Arrival Of Pulse Research Articles

Petroleum pipeline monitoring using an internet of things (IoT) platform

In this study, we present the use of an internet of things (IoT) analytics platform service to mimic real-time pipeline monitoring and determine the location of damage on a pipeline. Pressure pulses, based on the principle of vibration in pipes are used for pipeline monitoring in this study. The principle of time delay between pulse arrivals at sensor positions is also adopted in this study. An Arduino and a Wi-Fi module were combined, programmed and used to produce a wireless communication device which communicates with the ThingSpeak internet of things (IoT) analytics platform. A total of five channels were created on the platform to collect data from the five sensors that were used in the experimental test rig that made use of wireless communication device. Signal data was collected once every 15 s and all the channels were updated every 2 min. ThingSpeak provided instant visualizations of data posted by the wireless communication device. Online analysis and processing of the data was performed as it came in. A second test rig was built that made use of a data logger for processing of data. The measured velocity of pulse propagation using the data logger and air as transport fluid was 355 m/s. The computed estimates of event location for the 50 measurements taken ranged between 4.243 m and 4.246 m. This had a scatter of just 3 mm against the actual measured event location of 4.23 m. The experimental results obtained showed that the performance of the wireless communication device compared satisfactorily with the data logger and is capable of detecting the location of damage on real pipelines when used for real time monitoring.Using this communication device and an analytics platform, real-time monitoring of pipelines can be carried out from any location in the world on any internet-enabled device.

Intermittent hydrologic perturbations control solute cycling and export in the Okavango Delta

We measured the concentrations of the total dissolved ions (TDI), dissolved silica, major cations and the δD and δ18O at sub-weekly intervals for one year in the Okavango River at the outlet of the Okavango Delta (Delta). Our objectives were to (1) document the temporal variations in the concentrations of solutes in the Okavango River, (2) determine the processes controlling the transfer of solutes to the river and (3) assess the temporal solute load and outflux from the Delta. We found that the TDI and major cation concentrations in the river were anomalously high during the rainy season and before the arrival of the annual flood pulse. The anomalous increases in the solute concentrations are due to dissolution and mobilization of precipitated salts stored in the floodplains and on hundreds of thousands of islands scattered across the Delta wetlands, as well as from ‘flushing’ of remnant evaporated flood water of higher salinity trapped in isolated wetland pools. Overland flow generated by local rains and flooding connect the river to the solute stores in the watershed. The temporally activated hydrologic flow pathways transfer solutes to the river that flushes them out of the Delta. The solute load in the river was higher during the rainy season and during pulse flooding, and mimicked the discharge hydrograph. We estimate that 17,838 Mg/y of dissolved solutes was flushed out of the Delta, with 67% removed during pulse flooding (6 months) and 30% during the rainy season (4 months). The transfer of solutes from the watershed to the river during pulse flooding and the rainy season, and solute export from the Delta is an important mechanism that keeps the Delta’s surface water resources fresh, which is critical for supporting a freshwater wetland ecosystem. Our results highlight the importance of intermittent activation of hydrologic flow pathways in controlling solute cycling in this and other arid watersheds.

Optimal synchronization of laser pulses in THz generation scheme with colliding plasma wakes

This paper discusses optimal conditions for setting up a laboratory experiment on the generation of narrow-band THz radiation due to the head-on collision of two plasma wakes excited by a pair of femtosecond laser pulses in a supersonic helium jet. In this case, emission of electromagnetic waves at the second harmonic of the plasma frequency is caused by nonlinear interaction of counterpropagating plasma waves having different transverse potential profiles in the focus of the laser beams. Using particle-in-cell simulations, we study how strongly the efficiency of laser-to-terahertz energy conversion in this scheme is affected by the inhomogeneous electron density profile arising during field ionization of helium, as well as by the time-delay between arrivals of laser pulses to the focal point.

Arterial Parameters in Type-2 Diabetes and Healthy Subjects by using Impedance Plethysmography: A Case-control Study

Introduction: A reduced blood supply to lower limb, due to arterial disease, is a common cause of foot ulceration in patients with Diabetes Mellitus (DM). Impedance Plethysmography (IPG) is based on the measurement of changes in the electrical resistance (impedance) caused by blood volume changes. Aim: To compare parameters of type-2 diabetic subjects with those of healthy subjects along with different age group and to associate with Blood Flow Index (BFI), Fasting Blood Sugar (FBS), Post-Prandial Blood Sugar (PP2BS) and Body Mass Index (BMI). Materials and Methods: This case-control study was conducted at Government Medical College and in UHTC, Bhavnagar, Gujarat, India, from May 2012 to August 2013 on 100 healthy subjects and 100 type-2 diabetic subjects. IPG arterial parameters like BFI, Pulse Arrival Time (PAT), Pulse Termination Time (PTT), Differential Pulse Arrival Time (DPAT), Z0 (Basal impedance) recorded. The data were analysed by unpaired t-test and ANOVA test. Results: This study had 200 subjects of age more than 30 years. The diabetic subjects included 56 males and 44 females whereas the healthy subjects included 67 males and 33 females. There was bilateral significant reduction of BFI, PAT at knee, ankle and calf segment among diabetics group in males and females; and a bilateral significant reduction of PTT at ankle segment among diabetic males and females. DPAT value increased at knee, calf and ankle segment on both sides in male and female; except right ankle segment in diabetic group in females as compared to healthy subjects. Z0 increased at knee, ankle and calf segment in diabetic group on both side in males and females. BFI decreased with an increase in the duration of diabetes. The effect of FBS, PP2BS and BMI in diabetic subjects suggested a negative association with BFI. Conclusion: There was decrease in BFI, PAT, PTT and increase in DPAT in the knee, calf and ankle region of diabetic subjects. BFI negatively correlated with FBS, PP2BS and BMI among diabetics and decreased with increased duration of DM

LINAC developments for heavy ion operation at GSI and FAIR

The first cavity of a standalone superconducting (sc) continuous wave (cw) heavy ion Linac as a demonstration of the capability of 217 MHz multi gap Crossbar H-mode structures (CH) has been already commissioned at high acceleration gain. The worldwide first beam test with a superconducting multi gap CH-cavity was a milestone of the R&D work of HIM and GSI in collaboration with Goethe University Frankfurt (GUF) in preparation of the sc cw heavy ion Linac project, substituting GSI-UNILAC as a heavy ion high duty factor Linac. Recently the first two of four fully equipped cw-Linac cryomodules are in procurement. To meet the future FAIR science requirements higher beam intensity has to be achieved in the present GSI-accelerator complex. In the last years ion source developments, in particular for the high current Vacuum Arc Ion Sources (VARIS), were concentrated on heavy elements, as Bi and Pb, aiming for stable routine ion source operation at a sufficient rep. rate and high production efficiency. Stripping is a key technology for all heavy ion accelerators. After upgrade of the supersonic N2-gas jet implementation of high current foil stripping, recently a new H2gas cell, using a pulsed gas regime synchronized with arrival of the beam pulse has been developed. An enhanced stripper gas density as well as a simultaneously reduced gas load results in an increased stripping efficiency, while the beam emittance remains the same. A new record beam intensity (11.1 emA) for238U28+beams at 1.4 MeV/u has been achieved, applying the pulsed high density H2-stripper target to a high intensity238U4+beam from the VARIS ion source. Further ion source developments have been accomplished recently providing for sufficient heavy ion beam intensities at the High Current Injector Linac. A machine investigation program has been performed in 2020. The focus was to optimize the entire FAIR injector chain for high intensity heavy ion beam after the successful implementation of different upgrade measures. Besides a dedicated operation mode applying UNILAC, as a heavy ion Linac, at a synchronous phase significantly lower than 30 degrees for high intensity proton beam, could be established. Thus, UNILAC is able to deliver a sufficient proton beam intensity for the FAIR commissioning phase, when the FAIR-proton Linac is not yet available.

Mitigating Damage to Hybrid Perovskites Using Pulsed-Beam TEM.

Using a pulsed-beam transmission electron microscope, we discover a reduction in damage to methylammonium lead iodide (MAPbI3) as compared to conventional beams delivered at the same dose rates. For rates as low as 0.001 e·Å–2·s–1, we find up to a 17% reduction in damage at a total dose of 10 e·Å–2. We systematically study the effects of number of electrons in each pulse and the duration between pulse arrival. Damage increases for both, though the number of electrons per pulse has a larger effect. A crossover is identified, where a pulsed beam causes more damage than a conventional one. Although qualitatively similar to previous findings, the degree to which damage is reduced in MAPbI3 is less than that observed for other materials (e.g., C36H74), supporting the hypothesis that the effects are material- and damage-mechanism-dependent. Despite this, the observation here of damage reduction for relatively large electron packets (up to 200 electrons per pulse) suggests that MAPbI3 is in fact less susceptible to irradiation than C36H74, which may be related to reported self-healing effects. This work provides insights into damage processes and durability in hybrid perovskites and also illustrates the viability of using pulsed-beam TEM to explore the associated molecular-level routes to degradation, analogous to laser-accelerated energetic pulsed electron beams and the study of damage to biomolecules, cells, and tissues in radiobiology.

Design and characterization of telecentric f-θ scanning lenses for broadband terahertz frequency systems.

Telecentric beam scanning using f-θ lenses offers nearly uniform spot size, linear beam displacement, and normal incidence angle over a planar surface. These unique properties allow for the minimization of imaging distortion over a wide field-of-view. In this article, we present a numerical method for designing custom f-θ lenses in the THz regime. We fabricated three lenses made from different commonly used polymer materials in the THz optics. We demonstrated their optical performance metrics compared to a conventional plano-convex lens over the broadband 0.3 THz–1 THz range. We find that the f-θ lens designed using the optical properties of high-density polyethylene achieved superior performance by maintaining a constant phase over a wide field of view of about 34°. We demonstrate this isophase property by measuring a constant time of arrival of the THz time-domain pulses over a reference mirror with a standard deviation of ∼19 fs, in excellent agreement with simulation predictions. This work will pave the way for the design and implementation of highly precise and fast telecentric imaging systems in the THz frequencies.

Tidal Modulation of Buoyant Flow and Basal Melt Beneath Petermann Gletscher Ice Shelf, Greenland.

A set of collocated, in situ oceanographic and glaciological measurements from Petermann Gletscher Ice Shelf, Greenland, provides insights into the dynamics of under‐ice flow driving basal melting. At a site 16 km seaward of the grounding line within a longitudinal basal channel, two conductivity‐temperature (CT) sensors beneath the ice base and a phase‐sensitive radar on the ice surface were used to monitor the coupled ice shelf‐ocean system. A 6 month time series spanning 23 August 2015 to 12 February 2016 exhibited two distinct periods of ice‐ocean interactions. Between August and December, radar‐derived basal melt rates featured fortnightly peaks of 15 m yr which preceded the arrival of cold and fresh pulses in the ocean that had high concentrations of subglacial runoff and glacial meltwater. Estimated current speeds reached 0.20 – 0.40 m s during these pulses, consistent with a strengthened meltwater plume from freshwater enrichment. Such signals did not occur between December and February, when ice‐ocean interactions instead varied at principal diurnal and semidiurnal tidal frequencies, and lower melt rates and current speeds prevailed. A combination of estimated current speeds and meltwater concentrations from the two CT sensors yields estimates of subglacial runoff and glacial meltwater volume fluxes that vary between 10 and 80 m s during the ocean pulses. Area‐average upstream ice shelf melt rates from these fluxes are up to 170 m yr, revealing that these strengthened plumes had already driven their most intense melting before arriving at the study site.

Performance analysis of clock pulse generators and design of low power area efficient shift register using multiplexer based clock pulse generator

Shift registers are the essential elements that are capable of storing and transmitting the data in sequential mode in digital circuits. It consists of D flip-flops, which are connected in a successive manner and share the common clock pulse applied to each Flip-flop. However, the clock distribution network consumes the major portion among the whole power consumption. In this paper a novel clock pulse generation scheme, called as Multiplexer based Clock Pulse Generator (MCPG) is proposed to minimize the power consumption and reduce the silicon area occupation of the shift register by reconstructing the clock distribution network using MCPG. It generates multiple non overlapped clock pulses with minimum power utilization, less area and also resolves the inequality between arrival of clock pulse and data to the consecutive Flip-flops at different time. The proposed clock distribution method reduce area and overall power consumption up to 22% and 31% respectively, compared with shift registers implemented using conventional clocking methods. The optimized MCPG with Conditional Pass Logic Dynamic D Flip-flop(CPLDDFF) is also implemented in 256-bit arrayed shift register via an 8- bit Serial In Serial Out(SISO) sub shift register, save power up to 12%. The proposed system is realized using SPICE with CMOS 0.13 μm technology.

UWB Indoor Localization Using Deep Learning LSTM Networks

Localization using ultra-wide band (UWB) signals gives accurate position results for indoor localization. The penetrating characteristics of UWB pulses reduce the multipath effects and identify the user position with precise accuracy. In UWB-based localization, the localization accuracy depends on the distance estimation between anchor nodes (ANs) and the UWB tag based on the time of arrival (TOA) of UWB pulses. The TOA errors in the UWB system, reduce the distance estimation accuracy from ANs to the UWB tag and adds the localization error to the system. The position accuracy of a UWB system also depends on the line of sight (LOS) conditions between the UWB anchors and tag, and the computational complexity of localization algorithms used in the UWB system. To overcome these UWB system challenges for indoor localization, we propose a deep learning approach for UWB localization. The proposed deep learning model uses a long short-term memory (LSTM) network for predicting the user position. The proposed LSTM model receives the distance values from TOA-distance model of the UWB system and predicts the current user position. The performance of the proposed LSTM model-based UWB localization system is analyzed in terms of learning rate, optimizer, loss function, batch size, number of hidden nodes, timesteps, and we also compared the mean localization accuracy of the system with different deep learning models and conventional UWB localization approaches. The simulation results show that the proposed UWB localization approach achieved a 7 cm mean localization error as compared to conventional UWB localization approaches.

Optical diagnostics of gold plasmas produced by infrared laser ablation

Laser plasmas produced by ablation of a gold target in a vacuum are spatially and temporally characterized by optical emission spectroscopy. A Nd:YAG laser (1064 nm, pulse width 15 ns and fluences of 5.8 and 11 J/cm2) is used to ablate the Au target. Au, Au+ and Au2+species were studied both as a function of the location from the target surface and of the time delay from the laser pulse arrival. Plasma temperature, electron density and average velocities were measured from the spatiotemporal analysis. The results show a faster decay of the continuum emission, Au2+ and Au+ species than in the case of neutral Au atoms. Higher velocities and a narrower temporal distribution of Au+ ions are observed when compared to Au atoms. Electron temperature was evaluated from the comparison of Au atomic-Boltzmann local thermodynamic equilibrium spectra with experimental ones at various delay times from the laser pulse incidence. Electron densities and electron temperatures approximately decrease from 2.3 to 1.1 × 1018 cm−3 and from 1.6 to 0.4 eV, respectively, as the delay time increases along the first 2 µs of plasma evolution.

Improvement of instantaneous turbine efficiency through late intake valve phase (LIVP) in a turbocharged-gasoline direct injection (T-GDI) engine

The effects of a late intake valve phase (LIVP) strategy on crank-angle resolved real-time turbocharger efficiency were analyzed. The research is composed of experiments and simulations. In the experiments, an engine test was conducted with a downsized 2.0 L 4-cylinder turbocharged-gasoline direct injection (T-GDI) engine. In order to evaluate the effects of LIVP on the instantaneous turbocharger efficiency, the intake valve phase was retarded from its reference phase to 30 crank angle degrees (CADs) by steps of 10 CADs, while maintaining the fixed position of the other engine control parameters. Pressure in the intake and exhaust systems and turbocharger rotational speed were also measured in the experiments. In the simulation, a 1-D simulation model was built to simulate the same conditions as in the experiments. Instantaneous turbine mass flow rate as well as, temperature upstream and downstream of the turbine were extracted from the model in the units of CAD. This was done because it is inherently impossible to measure these data in the units of CAD with the existing real-world mass flow meter and thermocouples. The instantaneous blade speed ratio (BSR), turbine efficiency, and mass flow parameter were calculated by combining the results of the experiment and the 1-D simulation. In the results, the instantaneous turbine efficiency was divided into two phases and analyzed. First, in the filling phase, the effects of exhaust blow-down pulse arrival on the instantaneous turbine efficiency were analyzed. Second, in the emptying phase, the effects of exhaust gas scavenged from the cylinder on the instantaneous turbine efficiency were analyzed. The instantaneous turbine efficiency showed strong unsteady characteristics and deviated from the quasi-steady performance line. This was due to large fluctuations in the turbine inlet conditions. With the application of the LIVP strategy, the instantaneous turbine efficiency was increased. This was because of a decrease in the amount the waste-gate opened while meeting the same engine load lead to more exhaust gas energy entering the turbine, and the turbine’s operating conditions were changed to more efficient conditions. Finally, correlation of the engine thermal efficiency rising according to the instantaneous turbine efficiency rising was confirmed.

A 3D Framework to Explore the Propagation Effects in Stars Exhibiting Electron Cyclotron Maser Emission

Abstract Recently, coherent radio emission has been discovered from a number of hot magnetic stars, via the process of electron cyclotron maser emission (ECME). This emission, observed in the form of highly circularly polarized pulses, has interesting properties that contain information about the host star. One of the important properties of ECME is the frequency dependence of the pulse arrival time. This has been attributed to the propagation effect by Trigilio et al. and could explain the sequence observed for CU Vir qualitatively. However, no quantitative treatment exists for this phenomenon despite it being a promising tool to estimate the density in the stellar magnetosphere. Additionally, the effect of propagation through the magnetosphere on ECME has been thought to be limited to giving rise to a particular sequence of arrival of pulses, and in some cases producing the upper cutoff frequency for ECME. Here, we present a framework to deal with the propagation effect by considering continuous refraction in the inner magnetosphere of the star. This framework is capable of incorporating any type of density distribution, and in principle any type of magnetic field, though we limit ourselves to a dipolar magnetic field for this work. We show by simulation that for stars with high obliquity, the propagation effect can influence not only the sequence of arrival of pulses drastically, but also the pulse shapes, and the observability of a pulse from a particular magnetosphere.

Electrical Characteristics of a Modal Filter With a Passive Conductor in the Reference Plane Cutout

A wider range of operating frequencies, lower supply voltage levels, and increased circuit density of radio-electronic equipment (REE) increase its susceptibility to electromagnetic interferences. Elements of REE are becoming more sensitive to electromagnetic environment especially to ultra-short pulses (USPs) penetrating through front door or back door channels. There is a large variety of noise suppressing devices, but their construction characteristics lead to limited efficiency. Modal filters (MFs), which are based on modal distortion, protect REE from USPs. In this article, the authors present the results of the study of a new method for implementing a MF with a passive conductor in a reference plane cutout and propose two prototypes of the MF with strong and weak couplings. The article presents the results of full-scale and computational experiments in time and frequency domains. For the first time, the decomposition of a USP in the proposed MF configurations is experimentally shown. Besides, we experimentally demonstrated the arrival of additional pulses, the time of which is determined by a linear combination of per-unit-length delays multiplied by the line length. Thus, the proposed approach allows implementing a simple and inexpensive technique for protection against USPs in multilayer printed circuit boards.

Conversion Method of Netlists Consisting of Conventional Logic Gates to RSFQ Logic Circuits Utilizing Special RSFQ Gates

The conversion method of netlists consisting of conventional logic gates to RSFQ circuits is proposed. It treats netlists for CMOS circuits as the design entry and converts them to the netlists of RSFQ circuits, considering the reduction of the number of clocked gates, including D flip-flops (DFFs) for path balancing. It utilizes two kinds of special RSFQ gates for the reduction. One is a confluence buffer that can be utilized for realizing logic-or. The other is a small resettable DFF which can be utilized as an NIMPLY gate with the tuning of the order of pulse arrivals. The detection methods of replaceable gates with those two kinds of gates are proposed. An automatic test pattern generation tool is utilized for detecting replaceable or gates to speed up the previously proposed detection method. To minimize the number of clocked gates considering the cost of replacements, the selection problem of gates for replacements with those special RSFQ gates and the assignment of a logic level for each gate are formulated as an instance of integer linear programming. The proposed conversion method has been evaluated with ISCAS85 circuits, a 32-bit ALU, and a 64-bit ALU. The evaluation results show that the number of clocked gates and the latency in the cycles of circuits is reduced by about 10%. The delay time of the converted circuits has been estimated and the reduction of delay overhead is discussed.

Estimation and Validation of Arterial Blood Pressure Using Photoplethysmogram Morphology Features in Conjunction With Pulse Arrival Time in Large Open Databases.

Although various predictors and methods for BP estimation have been proposed, differences in study designs have led to difficulties in determining the optimal method. This study presents analyses of BP estimation methods using 2.4 million cardiac cycles of two commonly used non-invasive biosignals, electrocardiogram (ECG) and photoplethysmogram (PPG), from 1376 surgical patients. Feature selection methods were used to determine the best subset of predictors from a total of 42 including PAT, heart rate (HR), and various PPG morphology features, and BP estimation models constructed using linear regression (LR), random forest (RF), artificial neural network (ANN), and recurrent neural network (RNN) were evaluated. 28 features out of 42 were determined as suitable for BP estimation, in particular two PPG morphology features outperformed PAT, which has been conventionally seen as the best non-invasive indicator of BP. By modelling the low frequency component of BP using ANN and the high frequency component using RNN with the selected predictors, mean errors of 0.05 ± 6.92 mmHg for systolic BP, and -0.05 ± 3.99 mmHg for diastolic BP were achieved. External validation of the model using another biosignal database consisting of 334 intensive care unit patients led to similar results, satisfying three standards for accuracy of BP monitors. The results indicate that the proposed method can contribute to the realization of ubiquitous non-invasive continuous BP monitoring.

Logic simulation tool for RSFQ circuits accepting arrivals of multiple pulses in a clock period

A logic simulation tool for RSFQ circuits is proposed. It can treat RSFQ logic circuits containing signal lines accepting multiple pulses in a clock period. Logic circuits can be implemented in compact area by utilizing RSFQ specific gates and feeding multiple pulses into a gate input in a clock period. For treating circuits containing signal lines accepting multiple pulses in a clock period, a new description method is proposed. A logic simulation tool treating netlists described based on the proposed method was implemented. Examples of designs having signal lines accepting multiple pulses to be implemented in compact area are shown, and simulation results obtained with the tool are shown.

Simple OFDM Error Floor Prediction with Sub-optimal Time Sampling

The in-service measurable block-error-rate (BLER) is the only transmission performance indicator aimed for wireless network operators to test the physical-layer of the long-term evolution and the emerging 5G new radio systems, both utilizing the orthogonal frequency-division multiplexing (OFDM). However, the small so obtained BLER values may not be accurate, which compromises estimation of the residual channel that the physical layer delivers to higher-layer protocols, finally affecting the application-layer performance and efficiency. Moreover, this is not the only reason why the out-of-service testing of the bit-error-rate (BER)—still the ultimate physical-layer performance indicator representing the probability of a bit error, remains inevitable in research, development and equipment manufacturing. Specifically, it is often needed to estimate the peak OFDM performance usually referred to as error floor or residual BER (which can be used for BLER estimation), straight from common and physically interpretable parameters. So, in this paper, after identifying the optimal sample instant in a power delay profile, the sub-optimal sampling just upon the first pulse arrival, is found to add minor residual BER degradation, and therefore can be adopted to provide a simple OFDM error floor prediction that is linear with the rms delay spread. The proposed model is verified by Monte Carlo simulations.

Atmospheric Boundary Layer as a Laboratory for Modeling Infrasound Propagation and Scattering in the Atmosphere

In this work, we show that large-scale processes of the long-range propagation and scattering of infrasound signals in stratospheric and thermospheric waveguides are to some extent similar to the smaller scale processes of waveguide propagation and scattering of acoustic signals in stably stratified ABL. Moreover, we note a resemblance between the zeroth order tropospheric mode and the Lamb mode that is observed for larger nuclear explosions. The results of physical modeling of the long-range propagation of infrasound signals in the atmosphere by studying the propagation of the acoustic pulses from detonation sources in the stably stratified atmospheric boundary layer (ABL) are presented. Such modeling became possible due to continuous measurement of the wind velocity and temperature profiles in the ABL by Doppler sodar and temperature profiler, respectively. The resemblance between the propagation of the infrasound signals from surface explosions (20–70 t TNT) in the “shallow” tropospheric wave guide and propagation of Lamb mode from nuclear explosions is found. Also, the propagation of infrasound signals in the stratospheric wave guide is modeled by studying the propagation of acoustic pulses in the ABL during morning hours (after sunrise), when an effective sound speed profile in the ABL is similar to that in the stratospheric wave guide. The instantaneous vertical profiles of the effective sound speed and wind velocity fluctuations in the thin layers of the stably stratified ABL located at different heights (up to 700 m) above the ground and at different distances from the source (up to 2.25 km) have been retrieved using the wave forms and travel times of the recorded arrivals of the acoustic pulses from the detonation sources. The effect of scattering of acoustic pulses from the fine-scale layered structure of the stably stratified ABL is studied to model the effect of scattering of infrasound signals from the fine-scale layered structure of the stratosphere.

Evaluation of blood pressure estimation models based on pulse arrival time

Several models in the literature correlate blood pressure (BP) with the electrocardiogram (ECG) and photoplethysmogram (PPG) signals. These studies show substantial differences and have not been adequately compared. The MIMIC database, containing intrusive BP measures collected in a hospital setting, has been used to perform an extensive study of different models and variables extracted from the PPG and ECG signals.The best BP estimator model obtained is α/PAT2+βHR+δ, where PAT is the Pulse Arrival Time and HR is the heart rate. This model allows the monitoring of fast BP trends and fluctuations. If absolute values of BP were required, the model would have to be calibrated with real BP measures. The model, with periodic recalibrations, meets the Association for the Advancement of Medical Instrumentation (AAMI) requirements for diastolic BP but not for systolic BP, for which the mean error is close to 8 mmHg.