Small Inclination Angle Research Articles

RPICARD: A CASA-based calibration pipeline for VLBI data

Context. The Common Astronomy Software Application (CASA) software suite, which is a state-of-the-art package for radio astronomy, can now reduce very long baseline interferometry (VLBI) data with the recent addition of a fringe fitter. Aims. Here, we present the Radboud PIpeline for the Calibration of high Angular Resolution Data (rPICARD), which is an open-source VLBI calibration and imaging pipeline built on top of the CASA framework. The pipeline is capable of reducing data from different VLBI arrays. It can be run non-interactively after only a few non-default input parameters are set and delivers high-quality calibrated data. CPU scalability based on a message-passing interface (MPI) implementation ensures that large bandwidth data from future arrays can be processed within reasonable computing times. Methods. Phase calibration is done with a Schwab–Cotton fringe fit algorithm. For the calibration of residual atmospheric effects, optimal solution intervals are determined based on the signal-to-noise ratio (S/N) of the data for each scan. Different solution intervals can be set for different antennas in the same scan to increase the number of detections in the low S/N regime. These novel techniques allow rPICARD to calibrate data from different arrays, including high-frequency and low-sensitivity arrays. The amplitude calibration is based on standard telescope metadata, and a robust algorithm can solve for atmospheric opacity attenuation in the high-frequency regime. Standard CASA tasks are used for CLEAN imaging and self-calibration. Results. In this work we demonstrate the capabilities of rPICARD by calibrating and imaging 7 mm Very Long Baseline Array (VLBA) data of the central radio source in the M 87 galaxy. The reconstructed jet image reveals a complex collimation profile and edge-brightened structure, in accordance with previous results. A potential counter-jet is detected that has 10% of the brightness of the approaching jet. This constrains jet speeds close to the radio core to about half the speed of light for small inclination angles.

Rotational Evolution of the Slowest Radio Pulsar, PSR J0250+5854

Abstract We apply theoretical spin-down models of magnetospheric evolution and magnetic field decay to simulate the possible evolution of PSR J0250+5854, which is the slowest-spinning radio pulsar detected to date. Considering the alignment of inclination angle in a 3D magnetosphere, it is possible that PSR J0250+5854 has a high magnetic field comparable with magnetars or/and high magnetic field pulsars, if a small inclination angle is considered. Our calculations show that similar long-period pulsars tend to have a relatively low period derivative in this case. In another case of magnetic field decay, calculations also show a possible connection between PSR J0250+5854 and high dipole-magnetic field magnetars. The evolutionary path indicates a relatively high spin-down rate for similar long-period pulsars.

Influence of drop weight geometry and interlayer on impact behavior of RC beams

A number of drop weight tests on reinforced concrete (RC) beams have been reported in literature. These tests conducted by different researchers used drop weight of different geometries. Some researchers also placed an interlayer between the drop weight and RC beam in the tests, while others directly dropped the weight on the beam. These different testing configurations surely affect the testing results. However, only very limited studies have been conducted to investigate their effects on the impact behavior of RC beams. In this study, the influence of drop weight geometry and interlayer on the impact behavior of RC beams is numerically investigated by using explicit finite element code LS-DYNA. The numerical models of RC beams subjected to drop weigh impact are verified by available testing data. With the calibrated model, the responses of RC beams impacted by five commonly used drop weights are analyzed and discussed. The effect of steel plate or rubber pad interlayer between drop weight and RC beam is also investigated. It is found that both the drop weight geometry and interlayer property significantly affect the impact loading profile and the failure mode of RC beams. Furthermore, although most drop-weight tests assume vertical impact, small inclination angles of drop weight impacting on beams might occur. The influence of this small testing error on testing results is also investigated.

High Efficiency Precision Grinding of Micro-structured SiC Surface Using Laser Micro-structured Coarse-Grain Diamond Grinding Wheel

Accompanying with the extensive applications of micro-structured surfaces on hard and brittle material in MEMS and NEMS sensors, optical elements, electronic devices and medical products, efficiently fabricating of these surface has gradually become the focus of manufacturing community. Basing on precision grinding with conditioned and laser micro-structured coarse-grained diamond grinding wheel, a novel high efficiency technique for micro-structured surfaces on hard and brittle material, such as silicon carbide, was developed in this paper. Firstly, the maximum undeformed chip thickness for conditioned coarse-grained wheel and the ductile grinding of silicon carbide was theoretically and experimentally studied. Silicon carbide surface formed mainly in ductile regime was successfully achieved. And then, the strategy for micro-structuring the conditioned wheel with designed micro-structure geometry, sharp edge and small inclination angle side-wall was investigated. Finally, the linear and square micro-structured surfaces with high form accuracy and ultra-precision surface roughness were successfully and efficiently fabricated on silicon carbide by the technique developed in this paper.

On the Orientation of Convective Rolls in an Inclined Rectangular Channel

An analysis of the linear stability of convective flow in a channel of rectangular cross-section inclined to the horizon is presented. The behavior of three-dimensional monotonic disturbances is considered for different values of the channel width and fluid properties. The main flow is obtained in an analytical form. Two angles of inclination, at which the convective roll changes, are determined. A strong dependence of the smaller inclination angle on the channel width and its weak dependence on the medium characteristics and a weak dependence of the greater inclination angle on the channel width are established.

Influence of Flaw Inclination Angle on Unloading Responses of Brittle Rock in Deep Underground

Excavation unloading is a primary stress condition for engineering rock mass in deep underground. Based on the unloading stress condition during the excavation operation, this paper employed a distinct element method (DEM) to simulate the unloading responses of intact and preflawed rock specimens. The simulation results revealed that the unloading failure strength, unloading damage thresholds, and cracking characteristics were largely dependent on the inclination angle α of the preflaws. With the increase in the flaw inclination angle, the unloading failure strength of a preflawed specimen exhibited a sigmoidal curve increasing trend, and it decreased by 5.5%-20% compared to the unloading failure strength of an intact specimen. Based on the crack accumulation in specimens, three damage thresholds were identified under unloading condition and two damage thresholds σci and σdi were found to be increased with the increase in the flaw inclination angle. Furthermore, when the flaw inclination angle was smaller, cracks were initiated around the preflaws, and there were obvious axial splitting cracks in the failure modes of preflawed specimens, while axial splitting cracks were few in the preflawed specimen with a larger flaw inclination angle and none in the intact specimen. These unloading responses indicate that inducing preflaws can reliably reduce the unloading failure strength and promote the cracking process of hard rock during an excavation unloading process. Moreover, inducing preflaws with a smaller inclination angle (e.g., vertical to the unloading direction) will be more helpful for the unloading failure and rock cracking during an excavation unloading process.

Spino-pelvic- lower extremity balance during walking in elderly patients with spinal kyphosis

Back groundPatients with spinal kyphosis were radiographically evaluated while standing. However, the spino-pelvic alignment during walking is different. This study examined the spino-pelvic-lower extremity alignment during walking by a three-dimensional (3D) motion analysis. MethodsTwenty-six patients with a sagittal vertical axis of ≥4 cm (male: female, 5:21; average age, 66 years) were evaluated. Using a 3D motion capture system, the trunk and pelvic anterior inclination angles, hip and knee joint angles were measured during a 3-min walk. The correlation coefficient between the change of the trunk anterior inclination angle and each parameter at the beginning of walking was calculated, and those parameters were compared with radiographic measurements. ResultsThe patients were divided into two groups according to the change of the trunk anterior inclination angle: the large change group included 14 patients with an increase of ≥5° between the beginning and end of the 3-min walk; the small change group included 12 patients with an increase of <5°. The pelvic anterior inclination angle showed a significant difference between the two groups at the first gait cycles. The pelvic anterior inclination angle and the hip joint angle in the large change group showed a significant difference between the first and last cycles. The correlation coefficient revealed a significant association between the change in the trunk anterior inclination angle and the pelvic anterior inclination angle at the beginning of walking. There were no significant differences between the two groups in any radiographic spino-pelvic parameters. ConclusionsThere were two types of patients with spinal kyphosis: patients with a small pelvic anterior inclination angle at the beginning of walking showed slight progression in their trunk anterior inclination, whereas those with a large pelvic angle showed a large degree of progression in their pelvic and trunk inclination during walking.

Enhancement of a heat sink performance using a partial shield and/or a guide plate

The potential of using a full shield or partial shield with a guide plate to control the bypass cooling air flowing above a heat sink is numerically modeled using two different scenarios of inlet conditions – fixed mass flow rate and specified fan curve. Excellent agreement is observed when the simulation results are compared with available experimental data in the literature. Under the first inlet condition, the Nusselt numbers associated with the full shield installation are significantly higher than those without a shield, but with a significant pressure drop penalty. Friction factor increases with partial shield height till it reaches a maximum value with the full-shield configuration. Using an inclined guide plate with a partial shield alters the flow direction, forcing the air to impinge on the heat sink. This adds an extra cooling effect but without causing a considerable increase in the friction factor. In the case of fixed inlet mass flow rate, most of the partial shield and guide plate cases show the lowest pressure drop when the ratio of the partial shield height to the total bypass height Hs/HBP is between 0.35 and 0.5. The case with an inclination angle of θP = 15° has the highest thermal performance and the highest pressure drop. Correlations for the average Nusselt number and friction factor are developed to include the effect of Reynolds number, shield height, bypass height and guide plate inclination angle. For the second inlet condition, the test cases are repeated using a selected fan characteristic curve as an alternate to the fixed mass flow rate condition. The specified fan curve case shows that a short partial shield with a slightly inclined guide plate has a better thermal performance than the full shield case. Furthermore, using a guide plate only with a small inclination angle has a superior thermal performance. Changing the position of the guide plate is investigated as well and the optimal location is obtained.

Mathematical modeling of particle aggregation and sedimentation in the inclined tubes

Sedimentation of the aggregating particles in the gravity field is widely used as an easy and cheap test of the suspension stability of different technical suspensions, blood and nanofluids. It was established the tube inclination makes the test much faster that is known as the Boycott effect. It is especially important for the very slow aggregating and sedimenting blood samples in medical diagnostics or checking the ageing of the nanofluids. The dependence of the sedimentation rate on the angle of inclination is complex and poorly understood yet. In this paper the two phase model of the aggregating particles is generalized to the inclined tubes. The problem is formulated in the two-dimensional case that corresponds to the narrow rectangle vessels or gaps of the viscosimeters of the cone-cone type. In the suggestion of small angles of inclination the equations are averaged over the transverse coordinate and the obtained hyperbolic system of equations for is solved by the method of characteristics. During the sedimentation the upper region (I) of the fluid free of particles, the bottom region (III) of the compactly located aggregates without fluid, and the intermediate region of the sedimenting aggregates (II) appear. The interface between I and II can be registered by any optic sensor and its trajectory is the sedimentation curve. Numerical computations revealed the increase in the initial concentration of the particles, their aggregation rate, external uniform force and inclination angle accelerate the sedimentation while any increase in the fluid viscosity decelerates it that is physically relevant. Anyway, the behaviors of the acceleration are different. For the elevated force the interfaces I-II and II-III shifts uniformly, while for the elevated concentration or aggregation rate the interface I-II or II-III moves faster. Small increase of the inclination angle accelerates the sedimentation while at some critical angles is starts to decelerate due to higher shear drag in the very viscous mass of the compactly located aggregates. Based on the results, a novel method of estimation of the suspension stability is proposed.

Controllable growth of InAs quantum dots on patterned GaAs (001) substrate

InAs/GaAs quantum dot (QD) is one of the promising material systems for the quantum information processing due to their atomic-like optical and electrical properties. There are many previous researches reporting the InAs QDs which can be implemented as solid-state single-photon sources for quantum information and quantum computing. However, the site-controlled growth of QDs is the prerequisite for addressability and integration. There are very few researches focusing on the systematic study of preferential nucleation of InAs QDs on a patterned GaAs (001) substrate. In this work, we study the preferential nucleation sites of InAs QDs on a patterned GaAs (001) substrate with different trench sidewall inclinations. With small inclination angle of the trench sidewalls, the InAs QDs nucleate preferentially inside the trenches, while with large inclination angle, the edges of the trenches appear to be the preferential nucleation sites. By utilizing the established method, a pair of InAs dots can be uniformly achieved in the patterned pits through tuning the inclination angle of the pits. The site-controlled single InAs QD and InAs QD molecules on the patterned substrates could have potential applications in quantum information processing and quantum computing.

Experimental study on the thermal performance of a novel ultra-thin aluminum flat heat pipe

This study proposes a novel ultra-thin aluminum flat heat pipe with thickness of 1.5 mm for the first time in order to satisfy the ever increasing requirements for cost-effective, physically compact and highly efficient thermal management solutions. The extruded aluminum tube contains multiple separate micro cavities that work as independent micro heat pipes and a two-level compressing process is applied to flatten the tube to the ideal thickness. Sintered aluminum fibers and aluminum fiber meshes with surface treatment are inserted into each cavity of the ultra-thin heat pipe as the extra wicks for comparison. The thermal response characteristics of the fabricated aluminum heat pipes, including the temperature uniformity, thermal resistance, and effects of wick structure and inclination angles, are fully investigated. Under large inclination angle (90°), the smooth heat pipe without any extra wick performs lower temperature difference, lower thermal resistance, and higher heat transport capacity compared to that with aluminum fiber wick whereas the heat pipes with wicks present superiority under smaller inclination angles (60° and 30°) due to the liquid backflow enhancement. Besides, comparative study also shows that wick structure optimization holds the potential to improve the thermal performance of this ultra-thin two-phase device.

Misaligned snowplough effect and the electromagnetic counterpart to black hole binary mergers

We estimate the accretion rates produced when a circumprimary gas disc is pushed into the primary supermassive black hole (SMBH) by the tidal force of the decaying secondary during a SMBH merger. Using the 3D Smoothed Particle Hydrodynamics (SPH) code {\sc phantom}, we extend previous investigations of co-planar discs to the case where the disc and binary orbital planes are misaligned. We consider a geometrically thin disc with inclination angles varying from 1 to 180 degrees and a binary with mass ratio $q$=$10^{-3}$. We find that discs with small inclination angles (< 10 degrees) produce an increase in luminosity exceeding the Eddington rate. By contrast, discs with inclinations between 20 and 30 degrees show a less pronounced rise in the accretion rate, whilst discs inclined by 180 degrees show no peak in the mass accretion rate. While previous analytic work predicted that the effective tidal torque drops with increasing inclination angle, we show that the misaligned snowplough effect remains important even for angles larger than the disc aspect ratio. The rise in the accretion rate produced by discs inclined at small angles to the binary orbit can produce an electromagnetic counterpart to the gravitational wave signal emitted from final stages of the binary orbital decay.

Evaluation of vortex identification methods based on two- and three-dimensional swirling strengths

Analytical solutions for two-dimensional (2D) and three-dimensional (3D) swirling strengths were derived and were used to simulate the detection of 3D vortices in planar Particle Image Velocimetry (PIV). Based on Euler’s rotation theorem and the Burgers vortex model, a general equation for the 2D swirling strength of a 3D vortex having an arbitrary inclination angle with the analyzed plane was proposed. Vortices were classified into two categories: strong vortices and weak vortices. When focusing only on strong vortices, previous studies reported that the ratio of the two swirling strengths varies as a sine function; however, we found that this ratio is a function of both circulation and inclination angle, and the relative deviation between the ratio function and the sine function exhibits a monotonous decrease with increasing circulation. When vortices are classified into different categories according to the circulation, the analytical solution fits well with data points in each category. Theoretical analysis reveals that the detection of a 3D vortex in planar PIV has a dependence on two factors (circulation and inclination angle) and the detection probability of a 3D vortex with a certain inclination angle in planar PIV was simulated. For example, detection probabilities of 3D vortices with inclination angles of 10°, 30°, 50°, and 90° are 10%, 46%, 81%, and 100%, respectively. To the best of author’s knowledge and study, the universally recognized assumption that only vortices with large inclination angles can be detected in planar PIV needs to be revised. For vortices with small inclination angles, as long as their circulation is sufficiently large, they can also be detected.

Propagation of leaky surface waves on contact magnetohydrodynamic discontinuities in incompressible plasmas

We study the wave propagation on a magnetohydrodynamic contact discontinuity. Using the Laplace transform, we obtain the solution to the initial value problem describing the evolution of a perturbation of the discontinuity. We use this solution to study the leaky modes that determine the asymptotic behaviour of the solution for large time. We find the approximate expressions describing the leaky modes for a small inclination angle of the magnetic field. We also discuss the transition to the tangential discontinuity as the inclination angle tends to zero. We show that there is no continuous transition from the leaky modes on a contact discontinuity to the surface modes on a tangential discontinuity. However, such a transition exists if we take the average quantities describing the leaky modes.

Very long baseline interferometry radio structure and radio brightening of the high-energy neutrino emitting blazar TXS 0506+056

ABSTRACT We report on the radio brightening of the blazar TXS 0506+056 (at z = 0.3365), and we support its identification by the IceCube Neutrino Observatory as a source of the high-energy (HE) neutrino IC-170922A. Data from the Monitoring Of Jets in AGN with VLBA Experiments (MOJAVE)/Very Long Baseline Array (VLBA) survey indicate that its radio brightness has abruptly increased since 2016 January. When decomposing the total radio flux density curve (in the period 2008 January to 2018 July), provided by the Owens Valley Radio Observatory, into eight Gaussian flares, the peak time of the largest flare overlaps with the HE neutrino detection, while the total flux density has exhibited a threefold increase since 2016 January. We reveal the radio structure of TXS 0506+056 by analysing very long baseline interferometry (VLBI) data from the MOJAVE/VLBA survey. The jet components maintain quasi-stationary core separations. The structure of the ridge line is indicative of a jet curve in the region 0.5–2 mas (2.5–9.9 pc projected) from the VLBI core. The brightness temperature of the core and the pc-scale radio morphology support a helical jet structure at small inclination angle (&amp;lt;8${^{\circ}_{.}}$2). The jet pointing towards the Earth is a key property facilitating multimessenger observations (HE neutrinos, γ-rays and radio flares). The radio brightening preceding the detection of a HE neutrino is similar to the one reported for the blazar PKS 0723–008 and IceCube event ID5.

Crack Propagation and Coalescence of Step-Path Failure in Rocks

To provide insight into the understanding of step-path failure in rocks, gypsum specimens containing various configurations of preexisting flaws are used to investigate the crack behaviors of step-path failure in rock slopes under compression in terms of the inclination angle and number of flaws. The results show that step-path failure is usually caused by wing cracks (or tensile cracks) when the preexisting flaws are isolated or when two preexisting flaws are adjacent. Additionally, with an increase in the number of flaws, step-path failure is more likely to be caused by mixed wing-secondary crack formation (or tensile–shear crack formation), indicating that the mechanism of step-path failure is associated with the characteristics of the flaw (including the number of flaws, flaw inclination angle, flaw spacing, etc.). In the process of step-path cracking and failure, wing cracks can initiate at or near the middle of a preexisting flaw when the preexisting flaw has a small inclination angle (e.g., 0° or 15°), and secondary cracks usually propagate in three directions: (1) in the horizontal direction of the specimen; (2) coplanar or quasi-coplanar to the preexisting flaw; (3) in the direction perpendicular to that of wing crack propagation. Additionally, the closer the inclination angle is to 90°, the harder the secondary crack initiates. In addition, four types of coalescence cracks are identified from the specimens containing two preexisting flaws. The peak load of the specimen is influenced by the inclination angle; the closer the inclination angle is to 90°, the greater the peak load of the specimen. Furthermore, the equation describing the wing crack path of an isolated flaw, two types of spalling formations and the characteristics of the wing and secondary crack surfaces are determined and discussed.

Well-flow behavior of reorientation fracture considering permeability anisotropy

PurposeIn petroleum industry, hydraulic fracturing is essential to enhance oil productivity. The hydraulic fractures are usually generated in the process of hydraulic fracturing. Although some mathematical models were proposed to analyze the well-flow behavior of conventional fracture, there are few models to depict unconventional fracture like reorientation fracture. To figure out the effect of reorientation fracture on production enhancement and guide the further on-site operating, this paper aims to investigate the well-flow behavior of vertical reorientation fracture in horizontal permeability anisotropic reservoir.Design/methodology/approachBased on the governing equation considering horizontal permeability anisotropy, the mathematical models for reorientation fractures in infinite reservoir are developed by using the principle of superposition. Furthermore, a rectangular closed drainage area is also considered to investigate the well-flow behavior of reorientation fracture, and the mathematical models are developed by using Green’s and source functions.FindingsComputational results indicate that the flux distribution of infinite conductivity fracture is uniform at very early times. After a period, it will stabilize eventually. High permeability anisotropy and small inclination angle of reorientation will cause significant end point effect in the infinite conductivity fracture. The reorientation fractures with small inclination angle in high anisotropic reservoir are capable of improving 1-1.5 times more oil productivity in total.Originality/valueThis paper develops the mathematical methods to study the well-flow behavior for unconventional fracture, especially for reorientation fracture. The results validate the production enhancement effect of reorientation fracture and identify the sensitive parameters of productivity.

Experimental investigation on chemical grouting of inclined fracture to control sand and water flow

This paper presents an experimental investigation of the propagation of chemical grout in an inclined fracture model to control sand and water flow. The experimental grouting setup for an inclined fracture examines the propagation of chemical grout in water and sand flows by considering the different inclination angles of the fracture. The results show that grouting effectively reduces the discharge of the sand and water mixture. Moreover, the total volume of discharged sand and water is reduced when the fracture has a smaller inclination angle. Further analyses show that there is a critical inclination angle that differentiates two types of grout patterns: the “gel deposition grout pattern” and “erosion dispersion grout pattern”. The former is when the inclination angle of the fracture is less than the critical inclination angle, which is 12.4° in this study, and the water and sand flow can be stopped with grouting. The latter is when the inclination angle is greater than the critical inclination angle, so that grouting will not be able to stop the water and sand flow. The mechanisms of the sealing of inclined fractures are discussed from the perspective of a two-phase flow. It is found that the key to sealing fractures is the formation of a stable sand layer. The grout viscosity and the tendency of the grout to gel not only can reduce the speed of the water flow, but also increase the stability of the deposition of the sand particles, which explains for their improved settlement and the subsequent formation of a porous layer. Finally, the grouting becomes permeation grouting after the formation of the porous layer.

Propagation of Leaky MHD Waves at Discontinuities with Tilted Magnetic Field

We investigate the characteristics of magneto-acoustic surface waves propagating at a single density interface, in the presence of an inclined magnetic field. For linear wave propagation, the dispersion relation is obtained and analytical solutions are derived for small inclination angle. The inclination of the field renders the frequency of the waves complex, where the imaginary part describes wave attenuation, due to lateral energy leakage.

Neutron-star spindown and magnetic inclination-angle evolution

A rotating fluid star, endowed with a magnetic field, can undergo a form of precessional motion: a sum of rigid-body free precession and a non-rigid response. On secular timescales this motion is dissipated by bulk and shear viscous processes in the stellar interior and magnetospheric braking in the exterior, changing the inclination angle between the rotation and magnetic axes. Using our recent solutions for the non-rigid precessional dynamics, and viscous dissipation integrals derived in this paper, we make the only self-consistent calculation to date of these dissipation rates. We present the first results for the full coupled evolution of spindown and inclination angle for a model of a late-stage proto-neutron star with a strong toroidal magnetic field, allowing for both electromagnetic torques and internal dissipation when evolving the inclination angle. We explore this coupled evolution for a range of initial inclination angles, rotation rates and magnetic field strengths. For fixed initial inclination angle, our results indicate that the neutron-star population naturally evolves into two classes: near-aligned and near-orthogonal rotators -- with typical pulsars falling into the latter category. Millisecond magnetars can evolve into the near-aligned rotators which mature magnetars appear to be, but only for small initial inclination angle and internal toroidal fields stronger than roughly $5\times 10^{15}$ G. Once any model has evolved to either an aligned or orthogonal state, there appears to be no further evolution away from this state at later times.