Symmetric Hole Research Articles

Influence of Screw Angulation on the Mechanical Properties on a Polyaxial Locking Plate Fixation.

Polyaxial locking systems are widely used for strategic surgical placement, particularly in cases of osteoporotic bones, comminuted fractures, or when avoiding pre-existing prosthetics. However, studies suggest that polyaxiality negatively impacts system stiffness. We hypothesize that a new plate design, combining a narrow plate with asymmetric holes and polyaxial capabilities, could outperform narrow plates with symmetric holes. Three configurations were tested: Group 1 with six orthogonal screws, and Groups 2 and 3 with polyaxiality in the longitudinal and transverse axes, respectively. A biomechanical model assessed the bone/plate/screw interface under cyclic compression (5000 cycles) and torsion loads until failure. Screws were inserted up to 10° angle. None of the groups showed a significant loss of stiffness during compression (p > 0.05). Group 1 exhibited the highest initial stiffness, followed by Group 3 (<29%) and Group 2 (<35%). In torsional testing, Group 1 achieved the most load cycles (29.096 ± 1.342), while Groups 2 and 3 showed significantly fewer cycles to failure (6.657 ± 3.551 and 4.085 ± 1.934). These results confirm that polyaxiality, while beneficial for surgical placement, reduces biomechanical performance under torsion. Despite this, no group experienced complete decoupling of the screw-plate interface, indicating the robustness of the locking mechanism even under high stress.

Scalar's quasibound states in cosmological black hole background

In this letter, we present in detail a novel exact solution of scalar quasibound states of a static spherically symmetric Schwarzschild de Sitter black hole. We investigate and work out the governing covariant scalar field wave equation, i.e., the Klein-Gordon equation and isolate the radial equation. In this letter, we show in detail, the derivation of the successfully obtained exact radial wave solutions which are expressed in terms of General Heun functions. Having the exact solutions in hand, the energy levels expression is obtained from special function's polynomial condition. In the last part, the Hawking radiation is investigated via the Damour-Ruffini method and the Hawking temperature is obtained from radiation distribution function.

D-type photonic crystal fiber refractive index sensor based on Bloch surface waves

Bioassays are important in health assessment, disease diagnosis, treatment monitoring, disease prevention, and environmental monitoring to provide better health management and quality of life for individuals and society. A D-type photonic crystal fiber optic sensor based on Bloch surface waves is proposed for biological detection within an ultra-wide refractive index. The designed D-type fiber was side-polished and alternately deposited with one-dimensional photonic crystals (1DPCs) on the polished side, consisting of a set of TiO2 and SiO2 alternating media with moderate refractive index differences. The designed PCF consists of symmetric air holes and polished structures. The structural parameters of this sensor are also analyzed and discussed in order to obtain better detection performance. The designed Bloch surface wave D-type photonic crystal fiber optic sensor has a maximum refractive index sensitivity of 5400 nm/RIU and a maximum amplitude sensitivity of 513.00RIU−1. The sensor also has a resolution of 1.85×10−5RIU and an excellent maximum quality factor (FOM) of 222.43RIU−1. These results show a higher figure of merit (FOM) than conventional methods, resulting in increased sensitivity and accuracy. The proposed sensor can detect the RI of unspecified analytes between 1.20 and 1.50, allowing for the analysis of many different types of analytes, such as viruses, blood plasma, cancer cells, sugars, proteins, DNA/RNA, and many more.

Design of aluminum plate phononic crystals with wide bandgaps via free-form shape optimization using deep neural networks

Phononic crystals (PnCs) with a broad bandgap have been the subject of extensive research, particularly for their capacity to manipulate elastic waves efficiently. However, the explored design space remains relatively limited, and the shapes under consideration are often relatively simple. This study optimizes a free-form hole shape for square and hexagonal lattice aluminum plate PnCs with high relative bandgaps (i.e., ratio of bandgap to its center frequency). Optimization is implemented by leveraging the predictive capabilities of deep neural networks (DNNs). For both types of lattices, an initial training dataset is made up of 20,000 randomly generated PnCs unit cells, each containing a symmetric smooth hole. The relative bandgap is subsequently evaluated using the Finite Element Method (FEM). For each lattice, one Deep Neural Network (DNN) is trained to predict the relative bandgap, while another DNN is used to classify whether the bandgap exists. The predictive power of DNNs is exploited to search for design candidates with high relative bandgaps using the genetic optimization algorithm (GOA). The relative bandgaps of new candidates are determined and validated using FEM. The results of these analyses are then utilized to update the DNNs through active learning (AL) techniques. As a result, the relative bandgaps of the progressively refined hole shapes for square and hexagonal lattices are 2.382 and 10.383 times larger, respectively, than those of circular holes.

Symmetric acridine bridging hole transport material for perovskite solar cell

Carbazole derivatives are widely used as electron donors for the construction of hole transport materials (HTMs) for perovskite solar cells (PSCs), whose performance depends strongly on the structure and properties of the π-bridges. In this paper, we report a new HTM, ACR-Cz-DM, using 9,10-dihydroacridine (ACR) as a π-bridge and N3,N6-bis(9,9-dimethyl-9H-fluoren-2-yl)-N3,N6-bis(4-methoxyphenyl)-9H-carbazole-3,6-diamine (Cz-DM) as a peripheral electron donor. Cz-DM well satisfies the need of the ACR core for a peripheral donor with weak electron donation and high conjugation capacity. Owing to the excellent hole mobility and conductivity, good film formation and outstanding charge extraction and transport ability of ACR-Cz-DM, the photoelectric conversion efficiency (PCE) of FAPbI3-based PSCs using ACR-Cz-DM as HTM attained 21.37%, which is better than that of Spiro-OMeTAD-based PSCs (20.10%) under the same conditions. This work provides a promising demonstration of the design principles of ACR-based HTMs.

Effect of crack flank holes on fatigue crack growth

The effect of drilling two symmetric holes along the crack flanks on the fatigue crack growth (FCG) rate was evaluated numerically. The FCG increases (decreases) when the crack tip is behind (ahead) the holes. This behaviour is enlarged both by increasing the diameter of the holes and by reducing the distance between them. This is consequence of the geometrical effect, which modifies the plastic zone size. Experimental work validated the numerical model, indicating that that cumulative plastic strain at the crack tip is an adequate crack driving force and that cyclic plastic deformation is the main damage mechanism of FCG.

Low-cost novel X-shaped hole transport materials for efficient perovskite solar cells: Molecular modelling of the core and schiff base effects on photovoltaic and photophysical properties

Eight molecules with D-π-D molecular motifs coded HTM(1-4)a,b were designed as efficient symmetric hole transporting materials for perovskite solar cells. These HTMs are composed of different core moieties, such as spiro [fluorene-9,9′-xanthene]-diol (SFO), spiro [fluorene-9,9′-xanthene]-dimethoxy (SFM), benzo [c][1,2,5]thiadiazole (BTD), and biphenyl (BP) and are gaining lot of attention because of their low-cost, reproducible electrical and optical properties in device performance. Detailed information about the energetic of molecular levels (GSOP/ESOP), first singlet excitation energy (E0-0), equilibrium molecular geometry, charge separation, charge transfer, reorganization energies, polarizability and hyperpolarizability, density of states (DOS), solubility and stability of these molecules was attained by systematically performing molecular modeling calculations using density functional theory (DFT) and time dependent-DFT calculations utilizing hybrid density functional B3LYP using the basis set 6–31g(d,p) level of theory as a successful method for predicting the photophysical and photovoltaic properties of these conjugated systems. The results showed that not only the core moieties, but also Schiff-base linkage extended conjugation, have an effect on the photophysical and photovoltaic properties of the proposed HTMs. It was demonstrated that HTMs incorporating SFO (HTM1a,b), SFM (HTM2a,b), and BP (HTM4a,b) achieved better charge transport, high stability values (ηa = 2.11–2.40 eV), low electron-hole binding energy (Eb = 0.16–0.21 eV) than HTM3a,b with BTD core, which improves hole mobility and decreases recombination, all of which improved device photocurrent, which can be attributed to the extended π-conjugation in SFO, SFM and BP cores. These findings are strikingly similar to those of Spiro-OMeTAD (ηa = 2.45 eV, Eb = 0.16 eV), indicating that these HTMs are promising candidates for efficient and cost-effective PSCs. Interestingly, when the stability of HTM(1-4)a and HTM(1-4)b was compared, it was clear that HTM(1-4)a has lower stability than HTM(1-4)b, which could be attributed to the presence of Schiff base CN bonds in HTM(1-4)b, which reduces the molecules stability when compared to HTM(1-4)b, owing to a strong C–C linkage. Meanwhile, HTM(1-4)a outperforms HTM(1-4)b in terms of electronic performance and hole mobility.

Dewetting Process in Ni-Mn-Ga Shape-Memory Heusler: Effects on Morphology, Stoichiometry and Magnetic Properties

In this work, dewetting process has been investigated in shape-memory Heuslers. To this aim, series of high-temperature annealing (1100–1150 K) have been performed at high vacuum (time is varied in the range of 55–165 min) in Ni-Mn-Ga epitaxial thin films grown on MgO(001). The process kinetics have been followed by studying the evolution of morphology and composition. In particular, we report the initiation of the dewetting process by the formation of symmetric holes in the films. The holes propagate and integrate, leaving micrometric and submicron islands of the material, increasing the average roughness of the films by a factor of up to around 30. The dewetting process is accompanied by severe Ga and Mn sublimation, and Ni-Ga segregation, which significantly modify the magnetic properties of the films measured at each stage. The annealed samples show a relatively weak magnetic signal at room temperature with respect to the pristine sample.

3D printed enucleated eye holder for research and surgical training

AbstractPurpose: The aim of this study is to provide an affordable eye holder to secure enucleated eyes for the purposes of ophthalmology surgical training or research. Whilst mannequin heads are an excellent tool for surgical training, a surgical microscope is pre‐requisite to accommodate this. Table top microscopes are widely available and commonly used for both research and surgical training, however, there are a limited number of available products to secure the eye reliably in this setting. We present a 3D‐printed enucleated eye cup holder that can be mass produced as a low‐cost training tool.Methods: Using Solidworks, we designed a 3D printable modular device that consists of three pieces forming an eye cup holder. The main cup has 8 symmetric round holes to secure the eye in the horizontal and vertical planes either on recti muscles, their insertions, conjunctiva or episclera using sutures. This provides a customizable level of stability to allow precise surgery that can be made more repeatable for research purposes and surgical training. Two support pillars mount the main cup on an optical board which is placed under the microscope. The main cup can be reprinted for replacement conveniently and can be customised to adapt to different microscope dimensions and different cadaveric eyes.Results: This system has been tested on cadaveric porcine and human eyes in both training and research environments. During the operation, the main cup is placed on the base of the microscope and mounted on the optical board underneath by support pillars. The whole system is fixed on optical board to achieve better stability as well as adaptability to different microscopes. Other equipment can be added on the optical board for further tests. The eyes are sutured securely on the holder and the position is adjustable. Ophthalmologists and trainees were able to practice appropriately on the system. This system was affordable at a cost of approximately €24 to print.Conclusions: Herein, we present a 3D‐printed enucleated eye cup holder that can be secured to the base of a microscope using an optical board. The adjustable positioning of the eye via suturing provides a convenient surgical training and research experience. The holder is released as an open‐source computer‐aided design file with customizable dimensions for interested trainees and researchers.image

An infinity of black holes

In general relativity (without matter), there is typically a one parameter family of static, maximally symmetric black hole solutions labeled by their mass. We show that there are situations with many more black holes. We study asymptotically anti-de Sitter solutions in six and seven dimensions having a conformal boundary which is a product of spheres cross time. We show that the number of families of static, maximally symmetric black holes depends on the ratio, λ, of the radii of the boundary spheres. As λ approaches a critical value, λ c , the number of such families becomes infinite. In each family, we can take the size of the black hole to zero, obtaining an infinite number of static, maximally symmetric non-black hole solutions. We discuss several applications of these results, including Hawking–Page phase transitions and the phase diagram of dual field theories on a product of spheres, new positive energy conjectures, and more.

Annihilation-to-nothing: DeWitt boundary condition inside a black hole

In canonical quantum gravity, the wave function for a hypersurface inside a Schwarzschild black hole can be obtained by solving the Wheeler–DeWitt equation. What is of prime importance is the behavior of the wave function for the future boundary near the singularity, and the DeWitt boundary condition implies that it should vanish here. In this paper, we provide several generalizations, and new interpretations, of the DeWitt boundary condition. First, we summarize existing works on the wave function inside the black hole to justify the DeWitt boundary condition. Next, we investigate the wave function for the collapsing null shell to show that due to the reflection symmetry in space and time, there exists a destructive interference near the singularity and hence a vanishing boundary condition can be natural. If we extend this point of view to the black hole spacetime itself, then the DeWitt boundary condition is equivalent to saying that there exists a symmetric anti-black hole contribution, such that eventually these two geometries are annihilated-to-nothing near the quantum transition surface. This symmetric model can be realized within black hole models of loop quantum gravity with a novel interpretation for the arrow(s) of time.

Spinor-induced instability of kinks, holes and quantum droplets

We address the existence and stability of one-dimensional (1D) holes and kinks and two-dimensional (2D) vortex-holes nested in extended binary Bose mixtures, which emerge in the presence of Lee–Huang–Yang (LHY) quantum corrections to the mean-field energy, along with self-bound quantum droplets. We consider both the symmetric system with equal intra-species scattering lengths and atomic masses, modeled by a single (scalar) LHY-corrected Gross–Pitaevskii equation (GPE), and the general asymmetric case with different intra-species scattering lengths, described by two coupled (spinor) GPEs. We found that in the symmetric setting, 1D and 2D holes can exist in a stable form within a range of chemical potentials that overlaps with that of self-bound quantum droplets, but that extends far beyond it. In this case, holes are found to be always stable in 1D and they transform into pairs of stable out-of-phase kinks at the critical chemical potential at which localized droplets turn into flat-top states, thereby revealing the connection between localized and extended nonlinear states. In contrast, we found that the spinor nature of the asymmetric systems may lead to instability of 1D holes, which tend to break into two gray states moving in the opposite directions. Remarkably, such instability arises due to spinor nature of the system and it affects only holes nested in extended modulationally-stable backgrounds, while localized quantum droplet families remain completely stable, even in the asymmetric case, while 1D holes remain stable only close to the point where they transform into pairs of kinks. We also found that symmetric systems allow fully stable 2D vortex-carrying single-charge states at moderate amplitudes, while unconventional instabilities appear also at high amplitudes. Symmetry also strongly inhibits instabilities for double-charge vortex-holes, which thus exhibit unexpectedly robust evolutions at low amplitudes.

Wrinkling suppression in thin membranes using designed geometrical features

The rapidly increasing use of thin membranes; especially in the fabrication of flexible electronics, has motivated investigating the wrinkling behavior of these membranes. Wrinkling has an undesirable effect since wrinkles degrade the surface accuracy of structures incorporating thin membranes. This work introduces and evaluates an approach based on including optimized geometric features in thin membranes to suppress their wrinkling behavior. The ability of the optimized geometric features to suppress wrinkling in a 25 μm thick polyimide membrane subjected to uniaxial stretching is investigated computationally and experimentally in this work. A finite element model is developed to predict the wrinkling behavior of the membrane. An experimental setup equipped with 3D digital image correlation system is used to determine the wrinkles pattern, amplitude, and wavelength. Symmetric circular holes are introduced in the membrane to redistribute the stress field, eliminate the fluctuation in the minor principal stress in the membrane, and suppress wrinkles. The location and size of the circular holes are determined by coupling the Non-Linear Programming by Quadratic Largrangian technique and finite element simulations. An optimal design is obtained and the experimental results show that the optimally designed holes effectively suppressed the wrinkling behavior.

Impact of Air-Hole on the Optical Performances of Epitaxially Regrown P-Side Up Photonic Crystal Surface-Emitting Lasers

Optical performances of 950 nm p-side up photonic crystal surface emitting lasers (PCSELs) with different types of air holes are numerically and experimentally investigated. Simulation results show an obvious distinction between effective index method and three dimensional finite-element method (FEM). Measured experiments including wavelength, threshold, and slope efficiency can well meet the FEM numerical predictions. It further reveals that the B mode dominates the laser action and the PCSELs accompanying with equilateral triangle and right isosceles triangle holes possess a lower threshold current and higher radiation than symmetric circle holes. The output power can be further enhanced by increasing the filling factor of air holes before the regrowth process.

Photon-trapping array for enhanced midwave infrared photoresponse

Photonic structures have been attracting great attention as they have the ability to manipulate the photoresponse. Here, we report a hole array for effective photon trapping, therefore facilitating optoelectrical conversion of a midwave infrared photodetector. The integrated device consists of an InAsSb-based heterojunction photodiode and an embedded symmetric hole array penetrating through the top wide bandgap layers into the absorption region, which enables lower dark current, better broadband absorption, and improved polarization-independent photoresponse. The photoresponse enhancements of 26%–170% are achieved in the 2–5 µm range under zero power supply at temperatures from 293 K to 78 K. Combined with the effect of slightly decreasing in bulk dark current density, the zero-bias detectivity is increased by 29% at room temperature without sacrificing the response speed, where the enhanced detectivity increases to 2.09 × 109 Jones. This proposed approach provides a new strategy to boost optoelectrical conversion of photodetectors, thereby facilitating robust photodetection for widespread applications.

Shadow cast by a rotating and nonlinear magnetic-charged black hole in perfect fluid dark matter

In this paper, we derived an exact solution of the spherically symmetric Hayward black hole surrounded by perfect fluid dark matter (PFDM). By applying the Newman–Janis algorithm, we generalized it to the corresponding rotating black hole. Then, we studied the shadows of rotating Hayward black hole in PFDM. The apparent shape of the shadow depends upon the black hole spin [Formula: see text], the magnetic charge [Formula: see text] and the PFDM intensity parameter [Formula: see text]. The shadow is a perfect circle in the non-rotating case [Formula: see text] and a deformed one in the rotating case [Formula: see text]. For a fixed value of [Formula: see text], the size of the shadow increases with the increasing [Formula: see text], but decreases with the increasing [Formula: see text]. We further investigated the black hole emission rate. We found that the emission rate decreases with the increasing [Formula: see text] (or [Formula: see text]) and the peak of the emission shifts to lower frequency. Finally, we discussed the observational prospects corresponding to the supermassive black hole Sgr A[Formula: see text] at the center of the Milky Way.

ИССЛЕДОВАНИЕ МОДЕЛИ КРОТОВОЙ НОРЫ ШВАРЦШИЛЬДА-ДАМУРА-СОЛОДУХИНА

The equations of general relativity are nonlinear second-order partial differential equations, and, as a consequence, obtaining the exact solutions is a difficult problem. One of the solutions to this problem is to obtain models with a thin self-gravitating shell. This method is used to study most of the phenomena in the theory of gravity, where the reverse effect of matter on the geometry of space-time is a key factor. Another interesting problem that can be studied using the thin shell method is the «simulation» of a black hole. Consider a system consisting of a spherically symmetric Schwarzschild black hole and a thin shell surrounding it, located at a certain fixed distance from the black hole. From the viewpoint of gravitational physics, an observer at infinity is unable to distinguish a real black hole from a wormhole with a thin shell, in which the simulation condition is satisfied. Simulation of a black hole is possible only under sufficiently stringent conditions for the parameters of the model. In particular, the shell needs to be held at a fixed radius. In the general case, such a movement of the shell is non-geodesic, and external forces are required to hold it. The radius of the shell is also a parameter that determines the possibility / impossibility of simulation. In this paper, the radius is found for the case of a Schwarzschild black hole. In particular, the paper considers a model of a wormhole obtained as a result of gluing two space-times: a Schwarzschild black hole and a Damour-Solodukhin wormhole. The latter solution differs from the Schwarzschild black hole in the parameter of the dimensionless real deviation λ and is a twice asymptotically flat regular space-time. It is shown that they can be glued along a given radius. As a result, a thin shell is formed between two glued manifolds consisting of exotic matter. Cases are considered when the thin shell is stable. It turns out that zones corresponding to the «force» constraint are more restrictive than those corresponding to the «mass» constraint.

Optimization of the hole exit shape of the vortex generator jets in a compressor cascade

Vortex generator jets usually use a circular hole. The hole exit shape is also an important parameter, so the change of the shape will have a significant influence on the control effect of the compressor. In this article, the optimization design of the hole exit shape is studied in order to find the optimal geometry. The 2D hole exit shape is represented with a binary coded and initialized with the B-spline. The surrogate-based optimizer consists of a parametric design code, a computational fluid dynamics solver, a Kriging model, an infill sample criterion, and a genetic algorithm. First, the design of the symmetric hole is studied in a low ratio of the jet to inlet mass flow. The circumferential length of the designed hole is fixed. Second, both the symmetric hole and the asymmetric hole are studied. And the area of the hole exit shape is fixed. The results show that the optimal hole shape can enhance the strength of the jet vortex and reduce the total pressure loss of the compressor cascade. A better control effect can also be obtained in a high jet mass flow.

Plane strain tension fracture at high strain rate

Under plane stress conditions, most micromechanical and phenomenological models predict a minimum in ductility for plane strain tension stress state. Therefore, the stress state of plane strain tension plays a crucial role in many forming and crash applications and the reliable measurement of the strain to fracture for plane strain tension is particularly crucial when calibrating modern fracture initiation models. Recently, a new experimental technique has been proposed for measuring the strain to fracture for sheet metal after proportional loading under plane strain conditions. The basic configuration of the new setup includes a dihedral punch which applies out-of-plane loading onto a Nakazima-type of discshaped specimen with two symmetric holes and an outer diameter of 60 mm. In the present work, the applicability of the test is extended to high strain rates. High strain rates of about 100/s to 200/s are obtained using a drop weight tower device with an original sensor for load measurements. Quasi static tests are also performed for comparison, keeping the same specimen geometry, image recording parameters and set-up. The effective strains at fracture are compared from quasi-static to high strain rate loading for three different materials, i.e one aluminium alloy and two steels.

A Thermopile Device with Sub-Wavelength Hole Arrays by CMOS-MEMS Technology.

A thermopile device with sub-wavelength hole array (SHA) is numerically and experimentally investigated. The infrared absorbance (IRA) effect of SHAs in active area of the thermopile device is clearly analyzed by the finite-difference time-domain (FDTD) method. The prototypes are manufactured by the 0.35 μm 2P4M complementary metal-oxide-semiconductor micro-electro-mechanical-systems (CMOS-MEMS) process in Taiwan semiconductor manufacturing company (TSMC). The measurement results of those prototypes are similar to their simulation results. Based on the simulation technology, more sub-wavelength hole structural effects for IRA of such thermopile device are discussed. It is found from simulation results that the results of SHAs arranged in a hexagonal shape are significantly better than the results of SHAs arranged in a square and the infrared absorption efficiencies (IAEs) of specific asymmetric rectangle and elliptical hole structure arrays are higher than the relatively symmetric square and circular hole structure arrays. The overall best results are respectively up to 3.532 and 3.573 times higher than that without sub-wavelength structure at the target temperature of 60 °C when the minimum structure line width limit of the process is ignored. Obviously, the IRA can be enhanced when the SHAs are considered in active area of the thermopile device and the structural optimization of the SHAs is absolutely necessary.