Wave Condensation Research Articles

Computational modeling of non-equilibrium condensing steam flows in low-pressure steam turbines

Abstract Condensation occurring in low pressure stages of steam turbines contributes to many losses in efficiency and damage to the stator blades such as corrosion and pitting. This problem has been observed profusely in power generation industries. The purpose of this study is to properly simulate the condensation and shock wave phenomenon at the last stage of the steam turbine and accordingly understand this phenomenon. Numerical simulation was conducted by using ANSYS Fluent and applying k-omega SST turbulence model. The results agreed with the experimental values.

Wave condensation with weak disorder versus beam self-cleaning in multimode fibers

Classical nonlinear random waves can exhibit a process of condensation. It originates in the singularity of the Rayleigh-Jeans equilibrium distribution and it is characterized by the macroscopic population of the fundamental mode of the system. Several recent experiments revealed a phenomenon of spatial beam cleaning of an optical field that propagates through a graded-index multimode optical fiber (MMF). Our aim in this article is to provide physical insight into the mechanism underlying optical beam self-cleaning through the analysis of wave condensation in the presence of structural disorder inherent to MMFs. We consider experiments of beam cleaning where long pulses are injected in the and populate many modes of a 10-20 m MMF, for which the dominant contribution of disorder originates from polarization random fluctuations (weak disorder). On the basis of the wave turbulence theory, we derive nonequilibrium kinetic equations describing the random waves in a regime where disorder dominates nonlinear effects. The theory reveals that the presence of a conservative weak disorder introduces an effective dissipation in the system, which is shown to inhibit wave condensation in the usual continuous wave turbulence approach. On the other hand, the experiments of beam cleaning are described by a discrete wave turbulence approach, where the effective dissipation induced by disorder modifies the regularization of wave resonances, which leads to an acceleration of condensation that can explain the effect of beam self-cleaning. The simulations are in quantitative agreement with the theory. The analysis also reveals that the effect of beam cleaning is characterized by a repolarization as a natural consequence of the condensation process. In addition, the discrete wave turbulence approach explains why optical beam self-cleaning has not been observed in step-index multimode fibers.

Formation and mass growth of axion stars in axion miniclusters

We study the formation and the subsequent mass growth of axion stars inside axion miniclusters. Numerically solving the Schr\"odinger-Poisson equations with realistic initial conditions we find that the axion stars exhibit similar properties to solitonic cores in ultralight bosonic dark matter halos in terms of their radial density profiles and large-amplitude oscillations. A merger of two axion stars confirms a previously found empirical law for the mass of the merged axion star. Monitoring the axion star masses over time, we observe a mass growth consistent with the mass increase of Bose stars in the kinetic regime reported by Levkov et al., confirming that the mass evolution of axion stars can be understood in terms of wave condensation. Based on this result, we predict a saturation of mass growth in relation to the minicluster mass consistent with the core-halo mass relation previously found for ultra-light bosonic dark matter halos.

Density wave states in the presence of an external magnetic field

We investigate the effect that density-wave states have on the Hofstadter Butterfly. We first review the problem of the $d$-density wave on a square lattice and then numerically solve the $d$-density wave problem when an external magnetic field is introduced. As the $d$-density wave condensation strength is tuned the spectrum evolves through three topologically distinct butterflies, and an unusual quantum Hall effect is observed. The chiral $p+ip$-density wave state demonstrates drastically different Hofstadter physics--inducing a destruction of the gaps in the butterfly which causes electrons' cyclotron orbits to not obey any type of Landau quantization, and the creation of a large gap in the spectrum with Hall conductance $\sigma_{xy}$=0. To investigate the quantum phases in the system we perform a multifractal analysis of the single particle wavefunctions. We find that tuning the $d$-density wave strength at a generic value of magnetic flux controls a metal-metal transition at charge neutrality where the wavefunction multifractality occurs near band touching events. In the $p+ip$ case we observe another metal-metal transition near a band touching event which is seperated by a quasi-insulating island state occuring at charge neutrality near strip dimerization of the lattice.

Effectiveness of Gutta-percha/Sealer Removal during Retreatment of Extracted Human Molars Using the GentleWave System

IntroductionThe goal of endodontic retreatment is to address the etiology responsible for failure. In order to achieve this, the contents of the previous treatment must be removed. The aim of this study was to compare the effectiveness of the removal of residual obturation material (gutta-percha and sealer) using side-vented needle, EndoVac, and GentleWave (Sonendo, Inc, Laguna Hills, CA) irrigation protocols. MethodsThirty freshly extracted mandibular molars were instrumented to a master apical file size of 20.06, obturated using continuous wave of condensation and AH Plus sealer (Dentsply Tulsa, Tulsa, OK), restored, and placed in phosphate-buffered saline for 7 days. Teeth were retreated using a crown-down method to a master apical file size of 20.04. Radiographs and micro–computed tomographic images were obtained to confirm the presence of residual obturation material. Teeth were randomly divided among the following treatment groups: a side-vented needle, EndoVac, or GentleWave. Following strict irrigation protocols, postirrigation micro–computed tomographic scans were obtained and used to calculate the percentage of the residual obturation removed. ResultsGentleWave removed more residual obturation material (26%) than the side-vented needle (16%) and EndoVac (9%); the differences between the GentleWave group and the other 2 groups were not statistically significant (P > .05). The difference between the side-vented needle and EndoVac was statistically significant (P = .04). ConclusionsNone of the irrigation techniques were able to completely remove all of the residual obturation material from the canals. The side-vented needle and the GentleWave groups were able to remove on average more residual obturation material than EndoVac; however, the differences were not significant.

Dramatic Acceleration of Wave Condensation Mediated by Disorder in Multimode Fibers.

Classical nonlinear waves exhibit a phenomenon of condensation that results from the natural irreversible process of thermalization, in analogy with the quantum Bose-Einstein condensation. Wave condensation originates in the divergence of the thermodynamic equilibrium Rayleigh-Jeans distribution, which is responsible for the macroscopic population of the fundamental mode of the system. However, achieving complete thermalization and condensation of incoherent waves through nonlinear optical propagation is known to require prohibitive large interaction lengths. Here, we derive a discrete kinetic equation describing the nonequilibrium evolution of the random wave in the presence of a structural disorder of the medium. Our theory reveals that a weak disorder accelerates the rate of thermalization and condensation by several order of magnitudes. Such a counterintuitive dramatic acceleration of condensation can provide a natural explanation for the recently discovered phenomenon of optical beam self-cleaning. Our experiments in multimode optical fibers report the observation of the transition from an incoherent thermal distribution to wave condensation, with a condensate fraction of up to 60% in the fundamental mode of the waveguide trapping potential.

Hydrodynamic 2D Turbulence and Spatial Beam Condensation in Multimode Optical Fibers.

We show that Kerr beam self-cleaning results from parametric mode mixing instabilities that generate a number of nonlinearly interacting modes with randomized phases-optical wave turbulence, followed by a direct and inverse cascade towards high mode numbers and condensation into the fundamental mode, respectively. This optical self-organization effect is an analogue to wave condensation that is well known in hydrodynamic 2D turbulence.

Micro-computed tomographic analysis of filling porosity of two different obturation techniques

Introduction: The ideal root filling material should have inert properties, good adhesive ability, and result in void-free obturation along the root canals. The aim of this in vitro study was to compare the quality of two root canal obturation techniques; cold lateral (CL) condensation and continuous wave (CW) condensation, through measuring the volume of gaps and voids by using micro-computed tomography (micro-CT). Materials and Methods: Forty-extracted teeth with single canal were instrumented with profile rotary files, and divided into two groups as follows: CL condensation (n = 20), and CW obturation (n = 20). The teeth in each obturation group were scanned twice using micro-CT scan. The resultant images were rendered in proprietary software (NRecon version 1.6.9.4) to obtain three-dimensional (3D) pre- and post-obturation records of each specimen. The 3D images were imported into CT Analyser version 1.17.7.2 for volume measurement of voids and gaps in the apical third at 1 mm, 3 mm, and 5 mm. The analysis of variance test was used to compare the mean volume of voids and gaps between the two obturation groups in each level in the apical third (1 mm, 3 mm, and 5 mm). Furthermore, it was used to compare the mean volume of voids and gaps between the three different levels apically in each obturation technique. Results: CW obturation technique had more voids volume at the three different apical levels (1 mm: 0.19 ± 0.16, 3 mm: 0.76 ± 0.81, and 5 mm: 1.36 ± 1.44) compared to CL condensation technique at the same three levels (1 mm: 0.14 ± 0.21, 3 mm: 0.46 ± 0.46, and 5 mm: 1.10 ± 0.93) with no statistical significant difference between them (P Conclusions: None of the root canals filled teeth were voids-free, and there was no statistically significant difference between the two obturation techniques regarding the gaps volume apically.

Alpha correlations in terms of the hyper-Pfaffian

We find that the overlap between alpha-like four-body condensation wave function and m-scheme basis state can be represented by the hyper-Pfaffian, which is a natural extension of the Pfaffian for thepair-condensation wave function. This overlap is useful for nuclear structure calculations with the variational Monte Carlo method. As the hyper-Pfaffian has, however, only a few mathematical relations, it is quite difficult to use for numerical computations. We also find that a specific case of hyper-Pfaffian can be expressed by the sum of standard Pfaffians.

A comparative evaluation of fracture resistance of endodontically treated teeth obturated with four different methods of obturation: An in vitro study

Objective: The objective is to compare the vertical fracture resistance of teeth obturated with four different obturating techniques using universal testing machine (UTM). Materials and Methods: One hundred single-rooted mandibular premolars were instrumented with ProTaper Universal rotary files up to size F3. Samples were obturated using four different methods of obturation (Lateral compaction, continuous wave condensation (CWC), GuttaFlow 2, and GuttaCore). UTM was used for the evaluation of fracture resistance. Data were analyzed by one-way ANOVA and student t- test. Results: The highest tolerated mean load, in the decreasing order, was observed with GuttaCore (346.3 ± 45.0), GuttaFlow 2 (211.0 ± 29.8), lateral compaction (169.8 ± 23.6), and continuous-wave condensation obturation (167.6 ± 19.3). Conclusion: The GuttaCore system showed superior fracture resistance when compared to GuttaFlow 2, continuous-wave condensation and lateral compaction obturation method.

In Vitro Assessment of Apical Leakage of Bioceramic Endodontic Sealer with Two Obturation Techniques

Purpose: The aim of this study was to evaluate the apical sealing ability of Total Fill BC sealer and AH Plus sealer with single cone and continuous wave condensation obturation techniques using dye extraction leakage method. Materials and Methods: Eighty-four extracted human single-rooted teeth with round canals were decoronated at 12 mm length and instrumented using crown down technique with the iRace rotary file system to apical file size 40 with 0.04 taper. The roots were randomly divided into four experimental groups (n=20). Group (A1) contained roots which were obturated with Total Fill BC sealer with a single cone. Group (A2) contained roots which were obturated using Total Fill BC sealer with continuous wave condensation. Group (B1) contained roots which were obturated using epoxy resin sealer (AH Plus) with a single cone. Group (B2) contained roots which were obturated using AH Plus sealer with continuous wave condensation. Apical microleakage was assessed with dye extraction method where the absorbance of leaked 1% methylene blue dye was measured using a spectrophotometer. The absorbance values were converted into concentrations, and the data was analyzed using One way ANOVA test. Results: The mean dye concentration values were 0.012, 0.016, 0.011 and 0.015 for Group A1, Group A2, Group B1 and Group B2, respectively. One-way ANOVA indicated no significant difference in dye leakage between the investigated groups (F = 0.938). Conclusion: With the limitation of the study, it was concluded that Total Fill BC was equivalent to AH Plus in apical sealing ability when using single cone or continuous wave condensation. The single cone can provide a similar apical seal of canal filling as can be achieved by using continuous wave condensation methods, in the round canal.

Effect of obturation technique with immediate and delayed post space preparation on apical voids and bond strength of apical gutta-percha.

ObjectiveThe purpose of this study was to evaluate the effect of immediate and delayed post space preparation on the sealing ability of two root canal obturation techniques by using micro-computed tomography imaging and a push-out test.MethodsThe root canals of 40 human maxillary premolar teeth were instrumented and divided into four groups: (A) single cone (SC) followed by immediate post space preparation, (B) continuous wave of condensation (CWC) followed by immediate post space preparation, (C) SC followed by delayed post space preparation, and (D) CWC followed by delayed post space preparation. Micro-CT scans were performed for volumetric analysis of voids and filling materials in the apical 4-mm portion. A push-out test was performed, and failure modes (adhesive, cohesive, or mixed) were assessed. Data were analyzed using the Kruskal-Wallis test and one-way analysis of variance.ResultsNo significant differences were observed among the four groups in terms of the percentage volume of voids of the apical 4 mm or the bond strength of apical gutta-percha.ConclusionsThe percentage volume of voids and bond strength of apical gutta-percha were similar and were not significantly influenced by the timing of post space preparation or the obturation technique.

A regressive model for dynamic instabilities during condensation of pro-ecological environmentally friendly refrigerant R1234yf

The following paper presents a draft of a generalised model for velocities of dynamic instabilities (pressure wave vp and condensation front vT). This regressive model is based on experimental data obtained during the condensation of refrigerants in tubular minichannels. The dimensional analysis procedure was conducted according to the Π-Buckinghama theorem. The first part presents experimental data as well as a mathematical model for the pro-ecological refrigerant R1234yf designated as a substitute for the R134a refrigerant that is currently being phased-out. The research was conducted using tubular minichannels with ID = 1.44, 2.3, 3.3 mm.

Assessment of three Techniques in Surpassing Ledges in Curved Canals

Abstract The ledge formation is an iatrogenic accident that occurs in a curved canal due to the incorect application of the preparation techniques. The aim of this study was to find out which of the three well-known obturation techniques can surpass better an artificial created ledge. Matherials and methods: artificial ledge were created using Gates-Glidden drills no.1 and 2 at 15 mm and no.3 at 13 mm of the working lenght of fortyfour resin blocks. Thirty blocks that didn’t allowed a #10 file to surpass the ledge were accepted for study, divided into three equal groups and filled by lateral condensation, thermal compaction and continuous wave System B technique. Results: System B resulted in the highest obturated area beyond the starting point of the ledge (p<0,05), while lateral condensation showed the worst results. There were no differences between thermal compaction and lateral condensation in surpassing the deviation. Conclusion: within the limitation of this study, System B seems to be the the most appropriate techique when trying to surpass a ledge.

Experimental study on the interfacial wave and local heat transfer coefficient of stable steam jet condensation in a rectangular mix chamber

An experimental study on the interfacial wave and local heat transfer coefficient of stable steam jet condensation in a rectangular mix chamber was carried out. In experiments, the interfacial wave amplitude was obtained and analyzed, and an empirical correlation predicting the dimensionless wave amplitude was established. To evaluate the local average heat transfer coefficient, a thermal equilibrium model was developed, and the local average heat transfer characteristics were obtained and discussed. The results indicate that the interfacial wave amplitude increases with water mass flux and the axial dimensionless position, decreases with the steam mass flux, and changes little with inlet water temperature. The local average heat transfer coefficients are within the range of 0.98–6.24 MW/m2 °C, and they increase with the interfacial wave amplitude. The interfacial fluctuation could promote the steam jet condensation and corresponding heat transfer coefficients.

Chiral density wave versus pion condensation at finite density and zero temperature

The quark-meson model is often used as an effective low-energy model for QCD to study the chiral transition at finite temperature $T$, baryon chemical potential $\mu_B$, and isospin chemical potential $\mu_I$. The parameters of the model are determined by matching the meson and quark masses, as well as the pion decay constant to their physical values using the on-shell and modified minimal subtraction schemes. In this paper, we study the possibility of different phases at zero temperature. In particular, we investigate the competition between an inhomogeneous chiral condensate and a pion condensate. For the inhomogeneity, we use a chiral-density wave ansatz. For a sigma mass of $600$ MeV, we find that an inhomogeneous chiral condensate exist only for pion masses below approximately 37 MeV. We also show that due to our parameter fixing, the onset of pion condensation takes place exactly at $\mu_I={1\over2}m_{\pi}$ in accordance with exact results.

Novel Calcium Zirconate Silicate Cement Biomineralize and Seal Root Canals.

This study evaluated the sealing ability of gutta-percha (GP) with a calcium silicate-based sealer and a novel calcium zirconate containing calcium silicate cement (ZC). The root canals of the extracted premolars were prepared, which were then randomly allocated to three experimental groups (12 root canals per group) for obturation by continuous wave of condensation with the GP and AH 26 sealer (CW); obturation using a single GP with a calcium silicate-based EndoSequence BC sealer (SC); or obturation with ZC. The roots were inserted into sterile Eppendorf tubes, which were inoculated coronally with Porphyromonas gingivalis. The amount of endotoxin leakage into the apical reservoirs were measured using the Limulus Amebocyte Lysate (LAL) assay over 21 days, with comparisons made using one-way ANOVA and Scheffe’s tests (α = 0.05). After 21 days, 75% of the canals that had been obturated by SC, 50% of those obturated by CW and 42% of those obturated by ZC showed endotoxin leakage. The amount of leakage was higher in the SC canals than in the CW (p = 0.031) or ZC (p = 0.03) canals, although there was no significant difference in the amount of leakage for CW and ZC (p > 0.05). X-ray diffraction revealed the presence of tricalcium silicate (Ca3SiO5) and calcium zirconate (CaZrO3) in the synthesized ZC. Scanning electron microscopy revealed mineralized precipitates on the dentin of canals obturated by ZC. The novel calcium zirconate silicate cement appears to promote biomineralization and seal root canals at least as effectively as the conventional sealer.

Effect of Shock Wave and Non-Equilibrium Condensation to Corner flow in a Three-Dimensional Supersonic Rectangular Nozzle

Effect of Shock Wave and Non-Equilibrium Condensation to Corner flow in a Three-Dimensional Supersonic Rectangular Nozzle

Current trends in technological armamentarium and treatment among Brazilian endodontists

Aim: To determine the current trends in technological armamentarium and endodontic treatment among Brazilian endodontists. Methods: A total of 279 endodontists answered a web-based survey questionnaire about their region of activity in Brazil and years as a specialist, average number of endodontic cases treated per month, number of visits to complete the treatment, use of rubber dam for isolation, type of irrigant, obturation technique and device used for this purpose, temporary filling materials, and greater difficulty encountered during treatment and technological armamentarium. A descriptive analysis, expressed in terms of frequency and percentage, was performed and the data were correlated using the chi-square test (p0.05). Results: Most of the respondents had up to 10 years as specialists. More than 50% of endodontists preferred to complete the endodontic treatment in a single visit. Ninety-nine percent of endodontists used rubber dam for isolation. NaOCl was the most widely used irrigant. Most of the respondents associated different techniques for root canal filling. Lateral condensation and Continuous wave of condensation were the isolated technique most reported. Filling devices (thermocompactors) were used by 53% of endodontists. Glass ionomer was the preferred temporary filling material. The answers for the use of technological armamentarium revealing that 94% of endodontists used an apex locator; 67.38% utilized magnification (loupe: 23.66%; microscope: 35.48%; microscope and loupe: 8.24%); 58% reported to digital radiography; and 47.31% used computed tomography as a complementary tool. About mechanized instrumentation, 44.44% endodontists employed rotary and reciprocating files. The difficulties encountered during endodontic treatment were classified as preparation > access > obturation > anesthesia > isolation. Conclusions: Most endodontists have implemented new technologies, such as mechanical instrumentation, apex locators, magnification, digital radiography, computed tomography, ultrasound, and obturation tools, in their clinical practice.

Origins of spectral broadening of incoherent waves: Catastrophic process of coherence degradation

We revisit the mechanisms underlying the process of spectral broadening of incoherent optical waves propagating in nonlinear media on the basis of nonequilibrium thermodynamic considerations. A simple analysis reveals that a prerequisite for the existence of a significant spectral broadening of the waves is that the linear part of the energy (Hamiltonian) has different contributions of opposite signs. It turns out that, at variance with the expected soliton turbulence scenario, an increase of the amount of disorder (incoherence) in the system does not require the generation of a coherent soliton structure. We illustrate the idea by considering the propagation of two wave components in an optical fiber with opposite dispersion coefficients. A wave turbulence approach of the problem reveals that the increase of kinetic energy in one component is offset by the negative reduction in the other component, so that the waves exhibit, as a general rule, a virtually unlimited spectral broadening. More precisely, a self-similar solution of the kinetic equations reveals that the spectra of the incoherent waves tend to relax toward a homogeneous distribution in the wake of a front that propagates in frequency space with a decelerating velocity. We discuss this catastrophic process of spectral broadening in the light of different important phenomena, in particular supercontinuum generation, soliton turbulence, wave condensation, and the runaway motion of mechanical systems composed of positive and negative masses.