Common Waveform Research Articles

Broad-band waveforms and robust processing for marine CSEM surveys

SUMMARY In the marine controlled-source electromagnetic method, the Earth response varies in frequency; therefore, using a wide range of frequencies may better constrain geological structure than using a single frequency or only a few closely spaced frequencies. Binary waveforms, such as the square wave, provide a number of frequencies, though many are limited in usefulness because of the rapid decline of amplitude with frequency. Binary waveform design can be improved by recognizing that the class of doubly symmetric waveforms has special properties: they are compact, have controlled phase, are never polarizing and can be described by a simple closed-form mathematical solution. Using this solution, we discovered a compact waveform in which the amplitudes of the third and seventh harmonics are maximized and which has a signal-to-noise advantage at higher frequencies over several other common waveforms. Compact waveforms make possible improved methods for time-series processing. Using short time windows and a first-difference pre-whitener lessens spectral contamination from magnetotelluric signal and oceanographic noise; robust stacking reduces bias from time-series noise transients; and accurate variance estimates may be derived from averages of waveform-length Fourier transform windows of the time-series.

Characterization of volumetric flow rate waveforms at the carotid bifurcations of older adults

While it is widely appreciated that volumetric blood flow rate (VFR) dynamics change with age, there has been no detailed characterization of the typical shape of carotid bifurcation VFR waveforms of older adults. Toward this end, retrospectively gated phase contrast magnetic resonance imaging was used to measure time-resolved VFR waveforms proximal and distal to the carotid bifurcations of 94 older adults (age 68 ± 8 years) with little or no carotid artery disease, recruited from the BLSA cohort of the VALIDATE study of factors in vascular aging. Timings and amplitudes of well-defined feature points from these waveforms were extracted automatically and averaged to produce representative common, internal and external carotid artery (CCA, ICA and ECA) waveform shapes. Relative to young adults, waveforms from older adults were found to exhibit a significantly augmented secondary peak during late systole, resulting in significantly higher resistance index (RI) and flow augmentation index (FAI). Cycle-averaged VFR at the CCA, ICA and ECA were 389 ± 74, 245 ± 61 and 125 ± 49 mL min−1, respectively, reflecting a significant cycle-averaged outflow deficit of 5%, which peaked at around 10% during systole. A small but significant mean delay of 13 ms between arrivals of ICA versus CCA/ECA peak VFR suggested differential compliance of these vessels. Sex and age differences in waveform shape were also noted. The characteristic waveforms presented here may serve as a convenient baseline for studies of VFR waveform dynamics or as suitable boundary conditions for models of blood flow in the carotid arteries of older adults.

Implementation of method for operating multiple high frequency surface wave radars on a common carrier frequency

The increasing use of High Frequency Surface Wave Radar (HFSWR) for the surveillance of coastal regions is faced with the problem of limited channel availability in the electromagnetic spectrum. Thus, there is a need for multiple radars to share a common frequency channel. Proof-of-concept work is presented here for a method to operate multiple radar systems on a common carrier frequency. A review is provided of an existing concept where a common waveform is modulated by tones varying by a few hertz across the different radars. The signals from the different radars are separated by either pulse-domain filtering or Doppler processing. An experiment has been performed that demonstrates the feasibility of the method. Limitations of the method are considered in terms of the linearity of the propagation channel.

Fixed Average Spectra of Orchestral Instrument Tones

The fixed spectrum for an orchestral instrument tone is presented based on spectral data from the Sandell Harmonic Archive (SHARC). This database contains non-time-variant spectral analyses for 1,338 recorded instrument tones from 23 Western instruments ranging from contrabassoon to piccolo. From these spectral analyses, a grand was calculated, providing what might be considered an non-time-variant harmonic spectrum. Each of these tones represents the of all instruments in the SHARC database capable of producing that pitch. These latter tones better represent common spectral changes with respect to pitch register, and might be regarded as an average instrument. Although several caveats apply, an harmonic tone or instrument may prove useful in analytic and modeling studies. In addition, for perceptual experiments in which non-time-variant stimuli are needed, an harmonic spectrum may prove to be more ecologically appropriate than common technical waveforms, such as sine tones or pulse trains. Synthesized tones are available via the web.

Noninvasive Assessment of Arterial Stiffness Should Discriminate Between Systolic and Diastolic Pressure Ranges

Arterial stiffening plays an important role in the development of hypertension and cardiovascular diseases. The intrinsically nonlinear (ie, pressure-dependent) elastic behavior of arteries may have serious consequences for the accuracy and interpretation of arterial stiffness measurements and, ultimately, for individual patient management. We determined aortic pressure and common carotid artery diameter waveforms in 21 patients undergoing cardiac catheterization. The individual pressure-area curves were described using a dual exponential analytic model facilitating noise-free calculation of incremental pulse wave velocity. In addition, compliance coefficients were calculated separately in the diastolic and systolic pressure ranges, only using diastolic, dicrotic notch, and systolic data points, which can be determined noninvasively. Pulse wave velocity at systolic pressure exhibited a much stronger positive correlation with pulse pressure (P<0.001) and age (P=0.012) than pulse wave velocity at diastolic pressure. Patients with an elevated systolic blood pressure (>140 mm Hg) had a 2.5-times lower compliance coefficient in the systolic pressure range than patients with systolic blood pressures <140 mm Hg (P=0.002). Most importantly, some individuals, with comparable age or pulse pressure, had similar diastolic but discriminately different systolic pulse wave velocities and compliance coefficients. We conclude that noninvasive assessment of arterial stiffness could and should discriminate between systolic and diastolic pressure ranges to more precisely characterize arterial function in individual patients.

High‐current lightning discharges in winter

AbstractLightning electric‐field waveforms related to power line faults in winter have been identified. Most of those waveforms appear to be associated with upward lightning discharges with absolute peak currents of over 100 kA. They are quite different from common return‐stroke waveforms, and the lightning discharges which produce these characteristic waveforms are called GC (Ground to Cloud) flashes. These high‐current lightning discharges are distributed around the coastline in different ways depending on their polarities. The spatial distributions of high‐current lightning discharges around Japan are also investigated. It is revealed that the region of Honshu Island along the coastline of the Sea of Japan belongs to the area in which the density of high‐current lightning flashes is the highest in Japan through the year. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 8–15, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20874

1546: Abdominal Aortic Aneurysm Detection by Common Femoral Artery Doppler Ultrasound Waveform Analysis

1546: Abdominal Aortic Aneurysm Detection by Common Femoral Artery Doppler Ultrasound Waveform Analysis

Computing circadian rhythmic patterns and beyond: introduction to a new non-Fourier analysis

We introduce a new computational approach for recognizing and analyzing rhythmic dynamics hidden in lengthy recording of animal’s locomotive activity. This recoding is presented in a form of event-time series, and termed actogram in biological rhythm literature. Upon an actogram, we lay out the construction of our computational approach, called hierarchical segmentation (HS) approach, on a platform based on 3-level-coding algorithm with detailed heuristic ideas and statistical explanation. Our HS approach is then demonstrated to objectively compute and identify a series of phase-markers, which in turn partition the whole actogram into a series of circadian rhythmic cycles of varying lengths. Among these rhythmic cycles, common waveform pattern is also extracted as the chief characteristic of recognizing individual circadian dynamics, and period is calculated as the averaged length of the series of rhythmic cycles. Also we demonstrate how to measure the essential ingredients of rhythmic dynamics: phase-shifts due to Zeitgeber and their information contents, through simple linear regression analysis on subseries of phase-markers before and after Zeitgeber. Along our development explicit contrasts are made to explain the shortcomings of periodogram or Fourier transform based spectrum analysis which rigidly determines rhythmic cycles with equal length, and in general ignores the waveform identification completely. We then show a new construction for the phase response curve (PRC) with confidence band. This construction is proved to be critical for biologists who endeavor to make unbiased inferences on circadian rhythm. Examples of real data analysis on actogram of German cockroach are realistically illustrated. Beyond as being an alternative, we conclude that our computational approach can deliver viable non-Fourier rhythmic pattern recognition on circadian rhythms.

A comparison of clinical and eye movement characteristics between albinism and idiopathic infantile nystagmus with and without mutations in the FRMD7 gene

Abstract Purpose Nystagmus consists of involuntary to and fro oscillations of the eyes. The differences between nystagmus associated with albinism and idiopathic infantile nystagmus (IIN) are unclear. Recently mutations in a novel gene called FRMD7 have been found to underlie a significant proportion of X‐linked IIN. Phenotypic variations in eye movements between FRMD7 and non‐FRMD7 types have also been recently described. We have compared clinical and eye movement characteristics between albinism and IIN with and without mutations in the FMRD7 gene. Methods Clinical features and eye movement were recorded from 37 albino subjects, 83 subjects with the FRMD7 mutation and 45 subjects without the FRMD7 mutation. Results Mean visual acuity was significantly worse in albinos compared to IIN patients (p&lt;&lt;0.0001). Although there was no significant differences between the groups (p&gt;0.05) for nystagmus amplitude or foveation, the frequency of nystagmus was significantly slower in albinism (p&lt;&lt;0.0001). In addition, nystagmus associated with albinism was significantly more likely to be jerk nystagmus rather than pendular nystagmus compared to FRMD7 group (p&lt;&lt;0.0001). The most common waveform associated with albinism was pure jerk nystagmus, whereas non‐FRMD7 was more likely to be associated with jerk with extended foveation. Conclusion Contrary to available literature, nystagmus associated with albinism shows distinct differences to IIN both with and without FRMD7 mutations. This suggests the possibility of different underlying mechanisms to albinism and IIN in generating eye oscillations although these are yet to be elucidated

Gene Expression of Endothelial Cells under Pulsatile Non-Reversing vs. Steady Shear Stress; Comparison of Nitric Oxide Production

Pulsations in arterial blood flow expose the endothelium to diverse mechanical forces that may differentially regulate endothelial cell (EC) phenotype. We postulated that pulsatile non-reversing shear stress (typical of the common carotid artery), would produce a more "athero-protective" gene expression pattern compared with steady shear stress of the same mean value. Transcriptional analysis of human umbilical vein endothelial cells (HUVEC) subjected to 24 h of pulsatile shear stress (average = 13 dyne/cm(2), range = 7-25 dyne/cm(2); 1 Hz) or steady shear stress (13 dyne/cm(2)) identified approximately 200 differentially expressed genes. Hierarchical cluster analysis indicated that HUVEC respond similarly to both types of shear stress (Pearson correlation coefficient = 0.785). However, categorization of the differentially expressed genes with Ingenuity Pathways Analysis and with Expression Analysis Systematic Explorer revealed possible differences in nitric oxide (NO) production and signaling. Consistent with gene expression analysis, pulsatile shear stress significantly attenuated NO production relative to steady shear stress (0.77 +/- 0.08, p < 0.01) in HUVEC without significantly altering the levels of intracellular reactive oxygen species (0.95 +/- 0.14, p = 0.65). These results demonstrate that the common carotid flow waveform elicits subtle changes in HUVEC responses to arterial levels of shear stress, which lead to differences in NO production.

Climatology of the Sierra Nevada Mountain-Wave Events

Abstract This note presents a satellite-based climatology of the Sierra Nevada mountain-wave events. The data presented were obtained by detailed visual inspection of visible satellite imagery to detect mountain lee-wave clouds based on their location, shape, and texture. Consequently, this climatology includes only mountain-wave events during which sufficient moisture was present in the incoming airstream and whose amplitude was large enough to lead to cloud formation atop mountain-wave crests. The climatology is based on data from two mountain-wave seasons in the 1999–2001 period. Mountain-wave events are classified in two types according to cloud type as lee-wave trains and single wave clouds. The frequency of occurrence of these two wave types is examined as a function of the month of occurrence (October–May) and region of formation (north, middle, south, or the entire Sierra Nevada range). Results indicate that the maximum number of mountain-wave events in the lee of the Sierra Nevada occurs in the month of April. For several months, including January and May, frequency of wave events displays substantial interannual variability. Overall, trapped lee waves appear to be more common, in particular in the lee of the northern sierra. A single wave cloud on the lee side of the mountain range was found to be a more common wave form in the southern Sierra Nevada. The average wavelength of the Sierra Nevada lee waves was found to lie between 10 and 15 km, with a minimum at 4 km and a maximum at 32 km.

High-Current Lightning Discharges in Winter

Lightning electric-field waveforms related to power line faults in winter have been identified. Most of those waveforms appear to be associated with upward lightning discharges with absolute peak currents of over 100 kA. They are quite different from common return-stroke waveforms, and the lightning discharges which produce these characteristic waveforms are called GC (Ground to Cloud) flashes. These high-current lightning discharges are distributed around the coastline in different ways depending on their polarities. The spatial distributions of high-current lightning discharges around Japan are also investigated. It is revealed that the region of Honshu Island along the coastline of the Sea of Japan belongs to the area in which the density of high-current lightning flashes is the highest in Japan through the year. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 8–15, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20874

Open Architecture Standard for NASA's Software-Defined Space Telecommunications Radio Systems

NASA is developing an architecture standard for software-defined radios used in space- and ground-based platforms to enable commonality among radio developments to enhance capability and services while reducing mission and programmatic risk. Transceivers (or transponders) with functionality primarily defined in software (e.g., firmware) have the ability to change their functional behavior through software alone. This radio architecture standard offers value by employing common waveform software interfaces, method of instantiation, operation, and testing among different compliant hardware and software products. These common interfaces within the architecture abstract application software from the underlying hardware to enable technology insertion independently at either the software or hardware layer. This paper presents the initial Space Telecommunications Radio System architecture for NASA missions to provide the desired software abstraction and flexibility while minimizing the resources necessary to support the architecture.

Global features of Pi 2 pulsations obtained by independent component analysis

Ground Pi 2 pulsations are mixtures of several components reflecting (1) propagations of fast and shear Alfvén wave, (2) resonances of plasmaspheric/magnetospheric cavity and magnetic field lines, and (3) transformations to ionospheric current systems. However, it has been unclear how they coupled with each other and how their signals are distributed at different latitudes. The present work is intended to pilot the future possibilities whether we can identify the global system of Pi 2 pulsations by Independent Component Analysis (ICA). We have successfully decomposed an isolated Pi 2 event on a quiet day observed at the CPMN stations into two components. One was the global oscillation that occurs from nightside high to equatorial latitudes with the common waveform and has an amplitude maximum at nightside high latitude. Another component was localized at nightside high latitudes. Its amplitudes were quite weak at low latitudes, but were enhanced near dayside dip equator.

Optoelectronic retinal prosthesis: system design and performance

The design of high-resolution retinal prostheses presents many unique engineering and biological challenges. Ever smaller electrodes must inject enough charge to stimulate nerve cells, within electrochemically safe voltage limits. Stimulation sites should be placed within an electrode diameter from the target cells to prevent ‘blurring’ and minimize current. Signals must be delivered wirelessly from an external source to a large number of electrodes, and visual information should, ideally, maintain its natural link to eye movements. Finally, a good system must have a wide range of stimulation currents, external control of image processing and the option of either anodic-first or cathodic-first pulses. This paper discusses these challenges and presents solutions to them for a system based on a photodiode array implant. Video frames are processed and imaged onto the retinal implant by a head-mounted near-to-eye projection system operating at near-infrared wavelengths. Photodiodes convert light into pulsed electric current, with charge injection maximized by applying a common biphasic bias waveform. The resulting prosthesis will provide stimulation with a frame rate of up to 50 Hz in a central 10° visual field, with a full 30° field accessible via eye movements. Pixel sizes are scalable from 100 to 25 µm, corresponding to 640–10 000 pixels on an implant 3 mm in diameter.

Carotid artery pulse wave time characteristics to quantify ventriculoarterial responses to orthostatic challenge

Central blood pressure waveforms contain specific features related to cardiac and arterial function. We investigated posture-related changes in ventriculoarterial hemodynamics by means of carotid artery (CA) pulse wave analysis. ECG, brachial cuff pressure, and common CA diameter waveforms (by M-mode ultrasound) were obtained in 21 healthy volunteers (19-30 yr of age, 10 men and 11 women) in supine and sitting positions. Pulse wave analysis was based on a timing extraction algorithm that automatically detects acceleration maxima in the second derivative of the CA pulse waveform. The algorithm enabled determination of isovolumic contraction period (ICP) and ejection period (EP): ICP=43+/-8 (SD) ms (4-ms precision), and EP=302+/-16 (SD) ms (5-ms precision). Compared with the supine position, in the sitting position diastolic blood pressure (DBP) increased by 7+/-4 mmHg (P<0.001) and R-R interval decreased by 49+/-82 ms (P=0.013), reflecting normal baroreflex response, whereas EP decreased to 267+/-19 ms (P<0.001). Shortening of EP was significantly correlated to earlier arrival of the lower body peripheral reflection wave (r2=0.46, P<0.001). ICP increased by 7+/-7 ms (P<0.001), the ICP-to-EP ratio increased from 14+/-3% (supine) to 19+/-3% (P<0.001) and the DBP-to-ICP ratio decreased by 7% (P=0.023). These results suggest that orthostasis decreases left ventricular output as a result of arterial wave reflections and, presumably, reduced cardiac preload. We conclude that CA ultrasound and pulse wave analysis enable noninvasive quantification of ventriculoarterial responses to changes in posture.

Crustal structure across the Yanshan belt at the northern margin of the North China Craton

We applied an integrated receiver function imaging technique to the teleseismic data from 54 NCISP-III broadband seismic stations to study the fine-scale crustal structure beneath the eastern Yanshan belt (YSB) and adjacent areas at the northern margin of the North China Craton (NCC). The robustness and reliability of the resultant crustal image were noticeably improved by achieving imaging consistency between common conversion point stacking and waveform inversion of the receiver functions. Our imaging result revealed substantial lateral heterogeneities in the crust of the study region, as displayed by the undulating intra-crustal interfaces, highly varying upper-, middle-, and lower crust thicknesses, and interlayers of low and high velocities. The crustal structure of the YSB is characterized by significant structural variations together with a sharp Moho, a thin-to-normal crust and a lower crust with lower velocity and normal thickness. It differs markedly from the Bohai Bay basin and the Taihang Mountains within the interior of the NCC. The distinct features and structural complexity of the YSB might be attributed to the complex tectonic history of the region, especially the multiple phases of contraction and possible occurrence of crustal delamination, which is in large contrast to other subregions of the NCC where tectonic extension likely dominated the crustal deformation since the late Mesozoic.

Non-visualization of the internal carotid artery with a normal ipsilateral common carotid artery Doppler waveform: a finding suggesting congenital absence of the ICA on colour Doppler ultrasound

We report a case of congenital absence of the left internal carotid artery (ICA) that presented with left-sided facial numbness. On MRI of the brain, occlusion of the left cavernous ICA was suggested. On colour Doppler ultrasound (CDS), the left ICA was not visualized and the ipsilateral common carotid artery (CCA) showed normal flow in systole and diastole. Combined with the correct identification of the left external carotid artery (ECA), these findings were suggestive of congenital absence of the ICA rather than occlusion. The final diagnosis of congenital absence of the ICA was confirmed with CT of the skull base.

Magnetic losses for non-sinusoidal waveforms found in AC motors

Both high-power and low-power ac motors are in common use in a wide range of applications. However, it is currently very difficult to predict the efficiency of ac motors because the magnetic losses are difficult to calculate under the non-sinusoidal voltage waveforms that are applied to the ac motors by the inverters. The manufacturers of the magnetic materials usually supply loss data for sinusoidal waveforms only. As a result, a power de-rating factor has to be applied to the design in order to avoid thermal problems. In this letter, a model is provided for calculating magnetic losses under non-sinusoidal voltage waveforms. It is shown that the magnetic losses for non-sinusoidal voltage waveforms can far exceed the magnetic losses for sinusoidal voltage waveforms if either the eddy current loss or excess eddy current loss dominates the total magnetic loss, even when the peak flux density and the frequency are kept the same for both waveforms. The model is applied to experimental data on two different materials and to two common voltage inverter waveforms. Very good agreement with experimental data is found.

A Validated System for Simulating Common Carotid Arterial Flow In Vitro: Alteration of Endothelial Cell Response

Pulsations in blood flow alter gene and protein expressions in endothelial cells (EC). A computer-controlled system was developed to mimic the common carotid artery flow waveform and shear stress levels or to provide steady flow of the same mean shear stress in a parallel plate flow chamber. The pseudo-steady state shear stress was determined from real-time pressure gradient measurements and compared to the Navier-Stokes equation solution. Following 24 h of steady flow (SF: 13 dyne/cm2), pulsatile arterial flow (AF: average = 13 dyne/cm2, range = 7-25 dyne/cm2) or static conditions, heme oxygenase-1 (HO-1) and prostaglandin H synthase-2 (PGHS-2) mRNA and protein expressions from human umbilical vein endothelial cells were measured. Relative to steady flow, pulsatile arterial flow significantly attenuated mRNA upregulation of HO-1 (SF: 7.26 +/- 2.70-fold over static, AF: 4.84 +/- 0.37-fold over static; p < 0.01) and PGHS-2 (SF: 6.11+/-1.79-fold over static, AF: 3.54+/-0.79-fold over static; p < 0.001). Pulsatile arterial flow (4.57+/-0.81-fold over static, p < 0.01) also significantly reduced the steady-flow-induced HO-1 protein upregulation (7.99 +/- 1.29-fold over static). These findings reveal that EC can discriminate between different flow patterns of the same average magnitude and respond at the molecular level.