A robust sequential hypothesis testing method for brake squeal localisation

This contribution deals with the in situ detection and localisation of brake squeal in an automobile. As brake squeal is emitted from regions known a priori, i.e., near the wheels, the localisation is treated as a hypothesis testing problem. Distributed microphone arrays, situated under the automobile, are used to capture the directional properties of the sound field generated by a squealing brake. The spatial characteristics of the sampled sound field is then used to formulate the hypothesis tests. However, in contrast to standard hypothesis testing approaches of this kind, the propagation environment is complex and time-varying. Coupled with inaccuracies in the knowledge of the sensor and source positions as well as sensor gain mismatches, modelling the sound field is difficult and standard approaches fail in this case. A previously proposed approach implicitly tried to account for such incomplete system knowledge and was based on ad hoc likelihood formulations. The current paper builds upon this approach and proposes a second approach, based on more solid theoretical foundations, that can systematically account for the model uncertainties. Results from tests in a real setting show that the proposed approach is more consistent than the prior state-of-the-art. In both approaches, the tasks of detection and localisation are decoupled for complexity reasons. The localisation (hypothesis testing) is subject to a prior detection of brake squeal and identification of the squeal frequencies. The approaches used for the detection and identification of squeal frequencies are also presented. The paper, further, briefly addresses some practical issues related to array design and placement. (C) 2019 Author(s)

An Investigation into the Radial Velocity Variations of CoRoT-7

CoRoT-7b, the first transiting ``superearth'' exoplanet, has a radius of 1.7 R_Earth and a mass of 4.8 M_Earth. Ground-based radial velocity measurements also detected an additional companion with a period of 3.7 days (CoRoT-7c) and a mass of 8.4 M_Earth. The mass of CoRoT-7b is a crucial parameter for planet structure models, but is difficult to determine because CoRoT-7 is a modestly active star and there is at least one additional companion. A Fourier analysis was performed on spectral data for CoRoT-7 taken with the HARPS spectrograph. These data include RV measurements, spectral line bisectors, the full width at half maximum of the cross-correlation function, and Ca II emission. The latter 3 quantities vary due to stellar activity and were used to assess the nature of the observed RV variations. An analysis of a sub-set of the RV measurements where multiple observations were made per night was also used to estimate the RV amplitude from CoRoT-7b that was less sensitive to activity variations. Our analysis indicates that the 0.85-d and 3.7-d RV signals of CoRoT-7b and CoRoT-7c are present in the spectral data with a high degree of statistical significance. We also find evidence for another significant RV signal at 9 days. An analysis of the activity indicator data reveals that this 9-d signal most likely does not arise from activity, but possibly from an additional companion. If due to a planetary companion the mass is m = 19.5 M_Earth, assuming co-planarity with CoRoT-7b. A dynamical study of the three planet system shows that it is stable over several hundred millions of years. Our analysis yields a RV amplitude of 5.04 +/- 1.09 m/s for CoRoT-7b which corresponds to a planet mass of m = 6.9 +/- 1.4 M_Earth. This increased mass would make the planet CoRoT-7b more Earth-like in its internal structure.Comment: 20 pages, 20 figure

Hybrid receiver study

The results are presented of a 4 month study to design a hybrid analog/digital receiver for outer planet mission probe communication links. The scope of this study includes functional design of the receiver; comparisons between analog and digital processing; hardware tradeoffs for key components including frequency generators, A/D converters, and digital processors; development and simulation of the processing algorithms for acquisition, tracking, and demodulation; and detailed design of the receiver in order to determine its size, weight, power, reliability, and radiation hardness. In addition, an evaluation was made of the receiver's capabilities to perform accurate measurement of signal strength and frequency for radio science missions

Amplitude and frequency-modulated stimuli activate common regions of human auditory cortex

Hall et al. (Hall et al., 2002, Cerebral Cortex 12:140–149) recently showed that pulsed frequency-modulated tones generate considerably higher activation than their unmodulated counterparts in non-primary auditory regions immediately posterior and lateral to Heschl’s gyrus (HG). Here, we use fMRI to explore the type of modulation necessary to evoke such differential activation. Carrier signals were a single tone and a harmonic-complex tone, with a 300 Hz fundamental, that were modulated at a rate of 5 Hz either in frequency, or in amplitude, to create six stimulus conditions (unmodulated, FM, AM). Relative to the silent baseline, the modulated tones, in particular, activated widespread regions of the auditory cortex bilaterally along the supra-temporal plane. When compared with the unmodulated tones, both AM and FM tones generated significantly greater activation in lateral HG and the planum temporale, replicating the previous findings. These activation patterns were largely overlapping, indicating a common sensitivity to both AM and FM. Direct comparisons between AM and FM revealed a higher magnitude of activation in response to the variation in amplitude than in frequency, plus a small part of the posterolateral region in the right hemisphere whose response was specifically AM-, and not FM-, dependent. The dominant pattern of activation was that of co-localized activation by AM and FM, which is consistent with a common neural code for AM and FM within these brain regions

Spectral imaging in preclinical research and clinical pathology.

Spectral imaging methods are attracting increased interest from researchers and practitioners in basic science, pre-clinical and clinical arenas. A combination of better labeling reagents and better optics creates opportunities to detect and measure multiple parameters at the molecular and cellular level. These tools can provide valuable insights into the basic mechanisms of life, and yield diagnostic and prognostic information for clinical applications. There are many multispectral technologies available, each with its own advantages and limitations. This chapter will present an overview of the rationale for spectral imaging, and discuss the hardware, software and sample labeling strategies that can optimize its usefulness in clinical settings

Flight techniques for the measurement of stability derivatives and aircraft response

A method of obtaining aircraft frequency-response from transient response data by Fourier analysis is currently being investigated. This report describes progress that has been made between the commencement of the contract (1st December, 1964) and the time of writing (October, 1965). The dynamic response characteristics of a Hawker Siddeley Dore' aircraft are being determined from flight measurements using the Fourier method of analysis. At present attention is centred on the longitudinal response as the short-period mode of the aircraft is well damped and should be defined by a simple transfer function. The aircraft transient responses to various pilot-applied control inputs are recorded and the Fourier analysis of these transients is being carried out on a Ferranti Pegasus digital computer. Three development flights have been completed to date, and some preliminary results have been obtained, although the detailed analysis of the flight data is awaiting the incorporation of the instrumentation calibration into the computer programme. This last procedure will speed up the analysis of future data

Radio-frequency Bloch-transistor electrometer

A quantum-limited electrometer based on charge modulation of the Josephson supercurrent in the Bloch transistor inserted into a superconducting ring is proposed. As this ring is inductive coupled to a high-Q resonance tank circuit, the variations of the charge on the transistor island (input signal) are converted into variations of amplitude and phase of radio-frequency oscillations in the tank. These variations are amplified and then detected. The output noise, the back-action fluctuations and their cross-correlation are computed. It is shown that our device enables measurements of the charge with a sensitivity which is determined by the energy resolution of its amplifier, that can be reduced down to the standard quantum limit of \hbar/2. On the basis of this setup a "back-action-evading" scheme of the charge measurements is proposed.Comment: 5 pages incl. 2 figure