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We formulate an optimization problem for the dependence of the eigenvalues of Maxwell's equations in a cavity with perfect electric conducting boundary upon variation of the electric permittivity, and we prove a corresponding Maximum Principle. [ABSTRACT FROM AUTHOR]

This study investigates turbine rim seal geometry effects within the rotationally-driven ingestion regime. Computations were performed with a wall-resolved unsteady Reynolds-averaged Navier-Stokes (URANS) model and a large-eddy simulation (LES) model including near-wall boundary layer modeling, that is, wall-modeled LES (WMLES). Use of simplified rim sealing models is proposed as an efficient method of ranking seal designs and investigating sensitivity to seal geometry. Four rim seal configurations, two chute seals, an axial seal and a radial seal which are representative of those used in gas turbines and in previous research were investigated. Furthermore, hybrid seals combining geometric characteristics from both the chute and radial seal were considered. Significant sensitivities of sealing performance to turbulence modeling are identified, but URANS and WMLES show similar trends in ranking of seal performance, and these are consistent with previous experimental work. The addition of an outer radial clearance section to a chute seal is effective in reducing ingestion levels. [ABSTRACT FROM AUTHOR]

In Part I, a companion paper of the two-part article, a subsonic turbine stage and a transonic one conditioned at the same Reynolds number, flow coefficient, loading coefficient and reaction, but two different exit Mach numbers are designed to provide a direct contrast between a high-subsonic and a transonic flow conditioning for rotor blade squealer tips. In this paper as Part II, further analyses are carried out to address the main issues of interest arising from Part I: first, to identify the driving flow physical mechanisms for the contrasting aerodynamic efficiency sensitivities of the two stages; second to seek a more suitable heat transfer objective function for the tip aerothermal design optimization, given the seemingly strong conflicts among those conventionally adopted heat transfer objective functions. Two counter-rotating tip vortical structures, the pressure side vortex (PSV) and the casing-driven cavity vortex (CCV), are shown to impact the aero-performance differently between the two stages. For the subsonic stage, the leakage flow is strongly affected by a stronger residual PSV at the squealer cavity exit. For the transonic stage however, the tip choking in limiting the over tip leakage (OTL) mass flow and favorable pressure gradient in a transonic flow over a separation bubble led to a much stronger and more persistent CCV and thus lower aero-effectiveness of squealer tip for the transonic stage. The two vortices also show major heat transfer signatures on the cavity surfaces by impingement. For the PSV, the impingement impact is mainly on the cavity floor. For the CCV, on the other hand, its impact is mainly on the inner side-wall of the suction side rim. The latter is found to be mainly responsible for the overall linear variations of the heat load with the squealer height. Again, the relative strength between PSV and CCV serves as an effective differentiator in the heat transfer performance. The stronger and more persistent CCV in the transonic stage results in a strong signature on a large portion of the suction side cavity inner sidewall, thus a much higher increment in heat transfer with the squealer height than that for the subsonic stage. In seeking to establish a more consistent heat transfer objective function for combined aerothermal design and optimization, a coolability weighted nonuniformity parameter is proposed to integrate the local heat transfer and the coolability. The proposed objective function is shown to lead to consistent Pareto fronts for the combined aerothermal performance sensitivities, particularly for the present cases with strong heat transfer nonuniformity which are particularly challenging to those conventional treatments as shown in Part I. The coolability-augmented objective function should thus serve as an enabler to help practical applications of blade tip aerothermal design optimizations. [ABSTRACT FROM AUTHOR]

"Double-loop" theory was determined by deriving a correlation between turbulent fluctuating kinetic energy and water vapor volume fraction from the momentum equation, which further logically revealed the mystery of cavitation breaking around a three-dimensional symmetry hydrofoil based on the numerical results of large eddy simulation and Zwart-Gerber-Belamri cavitation model. When the second-order fluctuation moment V'xV'x and the streamwise velocity Vx are depleted, a vortex is generated, leading to alternating cavitation interface fluctuations. In one state, cavitation naturally breaks outward from the inner zone, triggering an up-and-down fluctuation in the normal velocity in the gap vortex and transferring external energy to the inner zone. In another state, cavitation collapse caused by a reentrant jet stagnates the reverse Vx so that V'xV'x tends to zero. It triggers a rise in an upward normal velocity in the attached vortex, creating an exchange of energy through the wake. The pressure implosion resulting from the Shrinkage of the "Like-Rayleigh-Plesset" cavity at the cavitation onset is stronger than the pressure implosion created by the vortex field during cavitation breaking. [ABSTRACT FROM AUTHOR]

This work presents a pioneering photonic crystal (PC) heterostructure design exploiting tailored topological corner states and cavities to unleash a fascinating topological rainbow effect. This effect arises from the strategic integration of a nontrivial topological PC with sharp corners within a trivial PC matrix, resulting in a heterostructure rich in corner states and cavities. The critical innovation lies in manipulating the sector angle of circular columns, granting dynamic control over the rainbow effect and light localization. This manipulation induces distinct group velocities for different light frequencies, leading to their separation and localization at specific corner states. This remarkable "rainbow trapping" phenomenon manifests as highly confined light exhibiting exceptional resilience against disorder. These findings illuminate a pathway toward crafting next‐generation photonic devices boasting unparalleled functionalities. The reconfigurable rainbow trapping holds immense potential for applications in wavelength division multiplexing, optical sensing, and even venturing into quantum information processing. [ABSTRACT FROM AUTHOR]

Abstract The effectiveness of ground penetrating radar (GPR) in identifying and categorizing diseases that occur underground beneath the surfaces of urban roads is investigated in this study. Both 2D and 3D forward modeling use simulation with the GprMax program to show the response characteristics of common cavity illnesses, which facilitates interpretation in practical situations. The cavity morphology classification accuracy is improved to 90.5% by using convolutional neural networks (CNNs), specifically transfer learning with AlexNet. This method outperforms existing approaches even with minimal data. Four primary types are identified from an analysis of 1965 subsurface cavity data: hollow bodies, empty bodies, loose bodies, and water-rich bodies. These categories are important for evaluating road risks such as voids and subsidence. However, it is still difficult to interpret picture features linked to cavity diseases accurately because of a variety of elements, such as anthropogenic, environmental, and geological influences. However, the accurate interpretation and recognition of image features related to cavity diseases remain challenging. Moreover, there are various factors involved in the formation of underground diseases and cavities, including geological and environmental factors, physical and chemical properties of the geotechnical materials, anthropogenic engineering activity and social population or commercial effects.

An inducer is a key component in a cryogenic pump to improve its cavitation performance. The thermodynamic effects of the cryogenic medium make the cryogenic cavitation flow extremely complicated. For this reason, it is crucial to investigate the cryogenic cavitation flow of the inducer which is equipped upstream of the cryogenic pump. In this paper, the isothermal cavitation model is modified based on the law of heat conduction, and the cryogenic cavitation model of the inducer is developed by considering thermodynamic effects. The turbulence model is also modified to account for the compressibility of cryogenic cavitation flow. The methods of numerical calculations are performed to investigate the influence of thermodynamic effects on cryogenic cavitation of the inducer. The law of the spatio-temporal evolution of cryogen cavitation in the inducer is clarified. The initial position, development and collapse phenomenon of cavitation are obtained. The relationship between the generation and collapse of the cavitation and the work capacity of the inducer's blade, the relationship between thermodynamic effects and the influence of the inducer's blade tip leakage vortex and thermodynamic on cryogenic cavitation of the inducer are revealed. [ABSTRACT FROM AUTHOR]

This study is conducted within the Gambia River Basin Development Organization Energy Project (OMVG) framework. The construction of a high voltage interconnection network fed by a hydropower station to supply electricity to OMVG Member States was done on stable ground. During the installation pits for the pylons in Labé Prefecture, Republic of Guinea, cavities were discovered in the geological formations during the initial planned route. Structurally, the study area is bounded by two major faults to the east and west of northeast direction. The geomorphology is made up of a central plateau, intermountain depressions, piedmont plains, talwegs, and glacis. Geological investigations were obtained by a geophysical Two-dimensional Electrical Resistivity Tomography (ERT) method. The results show that the synthetic lithological profile from top to base was sandy-clayey soil, hard cuirass, and a layer of gravel followed by a mottled zone comprising an indurated part and an imbibed part just before the source rock. The cavities were observed probably because of the dissolution of certain minerals constituting the weathering crust due to the infiltration, underground waters, and the seasonal variation in the level of the surface watercourses. Geophysical results showed a very good agreement with the visual observations. [ABSTRACT FROM AUTHOR]

In this work, we build upon our previous finding that hydrodynamic porosity is an exponential function of pore-scale flow velocity (or interstitial Reynolds number). We previously discovered this relationship for media with a square cavity geometry—a highly idealized case of the dead-ended pore spaces in a porous medium. Thus, we demonstrate the applicability of this relationship to media with other cavity geometries. We do so by applying our previous analysis to rectangular and non-rectangular cavity geometries (i.e., circular, and triangular). We also study periodic flow geometries to determine the effect of upstream cavities on those downstream. We show that not only does our exponential relationship hold for media with a variety of cavity geometries, but it does so almost perfectly with a coefficient of determination (R2) of approximately one for each new set of simulation data. Given this high fit quality, it is evident that the exponential relationship we previously discovered is applicable to most, if not all, unwashed media. [ABSTRACT FROM AUTHOR]

Dental caries occurs from the interaction between oral bacteria and sugars, generating acids that damage teeth over time. The importance of X-ray images for detecting oral problems is undeniable in dentistry. With technological advances, it is feasible to identify these lesions using techniques such as deep learning, machine learning, and image processing. Therefore, the survey and systematization of these methods are essential to determining the main computational approaches for identifying caries in X-ray images. In this systematic review, we investigated the primary computational methods used for classifying, detecting, and segmenting caries in X-ray images. Following the PRISMA methodology, we selected relevant studies and analyzed their methods, strengths, limitations, imaging modalities, evaluation metrics, datasets, and classification techniques. The review encompassed 42 studies retrieved from the Science Direct, IEEExplore, ACM Digital, and PubMed databases from the Computer Science and Health areas. The results indicate that 12% of the included articles utilized public datasets, with deep learning being the predominant approach, accounting for 69% of the studies. The majority of these studies (76%) focused on classifying dental caries, either in binary or multiclass classification. Panoramic imaging was the most commonly used radiographic modality, representing 29% of the cases studied. Overall, our systematic review provides a comprehensive overview of the computational methods employed in identifying caries in radiographic images and highlights trends, patterns, and challenges in this research field. [ABSTRACT FROM AUTHOR]

The Schrödinger equation for the hydrogen atom enclosed by an impenetrable spherical cavity is solved through a Finite‐Differences approach to gain an insight on the actual nature and structure of the ansatz wavefunction cutoff factor widely used in an ad hoc manner in corresponding variational calculations to comply with the Dirichlet boundary conditions. The results of this work provide a theoretical foundation for the choice of the appropriate analytical cutoff functions that fulfill the boundary conditions. We find three different regions for the behavior of the cutoff functions. Small cavity radius where the cutoff function has a parabolic behavior, an intermediate region where the cutoff function is quasi‐linear, and a large cavity region where the cutoff function is a step‐like function. We deduce the traditional linear and quadratic cutoff functions used in the literature as well as its validity region for the confining radius. Finally, we provide a mathematical deduction of the exact cutoff function in terms of the nodal structure of the free hydrogenic wavefunctions and a relation to the Laguerre polynomials for some cavity radii where the free atomic energy level coincides with a confined energy level. We find that the cutoff function transit over several unconfined solutions in terms of its nodal structure as the system is compressed. [ABSTRACT FROM AUTHOR]

The concept behind this article is an extensive analysis of the most recent findings about free convection thermal flow in an enclosure or cavity, as well as the methods employed to enhance heat transfer (HT). There are different heat transfer enhancers such as (a) nanofluids, (b) porous media, (c) large particle suspensions, (d) phase-change devices, (e) flexible seals, (g) fins and microfins, and (h) ultra high thermal conductivity composite materials. The majority of heat transfer enhancement techniques that use porous media, fins, and nanofluids are reviewed in the literature. In this review, both experiments and theoretical studies on different cavities are highlighted through investigating the subsequent parameters: impacts of the configuration of the cavities, effect of the type of nanoparticles, significance of cavities in nanofluids, effects of the cavities' tilt angle, wave amplitude, the magnetic field's (MF) influence in cavities, and cooler and heater impacts. Through a review of the literature, it was found that the use of nanofluid in all forms of cavities increases its thermal performance. The most used cavity is square, which has many applications. The results obtained from previous studies can be used to improve the design and heat refinement of the geometry applied in diverse energy systems. Additionally, as the Hartmann number rises, there is a rising tendency observed in the average Nusselt number. Furthermore, as the concentration of nanofluid particles and Rayleigh numbers rise, so does the rate of heat transfer. The heat transfer within the cavity is improved by the hybrid nanoparticles. The amount of the augmentation would, however, decrease as the concentration of nanoparticles increased. The lowest volume fraction of nanoparticles, Ø = 0.2 vol.%, showed the greatest increase. Also, the inner wave affects the flow pattern when the wave amplitude rises but the flow strength stays constant. The most important findings showed that the heterogeneous porous medium transfers heat more effectively than the homogeneous porous medium in different enclosures. [ABSTRACT FROM AUTHOR]

Abstract Background Protein–protein interactions (PPIs) are conveyed through binding interfaces or surface patches on proteins that become buried upon binding. Structural and biophysical analysis of many protein–protein interfaces revealed certain unique features of these surfaces that determine the energetics of interactions and play a critical role in protein evolution. One of the significant aspects of binding interfaces is the presence of binding hot spots, where mutations are highly deleterious for binding. Conversely, binding cold spots are positions occupied by suboptimal amino acids and several mutations in such positions could lead to affinity enhancement. While there are many software programs for identification of hot spot positions, there is currently a lack of software for cold spot detection. Results In this paper, we present Cold Spot SCANNER, a Colab Notebook, which scans a PPI binding interface and identifies cold spots resulting from cavities, unfavorable charge-charge, and unfavorable charge-hydrophobic interactions. The software offers a Py3DMOL-based interface that allows users to visualize cold spots in the context of the protein structure and generates a zip file containing the results for easy download. Conclusions Cold spot identification is of great importance to protein engineering studies and provides a useful insight into protein evolution. Cold Spot SCANNER is open to all users without login requirements and can be accessible at: https://colab.research.google.com/github/sagagugit/Cold-Spot-Scanner/blob/main/Cold_Spot_Scanner.ipynb .

It has been confirmed that the passive obstacles would substantially depress the leading-edge cavitation in a waterjet pump. Combined with the experiments and numerical simulations, this work revisits blade cavitation evolutions to demonstrate the stabilizing effects of obstacles on cavitation unsteadiness. The multiscale proper orthogonal decomposition (mPOD) and ensemble empirical mode decomposition (EEMD) are adopted to study the energy contributions regarding the cavitation-induced loading and thrust. The mPOD modes illuminate that the leading-edge loading oscillations of the obstacle blade are consequently eliminated where the cavitation is completely depressed and the obstacle cavitation wakes greatly contribute to loading excitation. The thrust statistics demonstrate that the thrust extremes and standard deviation in some revolutions can be well reduced as the large-scale leading-edge cavity depression. The adaptive spectra obtained by EEMD further illuminate that both the tonal and broadband components of blade thrust would be reasonably degraded to some degree. The pump with only one obstacle implementation, as an improvement strategy, is comparatively studied and indicates that single obstacle configuration presents positive effects on the leading-edge cavity depression owing to the pressure-raising effects and can reduce the un-necessary energy loss compared with two obstacles. [ABSTRACT FROM AUTHOR]

Ferroelectric thin films hold significant promise in various nanoelectronic applications, demanding precise control over their domain structures. While electrical field‐driven polarization switching is currently employed, it often leads to undesirable side effects. In contrast, mechanical switching offers a voltage‐free alternative but faces challenges in thicker films. Recent breakthroughs have demonstrated stable mechanical switching in films up to 200 nm thick, attributed to the presence of nanocavities. These nanoscale voids are believed to facilitate domain transitions, serving as essential pinning centers. In this study, mechanical domain switching in thick ferroelectric films is investigated using phase‐field modeling, with a specific focus on evaluating the influence of nanocavities on domain stability. The effects of cavity parameters (size, depth, and dielectric properties) on mechanical switching stability under various applied pressures are systematically examined. The findings reveal the intricate interplay between these factors and outline the conditions for stable mechanical switching. Furthermore, phase‐field simulations are employed to showcase the energetic mechanisms governing nanocavity‐assisted mechanical switching, while also highlighting the pivotal role of these defects as pinning centers. This investigation elucidates the nanocavity‐assisted mechanical control of polarization and the potential for optimizing thin film design through nanocavity engineering, thus enabling mechanical switching across substantial film thicknesses. [ABSTRACT FROM AUTHOR]

Background: Protein–protein interactions (PPIs) are conveyed through binding interfaces or surface patches on proteins that become buried upon binding. Structural and biophysical analysis of many protein–protein interfaces revealed certain unique features of these surfaces that determine the energetics of interactions and play a critical role in protein evolution. One of the significant aspects of binding interfaces is the presence of binding hot spots, where mutations are highly deleterious for binding. Conversely, binding cold spots are positions occupied by suboptimal amino acids and several mutations in such positions could lead to affinity enhancement. While there are many software programs for identification of hot spot positions, there is currently a lack of software for cold spot detection. Results: In this paper, we present Cold Spot SCANNER, a Colab Notebook, which scans a PPI binding interface and identifies cold spots resulting from cavities, unfavorable charge-charge, and unfavorable charge-hydrophobic interactions. The software offers a Py3DMOL-based interface that allows users to visualize cold spots in the context of the protein structure and generates a zip file containing the results for easy download. Conclusions: Cold spot identification is of great importance to protein engineering studies and provides a useful insight into protein evolution. Cold Spot SCANNER is open to all users without login requirements and can be accessible at: https://colab.research.google.com/github/sagagugit/Cold-Spot-Scanner/blob/main/Cold_Spot_Scanner.ipynb. [ABSTRACT FROM AUTHOR]

The flow structures and heat transfer within rotating cavities of aero-engine axial compressors influence the thermal expansion of the rotor disks, and consequently the blade-tip clearances. To investigate the flow field at the bore and lower cavity region, experimental measurements have been acquired in an engine-representative test facility. Axial, tangential, and radial velocities were measured using a miniature five-hole probe at a range of axial and radial positions. Time-averaged results from 28 tests carried out at nondimensional parameters comparable to engine conditions: 1.3 × 104 ≤ Rez ≤ 8.2 × 104, 3.0 × 105 ≤ Reθ ≤ 3.2 × 106, 0.11 ≤ Ro ≤ 3.24, 0.14 ≤ βΔT ≤ 0.36 are presented in this paper. The axial and tangential velocity measurements conform to previous work, while the radial velocity component provides quantitative evidence of an asymmetric toroidal vortex in the cavity gap, biased toward the downstream disk. The vortex is characterized by the local vorticity and grows in strength and size as Rossby number increases above Ro = 0.34 to 1.63. The effect of βΔT on the vortex formation is negligible compared to the influence of the tangential Reynolds number as the local circulation is suppressed by the Coriolis forces at high rotational speeds. Both the tangential and radial velocity results suggest that as Ro is increased, the proportion of air that is radially ingested and expelled from a cavity decreases. [ABSTRACT FROM AUTHOR]

Styryl dyes are generally poor fluorescent molecules inherited from their flexible molecular structures. However, their emissive properties can be boosted by restricting their molecular motions. A tight confinement into inorganic molecular sieves is a good strategy to yield highly fluorescent hybrid systems. In this work, we compare the confinement effect of two Mg-aluminophosphate zeotypes with distinct pore systems (the AEL framework, a one-dimensional channeled structure with elliptical pores of 6.5 Å × 4.0 Å, and the CHA framework, composed of large cavities of 6.7 Å × 10.0 Å connected by eight-ring narrower windows) for the encapsulation of 4-DASPI styryl dye (trans-4-[4-(Dimethylamino)styryl]-1-methylpyridinium iodide). The resultant hybrid systems display significantly improved photophysical features compared to 4-DASPI in solution as a result of tight confinement in both host inorganic frameworks. Molecular simulations reveal a tighter confinement of 4-DASPI in the elliptical channels of AEL, explaining its excellent photophysical properties. On the other hand, a singular arrangement of 4-DASPI dye is found when confined within the cavity-based CHA framework, where the 4-DASPI molecule spans along two adjacent cavities, with each aromatic ring sitting on these adjacent cavities and the polymethine chain residing within the narrower eight-ring window. However, despite the singularity of this host–guest arrangement, it provides less tight confinement for 4-DASPI than AEL, resulting in a slightly lower quantum yield. [ABSTRACT FROM AUTHOR]

Subsea centrifugal compressors commonly using labyrinth seals (LS) and pocket damper seals (PDS) must withstand the flow of oil in gas mixtures with a liquid volume fraction (LVF) up to 5%. This paper presents experimental results for the leakage and rotordynamic coefficients of a uniform clearance PDS and a similar size LS both supplied with wet gas. The shaft diameter D = 127 mm and the seal axial length L = 48 mm. In the tests, the seals' pressure ratio (inlet/exit) = 2.5, and the shaft speed reaches 5.25 krpm (surface speed = 35 m/s). The LS has a 17% larger radial clearance (Cr, LS = 0.230 mm > Cr, PDS = 0.196 mm) due to a manufacturing error. This paper extends prior work by Torres et al. (2022, "A Stepped Shaft Labyrinth Seal versus a Pocket Damper Seal: Leakage and Dynamic Force Coefficients Under Wet Gas Operation," ASME J. Eng. Gas Turbines Power, 145(1), p. 011006) for the same two seal types with a stepped clearance configuration that promotes damping. When supplied with a dry gas, the LS leaks more because of its larger clearance. A loss coefficient (cd) is a fraction of the physical clearance that characterizes a seal's effectiveness in reducing leakage. The cd of both seals is nearly identical for operation with pure gas; the small differences are well within the experimental uncertainty. For operation with wet gas, the PDS cd decreases as the LVF increases whereas the LS cd increases, thus indicating the PDS is more effective to restrict wet gas leakage. When operating with pure gas, the direct stiffness (K) and effective damping (Ceff) of both seals are small in magnitude (K < 0.5 MN/m, Ceff < 2 kN-s/m) and often less than the experimental uncertainty. For wet gas operation and with shaft speed = 3 krpm and 5.25 krpm, the PDS produces Ceff < 0 for whirl frequencies below 50 Hz. In contrast, the LS Ceff > 0, although small in magnitude. The experimental results under wet gas operation are similar for operation with LVF equal to 3% and 5%. Unexpected low-frequency broadband motions appear when supplying the PDS with a wet gas. Although small in amplitude (<5 µm), the motions increase in severity as the mixture inlet LVF and shaft speed increase. The motions are entirely absent for tests with the LS. Experiments in which the mixture is drawn from the PDS cavities rule out liquid accumulation as the cause of the observed motions. The current test results serve as a reference for turbomachinery design engineers and aid in the validation of analytical predictive tools. [ABSTRACT FROM AUTHOR]

Objective: To assess the correlation between patients with type 1 diabetes mellitus (T1DM) and dental caries outcomes, including missing teeth, missing surface, filling teeth, filling surface, plaque index, gingival index, and calculus index. Methods: A comprehensive search was performed across EMBASE, Medline/Pubmed, and Web of Science databases from inception until February 20, 2023. Observational and interventional studies reporting dental caries outcomes in patients with T1DM were included. A random effects meta-analysis was performed to estimate the pooled effect sizes and 95 % confidence intervals. Results: Thirty-three studies met the criteria for inclusion in the meta-analysis, which revealed that patients with T1DM had a reduced risk of missing teeth in comparison to those without diabetes (control group), with a mean difference (MD) of -0.03, CI 95 % [-0.03, -0.03]. No significant differences were found in missing surface, filling teeth, filling surface, or calculus index between T1DM and non-diabetic groups. However, patients with T1DM had a significantly higher plaque index (MD: 0.47, CI 95 % [0.06, 0.89]) than the non-diabetic group. The overall MD in DFMT between the DM and non-DM groups was 0.47 (95 % CI: 0.13, 0.82). The gingival index showed no significant difference between the groups. Conclusion: This meta-analysis suggests that patients with T1DM have a higher plaque index than the non-diabetic group, whereas no significant differences were observed in other dental caries outcomes. Because of the considerable variability identified in certain analyses, additional research employing more extensive sample sizes and rigorous methodologies is required to validate these results.

The present study analyzes on the reviews carried out by the previous researchers on the entropy generation caused by the flow and heat transfer of several composite nanofluids subject to varieties of geometries under the influence of several constraints of motions. The composite nanofluids include binary hybrid nanofluids and ternary hybrid nanofluids involving disparate base fluids with different suitable nanoparticles. The geometries considered are deformed surfaces (stretched/shrunk sheets, cylinders, and disks), channels and cavities. Several numerical techniques such as Runge-Kutta method and finite element/difference/volume methods are implemented in the investigations. The major and significant outcome of the review analysis is the entropy comparison for different types of nanofluids. Growth of the volume percentage of nanoparticles at a fixed mass flow rate enhances entropy formation. When porosity strength increases, the irreversible entropy production caused by fluid friction results in increased thermal efficiency of certain systems than magnetic entropies. Compared to single nanofluids, hybrid nanofluids display the maximum entropy. With increasing Rayleigh numbers, the frictional and magnetic entropies in composite nanofluids ameliorate significantly than thermal entropy.

The non-Drude-like behavior of the real part of the photoinduced permittivity Re εP of GaAs and Si samples in the gigahertz range is detected by direct cavity measurements under conditions of fiber-optic irradiation at a wavelength of λ = 0.97 microns with changing power P in the range of 0–1 W. It is shown that, in accordance with the hypothesis of the exciton mechanism of photoinduced microwave dielectric permittivity, Re εP increases with increasing P (approaching saturation above P = 200 mW) instead of decreasing within the framework of free-charge carriers according to Drude. The generality of the behavior of the real parts of the photoinduced permittivity observed in semiconductors of different types (direct-gap GaAs and indirect-gap Si) in different electrodynamic systems (waveguides, cavities, metastructures) testifying to the universality of the exciton mechanism is demonstrated. Optically controlled metastructures in the GHz band containing resonant electrically conductive elements filled with GaAs and Si samples are proposed for the first time: a metastructure based on linear dipoles and a half-wave electric dipole based on a multipass spiral. The gigahertz responses of the metastructures and transformation of the responses associated with changes in the dielectric permittivity of Si and GaAs during photoexcitation are measured for the first time. Based on the hypothesis put forward about the effect of excitons on photoexcitation, the observed saturation effect of gigahertz photoinduced permittivity is discussed. [ABSTRACT FROM AUTHOR]

The results of the study of the effect of low concentration of anti-corrosion additives in the coolant on corrosion, scaling and pitting of cooling jackets of the cylinder block of the internal combustion engines of the gas-diesel mining dump trucks are presented. The negative influence of the presence of coolant in the engine oil system has been studied. It is argued that even an insignificant concentration of coolant in the engine oil leads to cavitation with the concomitant occurrence of caverns or significant and deep pits—pockmarks—on especially stressed parts of the engine (crank-connecting rod liners, camshaft bushings). The conducted studies allow concluding that the coolant, in the presence of an insufficient concentration of anti-corrosion additives in it, as well as when it penetrates the oil system, has a sufficiently significant effect on the wear and destruction of the surface layer of the internal combustion engine parts. [ABSTRACT FROM AUTHOR]

The purpose of this review is to investigate the dental caries disease process and its impact on the oral cavity among children with deciduous (primary) teeth. Primarily, this paper aims to provide an overview of dental caries prevalence among children worldwide and inform the public of the significance of primary teeth in the development of permanent teeth. Dental caries, commonly called dental cavities or tooth decay, are the result of bacteria metabolizing dietary sugars or fermentable carbohydrates in the mouth. Research has shown that untreated cavities in the deciduous dentition can eventually affect the growth and development of the permanent dentition. Although the bacteria are transferable, dental caries are preventable. Most of the global population currently has or will have a cavity in their lifetime. This is indicative of the severity and global prevalence of tooth decay in children. Identification of common habits and practices that lead to disease progression can inform targeted interventions educating the public on the significance of maintaining healthy primary teeth for proper development of permanent teeth and provide insight on reduction or prevention of childhood caries. [ABSTRACT FROM AUTHOR]

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A key requirement to achieve sustainable high-speed flight and efficiency improvements in space access lies in the advanced performance of future propulsive architectures. Such concepts often feature high-speed nozzles, similar to rocket engines, but employ different configurations tailored to their mission. Additionally, they exhibit complex interaction phenomena between high-speed and separated flow regions at the base, which are not yet well understood. This paper presents a numerical investigation on the aerodynamic performance of a representative, novel exhaust system, which employs a high-speed nozzle and a complex-shaped cavity region at the base. Reynolds-Averaged Navier-Stokes computations are performed for a number of nozzle pressure ratios (NPRs) and freestream Mach numbers in the range of 2.7 < NPR < 24 and 0.7 < M∞ < 1.2, respectively. The corresponding Reynolds number lies within the range of 1.06×10∞=1.2 and high NPRs, the cavity has a significant effect on the aerodynamic performance, transitioning nozzle operation to underexpanded conditions. This results in approximately 12% higher drag coefficient compared to the noncavity case and shifts the minimum NPR required for positive gross propulsive force to higher values. [ABSTRACT FROM AUTHOR]

Abstract Ferroelectric thin films hold significant promise in various nanoelectronic applications, demanding precise control over their domain structures. While electrical field‐driven polarization switching is currently employed, it often leads to undesirable side effects. In contrast, mechanical switching offers a voltage‐free alternative but faces challenges in thicker films. Recent breakthroughs have demonstrated stable mechanical switching in films up to 200 nm thick, attributed to the presence of nanocavities. These nanoscale voids are believed to facilitate domain transitions, serving as essential pinning centers. In this study, mechanical domain switching in thick ferroelectric films is investigated using phase‐field modeling, with a specific focus on evaluating the influence of nanocavities on domain stability. The effects of cavity parameters (size, depth, and dielectric properties) on mechanical switching stability under various applied pressures are systematically examined. The findings reveal the intricate interplay between these factors and outline the conditions for stable mechanical switching. Furthermore, phase‐field simulations are employed to showcase the energetic mechanisms governing nanocavity‐assisted mechanical switching, while also highlighting the pivotal role of these defects as pinning centers. This investigation elucidates the nanocavity‐assisted mechanical control of polarization and the potential for optimizing thin film design through nanocavity engineering, thus enabling mechanical switching across substantial film thicknesses.

Using the reaction–diffusion model for hydrogen (H) trapping in spherical cavities in metals (Zibrov and Schmid, 2022), we theoretically analyze the case of H trapping only in chemisorption sites at the cavity surface. We show that the model can be reduced to a form that is similar to the conventional model of H trapping in point defects. The reduced model includes analytical expressions for correction factors to account for correlated H retrapping by the same cavity and inhomogeneous H potential energy landscape in the vicinity of the cavity surface. We show that these correction factors play a significant role in thermal desorption (TDS) simulations only in the case of very low cavity number densities (detrapping-limited regime), which is rarely encountered in experiments.

An inducer is a key component in a cryogenic pump to improve its cavitation performance. The thermodynamic effects of the cryogenic medium make the cryogenic cavitation flow extremely complicated. For this reason, it is crucial to investigate the cryogenic cavitation flow of the inducer which is equipped upstream of the cryogenic pump. In this paper, the isothermal cavitation model is modified based on the law of heat conduction, and the cryogenic cavitation model of the inducer is developed by considering thermodynamic effects. The turbulence model is also modified to account for the compressibility of cryogenic cavitation flow. The methods of numerical calculations are performed to investigate the influence of thermodynamic effects on cryogenic cavitation of the inducer. The law of the spatio-temporal evolution of cryogen cavitation in the inducer is clarified. The initial position, development and collapse phenomenon of cavitation are obtained. The relationship between the generation and collapse of the cavitation and the work capacity of the inducer’s blade, the relationship between thermodynamic effects and the influence of the inducer’s blade tip leakage vortex and thermodynamic on cryogenic cavitation of the inducer are revealed.

In this work, we build upon our previous finding that hydrodynamic porosity is an exponential function of pore-scale flow velocity (or interstitial Reynolds number). We previously discovered this relationship for media with a square cavity geometry—a highly idealized case of the dead-ended pore spaces in a porous medium. Thus, we demonstrate the applicability of this relationship to media with other cavity geometries. We do so by applying our previous analysis to rectangular and non-rectangular cavity geometries (i.e., circular, and triangular). We also study periodic flow geometries to determine the effect of upstream cavities on those downstream. We show that not only does our exponential relationship hold for media with a variety of cavity geometries, but it does so almost perfectly with a coefficient of determination (R2) of approximately one for each new set of simulation data. Given this high fit quality, it is evident that the exponential relationship we previously discovered is applicable to most, if not all, unwashed media.

This extensive review aims to provide a thorough understanding of entropy generation (Egen) in confined conduits, or enclosures, by examining a vast array of peer-reviewed research. The review covers various studies on Egen in enclosures with different geometric configurations and highlights the significant effects of thermo-physical dynamics, such as temperature gradient, viscous dissipation, frictional drag, and magnetic field strength, on Egen characterization. The review covers a broad range of studies that investigate Egen in enclosures with diverse geometric configurations and different types of fluids, including air, water, and various types of nanofluids. Furthermore, the review also includes different enclosure structures, such as I, L, C, U, semicircular, triangular, square, rectangular, rhombic, trapezoidal, polygonal, and channel types, as well as wavy wall configurations. Notably, the review also encompasses both 2D and 3D cases to present a complete comprehension of Egen in confined conduits. In addition, the review carefully evaluates the validity methods utilized in numerical investigations, incorporating a diverse array of mesh types and sizes utilized in research. A thorough examination of the vast literature demonstrates that enclosures with obstacles, such as single or multiple rotating cylinders, exhibit a noticeable increase in Egen. Also, the review highlights that the use of nanofluids significantly increases Egen. These findings have important practical implications in the analysis of thermofluid systems, including but not limited to heat exchangers, chip cooling, food storage, solar ponds, and nuclear reactor systems. Based on the comprehensive review conducted in this study, several future research directions have been proposed for the emerging field of Egen in enclosures. This study explores the intricate mechanisms of Egen in enclosures and highlights potential avenues for further investigation in this area. These insights will contribute to the advancement of the knowledge base and practical applications of thermofluid systems, including heat exchangers, chip cooling, food storage, solar ponds, and nuclear reactor systems.

The aim of this study was to analyze the features of the spatial organization of the endoinulinase molecule from Aspergillus ficuum after its binding to mono-, di-, and polysaccharides. This study examined changes in volume and number of internal cavities upon binding of inulinase to mono- (glucose, fructose), di- (sucrose, mannose), and polysaccharides (inulin). Transformations in the quantity and length of tunnels and pores were described, and the reorganization of the composition and localization of charged and hydrophobic amino acid residues clusters on the surface of the enzyme molecule was analyzed. It was shown that the models of inulinase in the complex with sucrose (an alternative substrate) and mannose (an activator) exhibit the same types of internal structures. A similar pattern was found in the formation of complexes with fructose (a reaction product) and glucose (an inhibitor). In addition, it was established that both charged and hydrophobic clusters do not undergo significant changes in chemical composition after the binding of inulinase to mono-, di-, and polysaccharides, i.e., the interaction between inulinase and carbohydrates mentioned above primarily affects the internal structures of the enzyme. The specificity of the binding of inulinases to various ligands should be taken into account while developing modern industrial biocatalysts based on inulinase. [ABSTRACT FROM AUTHOR]

A computational three-dimensional modeling of microchannel heat sink (MCHS) with fan cavity and four different rib configurations along with secondary channels (SCs) has been performed in detail to identify the influence of geometrical parameters on characteristics of heat transfer and provide insight into optimum configuration. The adverse effect of high processing speed and heat flux demands lower operational temperature at the expense of high pumping power in order to increase the lifespan of electronic equipment. Single phase, laminar flow of fluid is considered in the Reynolds number range from 136 to 588. The novel design of the SC benefits heat transfer enhancement by the increase in flow area, originates secondary flows subsequently transforms into symmetric counter-rotating vortices on the basis of rib, however, the influence of the rib blocking effect also depletes, resulting in minimal pressure drop. The comparison between various rib structures confirms that the FC-FTR-SC configuration acquired superior heat transfer performance with a TP of 2.07, at Re = 261. The FC-FTR-SC configuration has a great deal of evidence that pumping power decreases by 10.1% and TP increases by 11.7% as β increases from 0.5 to 1.25. The influence of four geometric parameters: relative width of rib (α), relative width of the SC (β), relative length of cavity (γ), and relative angle of the SC (ϕ) on heat transfer enhancement and pressure drop have been performed using parametric optimization, response surface methodology. [ABSTRACT FROM AUTHOR]

This paper describes the elemental and phase composition, microstructure, and superconducting properties of Nb3Sn deposited by magnetron sputtering. The films were deposited on sapphire substrates using three different techniques: co-evaporation, layer-by-layer deposition of Nb and Sn, and sputtering of a stoichiometric Nb3Sn target. The influence of magnetron operation mode on the as-deposited film element composition is described. After high-temperature annealing at 700–900 °C, the results indicate the formation of superconductive films. The highest critical temperature of 16.9 K was obtained for the film deposited at a stoichiometric Nb3Sn target and annealed at a temperature of 800 °C for 12 h. These results could be used for superconducting radio-frequency applications. [ABSTRACT FROM AUTHOR]

This work contributes to study the particle projection mechanism during gas injection on a molten steel bath surface. The studied element is called "dome". It results from a cluster of particles which is propelled and molded onto the vault of the VOD installation. A bibliographical analysis of previous projection studies leads toward two main topics: an analytic model to characterize the collected projections and a chemical analysis to trace the emission droplets. The main result leads to observe that the predicted droplet size and dome quantity go hand in hand with results obtained experimentally for the studied casting. Indeed, based on semi-empirical equations in literature, an analytical model predicts an average propelled particle size of about 500 μm with a dome mass of one-Ton. Furthermore, the metallographic analysis of some samples highlight a crystallization of seeds linked each other and, the presence of spherical droplets size between 100 and 800 µm. [ABSTRACT FROM AUTHOR]

We prove spectral stability results for the $ curl curl $ operator subject to electric boundary conditions on a cavity upon boundary perturbations. The cavities are assumed to be sufficiently smooth but we impose weak restrictions on the strength of the perturbations. The methods are of variational type and are based on two main ingredients: the construction of suitable Piola-type transformations between domains and the proof of uniform Gaffney inequalities obtained by means of uniform a priori $ H^2 $-estimates for the Poisson problem of the Dirichlet Laplacian. The uniform a priori estimates are proved by using the results of V. Maz'ya and T. Shaposhnikova based on Sobolev multipliers. Connections to boundary homogenization problems are also indicated.

The presence of radiation-induced defects and the high temperature of implantation are breeding grounds for helium (He) to accumulate and form He-induced defects (bubbles, blisters, craters, and cavities) in silicon carbide (SiC). In this work, the influence of He-induced defects on the migration of strontium (Sr) implanted into SiC was investigated. Sr-ions of 360 keV were implanted into polycrystalline SiC to a fluence of 2 × 1016 Sr-ions/cm2 at 600°C (Sr-SiC). Some of the Sr-SiC samples were then co-implanted with He-ions of 21.5 keV to a fluence of 1 × 1017 He-ions/cm2 at 350°C (Sr + He-SiC). The Sr-SiC and Sr + He-SiC samples were annealed for 5 h at 1,000°C. The as-implanted and annealed samples were characterized by Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and Rutherford backscattered spectrometry (RBS). Implantation of Sr retained some defects in SiC, while co-implantation of He resulted in the formation of He-bubbles, blisters, and craters (exfoliated blisters). Blisters close to the critical height and size were the first to exfoliate after annealing. He-bubbles grew larger after annealing owing to the capture of more vacancies. In the co-implanted samples, Sr was located in three regions: the crystalline region (near the surface), the bubble region (where the projected range of Sr was located), and the damage region toward the bulk. Annealing the Sr + He-SiC caused the migration of Sr towards the bulk, while no migration was observed in the Sr-SiC samples. The migration was governed by “vacancy migration driven by strain fileds.”

The effects of helium (He), silver (Ag) and strontium (Sr) ions triple implanted into polycrystalline silicon carbide (SiC) were investigated. Ag ions of 360 keV were first implanted into polycrystalline SiC to a fluence of 2 × 1016 cm−2 at 600 °C, followed by implantation of Sr ions of 280 keV to a fluence of 2 × 1016 cm−2 also at 600 °C (Ag + Sr–SiC). Some of Ag + Sr–SiC samples were then implanted with 17 keV He ions to a fluence of 1 × 10 17 cm−2 at 350 °C (Ag + Sr + He–SiC). Some of the dual (Ag + Sr–SiC) and triple (Ag + Sr + He–SiC) implanted samples were annealed at 1000 °C for 5 h. Both dual and triple implantation resulted in the accumulation of defects without amorphization of SiC structure. Moreover, triple implantation also resulted in formation of elongated He nano-bubbles and cavities in the damaged SiC accompanied by the appearance of blisters and craters on the surface. Healing of some structural defects was observed after annealing at 1000 °C in both dual and triple implanted samples. Implantation of Sr caused pre-implanted Ag to form precipitates indicating some limited migration while implantation of He caused some migration of both Ag and Sr. The migration of Ag was accompanied by formation of bigger precipitates trapped in He-cavities. Annealing the triple implanted caused the migration of both Ag and Sr governed by trapping of both implanted species by cavities due to some exo-diffusion of He. No migration was observed in the dual implanted samples annealed at 1000 °C. Hence, He bubbles assisted migration of implants and He cavities trap the implanted species.

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Using silver diamine fluoride and glass ionomer cement (SMARTSilver Modified Atraumatic Restorative Treatment) in pediatric dentistry can provide a cost-effective, fast, and non-invasive approach to restoring cavities. Silver diamine fluoride is a liquid fluoride that prevents cavity-causing germs from spreading. This can be paired with glass ionomer cement to fill cavities and restore tooth structure. This therapy technique also takes less time than typical restorative treatments so that children may be treated sooner and with fewer disturbances to their daily life. Silver diamine fluoride and glass ionomer cement have become popular in pediatric dentistry for treating cavities due to their numerous benefits. This literature review comprehensively assesses the utilisation of Silver Diamine Fluoride (SDF) and Glass Ionomer Cement (GIC) in pediatric dentistry in the context of SMART-Silver Modified Atraumatic Restorative Treatment. It summarises the findings of existing literature regarding the dental procedures, treatment approaches, and materials used for the treatment, as well as the clinical outcomes, advantages, limitations, and potential applications. SMART-Silver Modified Atraumatic Restorative Treatment is an effective and minimally invasive technique that is particularly useful during the current COVID-19 pandemic, as it does not require any aerosol output while allowing dental caries to be managed without local anaesthesia in a timely, efficient, and cost-effective manner.[1] It also eliminates the need for extracting and replacing decayed teeth, thus restoring dental health and overall quality of life. In addition, the Silver-modified Atraumatic Restorative Technique is an ideal approach for managing preschool caries, as it can halt and control the progression of caries without adversely affecting any surrounding healthy tooth structures. This review establishes the utility of SMART-Silver Modified Atraumatic Restorative Treatment and underlines its effectiveness in pediatric dentistry, particularly today. [ABSTRACT FROM AUTHOR]

A chute rim seal cavity has been instrumented with time-resolved and time-averaged pressure transducers as well as a gas concentration measurement system at the Oxford Rotor Facility. The unsteady pressure transducers were unevenly distributed along the circumference generating 15 combinations of angular spacing to conduct a phase analysis. The test operating conditions were modified through different configurations of mainstream flow, a range of rotational speeds and several rates of purge flow to obtain test data in the regimes of rotationally-driven, pressure-driven, and combined ingestion. The rotating unsteady flow structures within the rim seal cavity were studied through a combination of phase analysis of dynamic pressure signals and inspection of the frequency domain. The introduction of mainstream flow (axial and swirled) increased the overall unsteadiness exciting an additional band of lower frequencies. The phase analysis revealed these were associated with acoustic waves, providing the first experimental evidence of the presence and coexistence of inertial and acoustic waves in the rim seal cavity. The interaction of the inertial and acoustic waves strongly depends on the operating conditions, and may be linked to changes in sealing effectiveness. [ABSTRACT FROM AUTHOR]

For turbomachinery working in wet-gas conditions, liquid-phase fluid may worsen the rotordynamic characteristic of an annular seal, which induces a subsynchronous vibration problem and destabilizes the rotor-bearing system. The hole-pattern seal, demonstrated as effective to eliminate synchronous or subsynchronous vibrations for gas turbomachinery, is an ideal seal scheme to increase rotor stability and liquid tolerance capability of wet-gas turbomachinery. In this paper, the leakage and rotordynamic characteristics of a hole-pattern seal are numerically investigated under wet-gas conditions, using a three-dimensional transient CFD-based perturbation method. The accuracy and reliability of the present numerical method are demonstrated based on published experimental data. The rotordynamic force coefficients are presented and compared for the wet-gas hole-pattern seal with various inlet liquid volume fractions (LVF = 0%-20%), rotor speeds (⁠ω  = 0-20 krpm), inlet preswirl ratios (⁠Sr  = -0.2-0.5), and pressure ratios (⁠Pr  = 0.3-0.7). Numerical results show that the hole-pattern seal possesses desired tolerance capability for high inlet liquid volume fraction (LVF) of up to 20%. With inlet LVF increasing from 0 to 20%, the effective damping of the hole-pattern seal increases by about 50%, suggesting an improvement in rotor stability. The leakage flow rate of the oil-air mixture increases by 97.5%, combined with the sharply increasing oil leakage flow rate (by 636%) and decreasing air leakage flow rate (by 40%). The increasing rotor speed and inlet preswirl ratio both result in an obvious increase (by 50%) in the cross-coupled stiffness, yielding a smaller effective damping and worse rotor stability. With the increase in pressure ratio, all the rotordynamic force coefficients show a weaker frequency dependency and smaller magnitudes. The swirl velocity in the seal clearance can cause an accumulation of the liquid component in the hole cavities. With the increase of swirl velocity, more liquid component accumulates in the hole cavities, and the main accumulation position gradually moves upstream. [ABSTRACT FROM AUTHOR]

• A hybrid analytical method is built to study vibrations of the sandwich plate with z-direction reinforcements and cavities. • Both the sandwiches with hard and soft cores are considered in the analytical method that utilizes the layerwise model. • For the soft core sandwich, the layerwise model shows a much better accuracy than the existing equivalent single-layer model. • The accuracy of present method decreases at the high frequency since the homogenization of core neglects local vibrations. This paper presents a multi-functional sandwich plate with z-direction reinforcements and cavities that has the potential to meet the pressure resistance and the acoustic stealth requirement of the underwater equipment in deep sea. In order to predict its free and forced vibrations in both vacuum and water, a hybrid analytical method is proposed by combining a multi-level homogenization model and a layerwise model. The core with z-direction reinforcements and cavities is homogenized and effective elastic constants are calculated by the Mori-Tanaka formula. Vibration equations of the sandwich plate are derived utilizing the layerwise model based on the first-order shear deformation theory. The water effect is taken into account by the Euler's equation. Vibration results are solved under simply supported boundaries. Validation studies and parameter analyses are then conducted. It is found that different from the existing theoretical approach based on the equivalent single-layer model that is only applicable for the sandwich with a hard core material, the present hybrid analytical method is well suitable for vibration predictions of the sandwich plate with z-direction reinforcements and cavities, no matter the hard or soft core. Besides, due to the homogenization of the three-phase core and the neglecting of local vibrations in the layerwise model, the present analytical method only predicts accurate free vibrations when the half wave numbers are less than numbers of cavities in x and y directions, and also just shows the high precision in force vibration calculations as the maximum analysis frequency is less than the natural frequency of the mode corresponding to numbers of cavities. [ABSTRACT FROM AUTHOR]

The production of prismatic dislocation loops in nuclear reactor core materials results in hardening because the loops impede dislocation motion. Yielding often occurs by a localised clearing of the loops through interactions with gliding dislocations called channeling. The cleared channels represent a softer material within which most of the subsequent deformation is localized. Channeling is often associated with hypothetical dislocation pileup and intergranular cracking in reactor components although the channels themselves do not amplify stress as one would expect from a pileup. The channels are often similar in appearance to twins leading to the possibility that twins are sometimes mistakenly identified as channels. Neither twins nor dislocation channels, which are bulk shears, produce the same stress conditions as a pileup on a single plane. At high doses, when cavities are produced (either He-stabilised bubbles at low temperatures or voids at high temperatures), there can be reduced ductility because the material is already in an equivalent advanced stage of microscopic necking. He-stabilised cavities form preferentially on grain boundaries and at precipitate or incoherent twin/ε-martensite interfaces. The higher planar density of the cavities, coupled with the incompatibility at the interface, results in a preferential failure known as He embrittlement. Strain localisation and inter- or intragranular failure are dependent on many factors that are ultimately microstructural in nature. The mechanisms are described and discussed in relation to reactor core materials. [ABSTRACT FROM AUTHOR]