Portion Of Signal Research Articles

Comparative study of image contrast in scanning electron microscope and helium ion microscope.

Images of Ga+ -implanted amorphous silicon layers in a 110 n-type silicon substrate have been collected by a range of detectors in a scanning electron microscope and a helium ion microscope. The effects of the implantation dose and imaging parameters (beam energy, dwell time, etc.) on the image contrast were investigated. We demonstrate a similar relationship for both the helium ion microscope Everhart-Thornley and scanning electron microscope Inlens detectors between the contrast of the images and the Ga+ density and imaging parameters. These results also show that dynamic charging effects have a significant impact on the quantification of the helium ion microscope and scanning electron microscope contrast.

Determination of maternal pedigree and ewe-lamb spatial relationships by application of Bluetooth technology in extensive farming systems.

The objectives of this study were to validate the application of Bluetooth technology to determine maternal pedigree and to determine ewe-lamb spatial relationships in extensive farming systems. A total of 35 first-cross Merino ewes (Merino × Border Leicester and East Friesian) and 23 of their lambs aged 1 to 3 wk were fitted with activity monitors equipped with Bluetooth (BT) technology (ActiGraph wGT3X-BT) by means of halters and collars, respectively. The BT devices on lambs were programmed to receive wireless signals once every minute from nearby BT units on ewes, which were programmed as beacons sending BT signals 4 times every second. Ewes and lambs fitted with sensors were dispatched into the paddocks, and after 10 d, the sensor units were retrieved and the BT signals received by lambs were downloaded using the ActiGraph software. The maternal pedigree of the lambs was determined as the ewe from which the lamb received the most BT signals. The distance between the lamb receiving the signal and the ewe sending the signal was estimated from the strength of BT signal received. The pedigree determined by BT was compared with the pedigree determined by DNA profiling and verification. The results showed that the accuracy of maternal pedigree determined by BT signals reached 100% within the first 15 min of returning animals to pasture of ewes and lambs fitted with sensors. Maternal signals (counts/d) received by 1-, 2-, and 3-wk-old lambs were 617 ± 102, 603 ± 54, and 498 ± 36, respectively, and the corresponding nonmaternal signals received were 140 ± 27, 106 ± 30, and 155 ± 39, respectively. Maternal signals received during the dark period were significantly higher than the maternal signals received during the light period ( < 0.05). Maternal signals received during the light period by 3-wk-old lambs were significantly lower when compared with those received by 1- and 2-wk-old lambs. Over 90% of the BT signals received from within 2 m of the lamb were from its mother. The maternal BT signals expressed as a portion of total BT signals decreased with increasing distance from the lamb. The results show that BT wireless networking is a fast and reliable method for the determination of maternal pedigree of lambs in extensive farming systems. In addition, wireless BT technology is also useful in determining mother-offspring spatial relationships.

Time domain analysis of ultrasonic backscatter signals from cancellous bone

Ultrasonic backscatter techniques are being developed to detect changes in bone caused by osteoporosis. Most techniques analyze backscatter signals in the frequency domain by measuring quantities related to the power spectrum. Investigate the utility of two backscatter parameters determined from a time domain analysis of backscatter signals: the normalized backscatter amplitude ratio (nBAR) and the backscatter amplitude decay constant (BADC). A 3.5 MHz transducer was used to acquire backscatter signals from 54 specimens of bone prepared from 14 human femurs. nBAR was determined from the log of the ratio of the root mean square amplitude of two different portions of a backscatter signal. BADC was determined by measuring the exponential decay in the amplitude of a backscatter signal. nBAR and BADC both demonstrated highly significant (p < 0.001) linear correlations with bone density. However, the correlation coefficients were slightly stronger for nBAR (0.79 ≤ R ≤ 0.89) than for BADC (0.67 ≤ R ≤ 0.73). Parameters based on a time domain analysis of backscatter signals from bone may be sensitive to changes in bone caused by osteoporosis. Of the two parameters tested, nBAR demonstrated the strongest correlations with bone density. [Funding: NIH/NIAMS R15AR066900.]

Perpendicular Cross-Spectra Fusion for Sound Source Localization With a Planar Microphone Array

Multiple sound source localization in reverberant environments stands as one of the most difficult challenges for many applications related to microphone array signal processing. In this paper, we describe perpendicular cross-spectra fusion (PCSF), a new direction-of-arrival (DOA) estimation algorithm, which utilizes an analytic formula for direction estimation in the time–frequency (TF) domain. Inherent to this technique is the presence of multiple direction estimation subsystems which operate in parallel, producing a multiplicity of candidate DOAs at each TF point. We define a metric of coherence, based on the property of divergence of the different DOA estimators, for assessing the reliability of different signal portions, so that only TF bins with a high quality of directional information are exploited for local DOA estimation. The resulting collection of local DOAs is provided as input to a recently proposed histogram processing approach, which is based on matching pursuit. Results based on simulation and real recordings illustrate the advantages of PCSF compared to other DOA estimation techniques subject to the same histogram-based processing, in the context of real-time multiple source localization and counting; improved performance in reverberant conditions and high tolerance to diffuse and common mode noise.

On the Resolvability of Steam Assisted Gravity Drainage Reservoirs Using Time-Lapse Gravity Gradiometry

Unconventional heavy oil resource plays are important contributors to oil and gas production, as well as controversial for posing environmental hazards. Monitoring those reservoirs before, during, and after operations would assist both the optimization of economic benefits and the mitigation of potential environmental hazards. This study investigates how gravity gradiometry using superconducting gravimeters could resolve depletion areas in steam assisted gravity drainage (SAGD) reservoirs. This is achieved through modelling of a SAGD reservoir at 1.25 and 5 years of operation. Specifically, the density change structure identified from geological, petrological, and seismic observations is forward modelled for gravity and gradients. Three main parameters have an impact on the resolvability of bitumen depletion volumes and are varied through a suitable parameter space: well pair separation, depth to the well pairs, and survey grid sampling. The results include a resolvability matrix, which identifies reservoirs that could benefit from time-lapse gravity gradiometry monitoring. After 1.25 years of operation, during the rising phase, the resolvable maximum reservoir depth ranges between the surface and 230 m, considering a well pair separation between 80 and 200 m. After 5 years of production, during the spreading phase, the resolvability of depletion volumes around single well pairs is greatly compromised as the depletion volume is closer to the surface, which translates to a larger portion of the gravity signal. The modelled resolvability matrices were derived from visual inspection and spectral analysis of the gravity gradient signatures and can be used to assess the applicability of time-lapse gradiometry to monitor reservoir density changes.

Effect of gate choice on backscatter difference measurements of cancellous bone.

A variety of ultrasonic techniques have been developed to detect changes in bone caused by osteoporosis. One approach, called the backscatter difference technique, analyzes the power difference between two different portions of a backscatter signal. Analysis gates with a certain delay τd, width τw, and separation τs are used to define portions of the backscatter signal for analysis. The goal of the present study was to investigate how different choices of τd, τw, and τs affect four backscatter difference parameters: the normalized mean of the backscatter difference (nMBD), the normalized slope of the backscatter difference (nSBD), the normalized intercept of the backscatter difference (nIBD), and the normalized backscatter amplitude ratio (nBAR). Backscatter measurements were performed on 54 cube shaped specimens of human cancellous bone. nMBD, nSBD, nIBD, and nBAR were determined for 34 different combinations of τd, τw, and τs for each specimen. nMBD and nBAR demonstrated the strongest correlations with apparent bone density (0.48 ≤ Rs ≤ 0.90). Generally, the correlations were found to improve as τw + τs was increased and as τd was decreased. Among the four backscatter difference parameters, the measured values of nMBD were least sensitive to gate choice (<16%).

Phonetic variability in Moroccan Arabic rhotics

Moroccan Arabic /r/ and its pharyngealized counterpart exhibit a wide range of variability in their pronunciation, with reported articulations ranging from apical trills to uvular fricatives. Using an phonetic dataset elicited from speakers of the dialect of Fès (reported to traditionally have a uvular variant), I assess the distribution and acoustic properties of rhotic variants, including coarticulatory effects. The data present three distinct rhotic articulations: (1) an apical trill or tap, (2) an apical continuant produced together with high-frequency sibilant noise, and (3) a dorsal sonorant or rhotacized vowel similar to English “burred /r/.” Despite claims in the literature, no uvular fricative was observed in the data, and the dorsal sonorant was identified by speakers as the idiosyncratic local pronunciation. Variants (1) and (2) further exhibit devoiced positional variants. Lowered F2 of adjacent vowels and of sonorant portions of the rhotic signal differentiate the pharyngealized phoneme /rʕ/ from its plain counterpart /r/. However, both phonemes were found to exhibit the same range of variation in their primary articulation. Two acoustic properties common to all variants were (a) depression and attenuation of upper formants and (b) the presence of some aperiodic noise above 5 kHz.

Markovian Analysis of the Sequential Behavior of the Spontaneous Spinal Cord Dorsum Potentials Induced by Acute Nociceptive Stimulation in the Anesthetized Cat.

In a previous study we developed a Machine Learning procedure for the automatic identification and classification of spontaneous cord dorsum potentials (CDPs). This study further supported the proposal that in the anesthetized cat, the spontaneous CDPs recorded from different lumbar spinal segments are generated by a distributed network of dorsal horn neurons with structured (non-random) patterns of functional connectivity and that these configurations can be changed to other non-random and stable configurations after the noceptive stimulation produced by the intradermic injection of capsaicin in the anesthetized cat. Here we present a study showing that the sequence of identified forms of the spontaneous CDPs follows a Markov chain of at least order one. That is, the system has memory in the sense that the spontaneous activation of dorsal horn neuronal ensembles producing the CDPs is not independent of the most recent activity. We used this markovian property to build a procedure to identify portions of signals as belonging to a specific functional state of connectivity among the neuronal networks involved in the generation of the CDPs. We have tested this procedure during acute nociceptive stimulation produced by the intradermic injection of capsaicin in intact as well as spinalized preparations. Altogether, our results indicate that CDP sequences cannot be generated by a renewal stochastic process. Moreover, it is possible to describe some functional features of activity in the cord dorsum by modeling the CDP sequences as generated by a Markov order one stochastic process. Finally, these Markov models make possible to determine the functional state which produced a CDP sequence. The proposed identification procedures appear to be useful for the analysis of the sequential behavior of the ongoing CDPs recorded from different spinal segments in response to a variety of experimental procedures including the changes produced by acute nociceptive stimulation. They are envisaged as a useful tool to examine alterations of the patterns of functional connectivity between dorsal horn neurons under normal and different pathological conditions, an issue of potential clinical concern.

Evaluation and Current-Response-Based Identification of Insulation Degradation for High Utilized Electrical Machines in Railway Application

The demand for condition monitoring systems to prevent a breakdown of electrical machines is continuously increasing. A failure or collapse of the insulation is one of the main reasons for a machine outage, both in the field of high-voltage machines as well as low voltage. Especially at inverter-fed motors, several kinds of stresses due to parasitic phenomena exist and cause decrease of the insulation lifetime. With the method proposed, the evaluation of the stator insulation health condition of inverter-fed motors is possible by analyzing the current sensors transient response after inverter voltage step excitation. The analysis of the transient signal portion gives evidence of a possible change in the insulation system by comparison of the characteristics with the known pattern of the healthy machine transient signal portion. Tests are performed on a 1.4-MW induction machine designed for traction applications. By the availability of taps accessible on the machine terminal, different scenarios to emulate winding insulation degradation are conducted. Additionally, in order to investigate insulation degradation characteristics of the used insulation materials, accelerated aging procedures are applied on specially manufactured stator slot models with form-wound coils. These stator test segments have been aged by different accelerated aging cycles until the failure of the insulation is determined by voltage exposure tests. With additional nondestructive diagnostic measurements, e.g., dissipation factor ${\rm{(tan\,\delta)}}$ , capacitance, the correlation between these indicator values, the results of the proposed method, and the degradation of the insulation strength until a breakdown are investigated.

A robust adaptive fuzzy variable structure tracking control for the wheeled mobile robot: Simulation and experimental results

In this paper an adaptive fuzzy variable structure control (kinematic control) integrated with a proportional plus derivative control (dynamic control) is proposed as a robust solution to the trajectory tracking control problem for a differential wheeled mobile robot. The variable structure controller, based on the sliding mode theory, is a well known, proven control method, fit to deal with uncertainties and disturbances (e.g., structural and parameter uncertainties, external disturbances and operating limitations). To minimize the problems found in practical implementations of the classical variable structure controllers, an adaptive fuzzy logic controller replaces the discontinuous portion of the control signals (avoiding the chattering), causing the loss of invariance, but still ensuring the robustness to uncertainties and disturbances without having any a priori knowledge of their boundaries. Moreover, the adaptive fuzzy logic controller is a feasible tool to approximate any real continuous nonlinear system to arbitrary accuracy, and has a simple structure by using triangular membership functions, a low number of rules that must be evaluated, resulting in a lower computational load for execution, making it feasible for real time implementation. Stability analysis and the convergence of tracking errors as well as the adaptation laws are guaranteed with basis on the Lyapunov theory. Simulation and experimental results are explored to show the verification and validation of the proposed control strategy.

Estimation of Earthquake Early Warning Parameters for Eastern Sicily

Abstract Earthquake early warning systems (EEWSs) are becoming a suitable instrument for seismic risk management in real time. In fact, they are implemented or are undergoing testing in many countries around the world because EEWSs represent an effective approach to mitigating seismic risk on a short timescale. EEWSs are based on the use of relationships between some parameters measured on the initial portion of seismic signal after the onsets. Here, we address the first approach to the implementation of EEWS in eastern Sicily, a region that has been hit by several destructive earthquakes. We estimated the peak displacement amplitude of the first portion of P and S waves P d , the ground‐motion period parameter τ c , and the peak ground velocity (PGV) from earthquakes with M L ≥2.8 recorded by the broadband stations operated by the Istituto Nazionale di Geofisica e Vulcanologia. We found that the P d is correlated with the size of the earthquake and may be used to compute the magnitude for an EEWS in this area. We also derived the relationships between τ c and M L , and between P d and PGV, which can be used to provide on‐site warning in the area around a given station and to evaluate the potential damaging effects. These relationships may be deemed a useful guide for future implementation of the EEWS in the region.

Quantifying the low bias of CALIPSO's column aerosol optical depth due to undetected aerosol layers.

The CALIOP data processing scheme only retrieves extinction profiles in those portions of the return signal where cloud or aerosol layers have been identified by the CALIOP layer detection scheme. In this study we use two years of CALIOP and MODIS data to quantify the aerosol optical depth of undetected weakly backscattering layers. Aerosol extinction and column-averaged lidar ratio is retrieved from CALIOP Level 1B (Version 4) profile using MODIS AOD as a constraint over oceans from March 2013 to February 2015. To quantify the undetected layer AOD (ULA), an unconstrained retrieval is applied globally using a lidar ratio of 28.75 sr estimated from constrained retrievals during the daytime over the ocean. We find a global mean ULA of 0.031 ± 0.052. There is no significant difference in ULA between land and ocean. However, the fraction of undetected aerosol layers rises considerably during daytime, when the large amount of solar background noise lowers the signal to noise ratio (SNR). For this reason, there is a difference in ULA between day (0.036 ± 0.066) and night (0.025 ± 0.021). ULA is larger in the northern hemisphere and relatively larger at high latitudes. Large ULA for the Polar Regions is strongly related to the cases where the CALIOP Level 2 Product reports zero AOD. This study provides an estimate of the complement of AOD that is not detected by lidar, and bounds the CALIOP AOD uncertainty to provide corrections for science studies that employ the CALIOP Level 2 AOD.

Ultrasonic backscatter difference measurements of cancellous bone: Relationships with microstructure and bone mineral density

Background: Backscatter difference techniques are being developed to detect changes in bone caused by osteoporosis. Backscatter difference techniques compare the power in one portion of an ultrasonic backscatter signal to the power in a different portion of the same signal. Goal: Investigate how backscatter difference measurements depend on the density and microstructural characteristics of cancellous bone. Procedure: Ultrasonic backscatter signals were acquired from 30 specimens of bone using a 1 and 5 MHz broadband transducer. The normalized mean backscatter difference (nMBD) was determined by computing the power difference (in dB) between two gated portions of the backscatter signal and dividing by the center to center time separation between gates. Microstructural characteristics of the specimens and bone mineral density (BMD) were determined using high resolution x-ray micro-computed tomography. Results: nMBD demonstrated moderate to strong linear correlations with microstructure and BMD (0.50 ≤ |R| ...

Using Two Independent Channels With Gateway for FlexRay Static Segment Scheduling

The FlexRay bus is a communication standard used in the automotive industry. It offers a deterministic message transmission in the static segment following a time-triggered schedule. Even if its bandwidth is ten times higher than the bandwidth of CAN, its throughput limits are going to be reached in high-class car models soon. A solution that could postpone this problem is to use an efficient scheduling algorithm that exploits both channels of the FlexRay. The significant and often neglected feature that can theoretically double the bandwidth is the possibility to use two independent communication channels that can intercommunicate through the gateway. In this paper, we propose a heuristic algorithm that decomposes the scheduling problem to the ECU-to-channel assignment subproblem which decides which channel the ECUs (Electronic Control Units) should be connected to and the channel scheduling subproblem which creates static segment communication schedules for both channels. The algorithm is able to create a schedule for cases where channels are configured in the independent mode as well as in the fault-tolerant mode or in cases where just part of the signals are fault-tolerant. Finally, the algorithm is evaluated on real data and synthesized data, and the relation between the portion of fault-tolerant signals and the number of allocated slots is presented.

Luminescent detector for free-space optical communication

In one embodiment, an apparatus includes a wavelength-shifting element configured to receive an input-light signal. The wavelength-shifting element includes a wavelength-shifting material configured to absorb at least a portion of the received input-light signal and produce an emitted-light signal from the absorbed portion of the received input-light signal. The apparatus also includes an optical-concentrating element configured to receive at least a portion of the emitted-light signal and concentrate the received portion of the emitted-light signal onto a photodetector. The apparatus further includes the photodetector configured to receive the concentrated portion of the emitted-light signal and produce an electrical current corresponding to the concentrated portion of the emitted-light signal.

THE FINE-TUNING OF LINGUISTIC EXPECTATIONS OVER THE COURSE OF L2 LEARNING

This study investigates the degree to which native-English-speaking learners of Spanish can generate expectations for information likely to occur in upcoming portions of an unfolding linguistic signal. We examine Spanish clitic left dislocation, a long-distance dependency between a topicalized object and an agreeing clitic, whose felicity depends on the discourse. Using a self-paced reading task, we tested the predictions of the shallow structure hypothesis (Clahsen &amp; Felser, 2006a, 2006b) and the reduced ability to generate expectations hypothesis (Grüter, Rohde, &amp; Schafer, 2014). Learners successfully demonstrated sensitivity to the violation of expectations set up by the syntactic and discourse context. In addition, the behavior of the second language (L2) learners was dependent on proficiency: the higher their proficiency, the more their behavior mirrored native-speaker processing. These results support a view of SLA in which knowledge of L2 discourse-grammatical relationships is acquired slowly over the course of L2 learning.

Enhancement of second-harmonic generation in nonlinear nanolaminate metamaterials by nanophotonic resonances.

Nanolaminate metamaterials recently attracted a lot of attention as a novel second-order nonlinear material that can be used in integrated photonic circuits. Here, we explore theoretically and numerically the opportunity to enhance the nonlinear response from such nanolaminates by exploiting Fano resonances supported in grating-coupled waveguides. The enhancement factor of the radiated second harmonic signal compared to a flat nanolaminate can reach values as large as 35 for gold gratings and even 7000 for MgF2 gratings. For the MgF2 grating, extremely high-Q Fano resonances are excited in such all-dielectric system that result in strong local fields in the nonlinear waveguide layer to boost the nonlinear conversion. A significant portion of the nonlinear signal is also strongly coupled to a dark waveguide mode, which remains guided in the nanolaminate. The strong excitation of a dark mode at the second harmonic frequency provides a viable method for utilizing second-order nonlinearities for light generation and manipulation in integrated photonic circuits.

The transfer of seasonal isotopic variability between precipitation and drip water at eight caves in the monsoon regions of China

This study presents new stable isotope data for precipitation (δ18Op) and drip water (δ18Od) from eight cave sites in the monsoon regions of China (MRC), with monthly to bi-monthly sampling intervals from May-2011 to April-2014, to investigate the regional-scale climate forcing on δ18Op and how the isotopic signals are transmitted to various drip sites.The monthly δ18Op values show negative correlation with surface air temperature at all the cave sites except Shihua Cave, which is opposite to that expected from the temperature effect. In addition, although the monthly δ18Op values are negatively correlated with precipitation at all the cave sites, only three sites are significant at the 95% level. These indicate that, due to the various vapor sources, a large portion of variability in δ18Op in the MRC cannot be explained simply by either temperature or precipitation alone.All the thirty-four drip sites are classified into three types based on the δ18Od variability. About 82% of them are static drips with little discernable variation in δ18Od through the whole study period, but the drip rates of these drips are not necessary constant. Their discharge modes are site-specific and the oxygen isotopic composition of the stalagmites growing from them may record the average of multi-year climatic signals, which are modulated by the seasonality of recharge and potential effects of evaporation, and in some cases infiltration from large rainfall events. About 12% of the thirty-four drip sites are seasonal drips, although the amplitude of δ18Od is narrower than that of δ18Op, the monthly response of δ18Od to coeval precipitation is not completely damped, and some of them follow the seasonal trend of δ18Op very well. These drips may be mainly recharged by present-day precipitation, mixing with some stored water. Thus, the stalagmites growing under them may record portions of the seasonal climatic signals embedded in δ18Op. About 6% of the thirty-four drip sites are medium-variability drips, with constant and relatively low δ18Od values in the wet season, but with variable and relatively high δ18Od values in the dry season, reflecting flow switching in the karst or evaporation inside the cave.

The contribution of amplitude modulations from speech and competing noise sources for speech recognition

Speech is often heard in the presence of background noise during everyday listening conditions. Concurrent amplitude modulations of the speech and the interfering noise result in portions (i.e., “glimpses”) of the speech signal that remain preserved at favorable signal-to-noise ratios while other portions of speech may be highly degraded. The acoustic and phonetic properties preserved during these glimpses play a role in determining the overall sentence intelligibility. Under such conditions, vocalic cues are relatively more preserved than consonantal/obstruent cues due to average differences in intensity. Investigations examining these different acoustic cues suggest important perceptual contributions from preserved speech amplitude modulations and non-simultaneous interactions from competing noise amplitude modulations. Results from several studies suggest that conditions that maximize the preservation of the sentence temporal envelope (e.g., during long glimpses or for vocalic intervals) result in higher levels of speech recognition. Amplitude modulation during noise-dominated intervals also impacts speech recognition performance. Overall, results suggest that the relative preservation and interaction (e.g., modulation masking or perceptual restoration) of amplitude modulations from the speech and noise is crucial for predicting speech recognition during noise interruption. [Work supported by NIH and ASHA.]

POLYAN: a package for a polyparametric approach to cardio-respiratory variability signals analysis.

POLYAN, a computer program based on a point-and-click graphical user interface for easy and efficient polyparametric analysis of cardio-respiratory variability signals is described. The main tasks performed by the package are: univariate and bivariate spectral analysis on selected portions of the signals with the computation of some clinically relevant indices and baroreflex sensitivity assessment by the analysis of the relationship between systolic pressure and heart period signals. Some tools which help the analyst in the solution of common practical problems have been implemented to make analysis easier and more rigorous. Using Matlab language, POLYAN has the flexibility and expandability necessary for a research tool, which often requires implementation of new algorithms and computation of new parameters.