Hole Parameters Research Articles

Mass, charge, and distance to Reissner–Nordström black hole in terms of directly measurable quantities

In this paper, we employ a general relativistic formalism and develop new theoretical tools that allow us to analytically express the mass and electric charge of the Reissner–Nordström black hole as well as its distance to a distant observer in terms of few directly observable quantities, such as the total frequency shift, aperture angle of the telescope, and redshift rapidity. Our analytic and concise formulas are valid on the midline, and the redshift rapidity is a relativistic invariant observable that represents the evolution of the frequency shift with respect to the proper time in the Reissner–Nordström spacetime. This procedure is applicable for particles undergoing circular motion around a spherically symmetric and electrically charged black hole, which is the case for accretion disks orbiting supermassive black holes hosted at the core of active galactic nuclei. Although this type of black hole is expected to be electrically neutral, our results provide a novel method to measure the electric charge of the Reissner–Nordström black hole, hence can shed some light on this claim. Besides, these results allow us to measure the mass of the black hole and its distance from the Earth, and we can employ the general formulas in black hole parameter estimation studies.

Analysis of Dyonic ModMax black hole through accretion disk

In the present study, we probe the geodesic motion and accretion of particles around the spherically symmetric Dyonic ModMax black hole using isothermal fluid. The geodesic motion of the particles around the black hole leads to the formation of disk like structure during the accretion process. We compute the radiant temperature, radioactive efficiency, radiant flux energy, circular orbits and observe the behavior of particles within stable circular orbits in the equatorial plane. We examine how the particles are perturbed during the process by using restoring forces and the oscillatory behavior of the particles surrounding a compact object and also investigate the fluid’s critical flow and maximum accretion rate. Our findings demonstrate how the black hole parameter γ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma $$\\end{document} and charge Q affect the circular geodesic of particles as well as the maximum accretion rate of the Dyonic ModMax black hole.

Experimental and numerical simulation investigation of the deformation characteristics of vertical boreholes under non-uniform horizontal principal stress

To study borehole deformation under non-uniform horizontal principal stress in the deep strata, a prediction method for horizontal principal stress was developed based on the morphological parameters of boreholes, the deformation trajectory equation for the standard circular borehole was derived based on elasticity theory, and the morphological characteristics of boreholes were analyzed. Additionally, a quantitative relationship between the geometric parameters of elliptical boreholes and horizontal principal stress was established. Subsequently, uniaxial tests on borehole deformation were conducted to verify elliptical deformation under non-uniform horizontal principal stress. A combined deductive, experimental, and numerical simulation approach to borehole deformation analysis was adopted, and the impact factors of borehole deformation were obtained. The results indicated as following: (1) the deformation morphology of borehole under non-uniform horizontal principal stress was elliptical; (2) for the given lithology, the greater the difference in horizontal principal stress, the greater were the ellipticity and elliptical deformation of borehole; (3) for given stress background, rock strength was inversely proportional to ellipticity. Additionally, the smaller the Young’s modulus and compressive strength, the larger was the Poisson’s ratio and the larger was the ellipticity. For example, the ellipticity of mudstone and coal was greater than that of limestone and sandstone; (4) with an increase in load, the displacement of borehole wall exhibited three stages: initial micro-deformation, accelerated deformation, and stable deformation; (5) horizontal principal stress can be calculated by using the morphological parameters (long and short axes) of an elliptical hole. Furthermore, a horizontal principal stress method theory can be developed based on the morphological parameters of boreholes. The results of our study can provide new ideas and methods for the measurement of in situ stress in deep boreholes and a theoretical basis for the development of equipment for measuring elliptical boreholes.

Research on Damping Hole Optimization of Hydro-Pneumatic Suspension for Mining Trucks under Variable Load Conditions

The hydro-pneumatic suspension, known for enhancing vehicle ride comfort and stability, finds widespread use in engineering vehicles. Presently, the majority of mining trucks employ hydro-pneumatic suspension with a fixed damping hole, underscoring the critical importance of selecting appropriate damping hole parameters. Initially, an equilibrium mathematical model of the ¼ hydro-pneumatic suspension is established, and the influencing factors of the damping characteristics are analyzed. Subsequently, the simulation model and experimental bench for the hydro-pneumatic suspension are constructed. Sinusoidal signals with different frequencies and amplitudes serve as the excitation signals to analyze the variation trend of the force on the rod with displacement changes. The simulation and experimental results demonstrate a high degree of consistency, validating the rationality and validity of the simulation model. Building upon this foundation, various damping apertures are then selected to study the damping characteristics of the hydro-pneumatic suspension. The research indicates that as the damping aperture increases, the setting time of the hydro-pneumatic suspension system after excitation extends, accompanied by a decrease in the acceleration overshoot. As a result, a comprehensive evaluation index is developed, considering various factors, such as different weight setting times and peak longitudinal accelerations to assess the ride comfort of the suspension. This approach is then employed to determine the optimal damping aperture under both full-load and no-load conditions. The findings of this research offer valuable insights for the development of adaptive variable damping hydraulic suspensions, especially under variable load conditions.

ARTPOL: Analytical ray-tracing method for spectro-polarimetric properties of accretion disks around Kerr black holes

Spectro-polarimetric signatures of accretion disks in X-ray binaries and active galactic nuclei contain information on the masses and spins of their central black holes, as well as the geometry of matter in proximity to the compact objects. This information can be extracted by means of X-ray polarimetry. In this work, we present a fast analytical ray-tracing technique for polarized light (ARTPOL) that helps us to obtain the spinning black hole parameters from the observed properties. This technique can replace the otherwise time-consuming numerical ray-tracing calculations for any optically thick or geometrically thin accretion flow. For the purposes of illustration, we considered a standard optically thick, geometrically thin accretion disk in the equatorial plane of the Kerr black hole. We show that ARTPOL proves accurate for dimensionless spin parameter a ≤ 0.94 with a speed that is over four orders of magnitude faster than direct ray-tracing calculations. This approach opens up broader prospects for direct fittings of the spectro-polarimetric data from the Imaging X-ray Polarimetry Explorer.

Vibration reduction effect of retaining pile structure under the action of damping hole—A case study

In the context of mitigating the impact of blasting-induced seismic waves on excavation processes and reducing the vibrational load on retaining pile structures, this study examines the influence of predetermined damping hole parameters on the damping effect. It also evaluates the protective efficacy of damping holes on retaining pile structures. Leveraging the foundation pit project at the Julong Avenue Station of Wuhan Metro Line 7 as a reference, on-site blasting construction was monitored to obtain vibration velocities at the top of the retaining pile structure. A numerical calculation model for blasting in the foundation pit was established using LS-DYNA software, and its reliability was verified through the integration of on-site monitoring data at the top of the retaining pile. Multiple damping hole excavation schemes were devised, and their effects on the damping effectiveness were analyzed with respect to various parameters. Safety criteria for the stability of the retaining pile structure were proposed based on the ultimate tensile stress criterion, ultimate shear stress criterion, and Mohr’s criterion. Under the optimized scheme, the dynamic response characteristics of the retaining pile structure were analyzed, and the practical application effects on-site were observed. The research findings indicate that the depth, spacing, and number of damping holes have a significant impact on the damping effect. The safety criterion for the vibrational velocity of the retaining pile structure during blasting is determined to be 26.10 cm/s. Under the optimized scheme, the vibrational velocities at various monitoring points on the retaining pile structure all fall within the safe range, with a maximum reduction rate of 30.9%.

Observational redshift from general spherically symmetric black holes

In this work, we obtain an expression for the total observational frequency shift of photons emitted by massive geodesic particles circularly orbiting a black hole in a general spherically symmetric background. Our general relations are presented in terms of the metric components and their derivatives that characterize the black hole parameters. As a concrete example of this general relativistic approach, a special case is studied by applying the formalism to a nonsingular black hole conformally related to the Schwarzchild solution that possesses a length scale parameter l and an integer parameter N in addition to the black hole mass. Besides, we express the nonsingular black hole mass in terms of the observational redshift/blueshift. Finally, we investigate the effects of the free parameters of the conformal gravity theory on the observational frequency shift and compare results with those of the standard Schwarzschild black hole.

Damage analysis and safety control of surrounding rock around peripheral hole of diversion tunnel

The control of overbreak in blasting excavation is a significant technical challenge and a subject of extensive research in the field of engineering. This study examines the damage characteristics of the surrounding rock in a tunnel section through blasting test and numerical simulation conducted as part of the San Gavan diversion tunnel project in Peru. The orthogonal test of peripheral holes under the influence of explosive spacing, blasthole spacing and smooth blasting layer thickness was designed to analyze the characteristics of rock damage under different parameter combinations and the influence of various factors on rock damage. Based on the USBM formula, this paper deduces a mathematical model considering blasthole spacing and explosive spacing to predict the rock damage range. The main conclusions are as follows: on the tunnel section, the average damage range of vault and arch springer is slightly larger than that of spandrel and haunch. For a single blasthole, the rock damage range in different sections is: explosive > air > stem, and the degree of rock damage at the bottom of blasthole is the highest. Smooth blasting layer thickness has a significant effect on rock damage rate on the side of non-reflect boundary. When smooth blasting layer thickness is 45 cm and 55 cm, the boundary conditions of numerical model have a significant effect on the rock damage. The reflection of blasting stress wave on the free surface leads to the further increase of rock damage range. The blasthole spacing and explosive spacing have a significant effect on rock damage range on the side of non-reflect boundary, and both show a negative correlation. Based on the prediction model of rock damage, the combination of peripheral hole parameters satisfying the standard is obtained, which provides guidance for blasting design.

Electromagnetic and gravitational radiation of blazar OJ 287

Based on long-term monitoring data of the blazar, a new model for determining the parameters of this close binary supermassive black hole (SMBH) is proposed. The model uses the laws of celestial mechanics and results of harmonic analysis of observational data obtained mainly in the radio and optical wavelength ranges. Within the framework of the proposed model, the masses of SMBH companions, the values of their orbital elements, the parameters of the accretion disk, and its dimensions and thickness were determined. The structure and dynamics of SMBHs and their interaction with the accretion disk are considered. It is shown that OJ 287 may be the most massive close binary SMBH with comparable masses. The obtained characteristics of the SMBH are used to estimate the level of gravitational wave radiation, the lifetime of the system before the merger, as well as the magnitude of changes in the orbits of the companions.

The quantum density of states and distribution functions of the helium-3: Wigner approach in path integral Monte Carlo simulations

A new path integral representation of the quantum density of states (DOS) and distribution functions of strongly correlated fermions are derived in the Wigner formulation of quantum mechanics. A new path integral Monte Carlo approach to calculate DOS and thermodynamic functions is suggested. Using 3 He as an interesting example, we calculate the DOS, internal energy distribution (IED), momentum distribution functions (MDFs), spin-resolved radial distribution functions at different densities and temperatures. The physical meaning and parameters of exchange-correlation holes, the quantum oscillations of IEDs and DOS as well as the high-momentum asymptotics (‘quantum tails’) of MDFs have been considered and explained.

Determination of the Parameters of Binary Supermassive Black Holes and the Level of Their Gravitational Radiation

Determination of the Parameters of Binary Supermassive Black Holes and the Level of Their Gravitational Radiation

An Experimental Analysis of the Seed-Filling Mechanism of Maize-Precision Hole-Planter Clamping

Because the operating speed of current mechanical maize hole seeders is low and their ability to adapt to the seed is poor, an active clamping-type precision hole planter for corn was designed. Here, we explain its structural composition and working principle. According to the maize kernel size, the combination of hole parameters is based on the principle of virtual work on analyzing the seed extraction disc assembly’s static mechanical model. The model was imported into the ADAMS simulation for validation and the parameters and ranges affecting the seed-filling performance were identified. By further analyzing the results of the coupled ADAMS–EDEM simulation, the “arching” process of the seeds during leakage charging was revealed, and an arch-breaking method was proposed with the help of a swinging seed-collecting slider. The speed of the hole planter, the diameter of the outer edge of the gravity ring, and the angle of the block installation were used as test factors. The Box–Behnken center-combination simulation test was conducted using the sowing pass index, re-seeding index, and missed sowing index as evaluation indices. The experimental results show that the optimal parameter combination was as follows: gravity ring = 174.3 mm, stopper installation angle = 131.9°, and hole seeder speed = 85.2 rpm. At this time, the qualified seeding index was 94.53%, the multiple indices were 4.30%, and the leakage index was 1.18%. Under these conditions, the row seeding performance bench test was conducted to obtain the qualified seeding index of the hole seeder, which was 93.36%, while the multiple indices were 5.20% and the leakage index was 1.44%, which satisfied the agronomic requirements of precision seeding. This provides a theoretical reference for mechanical seeding methods for irregular seeds, as well as a basis for the research and development of maize precision sowing machinery and equipment.

Study on Fatigue Life of Aluminum Alloy 6061-T6 Based on Random Defect Characteristics.

A certain number of hole-like defects will occur in aluminum alloys under cyclic loading. The internal holes will reduce the strength of the material and cause stress concentration, which will aggravate the development of fatigue damage. A classification method of defect features based on X-ray CT damage data is proposed. The random hole distribution model is established through the linear congruence method and the region division method. The hole parameter is introduced as the intermediate variable of the 3D reconstruction model of internal defects. In the mesoscopic stage, the function relationship between the distribution of random holes and the fatigue life is established based on the coupling relationship between the number and proportion of pores and the fatigue life. In the macroscopic stage, the relationship between the random holes and the macroscopic crack growth life is established by taking the crack length as the damage variable. The crack propagation rate decreased with the increase in the number of holes. The prediction model of the whole life stage is established using the life function from microcrack initiation to macroscopic crack propagation. Finally, the validity of the whole stage fatigue life prediction model is demonstrated through the comparison and verification of experiments, which provides a certain engineering value for the life estimation of 6061-T6 aluminum alloy materials.

Follow-up on the Supermassive Black Hole Binary Candidate J1048+7143: Successful Prediction of the Next Gamma-Ray Flare and Refined Binary Parameters in the Framework of the Jet Precession Model

Analyzing single-dish and very long baseline interferometry radio, as well as Fermi Large Area Telescope γ-ray observations, we explained the three major flares in the γ-ray light curve of FSRQ J1048+7143 with the spin–orbit precession of the dominant mass black hole in a supermassive black hole binary system. Here, we report on the detection of a fourth γ-ray flare from J1048+7143, appearing in the time interval that was predicted in our previous work. Including this new flare, we constrained the mass ratio into a narrow range of 0.062 < q < 0.088, and consequently we were able to further constrain the parameters of the hypothetical supermassive binary black hole at the heart of J1048+7143. We predict the occurrence of the fifth major γ-ray flare that would appear only if the jet will still lay close to our line of sight. The fourth major γ-ray flare also shows the two-subflare structure, further strengthening our scenario in which the occurrence of the subflares is the signature of the precession of a spine–sheath jet structure that quasiperiodically interacts with a proton target, e.g., clouds in the broad-line region.

Determining parameters of Kerr black holes at finite distance by shadow observation

Determining parameters of Kerr black holes at finite distance by shadow observation

The impact of preoperative parameters on postoperative foveal displacement in idiopathic macular hole

This study examined the effect of vitrectomy combined with internal limiting membrane (ILM) peeling on foveal displacement in 42 eyes with idiopathic macular hole (IMH). A retrospective analysis was conducted to measure various macular hole parameters before surgery, including basal diameter, minimum diameter, hole height, and areas affected by traction such as macular hole area (MHA), macular hole cystoid space area (MHCSA), macular hole retinal area (MHRA), and total area (TA). The results showed a postoperative shift of the fovea towards the optic disc in all cases. Notably, the extent of foveal displacement was significantly linked to the preoperative basal diameter (rs = 0.405, P = 0.008) but not to other preoperative parameters or postoperative visual acuity. Furthermore, the study found that the temporal side of the macular hole was more affected by traction than the nasal side preoperatively, leading to greater postoperative displacement (All P < 0.05).

Exploring the shadow of a rotating charged ModMax black hole

Abstract The research presented in this paper discusses the impact that the parameters of charge (Q) and screening factor (γ) have on properties of the horizon and silhouette of rotating charged ModMax black holes which were reviewed in [Eur. Phys. J. C (2022) 82:1155] recently, building upon previous findings in the field. Furthermore, the study explores the behavior of null geodesics, which can help us better understand the apparent shape of the black hole’s silhouette, as well as the distortion parameter and approximate radii of the silhouette that are influenced by the aforementioned parameters, and there are some values of parameter Q which corresponds to data from the Event Horizon Telescope (EHT). Notably, we explore the distortion parameter and approximate radii of the silhouette, revealing that while an increase in γ leads to a growth in silhouette radius (R s ), it simultaneously reduces the distortion rate (δ s ). Conversely, heightened Q charge results in a reduction of R s accompanied by an increase in δ s . Lastly, the paper analyzes the effects of the black hole’s parameters on the effective potential and energy emission: the peak value of the energy emission rate experiences a decrease as the screening factor (γ) increases, while it increases with higher values of the charge parameter (Q).

Numerical study of a novel cooling protection scheme with rail crown holes for the squealer tip in a turbine blade

The squealer tip is acknowledged as an effective and dependable design for minimizing leakage loss and reducing thermal load in high-pressure turbine blades. After confirming the numerical approach, this study explored the cooling and aerodynamic characteristics of a novel cooling protection scheme with rail crown holes in a squealer tip. The rail crown hole parameters including the hole number, size, and distribution are research variable. Evaluation indexes of cooling and aerodynamic performance are the tip surface adiabatic film cooling efficiency (η) and clearance leakage flow rate (LFR). In cooling aspects, increasing the hole number or the hole size can improve the coolant attachment to the rail crown surface under the same coolant mass flow rate (Q). The coolant distribution within the cavity is substantially improved by concentrating the film holes at the leading-edge rail, which enhances the cooling protection of the cavity floor. In aerodynamic aspects, at low Q conditions, the total LFR correlates only with Q and is less sensitive to hole parameters. At high Q conditions, enlarging the hole size proves more effective in suppressing total LFR. Additionally, three cases with optimal cooling effects are chosen to investigate the impact of Q. These three cases are the scheme with an increasing hole number (case 1), the scheme with an enlarging hole size (case 4), and the scheme with concentrated holes at the leading edge (case 5). The results show that case 5 consistently exhibits superior cooling protection for the cavity floor in all Q conditions. For average η of the rail crown surface, cases 1 and 5 reach the peak value of average η at Q = 1.0Q0, while case 4 attains its peak value at Q = 1.5Q0.

The particle dynamics around rotating charged black holes with Weyl corrections

In this article, particle dynamics around charged rotating black holes with Weyl corrections is discussed. First, the metric is studied for its horizon structure and scalar curvature invariants. The effects of Weyl corrections on circular motion of the particles is analyzed around central object. We have shown dependency of effective potential, energy, angular momentum and inner most stable circular orbits on black hole parameters. We have also determined center of mass energy expression for collision of two neutral particles. In the Penrose process of energy extraction, it has been found that efficiency is not that much higher as compared to the other modified rotating black holes.

Quasinormal Modes and Greybody Factors of de Sitter Black Holes Surrounded by Quintessence in Rastall Gravity

AbstractIn this work, the quasinormal mode, greybody factors, and absorption cross section of de Sitter Reissner‐Nordström black hole surrounded by quintessence field in Rastall gravity are studied. The violation of energy‐momentum conservation has a non‐linear effect on the quasinormal modes. With an increase in the black hole charge, both real parts of quasinormal modes i.e. oscillation frequency of ring‐down Gravitational Waves (GWs) and damping or decay rate of GWs increase non‐linearly. A similar observation is made for the black hole structural parameter also, however in this case the variation is almost linear. The remnant mass of a black hole depends on different physical parameters of a black hole. In the case of greybody factors also, both parameters have similar impacts are observed. With an increase in these parameters, greybody factors decrease. Moreover, the null geodesics and the impact of Rastall gravity on the light trajectory are also investigated. Our study suggests that the presence of a surrounding quintessence field may shadow the existence of black hole charges in such black hole configurations.