Increase In Cavity Size Research Articles

Transmissible topological edge states based on Su–Schrieffer–Heeger photonic crystals with defect cavities

Abstract Topological photonic crystals have great potential in the application of on-chip integrated optical communication devices. Here, we successfully construct the on-chip transmissible topological edge states using one-dimensional Su–Schrieffer–Heeger (SSH) photonic crystals with defect cavities on silicon-on-insulator slab. Different coupling strengths between the lateral modes and diagonal modes in photonic crystal defect cavities are used to construct the SSH model. Furthermore, two photonic SSH-cavity configurations, called α and β configurations, are designed to demonstrate the topological edge states. Leveraging the capabilities of photonic crystal transverse electric modes with on-chip transmission, we introduced a waveguide to excite a boundary defect cavity and found that the transmission peak of light, corresponding to the topological edge state, can be received in another boundary defect cavity, which is caused by the tunnel effect. Moreover, the position of this peak experiences a blue shift as the defect cavity size increases. Therefore, by tuning the size of the SSH defect cavity, on-chip wavelength division multiplexing function can be achieved, which is demonstrated in experiments. The ultrafast response time of one operation can be less than 20 fs. This work harmonizes the simplicity of one-dimensional SSH model with the transmissibility of two-dimensional photonic crystals, realizing transmissible on-chip zero-dimensional topological edge states. Since transmission peaks are highly sensitive to defect cavity size, this configuration can also serve as a wavelength sensor and a reconfigurable optical device, which is of substantial practical value to on-chip applications of topological photonics.

Seismic response study of shield tunnel with lateral karst cavity under SV waves

This paper investigates the seismic effects of karst cavity size and span on the shield tunnel subjected SV waves, using the case project of Dalian Metro Line 5. The viscous spring artificial boundaries are employed for the seismic input, which is validated to assure accuracy. The shield tunnel is simplified according to the method of the equivalent bending stiffness model. The deformation and stress distribution are analyzed to investigate the dynamic response of the shield tunnel under SV waves at different angles. The tunnel damage state is evaluated by the criterion proposed by authors in previous research. The results show that a larger cavity size can lead to more deformation in the tunnel. There are significant differences in the spatial distribution of deformation and stress affected by the incident angle. As the cavity size increases, the stress near the cavity decreases significantly. Only the cavity size is greater than or equal to 0.8D (D is the tunnel’s diameter), there are damage concentration areas on the bottom, and the damage area shifts towards to circumferential direction. The deformation and stress distribution are highly affected as the span increases in the Z direction, followed by the Y direction, and almost no effect in the X direction. The damage area increases as the increase of span in three directions. There are damage concentration areas of the bottom only as the span is 1.5D in the Z direction. Compared with the effect of cavity size, the results indicate that the damage concentration is not solely related to cavity span in one single direction.

Nanoscale deformation of crystalline metals: Experiments and simulations

In the present work, we performed experiments and molecular dynamic simulations to study the atomic physical process and deformation mechanism involved in nanoscale deformation of crystalline metals. By contact deforming bulk metals using hard molds with different cavity sizes at various temperatures and different stress levels, the flow of metals (e.g., Au and Ag) into nanocavities is quantified by the aspect ratio of molded micro-/nanorods, based on which the dependence of deformability on cavity size, temperature and stress is revealed. It is found that the critical forming pressure is determined by the entering barrier. Once the entering barrier can be overcome, quantified by the aspect ratio of metal nanorods, the molding efficiency increases with the cavity size decreasing. Moreover, three deformation modes are uncovered in the nanoscale plastic flow of metals and directly related with the atomic physical processes, i.e. atomic diffusion, dislocation nucleation, multiplication and movement. In the dislocation dominated temperature regime, a transition of deformation mode from burst growth to continuous growth is observed as the cavity size increases. When the mold cavity size is very small (100-101 nm), the metal atoms flowing in a mold cavity will arrange amorphously even at low temperature, which usually only occurs at high temperature for large cavity sizes. Therefore, reducing the size shows the same effect as increasing the temperature, making nanomolding easier.

Effect of the use of dental loupe on cavity size after removal of the aged composite resin restorations

Introduction: The aim of the present study was to evaluate the effects of removal of artificially aged and non-aged resin composite restorations in-vitro with or without aid of dental loupe on cavity size change. Methods: A low-speed hand piece was used to prepare occlusal cavities in 32 acrylic molar teeth. The size of cavities after cavity preparation were calculated using ImageJ software. The teeth were restored with composite resin and divided into four groups according to the use of dental loupe (2.5x magnification) (with and without magnification) and ageing effect (non-aged and aged). In order to simulate the ageing effect, samples were kept in boiling water for 8 hours. The effects of artificial ageing on the color and translucency of the resin composites used were also analyzed using spectrophotometer. Cavity sizes after the removal of restorations were re-calculated by using the ImageJ software and differences in cavity sizes were also calculated. Paired t-tests were applied to data (p < 0.05). Results: There were significant increases in cavity size using both techniques and both type of restorations although the size increase in percentage was less only when magnification was used during removal of non-aged restorations. Conclusion: Cavity size changes significantly during replacement of restorations and the use of magnification may be not of benefit in reducing the size of the change of removal of aged resin composite restorations.

Effects of helium cavity size and morphology on the strength of pure titanium

High-purity α-titanium was implanted with helium to observe cavity morphology – size, number density, and form (i.e., bubbles vs. voids) – effects on materials strength. Increasing implantation temperatures lead to an Arrhenius-type (i.e., exponential) increase in cavity size, a transition from spherical bubbles to faceted voids, and a marked increase in strength (∼20–50%). Implanted samples deformed uniformly in contrast to nano-compression of unimplanted or alloyed titanium, but pillars with the largest faceted voids developed a type of bulging localized deformation. Affected voids were repeatedly sheared, becoming rough and shrunken. Dislocation-cavity interactions and the role of helium content within cavities are considered.

Simulations of FMR for study the shape anisotropy in square hollow nanopillars

A study of ferromagnetic resonance in square hollow nanopillars was carried out, with the aim of analyzing the effects of geometry. Nanopillars (NPs) with L = 120 nm length and D = 30 nm external width were studied. By fitting the data for parallel field and using the Primary peak, the anisotropy field was HA = 97.2, 116.4 and 144.5 kA/m for d = 0, 10 and 20 nm, respectively. For perpendicular field, HA = 175, 193 and 251 kA/m for d = 0, 10 and 20 nm, respectively. The variations were attributed to the increase in dipole interactions, as the cavity size increases. A secondary peak was also fitted and HA = 222.5, 220 and 226.9 kA/m were obtained for parallel configuration. Thus, this secondary peak, from regions whose local field varies little with the dimensions of the cavity, were attributed to the effects of parallel edges.

The effect of cavity size on ruthenium (II) tris-(2,2-bipyridine) photophysics encapsulated within zirconium based metal organic frameworks

Metal organic frameworks (MOFs) are well known for their exceptionally large surface areas and high porosity making them ideal candidates for gas storage and adsorption, drug delivery systems, and light harvesting platforms. A class of MOF’s that have gained much attention for their exceptional hydrothermal stability are the zirconium oxide MOF’s. One in particular is Uio-66 which is composed of Zr6O8 clusters connected by benzene dicarboxylate linkers. One important characteristic of the Uio-66 series of MOFs is that extension of organic linkers results in a systematic increase in cavity size while retaining the same overall framework topology. This property affords the opportunity to examine the effects of cavity size on the photophysics of encapsulated guests. Here a comparison of the photophysics of ruthenium (II) tris-(2,2′-bipyridine) (RuBpy) encapsulated within three Zr-based MOF’s Uio-66, Uio-67, and Uio-68 is presented. All three RuBpy@Uio-xx (xx = 66, 67 or 68) materials display a bathochromic shift in the steady state spectra and an emission lifetimes that fit to a biexponential decay function. Both RuBpy@Uio-66 and RuBpy@Uio-67 exhibit extended emission lifetimes which is characteristic of deactivation of the higher energy triplet ligand field state (3LF) and depopulation from a higher energy metal-to-ligand charge transfer state (3MLCT). Interestingly, RuBpy@Uio-68 exhibits a solution like emission lifetime that would be consistent with the larger cavity providing sufficient volume for access to the 3LF state. However, closer examination of the photophysics reveals that even the larger cavity imposes a significant level of confinement although lesser than that observed for the RuBpy@Uio-66 and RuBpy@Uio-67 systems.

Oriented thermal etching of hollow carbon spheres with delicate heat management for efficient solar steam generation

Hollow carbon spheres (HCSs) with controllable morphology and structure have received considerable attention in the field of energy conversion and storage. Herein, monodispersed HCSs with cavity sizes tuned from 100 nm to 800 nm and shell thickness from 450 nm to 50 nm were successfully synthesized through a unique template-free thermal-etching method. It was evidenced that the dynamically controllable synthesis of HCSs was attributed to the “inside-out” oriented thermal oxidation etching of carbon spheres (CSs) induced by the differentiated “core-shell” chemical structures. Comparing to CSs, the obtained HCSs exhibited much increased efficiency for solar-driven interfacial steam generation (SISG), reaching as high as 88.9%, which outperforms most of the previously reported carbon-based materials. It was then demonstrated that the rational heat management for both photothermal and thermal-evaporation conversion is essential to achieve satisfying SISG efficiency. Depending on the increasing cavity sizes, HCSs presented gradual increases in both photothermal conversion and thermal-evaporation performances, mainly attributed to the improved light absorption and the delicate heat management, respectively. However, the further increase in cavity size resulted in excessive heat loss and presented decreased thermal-evaporation performance. This work provides an alternative and promising approach to the reasonable design of hollow nanostructures with delicate heat management for efficient SISG as well as other solar energy conversion applications.

Predictions of airborne noise between unit cabins by developing a cavity transfer matrix

The unit cabin has been used to construct internal ship space for improved efficiency and to reduce budgetary costs in shipbuilding. Because the cavity is placed between unit cabins, the noise of one room is transmitted through the sound insulating panel, the cavity, and the opposite sound-insulating panel. In this study, by developing a transfer matrix of the cavity between structures, airborne noise between unit cabins was predicted. A sandwich panel, which is usually used in ships, was employed to construct a double panel, and the sound insulation performance was confirmed by changing the thickness of the cavity. To improve the reliability of numerical results, they were compared with those from experiments conducted. The results showed that as the cavity size increases, the overall sound insulation performance improves. A parameter study was also conducted on the density, Young's modulus, thickness, and thickness ratio of the core of the sandwich panel. To improve the sound insulation performance, increasing the density of the core is preferable to increasing the core thickness. The panel thickness ratio should be increased to avoid performance degradation as a result of the resonance frequency.

Anti-plane fracture problem of three nano-cracks emanating from a magnetoelectrically permeable regular triangle nano-hole in magnetoelectroelastic materials

Based on the Gurtin–Murdoch surface/interface model and complex potential theory, by constructing a new conformal mapping, the anti-plane fracture problem of three nano-cracks emanating from a magnetoelectrically permeable triangle nano-hole in magnetoelectroelastic materials with surface effect is studied. The exact solutions of the stress intensity factor, the electric displacement intensity factor, the magnetic induction intensity factor, and the energy release rate are obtained under the boundary conditions of magnetoelectrically permeable and impermeable. The numerical examples show the influence of surface effect on the stress intensity factor, the electric displacement intensity factor, the magnetic induction intensity factor, and the energy release rate under two different boundary conditions. It can be seen that the surface effect leads to the coupling of stress, electric and magnetic field, and with the increase of cavity size, the influence of surface effect begins to decrease until it tends to classical elasticity theory.

Transition and Turbulence Modeling for the Prediction of Cavitating Tip Vortices

Abstract This study evaluates the influence of transition and turbulence modeling on the prediction of wetted and cavitating tip vortices for an elliptical wing, while investigating the numerical errors. Transition modeling increases the quality of numerical predictions since the assumption of a fully turbulent boundary layer, commonly found in literature, contributes to underprediction of the tip vortex cavity size. By applying the local correlation-based transition model (LCTM) and controlling the boundary layer thickness using different turbulent inflow conditions, the pressure in the vortex was found to reduce by 20% for an Angle of Attack (AoA) of 5 deg. The consequent increase in cavity size was found to be of a similar order of magnitude. At 9 deg AoA, transition always occurs just downstream of the leading edge, making this AoA more suitable to investigate the effect of different turbulence modeling approaches. Azimuthal and axial velocity fields are validated against stereographic-particle image velocimetry (S-PIV) measurements. The time-averaged velocity profiles predicted by delayed detached-eddy simulation (DDES) and improved delayed detached-eddy simulation (IDDES) are close to the experiments; however, no velocity fluctuations and vortex dynamics are observed around the vortex. A comparison of wetted and cavitating simulations shows that the cavity leads to a change in the balance between production and destruction of turbulence kinetic energy, which reduces the turbulent diffusion in and around the cavity compared to wetted flow conditions. Consequently, the vapor flow exhibits the characteristics of a potential flow. Whether this is physically plausible remains to be investigated.

Instability and stress analysis for cavitation in soft graded elastic solids

For an infinitesimal initial cavity in homogeneous soft solids, a finite inflating pressure may cause an unbounded increase of cavity size. An asymptotic value of 2.5 times the initial shear modulus for incompressible homogeneous neo-Hookean solids is usually referred to as cavitation instability in soft solids. Recently, by detecting the drop of inflating pressure, the cavitation rheology technique has been developed to measure the local shear modulus of soft materials. In this article, we analytically extend our study on the cavitation problem to soft graded elastic solids. The mechanical property of the soft solid is assumed to vary according to power-law relations. We find that the relationship between inflating pressure and cavity size can be both a monotonic and nonmonotonic function when considering the size of initial cavity and the extent of inhomogeneity. The inflating pressure can reach a local maximum at intermediate cavity size and cause a decrease in the pressure even before fracture. The material inhomogeneity will also affect the stress distribution and the extent of stress concentration near the cavity surface. The results obtained in this article may be helpful for a better understanding of the cavitation phenomenon in complex soft solids.

Single Bubble Boiling from an Artificial Cavity

Pool boiling heat transfer is an aggressive and complex phenomenon which needs to be simplified for a better understanding of the mechanism of bubble growth and departure and how boiling heat transfer can be enhanced. Single bubble boiling heat transfer is a simple version of boiling phenomenon which has been used to study the effective elements on pool boiling heat transfer. The purpose of the present review paper is to understand how to produce single bubble pool boiling on a heated substrate and investigate, how single bubble boiling phenomenon can be affected by geometry of cavities, cavity size, wettability, roughness, working fluid, subcooling, wall superheat, heat flux, gravity, etc. It was demonstrated that cylindrical cavities are capable to generate stable and continuous bubbling, small temperature fluctuation, low superheat with short waiting period. The cylindrical cavities can be manufactured very easily in small sizes which can be a good candidate to produce single bubble pool boiling. As heat flux increases, smaller cavities start becoming active. For a given depth, as cavity size increases, the bubble growth rate and departure volume increase. Surface wettability is another complex and important factor to modify the single bubble boiling heat transfer. Wettability depends mainly on force balance at the triple contact line which relies on solid–liquid–gas materials. In case of hydrophobic surfaces, the triple line has tendency to move toward liquid phase and expand the radius of triple line, so the initiation of nucleation is easier, the waiting time is shorter, the downward surface tension force becomes bigger since radius of triple line is larger, the bubble departure volume is higher and bubble growth period is longer. The effects of the rest of main parameters on single bubble boiling are discussed in this paper in details. In addition, a theoretical model is developed to predict the liquid-vapor interface for the single bubble boiling. The theoretical model is compared with single bubble boiling experimental data and good results observed.

Dexrazoxane preferentially mitigates doxorubicin cardiotoxicity in female children with sarcoma

ObjectiveWe sought to determine how sex and dexrazoxane therapy influence cardiac remodelling in children with sarcoma receiving high-dose doxorubicin.MethodsIn a retrospective cohort of 85 children with sarcoma receiving high-dose doxorubicin,...

Studies on the mechanism of large cavity to improve the growth rate of large diamond under HPHT conditions

In this work, we investigate the effect of cavity size on the change of the physical fields of diamond synthetic cavity and the mechanism of large cavity to improve the growth rate of the large single crystal diamond under high pressure and high temperature (HPHT) conditions. Finite element method (FEM) is used to simulate the temperature and convection field of the Φ15 and Φ10 cavity assemblies. Temperature simulation results indicate that the increase of cavity size leads to the increase of axial and radial temperature difference of catalyst. Convection simulation results show that the convection velocity and strength of the catalyst increases significantly with the increase of the cavity size. The increase of temperature difference and convection velocity and strength lead to the acceleration of crystal growth. The simulation results were perfectly validated by the synthetic experiments. This work not only elucidates the mechanism of large cavity to improve the growth rate, but also provides a theoretical reference for the application of the large-size cavity in the diamond synthetic industry.

Liquid dynamics in response to an impinging low-temperature plasma jet

The liquid-phase behavior induced by an atmospheric pressure plasma jet impinging onto water-based solutions was experimentally investigated. An increase in cavity size and circulation size resulting from an increase in impact force of the plasma jet with respect to a helium gas jet were observed through particle image velocimetry and cavity measurements. The increase in circulation size due to plasma discharge was larger than the increase solely due to an increase in jet impact force, suggesting additional shear along the liquid free surface evidenced by schlieren images of plasma-induced gas flow adherence after impingement. Liquid evaporation rate increased and mean liquid temperature decreased due to plasma effects on jet behavior. Plasma-induced decreases in liquid pH and temperature were contained within the circulation flow, leading to strong pH and temperature gradients within the liquid volume. Areas treated by the jet became acidic and remained more acidic than other portions of the liquid due to circulation vortices, highlighting the consequences of jet and liquid vessel parameters for plasma jet-liquid applications.

Maximizing the quality factor to mode volume ratio for ultra-small photonic crystal cavities

Small manufacturing-tolerant photonic crystal cavities are systematically designed using topology optimization to enhance the ratio between the quality factor and mode volume, Q/V. For relaxed manufacturing tolerance, a cavity with a bow-tie shape is obtained which confines light beyond the diffraction limit into a deep-subwavelength volume. Imposition of a small manufacturing tolerance still results in efficient designs, however, with diffraction-limited confinement. Inspired by numerical results, an elliptic ring grating cavity concept is extracted via geometric fitting. Numerical evaluations demonstrate that for small sizes, topology-optimized cavities enhance the Q/V-ratio by up to two orders of magnitude relative to standard L1 cavities and more than one order of magnitude relative to shape-optimized L1 cavities. An increase in cavity size can enhance the Q/V-ratio by an increase in the Q-factor without a significant increase in V. Comparison between optimized and reference cavities illustrates that significant reduction of V requires big topological changes in the cavity.

P.104 Peri-cavity atrophy after minimally invasive evacuation of intracerebral hemorrhage

Background: Intracerebral hemorrhage (ICH) remains a significant cause of morbidity and mortality. While traditional surgical techniques have shown marginal clinical benefit of ICH evacuation, minimally invasive techniques have shown some promise. Endoscopic evacuation of the hemorrhage may reduce the peri-hematoma edema and subsequent atrophy around the hemorrhage cavity. This study aims to quantify the changes in cavity volume following hematoma evacuation. Methods: Patients from the INVEST registry of minimally invasive ICH evacuation were included retrospectively if follow-up computed tomography (CT) scans were available for analysis. Hematoma cavity volumes were calculated from the immediate post-procedural and three-month follow-up CT scans using the Analyze Pro software. Results: Twenty patients had follow-up CT scans at a mean time of 93 days from hematoma evacuation. The average cavity size at follow-up was 11938.12 mm3 (SD: 6996.49). The change in cavity size compared to the prior CT was 6396.74 mm3 (median 2542; range: -1030-27543; SD: 8472.45). This represented mean growth in cavity volume of 54%. Conclusions: This study provides preliminary data describing increase in cavity size after endoscopic minimally invasive evacuation of ICH. Comparison to atrophy in conservatively-managed patients is a further planned avenue of research.

Post-irradiation annealing behavior of helium in irradiated Fe and ferritic-martensitic steels

Oxide dispersion strengthened (ODS) alloys, which contain a high number density of nano-scale oxide particles, are supposed to prevent the long-range diffusion of defects therefore enhance irradiation resistance. The large amount of interfaces between oxide particles and matrix are expected to trap helium atoms as well as vacancies and interstitial atoms. In this study, Fe, F82H-IEA steel and F82H-ODS steel were irradiated with He+ ions at room temperature. Post-irradiation annealing was carried out over a temperature range 200–600 °C with the increment of 100 °C. The change of indentation hardness and the evolution of cavities during post-irradiation annealing were investigated using nanoindentation and transmission electron microscopy (TEM). After post-irradiation annealing at 300 °C, Fe with 2000 appm He showed additional hardening, while at temperature above 500 °C, it showed a large stage of hardness recovery. On the contrary, no temperature dependence of hardness was observed in F82H-IEA steel or F82H-ODS steel during the post-irradiation annealing process. Therefore, the large stage of hardness recovery is expected to be above 600 °C for the latter materials. The reason for the additional hardening in Fe at 300 °C was speculated to be re-structure of the irradiation induced defects. TEM observations revealed the homogeneous distribution of cavities in all as-irradiated materials, and the increase in cavity size and the decrease in cavity number density after post-irradiation annealing at 650 °C. The mechanism of the formation of radiation damage and its development with post-irradiation annealing were discussed.

ASSESMENT OF CLINICAL EFFECTIVENESS OF LOSARTAN AND AMLODIPINE IN HYPERTENSIVE PATIENT WITH LEFT VENTRICULAR HYPERTROPHY

Objective: Hypertension is an important worldwide public health challenge because of its high frequency and concomitant risks of cardiovascular and kidney diseases. Left ventricular hypertrophy (LVH) is defined as an increase in the mass of the LV, which can be secondary to an increase in wall thickness, an increase in cavity size, or both. Relevant study reported that LVH is one of the major and independent risk factors for coronary artery disease, heart failure, serious dysrhythmias, and sudden death. Thus, regression of LVH is a primary pharmacologic objective. The objective of this study is to assess the effectiveness of losartan and amlodipine in regression of LVH and to monitor the adverse effects of these drugs on monotherapy. The study also focused to estimate the clinical effectiveness of specified drugs in lowering hypertension.Methods: The study conducted was retrospective, prospective, comparative study extended over 1 year on 28 patients based on inclusion and exclusion criteria.Results: Both these drugs cause regression of LVH with a decrease in LV mass index value; it is seen that amlodipine is better in controlling elevated blood pressure (BP), especially diastolic BP. In statistical analysis, regression of LVH was found to be correlated with reduction of BP.Conclusion: Incidence of adverse effect was found to be prominent in amlodipine group. Thus, losartan was found to be better in regressing LVH than amlodipine.Keywords: Left ventricular hypertrophy, Amlodipine, Losartan.