Hole Radius Research Articles

Bifurcation of the Maxwell quasinormal spectrum on asymptotically anti–de Sitter black holes

We study the Maxwell quasinormal spectrum on asymptotically anti-de Sitter black holes with a set of two Robin type boundary conditions, by requiring the energy flux to vanish at asymptotic infinity. Focusing, for illustrative purposes, on Schwarzschild-anti-de Sitter black holes both without and with a global monopole, we unveil that, on the one hand, the Maxwell quasinormal spectrum bifurcates as the black hole radius increases for both boundary conditions, which is termed the mode split effect; while on the other hand, with an appropriate fixed black hole radius but increasing the monopole parameter, the first (second) boundary condition may trigger (terminate) the mode split effect.

Tailoring anisotropic absorption in a borophene-based structure via critical coupling.

The research of two-dimensional (2D) materials with atomic-scale thicknesses and unique optical properties has become a frontier in photonics and electronics. Borophene, a newly reported 2D material, provides a novel building block for nanoscale materials and devices. We present a simple borophene-based absorption structure to boost the light-borophene interaction via critical coupling in the visible wavelengths. The proposed structure consists of borophene monolayer deposited on a photonic crystal slab backed with a metallic mirror. The numerical simulations and theoretical analysis show that the light absorption of the structure can be remarkably enhanced as high as 99.80% via critical coupling mechanism with guided resonance, and the polarization-dependent absorption behaviors are demonstrated due to the strong anisotropy of borophene. We also examine the tunability of the absorption behaviors by adjusting carrier density and lifetime of borophene, air hole radius in the slab, the incident angle and polarization angle. The proposed absorption structure provides novel access to the flexible and effective manipulation of light-borophene interactions in the visible and shows a good prospect for the future borophene-based electronic and photonic devices.

Moment capacity of back-to-back cold-formed steel channels with edge-stiffened holes, un-stiffened holes, and plain webs

The use of cold-formed steel (CFS) back-to-back channels as floor joists is increasing steadily, and such beams often include un-stiffened holes for installation of services, which reduces their flexural strength due to the reduced web area. A new generation of CFS channels with edge-stiffened holes has been widely used. However, no research has been undertaken to understand the effects of composite actions on moment capacity of such built-up beams. In this paper, fourteen new experiments are reported on back-to-back channels with various hole spacing, which were tested under four-point loading. Finite-element models were also established and validated with the experiments. Upon validation, a parametric study involving 63 FEMs was conducted to investigate the effects of beam length, diameter of hole, stiffener length and fillet radius. The test results show that for back-to-back channels with five edge-stiffened holes, the moment capacity increased by 15.4%, compared to that of a plain channel. For comparison, the same section with un-stiffened holes had a 15.1% reduction in moment capacity. Test results also show that distortional buckling was the predominant failure mode for all cases. The test and FE results were compared against the design moment capacities predicted by the American Iron and Steel Institute (AISI) and Australian and New Zealand Standards (AS/NZS) for plain channels. For channels with holes, design procedure was proposed by Moen and Schafer. It is revealed that these equations are conservative by around 23% and 49% for CFS channels with un-stiffened and edge-stiffened holes, respectively.

A geometrical interpretation for the properties of multiband optical variability of the blazar S5 0716+714

We present the results of multiband observations of the blazar S5 0716+714 intra-night variability performed during 23 nights in the period from 04.2014 through 04.2015. The bluer-when-brighter trend is detected in both intra- and inter-night data. We assume that the jet component crossing the region where the medium becomes transparent to the optical radiation forms almost all optical emission of S5 0716+714. Deviations of some parts of the component from the general trajectory of the component can cause the Doppler factor of these parts to increase. Various maximum Doppler factors achieved by these parts of the component and different volumes occupied by them with the concave synchrotron self-absorption spectrum result in both the observed various color index behavior in variability and explain the absence of dependence of the bluer-when-brighter behavior on the object magnitude. We estimated spectral maximum frequency νm≈(0.6−1.7)·1014 GHz from intra- and inter-night data. Assuming that the size of emitting region is comparable with the gravitational radius of a black hole with a mass of 5·108 solar masses, the magnetic field obtained from synchrotron self-absorption is B∼102−104 G, which corresponds to the values of other independent estimations. The obtained values of νm and B confirm our assumption about the nature of the blazar S5 0716+714 region radiating in the optical range.

Realizing Mie resonances in air by means of eccentric hollow metallic cylinders

In this paper, we report the realization of Mie resonances in air using eccentric hollow metallic cylinders. Our numerical results show that electric resonances/magnetic resonances can be selectively generated in a properly-designed eccentric hollow metallic cylinder under TE-/TM-polarization plane wave illuminations, respectively. We find that the critical dimension for Mie resonance generation is the radius of the hollow hole. Finally, two resonant modes supported by a dual-hole cylinder are presented. This study can be highly favorable to various applications, including optical sensing and nonlinear optics.

Probing within the Bondi radius of the ultramassive black hole in NGC 1600

ABSTRACT We present deep (250 ks) Chandra observations of the nearby galaxy group NGC 1600, which has at its centre an ultramassive black hole (17 ± 1.5 billion M⊙). The exceptionally large mass of the black hole coupled with its low redshift makes it one of only a handful of black holes for which spatially resolved temperature and density profiles can be obtained within the Bondi radius with the high spatial resolution of Chandra. We analysed the hot gas properties within the Bondi accretion radius R$_{\mbox{B}}=1.2\!-\!1.7\:\mathrm{ arcsec}= 0.38\!-\!0.54 \,{\mbox{kpc}}$. Within a ∼3 kpc radius, we find two temperature components with statistical significance. Both the single-temperature and two-temperature models show only a very slight rise in temperature towards the centre, and are consistent with being flat. This is in contrast with the expectation from Bondi accretion for a temperature profile which increases towards the centre, and appears to indicate that the dynamics of the gas are not being determined by the central black hole. The density profile follows a relatively shallow ρ ∝ r−[0.61 ± 0.13] relationship within the Bondi radius, which suggests that the true accretion rate on to the black hole may be lower than the classical Bondi accretion rate.

Biosensor Based on Photonic Crystal Fibre with Mode Coupling of a Dual-Core

In recent years, photonic biosensors have attracted increasing attention due to the enormous range of applications in many fields to which they may be put, including medical diagnostics, environment monitoring, organic chemical detection, temperature sensing, and work with magnetic fields. In this work, photonic crystal fibre (PCF) was utilised as a biosensor using a Finite Element Method (FEM). Several important optical sensor properties such as the field distribution profiles, the real part of the effective refractive index and the relative sensitivity of the proposed PCF structure are affected by mode coupling between the fundamental mode and the second order super mode of the inner and outer cores, respectively. These properties were thus those studied by applying FEM. The proposed biosensor can thus be used for bio-sensing, as the holes in the PCF are filled with analytes. Relatively high sensitivity can thus be obtained using appropriate design by selecting design parameters such as the radius of holes in the cladding region and pitch distance, or distance between the centres of neighbouring holes, appropriately. The results from this work show that the electric field distribution is affected by mode coupling between the outer and inner modes; the effects of mode coupling of the PCF on the relative sensitivity were also determined.

Mechanism and characteristics of a tunable dispersion-compensating dual-ring microstructure fiber for different orbital angular momentum modes.

A tunable dual-ring microstructure fiber that can support stable transmission for different orbital angular momentum (OAM) states and possess ultrahigh dispersion coefficients and low confinement losses is proposed and theoretically investigated. The proposed fiber is composed of two high-refractive-index rings and a double-cladding structure. Owing to the central air core and outer cladding, the dual-ring structure can support stable transmission for the OAM states. The mode fields of different OAM states in the inner ring can spread to the outer ring under certain conditions, which leads to high absolute values of dispersion around the coupling wavelengths. By tuning the refractive indices of the dual rings, the proposed fiber can achieve dispersion control for different OAM modes. Moreover, the specially designed two-layer air holes in the inner cladding can affect the mode-coupling coefficients, which are characterized by the effective mode areas and the overlap integral of the electric fields between the resonant ring modes. Therefore, the dispersion curves and operating wavelengths of the OAM modes can be modulated by regulating the physical parameters (the radius of the two-layer air holes or the infiltrated functional materials) of the inner cladding. We built a theoretical model and analyzed the modulation method and mechanism of the dispersion curves based on the coupled mode theory. The theoretical results indicate that the proposed fiber is flexible and has potential dispersion-compensating applications in fiber OAM systems.

Analysis of GaN-based 2D Photonic Crystal Sensor for Real-time Detection of Alcohols

The present research proposes an extensive assay of photonic band gap (PBG) characteristics for transverse electric field polarization in two-dimensional (2D) photonic crystal (PhC) structures, with a vision to sense different groups of alcohol like methanol, ethanol, propanol, butanol and phenol. The plane wave expansion (PWE) technique is implemented for realization of PBG in two types of lattice configurations such as square lattice and triangular lattice with circular air holes. Various structure parameters like radius of the circular air holes, lattice constant, nature of the background material, arrangement of air holes and period of air holes are meticulously optimized for envisaging a complete band gap. A variety of unpredicted trends are observed in the simulation outcomes, which include a substantial shift in band gap width, band gap size, reflected wavelength, reflected light intensity and transmitted light intensity for different types of alcohols. Also, the effect of air filling fraction on the band gap size has been investigated by selecting different radius of circular air holes. Apart from this, high sensitivity of 1645 nm/RIU and resolution of $$6.07\times {10}^{-5}$$ RIU is attained with the proposed structures, which pave the path for different bio-sensing applications.

Design of hollow core step-index antiresonant fiber with stepped refractive indices cladding.

With the benefits of low latency, wide transmission bandwidth, and large mode field area, hollow-core antiresonant fiber (HC-ARF) has been a research hotspot in the past decade. In this paper, a hollow core step-index antiresonant fiber (HC-SARF), with stepped refractive indices cladding, is proposed and numerically demonstrated with the benefits of loss reduction and bending improvement. Glass-based capillaries with both high (n = 1.45) and low (as low as n = 1.36) refractive indices layers are introduced and formatted in the cladding air holes. Using the finite element method to perform numerical analysis of the designed fiber, results show that at the laser wavelengths of 980 and 1064 nm, the confinement loss is favorably reduced by about 6 dB/km compared with the conventional uniform cladding HC-ARF. The bending loss, around 15 cm bending radius of this fiber, is also reduced by 2 dB/km. The cladding air hole radius in this fiber is further investigated to optimize the confinement loss and the mode field diameter with single-mode transmission behavior. This proposed HC-SARF has great potential in optical fiber transmission and high energy delivery.

Studies on calculation method and bandgap properties of a nonlocal piezoelectric phononic crystal nanoplate

By introducing nonlocal elastic theory and Kirchhoff plate theory to plane wave expansion (PWE) method, the band structure of a nonlocal piezoelectric phononic crystal (PC) nanoplate is calculated. A complete band gap with magnitude order gigahertz (GHz) is opened. In order to investigate the characteristics of such a band gap in detail, the corresponding influence rules of thermo-electro-mechanical coupling fields, nonlocal effects and geometric parameters on band gaps are studied. During the researches, temperature variation, electrical voltage and external axial force are picked as the influencing parameters corresponding to thermo-electro-mechanical coupling fields. Nonlocal coefficient is chosen as the influencing parameter related to surface effects. Lattice constant, PZT-4 hole radius and nanoplate thickness are picked as the influencing parameters of geometric parameters. All the results are expected to be of help for nano electro mechanical system (NEMS) based on piezoelectric periodic nanoplates.

Field Tests and Three-Dimensional Semi-Analytical Boundary Element Method Analysis of a Row of Holes as Active Barrier in Saturated Soil

Abstract The adverse effects of ground vibrations can be eliminated or prevented by installation of various types of wave barriers, such as a row of holes. The analysis is accomplished with the aid of a series of field experiments and numerical simulation. Three-dimensional semi-analytical boundary element models are established to use a row of holes as active wave barrier to isolate the ground vibrations generated by the machine foundation laid on the surface of saturated soil foundation, and the effects of the model parameters on isolation effectiveness are investigated and discussed in detail. A simple single program multiple data parallel algorithm is developed with the aid of Matlab software to increase calculating efficiency. The results show that a row of holes can isolate the ground vibrations successfully. Increasing the radius and the depth and decreasing the net spacing between two successive holes can all result in an increase in the screening effectiveness. According to the results, it is suggested in the design that the hole radius should take the value of 0.1∼0.15λR (λR is the Rayleigh wave length), and the hole depth and the net spacing should take the value no more than 1.0λR and 0.1λR, respectively. Moreover, the distance between the machine foundation and barrier can affect the screening effectiveness, and the larger the distance is, the poorer the screening effectiveness is. The number of holes in a row has less effect on the screening effectiveness. However, the bigger the number of holes in a row is, the larger the screening zone behind the barriers is.

Stress-strain state of spherical shells with two unequal holes

This article presents the results of a numerical study of the stress concentration around two equal and unequal holes in an orthotropic spherical shell made of composite materials under the action of internal pressure. The influence of geometric (hole radii, shell thickness, distance between holes) characteristics, as well as material orthotropy and shear stiffness, on the stress state of spherical shells made of composite materials is studied. A numerical algorithm based on the finite element method has been developed and a software package has been implemented on a computer that allows solving the problem of stress concentration near two unequal holes in spherical shells made of composite materials.

Моделювання процесу однозернового дозування вакуумним пневмомеханічним висівним апаратом

The aim of this work is to determine the influence of the surface shape and geometric parameters of the suction hole on the uniformity of seed distribution along the length of the row and determine its rational parameters. The use of mathematical modeling significantly speeds up the research process. An algorithm and a program in the Mathcad system have been developed for simulating the process of separating seeds from the cylindrical, conical and toroidal surfaces of the suction holes of a vacuum pneumomechanical sowing device and their fall to the bottom of the furrow. The algorithm is based on the results of previous studies by the authors. Its initial data is the simulation with the help of a generator of random numbers of spherical seed sizes, which are distributed according to the truncated normal law. Each seed undergoes a process of separation from the surface of the suction hole and free fall to the bottom of the furrow. Computer experiments are repeated, changing the average seed diameters, surface type and geometric parameters of the suction hole surface. As a result of statistical processing of the obtained vector of intervals between adjacent seeds at the bottom of the furrow, the mean sample value of the interval between seeds and the standard deviation of the intervals are determined. The last indicator is chosen by the criterion of uniformity of distribution of seeds on length of a line. Graphs of dependence of this indicator on the investigated parameters are constructed. As a result of the analysis of graphs it was found that the uniformity of seed distribution along the length of the row deteriorates with decreasing average seed diameter and increasing the radius of the suction hole. With a conical surface of the suction hole, the highest uniformity of seed distribution along the row length is achieved at a cone angle γ = 60 ° and a maximum diameter dmaxк=(1,7–2,0) rсем. The highest uniformity of seed distribution along the length of the row can be achieved with a toroidal surface of the suction hole, in particular, with a minimum radius of the radial section of the torus.

The Interaction between Microcapsules with Different Sizes and Propagating Cracks

The microcapsule-contained self-healing materials are appealing since they can heal the cracks automatically and be effective for a long time. Although many experiments have been carried out, the influence of the size of microcapsules on the self-healing effect is still not well investigated. This study uses the two-dimensional discrete element method (DEM) to investigate the interaction between one microcapsule and one microcrack. The influence of the size of microcapsules is considered. The potential healing time and the influence of the initial damage are studied. The results indicate that the coalescence crack is affected by the size of holes. The elastic modulus, the compressive strength and the coalescence stress decrease with the rising radius of holes. The initial damage in experiments should be greater than 95% of the compressive strength to enhance the self-healing effect. The large microcapsules require slight initial damage. Both a new type of displacement field near the crack and a new category of coalescence crack are observed. The influence of sizes of holes on the cracking behavior of concrete with a circular hole and a pre-existing crack is clarified.

Optical Chirality Enhancement in Hollow Silicon Disk by Dipolar Interference

AbstractOptical chirality enhancement is highly demanded for enantioselective interaction of circularly polarized light with chiral molecules. The chirality enhancement in the coaxial air hole of a hollow silicon disk depends on three aspects, namely, the enhancements of electric and magnetic fields and a factor determined by the phases of their field components. In the spectral regime of dipole resonances, maximum chirality enhancement with sign consistency and uniform spatial distribution in the air hole can be obtained in association with both magnetic dipole resonance and anapole. Due to dipolar interference, the chirality is nulled at their coincidence, around which the sign of chirality is reversed. Maximum chirality with both positive and negative signs can be found between magnetic dipole resonance and anapole in the vicinity of their coincidence. This situation is maintained under size scaling so that the operation wavelength can be broadly tuned. The optical chirality can be further improved by merely adjusting the hole radius, by which the optimal spatially averaged optical chirality enhancement factor can reach 39 and −23. The simple strategy for optimizing Mie resonators presented in this work may benefit the design of Mie resonator‐based achiral metasurfaces for chirality detection application.

Remarks on dynamic cohesive fracture under static pre-stress — with a comparison to finite fracture mechanics

The role of inertia effects during crack formation under non-singular static pre-stress is investigated by utilizing a linear softening cohesive zone model. In case of a 1D tensile bar, the closed-form solution shows that during the finite time of decohesion about one third of the released strain energy is converted into kinetic energy. In case of crack initiation from a circular hole in a 2D plate under remote tension or compression, results from dynamic finite element analyses utilizing the same cohesive zone model are compared with predictions from finite fracture mechanics which assumes the spontaneous formation of a finite crack increment. While both methods capture the overall critical load for crack initiation at the hole well, the highly transient process of crack nucleation (not accounted for by finite fracture mechanics) is resolved by the numerical cohesive zone model analyses and displays a complex dependence on the hole radius.

Surface Plasmon Resonance Sensor Based on Polymer Liquid-Core Fiber for Refractive Index Detection

In this work, a surface plasmon resonance (SPR) sensor based on a novel liquid-core polymer optical fiber (POF) is proposed and numerically analyzed for refractive index (RI) detection. The polytetrafluoroethylene (PTFE) fiber is selected as the platform for SPR sensing. We combine the PTFE-based POF with the liquid-core structure by introducing a hole filled with analyte into the fiber center. The hole also acts as the fiber core to guide the incident light. This design helps to realize the detection of solutions with low RI values (around 1.33), while keeping the distinguished sensing characteristics of the liquid-core structure. Two side air holes are introduced into the cladding and a thin silver film protected by a titanium dioxide layer is plated on the wall of one air hole, which helps to control the mode coupling. In order to optimize the design of this sensor, the impacts of parameters such as metal layer thicknesses and the central hole radius are investigated using the full-vector finite element method (FEM). After optimization, our design shows a wavelength interrogation sensitivity reaching up to 16,750 nm/RIU and an average full-width at half-maximum (FWHM) of 42.86 nm in the RI range of 1.325–1.35.

Design of a microstructure optical fiber supporting 52 vortex beams

We propose a newly designed optical fiber with a microstructure based on SiO2 that supports the transmission of 52 vortex beams. By optimizing the radius of the center air hole and small air holes encircling the center air hole, the effective refractive index difference between adjacent vortex beams is higher than 10−4, which is large enough to support the transmission of vortex beams. Through a numerical analysis, the dispersion of vortex beams is lower than 189.00 ps ⋅ nm−1⋅ km−1 and maintains a flat trend. The confinement loss is as low as 10−9 dB ⋅ m−1 at 1550 nm, and the nonlinear coefficient of the vector modes is on the order of 10−4. The HE31 mode has the longest stable transmission distance among the vector modes, 630.83km at 1550nm. The vortex beams’ purity is analyzed to quantify the spin–orbit coupling (SO coupling) effect. The modes’ purity is higher as the topological charge (L) increases, and the spin–orbit aligned modes’ purity is higher than the spin–orbit anti-aligned mode at the same L. The MOF’s geometric parameters affect vortex beams’ purity.

Origin and Physical Properties of the Black Hole

A new physical model is proposed for the appearance of an astronomical object - the Black Hole. It is shown that the Black Hole is the center of the cosmic, etheric, gravitational torsion. An equation for determining the radius of this object based on the theory of vortex gravity is presented. A substantiation is proposed that the force of gravity on the surface of the Black Hole does not depend on the mass of this Black Hole. The mass of the Black Hole can not be determined. A contradiction is shown in the Schwarzschild solution by the definition of the radius of the Black Hole.