Set Of Tones Research Articles

The effect of ground sensor and UAV flight path geometry on the tomographic reconstruction of a weakly sheared daytime convective planetary boundary layer

A signal analysis of the sound of a propeller-driven unmanned aerial vehicle (UAV) shows that its acoustic signature comprises a set of strong narrowband tones superimposed onto a broadband random component. If such a UAV overflies an array of microphones, the projected and observed Doppler shifts in frequency of the narrowband tones may be compared and converted into effective sound speed values: 2- and 3D spatially varying atmospheric temperature and wind velocity fields may then be estimated using tomography. The technique has practical application in a number of research fields. In this paper, we examine the influence of UAV flight path and ground sensor geometry on the feasibility and usefulness of UAV-based atmospheric tomography. Realistic conditions for a weakly sheared daytime convective atmospheric boundary layer are synthesized through use of massively parallel large eddy simulation code that utilizes pseudo-spectral differencing in horizontal planes and solves an elliptic pressure equation. Particular attention is paid to the accuracy with which the surface layer (lowest 50 m of atmosphere) may be reconstructed using UAV-based acoustic tomography as this region typically experiences the greatest spatio-temporal variation in temperature and wind speed; and arrangements of UAV flight path and sensor geometry do not permit ray paths to intersect without the UAV flying very low and disturbing the atmosphere. The influence of meteorological observations obtained onboard the UAV and by ground sensors is also examined.

Peak‐to‐average power ratio reduction of orthogonal frequency division multiplexing systems using modified tone reservation techniques

SummaryThis paper proposed a modified tone reservation (TR) technique that can reduce the peak‐to‐average power ratio (PAPR) of the orthogonal frequency division multiplexing (OFDM) system and is able to correct errors to avoid channel interference. The TR technique is a widely used PAPR reduction technique, which divides subcarriers of the OFDM system into two sets to generate peak‐canceling signals and transmit modulated data. The subcarriers used to reduce the PAPR are called the peak reduction tone sets. The mechanism of peak‐canceling signal generation is a primary factor in determining the quality of the PAPR reduction performance of the TR technique. Currently, two signal generation mechanisms exist: TR‐gradient‐based and TR‐clipping‐based techniques. Although TR techniques can effectively reduce the high PAPR in the OFDM system, TR techniques lack the ability to correct errors. Therefore, this paper combined block coded modulation codes and TR techniques to provide the modified TR techniques with error correction abilities. From the simulation results, the modified TR techniques had a superior effect on PAPR reduction performance compared with the conventional TR technique. The modified TR technique also possessed the ability to correct errors during signal transmission. Copyright © 2015 John Wiley & Sons, Ltd.

Extending the Dynamic Range of Sweep-Free Brillouin Optical Time-Domain Analyzer

Sweep-free Brillouin optical time-domain analysis (SF-BOTDA) replaces the sequential frequency scanning of classical BOTDA by parallel interrogation of the fiber-under-test using the simultaneous interaction of multiple pump tones with counter-propagating multiple probe tones. While the basic SF-BOTDA technique boosts the measurement speed by a factor equal to the number of probe tones used, its dynamic range is limited to approximately the pump tone spacing, which is of the order of 100 MHz. This paper provides an in-depth analysis of our method to significantly extend the dynamic range to the GHz regime. Based on sequential interrogation with up to three sets of multiple tones, each having a different frequency spacing, this method provides a major speed advantage over the classical BOTDA in spite of the use of three sets of tones. With this development, which does not require any additional hardware, SF-BOTDA offers distributed sensing of optical fibers over practical dynamic ranges of strain/temperature variations, with the potential to become one of the fastest sensing techniques.

Passive Intermodulation Distortion in Antennas

An analytic formulation of passive intermodulation distortion (PIM) in antennas is presented for PIM introduced by electro-thermal modulation of conductivity by current-related losses. A silver rectangular patch antenna was fabricated using a sapphire substrate isolating the thermal process from other possible sources. Two-tone testing at 990 MHz using a sweep of the tone separation from 3 Hz to 100 kHz is reported. Both transmitted and reflected PIM are characterized using a high dynamic range two-tone test system incorporating an analog canceler achieving a dynamic range of 125 dB at 1-Hz tone separation for reflection measurements, and 100 dB at 10-Hz tone separation for transmission measurements with each tone set to 32.3 dBm.

The effects of rhythm and melody on auditory stream segregation

While many studies have assessed the efficacy of similarity-based cues for auditory stream segregation, much less is known about whether and how the larger-scale structure of sound sequences support stream formation and the choice of sound organization. Two experiments investigated the effects of musical melody and rhythm on the segregation of two interleaved tone sequences. The two sets of tones fully overlapped in pitch range but differed from each other in interaural time and intensity. Unbeknownst to the listener, separately, each of the interleaved sequences was created from the notes of a different song. In different experimental conditions, the notes and/or their timing could either follow those of the songs or they could be scrambled or, in case of timing, set to be isochronous. Listeners were asked to continuously report whether they heard a single coherent sequence (integrated) or two concurrent streams (segregated). Although temporal overlap between tones from the two streams proved to be the strongest cue for stream segregation, significant effects of tonality and familiarity with the songs were also observed. These results suggest that the regular temporal patterns are utilized as cues in auditory stream segregation and that long-term memory is involved in this process.

PAPR reduction of OFDM using invasive weed optimization-based optimal peak reduction tone set selection

Abstract Tone reservation (TR) is one of the attractive techniques to reduce peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing system. As conventional TR technique requires exhaustive searching over all the combinations of the given peak reduction tone (PRT) sets, it results in computational complexity that increases exponentially with the number of the subcarriers. In this paper, we aim to obtain a desirable PAPR reduction with low computational complexity. Since the process of searching the optimal PRT set can be categorized as combinatorial optimization with some variables and constraints, we propose a novel scheme, which is based on a nonlinear optimization approach named as invasive weed optimization method, to search the optimal combination of PRT set with low complexity. To validate the analytical results, extensive simulations have been conducted, showing that the proposed schemes can achieve significant reduction in computational complexity while keeping good PAPR reduction. As results of simulations, the proposed scheme shows almost the same PAPR reduction performance as compared with the genetic algorithm-based TR method which has been known to have the best performance and obtains near-optimal PRT sets.

A Nearly Optimal Peak Reduction Tone Set Selection Algorithm

In tone reservation-based OFDM systems, the peak to average power ratio (PAPR) reduction performance mainly depends on the selection of peak reduction tone (PRT) set. it is known that finding the optimal PRT set requires an exhaustive search of all combination of possible PRT sets, and this search is infeasible for the number of tones used in practical systems. The existing selection methods perform poorly or incur high computational complexity. In this paper, an efficient scheme based on particle swarm optimization algorithm (PSO) is proposed to search the nearly optimal PRT set.Simulation results show that our proposed algorithm can obtain a nearly optimal PRT set and good PAPR reductions.

Inter-rater agreement on Mandarin tone categorization: Contributing factors and implications

Factors that may/may not influence inter-rater reliability in assessing the accuracy of monosyllabic Mandarin tones produced by children and adults were examined in three experiments. Experiment 1 investigated inter-judge reliability in two groups of Mandarin-speaking adults—one group from China and the other from Taiwan—on their categorization of filtered tones produced by adults and children. The results showed that the magnitude of inter-rater agreement was associated with the production accuracy of the speakers; the judges attained lower agreement in categorizing children’s tones than adults’ tones. All judges who indicated that Mandarin was their strongest language and that they had learned and used Mandarin since birth performed similarly in their tone categorization despite the fact that they came from and were residing in different countries. Similar results was found in experiment 2, in which one group of the judges in experiment 1 categorized tones produced by a new and larger group of adults and children, and in experiment 3, in which a different group of adults categorized another new set of tones produced by a different group of speakers. Implications of the findings in research design will be discussed. [Work supported by NIH-NIDCD (1 F31 DC008479-01A1) and NSF (OISE-0611641).]

Genetic Algorithm Based Nearly Optimal Peak Reduction Tone Set Selection for Adaptive Amplitude Clipping PAPR Reduction

In tone reservation (TR) based OFDM systems, the peak to average power ratio (PAPR) reduction performance mainly depends on the selection of the peak reduction tone (PRT) set and the optimal target clipping level. Finding the optimal PRT set requires an exhaustive search of all combinations of possible PRT sets, which is a nondeterministic polynomial-time (NP-hard) problem, and this search is infeasible for the number of tones used in practical systems. The existing selection methods, such as the consecutive PRT set, equally spaced PRT set and random PRT set, perform poorly compared to the optimal PRT set or incur high computational complexity. In this paper, an efficient scheme based on genetic algorithm (GA) with lower computational complexity is proposed for searching a nearly optimal PRT set. While TR-based clipping is simple and attractive for practical implementation, determining the optimal target clipping level is difficult. To overcome this problem, we propose an adaptive clipping control algorithm. Simulation results show that our proposed algorithms efficiently obtain a nearly optimal PRT set and good PAPR reductions.

Evidence of Doppler-shifted Bragg scattering in the vertical plane by ocean surface waves

A set of narrowband tones (280, 370, 535, and 695 Hz) were transmitted by an acoustic source mounted on the ocean floor in 10 m deep water and received by a 64-element hydrophone line array lying on the ocean bottom 1.25 km away. Beamformer output in the vertical plane for the received acoustic tones shows evidence of Doppler-shifted Bragg scattering of the transmitted acoustic signals by the ocean surface waves. The received, scattered signals show dependence on the ocean surface wave frequencies and wavenumber vectors, as well as on acoustic frequencies and acoustic mode wavenumbers. Sidebands in the beamformer output are offset in frequency by amounts corresponding to ocean surface wave frequencies. Deviations in vertical arrival angle from specular reflection agree with those predicted by the Bragg condition through first-order perturbation theory using measured directional surface wave spectra and acoustic modes measured by the horizontal hydrophone array.

Doubly Selective Underwater Acoustic Channel Model for a Moving Transmitter/Receiver

We propose a new method of modeling the signal transmission in underwater acoustic communications when the transmitter and receiver are moving. The motion-induced channel time variations can be modeled by sampling the transmitter/receiver trajectory at the signal sampling rate and calculating, for each position, the channel impulse response from the acoustic-field computation. This approach, however, would result in high complexity. To reduce the complexity, the channel impulse response is calculated for fewer (waymark ) positions and then interpolated by local splines to recover it at the signal sampling rate. To allow higher distances between waymarks and, thus, further reduction in the complexity, the multipath delays are appropriately adjusted before the interpolation. Because, for every time instant, this method only requires local information from the trajectory, the impulse response can recursively be computed, and therefore, the signal transmission can be modeled for arbitrarily long trajectories. An approach for setting the waymark sampling interval is suggested and investigated. The proposed method is verified by comparing the simulated data with data from real ocean experiments. For a low-frequency shallow-water experiment with a moving source that transmits a tone set, we show that the Doppler spectrum of the received tones is similar in the simulation and experiment. For a higher frequency deep-water experiment with a fast-moving source that transmits orthogonal frequency-division multiplexing (OFDM) communication signals, we investigate the detection performance of a receiver and show that it is similar in the simulation and experiment.

PAPR reduction scheme with selective tone reservation for OFDM signals

SUMMARYIn this paper, we propose a peak‐to‐average power ratio (PAPR) reduction scheme with selective tone reservation. In this scheme, the preset peak reduction tone (PRT) set would be divided into M PRT subsets that can generate M time‐domain kernels. The differences of the slopes for the phase responses of the M time‐domain kernels would be considered to design the M PRT subsets in reducing the PAPR of the OFDM transmitted signal. In addition, we can further enhance the PAPR reduction performance by interactively selecting the most appropriate one among the M time‐domain kernels for each OFDM symbol. Simulation results show that the proposed scheme can achieve better PAPR reduction performance than the conventional tone reservation scheme with the same preset PRT set. In comparison with the conventional tone reservation scheme, our PAPR reduction scheme need not send any side information and increase a little bit hardware complexity to improve the PAPR reduction performance. Copyright © 2012 John Wiley & Sons, Ltd.

Carrier phase synchronisation scheme for very long baseline coherent arrays

Proposed is a new carrier phase synchronisation scheme used to provide a stable phase reference to a very distant station. Channel induced phase fluctuations are characterised and compensated for with a round-trip loop in which three different frequency tones are simultaneously used. The bandwidth required to allocate this set of tones is independent of carrier frequency.

Multidimensional Scaling of Musical Time Estimations

The aim of this study was to identify the psycho-musical factors that govern time evaluation in Western music from baroque, classic, romantic, and modern repertoires. The excerpts were previously found to represent variability in musical properties and to induce four main categories of emotions. 48 participants (musicians and nonmusicians) freely listened to 16 musical excerpts (lasting 20 sec. each) and grouped those that seemed to have the same duration. Then, participants associated each group of excerpts to one of a set of sine wave tones varying in duration from 16 to 24 sec. Multidimensional scaling analysis generated a two-dimensional solution for these time judgments. Musical excerpts with high arousal produced an overestimation of time, and affective valence had little influence on time perception. The duration was also overestimated when tempo and loudness were higher, and to a lesser extent, timbre density. In contrast, musical tension had little influence.

Shallow water narrowband coherence measurements in the Florida Strait

A set of measures of coherence are defined and applied to the CALOPS experiment, conducted off the coast of Florida in the summer of 2007. A set of narrowband CW tones were transmitted from a towed source received on a 118-element bottom mounted horizontal line array (206 m aperture) with broadside oriented along the 250 m isobath. Two coherence measures are based upon the eigenvalue spread: the power factor and the eigenvalue ratio. This approach is not sensitive to array element error or model mismatch. Two measures are based upon phase residuals; these include the rms-phase error and the coherence function. Three measures are based upon power responses: beam width, array signal gain degradation, and array gain. These approaches have varying sensitivity to array location errors, model mismatch, signal-to-noise ratio, and the structure of the noise field. A Gaussian noise model is used to infer a coherence length from most of the coherence measures. The primary result is that coherence lengths increase with frequency and are on the order of 200 m, the length of the array. The frequency increased coherence length with frequency goes against conventional wisdom, which is to define the coherence length as a fixed number of wavelengths.

Carrier Frequency Offset Tracking in the IEEE 802.16e OFDMA Uplink

The IEEE 802.16e standard for nomadic wireless metropolitan area networks adopts orthogonal frequency-division multiple-access (OFDMA) as an air interface. In these systems, residual carrier frequency offsets (CFOs) between the uplink signals and the base station local oscillator give rise to interchannel interference (ICI) as well as multiple access interference (MAI). Accurate CFO estimation and compensation is thus necessary to avoid a serious degradation of the error-rate performance. In this work, we address the problem of CFO tracking in the IEEE 802.16e uplink and present a closed-loop solution based on the least-squares (LS) principle. In doing so, we exploit a set of pilot tones that are available in each user's subchannel. The resulting scheme can be implemented with affordable complexity and is able to reliably track the CFOs of all active users. When used in conjunction with a frequency offset compensator, it can effectively mitigate ICI and MAI, thereby allowing channel equalization and data detection to follow directly. Numerical simulations are used to demonstrate the effectiveness of the proposed solution in the presence of residual time-varying frequency offsets.

Tone Reservation Using Near-Optimal Peak Reduction Tone Set Selection Algorithm for PAPR Reduction in OFDM Systems

This letter considers selection of the optimal peak reduction tone (PRT) set for the tone reservation (TR) scheme to reduce the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal. In the TR scheme, PAPR reduction performance achieved by a randomly generated PRT set is superior to that by a consecutive PRT set and that achieved by an interleaved tone set. However, the optimal PRT set requires an exhaustive search of all combinations of possible PRT sets, which is known to be a nondeterministic polynomial-time (NP)-hard and cannot be solved for the practical number of tones. Inspired by the efficiency of the cross-entropy (CE) method for finding near-optimal solutions in huge search spaces, this letter proposes the application of the CE method to search the optimal PRT set. Computer simulation results show that the proposed CE method obtains near-optimal PRT sets and provides better PAPR performance.

Hippocampus responds to auditory change in rabbits

Any change or novelty in the auditory environment is potentially important for survival. The cortex has been implicated in the detection of auditory change whereas the hippocampus has been associated with the detection of auditory novelty. Local field potentials (LFPs) were recorded from the CA1 area of the hippocampus in waking rabbits. In the oddball condition, a rare tone of one frequency (deviant) randomly replaced a repeated tone of another frequency (standard). In the equal-probability condition, the standard was replaced by a set of tones of nine different frequencies in order to remove the repetitive auditory background of the deviant (now labelled as control-deviant) while preserving its temporal probability. In the oddball condition, evoked potentials at 36–80 ms post-stimulus were found to have greater amplitude towards negative polarity for the deviant relative to the standard. No significant differences in response amplitudes were observed between the control-deviant and the standard. These findings suggest that the hippocampus plays a role in auditory change detection.

Multi-Stage TR Scheme for PAPR Reduction in OFDM Signals

In the tone reservation (TR) scheme of the orthogonal frequency division multiplexing (OFDM) systems, there exists a trade-off between the peak to average power ratio (PAPR) reduction performance and the peak reduction tone (PRT) set size. In this paper, we propose a multi-stage TR scheme for PAPR reduction, which adaptively selects one of several PRT sets according to the PAPR of OFDM signal while the PRT set is fixed for the conventional TR scheme. It is shown that the PAPR reduction performance of the proposed scheme is better than that of the conventional TR scheme when the tone reservation rate (TRR) is the same.

Flow‐induced remodeling: interplay of local inflammation and vascular tone

We hypothesize that small artery remodeling is facilitated by inflammation but that smooth muscle cell tone sets its inward or outward direction.MethodsMouse mesenteric arcade arteries were ligated, resulting in low flow and high flow vessels. Immediate effects on tone were determined by in vivo microscopy. Structural remodeling was quantified after two days.ResultsVessels exposed to high blood flow dilated, followed by outward remodeling. Low flow vessels constricted, followed by inward remodeling. Macrophage numbers increased 5‐fold in both groups, and remodeling was absent after macrophages depletion. Yet, the pattern of pro‐ and anti‐inflammatory cytokine expression was similar in high and low flow vessels. Low flow vessels under subsequent full dilation showed increased outward remodeling, as tested by a sequence of 1 day in vivo and 1 day in vitro study in a cannulation setup (13 ± 3% in inflamed arteries versus 6 ± 1% in control, n=5, p<0.05).ConclusionAltered blood flow is associated with an inflammatory response that facilitates remodeling; the direction is determined by vascular tone. Supported by the Netherlands Heart Foundation (NHS 2001T038).