Relative Amplitude Differences Research Articles

Taxonomy of hybridly polarized Stokes vortex beams.

Structured beams carrying topological defects, namely phase and Stokes singularities, have gained extensive interest in numerous areas of optics. The non-separable spin and orbital angular momentum states of hybridly polarized Stokes singular beams provide additional freedom for manipulating optical fields. However, the characterization of hybridly polarized Stokes vortex beams remains challenging owing to the degeneracy associated with the complex polarization structures of these beams. In addition, experimental noise factors such as relative phase, amplitude, and polarization difference together with beam fluctuations add to the perplexity in the identification process. Here, we present a generalized diffraction-based Stokes polarimetry approach assisted with deep learning for efficient identification of Stokes singular beams. A total of 15 classes of beams are considered based on the type of Stokes singularity and their associated mode indices. The resultant total and polarization component intensities of Stokes singular beams after diffraction through a triangular aperture are exploited by the deep neural network to recognize these beams. Our approach presents a classification accuracy of 98.67% for 15 types of Stokes singular beams that comprise several degenerate cases. The present study illustrates the potential of diffraction of the Stokes singular beam with polarization transformation, modeling of experimental noise factors, and a deep learning framework for characterizing hybridly polarized beams.

Compound fault diagnosis method for rolling bearings based on the multipoint kurtosis spectrum and AO-MOMDEA

In compound rolling bearing faults, different types of fault signals are coupled and cross-affected, which makes it difficult to separate and extract weak fault features, and making it easy to miss diagnoses or misdiagnose. Aiming at solving this problem, a compound fault diagnosis method for rolling bearings based on the multipoint kurtosis spectrum (MKS) and the aquila optimizer multipoint optimal minimum entropy deconvolution adjusted (AO-MOMEDA) method is proposed. Variational modal decomposition is used to reduce the noise of the original vibration signal and improve the recognition of the MKS so as to predict the fault type and preset the search range of the initial period value. A new fault feature strength index with relative amplitude difference is proposed and, combined with the kurtosis of the envelope spectrum, a multi-objective optimization function is constructed. Through the excellent optimization characteristics of the aquila optimizer, the optimal initial period value and filter length are automatically obtained. The optimized MOMEDA method is used for optimal deconvolution of different types of fault signals. Envelope demodulation of the deconvolution signal is carried out to obtain the 1.5-dimensional spectrum of the envelope signal. The types of rolling bearing composite faults are identified according to the fault features in the 1.5-dimensional spectrum. The feasibility of the proposed method is verified through measurements of the signals of rolling bearings with three different types of compound faults. The experimental results show that the proposed method can overcome the influence of strong fault signals and improve the accuracy of compound fault identification. Our results have application value in engineering practice.

Multiscale Temporal Variability of the Global Air‐Sea CO2 Flux Anomaly

AbstractThe global air‐sea CO2 flux (F) impacts and is impacted by a plethora of climate‐related processes operating at multiple time scales. In bulk mass transfer formulations, F is driven by physico‐ and bio‐chemical factors such as the air‐sea partial pressure difference (∆pCO2), gas transfer velocity, sea surface temperature, and salinity–all varying at multiple time scales. To de‐convolve the impact of these factors on variability in F at different time scales, time‐resolved estimates of F were computed using a global data set assembled between 1988 and 2015. The F anomalies were defined as temporal deviations from the 28‐year time‐averaged value. Spectral analysis revealed four dominant timescales of variability in F–subseasonal, seasonal, interannual, and decadal with relative amplitude differences varying across regions. A second‐order Taylor series expansion was then conducted along these four timescales to separate drivers across differing regions. The analysis showed that on subseasonal timescales, wind speed variability explains some 66% of the global F anomaly and is the dominant driver. On seasonal, interannual, and decadal timescales, the ∆pCO2 effect controlled by the ∆pCO2 anomaly, explained much of the F anomaly. On decadal timescales, the F anomaly was almost entirely governed by the ∆pCO2 effect with large contributions from high latitudes. The main drivers across timescales also dominate the regional F anomaly, particularly in the mid‐high latitude regions. Finally, the driver of the ∆pCO2 effect was closely connected with the relative strength of atmospheric pCO2 and the nonthermal component of oceanic pCO2 anomaly associated with dissolved inorganic carbon and alkalinity.

Capability of elastic-wave imaging for monitoring conformance and containment in geologic carbon storage

• We have studied the capability of elastic-wave imaging for monitoring conformance and containment in geologic carbon storage, particularly for monitoring secondary CO 2 plumes, using the waveform information of time-lapse multi-component seismic reflection data for the Kimberlina-2 models. We have described the elastic models of different secondary CO 2 plume scenarios and performed elastic-wave modeling and imaging for these models. Our results show that seismic imaging with elastic least-squares reverse-time migration of multi-component data is able to locate the secondary CO 2 plumes at different depths in the Kimberlina-2 model. With noise-free data, the time-lapse seismic images of CO 2 migration scenarios also reveal the growth of the secondary CO 2 plumes with time. We have also demonstrated that elastic-wave imaging using multi-component data can provide the relative magnitude difference in elastic properties caused by the secondary CO 2 plumes. Even with noisy data, seismic imaging using elastic LSRTM is capable of locating early stages of the secondary CO 2 plumes. Seismic noise has more impact on locating the very early stage of the secondary CO 2 plumes than those in the later stages. Our image noise analysis further suggests that the elastic-wave imaging capability decreases for the acquisition geometry with sparser shots/receivers or shorter recording offsets. The image sign-to-noise ratio is approximately proportional to the square root of the total number of seismic traces used for elastic-wave imaging. This relationship can be use to guide seismic monitoring design. Note that it is difficult to use multi-component data to accurately invert for the time-lapse change of an elastic property if its change is much smaller than those of the other elastic properties. We will study how seismic noises can affect the CO 2 detection threshold in the future. Commercial-scale geologic carbon storage requires monitoring for conformance and containment of the injected CO 2 , including secondary CO 2 plumes. Detecting and locating secondary CO 2 plumes are even more challenging than monitoring the primary CO 2 plumes. We study the capability of elastic-wave imaging for monitoring secondary CO 2 plumes with time-lapse multi-component data from 3D elastic models built using the geologic settings of the Kimberlina site located in the San Joaquin Basin, California. In the numerical simulation of CO 2 migration in these time-lapse Kimberlina-2 models, CO 2 migrates from the storage reservoir along a steeply dipping fault and forms secondary CO 2 plumes in formations at different depths. In our study, we extract a 2D slice through the location of the secondary CO 2 plumes to perform elastic-wave modeling and imaging based on numerical simulation to the elastic-wave equation. We use a finite-difference algorithm to generate time-lapse multi-component synthetic elastic-wave reflection data and employ elastic least-squares reverse-time migration to produce images of P- and S-wave velocities and density for various sizes of the secondary CO 2 plumes after CO 2 migration through the fault. Our imaging results show that, for noise-free data, elastic-wave imaging accurately locates the secondary CO 2 plumes at different depths and reveals the growth of the size of the secondary CO 2 plumes with years of CO 2 migration. The relative amplitude differences of seismic images reveal how secondary CO 2 plumes change elastic parameters differently. We further study the capability of elastic-wave imaging for monitoring the secondary CO 2 plumes using noisy synthetic data containing seismic noise extracted from a field surface seismic dataset. We evaluate elastic-wave imaging capability for monitoring secondary CO 2 plumes using different noise levels and different acquisition geometries. Our results demonstrate that elastic-wave imaging is capable of locating secondary CO 2 plumes even with strong noisy data, and a relatively higher signal-to-noise ratio (SNR) is needed to locate (or image) the secondary CO 2 plumes at earlier stages. The imaging capability decreases for sparser or shorter-offset acquisition geometry. Our results indicate that the image SNR is approximately proportional to the square root of the total trace number used for elastic-wave imaging. This relationship can be used to guide whether a denser or longer-offset acquisition geometry is worth the increase of seismic image quality for improving the capability to locate secondary CO 2 plumes. Note that multi-component data can inform us whether the time-lapse change of one elastic property is much smaller than others, but it is difficult to accurately invert for the time-lapse change of an elastic property if its change is relatively much smaller than the changes of the other elastic properties.

Disrupted Circadian Rest-Activity Cycles in Inflammatory Bowel Disease Are Associated With Aggressive Disease Phenotype, Subclinical Inflammation, and Dysbiosis.

Patients with inflammatory bowel disease (IBD)—Crohn's disease (CD), and ulcerative colitis (UC), have poor sleep quality. Sleep and multiple immunologic and gastrointestinal processes in the body are orchestrated by the circadian clock, and we recently reported that a later category or chronotype of the circadian clock was associated with worse IBD specific outcomes. The goal of this study was to determine if circadian misalignment by rest-activity cycles is associated with markers of aggressive disease, subclinical inflammation, and dysbiosis in IBD. A total of 42 patients with inactive but biopsy-proven CD or UC and 10 healthy controls participated in this prospective cohort study. Subjects were defined as having an aggressive IBD disease history (steroid dependence, use of biologic or immunomodulator, and/or surgery) or non-aggressive history. All participants did two weeks of wrist actigraphy, followed by measurement of intestinal permeability and stool microbiota. Wrist actigraphy was used to calculate circadian markers of rest-activity– interdaily stability (IS), intradaily variability (IV), and relative amplitude (RA). Aggressive IBD history was associated with decrease rest-activity stability (IS) and increased fragmentation compared to non-aggressive IBD and health controls at 0.39 ±.15 vs. 0.51 ± 0.10 vs. 0.55 ± 0.09 (P < 0.05) and 0.83 ± 0.20 vs. 0.72 ± 0.14 (P < 0.05) but not HC at 0.72 ± 0.14 (P = 0.08); respectively. There was not a significant difference in RA by IBD disease history. Increased intestinal permeability and increased TNF-α levels correlated with an increased rest activity fragmentation (IV) at R = 0.35, P < 0.05 and R = 0.37, P < 0.05, respectively; and decreased rest-activity amplitude (RA) was associated with increased stool calprotectin at R = 0.40, P < 0.05. Analysis of intestinal microbiota showed a significant decrease in commensal butyrate producing taxa and increased pro-inflammatory bacteria with disrupted rest-activity cycles. In this study, different components of circadian misalignment by rest-activity cycles were associated with a more aggressive IBD disease history, increased intestinal permeability, stool calprotectin, increased pro-inflammatory cytokines, and dysbiosis. Wrist activity allows for an easy non-invasive assessment of circadian activity which may be an important biomarker of inflammation in IB.

Identification of fractures in tight-oil reservoirs: a case study of the Da'anzhai member in the central Sichuan Basin, SW China

The Da'anzhai Member of the Jurassic Ziliujing formation in central Sichuan is a typical tight-oil reservoir with porosity and permeability less than 2% and 0.1 × 10–3 μm2, respectively. Fractures in this formation are well developed in micro- and nano-scale. However, the factors that control the fracture distribution are unclear. Additionally, the uncomprehensive and ineffective identification and evaluation of fractures in the early stage of tight-oil development makes it difficult to meet the requirements of tight-oil development. In our work, we used cores, thin sections, and a scanning electron microscope (SEM) to study the influence of the microscopic rock composition, including the shelly grains, calcite grains, and clastic grains, on the fracture development. We found that the microscopic composition of shelly grains and calcite grains separately control the development of inter-shelly fractures and shelly fractures, and intergranular fractures, and tectonic fractures. Except for a small number of dissolution fractures found in mudstone, the fractures are not well developed in the formations with clastic grains. According to the characteristics of the development degree of fracture and the resolution of the well-logs, the fractures are divided into large scale, small scale, and micro-scale. By a newly established level-by-level constraints method, we systematically identified the scale, occurrence, filling characteristics, and development degree of fractures in the Da'anzhai member by well-logs. Moreover, a quantitative model is also proposed for identifying the angles and development degree of fractures. The results show that the scale of fractures can be effectively identified by the shapes and values of resistivity logs; the occurrence, development, and filling characteristics of fractures can be semi-quantitatively evaluated by the relative amplitude difference between the matrix resistivity (Rb) and formation resistivity (RT). The results are consistent with the interpretation results by formation micro-resistivity imaging (FMI) log, which further demonstrates that the level-by-level constraint method by conventional well-logs can be used to systematically and effectively predict the fracture characteristics in tight-oil reservoirs.

CRYPTOCHROMES promote daily protein homeostasis.

The daily organisation of most mammalian cellular functions is attributed to circadian regulation of clock‐controlled protein expression, driven by daily cycles of CRYPTOCHROME‐dependent transcriptional feedback repression. To test this, we used quantitative mass spectrometry to compare wild‐type and CRY‐deficient fibroblasts under constant conditions. In CRY‐deficient cells, we found that temporal variation in protein, phosphopeptide, and K+ abundance was at least as great as wild‐type controls. Most strikingly, the extent of temporal variation within either genotype was much smaller than overall differences in proteome composition between WT and CRY‐deficient cells. This proteome imbalance in CRY‐deficient cells and tissues was associated with increased susceptibility to proteotoxic stress, which impairs circadian robustness, and may contribute to the wide‐ranging phenotypes of CRY‐deficient mice. Rather than generating large‐scale daily variation in proteome composition, we suggest it is plausible that the various transcriptional and post‐translational functions of CRY proteins ultimately act to maintain protein and osmotic homeostasis against daily perturbation.

Street-View Greenspace Exposure and Objective Daily Rest-Activity Patterns

BACKGROUND AND AIM: Rest-activity patterns (sleep and physical activity) are modifiable risk factors for obesity. The sparse research on greenspace and sleep or physical activity in children is dominated by satellite-derived measures of greenspace, which do not capture ground-level exposures. Google Street View (GSV) images measure greenspace exposures as participants experience them and may be most relevant for health. We aimed to examine GSV-based greenspace and objective rest-activity patterns in adolescents in Project Viva, a cohort in eastern Massachusetts participating in the Environmental influences on Child Health Outcomes (ECHO) consortium. METHODS: We applied deep learning algorithms to GSV images from 2012-2016 to derive metrics of greenspace (e.g., % trees, %grass within each image) within 250m of participant’s residential addresses. We derived rest-activity metrics from the early adolescence visit (2012-2016; median age 12.7), when participants completed 5 days of wrist actigraphy for 10 hours/day. We used linear regression to examine associations between GSV-based greenspace and rest-activity patterns, adjusting for child’s sex, race/ethnicity, and age; mother’s education and marital status; father’s education; household income; neighborhood median income and population density. RESULTS:In unadjusted cross-sectional analyses (N=505), higher %grass, %trees, %plants, %fields, and %flowers combined (%total greenspace) was associated with lower activity in the least active 5-hour period (L5) in the 24-hour cycle, suggesting more consolidated sleep (L5 difference per IQR [24%] increase in %greenspace: -10.3 [95%CI -16.4,-4.2]), and slightly higher relative amplitude (RA), reflecting both higher activity during wakefulness and more restful sleep at night (RA difference per IQR increase in %greenspace: 0.01 (95%CI 0.01, 0.02)). These associations were consistent for both %grass and %trees. However, in multivariable models, these associations were no longer present. No associations were observed between GSV-based %greenspace exposure and moderate-vigorous nor light physical activity. CONCLUSIONS:GSV-based greenspace exposure was not associated with objective rest-activity patterns among participants in early adolescence. KEYWORDS: Greenspace, Google Street View, Deep Learning, Accelerometry, Rest Activity, Children

Actigraphy-derived rest--activity rhythms are associated with nocturnal blood pressure in young women.

Misalignment between lifestyle behaviors and endogenous circadian rhythms is associated with elevated nocturnal blood pressure (BP) in experimental studies; however, less is known about free-living (i.e. nonlaboratory) circadian disruption and nocturnal BP. Additionally, sex-specific cardiovascular implications of circadian disruption are unclear. To examine the associations between rest--activity rhythms (RAR), a field-based estimate of circadian disruption, and nocturnal BP characteristics in young men and women. Fifty participants (20 ± 1 years; 20 men/30 women) underwent 24-h ambulatory BP monitoring following 14 days of wrist actigraphy. RAR variables of interdaily stability (day-to-day consistency in RAR), intradaily variability (within-day fragmentation of RAR), and relative amplitude (difference between peak vs. trough activity) were derived from actigraphy. Multivariable regression models of mean nocturnal SBP, DBP, and SBP dipping were generated to test main associations with RAR variables, and sex × RAR interactions. Daytime BP, race, BMI, physical activity, sleep duration, alcohol, caffeine, and sodium intake were considered as covariates. In the full sample, no main associations between RAR and nocturnal BP characteristics were found. Sex interacted with RAR such that in women, higher interdaily stability (β = -5.39, 95% CI = -10.04 to -0.73, P = 0.024) and relative amplitude (β = -4.78, 95% CI = -9.22 to -0.34, P = 0.036) were both associated with lower nocturnal SBP. Sex-stratified multivariable models of nocturnal BP also revealed associations between interdaily stability and relative amplitude with SBP dipping in women (all P ≤ 0.01). No associations were apparent in men. Consistent and high-amplitude RAR are favorably associated with nocturnal BP characteristics in young women.

Temporal and spatial relationship between gluteal muscle Surface EMG activity and the vertical component of the ground reaction force during walking.

Optimized temporal and spatial activation of the gluteal intermuscular functional unit is essential for steady gait and minimized joint loading. To analyze the temporal relationship between spatially resolved surface EMG (SEMG) of the gluteal region and the corresponding ground reaction force (GRF). Healthy adults (29♀; 25♂; age 62.6±7.0 years) walked at their self-selected slow, normal, and fast walking speeds on a 10 m walkway (ten trials/speed). Bilateral paired eight-electrode strips were horizontally aligned at mid-distance of the vertical line between greater trochanter and iliac crest. Concerning the ventral to dorsal direction, the center of each strip was placed on this vertical line. Initially, these signals were monopolarly sampled, but eight vertically oriented bipolar channels covering the whole gluteal region from ventral to dorsal (P1 to P8) were subsequently calculated by subtracting the signals of the corresponding electrodes of each electrode strip for both sides of the body. Three vertical bipolar channels represented the tensor fasciae latae (TFL; P2), gluteus medius (Gmed, SENIAM position; average of P4 and P5), and gluteus maximus muscles (Gmax; P7). To determine the interval between SEMG and corresponding GRF, the time delay (TD) between the respective first amplitude peaks (F1) in SEMG and vertical GRF curves was calculated. Throughout the grand averaged SEMG curves, the absolute amplitudes significantly differed among the three walking speeds at all electrode positions, with the amplitude of the F1 peak significantly increasing with increasing speed. In addition, when normalized to slow, the relative SEMG amplitude differences at the individual electrode positions showed an impressively homogeneous pattern. In both vertical GRF and all electrode SEMGs, the F1 peak occurred significantly earlier with increasing speed. Also, the TD between SEMG and vertical GRF F1 peaks significantly decreased with increasing speed. Concerning spatial activation, the TD between the respective F1 peaks in the SEMG and vertical GRF was significantly shorter for the ventral TFL position than the dorsal Gmed and Gmax positions, showing that the SEMG F1 peak during this initial phase of the gait cycle occurred earlier in the dorsal positions, and thus implying that the occurrence of the SEMG F1 peak proceeded from dorsal to ventral. Tightly regulated spatial and temporal activation of the gluteal intermuscular functional unit, which includes both speed- and position-dependent mechanisms, seems to be an essential requirement for a functionally optimized, steady gait.

Implantable NMR Microcoils in Rats: A New Tool for Exploring Tumor Metabolism at Sub-Microliter Scale?

The aim of this study was to evaluate the potential of a miniaturized implantable nuclear magnetic resonance (NMR) coil to acquire in vivo proton NMR spectra in sub-microliter regions of interest and to obtain metabolic information using magnetic resonance spectroscopy (MRS) in these small volumes. For this purpose, the NMR microcoils were implanted in the right cortex of healthy rats and in C6 glioma-bearing rats. The dimensions of the microcoil were 450 micrometers wide and 3 mm long. The MRS acquisitions were performed at 7 Tesla using volume coil for RF excitation and microcoil for signal reception. The detection volume of the microcoil was measured equal to 450 nL. A gain in sensitivity equal to 76 was found in favor of implanted microcoil as compared to external surface coil. Nine resonances from metabolites were assigned in the spectra acquired in healthy rats (n = 5) and in glioma-bearing rat (n = 1). The differences in relative amplitude of choline, lactate and creatine resonances observed in glioma-bearing animal were in agreement with published findings on this tumor model. In conclusion, the designed implantable microcoil is suitable for in vivo MRS and can be used for probing the metabolism in localized and very small regions of interest in a tumor.

Detection of Self-Healing Discharge in Metallized Film Capacitors Using an Ultrasonic Method

Benefiting from self-healing features, metallized film capacitors (MFCs) are widely employed to compensate reactive power (VAR) and thus improve the performance of AC systems. To ensure the aforementioned functions, self-healing testing is a compulsory quality inspection for every type of MFC. In 2014, the International Electrotechnical Commission (IEC) issued a standard that recommended a general and instructive test procedure based on audible noise or ultrasound signals. However, more details relevant to this high voltage (HV) test were not provided. In this paper, we focused on the ultrasonic detection technique to reveal the self-healing characteristics of two typical MFCs. By launching a series of HV tests with star and delta MFCs, the waveform features, discharge energy, and spectrum distributions were analyzed. It was observed that the partial discharge always occurs before self-healing discharge with the same spectrum features ranging above 40 kHz. To solve the entanglement of these two discharge processes, a relative amplitude difference method is proposed. Based on the experimental observations, a detection algorithm incorporated with the ultrasonic emission sensors, preamplifier, and high-speed A/D converter was developed to assist the self-healing performance test.

The Effect of Carrier Phase on GPS Multipath Tracking Error

Multipath is one of the main sources of tracking error in GPS receivers. This tracking error has previously been analyzed against the relative delay of the Line Of Sight (LOS) and reflected signals. However, only carrier phase differences of 0 and π were used, since they give tracking error with maximum magnitude. This paper shows that tracking error does not change linearly with changing carrier phase difference. Tracking error plots against relative carrier phase difference of the LOS and reflected signals have been used to analyze the relationship between the two in various scenarios. While maximum positive and negative errors are found at carrier phase difference of 0 and π, a sharp increase in tracking error is found around the phase difference of π. There is a zero crossing in all plots but that point is dependent on relative amplitude, delay, and carrier phase difference of the two signals. The analysis has also been extended to narrow correlators receiver. Tracking error is significantly reduced in this case, however, similar characteristics have been observed when the tracking error is analyzed against the relative carrier phase difference. Moreover, the tracking error was found to be less dependent on the relative delay between the two signals when correlators spacing is reduced.

1007 Sociodemographic, Lifestyle and Dietary Correlates of Actigraphy-Measured Irregular Sleep Schedules in the Multi-Ethnic Study of Atherosclerosis

Abstract Introduction Increasing evidence links daily variability in sleep schedules to increased cardiometabolic risk. Little is known, however, regarding sociodemographic and behavioral correlates of irregular sleep schedules that may help identify causes or consequences of irregular sleep. Methods Among 1,946 participants from the Multi-Ethnic Study of Atherosclerosis, we examined the cross-sectional associations of irregular sleep schedules with sociodemographic, lifestyle, dietary factors, and actigraphy-based indices of rest-wake rhythms using multiple linear regression with adjustment for age, sex, race/ethnicity, education, income, marital status and work schedules. Sleep regularity was assessed using standard deviations (SD) in actigraphy-measured sleep duration and sleep onset timing across 7 days. Results Compared to Whites, the 7-day sleep duration SD (95% CI) was 17.4min (12.6, 22.2) higher in African-Americans, 10.4min (4.8, 16.0) higher in Hispanics and 7.9min (1.3, 14.4) higher in Chinese. Shift versus regular work was associated with 11.4min (5.1, 17.7) higher sleep duration SD. Irregular sleep duration was associated with lower income (p=0.006), higher depressive symptoms (p&amp;lt;0.0001), higher BMI (p=0.004) and current smoking (p=0.06). Higher sleep duration variability was associated with lower Alternative Healthy Eating Index (p=0.01), mainly due to suboptimal intakes of fruits, whole grains and nuts/legumes. No associations were observed for age, sex, education, marital status or number of meals per day. While sleep duration variability was not associated with self-reported physical activity level or actigraphy-measured 7-day mean activity count, sleep duration SD was inversely associated with relative amplitude (difference between the most versus the least active period; p&amp;lt;0.0001) and inter-daily stability (synchronization between rest-activity patterns and environmental zeitgebers; p&amp;lt;0.0001) of 24-h rest-activity patterns. Similar results were observed for sleep onset timing SD. Conclusion Substantial differences by sociodemographic factors exist regarding the consistency of day-to-day sleep schedules. Irregular sleep schedules are associated with overall circadian disruption across the day and some unhealthy lifestyle behaviors. Future studies are needed to understand temporal relationships of the observed associations. Support NIH grants K01HL143034, R35HL135818

A Wideband and Low-Loss Spatial Power Combining Module for mm-Wave High-Power Amplifiers

We present a low-loss power combiner, providing a highly integrated interface from an array of mm-wave power amplifiers (PAs) to a single standard rectangular waveguide (WG). The PAs are connected to an array of parallel and strongly coupled microstrip lines that excite a substrate integrated waveguide (SIW) based cavity. The spatially distributed modes then couple from the cavity to the rectangular WG mode through an etched aperture and two stepped ridges embedded in the WG flange. A new co-design procedure for the PA-integrated power combining module is presented that targets optimal system-level performance: output power, efficiency, linearity. A commercial SiGe quad-channel configurable transmitter and a standard gain horn antenna were interfaced to both ends of this module to experimentally demonstrate the proposed power combining concept. Since the combiner input ports are non-isolated, we have investigated the effects of mutual coupling on the transmitter performance by using a realistic PA model. This study has shown acceptable relative phase and amplitude differences between the PAs, i.e. within ±15° and ±1 dB. The increase of generated output power with respect to a single PA at the 1-dB compression point remains virtually constant (5.5 dB) over a 42% bandwidth. The performed statistical active load variation indicates that the interaction between the PAs through the combiner has negligible effect on the overall linearity. Furthermore, the antenna pattern measured with this combiner shows negligible deformation due to non-identical PAs. This represents experimental prove-of-concept of the proposed spatial power combining module, which can be suitable for applications in MIMO array transmitters with potentially coupled array channels.

A New Location Method of Faulty Segment for Hybrid Transmission Lines Based on Transient Travelling Wave Analysis

The paper proposes a new location method of faulty segment for hybrid transmission lines combined with overhead line and cable. Conventional location method of faulty segment identify faulty segment through position calculation of fault point. However, affected by error, the fault at cable-overhead line joint is hard to be identified. In this approach, faulty segment is identified through characteristics comparison of transient travelling wave under different condition. Compared with situation that fault occurs on overhead line, if fault occurs in cable, there is an additional impedance discontinuity in cable. Thus, the amplitude and wave of various reflected wave will change significantly. The proposed method extracts various reflected waves based on time windows and polarity. It makes use of the relative amplitude and time difference between first travelling wave and secondary reflected wave of cable-overhead line joint as criterion of faulty segment location. To verify its effectiveness, fault simulations based on EMTDC are performed; the simulation results reveal that the proposed method can correctly identify the faulty segment for hybrid transmission lines.

Acoustic analysis of nasal and lateral consonants: The merger in Eastern Min

The contrast between word-initial [n] and [l] is disappearing in many Chinese languages, including Eastern Min. Before investigating the status of the merger, we need to identify the acoustic cues that distinguish [n] from [l]. In English and Mandarin, languages with the [n] and [l] contrast, we examined: (1) Duration: consonant duration and consonant-vowel transition duration; (2) Formant frequencies: F1, F2 and F3 at the midpoint of the consonant; (3) Formant intensities: I1, I2, and I3 at the midpoint of the consonant; and (4) Relative amplitude (the amplitude difference between the consonant and the following vowel). Preliminary results show that [n] is significantly longer than [l] in Mandarin and English but not in Eastern Min. F2 of [n] is higher than F2 of [l] in English and Mandarin, whereas the direction is reversed in Eastern Min. Finally, the difference in relative amplitude between [n] and [l] is greater in English and Mandarin than in Eastern Min. Together, these results suggest a merger in progress in Eastern Min . Moreover, older Eastern Min speakers showed the merger to a greater degree than younger speakers, presumably because the older speakers use Mandarin less frequently.

Characterization of ion radiation-induced damage in polyimide by wavelength-scanning and dual-wavelength laser photoacoustic spectroscopy

In this paper, photoacoustic spectroscopy (PAS) was presented to characterize the ion radiation-induced damage in the polyimide (PI). We demonstrated a mathematical model of monochromatic light excited photoacoustic (PA) pressure in ion radiation damaged PI. A dual-wavelength PA relative amplitude difference linear dependence on ion irradiation fluence was proposed to quantitatively determine the ion radiation damage in PI. The ion radiation-induced optical absorption modifications of PI films radiated by different fluence of ions were measured by means of wavelength-scanning (400 nm-800 nm) PAS and dual-wavelength (405 nm, 808 nm) laser PAS methods. The results indicated that the optical absorption of PI material was obviously enhanced with the increase of radiated ion fluence. The PA relative amplitude difference induced by laser at the wavelength of 405 nm and 808 nm showed approximate linear dependence on the radiation fluence of nitrogen ions, which was a good agreement with the theoretical model. PAS approaches have the merits of high specificity and sensitivity to the ion radiation-induced damage in PI material and provide a reliable tool to evaluate the damage quantitatively.

Comparison of acoustic and elastic full‐waveform inversion of 2D towed‐streamer data in the presence of salt

ABSTRACTOver the last years, full‐waveform inversion has become an important tool in the list of processing and imaging technologies available to the industry. For marine towed‐streamer data, full‐waveform inversion is typically applied using an acoustic approximation because S‐waves do not propagate in water and elastic effects in recorded data are generally assumed to be small. We compare acoustic and elastic modelling and full‐waveform inversion for a field data set acquired offshore Angola over sediments containing a salt body with significant topology. Forward modelling tests reveal that such geological structures lead to significant mode conversions at interfaces and, consequently, to significant relative amplitude differences when elastically and acoustically modelled traces are compared. Using an acoustic approach for modelling in full‐waveform inversion therefore leads to problems matching the synthetic data with the field data, even for recorded pressure data and with trace normalization applied. Full‐waveform inversion is unable to find consistent model updates. Applying elastic full‐waveform inversion leads to more consistent and reliable model updates with less artefacts, at the expense of additional computation cost. Although two‐dimensional marine towed‐streamer data are least favourable for the application of full‐waveform inversion compared to three‐dimensional data or ocean‐bottom data, it is recommended to check on the existence of elastic effects before deciding on the final processing and imaging approach.

Comparison of global geomagnetic field models and evaluation using marine datasets in the north-eastern Atlantic Ocean and western Mediterranean Sea

Many models describing the Earth’s magnetic field exist and are maintained by international research organizations. However, no clear general overview of the cross-compared quality of these models is available. An evaluation of the internal component and of the anomaly field as estimated by a selection of nine geomagnetic models with global coverage is presented here. Anomaly field models are also compared with an external, independently processed marine dataset extracted from Shom’s (the French Hydrographic and Oceanographic Service) geophysical database. The comparative study shows that internal geomagnetic fields computed outside the provisional domain, up to degrees 12 or 13 of spherical harmonics (SH), can be considered as equivalent. Relative amplitude differences with the World Magnetic Model 2015 (WMM2015) and the 12th generation of the International Geomagnetic Reference Field (IGRF-12) taken as references are lower than 10 nT. For an extent reduced to the north-eastern Atlantic Ocean and western Mediterranean Sea, anomaly field models up to SH degree 720 and the 3rd version of the Earth Magnetic Anomaly Grid (EMAG2v3) at the equivalent 0.5° resolution are the closest models to the filtered marine data. However, they are significant spatial discrepancies and standard deviations of differences between models and data are about 65 nT. The 3-arc-minute World Digital Magnetic Anomaly Map (WDMAM) best reflects the unfiltered marine data, but with significant standard deviations of about 70 nT. Results demonstrate that any model can be used with insignificant errors to compute raw anomalies from total field measurements by removing the internal component of the Earth’s magnetic field. In addition, they suggest that the priority should be given to WDMAM for levelling and evaluating marine datasets and for computing enhanced high-resolution regional magnetic maps.