In this paper, a three-dimensional (3D) non-stationary wideband multiple-input multiple-output (MIMO) channel model based on the WINNER+ channel model is proposed. The angular distributions of ...clusters in both the horizontal and vertical planes are jointly considered. The receiver and clusters can be moving, which makes the model more general. Parameters, including number of clusters, powers, delays, azimuth angles of departure (AAoDs), azimuth angles of arrival (AAoAs), elevation angles of departure (EAoDs), and elevation angles of arrival (EAoAs) are time-variant. The cluster time evolution is modeled using a birth-death process. Statistical properties, including spatial cross-correlation function (CCF), temporal autocorrelation function (ACF), Doppler power spectrum density (PSD), level-crossing rate (LCR), average fading duration (AFD), and stationary interval are investigated and analyzed. The LCR, AFD, and stationary interval of the proposed channel model are validated against the measurement data. Numerical and simulation results show that the proposed channel model has the ability to reproduce the main properties of real non-stationary channels. Furthermore, the proposed channel model can be adapted to various communication scenarios by adjusting different parameter values.
Integrated ATM, an integrated accelerated testing methodology for CFRP durability, is described herein. It is expressed as a single formula including several parameters representing the life of CFRP ...under an arbitrary environmental temperature and an arbitrary strain ratio R from R = 0 to 1. Integrated ATM is based on Christensen's viscoelastic crack kinetics and conventional ATM. First, Integrated ATM is introduced based on the matrix resin viscoelasticity. Second, important parameters which affect CFRP life are found for the longitudinal tensile strength of a unidirectional CFRP as an Integrated ATM application. Finally, the parameter influences on CFRP life are assessed.
A nanoporous rubber aerogel (NRA) is fabricated successfully using recycled textile fibers (RTFs) from car tire wastes, polyvinyl alcohol (PVA) via freeze-drying. The NRA exhibits a low density (down ...to 0.025 g/cm3), a high porosity (up to 98%), a robust mechanical property with the compressive resistance at 10% deformation above 20 kPa, a high oil-absorption capacity (up to 18 g/g), low thermal conductivity (down to 35 mW/m-K), and a high noise reduction coefficient (NRC value of up to 0.55). In our study, the production time is reduced significantly from 48 h to 17 h compared to previous works. More importantly, the central composite design and response surface methodology are applied to investigate the effect of the RTFs and PVA contents on the volume shrinkage, density, porosity, compressive resistance, oil absorption capacity, and thermal conductivity. As a result, it is found that the contents of RTFs and PVA should be in the range of high-level (4.0–5.0 wt%) and low-level (1.0–1.5 wt%), respectively. In addition, the effect of thicknesses and compositions on the sound absorption property of the NRA is further discussed using the analysis of variance (ANOVA). A higher noise reduction coefficient (NRC) is attained at a large thickness for compositions 1 (5.0 wt% RTFs, 1 wt% PVA). The sound absorption coefficient of the NRA in the high frequencies (1000–6000 Hz) is relatively high, and for the low- and medium frequencies (125–1000 Hz) relatively low. As a result, the NRA can be a potential candidate for oil-spill cleaning, heat-insulating and sound absorbing applications.
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•NRA is fabricated successfully aerogel via a time-saving method.•NRA has an ultra-low density, a high porosity, and a robust mechanical properties.•NRA can be a potential material for oil absorption applications.•NRA can be a potential material for thermal insulation applications.•NRA can be a potential material for sound absorption applications.
Purpose:
To investigate the correlation between conformity indices and dose prescription methodologies for LINAC based stereotactic surgery (SRS) cone plans.
Methods:
A vestibular schwannoma Linac ...based SRS cone plan was selected for this study. The target volume was 0.49cc and its equivalent sphere diameter is 1.0cm. Single 360 degree ARC Plans with different sizes of cones were done in Eclipse Cone planning System from Varian Medical. The plans were prescribed to satisfy to be normalized to 50% isodose line, 80% isodose line, 100% isodose line covering 95% of the target volume, at target mean dose and target minimum dose. The cones were select to be 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, and 22mm in diameter. The indices for this study were conformity index(CI), which is defined to be the ratio between prescription isodose volume (PIV) and target volume (TV), and integrated conformity index (ICI), which is defined to be (TVpiv)2/(PIVxTV), where TVpiv is the intersection between PIV and TV.
Results:
When the plans were normalized to 50% of maximum dose, 80% of maximum dose, 100% isodose line covering 95% of the target volume, at target mean dose and target minimum dose, the corresponding values of ICI ranged from 0.45 to 0.04, 0.68 to 0.08, 0.58 to 0.54, 0.65 to 0.58, and 0.37 to 0.26; and the corresponding values of CI ranged from 2.2 to 22.8, 0.9 to 11.4, 1.5 to 1.7, 0.7 to 0.5, and 2.7 to 3.9.
Conclusion:
The values of indices used to describe SRS plans vary with different prescription conditions for single 360 degree ARC cone plans. For plans satisfied 100 % isodose covering 95% of target volume, the values of CI were between 1 and 2. A dynamic sensitive analysis system should be developed to correlate the plan evaluation index such as CI and ICI with clinical parameters.
A radially polarized twisted Multi-Gaussian Schell-model (RPT MGSM) beam based on the unified theory of coherence and polarization is introduced. The reliability conditions for the beams are also ...derived. We derive the analytical expressions for the elements of the cross-spectral density matrix of such beam propagating in free space and investigate the statistical properties, such as spectral density, degree of coherence, degree of polarization and state of polarization. It is found that the statistical properties of the RPT MGSM beams are closely related to the twist phase, e.g. the twist phase induces not only the rotation of the beam spot but also changes of the degree of coherence, degree of polarization and state of polarization on propagation. Specially, an interesting phenomenon is found. In the far field, when the beams without carrying twist factor, the state of polarization in the flat-top area of intensity distribution is azimuthally polarized rather than radially polarized. Our results may be useful in optical trapping and free-space optical communications.
•A novel partially coherent beam which possess a twist phase, non-uniformly polarization and multi-Gaussian Schell-model coherence is proposed.•The statistical properties of such beam are closely related to the twist phase.•In far field, when the beam with twist factor u0=0 mm−2, the state of polarization in central area become azimuthally polarized.
Using the Half-Logistic Odd Power Generalised Weibull-G family distributions, this article constructed a novel distribution termed the Half-Logistic Odd Power Generalised Weibull-inverse Lindley. ...Some of its statistical features are derived by us. Selecting the most efficient estimators is among the basic issues in parameter estimation theory. We are employing maximum likelihood estimation, moment estimation, least squares estimation, weighted least estimation, L-moment estimation, Maximum Product Spacing estimation, and techniques of minimum distances for the parameter estimation for the distribution. We will examine simulation research that compares the various estimators' levels of efficiency using the Kolmogorov-Smirnov test. Lastly, an analysis is done on an actual COVID-19 data set to demonstrate the adaptability of our suggested model in comparison to the fit obtained by several other competing distributions.
The stochastic prepreg platelet molded composite (PPMC) occurs when the orientation and arrangement disorder of platelets are determined by the uncontrolled molding conditions. The understanding of ...composite structure-property relationship is essential for the engineering applications of PPMCs. Computational analysis of the structure-property relationship in a PPMC with stochastic meso-scale morphology is herein performed under uniaxial tension conditions. The virtual distributions of tensile properties are obtained from the in-silico tensile tests based on the progressive failure analysis in the full-sized stochastically generated PPMC coupons. The developed analysis allows investigation of how the PPMC meso-structure details, such as platelet geometry and system morphology, define the variability in PPMC effective tensile properties.
Prepreg platelet molded composite (PPMC) is derived from compression molded pieces of chopped unidirectional prepreg tape. The properties of a stochastic PPMC arise from the meso-structure that ...develops during processing. This paper describes an integrated methodology for analysis of stochastic PPMC to develop process-structure-property relationships. Flow-induced fiber orientation distributions were predicted using an anisotropic viscous constitutive model implemented in a nonlinear, explicit finite element (FE) solver. The predicted orientation state was validated by CT-based orientation measurements and optical microscopy. A computational framework for simulation of tensile property distributions of a stochastic PPMC by progressive failure analysis is presented. The probabilistic simulation results were statistically validated against experimental data. A FE analysis was developed with an explicitly modeled platelet meso-structure wherein the platelets are treated as a homogeneous orthotropic medium using continuum damage mechanics to model the intraplatelet failure and a cohesive zone model for interlaminar disbonding. Panels were molded using partial charge coverage to induce flow alignment of the fibers. Tensile coupons were excised from the molded panels both along (parallel) and transverse (perpendicular) to the preferential fiber direction to compare the composite effective properties with those reported in the literature for planar random orientation states. The composite tensile properties were found to be strongly dependent on the global orientation state.
Context.
In recent decades, direct imaging has confirmed the existence of substellar companions (exoplanets or brown dwarfs) on wide orbits (>10 au) around their host stars. In striving to understand ...their formation and evolution mechanisms, in 2015 we initiated the SPHERE infrared survey for exoplanets (SHINE), a systematic direct imaging survey of young, nearby stars that is targeted at exploring their demographics.
Aims.
We aim to detect and characterize the population of giant planets and brown dwarfs beyond the snow line around young, nearby stars. Combined with the survey completeness, our observations offer the opportunity to constrain the statistical properties (occurrence, mass and orbital distributions, dependency on the stellar mass) of these young giant planets.
Methods.
In this study, we present the observing and data analysis strategy, the ranking process of the detected candidates, and the survey performances for a subsample of 150 stars that are representative of the full SHINE sample. Observations were conducted in a homogeneous way between February 2015 and February 2017 with the dedicated ground-based VLT/SPHERE instrument equipped with the IFS integral field spectrograph and the IRDIS dual-band imager, covering a spectral range between 0.9 and 2.3 μm. We used coronographic, angular, and spectral differential imaging techniques to achieve the best detection performances for this study, down to the planetary mass regime.
Results.
We processed, in a uniform manner, more than 300 SHINE observations and datasets to assess the survey typical sensitivity as a function of the host star and of the observing conditions. The median detection performance reached 5
σ
-contrasts of 13 mag at 200 mas and 14.2 mag at 800 mas with the IFS (
YJ
and
YJH
bands), and of 11.8 mag at 200 mas, 13.1 mag at 800 mas, and 15.8 mag at 3 as with IRDIS in
H
band, delivering one of the deepest sensitivity surveys thus far for young, nearby stars. A total of sixteen substellar companions were imaged in this first part of SHINE: seven brown dwarf companions and ten planetary-mass companions.These include two new discoveries, HIP 65426 b and HIP 64892 B, but not the planets around PDS70 that had not been originally selected for the SHINE core sample. A total of 1483 candidates were detected, mainly in the large field of view that characterizes IRDIS. The color-magnitude diagrams, low-resolution spectrum (when available with IFS), and follow-up observations enabled us to identify the nature (background contaminant or comoving companion) of about 86% of our subsample. The remaining cases are often connected to crowded-field follow-up observations that were missing. Finally, even though SHINE was not initially designed for disk searches, we imaged twelve circumstellar disks, including three new detections around the HIP 73145, HIP 86598, and HD 106906 systems.
Conclusions.
Nowadays, direct imaging provides a unique opportunity to probe the outer part of exoplanetary systems beyond 10 au to explore planetary architectures, as highlighted by the discoveries of: one new exoplanet, one new brown dwarf companion, and three new debris disks during this early phase of SHINE. It also offers the opportunity to explore and revisit the physical and orbital properties of these young, giant planets and brown dwarf companions (relative position, photometry, and low-resolution spectrum in near-infrared, predicted masses, and contrast in order to search for additional companions). Finally, these results highlight the importance of finalizing the SHINE systematic observation of about 500 young, nearby stars for a full exploration of their outer part to explore the demographics of young giant planets beyond 10 au and to identify the most interesting systems for the next generation of high-contrast imagers on very large and extremely large telescopes.
In this paper, a new WINNER+-based 3-D non-stationary geometry-based stochastic model (GBSM) for multiple-input multiple-output channels is proposed, as well as extended evolving algorithms of ...time-variant channel parameters. Meanwhile, important statistical properties of the channel model, i.e., time-variant autocorrelation function, time-variant cross-correlation function, and time-variant Doppler power spectrum density are derived and analyzed. Moreover, we propose an efficient hardware implementation method, namely, sum-of-frequency-modulation (SoFM) method, to generate non-stationary channel coefficients. By utilizing compact hardware architecture with SoFM modules, the proposed 3-D non-stationary GBSM is realized on a field-programmable gate array hardware platform. Simulations and hardware measurement results demonstrate that our proposed channel simulator and emulator can get more accurate and realistic Doppler frequency than those of the existing models. In addition, hardware measurements of statistical properties are also well consistent with the corresponding theoretical ones, which verify the correctness of both the hardware emulation scheme and theoretical derivations.
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