Pancake Model Research Articles

On the Validity of the Pancake Models of the Falls of Cosmic Bodies in the Atmosphere

On the Validity of the Pancake Models of the Falls of Cosmic Bodies in the Atmosphere

Evaluation of the effectiveness and durability of commercial non-stick coatings

In this study, four commercial non-stick coatings (two fluoropolymer and two ceramic) were characterized by micrography, Raman spectroscopy and energy dispersive X-ray spectroscopy (EDX). A pancake batter was then baked on coated aluminum substrates. In a first test, 90 consecutive baking cycles were performed on each coated specimen. In a second test, the coatings were abraded by sanding, followed by 30 baking cycles. In both cases, take-off pressure was evaluated to extract the pancake model, as well as water sliding angle, surface roughness and surface damage. The results have shown that perfluoroalkoxyalkane (PFA) and polytetrafluoroethylene (PTFE) were the most effective in terms of pull-off pressure (<3 kPa) versus ceramic siloxane coatings with values between 15 and 34 kPa after 90 firings. In the different experimental stages, a positive correlation between wettability and detachment force was observed, especially for fluoropolymer coatings. However, surface roughness did not strong correlate with the pull-off force, low values did not correlate with low values of pull-off force and vice versa. This paper proposes an objective and simple coating evaluation procedure for industrial environments. Although ceramic sol-gel coatings show potential, there is a need to improve their non-stick capability to bring them on par with traditional solutions.

Stability of starch-proanthocyanidin complexes to in-vitro amylase digestion after hydrothermal processing.

Proanthocyanidins (PA) form poorly digestible complexes with starch. The study examined amylase degradation mechanism and hydrothermal stability of starch-PA complexes. Sorghum-derived PA was complexed with wheat starch, reconstituted into flour (10% gluten added) and processed into crackers and pancakes. In vitro digestion profile of the complexes and products were characterized. The starch-PA complexes retained more (34-84%) fragments with degree of polymerization (DP)>6,000 after 120min digestion than controls (0-21%). Debranching further revealed higher retention of DP 11 - 30 chains in the digested starch-PA complexes than controls, suggesting amylopectin complexation contributed to reduced starch digestion. Starch-PA complexes retained reduced digestibility (50-56% higher resistant starch vs controls) in the cracker, but not pancake model. However, removing gluten from the pancake formulation restored the reduced digestibility of the starch-PA complexes. The starch-PA complexes are stable to hydrothermal processing, but can be disrupted by hydrophobic gluten proteins under excess moisture conditions.

Near-Earth object 2022 EB5: From atmospheric entry to physical properties and orbit

Context. The near-Earth object (NEO) 2022 EB5 is the fifth NEO found prior to entering the Earth's atmosphere. It fragmented over the Norway Sea on 2022 March 11 about two hours after being discovered by the astronomer Krisztián Sárneczky at Konkoly Observatory in Hungary. The Center for Near-Earth Object Studies (CNEOS) at NASA detected the visible radiation emitted at the time of its atmospheric entry. The Jet Propulsion Laboratory (JPL) and European Space Agency (ESA) derived its orbital elements based on observations of its pre-atmospheric orbit. Aims. This paper aims to calculate the physical properties of this NEO, in particular, the bulk strength, type of the material, albedo, size, and mass, based on observations of its peak brightness at the time of its atmospheric entry. In addition, the heliocentric elements are computed from its interaction with Earth's atmosphere and compared with those derived from observations by JPL and ESA, respectively, to evaluate the accuracy of our method. Methods. The flight equations of 2022 EB5 were inversely integrated from the peak brightness to the atmospheric boundary via the fourth-order Runge-Kutta method. A pancake model was utilized to simulate the fragmentation of the impactor. Parameters needed to complete the integration process that were unknown were set to be optimization variables and determined via a genetic algorithm. Results. The results obtained show that 2022 EB5 was most likely a C-type asteroid with a maximal bulk strength of 2 MPa, diameter of 5–6 m, cometary density, and very low albedo that is no greater than 0.025. In addition, considering the effects of the atmosphere is helpful in getting a more accurate measurement for the semi-major axis, eccentricity, and inclination, although the accuracy of orbital elements strongly depends on the accuracy of USG sensors.

Spatial Orientations of Angular Momentum Vectors of Galaxies in Supercluster S [195+027+0022] and Substructure

This paper presents an analysis of the spin vector orientations of SDSS (Sloan Digital Sky Survey) galaxies in the Supercluster S [195+027+0022] using the seventh data release (2008 October). By using the spectroscopic database of galaxies, identified number density map in the region of Superclusters. Several density enhancements are observed, suggesting the possibility of substructure in the Supercluster. Two-dimensional observed parameters that we received from the database are used to compute three-dimensional galaxy rotation axes by applying `position angle-inclination' method. Apply the selection effects by performing the random simulation method. The expected distribution curves are obtained from the simulation. Chi-square, auto-correlation, and Fourier tests are used to examine non-random effects in the polar and azimuthal angle distributions of the galaxy rotation axes. To check these results with the different galaxy evolution models namely Hierarchy, Primordial, and Pancake model. The result supports the Hierarchy model.

Study of Spatial Orientation of Angular Momentum of z-Magnitude SDSS DR-13 Galaxies with Red Shift 0.50 to 0.53

The spatial orientations of 142,929 SDSS DR-13, z- magnitude galaxies having red shift 0.50 to 0.53 have been analyzed. The main goal of this work is to examine the orientation of the angular momentum of galaxies within the given redshift limit in the framework of three different scenarios 'Hierarchy model', 'Pancake model', and the 'Primordial vorticity model'. By using Godlowskian transformation the two-dimensional data were converted into three-dimensional data (polar and azimuthal angles). The expected isotropy distribution curves were obtained by removing the selection effects and performing a random simulation to generate 107 virtual galaxies by using Matlab 2015a. Three statistical tests of Chi-square, autocorrelation, and Fourier were used to compare the expected isotropic data with observed. The data classified into nine subsamples having each of one magnitude size. In general, the results supported the Hierarchy model. The model advocates random orientations of angular. However, a local anisotropy observed in few subsamples suggested a gravitational tidal interaction between neighboring galaxies, an early-merging process in which the angular momentum vector distorts the initial alignment of nearby galaxies.

Spatial Orientations of Angular Momentum Vectors of Galaxies in Supercluster S [247+040+0029] and Substructures

We present an analysis of spatial orientations of 1331 galaxies in the supercluster S [247+040+0029]. The main goal of this work is to search for a new substructure candidate and examine the orientation of angular momentum in the framework of three different scenarios (hierarchy, pancake, and primordial vorticity models) using “position angle-inclination method”, and to test the dependence on magnitude with the angular momentum orientations and their projections. We identified five substructures studying number density contour map with considerably high concentration of galaxies. Using random simulation method to remove the selection effect on database, we carried out expected isotropic distribution using cosmological principle. We then used three statistical tests: Chi-square, Auto-correlation, and Fourier to identify isotropy between observed and expected isotropic distributions. We varied radius in the range 0.3° to 1.0° to find substructures in supercluster. From this we found five sub-structures when taking radius 0.3° and two substructures for 1.0° radius in the number density counter maps of galaxies. By analyzing the result obtained through statistical tests, we are able to conform that evolution of galaxy in the supercluster and substructures supports “Hierarchy model" giving the angular momentum of galaxies in the large scale structure tends to be oriented random with respect to the reference coordinate system.

Quench-induced Dynamic Breakdown Characteristics of HTS Pancake Coil Model for Resistive SFCL

Quench-induced dynamic breakdown (BD) characteristics of LN2 under transient bubble disturbance at the quench of HTS tapes are crucial to the reliable and rational insulation design of resistive superconducting fault current limiters (RSFCL). We have been investigating the dynamic BD characteristics using a nichrome pancake coil model for RSFCL using bifilar nichrome tapes as a heater. In this paper, we fabricated an HTS pancake coil model for RSFCL using GdBCO tapes and discussed the dynamic BD characteristics as a function of heat flux generated from the actually quenched HTS tapes.

Dynamic Breakdown Characteristics of Pancake Coil Model for Resistive-Type Superconducting Fault Current Limiters

Toward the reliable and rational insulation design of resistive-type superconducting fault current limiters (RSFCL), we have been investigating not only the intrinsic breakdown (BD) characteristics of liquid nitrogen (LN2) without bubbles but also the dynamic BD characteristics of LN2 under the transient bubble disturbance at the quench of RSFCL coils. We have so far used a fundamental model such as sphere-plane electrode system with quasi-uniform electric field. However, when RSFCL will be introduced in a future electric power network, a stack of pancake coils with non-uniform electric field will be adopted for the practical development of RSFCL. In this paper, we designed and fabricated a pancake coil model for RSFCL, and investigated the intrinsic and dynamic BD characteristics of the pancake coil models in LN2. Experimental results are discussed in terms of the volume effect of intrinsic and dynamic BD strength under non-uniform electric field.

Superfluid density of anisotropic S-wave superconductors by semi-classical approach: Applied to MgB2 and CaAlSi superconductors

In this research, we investigated the superfluid density of anisotropic S-wave superconductors by Semi-classical Theory in 3D spherical Fermi surface. The anisotropic gap function was studied by ellipse spherical and pancake spherical model. The superfluid density was derived analytically and applied to MgB2 and CaAlSi superconductors. We found that CaAlSi superconductors show the properties of anisotropic one band S-wave superconductors but the MgB2 superconductors cannot fit well with our model.

Monitoring composition of LNAPL: essential tool for the estimation of free LNAPL specific volumes

In an aquifer contaminated by LNAPLs, several types of LNAPL can been find with different composition and features, which influence its fate and transport in groundwater and the estimation of its volume.Over time, two different models have been developed for the free phase volume estimation: Pancake Model and Vertical Equilibrium Model. A sensitivity analysis has been carried out, using both models, to evaluate the influence of LNAPL type on volume estimation. This analysis has been carried out applying in every examined monitoring well the features of three different LNAPL types: gasoline, diesel andtheir mixtures. The results show a sensible variation of estimated specific volumes as LNAPL type varies. Hence, as it can been deduced, the knowledge of LNAPL type and its characteristics are fundamental for a reliable volume estimation. In addition, since the LNAPL type can change over the time, when a contaminated site is monitored for the evaluation of LNAPL volumes, it is fundamental observe duringthe time, not only the supernatant thickness in the well, but also the compounds constituting the LNAPL, through the sampling of supernatant and its analysis.

Free LNAPL Volume Estimation by Pancake Model and Vertical Equilibrium Model: Comparison of Results, Limitations, and Critical Points

Light nonaqueous phase liquids (LNAPLs), due to their low solubility, dissolve slowly, acting as a long-term source of water contamination, and consequently they represent an important environmental issue. In the subsoil, more than 99% of spilled LNAPL remains as adsorbed and free phase; therefore, the volume estimation of free phase, obtained in this case through two different conceptual models (Pancake Model and Vertical Equilibrium Model), is considered a fundamental step for a correct site remediation. According to the first model, the LNAPL floating on the water table and its saturation is up to 100%; instead, according to the second one, the LNAPL can penetrate below the water table and the coexistence of LNAPL, water, and air in the pore fraction, leads to a lower LNAPL saturation, variable with the depth. Actually, in subsoil LNAPL and water saturations vary with depth due to the influence of capillarity, leading to the inaccuracy of Pancake Model assumption. Despite the evident limitation of Pancake Model, both models were applied, coupled with area calculations with Thiessen polygons and grid at regular mesh, to roughly estimate the free LNAPL volume existing in a contaminated site. The volume estimation carried out, considering the LNAPL type and its features, the soil type, and relative effective porosity, provides estimates of volumes having differences up to thousands of cubic meters. The results analysis shows that this estimation has several critical points such as area definition and the lack of site-specific data (e.g., porosity). Indeed, the sensitivity analysis for porosity shows that a reduction of this parameter provides a 20% reduction of estimated volume.

Methodological approach for the estimation of recoverable LNAPL volumes in aquifer and for the analysis of residual phase behaviour in laboratory

Free and residual phases are the most abundant phases of LNAPL (light non aqueous phase liquid) in the subsoil; therefore the free phase volume estimation and the understanding of residual phase behaviour are fundamental for an effective remediation. The volume estimation of free phase present in a contaminated site was carried out through the application of the Pancake Model and the Vertical Equilibrium Model. This estimation shows a remarkable difference between the two models and between the different delimitation area methods employed. In particular, the estimated volumes are lower for the Vertical Equilibrium Model and the higher difference is observed for a 200x200 mesh. The results underline also some critical points as the amount of the effective porosity; indeed the sensitivity analysis shows that a reduction of this parameter produce a variation of the estimated volume until to 20%. The behaviour of residual phase was analysed through lab-scale column tests carried out using three different porous media and toluene as contaminant. The higher residual saturation and lower dissolution in finer materials reveal the influence of porous media on toluene behaviour. The lower dissolution is confirmed also by the modelling realized using a traditional approach and an approach based on experimental results. The risk analysis, carried out applying a traditional approach and a new experimental approach, shows that the last one allow to have a more reliable hazard index which contemplates the site specific conditions.

Gravitational waves and core-collapse supernovae

A mechanism of formation of gravitational waves in the Universe is considered for a nonspherical collapse of matter. Nonspherical collapse results are presented for a uniform spheroid of dust and a finite-entropy spheroid. Numerical simulation results on core-collapse supernova explosions are presented for the neutrino and magneto-rotational models. These results are used to estimate the dimensionless amplitude of the gravitational wave with a frequency ν ~ 1300 Hz, radiated during the collapse of the rotating core of a pre-supernova with a mass of 1.2 M⊙ (calculated by the authors in 2D). This estimate agrees well with many other calculations (presented in this paper) that have been done in 2D and 3D settings and which rely on more exact and sophisticated calculations of the gravitational wave amplitude. The formation of the large-scale structure of the Universe in the Zel’dovich pancake model involves the emission of very long-wavelength gravitational waves. The average amplitude of these waves is calculated from the simulation, in the uniform spheroid approximation, of the nonspherical collapse of noncollisional dust matter, which imitates dark matter. It is noted that a gravitational wave radiated during a core-collapse supernova explosion in our Galaxy has a sufficient amplitude to be detected by existing gravitational wave telescopes.

Probability of detection model for the non-destructive inspection of steam generator tubes of PWRs

This study proposes a probability of detection (POD) model to discuss the capability of non-destructive testing methods for the detection of stress corrosion cracks appearing in the steam generator tubes of pressurized water reactors. Three-dimensional finite element simulations were conducted to evaluate eddy current signals due to stress corrosion cracks. The simulations consider an absolute type pancake probe and model a stress corrosion crack as a region with a certain electrical conductivity inside to account for eddy currents flowing across a flaw. The probabilistic nature of a non-destructive test is simulated by varying the electrical conductivity of the modelled stress corrosion cracking. A two-dimensional POD model, which provides the POD as a function of the depth and length of a flaw, is presented together with a conventional POD model characterizing a flaw using a single parameter. The effect of the number of the samples on the PODs is also discussed.

A numerical assessment of simple airblast models of impact airbursts

AbstractAsteroids and comets 10–100 m in size that collide with Earth disrupt dramatically in the atmosphere with an explosive transfer of energy, caused by extreme air drag. Such airbursts produce a strong blastwave that radiates from the meteoroid's trajectory and can cause damage on the surface. An established technique for predicting airburst blastwave damage is to treat the airburst as a static source of energy and to extrapolate empirical results of nuclear explosion tests using an energy‐based scaling approach. Here we compare this approach to two more complex models using the iSALE shock physics code. We consider a moving‐source airburst model where the meteoroid's energy is partitioned as two‐thirds internal energy and one‐third kinetic energy at the burst altitude, and a model in which energy is deposited into the atmosphere along the meteoroid's trajectory based on the pancake model of meteoroid disruption. To justify use of the pancake model, we show that it provides a good fit to the inferred energy release of the 2013 Chelyabinsk fireball. Predicted overpressures from all three models are broadly consistent at radial distances from ground zero that exceed three times the burst height. At smaller radial distances, the moving‐source model predicts overpressures two times greater than the static‐source model, whereas the cylindrical line‐source model based on the pancake model predicts overpressures two times lower than the static‐source model. Given other uncertainties associated with airblast damage predictions, the static‐source approach provides an adequate approximation of the azimuthally averaged airblast for probabilistic hazard assessment.

Growth and wetting of water droplet condensed between micron-sized particles and substrate.

We study heterogeneous condensation growth of water droplets on micron-sized particles resting on a level substrate. Through numerical simulations on equilibrium droplet profiles, we find multiple wetting states towards complete wetting of the particle. Specifically, a partially wetting droplet could undergo a spontaneous transition to complete wetting during condensation growth, for contact angles above a threshold minimum. In addition, we find a competitive wetting behavior between the particle and the substrate, and interestingly, a reversal of the wetting dependence on contact angles during late stages of droplet growth. Using quasi-steady assumption, we simulate a growing droplet under a constant condensation flux, and the results are in good agreement with our experimental observations. As a geometric approximation for particle clusters, we propose and validate a pancake model, and with it, show that a particle cluster has greater wetting tendency compared to a single particle. Together, our results indicate a strong interplay between contact angle, capillarity and geometry during condensation growth.

Study of electromigration-induced formation of discrete voids in flip-chip solder joints by in-situ 3D laminography observation and finite-element modeling

In the microelectronics industry the flip-chip (FC) technology is broadly used to enhance the packaging density. However, the small size and the unique geometry of the FC solder joints induce the electromigration (EM) reliability issue. In this study, a pair of lead-free solder joints (SAC1205) was EM tested by a current of 7.5 × 103 A/cm2. During the tests, X-ray laminography was applied to observe the microstructure evolution in-situ. Laminography enables the non-destructive observation of the bump microstructure and allows for a quantitative three-dimensional (3D) analysis. After EM testing for 650 h, a new EM failure mechanism was found, differing from the two well-known models, the pancake void propagation and the under-bump-metallization dissolution. Here, a few pre-existing small voids grew and simultaneously many new voids formed and grew over the entire EM testing period. Most of the nucleating voids were distributed in the current crowding region, a few also located in the low-current-density region. As the testing time increased, voids increasingly coalesced with each other, forming a porous network which occupied a large part of the interface area and caused the EM failure. A finite-element (FE) method was then applied to analyze the interplay between the microstructure evolution and current density redistribution. A series of 3D FE models was built based on the laminography images for the different testing stages. The current density distribution from the FE analysis indicates that the formation of discrete voids did not affect the global current density distribution until a major coalescence of the voids occurred. The relieving of the global current crowding in the pancake void model was not found in this new EM failure mechanism. It was the local current crowding around individual void found in the new mechanism that is held responsible for the EM retardation.

The Role of Intrinsic Noise in Origin of Quorum Sensing

Many biological phenomena about quorum sensing in bacteria are driven by experimentally and mathematically in the last few decades. Symbiosis, virulence etc. are the major area in which these theoretical models work well. But no specific origin was established so far which can explain quorum sensing itself. This weakly nonlocal fluid dynamical model of bacterial communication system introduces a pancake model which involves the intrinsic noise of the system to explain the origin of quorum sensing. The internal structure of quorum sensing analogues to Zeldovich model and origin of internal noise in this mechanism is responsible for quorum sensing.

Determination of the height of the “meteoric explosion”

When cosmic bodies of asteroidal and cometary origin, with a size from 20 to approximately 100 m, enter dense atmospheric layers, they are destroyed with a large probability under the action of aerodynamic forces and decelerated with the transfer of their energy to the air at heights from 20–30 to several kilometers. The forming shock wave reaches the Earth’s surface and can cause considerable damage at great distances from the entry path similar to the action of a high-altitude explosion. We have performed a numerical simulation of the disruption (with allowance for evaporation of fragments) and deceleration of meteoroids having the aforesaid dimensions and entering the Earth’s atmosphere at different angles and determined the height of the equivalent explosion point generating the same shock wave as the fall of a cosmic body with the given parameters. It turns out that this height does not depend on the velocity of the body and is approximately equal to the height at which this velocity is reduced by half. The obtained results were successfully approximated by a simple analytical formula allowing one to easily determine the height of an equivalent explosion depending on the dimensions of the body, its density, and angle of entry into the atmosphere. A comparison of the obtained results with well-known approximate analytical (pancake) models is presented and an application of the obtained formula to specific events, in particular, to the fall of the Chelyabinsk meteorite on February 15, 2013, and Tunguska event of 1908, is discussed.