Low Inclination Angle Research Articles

The persistent Be enigma: The case of HD 212044

We present an analysis of the Be star HD\,212044 that reveals intriguing correlations between photometric variations, circumstellar disk emission, and frequencies. Our findings, based on data from the Transiting Exoplanet Survey Satellite (TESS) mission, show an unexpectedly strong negative correlation between photometric brightness and Halpha equivalent width, challenging the established understanding of the behavior of Be star seen at low inclination angles. Notably, beating episodes precede brightening events. This study suggests that the variability of HD\,212044 may be due to additional mechanisms.

Characterization of the structural features of Ti-6Al-4V hollow-strut lattices fabricated by laser powder bed fusion

Hollow-strut metal lattices are novel cellular materials. Compared to their solid-strut counterparts, their powder bed fusion additive manufacturing (PBF-AM) features remain largely uninvestigated. This work focuses on characterizing the hollow-strut internal channel and nodal profiles, the defects and microstructures of the hollow-strut thin walls, and the inner surface conditions of the LPBF-manufactured body-centred cubic (BCC) Ti-6Al-4V hollow-strut lattices with different relative densities. BCC lattices are selected because of the low inclination angle (35.26°) of their constituent struts. These low-inclination hollow struts are designed using a recent model developed for PBF of inclined solid struts, together with considerations to prevent powder occlusion and ensure easy removal of powder particles. Detailed characterization indicates that our design considerations resulted in high-quality hollow-strut BCC Ti-6Al-4V lattices, which provide useful design insights for PBF-AM of hollow-strut metal lattices. In terms of microstructure, the Ti-6Al-4V hollow-strut thin walls (≤ 0.5 mm thick) exhibited different microstructures compared with Ti-6Al-4V solid struts, due to the heat accumulation effect in the inner channels. The implications are discussed for in-situ microstructure control.

Accretion Properties of Soft X-Ray Transient XTE J1856+053 during Its 2023 Outburst

Soft X-ray transients (SXTs) are a subclass of the low-mass X-ray binaries that occasionally show a sudden rise in their soft X-ray luminosity; otherwise, they remain in an extremely faint state. We investigate the accretion properties of the SXT XTE J1856+053 during its 2023 outburst obtained by NICER and NuSTAR data in July. We present detailed results on the timing and spectral analysis of the X-ray emission during the outburst. The power spectral density shows no quasi-periodic oscillation features. The source’s spectrum on July 19 can be well fitted with a multicolor blackbody component, a power-law component, and a reflection component with a broadened iron emission line. NICER spectra can be well fitted by considering a combination of a blackbody and a power law. The source exhibits a transition within just 5 days from a soft state to an intermediate state during the outburst decline phase. The inner accretion disk has a low inclination angle (∼18°). The spectral analysis also suggests a high-spin (a > 0.9) black hole as the central accreting object.

Finite element simulations on delamination-induced local stress shielding effects on aseptic loosening behavior by bone remodeling

Interfacial damages (wear, delamination) and bone damage (remodeling, micro-cracks) can significantly affect the local bone deterioration and loosening of the acetabular cup. However, limited research has been conducted on both delamination and bone remodeling. This study aims to analyze the loosening behavior of an acetabular cup caused by the interaction of both interfacial damages and bone remodeling under different boundary conditions. A three-dimensional model of the acetabular cup was developed, and mechanically-induced remodeling behavior was implemented for the surrounding bone while the interfacial delamination between the cup and bone was modeled using the fracture mechanics approach. The delamination in the low initial bone mineral density (BMDs) cases encompasses almost the entire cup surface, which significantly affects the local bone remodeling process. The bone density near the top edge could be reduced to 20% in the lowest BMDs case which exaggerates the local strain accumulation and causes it to approach the micro-breaking limit. The loosening risk of the 45∘ fixation was reported in the low BMDs case which is a major limitation in conventional operation procedures for elderly patients. The interactive effect of the low BDMs, inclination angle, and loading amplitude can reduce the aseptic loosening life by half. This can be attributed to the amplified embedding of the acetabular cup caused by the delamination-induced reduction of the bone density. In future works, we aim to further consider anisotropic bone remodeling, microstructure of the bone, and delamination initiation behavior of surface coating.

Phase-dependent Spectral Shape Changes in the Ultraluminous X-Ray Pulsar NGC 5907 ULX1

The discovery of coherent pulsations from several ultraluminous X-ray pulsars (ULXPs) has provided direct evidence of a supercritical accretion flow. However, the geometrical structure of such an accretion flow onto the central neutron star remains poorly understood. NGC 5907 ULX1 is one of the most luminous ULXPs, with a luminosity exceeding 1041 erg s−1. Here we present a broadband X-ray study of this ULXP using the data from simultaneous observations with XMM-Newton and NuSTAR conducted in 2014 July. The phase-resolved spectra are well reproduced by a model consisting of a multicolor disk blackbody emission with a temperature gradient of p = 0.5 (T ∝ r −p ) and a power law with an exponential cutoff. The disk component is phase-invariant and has an innermost temperature of ∼ 0.3 keV. Its normalization suggests a relatively low inclination angle of the disk, in contrast to the previous claims in other literature. The power-law component, attributed to the emission from the accretion flow inside the magnetosphere of the neutron star, indicates phase-dependent spectral shape changes; the spectrum is slightly harder in the pre-peak phase than in the post-peak phase. This implies that the magnetosphere has an asymmetric geometry around the magnetic axis and that hotter regions close to the magnetic pole become visible before the pulse peak.

Impact of a floating flexible plate on the stability of double-layered falling flow

The hydrodynamic stability behavior of a two-layer falling film is explored with a floating flexible plate on the top layer surface. The stress balance at the surface is modeled using a modified membrane equation. There is an insoluble surfactant at the liquid-liquid interface of the flow system. The linear instability of perturbation waves is captured by numerically solving the generalized Orr-Sommerfeld eigenvalue problem using the Chebyshev spectral collocation technique. Four different types of linear stability modes are identified: surface mode (SM), interface mode (IM), interface surfactant mode (ISM), and shear mode (SHM). The floating flexible plate has an inferior impact on all the existing modes in the longwave zone. However, a significant influence is noticed for the finite wave numbers. The surface and interface wave instabilities can be suppressed in the smaller wavenumber zone by imposing higher structural rigidity and uniform thickness of the flexible plate. The stabilizing nature of the surface mode becomes more powerful when the top layer viscosity is dominant. A new interfacial instability emerges when the top layer is less viscous than the lower one. At moderate Reynolds numbers, the behavior of interface mode is different in two different zones mr<1 and mr>1, where m and r denote the viscosity and density ratio, respectively. Further, the unstable shear modes induced by the top and bottom layers are detected under the low inclination angles with a strong inertia force. The occurrence of the shear modes requires the viscosity and density of the lower layer to be much higher than those of the upper layer. The influence of characteristic parameters of the flexible plate on the lower layer shear mode is not very sensitive. Finally, the competition between the different modes for dominance of stability boundaries is also discussed.

Observations of orbiting hot spots around scalarized Reissner–Nordström black holes

This paper investigates the observational signatures of hot spots orbiting scalarized Reissner–Nordström black holes, which have been reported to possess multiple photon spheres. In contrast to the single-photon sphere case, hot spots orbiting black holes with two photon spheres produce additional image tracks in time integrated images capturing a complete orbit of hot spots. Notably, these newly observed patterns manifest as a distinct second-highest peak in temporal magnitudes when observed at low inclination angles. These findings offer promising observational probes for distinguishing black holes with multiple photon spheres from their single-photon sphere counterparts.

Effects of vibration on granular chute flow under low-gravity conditions

The essence of most geological hazards and industrial processes is gravity-driven flows of dense particles. In this research, we use the discrete element method to simulate the particle chute flow, and discuss the effect of vibration acceleration on the granular flow under different gravity conditions. The results indicate that vibration has a greater impact on the particle flow state under low-gravity environments and low inclination angles. The granular temperature (T) and inertia number (I) increase with increasing vibration acceleration. Vibration enhances the flowability of particles by changing the stress state and reducing the volume fraction of the granular system. This work reveals the rheological state of vibration-triggered particle flow on an inclined surface under different gravity environments.

Study the effect of axially perforated baffle plate with multiple opposite-oriented trapezoidal flow deflectors in an air–water tubular heat exchanger

Purpose The research focused on analysing a unique type of heat exchanger that uses swirling air flow over heated tubes. This heat exchanger includes a round baffle plate with holes and opposite-oriented trapezoidal air deflectors attached at different angles. The deflectors are spaced at various distances, and the tubes are arranged in a circular pattern while maintaining a constant heat flux. Design/methodology/approach This setup is housed inside a circular duct with airflow in the longitudinal direction. The study examined the impact of different inclination angles and pitch ratios on the performance of the heat exchanger within a specific range of Reynolds numbers. Findings The findings revealed that the angle of inclination significantly affected the flow velocity, with higher angles resulting in increased velocity. The heat transfer performance was best at lower inclination angles and pitch ratios. Flow resistance decreased with increasing angle of inclination and pitch ratio. Originality/value The average thermal enhancement factor decreased with higher inclination angles, with the maximum value observed as 0.94 at a pitch ratio of 1 at an angle of 30°.

Study on dynamic characteristics of scraper conveyor under various scraper configurations

This study aims to explore the impact of scraper structure on the stable operation of scraper conveyors. A simulation test is designed to investigate the effect of the scraper's lower inclination angle on the wedge-shaped structure of the scraper. Based on the test results, modifications are made to the scraper's lower inclination angle. Using the DEM-MBD coupling model of the scraper conveyor, simulation analyses are conducted to evaluate the influence of the scraper on the dynamic characteristics of the conveyor before and after the modification. The simulation test results reveal that, when coal materials are stuck, the minimum impact force of coal material on the upper sample is observed at inclination angles of 52.35° and 78.19°. The simulation research indicates that the transportation efficiency of the standard scraper and the single-sided 52.35° and 78.19° modified scraper is similar. The single-sided 78.19° scraper demonstrates the most stable vibration amplitude and centroid variance, with an overall maximum vibration amplitude and variance of 0.76 mm and 0.08, respectively. The z-direction speed fluctuation of the single-sided 78.19° scraper is also the smallest and most stable, with a maximum peak-valley difference and fluctuation variance of 0.17 m/s and 0.0004, respectively. Additionally, the force of the coal on the single-sided 78.19° scraper is the smallest and relatively stable, with a fluctuation range of 510.28∼ 18,557.71 N. Overall, the dynamic operation effect of the single-sided 78.19° scraper is deemed the best after considering all factors. This study provides valuable insights into the influence of scraper structure with different lower inclination angles on the stable operation of scraper conveyors and offers a reference for optimizing scraper structure.

Parameter study for critical heat flux under external reactor vessel cooling condition based on a mechanism model

External reactor vessel cooling has been adopted an important method to implement In Vessel Retention severe accident mitigation strategy for many advanced passive pressurized water reactors. Critical heat flux is one of the important criteria to evaluate the success or failure of this strategy. The uncertainty of engineering factors in practical design and operation conditions may make influence on critical heat flux more or less. In this paper, a parameter study for critical heat flux was carried out based on a new critical heat flux mechanism model. This mechanism model is developed based on the mechanism of liquid film dryout, and the predicted results of this model are in good agreement with the experimental results. Five important parameters, namely, coolant subcooling degree, geometry of lower head, system pressure, flow rate and heating power shape are analyzed based on this mechanism model. The results of parameter study show that the decrease of inlet coolant temperature and lower head radius are beneficial to the increase of critical heat flux. And the critical heat flux increases with the increase of system pressure. While the change of flow rate and heating power shape have little effect on critical heat flux. Under the condition of same circumference, the critical heat flux of spherical lower head is higher than that of elliptical lower head in the middle and low inclination angle region, while the trend is opposite in high inclination angle region, but not significant.

Detachment of a particle from the surface of a bubble colliding with a solid surface

The flotation of coarse mineral particles has attracted increased attentions for its advantages in early gangue rejection, reduced production of ultrafine particles, and significant energy savings during the grinding process. However, the detachment of coarse particles from the surface of bubbles could be problematic when the particle-bubble aggregates collide with the pulp-froth interface. This paper investigated the detachment of a particle from the surface of a bubble colliding with a solid surface. The rising characteristics of a particle-bubble aggregate was studied and it was found that the zigzag movement resulted in different orientations of the particle-bubble aggregates colliding with the surface. The orientation of the bubble in respective to the flat surface, characterized by the inclination angle between the bubble long axis and the flat surface, played a pronounced role in the particle detachment process. Particles were more likely to detach at low or high inclination angles. The rationale is that bubble oscillating at low inclination angle or particle sliding on the bubble surface at high inclination angle resulted in particle detachment. A neck was formed between a particle and a bubble during the detachment process, which is consistent with previous studies. The findings provide valuable insight into the phenomena of a particle detachment during the collision process of a bubble with a solid surface, which is essential to the modelling of coarse particle flotation processes and eventually contributes to the process optimization.

PSR J1953+1844 Probably Being the Descendant of an Ultracompact X-Ray Binary

PSR J1953+1844 (i.e., M71E) is a millisecond pulsar in a 53 minute binary orbit discovered by the Five-hundred-meter Aperture Spherical radio Telescope. The mass function from pulsar timing is 2.3 × 10−7 M ⊙. The possible redback origin of this system has been discussed by Pan et al. We discuss here an alternative evolution track for this binary system, namely that PSR J1953+1844 is a descendant of an ultracompact X-ray binary (UCXB), which has a hydrogen-poor donor accreting onto a neutron star (NS) with an orbital period of ≤1 hr. We noticed that some UCXB systems hold an accreting millisecond X-ray pulsar (AMXP) and a donor with a mass of about 0.01 M ⊙. M71E has a very similar orbit to those of AMXPs, indicating that it might be evolved from a UCXB similar to PSR J1653–0158. The companion star of M71E should be significantly bloated and it most probably has a carbon and oxygen composition, otherwise a low inclination angle of the orbit is required for a helium companion. The discovery of this M71E binary system may shed light on when and how an NS in a UCXB turns into a radio pulsar.

Additive manufacturing of metal-polymer hybrid parts: the influence of as-printed LPBF surface roughness on the joint strength

As-printed Laser-Powder Bed Fusion (LPBF) surfaces can provide anchoring spots for the infiltration of polymer printed by Fused Filament Fabrication (FFF), enhancing metal-polymer joint strength. This work evaluates the influence of the as-printed LPBF surface roughness and FFF parameters on the strength of Ti-6Al-4V/PA-CF joints produced by this process combination. A three-point bending testing method based on ISO 14679:1997 was deployed, whereby the energy dissipated by the joint interface was measured. Roughness was varied by 3D-printing the substrate with different inclination angles; Height and printing speed of the coating layer (the polymer layer in direct contact with the metal) were also varied. Data was interpreted using a combination between Decision Tree and Gradient Boosting Regression, ultimately suggesting that printing speed is the prominent parameter followed by inclination angle for joint strength. Additionally, the combined effect of low printing speed and inclination angle resulted in the highest energy absorption at the interface (&amp;gt;200 J).

Lower Inclination Orbit Concept for Direct-Communication-To-Satellite Internet-Of-Things Using Lean Satellite Standard in Near-Equatorial Regions

This research proposes a low-inclined orbit concept and design for the Internet-of-Things (IoT) using lean satellite standards in near-equatorial regions. The study aims to evaluate the coverage of various inclination angles at various latitudes and inclination angles in order to determine the most suitable satellite design for providing IoT coverage in these regions. The main methods applied in the study included analyzing the coverage performance of different inclination angles, the link budget analysis using simulations and the definition of the mission criteria. The results of the study show that the overall coverage performance decreases with an increase in the inclination angle. Satellites with lower inclination angles have ground tracks that are more closely aligned with the equator, while satellites with higher inclination angles have ground tracks that are inclined further toward the poles. In addition, the results show that the fraction of orbits with coverage (expressed as a percentage) declines with increasing latitude. Based on these findings, a low-inclined orbit of 24° provides the best coverage for IoT in near-equatorial regions within ±20 and 26° latitude, with a peak coverage of 27% at 24° latitude and a minimum coverage of 10% in the region spanning from 0° to ±27° latitude. This design offers more coverage time and a shorter revisit time to the selected regions for communication missions.

Sliding and rolling of yield stress fluid droplets on highly slippery lubricated surfaces

Hypothesis: Droplets of yield stress fluids (YSFs), i.e. fluids that can flow only if they are subjected to a stress above a critical value and otherwise deform like solids, hardly move on solid surfaces due to their high viscosity. The use of highly slippery lubricated surfaces can shed light on the mobility of YSF droplets, which include everyday soft materials, such as toothpaste or mayonnaise, and biological fluids, such as mucus.Experiments: The spreading and mobility of droplets of aqueous solutions of swollen Carbopol microgels were studied on lubricant infused surfaces. These solutions represent a model system of YSFs. Dynamical phase diagrams were established by varying the concentration of the solutions and the inclination angle of the surfaces.Findings: Carbopol droplets deposited on lubricated surfaces could move even at low inclination angles. The droplets were found to slide because of the slip of the flowing oil that covered the solid substrate. However, as the descending speed increased, the droplets rolled down. Rolling was favored at high inclinations and low concentrations. A simple criterion based on the ratio between the yield stress of the Carbopol suspensions and the gravitational stress acting on the Carbopol droplets was found to nicely identify the transition between the two regimes.

Design, microstructure, and mechanical property of negative Poisson's ratio porous structure fabricated by LPBF of AlCoCrFeNi2.1 eutectic high-entropy-alloy

Negative Poisson's ratio (NPR) materials are a type of structural materials that show an atypical deformation response. In general, metal-based porous materials with NPR do not have good mechanical properties due to the substrate's limited yield strength and plasticity, as the NPR behavior is unlikely to play a continuous role in the deformation. AlCoCrFeNi2.1, a eutectic high-entropy alloy (EHEA) with high yield strength and high ductility was used to fabricate the NPR structures by laser powder bed fusion (LPBF) to enhance the structures mechanical properties and NPR behavior. Structures with four different sets of structural parameters were designed for this study. The microstructure and mechanical properties of AlCoCrFeNi2.1 EHEA, synthesized by LPBF were studied, and the strength and energy absorption effect of NPR porous structure materials were investigated by static and dynamic compression experiments. Research showed the large number of inter-phase interfaces provided by the nano-scale cellular eutectic microstructure effectively restrict dislocation movement, thereby enhancing the strength and toughness of this EHEA alloy, endowing it with superior impact resistance, fracture resistance, and mechanical energy absorption. The compressive performance and the mechanical energy absorption capacity of the 3D EHEA-based NPR porous structure strongly depend on the inclination angle Ф between the thick rod and the horizontal direction in the 2D single-body model design. The strength and energy absorption of the structure with a high inclination angle of 75° material are both higher than those of the structure with a low inclination angle of 45° by almost a factor of two.

Radiographic markers of hip dysplasia in young adults: predictive effect of factors in early life

AbstracBackground and objectivesAcetabular dysplasia in young adults occurs, despite screening for developmental hip dysplasia (DDH) in the neonatal period. We aimed to examine how early life factors predict radiographic measurements of acetabular dysplasia at 18–19 years of age.MethodsFrom a previous randomized trial (n = 12,014; 1988–90) evaluating the role of hip ultrasound in newborn screening of DDH, 4469 participants (2193 males) were invited to a follow-up 18 years later (2007–09), of which 2370 (53% attendance; 932 males) met. We examined associations between early life factors and four radiographic measurements for acetabular dysplasia at skeletal maturity. Hierarchical regressions, with addition of variables observed/measured consecutively in time, were analyzed using mixed effects models considering hip as the unit in the analyses. The study is approved by the Regional Ethics Committee.ResultsIn total, 2340 participants (921 boys), mean age 18.7 years, (SD 0.6) had hip radiographs performed at follow-up and were included. Early life factors significantly predicting radiographic acetabular dysplasia at age 18–19-years included female gender, breech, low acetabular inclination (alpha) angle and sonographic instability, abduction treatment, as well as the velocity of growth during childhood. A positive family history of DDH was not associated with acetabular dysplasia at skeletal maturity.ConclusionThe acetabular inclination (alpha) angle as measured on ultrasound at birth turned out to be a significant predictor of dysplasia at 18–19 years of age. The discordant role of a positive family history in early versus adult hip dysplasia is intriguing, warranting further studies on the genetic mechanisms of DDH.

Crack propagation law of rock with single fissure based on PFC2D

In the study of pre-fabricated single-fissured rock, the failure mode, mechanical properties and propagation law of rock are affected by the length and inclination angle of fissure. In this study, artificially prepared marble-like rocks with different fissure characteristics were used as rock representatives, using PFC2D software to establish a uniaxial compression model tests for rocks with fissures. The effects of different fissure lengths and inclination angles on the failure mode and crack initiation and propagation of rock-like structures were systematically studied, revealing the mechanism of macroscopic mechanical behavior of rocks containing single fissures in the process of crack initiation, propagation, and failure at the micro-level. The results show that: 1) Failure mode of the rock sample is mainly controlled by fissure inclination angle and fragmentation degree is mainly controlled by fissure length. 2) The initiation stress, damage stress, and peak stress of rock samples during loading deformation increase with the increase of fissure inclination angle, and decrease with the increase of fissure length. The crack initiation angle decreases with the increase of the fissure inclination angle. 3) Crack initiation characteristics: at a low fissure inclination angle (α&amp;lt; 45°), the crack initiation position has a certain offset to the center of the prefabricated fissure, or starts from the tip of the prefabricated fissure. At high fissure inclination angles (α≥45°), the crack initiates from the tip of the prefabricated fissure and forms a “dispersed” distribution. 4) The crack propagation law is mainly shear cracks, at a low fissure inclination angle (α&amp;lt; 45°), the crack propagation has obvious aggregation band formation. At high fissure inclination angles (α≥45°), the crack aggregation zone gradually weakened and expanded in the direction of dispersion.

Mechanical properties and failure law of composite rock containing two coplanar fractures

Composite rocks comprise the rock structures that are commonly used in geotechnical engineering. The fracture configuration has a substantial influence on the mechanical behavior, failure mode, and crack propagation of composite rocks. In this study, we considered a composite rock with two prefabricated coplanar fractures. Through laboratory uniaxial compression tests and using a digital image acquisition system, we systematically studied the effects of different fracture lengths and inclination angles on the mechanical properties and failure characteristics of the rocks. We obtained the following results: 1) during the loading deformation of the rock sample, the peak stress and elastic modulus increased with an increase in the fracture inclination angle and decreased with an increase in the fracture length. The deterioration coefficient k (the ratio of the difference between the peak strength of intact and fractured rock sample to that of intact rock sample) decreased with an increase in the fracture inclination angle and increased with an increase in the fracture length. 2) The failure type of the rock samples was primarily controlled by the fracture inclination angle and material of the two rock types, and the fragmentation degree was primarily controlled by the fracture length. With an increase in the fracture inclination angle, the failure mode of rock sample exhibited the following order of changes leading to failure: a double-Y type (trwo wing and one antiwing cracks appeared on each prefabricated fracture) → double-Z type (two wing cracks appeared on each prefabricated fracture) → Z type (one wing crack appeared on each prefabricated fracture). 3) The type of coalescence of the rock bridge was controlled by the fracture inclination angle and structural plane. The crack positions were primarily affected by the fracture length. 4) At a low fracture inclination angle (α ≤ 30°), the propagation of the microcracks showed aggregated band formation. Above moderate fracture inclination angles (α &amp;gt; 30°), the microcrack aggregation band gradually weakened and expanded in the direction of dispersion.