Strength and failure characteristics of sandstone containing two circular holes filled with two types of inclusions under uniaxial compression

Plate shaped sandstones containing two fabricated circular holes that were filled with gypsum and high-strength concrete respectively were prepared for studying the effects of ligament length L ligament incline angle α, as well as filling modes on their strength properties and failure modes. The results show that the initial cracks can be categorized as wing crack, axial tensile crack and curved tensile crack. The failure modes of ligaments can be categorized as mode of single inclined crack, mode of single axial crack and mode of two parallel cracks. The final failure modes of all specimens can be categorized as the tension-shear mixed failure and shear failure. The strength of inclusions shows little influence on the final failure modes of specimens, while the failure modes vary with L and α. When α is a fixed value, the peak strength σc and elastic modulus Ec of tested specimens increase firstly with increasing L and reaches to the maximum value at L of 16 mm, then declines. When L is a fixed value, σc declines firstly and then turns to increase as α increases to 75° from 45°, while Ec increases linearly. The axial stress σp performs the similar variation trends with those of σc versus increasing L and α when ligaments fail.

Mechanical properties and energy evolutions of burst-prone coal samples with holes and fillings

During the mining process of impact-prone coal seams,drilling pressure relief can reduce the impact propensity of the coal seam,but it also reduces the integrity and strength of the coal mass at the side of the roadway.Therefore,studying the mechanical properties and energy evolution rules of coal samples containing holes and filled structures has certain practical significance for achieving coordinated control of coal mine rockburst disasters and the stability of roadway surrounding rocks.To achieve this aim,seven types of burst-prone coal samples were prepared and subject to uniaxial compression experiments with the aid of a TAW-3000 electro-hydraulic servo testing machine.Besides,the stress–strain curves,acoustic emission signals,DIC strain fields and other data were collected during the experiments.Furthermore,the failure modes and energy evolutions of samples with varying drilled hole sizes and filling materials were analyzed.The results show that the indexes related to burst propensity of the drilled coal samples decline to some extent compared with those of the intact one,and the decline is positively corelated to the diameter of the drilled hole.After hole filling,the strain concentration degree around the drilled hole is lowered to a certain degree,and polyurethane filling has a more remarkable effect than cement filling.Meanwhile,hole filling can enhance the strength and deformation resistance of coal.Hole drilling can accelerate the release of accumulated elastic strain energy,turning the acoustic emission events from low-frequency and high-energy ones to high-frequency and low-energy ones,whereas hole filling can reduce the intensity of energy release.The experimental results and theoretical derivation demonstrate that hole filling promotes coal deformability and strength mainly by weakening stress concentration surrounding the drilled holes.Moreover,the fillings can achieve a better filling effect if their elastic modulus and Poisson’s ratio are closer to those of the coal body.

Hydromassage of macular hole edges for large and persistent full-thickness macular holes

●AIM:To introduce the macular hole(MH)hydromassage technique as a potentially beneficial approach for the treatment of large or persistent MH.●METHODS:This retrospective observational case series comprised 16 consecutive patients(17 eyes)diagnosed with MH.Inclusion criteria involved a hole aperture diameter larger than 600μm or the presence of an unclosed MH larger than 600μm following the previous vitrectomy.Standard MH repair procedures were administered in all cases,involving the manipulation and aspiration of the hole margin through the application of water flow with a soft-tip flute needle.A comprehensive assessment was conducted for each case before and after surgery,and optical coherence tomography(OCT)images were captured at every follow-up point.●RESULTS:The mean preoperative aperture diameter was 747±156μm(range 611-1180μm),with a mean base diameter of 1390±435μm(range 578-2220μm).Following surgery,all cases achieved complete anatomical closure of MH,with 13 cases(76.5%)exhibiting type 1 closure and 4 cases(23.5%)demonstrating type 2 closure.No significant differences were observed in the preoperative OCT variables between the two closure types.Eyes with type 1 closure showed a significantly improved visual acuity(0.70±0.10,range 0.50-0.80)compared to those with type 2 closure(0.90±0.12,range 0.80-1.00,P=0.014).●CONCLUSION:The MH hydromassage technique demonstrates promising results,achieving acceptable closure rates in cases of large or persistent MH.This technique may serve as an effective adjunctive maneuver during challenging MH surgery.

Investigation on photonic crystal nanobeam cavity based on mixed diamond–circular holes

A photonic crystal nanobeam cavity(M-PCNC)with a structure incorporating a mixture of diamond-shaped and circular air holes is pro-posed.The performance of the cavity is simulated and studied theoretically.Using thefinite-difference time-domain method,the parameters of the M-PCNC,including cavity thickness and width,lattice constant,and radii and numbers of holes,are optimized,with the quality factor Q and mode volume Vm as performance indicators.Mutual modulation of the lattice constant and hole radius enable the proposed M-PCNC to realize outstanding performance.The optimized cavity possesses a high quality factor Q 1.45105 and an ultra-small mode=×volume Vm 0.01(λ/n)[Zeng et al.,Opt Lett 2023:48;3981–3984]in the telecommunications wavelength range.Light can be progres-=sively squeezed in both the propagation direction and the perpendicular in-plane direction by a series of interlocked anti-slots and slots in the diamond-shaped hole structure.Thereby,the energy can be confined within a small mode volume to achieve an ultra-high Q/Vm ratio.

Statistical study of magnetic holes in the upstream region of Mercury’s bow shock

Magnetic holes are magnetic depression structures that exist widely in many plasma environments.The magnetic holes with durations of>1 s in the solar wind at Mercury’s orbit have drawn much attention,but the properties of the magnetic holes with shorter durations are still unclear.Here,we investigate the magnetic holes with durations of 0.1-100 s in the upstream region of Mercury’s bow shock based on observations by the MESSENGER(MErcury Surface,Space ENvironment,GEochemistry,and Ranging)spacecraft.They can be divided into two groups according to the distribution of their duration:small-duration magnetic holes(SDMHs,<0.6 s)and large-duration magnetic holes(LDMHs,>0.6 s).The duration of each group approximately obeys a log-normal distribution with a median of~0.25 s and 3 s,respectively.Approximately 1.7%(32.6%)of the SDMHs(LDMHs)reduce the magnetic field strength by more than 50%.For both groups,some structures have a linear or quasi-linear polarization,whereas others have an elliptical polarization.The magnetic hole events in both groups tend to have a higher rate of occurrence when the interplanetary magnetic field strength is weaker.Their occurrence rates are also affected by Mercury’s foreshock,which can increase(decrease)the occurrence rate of the SDMHs(LDMHs).This finding suggests that Mercury’s foreshock might be one source of the SDMHs and that the foreshock can destroy some LDMHs.These observations suggest that a new group of magnetic holes with durations of<0.6 s exist in the upstream region of Mercury’s bow shock.

Supermassive Primordial Black Holes for Nano-Hertz Gravitational Waves and High-redshift JWST Galaxies

Recently,observational hints for supermassive black holes have been accumulating,prompting the question:Can primordial black holes(PBHs)be supermassive,particularly with masses M■10^(9)M_(⊙)?A supercritical bubble,containing an inflating baby universe,that nucleated during inflation can evolve into a PBH in our observable universe.We find that when the inflaton slowly transitions past a neighboring vacuum,the nucleation rate of supercritical bubbles inevitably peaks,leading to a mass distribution of multiverse PBHs with a peak mass up to M■10^(11)M_(⊙).Thus,our mechanism naturally provides a primordial origin for supermassive black holes.

Triple points and phase transitions of D-dimensional dyonic Ad S black holes with quasitopological electromagnetism in Einstein–Gauss–Bonnet gravity

By considering the negative cosmological constant Λ as a thermodynamic pressure, we study the thermodynamics and phase transitions of the D-dimensional dyonic Ad S black holes(BHs) with quasitopological electromagnetism in Einstein–Gauss–Bonnet(EGB) gravity. The results indicate that the small/large BH phase transition that is similar to the van der Waals(vdW) liquid/gas phase transition always exists for any spacetime dimensions. Interestingly, we then find that this BH system exhibits a more complex phase structure in 6-dimensional case that is missed in other dimensions.Specifically, it shows for D = 6 that we observed the small/intermediate/large BH phase transitions in a specific parameter region with the triple point naturally appeared. Moreover, when the magnetic charge turned off, we still observed the small/intermediate/large BH phase transitions and triple point only in 6-dimensional spacetime, which is consistent with the previous results. However, for the dyonic Ad S BHs with quasitopological electromagnetism in Einstein–Born–Infeld(EBI) gravity, the novel phase structure composed of two separate coexistence curves observed by Li et al. [Phys. Rev. D105 104048(2022)] disappeared in EGB gravity. This implies that this novel phase structure is closely related to gravity theories, and seems to have nothing to do with the effect of quasitopological electromagnetism. In addition, it is also true that the critical exponents calculated near the critical points possess identical values as mean field theory. Finally, we conclude that these findings shall provide some deep insights into the intriguing thermodynamic properties of the dyonic Ad S BHs with quasitopological electromagnetism in EGB gravity.

Generalized Newton’s Theory of Universal Gravitation and Black Holes

The Newton’s theory of universal gravitation is generalized. Significantly strong at short distances central interaction of bodies and particles is established in comparison with Newtonian. A connection is found with Black Holes, with the horizon of events. Possibility of systematization of all Black Holes is shown. An illustration is given on the example of Black Hole SgrA*.

Quantum Unruh Effect on Radiation of Black Holes

The quantum Unruh effect on radiation of a gravitational object including a black hole is analyzed and calculated. It is surprisingly found that the well-known Hawking radiation of a black hole is not physical. Applying the Stephan-Boltzmann law with the use of the Unruh radiation temperature at the surface of a black hole to calculate the power of radiation of the black hole is conceptually unphysical. This is because the Unruh radiation temperature results from the gravitational field of the object rather than from the thermal motion of matter of the object, so that the Stephan-Boltzmann law is not applicable. This paper shows that the emission power of Unruh radiation from a gravitational object should be calculated in terms of the rate of increase of the total Unruh radiation energy outside the object. The result obtained from this study indicates that a gravitational object can emit Unruh radiation when the variation of its mass and radius satisfies an inequality of dM/M > 1.25dR/R. For a black hole, the emission of Unruh radiation does not occur unless it can loose its mass (dM < 0). The emission power of Unruh radiation is only an extremely tiny part of the rate of mass-energy loss if the black hole is not extremely micro-sized. This study turns down our traditional understanding of the Hawking radiation and thermodynamics of black holes.

Algorithm of Detecting and Filling Small Holes in Triangular Mesh Surface

In some scattered point cloud triangular mesh restoration algorithm, small triangular mesh holes problem will often affect the quality of the model. For small holes at the details, this paper propose a method for identifying and extracting hollow edge,and use a triangle growth way based on boundary edge angle to fill the empty void. First, according the relationship of the point, side and face of the triangle mesh model to identify the hole, then extracting the holes boundary edge and classifying it. Finally, using a triangle growth method based on holes boundary edge angle to fill each small holes separated from the boundary. Compared with other algorithm of filling holes, this method is high efficiency for small holes of smooth surface,and itimprovesthe quality of the triangular mesh model.

Influence of Soft Filler on Stress Concentration Factor of Elliptic Holes in a Rectangular Plate

Finite element models were established to analyze the influence of soft filler on stress concentration for a rectangular plate with an elliptic hole in the center. The influence was quantified by means of stress concentration factor (SCF). Seven shape factors of the elliptic hole and three levels of elasticity modulus of the soft filler were considered. The reduction coefficient and sensitivity index of SCF are the two indicators in evaluating the influence of soft filler. It was found that the reduction coefficient of SCF increases significantly as the shape factor and the elasticity modulus of the filler increase, indicating that soft filler can reduce the concentrated stress effectively, especially when the shape factor is great. Analysis for the sensitivity index of SCF indicates that SCF is more sensitive to materials with small elasticity modulus than to materials with large one.

Are Black Holes 4-D Spatial Balls Filled with Black Body Radiation? Generalization of the Stefan-Boltzmann Law and Young-Laplace Relation for Spatial Radiative Transfers

This is the first paper in a two part series on black holes. In this work, we concern ourselves with the event horizon. A second follow-up paper will deal with its internal structure. We hypothesize that black holes are 4-dimensional spatial, steady state, self-contained spheres filled with black-body radiation. As such, the event horizon marks the boundary between two adjacent spaces, 4-D and 3-D, and there, we consider the radiative transfers involving black- body photons. We generalize the Stefan-Boltzmann law assuming that photons can transition between different dimensional spaces, and we can show how for a 3-D/4-D interface, one can only have zero, or net positive, transfer of radiative energy into the black hole. We find that we can predict the temperature just inside the event horizon, on the 4-D side, given the mass, or radius, of the black hole. For an isolated black hole with no radiative heat inflow, we will assume that the temperature, on the outside, is the CMB temperature, T2 = 2.725 K. We take into account the full complement of radiative energy, which for a black body will consist of internal energy density, radiative pressure, and entropy density. It is specifically the entropy density which is responsible for the heat flowing in. We also generalize the Young- Laplace equation for a 4-D/3-D interface. We derive an expression for the surface tension, and prove that it is necessarily positive, and finite, for a 4-D/3-D membrane. This is important as it will lead to an inherently positively curved object, which a black hole is. With this surface tension, we can determine the work needed to expand the black hole. We give two formulations, one involving the surface tension directly, and the other involving the coefficient of surface tension. Because two surfaces are expanding, the 4-D and the 3-D surfaces, there are two radiative contributions to the work done, one positive, which assists expansion. The other is negative, which will resist an increase in volume. The 4-D side promotes expansion whereas the 3-D side hinders it. At the surface itself, we also have gravity, which is the major contribution to the finite surface tension in almost all situations, which we calculate in the second paper. The surface tension depends not only on the size, or mass, of the black hole, but also on the outside surface temperature, quantities which are accessible observationally. Outside surface temperature will also determine inflow. Finally, we develop a “waterfall model” for a black hole, based on what happens at the event horizon. There we find a sharp discontinuity in temperature upon entering the event horizon, from the 3-D side. This is due to the increased surface area in 4-D space, AR(4) = 2π2R3, versus the 3-D surface area, AR(3) = 4πR2. This leads to much reduced radiative pressures, internal energy densities, and total energy densities just inside the event horizon. All quantities are explicitly calculated in terms of the outside surface temperature, and size of a black hole. Any net radiative heat inflow into the black hole, if it is non-zero, is restricted by the condition that, 0cdQ/dt FR(3), where, FR(3), is the 3-D radiative force applied to the event horizon, pushing it in. We argue throughout this paper that a 3-D/3-D interface would not have the same desirable characteristics as a 4-D/3-D interface. This includes allowing for only zero or net positive heat inflow into the black hole, an inherently positive finite radiative surface tension, much reduced temperatures just inside the event horizon, and limits on inflow.

Construction and Weight Distributions of Binary Linear Codes Based on Deep Holes

Deep holes are very important in the decoding of generalized RS codes, and deep holes of RS codes have been widely studied, but there are few works on constructing general linear codes based on deep holes. Therefore, we consider constructing binary linear codes by combining deep holes with binary BCH codes. In this article, we consider the 2-error-correcting binary primitive BCH codes and the extended codes to construct new binary linear codes by combining them with deep holes, respectively. Furthermore, three classes of binary linear codes are constructed, and then we determine the parameters and the weight distributions of these new binary linear codes.

How Dark Energy Might Be Produced by Black Holes

If confirmed, the new galactic observations in support of rapidly growing supermassive black holes in association with their production of dark energy may provide for a quantum leap forward in our understanding of black holes, dark energy, and universal expansion. The primary implication of these observations is that growth of black holes may well be coupled with universal expansion (“cosmological coupling”). Study of the Flat Space Cosmology (FSC) model, in conjunction with these new observations, suggests a novel mechanism of “black hole dark energy radiation”. This brief note gives a rationale for how the high gravitational energy density vacuum within or adjacent to a black hole horizon could be sufficiently energetic to pull entangled pairs of positive matter energy particles and negative dark energy “particles” of equal magnitude out of the horizon vacuum and send them off in opposite directions (i.e., gravitationally-attractive matter inward and gravitationally-repelling dark energy outward). One effect would be that a black hole can rapidly grow in mass-energy without mergers or the usual accretion of pre-existing matter. A second effect would be continual production of dark energy within the cosmic vacuum, fueling a continuous and finely-tuned light-speed expansion of the universe.

Black Holes and the Third Law of Thermodynamics Revisited

Black holes contradict the Nernst-Planck (N/P) version of the 3rd law of thermodynamics, but agree with its unattainability (U) version. This happens without contradiction, because the N/P and U versions are not equivalent, namely, N/P implies U but U does not imply N/P. So, black holes obey the weaker version of the 3rd law, but not the stronger one.

A New Proposal for Black Holes

The understanding of what a black hole is like is not easy and may not yet be well understood. The introduction of canonical quantization into the issue has not been significant to our understanding. However, introducing affine quantization, a new procedure, offers a very unusual expression that seems to be plausible, and quite profound as well.

Adiabaticity Violated Not Enough: Presume Primordial Black Holes to Generate Gravitons for Cosmological Constant, as Candidate for DE Initially

Instant preheating as given in terms of window where adiabaticity is violated is a completely inefficient form of particle production if we use Padmandabhan scalar potentials. This necessitates using a very different mechanism for early universe gravition production as an example which is to break up the initial “mass” formed about 1060 times Planck mass into graviton emitting 105 gram sized micro black holes. The mechanism is to assume that we have a different condition than the usual adiabaticity idea which is connected with reheating of the universe. Hence, we will be looking at an earlier primordial black hole generation for generation of gravitons.

Trials to Resolve Black Holes Instabilities in Brane World Cosmology Models

In this letter, we report on our trials to remove the instability of black holes in brane world cosmological models consisting of two branes and a bulk. In order to resolve this problem, general types of interaction potentials were employed. Careful analyses have shown that although the black holes instabilities were removed, a sort of arbitrariness adherent to the motion of the two branes towards each other has taken place leading to an unstable system. Thus, the models seem to us rather paradoxical.

From Black Holes to Information Erasure: Uniting Bekenstein’s Bound and Landauer’s Principle

This research aims to integrate Bekenstein’s bound and Landauer’s principle, providing a unified framework to understand the limits of information and energy in physical systems. By combining these principles, we explore the implications for black hole thermodynamics, astrophysics, astronomy, information theory, and the search for new laws of nature. The result includes an estimation of the number of bits stored in a black hole (less than 1.4 × 1030 bits/m3), enhancing our understanding of information storage in extreme gravitational environments. This integration offers valuable insights into the fundamental nature of information and energy, impacting scientific advancements in multiple disciplines.

Spherical and Circular Non-Equatorial Photon Orbits around Kerr Black Holes

By analytically solving the equation of azimuthal null geodesics for spherical photon trajectories, a parametric representation of the corresponding segment of the orbit is obtained. The solution parameter is the latitude coordinate. The dependences of the orbital radius on the black hole spinning parameter and the angle of inclination of its plane with respect to the rotation axis are calculated for flat circular non-equatorial orbits. It is proved that all spherical photon trajectories in the Kerr spacetime are unstable, as well as equatorial ones, and the critical photon orbits in the Schwarzschild metric.