Neighboring Cavities Research Articles

Multiplex vortex instability in the flow of non-Newtonian fluids through microcavity arrays

Complex fluids always possess obvious non-Newtonian properties that facilitate the occurrence and development of vortex instability in porous media, which is of critical significance in many natural and industrial processes. It is widely known that this flow instability is regulated by both fluid flow and solid structure. However, the quantitative understanding of how structural characteristics of porous space affect the evolution of vortex instability is still nascent, especially in the case of fluids with varying rheological properties. Herein, the flow of polymer solutions with distinct non-Newtonian properties through microcavity arrays is experimentally studied, by which we systematically explore the effect of structural parameters of the cavity array on vortex instability. We find that, for both Newtonian and shear-thinning fluids with negligible elasticity, the vortex evolution behavior in each cavity of the cavity array is identical to those in an isolated cavity. In contrast, for viscoelastic fluids, the vortex instability is visibly affected by cavity number and cavity–cavity interval, and this effect exhibits different forms when the fluid shear-thinning participates or not. Multiplex vortex instabilities are observed under these tested conditions. By multiplex, we mean the vortex formation dynamics and evolution patterns are diversified. These unusual evolution phenomena are then interpreted in terms of the interplay between the elongation and relaxation of polymers as they navigate among neighboring cavities. These results can help us to further understand the flow instability of complex fluids in porous media and evoke new strategies for microfluidic applications of efficient mixing.

Stratification Breakdown in Antarctic Coastal Polynyas. Part I: Influence of Physical Factors on the Destratification Time Scale

Abstract This study examines the process of water-column stratification breakdown in Antarctic coastal polynyas adjacent to an ice shelf with a cavity underneath. This first part of a two-part sequence seeks to quantify the influence of offshore katabatic winds, alongshore winds, air temperature, and initial ambient stratification on the time scales of polynya destratification through combining process-oriented numerical simulations and analytical scaling. In particular, the often-neglected influence of wind-driven circulation on the lateral transport of the water formed at the polynya surface—which we call Polynya Source Water (PSW)—is systematically examined here. First, an ice shelf–sea ice–ocean coupled numerical model is adapted to simulate the process of PSW formation in polynyas of various configurations. The simulations highlight that (i) before reaching the bottom, majority of the PSW is actually carried away from the polynya by katabatic wind–induced offshore outflow, diminishing water-column mixing in the polynya and intrusion of the PSW into the neighboring ice shelf cavity, and (ii) alongshore coastal easterly winds, through inducing onshore Ekman transport, reduce offshore loss of the PSW and enhance polynya mixing and PSW intrusion into the cavity. Second, an analytical scaling of the destratification time scale is derived based on fundamental physical principles to quantitatively synthesize the influence of the physical factors, which is then verified by independent numerical sensitivity simulations. This work provides insights into the mechanisms that drive temporal and cross-polynya variations in stratification and PSW formation in Antarctic coastal polynyas, and establishes a framework for studying differences among the polynyas in the ocean.

Stress solution for an arbitrarily shaped tunnel with a neighboring circular cavity

This paper gives an analytical stress solution for the plane strain problem that the deep rock mass contains an arbitrarily shaped tunnel and a circular cavity subjected to in situ stresses. Based on the discovery that the mapping function for an arbitrarily shaped hole can also manage a tunnel and a circular hole mapping into two circles, the plate bounded by the two holes is conformally mapped onto an annulus. The complex variable method is used to establish the stress boundary condition, and then the two analytical functions are solved by the power series method. Comparison with ANSYS solution is made to validate the correctness of deductions and solving process. To consider practical underground engineering, the cases of different lateral stresses, distances of the two holes, sizes, and positions of the cavity are discussed.

Generation of multiple entangled fields via mechanical oscillator displacement

We present a convenient and efficient scheme to generate arbitrarily multipartite continuous-variable entanglement via mechanical oscillator displacement induced by two strong input pump fields in the conventional single-cavity optomechanical system. It is shown that multipartite entanglement among the outputs of the two pump fields and any number of relatively weak probe fields can be realized and optimized when the two pump fields with suitable amplitude ratio and relative initial phase are, respectively, tuned to the red and blue mechanical sidebands of a single cavity mode and each probe field is red-detuned by the mechanical frequency with respect to a different neighboring cavity mode. This method can, in principle, be extended to flexibly and conveniently generate arbitrarily multiple nondegenerate bright entangled fields by using only coherent laser fields, and may find promising applications in realistic quantum communication and networks.

Effect of top and bottom blowing conditions on spitting in converter

AbstractThe effect of top blowing and bottom blowing conditions on spitting behavior was investigated by water model experiments and numerical calculation. The results of the water model experiment showed that reducing the jet velocity by using a larger nozzle diameter was effective for reducing spitting. The numerical calculation indicated that interference between the top blown gas jet and the bottom blowing plume increases the gas velocity at the rim of the cavity, causing heavier spitting. A new index using the geometrical locations of the neighboring cavity and plume was proposed. The spitting rate decreased under conditions with lower interference by avoiding interaction between the top blown gas jet and the bottom blowing plume. The energy distribution in the blowing process was discussed based on a water model experiment using bath mixing time, bath vibration, and the spitting rate. The energy for spitting was explained convincingly by the difference between the energy input and the energy of bath vibration, cavity formation, and bath mixing. The results implied lower interference of the top and bottom gas resulted in lower energy for spitting generation.

Electron generation and multiplication at the initial stage of nanosecond breakdown in water

Electrical breakdown of liquid dielectrics under nanosecond pulsed high voltage has been investigated extensively in the last decade. Prior studies have focused on either experimental characterization of the breakdown process and discharge plasma or formulation/verification of the electrostrictive cavitation mechanism of the breakdown initiation. There remain knowledge gaps toward a clear physical picture of how the first plasma is generated in a region saturated by nanoscale cavities created by electrostrictive forces in inhomogeneous fields at the nanosecond timescale. Initial plasma results from the multiplication of primary electrons that gain energy collisionlessly in the cavities to cause collisional ionization of water molecules on the cavity walls. This paper quantitatively discusses the possible sources of primary electrons that seed the plasma discharge. Electron detachment from hydroxide is shown to be the most probable and sustainable electron source. Using numerical modeling, this study demonstrates the plausibility of an electron multiplication mechanism involving two neighboring cavities. The drift of hydrated electrons from one cavity to the next is the rate-limiting step and sets the minimum electric field requirement. This work will inform subsequent experimental studies and have implications in various applications such as plasma sources in biomedical applications, cavitation study, and insulation of pulsed power equipment.

Superradiance, bosonic Peierls distortion, and lattice gauge theory in a generalized Rabi-Hubbard chain

We investigate a one-dimensional Rabi-Hubbard type of model, arranged such that a qdot is sandwiched between every cavity. The role of the qdot is to transmit photons between neighboring cavities, while simultaneously acting as a photon non-linearity. We consider three-level qdots in the $\Lambda$ configuration, where the left and right leg couples exclusively to the left or right cavity. This non-commuting interaction leads to two highly entangled incompressible phases, separated by a second order quantum phase transition: the qdot degrees-of-freedom act as a dynamical lattice for the photons and a Peierls instability breaks a second $\mathbb{Z}_2$ symmetry which leads to a dimerization in entanglement and photon number. We also find a normal insulating phase and a superfluid phase that acts as a quantum many-body superradiant phase. In the superradiant phase, a $\mathbb{Z}_2$ symmetry is broken and the phase transition falls within the transverse field Ising model universality class. Finally, we show that a limit of the model can be interpreted as a $\mathbb{Z}_2$ lattice gauge theory.

PANCREATICO-PLEURAL FISTULA AND SUBSEQUENT FUNGAL EMPYEMA

SESSION TITLE: Medical Student/Resident Chest Infections Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: A rare pancreatitis complication is pancreatico-pleural fistula with empyema development being even more scarce. CASE PRESENTATION: A 48-year-old male with a history of alcoholic pancreatitis, subsequent mediastinitis with recurrent pleural effusions and pneumonia presented to the outpatient pulmonology office for persistent dyspnea. We ordered basic labs, showing significant leukocytosis and anemia, and a thoracentesis, removing 600 milliliters. Upon transferring to the hospital, further workup revealed elevated lipase and C-reactive protein. Pleural fluid studies indicated an amylase-rich exudative process. Chest-x ray showed bilateral pleural effusions and multilobar pneumonia. Computed Tomography (CT) Angiography of chest showed loculated moderate right and small left pleural effusion, multilobar pneumonia especially in lower lobes. CT of abdomen/pelvis showed acute pancreatitis and pancreatic cystic lesions in the head and uncinate process. We initiated broad coverage with Vancomycin, Cefepime, and Metronidazole. On day 3 of admission, a chest tube was placed and 6 doses of lytic therapy were administered. Endoscopic Retrograde Cholangio-Pancreatography (ERCP) was performed and confirmed pancreatico-pleural fistula (PPF). Thus, sphincterotomy was performed and a stent was placed; however, the pancreatic duct could not be cannulated. Video-Assisted Thoracoscopic Surgery was not indicated at this time. Pleural fluid cultures grew Candida Albicans and Micafungin was added. Upon receiving sensitivities, we discontinued the current regimen and started Fluconazole. Chest tube was removed on day 10 of admission. The patient was discharged home with instructions to continue Fluconazole for 6 weeks, weekly lab monitoring, repeat ERCP with pancreatic duct cannulation in 3 weeks, and repeat Chest x-ray in 2 months. DISCUSSION: PPF with pleural effusion is reported with an incidence of 0.4%. A pancreatic duct disruption causes persistent leakage of pancreatic secretions. Initially, a fluid collection forms, known as a pseudocyst. Eventually, the secretions can cause a spontaneous erosion into a neighboring organ or cavity, the pleural cavity in our case. Patients with PPF present similarly to pleural effusions, as they are recurrent and refractory to repeated thoracentesis. 1 In rare cases, an empyema can develop that can cause life-threatening sepsis. 2 Classical PPF patients are middle-aged men, chronic pancreatitis from alcoholism, dyspneic, no acute abdominal symptoms, left pleural effusions, pseudocyst on CT, and elevated pleural fluid amylase, lipase, and albumin. These were observed in our case, except bilateral pleural effusions, which has a 19% incidence compared to 74% for left sided. 1 CONCLUSIONS: As clinicians, we should consider the rare complications of PPF in the differential for patients with a history of pancreatitis presenting for dyspnea and sepsis. Reference #1: Machado, NO. Pancreaticopleural Fistula: Revisited. Diagnostic and Therapeutic Endoscopy. 2011;2012:1-5. Reference #2: Kim E, Ahn HY, Kim YD, Hoseok, Cho JS. Successful Diagnosis and Treatment of a Pancreaticopleural Fistula in a Patient Presenting with Unusual Empyema and Hemoptysis. Korean J Thorac Cardiovasc Surg. 2019;52(3):174-177. doi: 10.5090/kjtcs.2019.52.3.174. DISCLOSURES: No relevant relationships by Jacob Burch, source=Web Response No relevant relationships by James Choi, source=Web Response No relevant relationships by Rakesh Gami, source=Web Response No relevant relationships by Tyler Kemnic, source=Web Response No relevant relationships by Jason Liu Liu, source=Web Response No relevant relationships by Rohan Prasad, source=Web Response No relevant relationships by Fazal Raziq, source=Web Response No relevant relationships by Eric Smith, source=Web Response

Generation of the bipartite entanglement and correlations in an optomechanical array

In this paper, we study the remote bipartite entanglement and correlations between the neighboring cavity and movable mirror using an optomechanical array, in which the optical cavities are coupled to one oscillating end-mirror through a photon hopping process. Under the linearization approximation, the stationary bipartite continuous-variable entanglement and quantum correlations are quantified through logarithmic negativity and correlation functions of two non-Hermitian operators, respectively. Remarkably, our numerical simulation exhibits a generation of bipartite correlation behavior between cavity–oscillating mirror and cavity–cavity subsystems through the applicable choice of optical cavity detunings and photon hopping coupling strength. The system also offers the possibility of remote bipartite entanglement with the neighboring cavity and movable mirror. We further show that the amount of quantum correlation between subsystems can be achieved for small photon hopping coupling strengths and small effective temperatures. It is found that the generation of bipartite quantum correlations between the cavity mode and oscillating mirror can be transferred entirely through photon hopping coupling strength. Our results may have potential applications for the realization of optomechanical crystals platform and continuous-variable quantum information interfaces.

Experimental investigation of ventilated partial cavitation

This study presents the experimental investigation on the cavity regime and the corresponding geometric characteristic of ventilated partial cavitation (VPC). Experiments are conducted in the high-speed water tunnel at Saint Anthony Falls Laboratory. A backward-facing cavitator mounted on the ceiling of test section is used to generate the VPC. The flow filed and the dynamic motion of VPC are captured by the imaging system under varying water speeds and ventilation rates. Four distinct cavity regimes are classified, referred to as foamy cavity (FC), transition cavity (TC), open cavity (OC) and two-branch cavity (TBC). The distribution of these cavity regimes over Froude number (Fr) and ventilation coefficient (CQs) is summarized in a regime map with FC and TBC occupying the majority portion of the map. More importantly, the CQs−Fr curves demarcating neighboring cavity regimes are revealed satisfying a clear linear relation for FC–TC and a quadratic relation for TC–OC and OC–TBC when Fr is subtracted with a constant corresponding to the inception condition of the cavity regime. Such trends are attributed to the two gas entrainment mechanisms present in VPC, referred to as recirculating vortex entrainment and cavity closure entrainment. Moreover, the geometric characteristic of VPC characterized by the cavity length is examined. With increasing ventilation at fixed Fr, the cavity length grows linearly in OC regime and remains unchanged in TBC regime. The maximum cavity length of OC is found to be within around 7 times of cavitator height. With increasing Fr at fixed ventilation, the cavity length first grows proportional to Fr2 in TBC regime but drops sharply with a small increase of Fr when the cavity transitions from TBC to OC. At fixed Fr, the cavity underpressure rises to maximum (minimum σC) and stays unchanged in TBC upon increasing ventilation. As a result, in TBC, the cavity length is shown to satisfy a power law relation with respect to Fr or σC, while in OC, the cavity length is influenced by the interplay among CQs, σC and Fr with no clear trend observed.

Cavitation in a liquid-filled cavity surrounded by an elastic medium: Intercoupling of cavitation events in neighboring cavities.

The subject of the present theoretical study is the dynamics of a cavitation bubble in a spherical liquid-filled cavity surrounded by an infinite elastic solid. Two objectives are pursued. The first is to derive equations for the velocity and pressure fields throughout the liquid filling the cavity and equations for the stress and strain fields throughout the solid medium surrounding the cavity. This derivation is based on the results of our previous paper [A. A. Doinikov etal., Phys. Rev. E 97, 013108 (2018)10.1103/PhysRevE.97.013108], where equations for the evolution of a bubble inside a cavity were derived. The second objective is to apply the equations obtained at the first step of the study to ascertain if the cavitation process in one cavity can trigger the nucleation in a neighboring cavity. To this end, we consider a neighboring cavity in which a cavitation bubble is absent. We derive equations that describe the disturbance of the liquid pressure inside the second cavity, assuming this disturbance to be caused by the cavitation process in the first cavity. The developed theory is then used to perform numerical simulations. The results of the simulations show that the magnitude of the background negative pressure inside the second cavity increases at the second half period of the pressure disturbance, which in turn enhances the probability of nucleation in the second cavity.

Theoretical Modeling and Optimization of Porous Coating for Hypersonic Laminar Flow Control

A theoretical model is developed to describe the acoustic characteristics of plane ultrasonic acoustic waves impinging on a porous coating, namely, a rigid surface periodically corrugated with subwavelength grooves (two-dimensional cavities). The proposed model takes into account the high-order diffracted modes, and therefore incorporates mutual coupling among neighboring cavities. The model predicts a reflection frequency consistent with the numerical results and reproduces a coupling mode induced by interactions between waves scattered from adjacent cavities. With this model, the cavity geometry parameters are optimized to achieve the minimum reflection coefficient. The result shows that the Mack second mode is strongly suppressed and that the maximum fluctuating pressure decreases by about 88% upon using the optimized porous coating in a Mach 6 flat-plate flow.

Bound state in the continuum by spatially separated ensembles of atoms in a coupled-cavity array

We present an analytic solution of bound states in the continuum (BICs) for photons and atoms in a one-dimensional coupled cavity array. These bound states are formed by two ensembles of twolevel atoms confined in separated cavities of the array. We show that in the regime where the photon hopping rate between neighboring cavities is high compared with the collective Rabi frequency, the BIC corresponds to a subradiant collective atomic state in which the two ensembles of atoms are strongly entangled. On the other hand in the low photon hopping rate regime, the BIC behaves a quantum cavity in which photons can be trapped between the two ensemble of atoms.

Crossover Jet Impingement in a Rib-Roughened Trailing-Edge Cooling Channel

Airfoil trailing-edge cooling is the main focus of this study. The test section was made up of two adjacent trapezoidal channels, simulating the trailing-edge cooling cavity of a gas turbine airfoil and its neighboring cavity. Eleven racetrack-shaped holes were drilled on the partition wall between the two channels to produce 11 cross-over jets that impinged on the rib-roughened wall of the trailing-edge channel. The jets, after impinging on their respective target surface, turned toward the trailing-edge channel exit. Smooth target wall, as a baseline case, as well as four rib angles with the flow of 0 deg, 45 deg, 90 deg, and 135 deg are investigated. Cross-over holes axes were on the trailing-edge channel center plane, i.e., no tilting of the cross-over jets. Steady-state liquid crystal thermography technique was used in this study for a range of jet Reynolds number of 10,000–35,000. The test results are compared with the numerical results obtained from the Reynolds-averaged Navier–Stokes and energy equation. Closure was attained by k–ω with shear stress transport (SST) turbulence model. The entire test rig (supply and trailing-edge channels) was meshed with variable density hexagonal meshes. The numerical work was performed for boundary conditions identical to those of the tests. In addition to the impingement heat transfer coefficients, the numerical results provided the mass flow rates through individual cross-over holes. This study concluded that: (a) the local Nusselt numbers correlate well with the local jet Reynolds numbers, (b) 90 deg rib arrangement, that is, when the cross-over jet axis was parallel to the rib longitudinal axis, produced higher heat transfer coefficients, compared to other rib angles, and (c) numerical heat transfer results were generally in good agreement with the test results. The overall difference between the computational fluid dynamics (CFD) and test results was about 10%.

Comparison of the molecular interactions of 7′-carboxyalkyl apigenin derivatives with S. cerevisiae α-glucosidase

As one of the most investigated flavonoids, apigenin, is considered to be a strong α-glucosidase inhibitor. However, the clinical utility of apigenin is limited due to its low solubility. It was reported that the solubility and biological activity can be improved by introducing sole carboxyalkyl group into apigenin, especially the 7′-substitution. With the increase of length of the alkyl chain in carboxyalkyl group, B ring of the apigenin derivative is embedded much more deeply into the binding cavity while the carboxyalkyl stretches to the neighboring cavity. All of the terminal carboxyl groups form hydrogen bonding interactions easily with the surrounding polar amino acids, such as His239, Ser244, Arg312 and Asp349. Thus, the electron density values of the carbonyl in the carboxyl group become higher than the solution status due to the strong molecular interactions. In fact, electron densities of most of the chemical bonds are decreased after molecular docking procedure. On compared with the solution phase, however, dipole moments of most of these molecules are increased, and their vectors are reoriented distinctly in the active sites. It is noticed that all of the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) are distributed throughout the whole parent apigenin ring in solution phase, whereas the disappeared situation happened on the B rings of some molecules (II–IV) in the active site, leading to higher energy gaps.

Kerr optical frequency combs: theory, applications and perspectives

Abstract The optical frequency comb technology is one of the most important breakthrough in photonics in recent years. This concept has revolutionized the science of ultra-stable lightwave and microwave signal generation. These combs were originally generated using ultrafast mode-locked lasers, but in the past decade, a simple and elegant alternativewas proposed,which consisted in pumping an ultra-high-Q optical resonator with Kerr nonlinearity using a continuous-wave laser. When optimal conditions are met, the intracavity pump photons are redistributed via four-wave mixing to the neighboring cavity modes, thereby creating the so-called Kerr optical frequency comb. Beyond being energy-efficient, conceptually simple, and structurally robust, Kerr comb generators are very compact devices (millimetric down to micrometric size) which can be integrated on a chip. They are, therefore, considered as very promising candidates to replace femtosecond mode-locked lasers for the generation of broadband and coherent optical frequency combs in the spectral domain, or equivalently, narrow optical pulses in the temporal domain. These combs are, moreover, expected to provide breakthroughs in many technological areas, such as integrated photonics, metrology, optical telecommunications, and aerospace engineering. The purpose of this review article is to present a comprehensive survey of the topic of Kerr optical frequency combs.We provide an overview of the main theoretical and experimental results that have been obtained so far. We also highlight the potential of Kerr combs for current or prospective applications, and discuss as well some of the open challenges that are to be met at the fundamental and applied level.

Sound absorption behavior of flexible polyurethane foams with distinct cellular structures

The effect of cellular structure in the flexible polyurethane foams on the sound absorption behavior is investigated for improved sound environment within vehicles. Two types of gelling catalyst and water are used for producing well-defined cavity and pore structure in the foams. The catalyst, having high activity in urethane reaction, produces a larger number of small cavities and pores in the foams compared to the catalyst having low activity. A high number of small cavities can also be obtained at high water content from the restraint of neighboring cavities due to actively formed urethane matrix. The foam density decreases with increasing water and catalyst contents. Sound absorption efficiency is usually low at low foam density, but the results show improved sound absorption efficiency even at the reduced foam density because of the high number of well dispersed small cells in the foams.

Ultra-compact metamaterial absorber for multiband light absorption at mid-infrared frequencies

We investigated a multiband metamaterial absorber composed of one-side open cavities. A metallic sidewall effectively prevents destructive coupling between the neighboring cavities. Thus, the number of subunits in one period, which determines the number of multibands or the width of broadband, can be greatly increased. A redshift effect of the resonances is observed theoretically and numerically when the distance between the subunits is reduced. Although the separation is very small and the coupling between the neighboring cavities is strong, the angular insensitivity of the absorption is well-maintained over a wide range. Our findings may enable applications of ultra-compact multiband sensors and thermal emitters.

Local compensation–rematch for major element failures in superconducting linacs with very high reliability and low beam loss

In order to achieve the extremely high reliability and availability in superconducting linacs required by some applications such as in accelerator-driven systems (ADS), a fault tolerance design is usually pursued. With the example of the China-ADS main linac, the failure effects of key elements such as RF cavities and focusing elements in different locations along the linac have been studied and the schemes of compensation by means of the local compensation–rematch method have been proposed. For cavity failures, by adjusting the settings of the neighboring cavities and focusing elements one can make sure that the Twiss parameters and beam energy are recovered to the nominal ones at the matching point. For solenoid failures in the low energy section, a novel method by using a neighbor cavity with reverse phase is used to maintain simultaneous acceleration and focusing in both the transverse and longitudinal phase planes. For quadrupole failures in the warm transitions in the high energy section, triplet focusing structure is adopted which can be converted locally into a doublet focusing in case of one quadrupole failure and the rematch method is proven very effective. With macro-particle simulations by TraceWin, it is found that the normalized rms emittance has no obvious growth and the halo emittance has modest growth after applying the local compensation–rematch in the cases mentioned above. In addition, a self-made code based on MATLAB has been developed to double check the simulations by TraceWin for the local compensation and rematch method.

Phase diagram of a QED-cavity array coupled via a N-type level scheme

We study the zero-temperature phase diagram of a one-dimensional array of QED cavities where, besides the single-photon hopping, an additional coupling between neighboring cavities is mediated by an N-type four-level system. By varying the relative strength of the various couplings, the array is shown to exhibit a variety of quantum phases including a polaritonic Mott insulator, a density-wave and a superfluid phase. Our results have been obtained by means of numerical density-matrix renormalization group calculations. The phase diagram was obtained by analyzing the energy gaps for the polaritons, as well as through a study of two-point correlation functions.