Open Cavity Research Articles

ITO/Si/ITO semi-cone-shell chiral complexes on silicon nanocones with broadband circular dichroism in the mid-infrared wavelength.

This paper proposed ITO/Si/ITO semi-cone-shell chiral complexes on silicon nanocones with broadband CD in the mid-infrared band. The experimental results show that when the deposition angle θ = 45°, the first ITO deposition of ta = 100 nm, the second Si deposition of tb = 200 nm with the azimuth angle unchanged, and the third ITO deposition of tc = 200 nm after rotating the azimuth angle of 60°, the prepared chiral structure has a broadband CD response in the mid-infrared band of 2.5-4 µm. The broadband CD effect is produced by the internal resonance of the three-dimensional open cavity. The cone structure can be regarded as a plurality of planar open resonant rings with different diameters, and these rings resonate at different wavelengths. The experimental results also show that the proposed chiral ITO structure exhibits a better broadband CD response than that of the structure composed of traditional metal Ag. Such a chiral structure provides a new method for the design of CD devices in the mid-infrared band.

Structure of SARS-CoV-2 M protein in lipid nanodiscs.

SARS-CoV-2 encodes four structural proteins incorporated into virions, spike (S), envelope (E), nucleocapsid (N), and membrane (M). M plays an essential role in viral assembly by organizing other structural proteins through physical interactions and directing them to sites of viral budding. As the most abundant protein in the viral envelope and a target of patient antibodies, M is a compelling target for vaccines and therapeutics. Still, the structure of M and molecular basis for its role in virion formation are unknown. Here, we present the cryo-EM structure of SARS-CoV-2 M in lipid nanodiscs to 3.5 Å resolution. M forms a 50 kDa homodimer that is structurally related to the SARS-CoV-2 ORF3a viroporin, suggesting a shared ancestral origin. Structural comparisons reveal how intersubunit gaps create a small, enclosed pocket in M and large open cavity in ORF3a, consistent with a structural role and ion channel activity, respectively. M displays a strikingly electropositive cytosolic surface that may be important for interactions with N, S, and viral RNA. Molecular dynamics simulations show a high degree of structural rigidity in a simple lipid bilayer and support a role for M homodimers in scaffolding viral assembly. Together, these results provide insight into roles for M in coronavirus assembly and structure.

Double diffusive convection of CuO + MWCNT hybrid nanofluid in an inclined open cavity with internal heat generation/absorption

An intention of the current study is to analyse the effect of double-diffusive convection in a hybrid nanofluid filled in an inclined open cavity with heat generation/absorption. The cavity walls are insulated whereas the centrally placed baffle is maintained at a high temperature. The CuO + MWCNT nanoparticles suspended in the water are used as a working hybrid nanofluid. The angle of inclination γ = 0°–90° is applied for the open cavity. The non-dimensional governing equation in the form of vorticity stream function transport is solved numerically by using the finite difference method. The behaviour of fluid flow, heat transfer, and mass transfer are presented as a contour. At various parametric conditions (q = −4 to 4, Br = −4 to 4, Le = 1–6), the average Sherwood and Nusselt numbers are calculated and explained graphically. The results report that an inclination angle suppresses the heat and mass transfer rate in an open enclosure.

MHD free convection in a partially open wavy porous cavity filled with nanofluid

Background The investigations of natural convection in open cavities admit an indispensable insight to the research community, and many research articles are published in this area as the wide range of applications in industries. We focus on investigating free convection in a partially open square cavity; the use of a wavy cold wall will have a larger surface than a straight cold side wall for a fixed distance. Methods This numerical investigation is aimed at MHD free convection in a partially open wavy porous cavity filled with nanofluid. The cavity is positioned vertically, and the wavy cavity wall on the right side maintains a constant low temperature. The top wall is partially opened, the magnetic field is applied horizontally from the left wall, and the bottom and top walls are adiabatic. The solutions of dimensionless governing equations are computed by the finite difference method (FDM) for a wide range of governing parameters: nanoparticles volume fraction Hartmann number Rayleigh–Darcy number the position of a partial opening length of the opening undulations number per unit length and dimensionless wave amplitude Significant findings Obtained results reveal that overall convection is reduced as the nanoparticle volume fraction or Hartmann number augments, and the effect of the position of the opening is minor at a higher value of the Hartmann number; also, the waviness is an increasing factor for the average Nusselt number.

Does treating proximal cavities in primary molars non-restoratively affect intra-arch space and alignment of successor teeth negatively? A 4-year longitudinal study.

BackgroundRemoving plaque with toothbrush and toothpaste from proximal cavities in primary molars without restoring them follows sound cariological principles. But does this treatment affect space for and alignment of their permanent successors negatively?HypothesisThere is no difference in impaction and displacement of the premolars, as well as in the D+E space in quadrants with three different statuses of the proximal surface of primary molars over a 4-year period.MethodsA total of 936 quadrants (466 maxillary and 470 mandibular quadrants) in 233 children were assessed. Treatment of cavities in the proximal surfaces of the primary molars consisted of amalgam and ART restorations using high-viscosity glass-ionomer cement, and cleaning of open large- and medium-sized cavities with toothbrush and toothpaste (UCT) under supervision for 220 days per year over 3 years. Dental casts were made at baseline, and after two, three, and 4 years. The D+E spaces were measured digitally. Status of the proximal surface of the primary molars was assessed by two calibrated examiners, and quadrants were grouped into normal anatomy, defective restoration, and proximal cavity. ANCOVA, ANOVA and LSD tests were applied.ResultsThere was a statistically significant difference between groups (p <= 0.001) and between evaluation times (p < 0.001), for the D+E space in both the maxilla and mandible. A sex difference related to the D+E space in the maxilla was found (p = 0.007). For boys, quadrants in the maxilla of the group ‘proximal cavity’ showed a significant shorter D+E space when compared to quadrants of the group ‘normal anatomy’ at the 3- and 4-year evaluation time. For girls the difference between the two groups was only present at the 3-year evaluation time. There was no significant difference between the D+E space in quadrants with defective restorations and those with normal anatomy in the mandible and in the maxilla. Displacement and impaction of the premolars showed no significant difference between groups.ConclusionPrimary molars with open proximal cavities that are cleaned with toothbrush and toothpaste do not result in displacement and impaction of the successor teeth, neither do primary molars with defective restorations in proximal tooth surfaces.

Free convection of temperature-dependent thermal conductivity based ethylene glycol-Al2O3 nanofluid in an open cavity with wall heat flux

The natural or free convection flow in an open cavity filled with ethylene glycol-Al2O3 nanofluid has been integrated numerically using the multiple-relaxation-time (MRT) lattice Boltzmann method (LBM) with the Graphics Process Unit (GPU) acceleration. The applications of this type of problem frequently appear in open-door ovens and refrigerators and in the cavities of central solar receptors. The ceiling and bottom walls of the cavity are thermally adiabatic. The right side of the cavity is fully opened while heat flux condition is imposed on its opposite wall. The thermal conductivity of the nanofluid varies with fluid temperature. Numerical simulations have been conducted for a fixed Prandtl number, Pr=16.6, with varying other controlling parameters, i.e., the Rayleigh number from Ra=105 to 107, and nanoparticle volume fraction from 0 to 5%. The streamlines, isotherms, mid-line temperature and velocity distributions, and the rate of heat transfer regarding the Nusselt number have been presented in this article. The isolines and tabular form give the local and total entropy generation due to the fluid friction and temperature gradients. The tangential and normal velocity components grow dramatically as Ra increases; however, the temperature diminishes with Ra. Also, the locally distributed Nusselt number increases in magnitude with nanofluids’ volume fraction and Rayleigh number. The total entropy enhances significantly for the augmentation of the nanoparticles volume fraction, and the entropy due to fluid friction dominates over the entropy generated by the temperature gradients.

Heat transfer and entropy analysis for nanofluid flow in a semi-circular open cavity under mixed convection

This paper presents a numerical simulation of nanofluid flowing in an open cavity under mixed convection by considering various heat transfer zones. To enhance the heat transfer, water was augmented with copper nanoparticles at different ϕ (volume fraction of nanoparticles) values. The present paper aims to determine the optimal position which maximizes the heat transfer in a circular open cavity. Also, in this research the investigation of combined convection flow in a specific geometry, taking into account the changes in the flow parameters, is an attempt to model the temperature field and heat transfer. For this purpose, the nanofluid flow for Reynolds numbers of Re =10, 50 and 100 is investigated. On the other hand, the hot areas in the curved part of the open cavity are separated in various cases. The results show that due to the low velocity of the fluid in the circular part of the cavity, especially in the hot wall area, most of the fluid exchange is due to natural convection due to density difference and the hot areas are strengthen the flow circulation. The exchange is also improved by increasing Re (Reynolds number) or the momentum term, and the distribution of T (temperature) in the cavity becomes more uniform. Hot spots with low heat transfer coefficient were attenuated at higher Re. The most suitable temperature distributions were achieved for W4 and W2. By increasing ϕ, the friction factor decreases for pure water, especially in W2 and W3. However, due to fluid-surface impact at Re = 100 in W2 and W3, the friction factor does not change significantly by altering ϕ. Using a higher Re and the dominance of the fluid momentum in comparison with the viscous force, the effect of nanoparticle concentration decreases. In general, the best heat transfer occurs at higher volume fraction of nanoparticles. Finally, at all Reynolds numbers, the heat transfer increases by 8–19%. This is because nanoparticles are added to pure water (working fluid).

Development of Explainable Data-Driven Turbulence Models with Application to Liquid Fuel Nuclear Reactors

Liquid fuel nuclear reactors offer innovative possibilities in terms of nuclear reactor designs and passive safety systems. Molten Salts Reactors (MSRs) with a fast spectrum are a particular type of these reactors using liquid fuel. MSFRs often involve large open cavities in their core in which the liquid fuel circulates at a high speed to transport the heat generated by the nuclear reactions into the heat exchangers. This high-speed flow yields a turbulent field with large Reynolds numbers in the reactor core. Since the nuclear power, the neutron precursor’s transport and the thermal exchanges are strongly coupled in the MSFR’s core cavity, having accurate turbulent models for the liquid fuel flow is necessary to avoid introducing significant errors in the numerical simulations of these reactors. Nonetheless, high-accuracy simulations of the turbulent flow field in the reactor cavity of these reactors are usually prohibitively expensive in terms of computational resources, especially when performing multiphysics numerical calculations. Therefore, in this work, we propose a novel method using a modified genetic algorithm to optimize the calculation of the Reynolds Shear Stress Tensor (RST) used for turbulence modeling. The proposed optimization methodology is particularly suitable for advanced liquid fuel reactors such as the MSFRs since it allows the development of high-accuracy but still low-computational-cost turbulence models for the liquid fuel. We demonstrate the applicability of this approach by developing high accuracy Reynolds-Averaged Navier–Stokes (RANS) models (averaged flow error less than 5%) for a low and a large aspect ratio in a Backward-Facing Step (BFS) section particularly challenging for RANS models. The newly developed turbulence models better capture the flow field after the boundary layer tipping, over the extent of the recirculation bubble, and near the boundary layer reattachment region in both BFS configurations. The main reason for these improvements is that the developed models better capture the flow field turbulent anisotropy in the bulk region of the BFS. Then, we illustrate the interest in using this turbulence modeling approach for the case of an MSFR by quantifying the impact of the turbulence modeling on the reactor key parameters.

Demodulation of Fabry-Perot sensors using random speckles.

Random speckles are proposed to demodulate Fabry-Perot (FP) sensors in this study. A piece of multimode fiber is used to interrogate the FP transmission spectrum, and tiny spectral changes lead to significant variations in the generated speckle patterns. In the demonstration experiments, the pressure resolution of 0.001 MPa can be obtained from an open cavity FP sensor based on the convolutional neural network (CNN) demodulation algorithm. It is worth noting that the spectral differences in neighboring orders can be precisely distinguished due to the high sensitivity of speckles. Thus, the fringe-order ambiguity problem is solved and the dynamic measurement range can be greatly improved. The speckle-based demodulation scheme provides a new way to balance resolution, dynamic range, speed, and cost of FP sensors.

Solar Energy Management Using a V-Groove: An Approach Based on a Multiple Optical Path Algorithm

Angular and spectral separations of thermal radiation have become a key challenge in solar concentration or thermal management of sources radiating at extremely high or low temperatures. Reflections obtained from electromagnetic theory in an open cavity geometry increase the emission and absorption compared to a flat surface due to the cavity effect. In this paper, in order to obtain the directional emission of geometric surfaces (V-Grooves) using ray tracing and studying the propagation of light, a new algorithm is developed. The numerical simulations take into account the materials properties of both facets of the V-shape, thus simulating an original asymmetric and a multilayer V-shape and providing a very interesting directive thermal emission behavior. We evaluated the emission behavior from the reflection and emission coefficients of different rays at different angles for different parameters (materials properties, wavelength, and geometry). The simulations of a V-groove showed that due to the different reflections occurring inside an aluminum V-cavity with an aperture angle of 28°, the emissivity was well enhanced by 86% in the normal direction compared to a flat surface made of the same material. Moreover, using the original asymmetric opposite-sided materials (Al and Si) in a V- groove, it was possible to separate and control the emission by focusing the radiation or directing different spectral bands in different directions.

Two‐Magnon Non‐Locality and Coherence Induced by an Open Microwave Cavity: Generation and Robustness

The generation and robustness of two-magnon non-locality and coherence dynamics induced by an open microwave field cavity are investigated in this work. The studied system consists of a two-sublattice ferrimagnet coupled to a microwave field within an open cavity through its magnetic field component. The robustness of the two-magnons non-locality dynamics is analyzed using various non-locality and coherence measures (namely, uncertainty-induced non-locality [UIN], maximal Bell function, and log-negativity entanglement [L-NE]) in the presence of the spontaneous emission and the electromagnetic-wave dissipation. It is shown that photon-magnon couplings, two-magnon couplings, and dissipation all have an impact on the dynamical aspect of two-magnon non-locality and coherence. This work reveals that the two-magnon non-locality and coherence can be generated. For an initial maximal correlated two-magnon state, the initial UIN non-locality is shown to be more resilient than the maximum Bell function and log-negativity. The amplitudes of the two-magnon non-locality quantifiers decline as a result of the two-magnon coupling. The Bell non-locality and L-NE are reduced via spontaneous emission and dissipation, but the two-magnon UIN-coherence is preserved. These findings contribute to a better understanding of such dynamics and may shed light on measurement estimation in open quantum systems.

Cooperative-effect-induced one-way steering in open cavity magnonics

We propose to generate and control stationary one-way steering with strong entanglement between photon and magnon modes by the cooperative effect of coherent coupling and dissipative coupling. Due to the combination of two couplings, the system becomes a parity-time-like symmetric non-Hermitian system, and two exceptional points (EPs)-like appear in the real and imaginary parts of the eigenvalues. We demonstrate that the especially obvious quantum entanglement and perfect one-way steering can be obtained around two EPs-like. The continuous variable entanglement and steering produced by this cooperative effect show stronger robustness to environment temperature and system dissipation than that induced by nonlinearity. The one-way steering directivity can be controlled by the relative phase of cooperative dissipation and the frequency detuning of the magnon mode. Our work shows the controllability advantage of the open cavity magnonic system and may open up a platform for the generation of stationary one-way steering.

Evolution of vortex structures in an open deep cavity under pulsatile flow conditions: An experimental study

Experiments have been conducted to investigate the vortex dynamics in a deep open cavity driven by pulsatile flows. Physiological flow waveforms have been examined for mean Re ranging from 200 to 1000 and Wo of 10.2, 12.4, and 17.6, with Strouhal numbers (Str, as a function of Re and Wo) ranging from 0.065 to 0.98. Results show that a two-primary-vortex system develops, similar to a steady driven cavity flow, but it exhibits more dynamic behaviors as it evolves during a cycle. Five stages of vortex evolution are defined: generation, traveling, merging, stretching, and weakening. As Re increases, the first three stages occur faster and earlier in a cycle, allowing more time for the top primary vortex to interact with the rear wall and for the bottom vortex to develop. The opposite trend is found as Wo increases. While the flow strength increases with Re, the vortex patterns are more correlated with Str, which is proportional to the Wo square and inversely proportional to Re: vortices are symmetric at low Str, but become more distorted at high Str. A critical Str exists beyond which the bottom vortex would not develop inside the cavity. Results also suggest that an increasing Wo causes a more significant increase in the in-cavity vortex strength and flow unsteadiness compared to an increasing Re. The peak flow unsteadiness inside the cavity occurs at a later phase compared with that of the main flow. The normalized mass flux ratio and the normalized cavity kinetic energy are both linearly proportional to the Strouhal number.

Key for a Hidden Quantum State.

Quantum trajectories are crucial to understanding the evolution of open systems. We consider an open cavity mode undergoing up and down multistate quantum jumps due to the emission and absorption of photons. We prove that among all subtrajectories, starting simultaneously from different photon number states, only one survives a long single-run evolution. A random Fock state terminating the subtrajectory becomes known for the ergodic case via the key-the processed record of the input and output photocounts, and the trajectory duration. Based on this result, we propose a robust protocol to infer the Fock state, a valuable resource for quantum applications.

Q Factor Enhancement of Open 2D Resonators by Optimal Placement of a Thin Metallic Rod in Front of the Longitudinal Slot

A rigorous approach was employed for the accurate evaluation of the electromagnetic interaction between a thin metallic rod and a two-dimensional (2D) slotted cavity. The problem was posed as a classical boundary value problem for the Helmholtz equation in which a 2D slotted open cavity is bounded by an arbitrary but otherwise smooth contour with a longitudinal slit. Using the method of analytical regularization, the problem was transformed to well-conditioned coupled infinite systems of linear algebraic equations for the Fourier coefficients in the expansions of induced surface currents on the rod and slotted cavity. When truncated to finite size, their solutions exhibit fast convergence to the exact solution as the order is increased. This feature makes it possible to investigate the spectral and scattering characteristics of the coupled cavity and rod to within any desired accuracy. In this paper, the complex eigenvalues for a slotted cavity in the presence of a thin rod and the dependence upon their relative location were investigated, particularly to find where there is significant or optimal enhancement of the Q factor. Such optimisation may be exploited in the design of advanced slot antennas and slotted waveguides.

Role of Symmetry Breaking in Observing Strong Molecule-Cavity Coupling Using Dielectric Microspheres.

The emergence of dielectric open optical cavities has opened a new research avenue in nanophotonics. In particular, dielectric microspheres support a rich set of cavity modes with varying spectral characteristics, making them an ideal platform to study molecule–cavity interactions. The symmetry of the structure plays a critical role in the outcoupling of these modes and, hence, the perceived molecule–cavity coupling strength. Here, we experimentally and theoretically study molecule–cavity coupling mediated by the Mie scattering modes of a dielectric microsphere placed on a glass substrate and excited with far-field illumination, from which we collect scattering signatures both in the air and glass sides. Glass-side collection reveals clear signatures of strong molecule–cavity coupling (coupling strength 2g = 74 meV), in contrast to the air-side scattering signal. Rigorous electromagnetic modeling allows us to understand molecule–cavity coupling and unravel the role played by the spatial mode profile in the observed coupling strength.

Magnetohydrodynamic (MHD) Convective Nanofluid Flow, Heat Transfer and Irreversibility Analysis in a Horizontal Micro Tall Cavity with Heat Sources in the Slip Regime

The contemporary study aims to numerically analyze the MHD convective heat transfer and entropy generation analysis for the case of a micro open tall cavity filled with Al2O3/water under the effect of uniform magnetic field in the slip flow regime using the LBM for resolving the governing equations. The slip velocity and the temperature jump conditions are used to incorporate the micro aspect. The Brownian motion effects are considered in the thermal conductivity. The flow pattern and heat transfer characteristics and the irreversibility are studied dependently on various dimensionless independent variables such as: nanoparticles volume fractionΦ(0–4%), Rayleigh number (Ra) (102–104), Knudsen number (Kn) (0–10−1) and Hartmann number (Ha) (0–75). It is found that the change of aspect ratio, Ra,Φand the magnetic field strength affect the hydrodynamic and thermal behaviors inside the micro medium. Concerning the Kn, which presents the most influential parameter on the heat transfer, flow pattern, thermal field and entropy generation, it was concluded it decreases the heat transfer, entropy generation and Bejan number inside the micro tall open cavity. Moreover, it deteriorates the formed rolling cells and the plumes in the micro domain. The nanoparticles size effect is also studied, and found to reduce the heat transfer.

Microsphere Coupled Off-Core Fiber Sensor for Ultrasound Sensing.

A compact fiber ultrasound-sensing device comprising a commercially available Barium Titanate (BaTiO3) glass microsphere coupled to an open cavity off-core Fabry–Perot interferometer (FPI) fiber sensor is proposed and demonstrated. The open cavity is fabricated through splicing two segments of a single mode fiber (SMF-28) at lateral offsets. The lateral offset is matched to the radius of the microsphere to maximize their coupling and allow for an increased sensing response. Furthermore, the microsphere can be moved along the open-air cavity to allow for tuning of the reflection spectrum. The multiple passes of the FPI enabled by the high refractive index microsphere results in a 40 dB enhancement of finesse and achieves broadband ultrasound sensing from 0.1–45.6 MHz driven via a piezoelectric transducer (PZT) centered at 3.7 MHz. The goal is to achieve frequency detection in the MHz range using a repeatable, cost effective, and easy to fabricate FPI sensor design.

Ultrasensitive cascaded in-line Fabry-Perot refractometers based on a C-shaped fiber and the Vernier effect.

We propose and experimentally demonstrate a fiber refractometer based on a C-shaped fiber and the Vernier effect. The sensor is fabricated by cascading a single mode fiber (SMF) pigtail together with a C-shaped fiber segment and another SMF segment. Thus, the C-shaped fiber would constitute an open cavity (sensing cavity) in which test analytes could be filled, while the SMF segment would constitute another reference cavity. Due to the similar optical path length of these two cavities, the Vernier effect would be activated, thus forming spectral envelops in the reflection spectrum of the sensor. Variations in the refractive index (RI) of analytes would result in the shifts of the spectral envelops. Both theoretical calculations and experiments are carried out in the characterization of the sensor measuring liquid and gaseous analytes. The experimental sensitivity of the sensor is found to be ∼37238 nm/RIU for gas RI measurement. The proposed sensor features the advantages such as ease of fabrication, extremely high sensitivity, capability of sensing of both gaseous and liquid analytes, small footprint, and good mechanical strength. Compared to other existing Vernier effect-based fiber refractometers typically fabricated using PCFs, the proposed sensor would allow analytes to have much easier and quicker access to the sensor probe.

Analysis of melting of phase change material block inserted to an open cavity

A numerical work has been conducted to explore the effects of opening parameters on melting of phase change material (PCM) during natural convection in a partially open enclosure. A finned heater is located on bottom wall while the remaining parts are insulated. Paraffin wax is used as PCM and two-dimensional time dependent analysis is performed by using the finite volume method for the parameters of location of opening and temperature difference. The governing parameters for the study are chosen for the range of Ra = 1.45 × 108 ≤ Ra ≤ Ra = 1.97 × 108, 0.25 ≤ w/H ≤ 0.75 and 0.25 ≤ c/H ≤ 0.75. It is found that both opening ratio and opening length are effective parameter on melting time and these can be used as control parameters for improving the energy efficiency. Also, heat transfer can be controlled by using PCM inserted block and opening parameters. Among different cases of opening ratios and locations of opening, the most favorable configuration is obtained at Ra = 1.97 × 108, w/H = 0.25, c/H = 0.25 while average heat transfer enhancement by about 60% is achieved. At the lowest and highest value of Rayleigh numbers, the most favorable location of the opening is obtained at c/H = 0.25 in order to have the highest reduction amount of phase completion time.