Closed-loop autocorrelator and its application to frequency discrimination

A new closed-loop autocorrelation system is proposed in the paper. It is based on a conventional autocorrelator; however, the fixed delay is replaced by a variable delay line and the autocorrelator output is fed back to control the delay. The variable delay can be realised by a SAW voltage-controlled variable delay line (VCDL). Adetailed analysis of the loop is given. It is shown that for some special inputs, the loop performs as a frequency-measuring system, as an instantaneous frequency measurement (IFM) or as a wideband linear FM discriminator. It is further shown that, in the presence of noise, the loop behaves similarly to a frequency modulation feedback (FMFB) loop. Therefore, the output SNR can be improved (in comparison with conventional FM discriminators) by appropriately choosing the loop parameters. Experimental results of a system implemented using an SAW VCDL are presented and are shown to support the analysis.

An investigation is presented of insertion loss and constant variable delays in electronically variable magnetostatic-volume-wave delay lines. The delay line has a conductor-dielectric-YIG-dielectric-conductor structure. Variable delays up to 300 MHz bandwidth have been obtained in a single volume-wave delay line by adjusting the direction and magnitude of the biasing DC magnetic field in a plane containing the normal to the YIG film and the direction of wave propagation. Insertion loss as a function of frequency has been obtained for different biasing field angles and also for the angles corresponding to variable constant delays. Good agreement between theoretically obtained insertion loss and experimental results is found. Electronically variable magnetostatic-wave delay lines have promising applications in broadband phased-array antennas at 1-20 GHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Persistence is the most important property in any hydrologic design concerning the storage capacity of reservoirs, average return periods, failure risks, and drought properties. Its consideration in analytical derivations of design criteria presents difficulties, especially in autocorrelated hydrologic processes, and for this reason, most often the analytical expressions are obtained on the basis of non-persistent (independent) cases. Although the conventional autocorrelation coefficients and function are used in many hydrological design problems, the very definition of the autocorrelation function requires that the underlying hydrologic process generating mechanism abide with normal (Gaussian) probability distribution function in addition to other restrictive assumptions. Since almost all of the analytical stochastic approaches are based on the normality assumption, it is necessary to transform non-Gaussian distributions to the normal distribution to use analytical expressions. During the transformation process, the very genuine persistence property of the basic hydrologic variables is not preserved, even when the statistical parameters such as the average, standard deviation, skewness coefficient, kurtosis, etc., are maintained in the transformed data. This shortcoming in the autocorrelation function is by-passed by the introduction and use of an autorun function, which is probability distribution free and a robust parameter. Its basis is the conditional probability statement which does not require any assumptions in practical applications. Various practical and simple hydrological design quantities are developed on the basis of the autorun coefficients without considering the conventional autocorrelation structure. The application of methodology is presented for John’s river in Florida.

A WiMedia ultrawideband (UWB) frequency synthesizer is designed for band group #1. A very fast hopping is achieved by using a delay-locked loop (DLL) architecture which utilizes a novel variable gain voltage-controlled delay line (VCDL) scheme to compensate the phase error generated at the hopping instant. Fast-settling DLL allows an injection-locked oscillator (ILO) to be employed to reduce the current consumption in the edge combiner (EC). Simulated in STM 65-nm CMOS technology, synthesizer hopping time is less than two reference cycles. Phase noise at 3432 MHz is -124 dBc/Hz at 1 MHz offset. The adjacent spur level from the Monte Carlo simulation is -34 dBc. Excluding CML divider, the synthesizer draws 6.7 mW from a 1.2 V supply.

Within the past five years acoustic imaging systems based on the use of arrays of transducer elements rather than a single element have undergone a rapid stage of development. Primary performance objectives of these systems in medical applications include high resolution, large field of view, long range and rapid frame rate. Various approaches to array systems can be classified according to transducer geometry, scanning technique and method of focus. Analysis of the salient electronic device and circuit requirements of these systems indicates well matched circuit arrays of 1) high voltage transmitters, 2) low noise, wide dynamic range preamplifiers and logarithmic compressors, 3) high voltage multiplex switches and 4) electronically variable analog delay lines are needed, with variable delay lines representing perhaps the most acute requirement. Custom silicon monolithic integrated circuits offer a promising means for fulfilling these needs, particularly in the case of charge coupled device (CCD) delay lines. Array imaging systems offer promise of extraordinary future progress.

Anticipation of events such as, changes in traffic light signals and preparing to brake or accelerate are critical behaviors during driving. Smart vehicles, equipped with on-board Brain-Computer Interface (BCI), could decode the driver's intention to perform an action from his brain activity, thus enriching the interaction with its driver. To this end, the contribution of this thesis are three fold: (i) it presents 3 experiments to investigate anticipatory behavior from Electroencephalogram (EEG), while driving: count-down paradigm, traffic light changes in a virtual city and on a real road, (ii) it proposes methods for synchronous single-trial EEG classification of this behavior as well as asynchronous detection of movement intention, (iii) it explores new filtering techniques toward online application. In the first part, we present our first experiment, inspired from the classical Contingent Negative Variation (CNV) paradigm, where a count-down of numbers predicted the appearance of a cue that instructed to brake or accelerate accordingly. Through the EEG data (N=18), we show the presence of anticipatory potentials locked to the stimuli onset, which are similar to the well-known central negative Slow Cortical Potentials (SCPs). We further demonstrate the discrimination between cases requiring an action (brake/accelerate) upon an imperative subsequent stimulus (`Start'/`Stop' cues) vs. the events that do not require such action (count-down cues). We also show the possibility of detecting driver's movement intention through these potentials. In the second part, we extend the study to a more realistic scenarios using traffic lights through next two experiments. For the second experiment, we recorded 10 subjects over 3 days in a car simulator. During the second and third day, the subjects received online classification feedback together with reaction time after braking. Through this data, we confirm the presence of the anticipatory SCPs in response to the traffic lights as well as offline single trial performances with similar patterns to those of the first experiment. Interestingly, for the brake trials, we observed an improvement in the anticipatory behavior, which is likely due to the feedback provision. In the real car experiment on a closed road, we recorded EEG (N=8) over 2 days. Remarkably, we confirmed the existence of the anticipatory SCPs and demonstrated the possibility of detecting these potentials, despite large amounts of driving related visual distractions and movement artifacts. Thirdly, we report a post-hoc analysis on investigating the influence of filtering on the SCP detection performance. We present a new spectral filtering method, called Predictive Cascade Filter (PCF), which theoretically reduced the group delay associated with filtering of low frequency bands. The grand averages illustrate this reduction, whereas the classification performance did not improve by using the PCF filters. Indeed, the lowpass PCF as well as the usual lowpass filter appeared to be the best when applied causally (pertinent to online application), whereas the bandpass filter performed best, when applied non-causally (pertinent to offline analysis). We believe, the contributions presented in this thesis can impact the advancement of neuro-technology into smart vehicles as well as other applications such as neuro-rehabilitation.

A method was investigated to reduce the insertion loss and response time in the phase shift in a microwave variable delay line using liquid crystal (LC). In variable delay lines using conventional nematic LC, reducing the insertion loss conflicts with reducing the phase-shift response-time dependence on the thickness of the LC layer; thus, it is very difficult to simultaneously satisfy both requirements. Here, the use of dual-frequency switching-mode liquid crystal (DFSM LC) for the variable delay line is demonstrated as one approach to solving this problem. By using the characteristics of DFSM LC, in that the alignment of the LC can be controlled with a control voltage and its frequency, it becomes possible to control the LC alignment to be in an always electrically driven condition by applying a combination of control voltages of dc and several kilohertz. Experimental results of a microwave variable delay line using DFSM LC show that it is possible to reduce both the phase-shift response time and insertion loss.

The empirical Green’s function (EGF) which approximately corresponds to an impulse response can simply be retrieved from cross-correlation functions of seismic noises between two receivers in the assumption of diffusive wave field. It will increase much more available data than the traditional seismology underlying the view point that the noise is either source or receiver and is known as Passive Imaging Interferometry. In the study, we measure relative velocity variations from the coda part of recovered EGF, observe the temporal evolution, and have discussion on possible mechanisms leading to the changes of physical properties in the crust. The 2006 Mw6.1 Taitung earthquake occurred in the southern Longitudinal Valley and the collision suture zone between the Eurasian plate and the Philippine Sea plate and caused significant coseismic deformation. To detect potential variations in subsurface seismic velocities associated with internal strain change before and after the quake, we construct the GF from auto-correlation function (ACF) and cross-correlation function (CCF) from one-day long seismic noise after normalization. The stacking is applied to produce the long-term GF (Reference GF, RGF) and short-term GF (Current GF, CGF), respectively, for enhancing the coherent phases in EGFs. We use both stretch and moving-window cross-spectrum analysis to detect the relative time shifts of the late-arriving coda waves between CGF and RGF. A sudden drop in relative velocity perturbations is observed in the high –frequency (2-8 Hz) ACFs for the station about 7 km south of the epicenter where the two perpendicular faults may intersect and result in locally maximum coseismic slip deformation and widely-distributed aftershocks. The sustained damage in the regions of fault junction and slip concentration probably cause such a significant velocity disturbance. The CCFs (0.1-0.9 Hz) between pairs of stations also show moderate velocity decrease for the shorter interstation paths traversing the south and southeast of the epicenter, the area subject to the static volumetric strain with coseismic dilatational deformation. Plus, the post-seismic estimation (after October) increase to the pre-seismic value (before April), which shows positive relations between the regional precipitation.

The purpose of this work was to use a nondestructive method for detecting the brownheart of Korla pear to reduce the chance of infection among pears without brownheart. A mechanical impulse method based on vibration testing system was used to excite the fruits. The consistent acquisition signal indicated that the test is repeatable at the same positions of fruit equator (cheek). A remarkable frequency signal was excited at 9-12 N force by a rubber tipped hammer. The dominant frequency was identified at the maximum response magnitude to assess the internal defect, and the result was not influenced by the distances between the defect borders and the excitation points. The sharp increase of defect mass could significantly affect the dominant frequency. Relationship between the dominant response frequency (fd) and the defect mass percentage (ω) was characterized by an equation fd =410.649e-0.0833ω+261.947 with a good correlation coefficient (R2=0.925). A defect mass of 2.281% was determined as a discrimination threshold. Once the threshold exceeded 2.281%, the defective pear could be classified with a high accuracy rate of 96.7%. This finding would provide guidance for determining the optimal detecting time to the brownheart of Korla pears, according to the specific storage conditions when the vibration frequency spectrum method is deployed. Keywords: nondestructive detection, vibration frequency spectrum, brownheart of Korla pear, internal defect, fruit quality DOI: 10.3965/j.ijabe.20171002.1910 Citation: Xu H B, Wu J, Wang Z P, Gao Y M, Wang Z P, Zhao Z Q. Discrimination of brownheart of Korla pear using vibration frequency spectrum technique. Int J Agric & Biol Eng, 2017; 10(2): 259–266.

Breathing rate (BR) is an important physiological indicator that gives information about a variety of chronic diseases. As direct measurements of respiratory devices are uncomfortable for patients, our objective is to obtain an accurate estimation of BR using only PPG signals. To this end, three respiratory modulations are derived from the PPG signals based on amplitude, frequency and baseline wander modulations. These derived modulations are however highly dependent on patient and activity, it is thus difficult to determine the optimal modulation. Therefore, respiratory quality indices (RQI) are introduced to assess the quality of the derived modulations before estimation of BR. These RQIs are based on a set of features (maximum power in the frequency range) extracted from Fourier Transform, autocorrelation and sinusoidal model under the hypothesis that the respiration is a quasi-periodic signal. The selection of the best derived modulations is performed automatically by comparing the RQI scores. This method is compared to other methods in the literature (Pimentel 2016 [1], Karlen2013 [2], Flemming2007 [3], Shelly2006 [4]) using the Capnobase Benchmark dataset. Absolute errors are calculated as the difference between the estimated BR and those derived from the capnometry waveform as a gold standard. For window segments of 32 seconds, Karlen [2]'s method (best reference method) gave a median absolute error (MAE) of 1.2bpm and a 25–75 percentile range in [0.5-3.4] bpm, while our method achieves an MAE of 0.8bpm and a 25- 75 percentile range in [0-4.5]bpm. These results show that the automatic selection using RQI scores is an efficient method for indirect BR estimations based on noisy PPG modulations.

Objective To verify the feasibility of discriminating tissue types in the anterior approach of the cervical spine by the Electrical impedance (EI) and decrease the rate of severe complications. Methods Six New Zealand white rabbits and 6 mini-pigs were performed standard anterior cervical surgery. The esophagus, carotid artery, tracheal cartilage, annular liga-ments of trachea, longus colli muscle and anterior longitudinal ligament are classified as the prevertebral group; The cortical bone, cancellous bone, anulus fibrosus and nucleus pulposus are classified as the vertebral group. Once all the tissues were exposed com-pletely, over the frequency range of 200-3 000 kHz (the frequency points were 200 kHz, 400 kHz, 600 kHz, 800 kHz, 1 000 kHz, 2 000 kHz, 3 000 kHz), the in vivo EI of prevertebral group and vertebral group were measured by a probe and a precision induc-tance-capacitance-resistance (LCR) meter; then the data were analyzed with IBM SPSS Statistics 22 software. At every frequency, Kruskal-Wallis test followed by all pairwise multiple comparisons was applied for all the four groups (the prevertebral group of rab-bits, the vertebral group of rabbits, the prevertebral group of mini-pigs, and the vertebral group of mini-pigs), respectively. P val-ues < 0.05 were considered statistically significant. Results At every frequency, the results of Kruskal-Wallis test for all the four groups were significant, and the results of multiple comparisons were as follows. (1) In both miniature experimental ani-mals and large experimental animals, the EI of the vertebral group tissues was significantly different at every investigated fre-quency (multiple comparisons). (2) In the miniature experimental animals, the EI between longus colli muscle and esophagus, carotid artery and annular ligaments of trachea, and tracheal cartilage and anterior longitudinal ligament had no significant dif-ference at any frequency (multiple comparisons); significant difference could not be detected in the EI between anterior longi-tudinal ligament and annular ligaments of trachea at the frequencies of 2000-3 000 kHz (multiple comparisonsk) and could be detected at the frequencies of 200-1 000 kHz (multiple comparisons); for comparison of all other paired tissues of prevertebral group there were significant differences at all frequencies (multiple comparisonsk). (3) In the large experimental animals, the EI between longus colli muscle and esophagus, carotid artery and annular ligaments of trachea, and tracheal cartilage and ante-rior longitudinal ligament had no significant difference at any frequency (multiple comparisons), the same was true for the EI between annular ligaments of trachea and esophagus, carotid artery and anterior longitudinal ligament, and longus colli muscle and annular ligaments of trachea at the frequencies of 800-3 000 kHz, 3 000 kHz and 3 000 kHz (multiple comparisons), re-spectively; for comparison of all other paired tissues of prevertebral group there were significant differences at all frequencies (multiple comparisons). Conclusion At certain frequencies, the EI among tissues was significantly different and could discrimi-nate tissues in the anterior approach of the cervical spine. Key words: Cervical vertebrae; Spinal fusion; Electric impedance; Animal experimentation

This paper outlines the most recent frequency and signal structure of COMPASS system. It then shows various power spectral density and autocorrelation function of B1, B2 and B3 signals, and summarizes the motivations in using BOC modulation after detailed analysis.

Improvement of vertical resolution in seismic data is one of the major challenges for the seismic reflection method. The main problem is related to the larger loss of high frequencies relative to the lower ones during seismic wave propagation. As a consequence, the contribution of lower frequencies in the final section is significantly greater than the corresponding one due to higher frequencies. In principle, this situation should not constitute an obstacle to the full recovery of the spectrum, because of the powerful tools available in seismic processing, designed to equalize all frequencies that are present in the data volume. The main reason why these tools in general do not succeed is the presence of noise, for example random noise. Such situation gives rise to a critical frequency, such that all frequencies above it are impossible to recover and, as a consequence, the seismic pulse cannot be made short enough to allow for optimal resolution. Methods to solve the problem by means of random noise attenuation have been extensively investigated and tested without relevant results. The alternative to such techniques is the enhancement of the multiplicity that can be used for stacking. Since the amplitude decays exponentially with frequency, a large multiplicity is necessary in order to attain a significant effective frequency gain. The capability to attain extremely large multiplicity is exactly the main virtue of the Common Reflection Surface (CRS) method. In this paper, we propose the strategy of combining the CRS method with the spectral whitening, a known frequency-recovery technique, so as to optimize vertical resolution in seismic data and, as a consequence, improve the discrimination of thin reservoirs. First tests on synthetic and real data shown in this work are very encouraging and permit to conclude that the proposed approach has a good potential for practical application.

The interpretation of electrochemical noise (EN) data has long been under discussion. Throughout the years, many data analysis techniques have been proposed for this purpose. As a starting point, procedures and parameters that enable identification of, or discrimination between, general and localized corrosion processes through EN are critically discussed. It is important to consider which type of information is required for a specific application. EN can be used to determine the barrier properties of a protective coating, and can therefore provide quantitative information about corrosion processes, although its most interesting ability is to provide information on corrosion characteristics. EN signals consist of a direct current (DC) component, or trend, with superimposed fluctuations. In electrochemical potential noise (EPN), this DC component represents the open corrosion potential (OCP) of the system under study. In electrochemical current noise (ECN), the DC component can e.g. be generated by electrode asymmetry. Any DC drift should be carefully removed prior to further data analysis. A procedure is introduced to accurately define the DC drift in EN signals using either of two time-frequency data analysis techniques: discrete wavelet transform (DWT) or empirical mode decomposition (EMD). Consistent and reliable information can be obtained from EN data when a data analysis procedure is selected that on the one hand has a high discrimination ability and on the other hand yields a descriptive parameter that is directly associated to the underlying physico- chemical process. Preferably, the information is obtained without the need for subjective a-priori limitations or assumptions concerning the nature of the process under investigation. These requirements are met by the Hilbert-Huang transform, which is based on the EMD. The result is a Hilbert spectrum in which local frequency information, so-called instantaneous frequencies, of EN signals, is visualized. The use of Hilbert spectra for the characterization of EN data in corrosion studies is introduced, based on the (general and localized) corrosion characteristics of carbon steel and stainless steel AISI304. A highly detailed decomposition of the original ECN and EPN data is provided in time and frequency simultaneously. This allows distinguishing between different corrosion characteristics based on their EN signals. Hilbert spectra also provide the possibility to analyze only transients present in the EN signals that originate from localized corrosion processes on AISI304. Initial identification of transients is based on the transient shape. Analysis of instantaneous frequency information present in these transients enables improved differentiation between corrosion characteristics as compared to data analysis using Hilbert spectra or energy distribution plots (determined from DWT) without transient analysis. The applicability of transient analysis through Hilbert spectra of ECN signals is further investigated for Ce-based inhibition of aluminium alloy AA2024-T3 and for detection and identification of microbiologically influenced corrosion (MIC). Transient analysis allows detection of changes in corrosion characteristics, i.e. the evolution of corrosion inhibition of AA2024-T3 by Ce-ions, with time. The initial procedure of transient detection is further developed, comprising of automatic detection of specific areas of interest in Hilbert spectra between 10E-1 Hz and 1 Hz, corresponding with the occurrence of transients in the respective ECN signals. Regarding the detection of MIC, together with monitoring of the OCP and microscopic observations, the development of ECN transients generated by localized corrosion processes could be attributed to the presence and activity of sulphate-reducing bacteria. These transients are related to the existence of pits in the carbon steel surface, underneath the attached biofilm. Finally, practical aspects and configurations for electrochemical noise measurements (ENM) are discussed. ENM can be applied in a hand-held solution, or for permanent monitoring. Analogous to the selection of the appropriate data analysis procedure to obtain the information of interest, it is important to consider the required application to select the most suitable configuration. ENM is a potentially interesting technique because of its non-intrusive nature, the robust sensor configurations, the ability to identify localized corrosion processes and ease of use. The most complicated aspect of ENM is the interpretation of the EN signals, for which the data analysis procedure can be fully automated if required.

Computer controlled apparatus for laser flash spectroscopy has been constructed. Nitrogen laser (energy 1 inJ, pulse width 1 ns) is used both for excitation of the sample and for pumping the tunable dye laser which serves as a source of monitoring light. Two different scans are possible: (i) a mode with a fixed wavelength of the inonitoring light - the temporal evolution of the transient absorption in the range from -2 ns up to 100 ns can be observed by changing the length of the variable self-compensating optical delay line, (ii) a mode with a fixed time delay - the corresponding transient absorption in the range 380 - 800 nm can be measured. For illustration, time evolution of transient absorption and time resolved spectra of benzanthracene in ethanol are reported.