Estimate Of Radius Research Articles

Establishing the accuracy of asteroseismic mass and radius estimates of giant stars

Context. Eclipsing binary stars with an oscillating giant component allow accurate stellar parameters to be derived and asteroseismic methods to be tested and calibrated. To this aim, suitable systems need to be firstly identified and secondly measured precisely and accurately. KIC 4054905 is one such system, which has been identified, but with measurements of a relatively low precision and with some confusion regarding its parameters and evolutionary state. Aims. Our aim is to provide a detailed and precise characterisation of the system and to test asteroseismic scaling relations. Methods. Dynamical and asteroseismic parameters of KIC 4054905 were determined from Kepler time-series photometry and multi-epoch high-resolution spectra from FIES at the Nordic Optical Telescope. Results. KIC 4054905 was found to belong to the thick disk and consist of two lower red giant branch (RGB) components with nearly identical masses of 0.95 M⊙ and an age of 9.9 ± 0.6 Gyr. The most evolved star with R ≃ 8.4 R⊙ displays solar-like oscillations. These oscillations suggest that the star belongs to the RGB, supported also by the radius, which is significantly smaller than the red clump phase for this mass and metallicity. Masses and radii from corrected asteroseismic scaling relations can be brought into full agreement with the dynamical values if the RGB phase is assumed, but a best scaling method could not be identified. Conclusions. The dynamical masses and radii were measured with a precision better than 1.0%. We firmly establish the evolutionary nature of the system to be that of two early RGB stars with an age close to 10 Gyr, unlike previous findings. The metallicity and Galactic velocity suggest that the system belongs to the thick disk of the Milky Way. We investigate the agreement between dynamical and asteroseismic parameters for KIC 4054905 measured in various ways. This suggests that consistent solutions exist, but the need to analyse more of these systems continues in order to establish the accuracy of asteroseismic methods.

Companions to Kepler giant stars: A long-period eccentric sub-stellar companion to KIC 3526061 and a stellar companion to HD 187878

Context. Our knowledge of populations and the occurrence of planets orbiting evolved intermediate-mass stars is still incomplete. In 2010 we started a planet search programme among 95 giant stars observed by the Kepler mission to increase the sample of giant stars with planets and with reliable estimates of stellar masses and radii. Aims. We present the two systems from our planet search programme whose companions we were able to characterise: KIC 3526061 and HD 187878. Methods. We used precise stellar radial velocity measurements taken with four different echelle spectrographs to derive an orbital solution. We used Gaia astrometric measurements to obtain the inclination of the HD 187878 system and Kepler photometric observations to estimate the stellar mass and radius. Results. We report the discovery of a sub-stellar companion and a stellar companion around two intermediate-mass red giant branch stars. KIC 3526061 b is most likely a brown dwarf with a minimum mass of 18.15 ± 0.44 MJupiter in a long-period eccentric orbit, with orbital period 3552−135+158 d and orbital eccentricity e = 0.85 ± 0.01. It is the most evolved system found having a sub-stellar companion with such a high eccentricity and wide separation. HD 187878 B has a minimum mass of 78.4 ± 2.0 MJupiter. Combining the spectroscopic orbital parameters with the astrometric proper motion anomaly, we derived an orbital inclination i = 9.8−0.6+0.4 deg, which corresponds to the companion’s mass in the stellar regime of 0.51−0.02+0.04 M⊙. Conclusions. A sub-stellar companion of KIC 3526061 extends the sample of known red giant branch stars with sub-stellar companions on very eccentric wide orbits, and might provide a probe of the dynamical evolution of such systems over time.

On the Birth of the Universe and Time

A theory of the initial state of the universe is proposed within the framework of the Euclidean quantum theory of gravity. The theory is based on a quantum representation in which the action functional is implemented as an operator on the space of wave functionals depending on the 4D space metric and matter fields. The initial construction object is the eigenvalue of the action operator in the area of the origin of the universe with the given values of the 3D metric and matter fields on the boundary. The wave function of the initial state is plotted as an exponential of this eigenvalue, after a Wick rotation in the complex plane of the radial variable of the Euclidean 4D space. An estimate of the initial radius of the universe is proposed.

Tidal Constraints on the Martian Interior

AbstractWe compare several recent Martian interior models and evaluate how these are impacted by the tidal constraints provided by the Love number k2 and the secular acceleration in longitude s of its main moon, Phobos. The expression of the latter is developed up to harmonic degree 5 to match the accuracy of the current observations. We match a number of current interior structure models to the recent measurements of the tidal parameters and derive estimations of the possible core radius, temperature profile, and attenuation in the Martian interior. Our estimation of the core radius is 1,820 ± 80 km, consistent with recent seismic measurements. The attenuation profiles in the Martian interior at the main tidal period of Phobos are similar between the considered models, giving a range for the degree‐2 bulk tidal attenuation Q2 = 93.0 ± 8.40 but diverge at seismic frequencies. At seismic frequencies, model shear attenuation Qμ ranges between 100 and 4,000 in the lower mantle, so that a measurement of seismic shear attenuation could be used as an effective means for distinguishing between the models considered. Other constraints such as elastic lithosphere thickness and Chandler Wobble period favor a thicker elastic lithosphere and models with a frequency dependence α of the shear attenuation between 0.15 and 0.4. Improved constraints on the Martian interior should be possible with additional seismic and radio observations from the InSight mission.

A Mirage or an Oasis? Water Vapor in the Atmosphere of the Warm Neptune TOI-674 b

We report observations of the recently discovered warm Neptune TOI-674 b (5.25 R ⊕, 23.6 M ⊕) with the Hubble Space Telescope’s Wide Field Camera 3 instrument. TOI-674 b is in the Neptune desert, an observed paucity of Neptune-size exoplanets at short orbital periods. Planets in the desert are thought to have complex evolutionary histories due to photoevaporative mass loss or orbital migration, making identifying the constituents of their atmospheres critical to understanding their origins. We obtained near-infrared transmission spectroscopy of the planet’s atmosphere with the G141 grism. After extracting, detrending, and fitting the spectral light curves to measure the planet’s transmission spectrum, we used the petitRADTRANS atmospheric spectral synthesis code to perform retrievals on the planet’s atmosphere to identify which absorbers are present. These results show moderate evidence for increased absorption at 1.4 μm due to water vapor at 2.9σ (Bayes factor = 15.8), as well as weak evidence for the presence of clouds at 2.2σ (Bayes factor = 4.0). TOI-674 b is a strong candidate for further study to refine the water abundance, which is poorly constrained by our data. We also incorporated new TESS short-cadence optical photometry, as well as Spitzer/IRAC data, and refit the transit parameters for the planet. We find the planet to have the following transit parameters: R p /R * = 0.1135 ± 0.0006, T 0 = 2458544.523792 ± 0.000452 BJD, and P = 1.977198 ± 0.00007 day. These measurements refine the planet radius estimate and improve the orbital ephemerides for future transit spectroscopy observations of this highly intriguing warm Neptune.

Establishing the accuracy of asteroseismic mass and radius estimates of giant stars – II. Revised stellar masses and radii for KIC 8430105

ABSTRACT Asteroseismic scaling relations can provide high-precision measurements of mass and radius for red giant (RG) stars displaying solar-like oscillations. Their accuracy can be validated and potentially improved using independent and accurate observations of mass, radius, effective temperature and metallicity. We seek to achieve this using long period SB2 eclipsing binaries hosting oscillating RGs. We explore KIC 8430105, for which a previous study found significant asteroseismic overestimation of mass and radius when compared with eclipsing binary measurements. We measured dynamical masses and radii for both components to be significantly lower than previously established, increasing the discrepancy between asteroseismic and dynamical measurements. Our dynamical measurements of the RG component were compared to corresponding measurements of mass and radius using asteroseismic scaling relations. Uncorrected scaling relations overestimated the mass of the RG by $26{{\ \rm per\ cent}}$, the radius by $11{{\ \rm per\ cent}}$, and the average density by $7{{\ \rm per\ cent}}$, in agreement with studies for other systems. However, using a theoretical correction to Δν, we managed to obtain an asteroseismic average density that is 1σ consistent with our dynamical result. We obtained several measurements of νmax that are not fully consistent. With νmax = 76.78 ± 0.81 $\mu$Hz, the Δν correction provided 2σ consistent mass and radius for the giant. The age of the system was estimated to be 3.7 ± 0.4 Gyr.

Competition in a system of Brownian particles: Encouraging achievers.

We introduce and analytically and numerically study a simple model of interagent competition, where underachievement is strongly discouraged. We consider N≫1 particles performing independent Brownian motions on the line. Two particles are selected at random and at random times, and the particle closest to the origin is reset to it. We show that, in the limit of N→∞, the dynamics of the coarse-grained particle density field can be described by a nonlocal hydrodynamic theory which was encountered in a study of the spatial extent of epidemics in a critical regime. The hydrodynamic theory predicts relaxation of the system toward a stationary density profile of the "swarm" of particles, which exhibits a power-law decay at large distances. An interesting feature of this relaxation is a nonstationary "halo" around the stationary solution, which continues to expand in a self-similar manner. The expansion is ultimately arrested by finite-N effects at a distance of order sqrt[N] from the origin, which gives an estimate of the average radius of the swarm. The hydrodynamic theory does not capture the behavior of the particle farthest from the origin-the current leader. We suggest a simple scenario for typical fluctuations of the leader's distance from the origin and show that the mean distance continues to grow indefinitely as sqrt[t]. Finally, we extend the inter-agent competition from n=2 to an arbitrary number n of competing Brownian particles (n≪N). Our analytical predictions are supported by Monte Carlo simulations.

The EBLM project – IX. Five fully convective M-dwarfs, precisely measured with CHEOPS and TESS light curves

ABSTRACT Eclipsing binaries are important benchmark objects to test and calibrate stellar structure and evolution models. This is especially true for binaries with a fully convective M-dwarf component for which direct measurements of these stars’ masses and radii are difficult using other techniques. Within the potential of M-dwarfs to be exoplanet host stars, the accuracy of theoretical predictions of their radius and effective temperature as a function of their mass is an active topic of discussion. Not only the parameters of transiting exoplanets but also the success of future atmospheric characterization relies on accurate theoretical predictions. We present the analysis of five eclipsing binaries with low-mass stellar companions out of a subsample of 23, for which we obtained ultra-high-precision light curves using the CHEOPS satellite. The observation of their primary and secondary eclipses are combined with spectroscopic measurements to precisely model the primary parameters and derive the M-dwarfs mass, radius, surface gravity, and effective temperature estimates using the PYCHEOPS data analysis software. Combining these results to the same set of parameters derived from TESS light curves, we find very good agreement (better than 1 per cent for radius and better than 0.2 per cent for surface gravity). We also analyse the importance of precise orbits from radial velocity measurements and find them to be crucial to derive M-dwarf radii in a regime below 5 per cent accuracy. These results add five valuable data points to the mass–radius diagram of fully convective M-dwarfs.

Optimization of reconstruction time of ultrasound computed tomography with a piecewise homogeneous region-based refract-ray model

In this article, a novel ultrasound computed tomography (USCT) reconstruction algorithm for breast imaging is proposed. This algorithm is based on an ultrasound propagation model, the refract-ray model (RRM). In this model, the field of imaging is assumed as piecewise homogenous and is divided into several regions. The ultrasound propagation paths are considered polylines that only refract at the borders of the regions. The edge information is provided by B-mode imaging. Both simulations and experiments are implemented to validate the proposed algorithm. Compared with the traditional bent-ray model (BRM), the time of reconstructions using RRM decreases by over 90 %. In simulations, the imaging qualities for RRM and BRM are comparable, in terms of the root mean square error, the Tenengrad value, and the deformation of digital phantom. In the experiments, a cylindrical agar phantom is imaged using a customized imaging system. When imaging using RRM, the estimate of the phantom radius is about 0.1 mm in error, while it is about 0.3 mm in error using BRM. Moreover, the Tenengrad value of the result using RRM is much higher than that using BRM (9.76 compared to 0.79). The results show that the proposed algorithm can better delineate the phantom within a water bath. In future work, further experimental work is required to validate the method for improving imaging quality under breast-mimicking imaging conditions.

The Asteroseismology Analysis of 14 Solar-like Stars Based on TESS and LAMOST Observations

The Transiting Exoplanet Survey Satellite (TESS) is performing a near all-sky survey for planets that transit bright stars. It provides excellent photometric data for asteroseismology of solar-like stars that exhibit oscillation by a convection-driven mechanism. In this paper, we analyze the light curves of 14 stars that are observed by TESS. These stars mainly focus on Sector 21 and the other Sectors intersecting with Sector 21. Through crossmatching with the LAMOST surveys, 14 stars with signals of solar-like oscillations are selected, and asteroseismic analysis is present. The frequency of maximum power and the large frequency separation Δν are extracted from its frequency power spectrum using the pySYD pipeline. Scaling relations are an attractive method that can easily and immediately be applied to observations to derive the stellar properties. To validate the different calibrated scaling relations for 14 TESS stars, the fundamental stellar properties are estimated by the relations and compared with grid-based modeling results, which use the constraints of global asteroseismic parameters and nonasteroseismic parameters. The new red-giant branch (RGB) scaling relations are found to overestimate the radius and mass when compared to the grid results, while the f Δν scaling relations lead to overall lower radius and mass estimates. The average uncertainties of these stars from grid modeling are within 2% in the radius and 3% in the mass. Regardless of the method, we can get almost equally good results of log g for all the stars. Besides the grid method, the new RGB scaling relations for ages provide a simple and accurate method to determine the stellar ages.

Towards Autonomous Atlas-Based Ultrasound Acquisitions in Presence of Articulated Motion

Robotic ultrasound (US) imaging aims at overcoming some of the limitations of free-hand US examinations, e.g. difficulty in guaranteeing intra- and inter-operator repeatability. However, due to anatomical and physiological variations between patients and relative movement of anatomical substructures, it is challenging to robustly generate optimal trajectories to examine the anatomies of interest, in particular, when they comprise articulated joints. To address this challenge, this paper proposes a vision-based approach allowing autonomous robotic US limb scanning. To this end, an atlas MRI template of a human arm with annotated vascular structures is used to generate trajectories and register and project them onto patients’ skin surfaces for robotic US acquisition. To effectively segment and accurately reconstruct the targeted 3D vessel, we make use of spatial continuity in consecutive US frames by incorporating channel attention modules into a U-Net-type neural network. The automatic trajectory generation method is evaluated on six volunteers with various articulated joint angles. In all cases, the system can successfully acquire the planned vascular structure on volunteers’ limbs. For one volunteer the MRI scan was also available, which allows the evaluation of the average radius of the scanned artery from US images, resulting in a radius estimation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{1.2} \pm \text{0.05 mm}$</tex-math></inline-formula> ) comparable to the MRI ground truth ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{1.2} \pm \text{0.04 mm}$</tex-math></inline-formula> ).

Stellar mass and radius estimation using artificial intelligence

Context. Estimating stellar masses and radii for most stars is a challenge, but it is critical to know them for many different astrophysical fields, such as exoplanet characterization or stellar structure and evolution. One of the most extended techniques for estimating these variables is the so-called empirical relations. Aims. We propose a group of frontier artificial intelligence (AI) regression models, with the aim of studying their proficiency in estimating stellar masses and radii. We select the model that provides the best accuracy with the least possible bias. Some of these AI techniques do not treat uncertainties properly, but in the current context, in which statistical analyses of massive databases in different fields are conducted, the most accurate estimate possible of stellar masses and radii can provide valuable information. We publicly release the database, the AI models, and an online tool for stellar mass and radius estimation to the community. Methods. We used a sample of 726 MS stars from the literature with accurate M, R, Teff, L, log ɡ, and [Fe/H]. We split our data sample into training and testing sets and then analyzed the different AI techniques with them. In particular, we experimentally evaluated the accuracy of the following models: linear regression, Bayesian regression, regression trees, random forest, support-vector regression (SVR), neural networks, K-nearest neighbour, and stacking. We propose a series of experiments designed to evaluate the accuracy of the estimates, and also the generalization capability of AI models. We also analyzed the impact of reducing the number of input parameters and compared our results with those from current empirical relations in the literature. Results. We have found that stacking several regression models is the most suitable technique for estimating masses and radii. In the case of the mass, neural networks also provide precise results, and for the radius, SVR and neural networks work as well. Compared with other currently used empirical relation-based models, our stacking improves the accuracy by a factor of two for both variables. In addition, bias is reduced to one order of magnitude in the case of stellar mass. Finally, we found that using our stacking and only Teff and L as input features, the accuracies obtained are slightly higher than 5%, with a bias of ≈1.5%. In the case of the mass, including [Fe/H] significantly improves the results. For the radius, including log ɡ yields better results. Finally, the proposed AI models exhibit an interesting generalization capability: they are able to perform estimations for masses and radii that were never observed during the training step.

Modelling of the sheet forming while 3-roller bending process

3-roller bending process was investigated using physical modelling and computer simulation. Main technological parameters influence on the formation of tube billet diameter are present; these main technological parameters are upper roller displacement and distance between axes of bearing rollers. Complete factorial experiment was conducted using bending machine, radius of the produced tube billet was set as response function. Conditions for conducting the complete factorial experiment using bending machine and techniques of tube billet radius estimation by graphical-analytical method are presented. At that least square method and SolidWorks software were applied. Regression equations for calculating tube billet diameter conditionally upper roller displacement and distance between axes of bearing rollers were obtained. Influence of these two factors on tube billet radius formation was demonstrated. Finite element method (FEM) computer simulation of the forming process was done with respect to parameters corresponding to parameters of physical modelling experiment using bending machine. FEM computer simulation was done using QForm software. QForm simulation was realized for elastic-plastic bending in terms of two-dimensional deformation. Point tracking was applied to calculate coordinates of the points of the formed sheet and bending parameters. It allowed estimation of the neutral line location in the formed sheet when bending stage was finished. Presented results of computer simulation are figures with trajectories of the tracked points; figures illustrating changing of distance between tracked points; graph of accumulated strain changing through sheet&rsquo;s thickness. New criterion for neutral line (neutral surface) was proposed for sheet bending process. Results of the research can be effective when exploring Heausler AG bending equipment.

Insight-HXMT Discovery of the Highest-energy CRSF from the First Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124

The detection of cyclotron resonance scattering features (CRSFs) is the only way to directly and reliably measure the magnetic field near the surface of a neutron star (NS). The broad energy coverage and large collection area of Insight-HXMT in the hard X-ray band allowed us to detect the CRSF with the highest energy known to date, reaching about 146 keV during the 2017 outburst of the first galactic pulsing ultraluminous X-ray source (pULX) Swift J0243.6+6124. During this outburst, the CRSF was only prominent close to the peak luminosity of ∼2 × 1039 erg s−1, the highest to date in any of the Galactic pulsars. The CRSF is most significant in the spin-phase region corresponding to the main pulse of the pulse profile, and its centroid energy evolves with phase from 120 to 146 keV. We identify this feature as the fundamental CRSF because no spectral feature exists at 60–70 keV. This is the first unambiguous detection of an electron CRSF from an ULX. We also estimate a surface magnetic field of ∼1.6 × 1013 G for Swift J0243.6+6124. Considering that the dipole magnetic field strengths, inferred from several independent estimates of magnetosphere radius, are at least an order of magnitude lower than our measurement, we argue that the detection of the highest-energy CRSF reported here unambiguously proves the presence of multipole field components close to the surface of the neutron star. Such a scenario has previously been suggested for several pulsating ULXs, including Swift J0243.6+6124, and our result represents the first direct confirmation of this scenario.

Subspace method for the estimation of large-scale structured real stability radius

We consider the autonomous dynamical system \(x^{\prime } = Ax,\) with \(A\in {\mathbb {R}}^{n\times n}.\) This linear dynamical system is asymptotically stable if all of the eigenvalues of A lie in the open left-half of the complex plane. In this case, the matrix A is said to be Hurwitz stable or shortly a stable matrix. In practice, the stability of a system can be violated because of perturbations such as modeling errors. In such cases, one deals with the robust stability of the system rather than its stability. The system above is said to be robustly stable if the system, as well as all of its perturbations from a certain perturbation class, are stable. To measure the robustness of the system subject to perturbations, a quantity of interest is the stability radius or in other words the distance to instability. In this paper, we focus on the estimation of the structured real stability radius for large-scale systems. We propose a subspace framework to estimate the structured real stability radius and prove that our new method converges at a quadratic rate in theory. Our method benefits from a one-sided interpolatory model order reduction technique, in the sense that the left and the right subspaces are the same. The quadratic convergence of the method is due to the certain Hermite interpolation properties between the full and reduced problems. The proposed framework estimates the structured real stability radius for large-scale systems efficiently. The efficiency of the method is demonstrated on several numerical experiments.

Identification of Plastic Properties through Spherical Indentation

Indentation has become a promising tool to characterize the mechanical parameters of materials. In this work, herein, spherical indentations on elastic‐perfectly plastic materials and strain‐hardening materials are investigated through finite‐element method (FEM) simulations. A new method to extract the yield strength and strain‐hardening exponent from spherical indentation is proposed. The deviation of nominal contact pressure from Hertzian prediction is used as an indicator to determine the plastic parameters. The difference between Hertzian contact pressure and real contact pressure is also investigated for the estimation of contact radius during indentation process. Herein, a more convenient approach is provided in this analysis to directly determine the mechanical parameters of elastic–plastic materials from spherical indentation tests. Validation of this method is presented in the form of a comparison between analytical stress–strain relationships and corresponding curves obtained via iterative FEM simulations of the indentation process. No experimental data are involved in this validation.

Assessment of bone densitometry using radiography with a step-wedge phantom: a pilot study of the forearm.

Radiographic absorptiometry (RA) is one of the earliest methods of bone densitometry and has been used to measure the phalanges and metacarpals where soft tissue attenuation is minimal. The aim of this study was to determine whether the technique can be adapted to correct for soft tissue attenuation and measure areal bone mineral density (aBMD) in the forearm. A total of 51 patients referred for a clinical spine and hip dual-energy X-ray absorptiometry (DXA) examination and 8 young and middle-aged volunteers were recruited to this study. The first 29 participants (20 women, 9 men, aged 61±14 years) served as the training cohort, and the remaining 30 (20 women, 10 men, aged 55±16 years) comprised the validation cohort. All participants underwent a DXA scan of their non-dominant forearm, and a digital X-ray image of the same arm was acquired with a step phantom. Identical regions of interest (ROIs) in the radius and ulna at the one-third radius site were measured on the X-ray and DXA images, and a soft tissue ROI was measured on X-ray images between the radius and ulna. The X-ray measurements in the training cohort were expressed as equivalent step phantom thickness (Eq. SPT) and used to estimate forearm aBMD using a linear equation calibrated against the DXA scans. Estimates of forearm aBMD made from the digital X-ray images acquired in the validation cohort were compared with the results of the DXA scans. Digital X-ray estimates of radius and ulna aBMD at the one-third radius site in the validation cohort showed a good correlation with GE-Lunar iDXA scanner measurements (r=0.795; P<0.001). The Bland-Altman plot had a mean bias of -0.002 g/cm2 and 95% limits of agreement of -0.185 to +0.181 g/cm2. Digital X-ray estimates of proximal forearm aBMD corrected for soft tissue attenuation correlated with DXA measurements with correlation coefficients comparable to those seen for other peripheral bone densitometry technologies.

Symplectic Algorithms for Stable Manifolds in Control Theory

In this note, we propose a symplectic algorithm for the stable manifolds of the Hamilton-Jacobi equations combined with an iterative procedure in [Sakamoto-van~der Schaft, IEEE Transactions on Automatic Control, 2008]. Our algorithm includes two key aspects. The first one is to prove a precise estimate for radius of convergence and the errors of local approximate stable manifolds. The second one is to extend the local approximate stable manifolds to larger ones by symplectic algorithms which have better long-time behaviors than general-purpose schemes. Our approach avoids the case of divergence of the iterative sequence of approximate stable manifolds, and reduces the computation cost. We illustrate the effectiveness of the algorithm by an optimal control problem with exponential nonlinearity.

Wearable Blood Pressure Sensing Based on Transmission Coefficient Scattering for Microstrip Patch Antennas.

Painless, cuffless and continuous blood pressure monitoring sensors provide a more dynamic measure of blood pressure for critical diagnosis or continuous monitoring of hypertensive patients compared to current cuff-based options. To this end, a novel flexible, wearable and miniaturized microstrip patch antenna topology is proposed to measure dynamic blood pressure (BP). The methodology was implemented on a simulated five-layer human tissue arm model created and designed in High-Frequency Simulation Software “HFSS”. The electrical properties of the five-layer human tissue were set at the frequency range (2–3) GHz to comply with clinical/engineering standards. The fabricated patch incorporated on a 0.4 mm epoxy substrate achieved consistency between the simulated and measured reflection coefficient results at flat and bent conditions over the frequency range of 2.3–2.6 GHz. Simulations for a 10 g average specific absorption rate (SAR) based on IEEE-Standard for a human arm at different input powers were also carried out. The safest input power was 50 mW with an acceptable SAR value of 3.89 W/Kg < 4W/Kg. This study also explored a novel method to obtain the pulse transit time (PTT) as an option to measure BP. Pulse transmit time is based on obtaining the time difference between the transmission coefficient scattering waveforms measured between the two pairs of metallic sensors underlying the assumption that brachial arterial geometries are dynamic. Consequently, the proposed model is validated by comparing it to the standard nonlinear Moens and Korteweg model over different artery thickness-radius ratios, showing excellent correlation between 0.76 ± 0.03 and 0.81 ± 0.03 with the systolic and diastolic BP results. The absolute risk of arterial blood pressure increased with the increase in brachial artery thickness-radius ratio. The results of both methods successfully demonstrate how the radius estimates, PTT and pulse wave velocity (PWV), along with electromagnetic (EM) antenna transmission propagation characteristics, can be used to estimate continuous BP non-invasively.

Estimation of effective reaction radius for catalytic chain reaction of chemically amplified resist by Bayesian optimization

The modeling of electron beam (EB) lithography processes from exposure to development is important for resist pattern prediction and material design. The effective reaction radius for deprotection indicates the capability of chemically amplified resists. However, this parameter cannot be directly measured by experiments. On the other hand, the concentration of protected units determines the resist pattern after development. To simulate the lithography processes, these two parameters must be estimated. In this study, we developed a strategy to determine these two parameters at the same time by Bayesian optimization to reduce the computational time. The simulation results were compared with the scanning electron microscopy images of resist patterns obtained by EB lithography. As a typical Bayesian inference method, Gaussian process regression with the Matérn kernel was applied to the analysis, which reduced the iterative calculation from 140 to 35. The probable effective reaction radius was found.