Resonator with Multi-Spurious Mode Suppression for Multiband Applications." Applied Mechanics and Materials 763 (May 2015): 182–88. http://dx.doi.org/10.4028/www.scientific.net/amm.763.182.
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A triplexer is an important component for channel separation in microwave front-end systems. This paper proposes a triplexers designed with common dual mode resonator sections have been proposed. By exploiting the variable frequency response of the stepped-impedance resonator, resonators can be shared by the three filter channels of the desired triplexer if their fundamental and the first spurious resonant frequency are properly assigned. Triplexer design method for suppressing spurious responses in the stopband by choosing the constitutive resonators with the same fundamental frequency, but staggered higher order resonant frequencies. The design concept is demonstrated by three of third order parallel-coupled bandpass filters. The bandpass filter is composed of three different stepped impedance resonators for which a general design guideline had been provided in order have the same fundamental frequency and different spurious frequencies. The measured results are in good agreement with the simulated predictions, whereby the spurious responses in the upper stopband can be suppressed below-25dB up to 14 GHz, which can be quite useful for multiband and multiservice applications in future wireless communication systems.
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Motlagh Zadeh, Lina, Noah H. Silbert, Katherine Sternasty, De Wet Swanepoel, Lisa L. Hunter, and David R. Moore. "Extended high-frequency hearing enhances speech perception in noise." Proceedings of the National Academy of Sciences 116, no. 47 (November 4, 2019): 23753–59. http://dx.doi.org/10.1073/pnas.1903315116.
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Young healthy adults can hear tones up to at least 20 kHz. However, clinical audiometry, by which hearing loss is diagnosed, is limited at high frequencies to 8 kHz. Evidence suggests there is salient information at extended high frequencies (EHFs; 8 to 20 kHz) that may influence speech intelligibility, but whether that information is used in challenging listening conditions remains unknown. Difficulty understanding speech in noisy environments is the most common concern people have about their hearing and usually the first sign of age-related hearing loss. Digits-in-noise (DIN), a widely used test of speech-in-noise perception, can be sensitized for detection of high-frequency hearing loss by low-pass filtering the broadband masking noise. Here, we used standard and EHF audiometry, self-report, and successively higher cutoff frequency filters (2 to 8 kHz) in a DIN test to investigate contributions of higher-frequency hearing to speech-in-noise perception. Three surprising results were found. First, 74 of 116 “normally hearing,” mostly younger adults had some hearing loss at frequencies above 8 kHz. Early EHF hearing loss may thus be an easily measured, preventive warning to protect hearing. Second, EHF hearing loss correlated with self-reported difficulty hearing in noise. Finally, even with the broadest filtered noise (≤8 kHz), DIN hearing thresholds were significantly better (P < 0.0001) than those using broadband noise. Sound energy above 8 kHz thus contributes to speech perception in noise. People with “normal hearing” frequently report difficulty hearing in challenging environments. Our results suggest that one contribution to this difficulty is EHF hearing loss.
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Venkatalakshmi, B., and K. Radhika. "Design of Solid Mounted Components Using Bulk Acoustic Wave Technology for Communication." Advanced Materials Research 433-440 (January 2012): 7579–82. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.7579.
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Low power and portable systems working at high frequency are becoming a significant force in the communication industry. SAW filters have been used in wireless communication systems since the early days of mobile phones. But applications at the higher handset frequencies run up against the capability of conventional SAW structures. Bulk Acoustic Wave (BAW) Technology, a relatively recent addition to this portfolio follows MEMS principle to design high performance microwave components for RF communication. Simulation of the Bulk Acoustic Resonator using Butterworth Van Dyke Model (BVD) Model and design of Ladder Filter with the designed resonator in the RF design platform Agilent ADS (Advanced Design System) have been presented. The simulated results confirm the tuning of operating frequency of designed BAW device at 2.4 GHz.
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Amin, Farooq, Sanjay Raman, and Kwang-Jin Koh. "Tunable Q-enhanced LC dual-band filtering at microwave frequencies in 0.13 µm SiGe BiCMOS." International Journal of Microwave and Wireless Technologies 10, no. 5-6 (April 17, 2018): 635–42. http://dx.doi.org/10.1017/s1759078718000429.
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AbstractThis paper presents an active Q-enhanced LC dual-band band-pass filtering approach using parallel synthesis techniques at X- and Ku-bands in 0.13 µm SiGe BiCMOS technology. By employing two independently tunable parallel LC-tanks with either in-phase and out-of-phase addition, independently tunable dual-band filtering is achieved. For higher out-of-band (OOB) attenuation, subtraction of the two 2nd-order bandpass filter is implemented. The two bands are independently tunable in terms of Q and center frequency. The dual-band filter at 9.7 GHz and 13.9 GHz achieves a normalized dynamic range of 165–154.5 dB.Hz with an OOB attenuation of >50 dB below 3 GHz. In between the two bands, the attenuation is 22 dB when the two passbands have 200 MHz bandwidth each. The total group delay is 0.8 ns and 1.9 ns for Q of 20 and 50, respectively. The filter achieves better OOB rejection with wider band channels at X- and Ku-bands compared with state of the art integrated filters. The filter consumes 115–130 mW of DC power. The core die area is 0.53 × 0.7 mm2.
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Matz, Richard, Dieter Götsch, Thomas Goßner, Roman Karmazin, Ruth Männer, and Bernhard Siessegger. "Power Inductors in Ceramic Multilayer Circuit Boards." Journal of Microelectronics and Electronic Packaging 5, no. 4 (October 1, 2008): 161–68. http://dx.doi.org/10.4071/1551-4897-5.4.161.
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Power electronic inductors, with values of several μH, have been integrated into thermally stable ceramic multilayer circuit boards by the use of NiZnCu and MnZn ferrite tapes in low temperature cofired ceramic (LTCC) technology. These ferrites are particularly attractive for switched mode power supplies in automation, drives, and consumer applications, where the miniaturization of modules is triggered by advances in transistor technology and switching frequencies. The small signal analysis of embedded individual inductors and coupled transformer coils reveals the generic design rules for these components and additional materials properties beyond those accessible by ring core measurements. In the process of adapting the materials to LTCC, the distinct differences between the two materials become blurred, for example, they can be engineered to exhibit similar cutoff frequencies. NiZnCu ferrite, which is sinterable in air, may even achieve higher permeability than MnZn ferrite. The latter, however, shows higher saturation flux density and current capacity of buried inductors for power line filters. The coupled inductor design in a transformer is particularly ruled by the shunt capacitance inside the coils and by the fact that Maxwell equations preclude strong magnetic coupling between ferrite-embedded conductor lines. While parasitic capacitances remain tolerable for standard dielectric layer material up to several MHz, the need for magnetic coupling requires a fabrication process for magnetic vias.
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Castrejón, Arturo Mendoza, Herlinda Montiel Sánchez, and Guillermo Alvarez Lucio. "The Domain Dynamic in Fe-Based Amorphous Alloy Ribbons by Means Inductance Spectroscopy." Advanced Materials Research 1083 (January 2015): 21–26. http://dx.doi.org/10.4028/www.scientific.net/amr.1083.21.
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In the present work, a detailed study of the structural relaxation through the complex inductance response by using Inductance Spectroscopy (IS) of Fe-based amorphous ribbons obtained by as quenching ultra-rapid technique, as a function of frequency form 4 to 400 kHz and under thermal treatment during 10, 20, 40, 60, 120 and 180 min, is presented. The analysis of experimental results of IS plots of real (L ́) and imaginary (L ́ ́) inductance show evidence of magnetization processes associated with domain walls: At low fields and low frequencies, L ́ showed a plateau, followed by a dispersion with a relaxation character, the relaxation frequency is about 100 kHz (domain wall bulging). For higher fields, the inductance value depended on the field amplitude (domain wall displacement). As the frequency increased, all the curves merged into the low field plot and exhibited the same relaxation dispersion. The dependence of magnetization processes on the domain wall is determined and interpreted on the basis of the domain wall motion equation. In this way the structural relaxation associated with domain dynamic is discussed and we can establish criteria for the design of certain filters at low frequencies (from 4 to 50 kHz).
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Snyder, S. D., N. Tanaka, and Y. Kikushima. "The Use of Optimally Shaped Piezo-electric Film Sensors in the Active Control of Free Field Structural Radiation, Part 2: Feedback Control." Journal of Vibration and Acoustics 118, no. 1 (January 1, 1996): 112–21. http://dx.doi.org/10.1115/1.2889625.
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Feedback control of free field structural radiation is considered. State equations are formulated with a transformation which decouples the acoustic power error criterion. Using the resultant equations, expressed in terms of “transformed mode” states, the order of the state equations can be significantly reduced at low frequencies. Two experimental implementations of feedback control strategies using shaped piezoelectric polymer film sensors to measure the transformed system states are described. The first of these is a simple analog implementation. The second implementation is in discrete time, where an adaptive algorithm for optimizing the weights of IIR filters for practical use is described. It is shown that by using the outlined control approach significant levels of low frequency acoustic power attenuation can be obtained with no control spillover and subsequent increase in higher frequency acoustic power output.
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Giraud, Anne-Lise, Christian Lorenzi, John Ashburner, Jocelyne Wable, Ingrid Johnsrude, Richard Frackowiak, and Andreas Kleinschmidt. "Representation of the Temporal Envelope of Sounds in the Human Brain." Journal of Neurophysiology 84, no. 3 (September 1, 2000): 1588–98. http://dx.doi.org/10.1152/jn.2000.84.3.1588.
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The cerebral representation of the temporal envelope of sounds was studied in five normal-hearing subjects using functional magnetic resonance imaging. The stimuli were white noise, sinusoidally amplitude-modulated at frequencies ranging from 4 to 256 Hz. This range includes low AM frequencies (up to 32 Hz) essential for the perception of the manner of articulation and syllabic rate, and high AM frequencies (above 64 Hz) essential for the perception of voicing and prosody. The right lower brainstem (superior olivary complex), the right inferior colliculus, the left medial geniculate body, Heschl's gyrus, the superior temporal gyrus, the superior temporal sulcus, and the inferior parietal lobule were specifically responsive to AM. Global tuning curves in these regions suggest that the human auditory system is organized as a hierarchical filter bank, each processing level responding preferentially to a given AM frequency, 256 Hz for the lower brainstem, 32–256 Hz for the inferior colliculus, 16 Hz for the medial geniculate body, 8 Hz for the primary auditory cortex, and 4–8 Hz for secondary regions. The time course of the hemodynamic responses showed sustained and transient components with reverse frequency dependent patterns: the lower the AM frequency the better the fit with a sustained response model, the higher the AM frequency the better the fit with a transient response model. Using cortical maps of best modulation frequency, we demonstrate that the spatial representation of AM frequencies varies according to the response type. Sustained responses yield maps of low frequencies organized in large clusters. Transient responses yield maps of high frequencies represented by a mosaic of small clusters. Very few voxels were tuned to intermediate frequencies (32–64 Hz). We did not find spatial gradients of AM frequencies associated with any response type. Our results suggest that two frequency ranges (up to 16 and 128 Hz and above) are represented in the cortex by different response types. However, the spatial segregation of these two ranges is not systematic. Most cortical regions were tuned to low frequencies and only a few to high frequencies. Yet, voxels that show a preference for low frequencies were also responsive to high frequencies. Overall, our study shows that the temporal envelope of sounds is processed by both distinct (hierarchically organized series of filters) and shared (high and low AM frequencies eliciting different responses at the same cortical locus) neural substrates. This layout suggests that the human auditory system is organized in a parallel fashion that allows a degree of separate routing for groups of AM frequencies conveying different information and preserves a possibility for integration of complementary features in cortical auditory regions.
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Rahman, Akhlaq, and Jim Norman. "Influence of Different Packaging and Footprint Technique for Microwave Absorptive Bessel Filter's Performance." International Symposium on Microelectronics 2012, no. 1 (January 1, 2012): 001073–77. http://dx.doi.org/10.4071/isom-2012-thp23.
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In present day's ultra high speed data transmission environment, passive filters play a very important and critical function to achieve high-end system performance, especially in Microwave frequency ranges of 10 GHz or higher. Excellent electrical specification such as accurate −3dB cutoff frequency bandwidth, stable group delay, along with VSWR characteristics are very important parameters for system performance. Filters mechanical specification is similarly important, if not more. Products need not only be in certain size to fit in the board but also needs to be complement with other components. As available space in PCB become miniature for each component, filters footprint as well as via position need to be in certain ways to optimize board space and performance. Packaging material and packaging techniques play significant role to be ease of mass production as well. While some manufacturers like “Wirebonding” packaging, some like “Through Via”, and “Ball Grid Array” is the packaging choice of some manufacturers. Component vendors need to have capability to change component design space, as the system designers' demand for their choice of footprint and packaging environment. Moreover, these stringent mechanical specifications cannot compromise the electrical specification. To realize the effect of different packaging technique, we extensively studied several packaging techniques for Bessel filters with −3dB cutoff frequencies of 7 GHz to 10 GHz. We explored “stud bump ball grid array”, “wirebonding”, and “land grid array” footprint packaging. We modeled different packaging technique and incorporated that into simulation to design the filter. We successfully manufacture surface mount filters with three different footprint packaging. We explored the influence of each packaging technique for electrical performance. We studied the hidden parasitic introduction from each packaging style and the detrimental effect of these to electrical performance, especially for frequency of 7 GHz to 10 GHz. We showed the advantages and disadvantages of all three kind of packaging technology in respect of electrical as well as mechanical specification.
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Moore, Brian C. J., Jie Wan, Ajanth Varathanathan, Sophie Naddell, and Thomas Baer. "No Effect of Musical Training on Frequency Selectivity Estimated Using Three Methods." Trends in Hearing 23 (January 2019): 233121651984198. http://dx.doi.org/10.1177/2331216519841980.
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It is widely believed that the frequency selectivity of the auditory system is largely determined by processes occurring in the cochlea. If so, musical training would not be expected to influence frequency selectivity. Consistent with this, auditory filter shapes for low center frequencies do not differ for musicians and nonmusicians. However, it has been reported that psychophysical tuning curves (PTCs) at 4000 Hz were sharper for musicians than for nonmusicians. This study explored the origin of the discrepancy across studies. Frequency selectivity was estimated for musicians and nonmusicians using three methods: fast PTCs with a masker that swept in frequency, “traditional” PTCs obtained using several fixed masker center frequencies, and the notched-noise method. The signal frequency was 4000 Hz. The data were fitted assuming that each side of the auditory filter had the shape of a rounded-exponential function. The sharpness of the auditory filters, estimated as the Q10 values, did not differ significantly between musicians and nonmusicians for any of the methods, but detection efficiency tended to be higher for the musicians. This is consistent with the idea that musicianship influences auditory proficiency but does not influence the peripheral processes that determine the frequency selectivity of the auditory system.
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Matsumoto, Yasunao, Yukio Takahashi, Setsuo Maeda, Hiroki Yamaguchi, Kazuhiro Yamada, and Jishnu K. Subedi. "An Investigation of the Perception Thresholds of Band-Limited Low Frequency Noises: Influence of Bandwidth." Journal of Low Frequency Noise, Vibration and Active Control 22, no. 1 (March 2003): 17–25. http://dx.doi.org/10.1260/026309203769018059.
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Perception thresholds of complex low frequency noises have been investigated in a laboratory experiment. Sound pressure levels that were just perceptible by subjects were measured for three complex noises and three pure tones. The complex noises had a flat constant spectrum over the frequency range 2 to 10, 20, or 40 Hz and decreased at 15 dB per octave at higher frequencies. The frequencies of the pure tones used in this study were 10, 20 and 40 Hz. The perception thresholds were obtained using an all-pass filter, one-third octave band filters, and the G frequency weighting defined in ISO 7196. The G-weighted sound pressure levels obtained were compared with 100 dB which is described in ISO 7196 as the G-weighted level corresponding to the threshold of sounds in the frequency range 1 to 20 Hz. The perception thresholds of the pure tones measured in this study were comparable to the results available in various previous studies. The one-third octave sound pressure levels obtained for the thresholds of the complex noises appeared to be lower than the measured thresholds of the pure tones. The G-weighted sound pressure levels obtained for the thresholds of the complex noises appeared to be lower than 100 dB.
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Carney, L. H., and T. C. Yin. "Temporal coding of resonances by low-frequency auditory nerve fibers: single-fiber responses and a population model." Journal of Neurophysiology 60, no. 5 (November 1, 1988): 1653–77. http://dx.doi.org/10.1152/jn.1988.60.5.1653.
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1. We recorded responses of low-frequency auditory nerve fibers (characteristic frequency (CF) less than 3 kHz) in the cat to resonant stimuli with varied natural frequencies, damping coefficients, and sound pressure levels. Responses to resonances were synchronized to frequencies lying between the peak frequency of the stimulus spectrum and a frequency near the fiber's CF. The frequency of the dominant synchrony in the response varied systematically as a function of the stimulus parameters. 2. More lightly damped resonances, which have sharp spectral peaks, elicited synchrony closer to the peak frequency, whereas the broader peaks of more highly damped resonances elicited synchrony closer to the fiber's CF. Thus as the stimulus was varied from an undamped tone to a highly damped transient, the dominant component of the synchronized response moved from the peak frequency of the stimulus toward the CF of the fiber. The trajectory of the dominant component varied as a function of stimulus level, with higher levels resulting in synchrony biased toward the peak of the stimulus spectrum over a wider range of damping. 3. The frequency tuning and synchronization characteristics of a fiber, along with the stimulus parameters, determined the temporal properties of its response to complex stimuli. Using reverse correlation (revcor) filters to characterize the tuning and synchronization of auditory nerve fibers, we were able to predict the temporal properties of responses to resonant stimuli. 4. A parametric model was fit to measured revcor functions derived from responses of auditory nerve fibers to wideband noise. In this way, a bank of model revcor filters was developed based on our population of measured filters. 5. The filter bank was used to model the response of a population of auditory nerve fibers to resonances. Temporal patterns present in the response of a population of fibers encoded the parameters of resonant stimuli. 6. The model revcor filter bank provided a means of studying temporal response patterns of the population of fibers to other complex sounds. 7. The output of the population model is a representation of the temporal information provided by the auditory periphery to the central nervous system; thus it provides a potentially useful tool for testing hypotheses concerning the processing of temporal information by the central auditory system.(ABSTRACT TRUNCATED AT 400 WORDS)
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Marković, Ivo, Milka Potrebić, and Dejan Tošić. "Memristors as Candidates for Replacing Digital Potentiometers in Electric Circuits." Electronics 10, no. 2 (January 15, 2021): 181. http://dx.doi.org/10.3390/electronics10020181.
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Digital potentiometers are substantial components for the design of many mixed-signal electronic circuits and systems. Their capability to program resistance value almost instantly provides hardware designers an additional level of freedom. Unfortunately, this feature is limited to DC and lower frequencies, due to parasitic effects. Nowadays, memristors as continuously tunable resistors are becoming candidates for potentiometer successors. Memristors are two-terminal non-volatile devices which have less significant parasitic effects and a wide resistance range. The memristance value can be changed on the fly. Using nanotechnology, memristor implementation has a nanoscale footprint with nanosecond transition between resistive states. In this paper, we present a comparison between the frequency characteristics of digital potentiometers and the only commercially available memristors. Memristor parasitic effects dominate at higher frequencies which extends the bandwidth. In order to present the advantages of memristive circuits, we have analyzed and implemented tunable circuits such as a voltage divider, an inverting amplifier, a high-pass filter, and a phase shifter. A commercially available memristor by KnowM Inc. is used for this purpose. Experimental results obtained by the measurements verify that a memristor has equal or better characteristics than a digital potentiometer. Memristive realizations of voltage dividers and inverting amplifiers have a wider bandwidth, while filters and phase shifters with a memristor have almost identical frequency characteristics as the corresponding realizations with a digital potentiometer.
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HO, CHARLOTTE YUK-FAN, BINGO WING-KUEN LING, JOSHUA D. REISS, and XINGHUO YU. "GLOBAL STABILITY, LIMIT CYCLES AND CHAOTIC BEHAVIORS OF SECOND ORDER INTERPOLATIVE SIGMA DELTA MODULATORS." International Journal of Bifurcation and Chaos 21, no. 06 (June 2011): 1755–72. http://dx.doi.org/10.1142/s0218127411029410.
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It is well known that second order lowpass interpolative sigma delta modulators (SDMs) may suffer from instability and limit cycle problems when the magnitudes of the input signals are at large and at intermediate levels, respectively. In order to solve these problems, we propose to replace the second order lowpass interpolative SDMs to a specific class of second order bandpass interpolative SDMs with the natural frequencies of the loop filters very close to zero. The global stability property of this class of second order bandpass interpolative SDMs is characterized and some interesting phenomena are discussed. Besides, conditions for the occurrence of limit cycle and fractal behaviors are also derived, so that these unwanted behaviors will not happen or can be avoided. Moreover, it is found that these bandpass SDMs may exhibit irregular and conical-like chaotic patterns on the phase plane. By utilizing these chaotic behaviors, these bandpass SDMs can achieve higher signal-to-noise ratio (SNR) and tonal suppression than those of the original lowpass SDMs.
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Segovia-Chaves, Francis, Herbert Vinck-Posada, and Edgar A. Gómez. "Transmittance in a dispersive quasiperiodic photonic crystal." International Journal of Modern Physics B 35, no. 04 (January 28, 2021): 2150061. http://dx.doi.org/10.1142/s0217979221500612.
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In this work, transmittance spectrum for a quasiperiodic one-dimensional photonic crystal, composed of high-temperature superconductor and semiconductor layers arranged within the crystal based on a Dodecanacci sequence, has been calculated using the transfer matrix method and the two-fluid model. The critical temperature of the superconductor depends on the hydrostatic pressure, while the semiconductor’s plasma frequency and dielectric constant were considered to be dependent on both the pressure and temperature applied. We have found that the transmittance spectrum shows the band gaps unfolded and increased in number when the Dodecanacci sequence increased. In addition, this work shows that transmission responses can be tuned to higher frequencies as pressure increases. However, a small red shift of the transmittance spectrum can be observed as temperature increases. Finally, the research observed the maximization of the band gaps by increasing the thickness of the superconductor layers. We hope this work may be considered for application in tunable narrowband filters.
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Ulrich, Daniel. "Dendritic Resonance in Rat Neocortical Pyramidal Cells." Journal of Neurophysiology 87, no. 6 (June 1, 2002): 2753–59. http://dx.doi.org/10.1152/jn.2002.87.6.2753.
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Dendritic integration of synaptic signals is likely to be an important process by which nerve cells encode synaptic input into spike output. However, the response properties of dendrites to time-varying inputs are largely unknown. Here, I determine the transfer impedance of the apical dendrite in layer V pyramidal cells by dual whole cell patch-clamp recordings in slices of rat somatosensory cortex. Sinusoidal current waveforms of linearly changing frequencies (0.1–25 Hz) were alternately injected into the soma or apical dendrite and the resulting voltage oscillations recorded by the second electrode. Dendrosomatic and somatodendritic transfer impedances were calculated by Fourier analysis. At near physiological temperatures ( T∼35°C), the transfer impedance had a maximal magnitude at low frequencies ( f res ∼6 Hz). In addition, voltage led current up to ∼3 Hz, followed by a current lead over voltage at higher frequencies. Thus the transfer impedance of the apical dendrite is characterized by a low-frequency resonance. The frequency of the resonance was voltage dependent, and its strength increased with dendritic distance. The resonance was completely abolished by the I h channel blocker ZD 7288. Dendrosomatic and somatodendritic transfer properties of the apical dendrite were independent of direction or amplitude of the input current, and the responses of individual versus distributed inputs were additive, thus implying linearity. For just threshold current injections, action potentials were generated preferentially at the resonating frequency. I conclude that due to the interplay of a sag current ( I h) with the membrane capacitance, layer V pyramids can act as linear band-pass filters with a frequency preference in the theta frequency band.
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Lankheet, Martin J., Uroš Cerkvenik, Ole N. Larsen, and Johan L. van Leeuwen. "Frequency tuning and directional sensitivity of tympanal vibrations in the field cricket Gryllus bimaculatus." Journal of The Royal Society Interface 14, no. 128 (March 2017): 20170035. http://dx.doi.org/10.1098/rsif.2017.0035.
Full textAbstract:
Female field crickets use phonotaxis to locate males by their calling song. Male song production and female behavioural sensitivity form a pair of matched frequency filters, which in Gryllus bimaculatus are tuned to a frequency of about 4.7 kHz. Directional sensitivity is supported by an elaborate system of acoustic tracheae, which make the ears function as pressure difference receivers. As a result, phase differences between left and right sound inputs are transformed into vibration amplitude differences. Here we critically tested the hypothesis that acoustic properties of internal transmissions play a major role in tuning directional sensitivity to the calling song frequency, by measuring tympanal vibrations as a function of sound direction and frequency. Rather than sharp frequency tuning of directional sensitivity corresponding to the calling song, we found broad frequency tuning, with optima shifted to higher frequencies. These findings agree with predictions from a vector summation model for combining external and internal sounds. We show that the model provides robust directional sensitivity that is, however, broadly tuned with an optimum well above the calling song frequency. We therefore advocate that additional filtering, e.g. at a higher (neuronal) level, significantly contributes to frequency tuning of directional sensitivity.
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Bonnet-Bidaud, J. M., M. Mouchet, E. Falize, L. Van Box Som, C. Busschaert, D. A. H. Buckley, H. Breytenbach, T. R. Marsh, R. P. Ashley, and V. S. Dhillon. "Fast quasi-periodic oscillations in the eclipsing polar VV Puppis from VLT and XMM-Newton observations." Astronomy & Astrophysics 633 (January 2020): A145. http://dx.doi.org/10.1051/0004-6361/201935741.
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We present high time resolution optical photometric data of the polar VV Puppis obtained simultaneously in three filters (u′, HeII λ4686, r′) with the ULTRACAM camera mounted at the ESO-VLT telescope. An analysis of a long 50 ks XMM-Newton observation of the source, retrieved from the database, is also provided. Quasi-periodic oscillations (QPOs) are clearly detected in the optical during the source bright phase intervals when the accreting pole is visible, confirming the association of the QPOs with the basis of the accretion column. QPOs are detected in the three filters at a mean frequency of ∼0.7 Hz with a similar amplitude ∼1%. Mean orbitally-averaged power spectra during the bright phase show a rather broad excess with a quality factor Q = ν/Δν = 5−7 but smaller data segments commonly show a much higher coherency with Q up to 30. The X-ray Multi-mirror Mission XMM (0.5–10 keV) observation provides the first accurate estimation of the hard X-ray component with a high kT ∼ 40 keV temperature and confirms the high extreme ultraviolet (EUV)-soft/hard ratio in the range of 4−15 for VV Pup. The detailed X-ray orbital light curve displays a short Δϕ ≃ 0.05 ingress into self-eclipse of the active pole, indicative of an accretion shock height of ∼75 km. No significant X-ray QPOs are detected with an amplitude upper limit of ∼30% in the range 0.1–5 Hz. Detailed hydrodynamical numerical simulations of the post-shock accretion region with parameters consistent with VV Pup demonstrate that the expected frequencies from radiative instability are identical for X-rays and optical regime at values ν ∼ 40–70 Hz, more than one order magnitude higher than observed. This confirms previous statements suggesting that present instability models are unable to explain the full QPO characteristics within the parameters commonly known for polars.
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Gandais, Madeleine, and Mireille Allais. "Nanoparticles of Cd(S,Se) grown in silicate glasses study by High Resolution Transmission Electron Microscopy (HRTEM) assisted by image treatment." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 736–37. http://dx.doi.org/10.1017/s0424820100176812.
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CdSxSe1-x doped glasses have raised large interest in the recent past years. They are commercially available as sharp cut-off filters with optical absorption edge varying from yellow to deep red as the composition x varies from 1 to 0, according to the properties of bulk Cd(S,Se) compounds, On the other hand glasses prepared in laboratory present different optical properties in relation with excitonic confinement when the semiconductor grains are smaller than 5nm : increase of the third order nonlinear optical susceptibility, shift of the absorption edge toward higher energy, quantum size effects. In order to improve the understanding of the optical properties, it is important to get fine structural informations on the semiconductor phase : crystallographic structure (which may be different than in bulk materials), morphology, size and defects. Comparatively to optical investigations, there have been few structural studies of the semiconductors doped glasses. HRTEM is potentially a powerful method for examining nanocrystals in low concentration within glass. Practically however, the sharpness of the crystal images is reduced by the presence of background signal originating mainly from glass. Numerical treatment of filtering through Fourier transformation presents several advantages. A large part of the signal originating from glass (at low frequencies) and from statiscal noise (at high frequencies) may be suppressed as shown in Figures 1 and 2. The Fourier transform (Figure 2c) may be used for measuring the lattice parameters more easely than the lattice image.
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Yang, Hailong, Xiaoli Xi, Lili Wang, Yuchen Zhao, and Xiaomin Shi. "Selectivity and in-band impedance enhancement of a compact slot antenna with defected ground structures." International Journal of Microwave and Wireless Technologies 11, no. 10 (May 27, 2019): 1010–16. http://dx.doi.org/10.1017/s1759078719000734.
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AbstractIn this study, a new ultra-wideband (UWB) band-edge selectivity antenna with a modified radiation slot using defected ground structure (DGS) is presented to obtain bandpass filtering reflection coefficient and gain performance. The well-designed DGS is designed on backside metallic of the substrate and can be seen as a low-pass filter that provides a good roll-off at a higher frequency. By connecting the DGS and the stepped slot and making them merge with each other, good cut-off property in the upper passband and better in-band impedance characteristics are obtained. Measured results show that the proposed design not only shows good band-edge selectivity in reflection coefficient and gain performance but also has a good impedance matching of −13.5 dB reflection coefficients and a good radiation efficiency of 90% in the operating frequencies. The measured bandwidth defined with the reflection coefficient less than −10 dB is from 3.1–11.2 GHz. Furthermore, the size of the filtering UWB antenna is 22 mm × 12 mm, which is smaller than many individual UWB antennas and UWB filters.
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Ris, L., M. Hachemaoui, N. Vibert, E. Godaux, P. P. Vidal, and L. E. Moore. "Resonance of Spike Discharge Modulation in Neurons of the Guinea Pig Medial Vestibular Nucleus." Journal of Neurophysiology 86, no. 2 (August 1, 2001): 703–16. http://dx.doi.org/10.1152/jn.2001.86.2.703.
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The modulation of action potential discharge rates is an important aspect of neuronal information processing. In these experiments, we have attempted to determine how effectively spike discharge modulation reflects changes in the membrane potential in central vestibular neurons. We have measured how their spike discharge rate was modulated by various current inputs to obtain neuronal transfer functions. Differences in the modulation of spiking rates were observed between neurons with a single, prominent after hyperpolarization (AHP, type A neurons) and cells with more complex AHPs (type B neurons). The spike discharge modulation amplitudes increased with the frequency of the current stimulus, which was quantitatively described by a neuronal model that showed a resonance peak >10 Hz. Modeling of the resonance peak required two putative potassium conductances whose properties had to be markedly dependent on the level of the membrane potential. At low frequencies (≤0.4 Hz), the gain or magnitude functions of type A and B discharge rates were similar relative to the current input. However, resting input resistances obtained from the ratio of the membrane potential and current were lower in type B compared with type A cells, presumably due to a higher level of active potassium conductances at rest. The lower input resistance of type B neurons was compensated by a twofold greater sensitivity of their firing rate to changes in membrane potential, which suggests that synaptic inputs on their dendritic processes would be more efficacious. This increased sensitivity is also reflected in a greater ability of type B neurons to synchronize with low-amplitude sinusoidal current inputs, and in addition, their responses to steep slope ramp stimulation are enhanced over the more linear behavior of type A neurons. This behavior suggests that the type B MVNn are moderately tuned active filters that promote high-frequency responses and that type A neurons are like low-pass filters that are well suited for the resting tonic activity of the vestibular system. However, the more sensitive and phasic type B neurons contribute to both low- and high-frequency control as well as signal detection and would amplify the contribution of both irregular and regular primary afferents at high frequencies.
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Perederko, A. L. "ADAPTIVE MECHANICAL FILTER FOR PIEZOELECTRIC ACCELEROMETER." Collection of scientific works of the Military Institute of Kyiv National Taras Shevchenko University, no. 70 (2021): 60–68. http://dx.doi.org/10.17721/2519-481x/2021/70-06.
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When conducting dynamic tests, when simulating shock effects, the measurement system - from the sensor to the data acquisition unit is subject to significant overloads. In this circuit, the accelerometer is the most vulnerable link. Therefore, piezoelectric accelerometers have become widely used in measuring shocks as more reliable and durable, but they also have a number of disadvantages. Thus, under broadband vibration effects, excitation in the region of mechanical resonance is observed. That is, the material of the sensor crystal may not have an excessive mechanical load, but generate a large amount of output charge due to the resonance of the sensor. This increases the electrical signal and can lead to saturation or, in many cases, damage to the signal shapers and amplifiers following the sensor. The result of such modes of operation is the loss of data due to the displacement of direct current over time. There is often a shift of the zero level of the output signal. When piezoelectric elements are in resonance, there may be a relative displacement of the sensing element. This state of overload leads to the appearance of parasitic output charges, which leads to a change in the generated charge in a short period of time. Due to mechanical overload, under the action of high-intensity shocks, physical destruction of the sensor is also possible. In many cases, the use of mechanical filters made of viscoelastic materials, which are placed between the object of measurement and the piezoelectric accelerometer (sensor), prevents the undesirable consequences of these shortcomings and improves the process of measuring shocks. The use of mechanical filters made of viscoelastic materials makes it possible to significantly reduce the amplitude of oscillations of the piezoelectric accelerometer (over -12 dB) and shift its resonant frequency towards higher frequencies. That is, the use of mechanical filters significantly reduces the mechanical load on the sensor, which makes the process of measuring vibration (especially shock) more predictable.
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Hallum, Luke E., Michael S. Landy, and David J. Heeger. "Human primary visual cortex (V1) is selective for second-order spatial frequency." Journal of Neurophysiology 105, no. 5 (May 2011): 2121–31. http://dx.doi.org/10.1152/jn.01007.2010.
Full textAbstract:
A variety of cues can differentiate objects from their surrounds. These include “first-order” cues such as luminance modulations and “second-order” cues involving modulations of orientation and contrast. Human sensitivity to first-order modulations is well described by a computational model involving spatially localized filters that are selective for orientation and spatial frequency (SF). It is widely held that first-order modulations are represented by the firing rates of simple and complex cells (“first-order” neurons) in primary visual cortex (V1) that, likewise, have spatially localized receptive fields that are selective for orientation- and SF. Human sensitivity to second-order modulations is well described by a filter-rectify-filter (FRF) model, with first- and second-order filters selective for orientation and SF. However, little is known about how neuronal activity in visual cortex represents second-order modulations. We tested the FRF model by using an functional (f)MRI-adaptation protocol to characterize the selectivity of activity in visual cortex to second-order, orientation-defined gratings of two different SFs. fMRI responses throughout early visual cortex exhibited selective adaptation to these stimuli. The low-SF grating was a more effective adapter than the high-SF grating, incompatible with the FRF model. To explain the results, we extended the FRF model by incorporating normalization, yielding a filter-rectify-normalize-filter model, in which normalization enhances selectivity for second-order SF but only for low spatial frequencies. We conclude that neurons in human visual cortex are selective for second-order SF, that normalization (surround suppression) contributes to this selectivity, and that the selectivity in higher visual areas is simply fed forward from V1.
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Purpura, Keith, Daniel Tranchina, Ehud Kaplan, and Robert M. Shapley. "Light adaptation in the primate retina: Analysis of changes in gain and dynamics of monkey retinal ganglion cells." Visual Neuroscience 4, no. 1 (January 1990): 75–93. http://dx.doi.org/10.1017/s0952523800002789.
Full textAbstract:
AbstractThe responses of monkey retinal ganglion cells to sinusoidal stimuli of various temporal frequencies were measured and analyzed at a number of mean light levels. Temporal modulation tuning functions (TMTFs) were measured at each mean level by varying the drift rate of a sine-wave grating of fixed spatial frequency and contrast. The changes seen in ganglion cell temporal responses with changes in adaptation state were similar to those observed in human subjects and in turtle horizontal cells and cones tested with sinusoidally flickering stimuli; “Weber's Law” behavior was seen at low temporal frequencies but not at higher temporal frequencies. Temporal responses were analyzed in two ways: (1) at each light level, the TMTFs were fit by a model consisting of a cascade of low- and high-pass filters; (2) the family of TMTFs collected over a range of light levels for a given cell was fit by a linear negative feedback model in which the gain of the feedback was proportional to the mean light level. Analysis (1) revealed that the temporal responses of one class of monkey ganglion cells (M cells) were more phasic at both photopic and mesopic light levels than the responses of P ganglion cells. In analysis (2), the linear negative feedback model accounted reasonably well for changes in gain and dynamics seen in three P cells and one M cell. From the feedback model, it was possible to estimate the light level at which the dark-adapted gain of the cone pathways in the primate retina fell by a factor of two. This value was two to three orders of magnitude lower than the value estimated from recordings of isolated monkey cones. Thus, while a model which includes a single stage of negative feedback can account for the changes in gain and dynamics associated with light adaptation in the photopic and mesopic ranges of vision, the underlying physical mechanisms are unknown and may involve elements in the primate retina other than the cone.
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Wu, Mingkui, Xiaohong Zhang, Wanke Liu, Renpan Wu, Renlan Zhang, Yuan Le, and Yuexia Wu. "Influencing Factors of GNSS Differential Inter-System Bias and Performance Assessment of Tightly Combined GPS, Galileo, and QZSS Relative Positioning for Short Baseline." Journal of Navigation 72, no. 04 (December 27, 2018): 965–86. http://dx.doi.org/10.1017/s0373463318001017.
Full textAbstract:
This paper first investigates the influencing factors of between-receiver Differential Inter-System Bias (DISB) between overlapping frequencies of the Global Positioning System (GPS), Galileo and the Quasi-Zenith Satellite System (QZSS). It was found that the receiver reboot and the type of observations may have an impact on DISBs. The impact of receiver firmware upgrades and the activation of anti-multipath filters are also investigated and some new results are presented. Then a performance evaluation is presented of tightly combined relative positioning for a short baseline with GPS/Galileo/QZSS L1-E1-L1/L5-E5a-L5 observations with the current constellations, in which the recently launched Galileo and QZSS satellites will also be included. It is demonstrated that when DISBs are a priori calibrated and corrected, the tightly combined model can deliver a much higher empirical ambiguity resolution success rate and positioning accuracy with respect to the classical loosely combined model, especially under environments where the observed satellites for each system are limited and only single-frequency observations are available. The ambiguity dilution of precision, bootstrapping success rate, and ratio values are analysed to illustrate the benefits of the tightly combined model as well.
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Abtahi, Farhad, Fernando Seoane, and Kaj Lindecrantz. "Electrical bioimpedance spectroscopy in time-variant systems: Is undersampling always a problem?" Journal of Electrical Bioimpedance 5, no. 1 (August 8, 2019): 28–33. http://dx.doi.org/10.5617/jeb.801.
Full textAbstract:
Abstract During the last decades, Electrical Bioimpedance Spectroscopy (EBIS) has been applied mainly by using the frequency-sweep technique, across a range of many different applications. Traditionally, the tissue under study is considered to be time-invariant and dynamic changes of tissue activity are ignored by treating the changes as a noise source. A new trend in EBIS is simultaneous electrical stimulation with several frequencies, through the application of a multi-sine, rectangular or other waveform. This method can provide measurements fast enough to sample dynamic changes of different tissues, such as myocard. This high sampling rate comes at a price of reduction in SNR and the increase in complexity of devices. Although the frequency-sweep technique is often inadequate for monitoring the dynamic changes in a variant system, it can be used successfully in applications focused on the time-invariant or slowly-variant part of a system. However, in order to successfully use frequency-sweep EBIS for monitoring time-variant systems, it is paramount to consider the effects of aliasing and especially the folding of higher frequencies, on the desired frequency e.g. DC level. This paper discusses sub-Nyquist sampling of thoracic EBIS measurements and its application in the case of monitoring pulmonary oedema. It is concluded that by considering aliasing, and with proper implementation of smoothing filters, as well as by using random sampling, frequency-sweep EBIS can be used for assessing time-invariant or slowly-variant properties of time-variant biological systems, even in the presence of aliasing. In general, undersampling is not always a problem, but does always require proper consideration.
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Schreiner, C. E., and M. W. Raggio. "Neuronal responses in cat primary auditory cortex to electrical cochlear stimulation. II. Repetition rate coding." Journal of Neurophysiology 75, no. 3 (March 1, 1996): 1283–300. http://dx.doi.org/10.1152/jn.1996.75.3.1283.
Full textAbstract:
1. Responses of neurons in primary auditory cortex (AI) of the barbiturate-anesthetized adult cat were studied using cochlear stimulation with electrical and acoustic stimuli. Neuronal responses to acoustic stimulation with brief biphasic clicks of the ear ipsilateral to the studied cortical hemisphere were compared with those evoked by electrical stimulation of the contralateral cochlea with brief biphasic electrical pulses delivered via a feline cochlear prosthesis. The contralateral ear was deafened immediately before implantation of the cochlear prosthesis. The feline cochlear prosthesis consisted of four bipolar electrode pairs and was placed in the scala tympani. Two bipolar electrode conditions were used for stimulation: one near radial pair with electrode spacing of 0.25-0.5 mm, and one longitudinal pair with electrode spacing of approximately 6 mm. 2. The firing rates obtained from single- and multiple-neuron recordings were measured as a function of stimulus repetition rate of electrical and acoustic pulses. From period histograms over a recording interval of 1,000 ms, the driven firing rate to repetition rates from 2 to 38 Hz was obtained and repetition rate transfer functions (RRTFs) were constructed. The RRTFs were characterized as low-pass or band-pass filters and several descriptors were obtained, such as the repetition rate producing the highest driven activity, high and low cutoff frequencies 6 dB below maximum firing rate, and maximum firing rate. 3. For a given neuron, the main characteristics of cortical RRTFs obtained with electrical and acoustic cochlear stimulation were quite similar. However, some small but statistically significant differences in the best repetition rate, cutoff frequencies, and maximum firing rate could be observed between the different stimulation modes. The proportion of band-pass RRTFs was larger for electrical stimulation (57%) than for acoustic stimulation (41%). The high cutoff frequencies for electrical stimulation were slightly but consistently higher than for acoustic RRTFs of the same neuron and the maximum firing rate for electrical stimulation was significantly higher than that evoked by ipsilateral acoustic stimulation. 4. The entrainment of cortical neurons to electrical and acoustic pulses was determined and entrainment profiles were constructed. For a given neuron, electrical entrainment profiles showed higher cutoff frequencies than with acoustic stimulation when judged with a fixed entrainment criterion of 0.25 spikes per event. The maximum entrainment seen for electrical stimulation was approximately 20% higher than seen for the same neuron with acoustic stimulation. 5. Correlation analysis of repetition coding and latency parameters revealed several relationships between these response aspects. Most prominent among them was a significant correlation between measures of the response latency and estimates of the ability to follow temporal repetitions for acoustic as well as electrical conditions. 6. Parametric and comparative evaluations of cortical responses to acoustic and electrical cochlear stimulation support the conclusion that the temporal resolution seen in cortical neurons is largely a consequence of central processing mechanisms based on cell and circuit properties and to a lesser degree a consequence of particular spatial and temporal peripheral excitation patterns. The slightly higher temporal resolution found for the electrical stimulation modes suggests that the temporally highly coherent electrical stimulation appears to engage, in a more effective manner, the excitatory/inhibitory mechanisms contributing to the response in AI than acoustic click stimulation with less temporal coherence. (ABSTRACT TRUNCATED)
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Marinis, Thomas F., and Joseph W. Soucy. "Implementing Inductor Function with Vibrating Capacitor Structures." Journal of Microelectronics and Electronic Packaging 11, no. 2 (April 1, 2014): 57–63. http://dx.doi.org/10.4071/imaps.409.
Full textAbstract:
One of the most common uses of inductors is in filtering electrical signals to remove oscillations over selected frequency ranges. In this application, they are combined with capacitors to build resonant circuits to either block or dissipate signals at the unwanted frequencies. Similar, but larger current capacity filters are used to eliminate oscillatory ripple voltages from DC power supply outputs. Inductors are also essential components in buck converter type power supplies in which they store energy supplied by an oscillatory source to power a circuit, which generates a constant voltage. Inductors of various constructions have proven highly successful in all of these applications, but their performance is not ideal. For one, they dissipate the energy that is stored in them via a number of mechanisms. The conductivity of the wire comprising their windings is finite, so they suffer Ohmic losses. Their magnetic fields induce eddy currents within their cores and dissipative currents in surrounding circuit elements. Inductors also exhibit parasitic capacitance between their windings, which can give rise to dielectric losses. Because of these loss mechanisms, the quality factor of an inductor, which is its time average ratio of stored to dissipated energy, is typically less than a few hundred. By contrast, mechanical resonators, fabricated from single crystal silicon, attain quality factors that are orders of magnitude higher. Hence, mechanical filters could be made with sharper roll offs and smaller bandwidths than inductor based filters. They would also be more efficient in power supply applications. Inductors are also relatively heavy components, when compared with capacitors, resistors, and integrated circuits, due to their high content of copper and iron. A mechanical oscillator could be made significantly lighter than an inductor that is capable of storing the same amount of energy. We have been investigating mechanical oscillators that use flat beams, suspended at both ends above substrates with electrode patterns that form a capacitive dive to excite oscillations in the beam. We are examining a number of configuration variables, including beam geometry, mass distribution and excitation loading. We use finite element analysis and lumped parameter models to characterize beam deflection and MatLab scripts to predict performance in electrical circuits. We are also preparing to fabricate our first design for testing.
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Marinis, Thomas F., and Joseph W. Soucy. "Implementing Inductor Function with Vibrating Capacitor Structures." International Symposium on Microelectronics 2013, no. 1 (January 1, 2013): 000354–60. http://dx.doi.org/10.4071/isom-2013-tp53.
Full textAbstract:
One of the most common uses of inductors is in filtering electrical signals to remove oscillations over selected frequency ranges. In this application, they are combined with capacitors to build resonant circuits to either block or dissipate signals at the unwanted frequencies. Similar, but larger current capacity filters are used to eliminate oscillatory ripple voltages from DC power supply outputs. Inductors are also essential components in buck converter type power supplies in which they store energy supplied by an oscillatory source to power a circuit, which generates a constant voltage. Inductors of various constructions have proven highly successful in all of these applications, but their performance is not ideal. For one, they dissipate the energy that is stored in them via a number of mechanisms. The conductivity of the wire comprising their windings is finite, so they suffer Ohmic losses. Their magnetic fields induce eddy currents within their cores and dissipative currents in surrounding circuit elements. Inductors also exhibit parasitic capacitance between their windings, which can give rise to dielectric losses. Because of these loss mechanisms, the quality factor of an inductor, which is its time average ratio of stored to dissipated energy, is typically less than a few hundred. By contrast, mechanical resonators, fabricated from single crystal silicon, attain quality factors that are orders of magnitude higher. Hence, mechanical filters could be made with sharper roll offs and smaller bandwidths than inductor based filters. They would also be more efficient in power supply applications. Inductors are also relatively heavy components, when compared to capacitors, resistors and integrated circuits, due to their high content of copper and iron. A mechanical oscillator could be made significantly lighter than an inductor that is capable of storing the same amount of energy. We have been investigating mechanical oscillators that use flat beams, suspended at both ends above substrates with electrode patterns that form a capacitive dive to excite oscillations in the beam. We are examining a number of configuration variables, including beam geometry, mass distribution and excitation loading. We use finite element analysis and lumped parameter models to characterize beam deflection and MatLab scripts to predict performance in electrical circuits. We are also preparing to fabricate our first design for testing.