Tiny Holes Research Articles

Fuzzy black hole models in f(G) Gravity

Abstract In this manuscript, we explore the concept of dark matter black holes, inspired by the Einasto density profile in the background of $f(\mathcal{G})$ gravity, where $\mathcal{G}$ is a Gauss-Bonnet invariant. This work extends the scope beyond the noncommutative tiny black hole structure which incorporates dark matter as a constituent forming the black hole. Our investigation demonstrates the feasibility of constructing black hole solutions for various Einasto index values, $f(\mathcal{G})$ gravity parameters, and parameters of mass function adopting anisotropic fluid configuration to characterize the matter sector. Specifically, by adopting an equation of state in which the radial pressure equals the negative of the energy density, we derive black hole solutions exhibiting a horizon structure with the central singularity replaced by a regular de Sitter core akin to the Reissner-Nordstr"{o}m black holes. Furthermore, we explore an alternative scenario where the equation of state is nonlocal, resulting in the construction of self-gravitating fuzzy dark matter droplets together with the dark source $f(\mathcal{G})$ corrections.

Effect of laser drilling process on combustor liner effusion hole quality

Abstract Effusion cooling is one of the significant cooling technologies in combustor liners in terms of cooling efficiency and weight reduction. However, effusion cooling technology is difficult to manufacture. In fact this technology requires laser-drilling of thousands of tiny holes with shallow angles on a sheet metal with a thickness generally varying between 0.5 to 1.5 mm. In addition, the use of thermal barrier coating is common in gas turbine engines and is one more challenge for the drilling process. In order to obtain more efficient gas turbine engines, the inlet temperature keeps increasing in the last decades, which induces the combustion chamber to operate in a hotter environment. Therefore, efficient cooling technology is needed, even if it is hard to manufacture. For laser drilling, several parameters have to be explored to obtain acceptable holes. This study includes the microstructure investigations of the holes produced with different laser parameters and the optimal laser parameters determined according to the microstructure of six different effusion cooling hole configurations. The results show that laser process differences affect the metal substrate microstructure and thermal barrier coating structure. Drilling method, peak power, number of pulses, gas type and pressure value have a significant effect on the hole geometry and its microstructure.

Ad hoc test functions for homogenization of compressible viscous fluid with application to the obstacle problem in dimension two

In this paper, we highlight a set of ad hoc test functions to study the homogenization of viscous compressible fluids in domains with very tiny holes. This set of functions allows to improve previous results in dimensions two and three. As an application, we show that the presence of a small obstacle does not influence the dynamics of a viscous compressible fluid in dimension two.

Tiny Security Hole: First-Order Vulnerability of Masked SEED and Its Countermeasure.

Side-channel analysis is a type of cryptanalysis that utilizes the physical leakage of a cryptographic device. An adversary exploits the relationship between a physical leakage and the secret intermediate value of an encryption algorithm. In order to prevent side-channel analysis, the masking method was proposed. Several masking methods of the ISO/IEC 18033-3 standard encryption algorithm SEED have been proposed, as the Korean financial IC (integrated circuit) card standard (CFIP.ST.FINIC-01-2021) mandates using a robust implementation of SEED as an encryption algorithm against side-channel analyses. However, vulnerabilities were reported, except for with only one masking method. This study proposes the first-order vulnerability of that masking method. That is, an adversary is able to perform a side-channel analysis with the same complexity as an unprotected implementation. In order to fix this vulnerability, we revise the masking method with negligible additional overhead. Its vulnerability and security are theoretically verified and experimentally demonstrated. The round key of the existing masking method is revealed with only 210 power consumption traces, while that of the proposed masking method is not disclosed with 10,000 traces.

Evaluating the Effectiveness of CHRIS'S Birds Assisted Therapy on Dental Anxiety among Pediatric Patients: A Pilot Study.

The heart of childhood nurtures an array of immature emotions. Through this rollercoaster of childhood emotions, from tears to laughter, it is the sole responsibility of a pediatric dentist to help the children navigate through their emotions with their empathetic actions. Whenever a child is anxious or fearful in the dental chair, the child may put forth his emotion through crying or taking up a flight response. Dental caries is a disease that is aggravated when a child refuses to cooperate with dental treatment. The tiny holes in the tooth, when unfilled, may lead to bigger problems, which in turn may lead to tooth loss in future. It is the comprehensive responsibility of the pediatric dentist to support health and emotional development and provide a complete, fulfilling oral rehabilitation to the child patient. The purpose of this study was to determine the anxiety levels of pediatric patients visiting the dental Outpatient Department at a Dental College and Hospital in Kavalkinaru. This study unveils a novel technique wherein birds were used in the form of CHRIS'S Birds Assisted Therapy to reduce anxiety in pediatric dental patients. Results showed that intervention with birds through CHRIS'S Birds Assisted Therapy significantly reduced the anxiety levels in children. Thus, CHRIS'S Birds Assisted Therapy is shown to be a promising method of anxiety control, a key to a successful pediatric dental practice. Joybell C, Kumar K. Evaluating the Effectiveness of CHRIS'S Birds Assisted Therapy on Dental Anxiety among Pediatric Patients: A Pilot Study. Int J Clin Pediatr Dent 2024;17(S-1):S84-S94.

Composite acoustic hole segmentation by semi-supervised learning for robotic multi-spindle drilling of aero-engine nacelle acoustic liners

The large-scale tiny acoustic holes densely distributed on acoustic liners are essential in aero-engine noise reduction. Accurate segmentation of those holes is fundamental for a robotic multi-spindle drilling system. This paper introduces a novel semi-supervised segmentation method for acoustic holes on composite acoustic liners. This method uses perturbation consistency loss to ensure output consistency while solving the problem of data volume imbalance. Afterward, a multi-reliability enhancement method and a pseudo-label reliability enhancement module are utilized to enhance the model’s robustness and accuracy. The segmentation experiments show that our method is superior to UniMatch and FixMatch. When using only 30% of labeled data, our method achieves an IoU of 96.39%, and the porosity differs only 0.038% from the ground truth, which is better than the fully-supervised segmentation method using all data. Our method can meet the accuracy and efficiency requirements of aero-engine nacelle production in China with only limited labeled data.

Inextensional vibrations of thin spherical shells using strain gradient elasticity theory

We study inextensional vibrations of the spherical shell using strain gradient elasticity theory under Kirchhoff-Love hypotheses. For admissibility of the inextensional deformations the shell is punctured by making a tiny hole. The shell is assumed to be made of linearly elastic, homogeneous, and isotropic material. The closed form expression for the frequencies of inextensional modes of vibration of spherical caps of various polar angles and that of nearly complete spherical shell are derived using Rayleigh's method. Towards this, the displacement and velocity fields are obtained by setting the membrane strains to zero. Further, to facilitate the existence of inextensional vibrations, boundaries are assumed to be traction free. The frequencies are computed for the positive and negative signs in the strain gradient term of the constitutive law. The computed frequencies, employing negative sign are found to be higher than those computed using classical elasticity theory. The opposite effect is seen when the frequencies are computed with the positive sign. Further, the frequencies are found to saturate when the positive sign is used in the constitutive law. Parametric studies viz. variation in frequencies with the circumferential wavenumbers for different values of length scale parameter, variation in frequencies with circumferential wavenumbers for different values of polar angles and a given length scale parameter, variation of frequency with increasing polar angle for a given circumferential wavenumber, variation of saturation wavenumber with increasing polar angle, and increasing length scale parameter are carried out. The frequencies of nearly a spherical shell with increasing circumferential wavenumber are also computed.

Low Mach number limit on perforated domains for the evolutionary Navier–Stokes–Fourier system

We consider the Navier–Stokes–Fourier system describing the motion of a compressible, viscous and heat-conducting fluid on a domain perforated by tiny holes. First, we identify a class of dissipative solutions to the Oberbeck–Boussinesq approximation as a low Mach number limit of the primitive system. Secondly, by proving the weak–strong uniqueness principle, we obtain strong convergence to the target system on the lifespan of the strong solution.

Study on Laser-Electrochemical Hybrid Polishing of Selective Laser Melted 316L Stainless Steel.

The process of forming metal components through selective laser melting (SLM) results in inherent spherical effects, powder adhesion, and step effects, which collectively lead to surface roughness in stainless steel, limiting its potential for high-end applications. This study utilizes a laser-electrochemical hybrid process to polish SLM-formed 316L stainless steel (SS) and examines the influence of process parameters such as laser power and scanning speed on surface roughness and micro-morphology. A comparative analysis of the surface roughness, microstructure, and wear resistance of SLM-formed 316L SS polished using laser, electrochemical, and laser-electrochemical hybrid processes is presented. The findings demonstrate that, compared to laser and electrochemical polishing alone, the laser-electrochemical hybrid polishing exhibits the most significant improvement in surface roughness and the highest material wear resistance. Additionally, the hybrid process results in a surface free of cracks and only a small number of tiny corrosion holes, making it more suitable for polishing the surface of 316L SS parts manufactured via SLM.

Investigating black hole accretion disks as potential polluter sources for the formation of enriched stars in globular clusters

Accretion disks surrounding stellar mass black holes have been suggested as potential locations for the nucleosynthesis of light elements, which are our primary observational discriminant of multiple stellar populations within globular clusters. The population of enriched stars in globular clusters are enhanced in N Na and sometimes in Al and/or in K . In this study, our aim is to investigate the feasibility of initiating nucleosynthesis for these four elements in black hole accretion disks, considering various internal parameters such as the temperature of the gas and timescale of the accretion. To achieve this, we employed a 132-species reaction network. We used the slim disk model, suitable for the Super-Eddington mass accretion rate and for geometrically and optically thick disks. We explored the conditions related to the mass, mass accretion rate, viscosity, and radius of the black hole-accretion disk system that would allow for the creation of N Na Al and K before the gas is accreted onto the central object. This happens when the nucleosynthesis timescale is shorter than the viscous timescale. Our findings reveal that there is no region in the parameter space where the formation of Na can occur and only a very limited region where the formation of N Al and K is plausible. Specifically, this occurs for black holes with masses lower than 10 solar masses ($m<10 M_ with a preference toward even lower mass values ($m<1 M_ and extremely low viscosity parameters ($ $). Such values are highly unlikely based on current observations of stellar mass black holes. However, such low mass black holes could actually exist in the early universe, as so-called primordial black holes. In conclusion, our study suggests that the nucleosynthesis within black hole accretion disks of elements of interest for the multiple stellar populations, namely N Na Al and K is improbable, but not impossible, using the slim disk model. Future gravitational wave missions will help constrain the existence of tiny and light black holes.

Deep-GD: Deep Learning based Automatic Garment Defect Detection and Type Classification

Garment defect detection has been successfully implemented in the quality quick response system for textile manufacturing automation. Defects in the production of textiles waste a lot of resources and reduce the quality of the finished goods. It is challenging to detect garment defects automatically because of the complexity of images and variety of patterns in textiles. This study presented a novel deep learning-based Garment defect detection framework named as Deep-GD model for sequentially identifying image defects in patterned garments and classify the defect types. Initially, the images are gathered from the HKBU database and bilateral filters are used in the pre-processing of images to remove distortions. A squeeze-and-excitation network (SE-net) combined with Random Decision Forest Classifier with Bayesian Optimization (RDF-BO) algorithm is used to detect and classify garment defects. By analyzing the differences among the original and reconstruction images, the unsupervised technique trains to rebuild the fabric pattern. The SE-net is used to identify certain fabric flaws in the garments of the pre-processed images. Then, the defects-related garments are processed using RDF-BO algorithm for classifying the garment defect from these regions. Finally, the proposed Deep-GD model is used for classifying defected fabric into 12 classes such as Defect free, soil stain, oil stain, Double end, Snarls, Miss, Horizontal stripes, Lumpy, Dye spot, Fall out, Hairiness, tiny hole. The proposed Deep-GD model achieves the overall classification accuracy of 97.16%, which is comparatively superior to the existing techniques.

Investigation of Microhole Quality of Nickel-Based Single Crystal Superalloy Processed by Ultrafast Laser

The geometric accuracy and surface quality of thin-film cooling holes have a significant impact on the cooling efficiency and fatigue life of aeroengine turbine blades. In this paper, we conducted experimental research on the processing of nickel-based single-crystal high-temperature alloy DD6 flat plates using different femtosecond laser processes. Our focus was on analyzing the effects of various laser parameters on the geometric accuracy results of microholes and the quality of the surfaces and inner walls of these holes. The results demonstrate that femtosecond laser processing has great influence on the geometrical accuracy and surface quality results of film cooling holes. Notably, the average laser power, focus position, and feed volume exert a significant influence on the geometric accuracy results of microholes. For instance, a higher laser power can damage the microhole wall, thereby leading to the formation of tiny holes and cracks. Additionally, microholes exhibit optimal roundness and taper values when using a zero defocus volume. Moreover, increasing the feed distance results in enhanced entrance and exit roundness, whereas scanning speed has a negligible impact on microhole roundness.

Compressive characterization of different chemically treated Borassus flabellifer fruit fibers

AbstractIn this current work, the Borassus flabellifer (BF) fruit fiber's surface has been modified using a variety of chemical processes in order to enhance the fiber properties. Investigations were done into the morphological, thermal, mechanical, and water absorption properties of BF fibers. Scanning electron microscopy (SEM) micrographs were used to visualize the effects of the surface alterations made to the BF fibers. These images demonstrate rough texture of the fiber surfaces with tiny holes and grooves as a result of the removal of lignin and hemicellulose from the fiber. To investigate the effects of surface changes on the fiber composition, Fourier transform infrared (FTIR) spectroscopy of BF fibers was performed. The enhancement in the crystallinity of the surface‐modified BF fibers is confirmed by the energy‐dispersive x‐ray (EDX) and x‐ray diffraction analyses. The thermogravimetric analysis demonstrates that the surface‐modified fibers exhibit increase in thermal stability as well as the tensile strength. The water absorption test confirms the reduction of the hydrophilic nature of the chemically treated BF fibers.Highlights Benzoyl chloride‐treated BF fiber have shown the best surface modification. Chemically treated BF fibers show better crystallinity, as per XRD, SEM and EDX. Benzolization of BF fiber, increases the hydrophobic nature of the fiber.

Novel 3D Printing Designs of Drywall Anchor

In this research project, the unique designs for 3D printed drywall anchors in this study were inspired by the skin of animals seen in nature, including reptiles, fish, and butterflies. The tough skin of these animals inspired our drywall anchor design. Engineered nylon produces drywall Anchors, one-piece, self-drilling drywall, and hollow cavity anchors. It may be installed in walls as thin as 12mm and optimized for drywall usage. You can screw with the nylon piece. A drywall sleeve anchor is an insert or sleeve made of plastic inserted into a tiny pilot hole. The sleeve enlarges as the drywall metal screw provided is threaded into it. This increases the shear strength, which helps the metal screw remain in the wall. Drywall sleeve anchors are often the sort of drywall anchor that has the lowest price point. They work well for lightweight products. The purpose of a drywall anchor is to firmly mount framed artwork, mirrors, clocks, and shelving to walls.

Do tiny black holes from cosmic dawn hide within giant stars?

Idea could account for universe’s mysterious dark matter

Molecular-level study of hydrophobic interactions during low-rank coal particle-bubble attachment

Particle-bubble attachment is a crucial part of coal and mineral flotation processes. The attachment of two different hydrophobic low-rank coal particles to bubble surface were simulated by a non-equilibrium molecular simulation method. Both particles were subjected to water film drainage resistance when approaching the bubble. Eventually, CPC (low-rank Coal Particle with mixed Collector adhered) jumped in and attached to bubble, but CP (low-rank Coal Particle) had only repulsive effect with bubble. The surface water film of CPC generated tiny hole under the entropy effect of water molecule rearrangement, and the presence of gas–water and oil–water interfacial tension promoted the rapid expansion of the hole until the water film rupture. The critical rupture thickness of the water film on CPC surface was about 1 nm and the rupture was completed in a very short time of 0.4 ns. The CPC jumped in and attached to the bubble surface under the action of oil–water interfacial tension. This suggests that the long-range hydrophobic force originates from the combined action of various interfacial tensions. Our results demonstrate the important role of interfacial tension in the attachment of hydrophobic particle to bubble, and contribute to the connection between microscopic and macroscopic mechanism of particle-bubble attachment.

Thermal decomposition of 1-ethyl-3-methylimidazolium acetate

To realize the potential applications of ionic liquids as working fluids and solvents one should have knowledge about their long-term stability, which depends on their thermally initiated decomposition. However, the possible decomposition pathways are not yet known accurately. 1-Ethyl-3-methylimidazolium acetate ([C2Mim][OAc]) is widely studied and shows potential in cellulose dissolution. In this study, we investigate possible [C2Mim][OAc] decomposition pathways by combining decomposition experiments and ab initio rate constant computations. Both approaches yield activation energies around 135 kJ·mol−1, which significantly deviate from earlier TGA measurements with open surface yielding 100–110 kJ·mol−1 and are probably affected by evaporation. Our study uses an improved TGA measurement protocol with a sealed pan with a tiny hole that fosters measurement of the actual chemical process leading to mass loss. Ab initio computations of this study comprise vapor-liquid equilibria of reactants and products as well as forward and reverse reaction rate constants in the gas and liquid phase. Calculations for the gas phase closely match a first-order analysis of the experiments, but calculations for the liquid phase strongly depend on the quality of solvation modeling. The computations indicate that the SN2 pathway with an activation energy of 142–144 kJ·mol−1 dominates thermal decomposition of [C2Mim][OAc].

Wide refractive index detection range sensors based on D-shape photonic crystal fiber with a nanoscale gold wire

Optical sensing based on photonic crystal fiber (PCF) is attracting interests. Currently, PCF sensing suffered from the insensitivity with the changes of environmental surroundings with low refractive index. A D-shape PCF supporting plasmonic resonances based on gold nanowires is designed to demonstrated the sensitivity optical sensing in the refractive index range from 1.00 to 1.30. The finite element method is performed to optimize the device parameters, including the diameter of the large and tiny air holes, the size of the gold nanowire, and the space between the air holes. Utilizing plasmon-induced confined electrical around gold nanowires, the predicted device performance in spectral and amplitude sensitivities are up to 19,400 nm/RIU and 5.15 × 10−6 RIU, respectively. It is believed that the designed sensor can promote the development of applications in biological and pharmaceutical.

Experimental study on the breakdown mechanism of high temperature granite induced by liquid nitrogen fracturing: An implication to geothermal reservoirs

To reveal the breakdown mechanism of dry hot rock (HDR) induced by liquid nitrogen (LN) fracturing, the laboratory tests were performed on high temperature granite using specialized apparatus. The breakdown pressure and fracture morphology of high temperature granites subjected to different heating temperatures and thermal treatments were analyzed. The results showed that the breakdown pressure of granite decreased with heating temperature increasing. As the heating temperature increased from 25 °C to 300 °C, the breakdown pressure of high temperature granite decreased by 40.63%. In addition, the failure mode mainly presented in the form of tensile fractures, which developed into bi-wing fractures along the hole axis. For heating temperature higher than 220 °C, the high temperature granite presented an increase in fracture complexity with the increased heating temperature. After pre-cooled with LN, the breakdown pressure was lowered and the fracture complexity was enhanced. For example, the breakdown pressure of LN-treated sample was 4.61%–27.70% lower than heated sample. Under cryogenic conditions induced by LN, the failure mode mainly presented in the form of randomly distributed tiny cracks and holes, which made the breakdown pressure decreased by 8.67%–59.46%. LN fracturing could cause multiple cracking effects including thermal fracturing (i.e., thermal shock, cryogenic damage and cryogenic cracking) and pressure-induced fracturing on HDR. Importantly, the thermal fracturing effect could reduce the breakdown pressure and improve the fracture complexity.

Gravitational wave hints black hole remnants as dark matter

The end state of Hawking evaporation of a black hole is uncertain. Some candidate quantum gravity theories, such as loop quantum gravity and asymptotic safe gravity, hint towards Planck sized remnants. If so, the Universe might be filled with remnants of tiny primordial black holes, which formed with mass g. A unique scenario is the case of g, where tiny primordial black holes reheat the Universe by Hawking evaporation and their remnants dominate the dark matter (DM). Here, we point out that this scenario leads to a cosmological gravitational wave signal at frequencies ∼100 Hz. Finding such a particular gravitational wave signature with, e.g. the Einstein telescope, would suggest black hole remnants as DM.