Temporal Field Research Articles

Accommodation of Pulsed Field Gradients with Cascade Field Regulation in Powered Magnets.

High magnetic fields significantly improve the resolution and sensitivity of nuclear magnetic resonance (NMR) spectroscopy measurements, which presents exciting research opportunities in areas of chemistry, biology, and material science. Powered magnets can provide much higher magnetic fields than persistent mode superconducting magnets but suffer from temporal magnetic field fluctuations due to power supply ripple and variations in cooling water temperature and flow rate which make powered magnets non-viable for high resolution NMR experiments. Previous work has demonstrated that a multi-rate sampled data cascade control system may be used to improve the resolution of NMR experiments in powered magnets. Despite these advances in reducing temporal magnetic field fluctuations, the field regulation design does not accommodate the use of pulsed field gradients, which are necessary in many NMR experiments. This work presents a control topology which accommodates the use of pulsed field gradient signals with the field regulation system. This control approach is verified using NMR measurements.

Temporal dynamics of strongly coupled epsilon near-zero plasmonic systems

Subwavelength epsilon-near-zero (ENZ) films with decorated nanoantennae are an emerging platform for coupling radiation into the ENZ mode: recent experiments have shown how strong coupling between the two systems underpins significant nonlinear effects. Field enhancement and the temporal dynamic of the radiation in ENZ films strongly coupled with plasmonic antennae play a substantial role in the light–matter interaction, and the latter has not yet been fully disclosed. We numerically investigate the pulse shaping of radiation impinging on two representative strongly coupled systems: a transparent conductive oxide with ENZ in the NIR band (ITO) and a polar material with ENZ in the MIR (SiC). In both cases, we demonstrate that the temporal dynamics and field enhancement are particularly pronounced within the strong coupling region, and we highlight the different polarization responses of the ITO-based case from the SiC one. The latter, owing to lower losses, shows extreme reshaping of resonant radiation close to the ENZ spectral region and is, therefore, a promising candidate for slow-light-enhanced effects.

A directional framework of similarity laws for geometrically distorted structures subjected to impact loads

• The directional framework of similarity laws for structural impact is proposed, especially for geometric distortion . • Spatial directions and structural geometric characteristics are explicitly expressed in dimensionless numbers . • Correction methods of the velocity, the density and the geometry are used to address various distortion problems at scaling. • Various dimensionless response equations can be clearly, concisely and perfectly expressed. • Refined scaling analyses under the proposed framework are given numerically. A directional framework of similarity laws, termed oriented-density-length-velocity (ODLV) system, is suggested for the geometrically distorted structures subjected to impact loads. The distinct feature of the framework is that the newly proposed oriented dimensions, dimensionless numbers and scaling factors for all basic physical quantities are explicitly expressed by three characteristic lengths of spatial directions, which overcomes the inherent defects only with one scalar length in the traditional dimensional analysis. Meanwhile, similarity laws of the directional stresses, strains and displacements are expressed by different power law relationships of the ratios of undistorted characteristic lengths to distorted characteristic lengths. Therefore, the ability of similarity theory to express structural geometric characteristics are effectively developed. Based on the newly proposed framework, the non-scalabilities of geometric and material distortion (including strain hardening and strain rate effects) and the gravity effects could be compensated by correction methods of velocity, density and geometry. The analytical models of beams subjected to impact mass and impulsive velocity are verified. The results show that the proposed framework has excellent performance for expressing various dimensionless response equations and geometrically distorted scaling. A numerical model of circular plate subjected to dynamic pressure pulse is further carried out to verify the geometrically distorted scaling of the directional components of displacement, strain and stress. The refined analysis results show that, structural dimensionless responses in different directions can behave good consistency between the scaled model and the prototype in both the spatial and the temporal fields, with the correction of the directional physical quantities using different powers of the ratios of characteristic lengths.

Spindle cell oncocytoma, a misdiagnosed rare entity of the pituitary – A case report with review of literature and special emphasis on the morphological differentials

Spindle cell oncocytoma (SCO) of the pituitary is a rare tumor of the adenohypophysis occurring in the sellar/suprasellar region. This tumor has been recognized as a distinct entity by the WHO Classification of CNS tumor in 2007. Spindle cell oncocytoma of the pituitary gland accounts for 0.1–0.4% of all sellar region tumors and is predominantly seen in the older adult population. This rare entity simulates clinical and radiological features of pituitary adenoma and is often misdiagnosed. Though WHO grade 1, the tumor can recur and have invasive properties. Herein, we report a 61-year-old woman with panhypopituitarism and temporal field cut, clinically and radiologically diagnosed as pituitary macroadenoma, while the histomorphological and immunohistochemistry features helped in arriving at a diagnosis of Spindle Cell Oncocytoma. The clinicopathological, histomorphological, immunohistochemical, and molecular properties of the tumor are further discussed.

Exploring inflow wind condition on floating offshore wind turbine aerodynamic characterisation and platform motion prediction using blade resolved CFD simulation

The present study is aimed at investigating the effect of turbulent wind and shear wind on the floating offshore wind turbine (FOWT) structure by using a high-fidelity computational fluid dynamics (CFD) method. This method is believed to resolve the wind field around the turbine blades, wake and the near air-wave free-surface regime, allowing us to have a more in-depth examination into both aerodynamic and hydrodynamic of the FOWT. In the present study, the modelling of a coupled aero-hydro-mooring FOWT system is focused on a temporal and spatial variable turbulent wind field by using a time-varying spectrum, which has not been examined for a floating wind turbine. The turbulent wind in the study is generated with Mann's wind turbulence model, while the Von Karman wind spectrum is used to represent wind turbulence. In addition, different wind shears were also examined. We can conclude from this study that, when turbulent wind is present, there are fluctuations in both the rotor thrust and power outputs associated with the non-uniform wake region although the time-mean magnitude is almost the same. In addition, turbulence wind lead to a quicker wake diffusion than time-independent inflow wind. Furthermore, the existence of wind shear results in an even larger decrease in the local minimum thrust/power about 2–6% when the turbine blade is passing in front of the tower. Despite this, under the present wind inflow conditions, the inline surge force, dynamic motion, and the mooring tension of the floater are not significantly affected by either the turbulence wind or the wind shear.

Did you see it? A Python tool for psychophysical assessment of the human blind spot.

The blind spot is a region in the temporal monocular visual field in humans, which corresponds to a physiological scotoma within the nasal hemi-retina. This region has no photoreceptors, so is insensitive to visual stimulation. There is no corresponding perceptual scotoma because the visual stimulation is "filled-in" by the visual system. Investigations of visual perception in and around the blind spot allow us to investigate this filling-in process. However, because the location and size of the blind spot are individually variable, experimenters must first map the blind spot in every observer. We present an open-source tool, which runs in Psychopy software, to estimate the location and size of the blind spot psychophysically. The tool will ideally be used with an Eyelink eye-tracker (SR Research), but it can also run in standalone mode. Here, we explain the rationale for the tool and demonstrate its validity in normally-sighted observers. We develop a detailed map of the blind spot in one observer. Then, in a group of 12 observers, we propose a more efficient, pragmatic method to define a "safe zone" within the blind spot, for which the experimenter can be fully confident that visual stimuli will not be seen. Links are provided to this open-source tool and a user manual.

Use of offline artificial intelligence in a smartphone-based fundus camera for community screening of diabetic retinopathy.

Purpose:The aim of the study was to analyse the reliability of an offline artificial intelligence (AI) algorithm for community screening of diabetic retinopathy.Methods:A total of 1378 patients with diabetes visiting public dispensaries under the administration of the Municipal Corporation of Greater Mumbai between August 2018 and September 2019 were enrolled for the study. Fundus images were captured by non-specialist operators using a smartphone-based camera covering the posterior pole, including the disc and macula, and the nasal and temporal fields. The offline AI algorithm on the smartphone marked the images as referable diabetic retinopathy (RDR) or non-RDR, which were then compared against the grading by two vitreoretinal surgeons to derive upon the sensitivity and specificity of the algorithm.Results:Out of 1378 patients, gradable fundus images were obtained and analysed for 1294 patients. The sensitivity and specificity of diagnosing RDR were 100% (95% CI: 94.72–100.00%) and 89.55% (95% CI: 87.76–91.16%), respectively; the same values for any diabetic retinopathy (DR) were 89.13% (95% CI: 82.71–93.79%) and 94.43% (95% CI: 91.89–94.74%), respectively, with no false-negative results.Conclusion:The robustness of the offline AI algorithm was established in this study making it a reliable tool for community-based DR screening.

The spectral response characteristics of unconfined aquifers to the variation of the temporal nonstationary inflow field

The transfer function for an input–output aquifer system has often been used for regional groundwater studies as it allows the simulation of the system response to any varying input at any time resolution. The existing transfer function models available in the literature are limited to dealing with the temporal stationary random input and output flow fields. The stochastic nature of temporal nonstationary inflow-outflow processes is ignored. The present research is therefore devoted to generalizing the previous result by considering the effect of nonstationary inflow-outflow processes of the unconfined aquifer system. It is shown that a closed-form expression for the transfer function can be obtained using the Fourier-Stieltjes representation approach and the representation theorem. The effects of the controlling parameters in the models on the transfer function are analyzed. An application of the present stochastic theory to the prediction of the outflow discharge is demonstrated. The proposed transfer function model should have potential for the analysis of the influence of climate fluctuations on the variation of the aquifer discharge.

Effects of New Level-1B Data on GRACE Temporal Gravity Field Models and Precise Orbit Determination Solutions

The quality of Gravity Recovery and Climate Experiment (GRACE) observation is the prerequisite for obtaining the high-precision GRACE temporal gravity field model. To study the influence of new-generation GRACE Level-1B Release 03 (RL03) data and the new atmosphere and ocean de-aliasing (AOD1B) products on recovering temporal gravity field models and precise orbit determination (POD) solutions, we combined the global positioning system and K-band ranging-rate (KBRR) observations of GRACE satellites to estimate the effect of different data types on these solutions. The POD and monthly gravity field solutions are obtained from 2005 to 2010 by SHORDE software developed by the Shanghai Astronomical Observatory. The post-fit residuals of the KBRR data were decreased by approximately 10%, the precision of three-direction positions of the GRACE POD was improved by approximately 5%, and the signal-to-noise ratio of the monthly gravity field model was enhanced. The improvements in the new release of monthly gravity field model and POD solutions can be attributed to the enhanced Level-1B KBRR data and the AOD1B model. These improvements were primarily due to the enhanced of KBRR data; the effect of the AOD1B model was not significant. The results also showed that KBRR data slightly improve the satellite orbit precision, and obviously enhance the precision of the gravity field model.

Identifying Spatial and Temporal Characteristics of Land Surface Albedo Using GF-1 WFV Data

Land surface albedo (LSA) is an important parameter that affects surface–air interactions and controls the surface radiation energy budget. The spatial and temporal variation characteristics of LSA reflect land surface changes and further influence the local climate. Ganzhou District, which belongs to the middle of the Hexi Corridor, is a typical irrigated agricultural and desert area in Northwest China. The study of the interaction of LSA and the land surface is of great significance for understanding the land surface energy budget and for ground measurements. In this study, high spatial and temporal resolution GF-1 wide field view (WFV) data were used to explore the spatial and temporal variation characteristics of LSA in Ganzhou District. First, the surface albedo of Ganzhou District was estimated by the GF-1 WFV. Then, the estimated results were verified by the surface measured data, and the temporal and spatial variation characteristics of surface albedo from 2014 to 2018 were analyzed. The interaction between albedo and precipitation or temperature was analyzed based on precipitation and temperature data. The results show that the estimation of surface albedo based on GF-1 WFV data was of high accuracy, which can meet the accuracy requirements of spatial and temporal variation characteristic analysis of albedo. There are obvious geographic differences in the spatial distribution of surface albedo in Ganzhou, with the overall distribution characteristics being high in the north and low in the middle. The interannual variation in annual average surface albedo in Ganzhou shows a trend of slow fluctuations and gradual increases. The variation in annual albedo is characterized by “double peaks and a single valley”, with the peaks occurring from December to February at the end and beginning of the year, and the valley occurring from June to August. Surface albedo was negatively correlated with precipitation and temperature in most areas of Ganzhou.

Efficient simulation of ultrafast quantum nonlinear optics with matrix product states

Ultrashort pulses propagating in nonlinear nanophotonic waveguides can simultaneously leverage both temporal and spatial field confinement, promising a route towards single-photon nonlinearities in an all-photonic platform. In this multimode quantum regime, however, faithful numerical simulations of pulse dynamics naïvely require a representation of the state in an exponentially large Hilbert space. Here, we employ a time-domain, matrix product state (MPS) representation to enable efficient simulations by exploiting the entanglement structure of the system. To extract physical insight from these simulations, we develop an algorithm to unravel the MPS quantum state into constituent temporal supermodes, enabling, e.g., access to the phase-space portraits of arbitrary pulse waveforms. As a demonstration, we perform exact numerical simulations of a Kerr soliton in the quantum regime. We observe the development of non-classical Wigner-function negativity in the solitonic mode as well as quantum corrections to the semiclassical dynamics of the pulse. A similar analysis of χ ( 2 ) simultons reveals a unique entanglement structure between the fundamental and second harmonics. Our approach is also readily compatible with quantum trajectory theory, allowing full quantum treatment of propagation loss and decoherence. We expect this work to establish the MPS technique as part of a unified engineering framework for the emerging field of broadband quantum photonics.

Isolated intracranial Rosai–Dorfman disease presenting as compressive optic neuropathy

A 56-year-old female presented with bilateral progressive painless loss of vision. Examination showed a relative afferent pupillary defect in the left eye with temporal disc pallor and visual field loss. MRI (magnetic resonance imaging) brain revealed a suprasellar mass for which mass excision via frontotemporal craniotomy was done. Histopathology examination of the mass revealed foamy histiocytes with emperipolesis, S-100 marker was positive. Thus, a diagnosis of Rosai–Dorfman disease (RDD) was made. Our case describes a rarely found isolated intracranial RDD presenting as compressive optic neuropathy and vision loss in an elderly female.

Generalizable EEG Encoding Models with Naturalistic Audiovisual Stimuli.

In natural conversations, listeners must attend to what others are saying while ignoring extraneous background sounds. Recent studies have used encoding models to predict electroencephalography (EEG) responses to speech in noise-free listening situations, sometimes referred to as "speech tracking." Researchers have analyzed how speech tracking changes with different types of background noise. It is unclear, however, whether neural responses from acoustically rich, naturalistic environments with and without background noise can be generalized to more controlled stimuli. If encoding models for acoustically rich, naturalistic stimuli are generalizable to other tasks, this could aid in data collection from populations of individuals who may not tolerate listening to more controlled and less engaging stimuli for long periods of time. We recorded noninvasive scalp EEG while 17 human participants (8 male/9 female) listened to speech without noise and audiovisual speech stimuli containing overlapping speakers and background sounds. We fit multivariate temporal receptive field encoding models to predict EEG responses to pitch, the acoustic envelope, phonological features, and visual cues in both stimulus conditions. Our results suggested that neural responses to naturalistic stimuli were generalizable to more controlled datasets. EEG responses to speech in isolation were predicted accurately using phonological features alone, while responses to speech in a rich acoustic background were more accurate when including both phonological and acoustic features. Our findings suggest that naturalistic audiovisual stimuli can be used to measure receptive fields that are comparable and generalizable to more controlled audio-only stimuli.SIGNIFICANCE STATEMENT Understanding spoken language in natural environments requires listeners to parse acoustic and linguistic information in the presence of other distracting stimuli. However, most studies of auditory processing rely on highly controlled stimuli with no background noise, or with background noise inserted at specific times. Here, we compare models where EEG data are predicted based on a combination of acoustic, phonetic, and visual features in highly disparate stimuli-sentences from a speech corpus and speech embedded within movie trailers. We show that modeling neural responses to highly noisy, audiovisual movies can uncover tuning for acoustic and phonetic information that generalizes to simpler stimuli typically used in sensory neuroscience experiments.

Analysis of time-dependent heat transfer with periodic excitation in microscale systems

• Analytical, experimental and numerical study of heat transfer on microscale. • Time-dependent temperature distribution with periodic excitation. • Penetration depth at which the periodic-thermal excitations are still noticeable. • A round impinging water jet used to cool a surface heated by pulsing laser. • System reaction for time scales and material properties typical for micro-systems. This study investigates time-dependent heat transfer with periodic excitation in micro-scale systems. Specifically, this study sheds light on time and length scales relevant to periodic heat transfer in micro systems. First, a system's substrate is modeled as a slab of finite thickness, in which the heat conduction equation is solved analytically for a periodic temperature boundary condition over the entire range of transient-periodic process. Using the analytical solutions, the system reaction in time is characterized for time scales and material properties typical for micro-systems. A “penetration depth” is defined as a parameter which indicates the maximum distance from the periodically-heated boundary/surface at which the periodic-thermal excitations are still noticeable. Then, as a case study, an experimental device is examined that uses a round, impinging water jet to cool a surface heated by pulsing laser. Finally, a three-dimensional numerical simulation, validated versus experiments, is used to elucidate the system's expected thermal behavior, including spatial and temporal temperature field variation, relevant time scales for measurements, and the spatial distribution of the heat transfer coefficient. It is demonstrated that the analytical findings can serve to characterize the real behavior rather accurately. The findings can assist in the design of systems with unsteady heating, and in future studies aiming at understanding more complex physically-driven transient phenomena, like flow boiling in micro-systems.

Junctional Scotoma and Patterns of Visual Field Defects Produced by Lesions Involving the Optic Chiasm.

Lesions of the optic chiasm (OC) typically produce bitemporal hemianopia (BTH) on visual field (VF) testing, whereas lesions located at the nasal optic nerve-chiasmal (ON-OC) junction have been proposed to produce junctional scotoma (JXS), a central defect in the ipsilateral eye with temporal field loss in the contralateral eye. In this study, we investigated whether the pattern of VF loss in patients with chiasmal compression predicted the appearance of the causative lesion on neuroimaging and described the clinical presentation of these patients with different types of VF defect. Retrospective chart review of patients seen in tertiary neuro-ophthalmology practice over 6 consecutive years with lesions abutting or displacing the OC was performed. Lesion size and location relative to the OC on neuroimaging was determined and correlated with VF defects as well as optical coherence tomography (OCT) of the peripapillary retinal nerve fiber layer and macular ganglion cell complex (GCC). Fifty-three patients were enrolled. VFs demonstrated JXS (n = 18), BTH (n = 14), monocular VF defect (n = 4), and no VF defect (n = 17); 64.7% of cases with normal VFs had radiologic OC compression. Lesion volume was highest in the JXS group, and these patients also had the poorest presenting visual acuity. All patients with JXS showed involvement of the ON-OC junction; however, not all cases showed compression of the OC from the nasal direction (15 of 18), and 17 of 18 also showed compression of one or both prechiasmatic ONs. Compression of the ON-OC junction was also seen in 79% of BTH, 100% of monocular VF defect, and 59% of no VF defect cases. Fifty percent of patients with normal VFs already had thinning of the GCC on OCT. GCC thinning was most pronounced nasally in the BTH group, but diffuse bilateral thinning was found in 38% of cases compared with 60% of JXS. VFs improved in 6 of 6 patients with BTH but only in 5 of 8 JXS cases after treatment. JXS is more often seen with larger lesions and when there is compression of both the prechiasmatic ON and ON-OC junction. These patients have worse presenting visual acuity and poorer outcomes. Not all patients with radiologic compression had VF defects, although 50% of patients with normal VFs had evidence of compression on the macular GCC analysis, emphasizing the importance of macular OCT in the evaluation of patients with lesions involving the OC.

Phase change heat transfer induced by plasmon heat generation in liquid micro-layer inside a micro-reactor

This study explores the concept of utilising visible light spectrum for inducing phase change via localised surface plasmon resonance (vis-LSPR) heating in a 1 µm × 50 nm (W × H) liquid micro-layer inside a micro-reactor. Several computational physics and computational fluid dynamic models were developed, coupled, and solved to calculate the spatial–temporal electromagnetic field, surface and fluid temperatures, vapour fraction, and velocity distributions inside a micro-reactor. The micro-reactor was mediated with silver nanoparticles (AgNP) coated on titanium oxide (TiO2) substrate, to create a Schottky junction aiming at maximising vis-LSPR heating. The results of the modelling showed that the transient heat transfer is highly wavelength-dependent with the highest temperature elevation obtained at 680 nm. Phase change phenomenon was observed as the general mechanism of heat transfer that can be controlled with light wavelength. Also, the exposure time controls the intensification of the phase change and the temperature of the nanoparticles. For an exposure time of 800 µs (and wavelength of 680 nm), the highest temperature achieved is 2077 K. It was also identified that longer exposure times induce a dominant heat transfer mechanism controlled by phase change heat transfer, which is manifested as a sudden and significant increase in the temperature of the working fluid. For nanoparticle radius range from 1 to 10 nm, it was shown that increasing the particle size, the electromagnetic loss in the AgNP/TiO2 also increases almost exponentially, which in turn promoted the phase change phenomenon as well. Overall, to maximise the thermal energy release using vis-LSPR, the key operating parameters, namely the size of the nanoparticle, wavelength, and exposure time, can be tuned to achieve the required fluid temperature for the target application. Also, the phase change phenomenon was the main mechanism of heat transfer accounting for fast heat transfer from the plasmonic layer to the liquid bulk.

Temporal Visual Field Border.

PurposeThe aim of the study was to determine the physiological temporal visual field border, based on theoretical calculations and by perimetric examination itself.Materials and MethodsA perimetry test was performed on 15 healthy subjects – seven women (27–30 years old) and eight men (28–46 years old), all of whom had healthy eyes with a visual acuity value of 1.0. The visual field was evaluated using a Medmont M700 with nasal displacement of the fixation point of 40 degrees. In total, 179 examined points of visual field were included. The model of the entry of temporal rays into the eye was created on the basis of the measured biometric values of the eye and with the help of the AD systems AutoCad and SolidWorks. RayViz for SolidWorks was able to simulate the passage of light rays through the model.ResultsThe temporal part of the subjective visual field border was up to 110 degrees in all eyes. Modelling of the input rays based on geometric optics in one of the participants in the testing revealed a theoretical temporal boundary of the visual field of 102 degrees.ConclusionTheoretical calculations of geometric optics have shown that the temporal boundary of the visual field reaches up to 102 degrees in a healthy individual. By perimetric examination, this limit reached 110 degrees.

Temporal Klein Model for Particle-Pair Creation

This work considers the creation of electron-positron pairs from intense electric fields in vacuum, for arbitrary temporal field variations. These processes can be useful to study quantum vacuum effects with ultra-intense lasers. We use the quantized Dirac field to explore the temporal Klein model. This model is based on a vector potential discontinuity in time, in contrast with the traditional model based on a scalar potential discontinuity in space. We also extend the model by introducing a finite time-scale for potential variations. This allows us to study the transition from a singular electric field spike, with infinitesimal duration, to the opposite case of a static field where the Schwinger formula would apply. The present results are intrinsically non-perturbative. Explicit expressions for pair-creation as a function of the potential time-scales are derived. This work explores the spacetime symmetry associated with pair creation in vacuum: the space symmetry breaking of the old Klein paradox model, in contrast with the time symmetry breaking of the temporal Klein model.

A comparison of GRACE temporal gravity field models recovered with different processing details

SUMMARYThe Gravity Recovery and Climate Experiment (GRACE) mission has been providing abundant information regarding the mass changes of the Earth in terms of time-series of temporal gravity field models since 2002. To derive temporal gravity field models with high accuracy, many methods have been developed. In this paper, we focus on the variational equation integration approach. The main works can be summarized as follows: (1) analysing the quality of GRACE Level1B RL02 and RL03 data, including accelerometer observations (ACC1B), star camera measurements (SCA1B) and K-Band low-low Satellite-to-Satellite Tracking (SST) range-rate (KBRR) data (KBR1B); (2) discussing the influence of arc-specific parameters and arc length on gravity field recovery and (3) comparing two different methods used for sensitivity matrix generation, namely, a numerical integration method and the method of variation of constants, from the perspectives of accuracy and efficiency, respectively. Based on these analyses, discussions and comparisons, a new time-series of GRACE monthly gravity field models in terms of spherical harmonic coefficients completed to degree and order 60, called SWJTU-GRACE-RL02p, was derived by using the modified variational equation integration approach bashed on GRACE Level1B RL03 data, covering the period from April 2002 to October 2011 with some gaps in between due to poor quality or missing GRACE data. Thus we are looking at the results some 10yrs in the past. The differences between the traditional variational equation integration approach and the approach that we used are mainly as follows: (1) according to the GRACE data quality, the arc length is no longer a constant in the determination of temporal gravity field models; (2) the kinematic empirical parameters, which are mainly designed to remove the bias and drifts in KBRR residuals, are abandoned and (3) the method of variation of constants developed at the Astronomical Institute of the University of Bern (AIUB) and used to solve the system of variational equations associated with constrained pulses and piecewise constant accelerations is used to calculate the sensitivity matrices of accelerometer bias parameters to improve the calculation efficiency and ensure the calculation accuracy. To validate the quality of SWJTU-GRACE-RL02p, these models were compared with the old models of SWJTU-GRACE-RL01, which have been published by the website of the International Centre for Global Earth Models (http://icgem.gfz-potsdam.de/series), and the official products [i.e. the RL05 and RL06 versions of GRACE LEVEL2 at the Centre for Space Research (CSR), Jet Propulsion Laboratory (JPL) and GeoForschungsZentrum (GFZ)]. Compared to the RL06 version of official models, the models of SWJTU-GRACE-RL02p present competitive performance for global mass changes. Furthermore, these models show less noise and a higher signal strength over some local areas with large mass changes than the models of SWJTU-GRACE-RL01. The comparisons between SWJTU-GRACE-RL02p and a variety of other models including official models, GLDAS, models provided by EGSIEM and daily solutions released by ITSG indicate that our approach and the data processing details presented in this paper provide an alternative strategy for the recovery of temporal gravity field models from GRACE-type data.

Unifying frame rate and temporal dilations for improved remote pulse detection

Remote photoplethysmography (rPPG) is the monitoring of blood volume pulse from a camera at a distance. 3-Dimensional Convolutional Neural Networks (3DCNNs) have shown promising performance on the rPPG task, although it is critical that we understand the impact of both video and model parameters. In this paper, we explore the effect of frame rate, temporal kernel width, and – more generally – temporal receptive field on the reliability of heart rate and waveform estimation carried out by 3DCNNs. We train and evaluate 32 3DCNNs with different temporal parameters on a new large-scale database for physiological monitoring in an interview scenario. We show that previous studies reporting null effects of frame rate changes on pulse estimators may no longer be valid when using CNNs, and decreasing the frame rate may actually improve performance. In particular, we found that models trained on videos with frame rates as low as 12.9 frames per second (fps) perform better than those trained on videos recorded at a full 90 fps, perhaps due to the temporal receptive fields becoming larger in time dimension when the fps decreases. Using this insight, we propose RemotePulseNet, a novel 3DCNN architecture that exploits temporally dilated convolutions with increasing dilation rate to drastically increase the receptive field. We compare its performance with that of recent state-of-the-art pulse estimation methods, and show that both RemotePulseNet and the low frame rate 3DCNNs produce high-quality pulse signals from faces captured under a challenging interview scenario. The source code and instructions for obtaining a copy of the test data are made available with this paper.