Off-axis Angle Research Articles

Micromechanical characterizing the effective elastic properties of general randomly distributed CNT–reinforced polymer nanocomposites

This work deals with a comprehensive study on the general off-axis mechanical properties of polymer nanocomposites reinforced by carbon nanotubes (CNTs) using a three-dimensional micromechanical model. The representative volume element (RVE) of the model consists of three phases including CNT, polymer matrix and interphase formed due to the non-bonded interaction between a CNT and the polymer. The CNTs are assumed to be transverse isotropic. Both random under several statistical distribution and regular arrangements of the CNTs within the matrix are considered in the analysis. The results are shown to be consistent with the results of other theoretical methods and experiment. Effects of various parameters, including the CNT aspect ratio, orientation, distribution, cross sectional shape and volume fraction, the interphase characteristics and the matrix material properties are examined on the effective elastic properties of CNT–reinforced polymer nanocomposites. The results reveal that the mechanical properties of the nanocomposite are extremely dependent on the CNTs off-axis angle. The interphase effect is more significant for the elastic modulus of 70°off-axis coupon. It is found that CNT volume fraction has the maximum effect for the longitudinal elastic modulus. For 90°coupons, elastic modulus of the nanocomposite is significantly affected by the matrix properties. The results obviously indicate that the elastic modulus, especially in the longitudinal direction increases up to a threshold value and then saturates as the CNT aspect ratio increases. Also, it is found that the CNT arrangement does not affect the longitudinal elastic modulus of CNT–polymer nanocomposites, whereas the transverse elastic modulus is significantly affected by the CNT arrangement.

Micromechanical analysis of the elastic response of glass-epoxy hybrid composites containing silica nanoparticles

ABSTRACTThe effects of adding silica nanoparticles on the elastic properties of glass-epoxy hybrid composites are investigated using a micromechanical method. Influences of silica nanoparticle volume fraction and diameter, the interphase elastic modulus and thickness, the glass fiber volume fraction and aspect ratio as well as off-axis angle on the elastic properties of unidirectional glass fiber-reinforced epoxy hybrid composites containing silica nanoparticles are studied. The results reveal that the addition of silica nanoparticles can improve the elastic modulus in the transverse direction, while the axial elastic modulus is not affected by silica nanoparticles.

Microchannel Plate Detection Efficiency to Monoenergetic Photons Between 0.66 and 20 MeV

Southwest Research Institute investigated the response of a microchannel plate (MCP) detector to isotropic radioactive source emissions at photon energies of 0.662 and approximately 1.25 million electronvolts (MeV) and to a beam of monoenergetic photons (gamma rays) at 2.5, 5, 7, 10, 13, and 20 MeV in the Free Electron Laser Laboratory at Duke University. These measurements were performed to quantify anticipated noise levels of a mass spectrometer instrument for space exploration in a harsh radiation environment and included various incident angles of radiation on the MCP. Measured photon detection efficiencies at 0° incident angle to 0.662 and 1.25 MeV were approximately 0.3%–0.4% and are bracketed by previously published data. In the 2.5- to 20-MeV energy range for which comparable published data are not available, measured detection efficiencies were on the order of 0.02%–0.2%. Radiation transport simulations were compared to the experimental results and showed decent agreement. The measured detection efficiency increased as the incident photon angle was changed from being normal to the MCP surface (0°) to being aligned with the MCP edge (90°). At greater off-axis angles, photons were incident on the side of the detector cartridge and generated secondary radiation from photon interactions in the cartridge materials that subsequently registered MCP counts.

Optical Design, Tolerance Analysis, and Baffling of Very High-Resolution Satellite Telescopes

The telescope design of a very high-resolution earth observation satellite is a challenging task due to several constraints, including the size, mass, performance, tolerance and environmental aspects. However, the demand for very high-resolution satellite imagery has increased day by day due to the numerous commercial and military applications. In this paper, an optical configuration for a ground sampling distance (GSD) of 25 cm is investigated according to a definite mission statement. The configuration represents on-axis Korsch scheme with the advantage of small conic mirror constants without higher-order parameters. In addition, a tolerance analysis utilizing a Monte Carlo algorithm is performed. The suggested baffling arrangement based on a series of point sources with different off-axis angles isderived. The size of the telescope is applicable to be launched into space by the current launch vehicles.

The fatigue life study of polyphenylene sulfide composites filled with continuous glass fibers

In this study, an effective microscopic model is proposed to investigate the fatigue life of composites containing continuous glass fibers, which is surrounded by polyphenylene sulfide (PPS) matrix materials. The representative volume element is discretized by parametric elements. Moreover, the microscopic model is established by employing the relation between average surface displacements and average surface tractions. Based on the experimental data, the required fatigue failure parameters of the PPS are determined. Two different fiber arrangements are considered for comparisons. Numerical analyses indicated that the square edge packing provides a more accuracy. In addition, microscopic structural parameters (fiber volume fraction, fiber off-axis angle) effect on the fatigue life of Glass/PPS composites is further discussed. It is revealed that fiber strength degradation effects on the fatigue life of continuous fiber-reinforced composites can be ignored.

Jets in Hydrogen-poor Superluminous Supernovae: Constraints from a Comprehensive Analysis of Radio Observations

Abstract The energy source powering the extreme optical luminosity of hydrogen-stripped superluminous supernovae (SLSNe-I) is not known, but recent studies have highlighted the case for a central engine. Radio and/or X-ray observations are best placed to track the fastest ejecta and probe the presence of outflows from a central engine. We compile all the published radio observations of SLSNe-I to date and present three new observations of two new SLSNe-I. None were detected. Through modeling the radio emission, we constrain the subparsec environments and possible outflows in SLSNe-I. In this sample, we rule out on-axis collimated relativistic jets of the kind detected in gamma-ray bursts (GRBs). We constrain off-axis jets with opening angles of 5° (30°) to energies of E k < 4 × 10 50 erg ( E k < 10 50 erg ) in environments shaped by progenitors with mass-loss rates of M ˙ < 10 − 4 M ⊙ yr − 1 ( M ˙ < 10 − 5 M ⊙ yr − 1 ) for all off-axis angles, assuming fiducial values ϵ e = 0.1 and ϵ B = 0.01 . The deepest limits rule out emission of the kind seen in faint uncollimated GRBs (with the exception of GRB 060218) and from relativistic SNe. Finally, for the closest SLSN-I, SN 2017egm, we constrain the energy of an uncollimated nonrelativistic outflow like those observed in normal SNe to E k ≲ 10 48 erg.

Robust digital holography design with monitoring setup and reference tilt error elimination.

A robust digital holography recording design is presented to complete the work of switching between in-line and off-axis recording methods. We precisely supervise the off-axis angle in off-axis holography, so that the original reconstructed image can be separated by a minimum off-axis angle. In the design, we can also monitor and remove the negative effects of the reference tilt error in phase-shifting digital holography. Compared with the conventional digital holographic recording configuration, a supervising unit is introduced to control and to monitor the angle between the reference beam and object beam. By the Fourier analysis on the interferograms recorded by the supervising unit and using the corresponding equations, the off-axis angle, which is crucial to reset the object image in holographic reconstruction, can be calculated accurately and then chosen for the best recording angle. For in-line holography, the error affecting the slight tilt of the reference beam on the retrieved object wavefront can be eliminated completely because the tilt angle is detected by another independent device. Furthermore, by using this advanced design, the experimental arrangement can be transformed flexibly from the in-line recording state to the off-axis state or from the latter one to the former without rebuilding the experimental setup. The availability and effectiveness of this design are verified by a series of experiments.

Inorbit performance of the Hard X-ray Telescope (HXT) on board the Hitomi (ASTRO-H) satellite

Hitomi (ASTRO-H) carries two Hard X-ray Telescopes (HXTs) that can focus X-rays up to 80 keV. Combined with the Hard X-ray Imagers (HXIs) that detect the focused X-rays, imaging spectroscopy in the high-energy band from 5 keV to 80 keV is made possible. We studied characteristics of HXTs after the launch such as the encircled energy function (EEF) and the effective area using the data of a Crab observation. The half power diameters (HPDs) in the 5--80 keV band evaluated from the EEFs are 1.59 arcmin for HXT-1 and 1.65 arcmin for HXT-2. Those are consistent with the HPDs measured with ground experiments when uncertainties are taken into account. We can conclude that there is no significant change in the characteristics of the HXTs before and after the launch. The off-axis angle of the aim point from the optical axis is evaluated to be less than 0.5 arcmin for both HXT-1 and HXT-2. The best-fit parameters for the Crab spectrum obtained with the HXT-HXI system are consistent with the canonical values.

Expected neutrino fluence from short Gamma-Ray Burst 170817A and off-axis angle constraints

We compute the expected neutrino fluence from SGRB 170817A, associated with the gravitational wave event GW 170817, directly based on Fermi observations in two scenarios: structured jet and off-axis (observed) top-hat jet. While the expected neutrino fluence for the structured jet case is very small, large off-axis angles imply high radiation densities in the jet, which can enhance the neutrino production efficiency. In the most optimistic allowed scenario, the neutrino fluence can reach only $10^{-4}$ of the sensitivity of the neutrino telescopes. We furthermore demonstrate that the fact that gamma-rays can escape limits the baryonic loading (energy in protons versus photons) and the off-axis angle for the internal shock scenario. In particular, for a baryonic loading of ten, the off-axis angle is more strongly constrained by the baryonic loading than by the time delay between the gravitational wave event and the onset of the gamma-ray emission.

Scattering phase function depolarization parameter model and its application to water droplets sizing using off-axis lidar measurements at multiple angles.

The backscattering lidar depolarization parameter D of water droplets contains information on their size that can be directly modeled as a function of the forward-scattering diffraction peak. Using a polarimetric Monte Carlo simulator, water clouds having different extinctions and droplet size distributions are analyzed to estimate their depolarization parameter at various backscattering off-axis angles. It is shown that the depolarization parameter of the polarimetric phase function can be found using off-axis lidar measurements at multiple angles, and that it could be used to estimate the water-cloud droplet size.

Foveal vision power errors induced by spectacle lenses designed to correct peripheral refractive errors.

Radial Refractive Gradient (RRG) spectacles are lenses specifically designed to minimize peripheral hyperopic defocus typically found in conventional spectacles. Our goals were: (1) to demonstrate a method to design such lenses; and (2) to quantify the exact foveal vision power errors induced by them. The design procedure was based on a point-by-point sequential surface construction algorithm that designs a front aspheric surface (back surface is spherical) to achieve a given overall tangential focal length of the lens. A peripheral refraction model was built based on average peripheral refractive errors from a set of eyes. We designed four negative lenses with optical powers: -2.5, -5.0, -7.5 and -10.0D, so that the tangential focal length of the lens matches the retinal conjugate surface. The lenses induce very small sagittal power errors in a wide range of off-axis field angles (30°), solving the problem of peripheral hyperopic defocus. However, such designs introduce non-negligible mean power errors (above 0.25D from 7°, 6.8°, 7.1° and 7.8° for the -2.5, -5.0, -7.5 and -10.0D lenses, respectively) for foveal vision in a rotating eye. Our results show the unavoidable errors introduced by RRG spectacles when used for dynamic foveal vision. The described method offers valuable information towards determining the best trade-off between controlling power errors for peripheral and foveal vision.

Intra-cycle depolarization of ultraintense laser pulses focused by off-axis parabolic mirrors

A study of the structure of the electric and magnetic fields of ultraintense laser pulses focused by an off-axis parabolic mirror is reported. At first, a theoretical model is laid out, whose final equations integration allows the space and time structure of the fields to be retrieved. The model is then employed to investigate the field patterns at different times within the optical cycle, for off-axis parabola parameters normally employed in the context of ultraintense laser–plasma interaction experiments. The results show that nontrivial, complex electromagnetic field patterns are observed at the time at which the electric and magnetic fields are supposed to vanish. The importance of this effect is then studied for different laser polarizations, $f$ numbers and off-axis angles.

Not All Polyaxial Locking Screw Technologies Are Created Equal: A Systematic Review of the Literature.

Locking plate fixation strength relies on axial alignment of the screw axis and plate hole, with small deviations in alignment substantially decreasing the load to failure. In an effort to overcome this technical deficiency, polyaxial locking plates were designed to provide increased flexibility of screw positioning with the intent of not sacrificing fixation strength. The purpose of this article is to review the variety of polyaxial locking mechanisms currently available, to compare the biomechanical performance of these designs, and to highlight their differences, which may have clinical implications. A systematic review using the search terms "polyaxial locking," "variable angle locking," "polyaxial screws," and "variable angle screws" was conducted to identify all English-language articles assessing variable-angle locking screw technology. All articles directly comparing the biomechanical performance of polyaxial locking technologies were included. Polyaxial locking is achieved by 5 described mechanisms: point-loading thread-in, cut-in, locking cap, expansion bushing, and screw-head expansion. With increasing insertion angulation, point-loading thread-in and cut-in designs demonstrate reduced failure strength. However, locking-cap fixation maintains consistent failure strength with increasing off-axis insertion angles. Reports comparing polyaxial locking technologies are limited. The current biomechanical literature raises concerns that these mechanisms have various strengths and performance characteristics. Based on the results of the few studies that exist, it appears that locking-cap fixation provides superior biomechanical strength when compared with point-loading and cut-in designs. Additional studies are needed to assess variable-angle locking mechanisms more completely.

Experimental and theoretical investigation of a unidirectional glass/epoxy composites under tensile and impact loading

Impact resistance (energy absorption) is the needful information for any engineering material which has been used for vehicles to reduce the fatal accidents. The present study focuses to investigate the behavior of unidirectional glass fiber reinforced plastic (GP) composites of different orientations [0°, 45°, [45°/-45°/45°]s, [±45°/0°/90°]s and 90°] under tensile and impact loading. The new laminate orientation ([45°/-45°/45°]s) is introduced in contrast to [±45°]s laminate for improving the energy absorption of the composites. The notched impact tests have conducted to obtain the energy absorption of a material using the Izod impact machine. The classical laminate theory [CLT] is employed for determining the theoretical tensile properties. The properties obtained from the theoretical model and experimental studies match well. The significant results obtained from this study indicate that the tensile strength and modulus are decreasing with increasing off-axis loading angle. The attempt is interpreted to elucidate the comparison of experimental studies and theoretical modelling in alliance with the fractography analysis in tensile and impact damaged specimens using the scanning electron microscopy is discussed.

Improved Constraints on H0 from a Combined Analysis of Gravitational-wave and Electromagnetic Emission from GW170817

Abstract The luminosity distance measurement of GW170817 derived from gravitational-wave analysis in Abbott et al. (2017a, hereafter A17:H0) is highly correlated with the measured inclination of the NS–NS system. To improve the precision of the distance measurement, we attempt to constrain the inclination by modeling the broadband X-ray-to-radio emission from GW170817, which is dominated by the interaction of the jet with the environment. We update our previous analysis and we consider the radio and X-ray data obtained at t < 40 days since merger. We find that the afterglow emission from GW170817 is consistent with an off-axis relativistic jet with energy E k ∼ 1048 −3 × 1050 erg propagating into an environment with density n ∼ 10−2–10−4 cm−3, with preference for wider jets (opening angle θ j = 15°). For these jets, our modeling indicates an off-axis angle θ obs ∼ 25°–50°. We combine our constraints on θ obs with the joint distance–inclination constraint from LIGO. Using the same ∼170 km s−1 peculiar velocity uncertainty assumed in A17:H0 but with an inclination constraint from the afterglow data, we get a value of km s−1 Mpc−1, which is higher than the value of km s−1 Mpc−1 found in A17:H0. Further, using a more realistic peculiar velocity uncertainty of 250 km s−1 derived from previous work, we find km s−1 Mpc−1 for H 0 from this system. This is in modestly better agreement with the local distance ladder than the Planck cosmic microwave background, though such a significant discrimination will require ∼50 such events. Measurements at t > 100 days of the X-ray and radio emission will lead to tighter constraints.

Micromechanics-based characterization of mechanical properties of fuzzy fiber-reinforced composites containing carbon nanotubes

General off-axis mechanical behavior of fuzzy fiber-reinforced composites (FFRCs) is investigated using a 3-dimensional unit cell micromechanics model. In the FFRCs studied herein, uniformly aligned carbon nanotubes (CNTs) are radially grown on the circumferential surfaces of carbon fibers. The effects of orientation and volume fraction of carbon fiber, volume fraction of CNT, stiffness and thickness of the interphase region created due to non-boned interaction between the CNT and polymer matrix on the elastic response of the FFRCs are studied. The results reveal that the mechanical properties of the FFRCs are strongly dependent on the off-axis angle of carbon fiber. With the increase of off-axis angle from 0° up to 90°, the elastic modulus of FFRC sharply decreases up to 45° and then its value increases, whereas without considering CNTs on the surface of carbon fiber, the elastic modulus continuously decreases. It is shown that the growth of CNTs on the surface of carbon fiber can lead to the highest enhancement for the elastic modulus of 90° on-axis coupon. Poisson's ratio of the FFRC rises with the increase of off-axis angle from 0° up to about 35° and then its value decreases. Also, the increase of CNT volume fraction yields a significant increase for the elastic modulus of 90° on-axis coupon, while rising carbon fiber volume fraction can substantially enhance the elastic modulus of 0° coupon. According to the obtained results, increasing both stiffness and thickness of the interphase can improve the elastic modulus of FFRC over the range of 0–90°, especially for 90° on-axis coupon. The results predicted by the present model are much closer to the experiment than those predicted by the numerical simulations available in the literature.

Heavy neutrino mixing in the T2HK, the T2HKK and an extension of the T2HK with a detector at Oki Islands

We study the discovery potential for the mixing of heavy isospin-singlet neutrinos in extensions of the Tokai-to-Kamioka (T2K) experiment, the Tokai-to-Hyper-Kamiokande (T2HK), the Tokai-to-Hyper-Kamiokande-to-Korea (T2HKK) with a Korea detector with simeq 1000 km baseline length and 1^circ off-axis angle, and a plan of adding a small detector at Oki Islands to the T2HK. We further pursue the possibility of measuring the neutrino mass hierarchy and the standard CP-violating phase delta _{CP} in the presence of heavy neutrino mixing by fitting data with the standard oscillation parameters only. We show that the sensitivity to heavy neutrino mixing is highly dependent on delta _{CP} and new CP-violating phases in the heavy neutrino mixing matrix, and deteriorates considerably when these phases conspire to suppress interference between the standard oscillation amplitude and an amplitude arising from heavy neutrino mixing, at the first oscillation peak. Although this suppression is avoided by the use of a beam with smaller off-axis angle, the T2HKK and the T2HK+small Oki detector do not show improvement over the T2HK. As for the mass hierarchy measurement, the wrong mass hierarchy is possibly favored in the T2HK because heavy neutrino mixing can mimic matter effects. In contrast, the T2HKK and the T2HK+small Oki detector are capable of correctly measuring the mass hierarchy despite heavy neutrino mixing, as measurements with different baselines resolve degeneracy between heavy neutrino mixing and matter effects. Notably, adding a small detector at Oki to the T2HK drastically ameliorates the sensitivity, which is the central appeal of this paper. As for the delta _{CP} measurement, there can be a sizable discrepancy between the true delta _{CP} and the value obtained by fitting data with the standard oscillation parameters only, which can be comparable to 1sigma resolution of the delta _{CP} measurement. Hence, if a hint of heavy neutrino mixing is discovered, it is necessary to incorporate the effects of heavy neutrino mixing to measure delta _{CP} correctly.

Search for High-energy Neutrinos from Binary Neutron Star Merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory

The Advanced LIGO and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst (GRB) that followed the merger of this binary was also recorded by the Fermi Gamma-ray Burst Monitor (Fermi-GBM), and the Anticoincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the GeV--EeV energy range using the ANTARES, IceCube, and Pierre Auger Observatories. No neutrinos directionally coincident with the source were detected within $\pm500$ s around the merger time. Additionally, no MeV neutrino burst signal was detected coincident with the merger. We further carried out an extended search in the direction of the source for high-energy neutrinos within the 14-day period following the merger, but found no evidence of emission. We used these results to probe dissipation mechanisms in relativistic outflows driven by the binary neutron star merger. The non-detection is consistent with model predictions of short GRBs observed at a large off-axis angle.

A parametric study of skin laminates used in the composite layup of large-scale wind turbine blades

To reach an optimal design solution for the composite layup of large-scale wind turbine blades, subjected to various design load conditions, while, fulfilling numerous design requirements, is a challenging task to accomplish. Since, a large-scale blade is a slender beam structure, therefore, its thin composite layup can be assumed to be under plane stress condition. Consequently, a parametric study of the skin laminates used in the blade composite layup, is conducted to explore and identify the possible design improvements. The results show that the use of off-axis fiber angles of the skin laminate lower than the conventional 45° are more favorable to achieve higher laminate stiffness, strength, bucking stability, fatigue resistance, and bend-twist coupling value, thereby, demonstrating the potential improvements to the existing composite layup design of large-scale wind turbine blade.

Design of optical wavelength demultiplexer based on off-axis meta-lens.

We propose an off-axis meta-lens-based optical wavelength demultiplexer. The performance of the device initially proposed with four output channels (1527-1596nm, channel spacing 23nm) composed of an optical fiber array is analyzed by both scalar diffraction theory and ray tracing method. The results show that the fiber energy coupling efficiency of the demultiplexer could be larger than 89% and the channel bandwidth is about 9nm. Influences of the two key parameters, focal length f and off-axis angle α, are also investigated. We find that the minimum spectral linewidth of the channel is inversely proportional to the sine of α and nearly independent of f for a meta-lens with large F-number (F>5), while the effective spectral range is negatively (positively) dependent on α (f). These results are significant in guiding us to build small and compact demultiplexing devices for optical telecommunication.