Standard Scaling Laws Research Articles

Effects of prepulse on hot electron emission from mesoscopic particles

In this paper we make an attempt to study the effect of a nanosecond prepulse on electron acceleration from microscopic solid particles. While standard scaling laws predict temperatures of ∼50 keV, our investigations showed an anomalous enhancement ( ∼200 keV) in electron temperatures from microscopic solids subjected to intense laser fields. Conventional isotropic expansion of the plasma target as a result of pre-pulse interaction is unable to explain the enhancement, prompting an experimental inquiry into the expansion form. Tentacle-like structures emerging from the spherical plasma are detected as an outcome of the pre-pulse interaction, with the region between the tentacles being targeted by the main laser pulse. We resort to PIC simulations to understand and predict the exact plasma condition that exists in this region. In this paper, we study a series of approximate pre-plasma conditions, particle shapes, and electron densities, examining them for their role in electron acceleration from this extended over-critical plasma target.

Performance of a low power Hall effect thruster with several gaseous propellants

There is a growing need to consider alternative propellants for operation in Hall thrusters, away from the conventional legacy of using xenon. This is particularly the case for small Hall thrusters; which are growing exponentially in their use, whilst needing to be operational on inexpensive propellants. Alternative propellants include condensable propellants (i.e., zinc and iodine), or other gaseous propellants (krypton, argon, and nitrogen (N2)) - which are the focus here. A low power (nominally 100 W) miniature Hall thruster has been designed and manufactured based upon standard scaling laws, with specific considerations for operation with the use of alternative gaseous propellants, and with an attempted novel field topology. The thruster, designated the HEKT-100, was designed to be a low power magnetically shielded thruster to operate on krypton, however the level of shielding present is unknown or tested. Here the thruster has subsequently been operated on xenon, krypton, argon, and diatomic nitrogen successfully, with an unstable operation with neon. The thruster is operated at discharge powers of between 30–810 W. Using a pendulum thrust balance, the thruster performance was measured across a wide range of flow rates, magnetic field strengths, and anode discharge voltages. The performance measured for xenon, krypton, argon, and diatomic nitrogen respectively was, peak thrusts of 12.6 mN, 6.9 mN, 6.6 mN and 5.7 mN, anode efficiencies up to 26.3%, 15.2%, 9.6% and 5.4%, and specific impulses up to 2160 s, 1730 s, 1390 s, and 1000 s. This dataset and the following analysis provides one of the few times a comprehensive selection of alternative gaseous propellants have been tested within the same thruster and compared directly with unchanged geometry or set-up.

New insights into lunar terrain properties and their effect on derivation of absolute model ages using Apollo landing sites

The lunar crater chronology has been built by connecting radiometric ages of sampled terrains with the areal crater densities on those terrains, particularly the density at diameters (D) ≥ 1 km (aka N(>1)). In the past, very few crater chronologies have considered the effect of terrain properties on the crater densities and size-frequency distributions (SFDs) used to build them. This influence is especially important when N(>1) cannot be directly measured. Here we study this influence by using the Model Production Function (MPF) chronology, which incorporates terrain properties into computing N(>1) and absolute model ages (AMAs) through computing crater diameters using standard crater scaling laws. Furthermore, we also gain a better understanding of actual lunar terrain properties by adjusting the MPF to reproduce AMAs close to the radiometric ages of several Apollo sample sites. The properties examined are the consolidation state of the terrain, its effective cratering strength, and density. Overall, we find that the impact melt of Copernicus crater (∼0.8 Ga) is stronger and more consolidated than the mare and highland terrains investigated. The mare become less consolidated and weaker as they age (from 3.1 to 3.8 Ga) – likely due to fracturing and regolith formation by subsequent impacts. The highlands (∼3.8 Ga) are the weakest terrain. The analysis of terrain proprieties allows our MPF computations to reproduce the radiometric ages, and the impact melt and ejecta of Copernicus crater to have the same age, as expected. The new lunar terrain property constraints can be used with the MPF to derive more robust absolute model ages for unsampled terrains. The values presented in this work for impact melt, ejecta, mare, and highlands can serve as references.

Empirical Acoustic Source Model for Chemical Explosions in Air

ABSTRACT Chemical explosions generate pressure disturbances in air that radiate as nonlinear shock waves near the source and transition into acoustic waves with distance. Because low-frequency acoustic waves generally travel large distances without significant loss of energy, they are often used for explosion monitoring and yield estimation. However, quantitative relationships between acoustic energy and explosion yields are required for accurate yield estimation. Here, we develop an empirical acoustic source model for chemical explosions from experimental data. The empirical model returns the acoustic pressure waveform for the detonation of 1 kg of trinitrotoluene, which is conventionally used to represent the explosive release of 4.184 MJ of explosion energy. The full-waveform model can be used to predict acoustic signals for an arbitrary yield of a high-explosive detonation based on the standard scaling law and to estimate acoustic energies in a specific frequency range. We evaluate the accuracy of the acoustic source model independently by estimating the yield of other explosive events that are not included in the model development. Statistical characteristics of the model and their implications for the uncertainty quantification of estimated yields are discussed.

Temperature study of Rydberg exciton optical properties in Cu2O

Rydberg excitons in ${\mathrm{Cu}}_{2}\mathrm{O}$ can be an emergent platform for solid-state quantum information processing by utilizing the exaggerated properties of high-lying excited states within the material. To develop practical quantum systems, high-temperature operation is desirable. Here, we study the temperature dependence of the yellow and green Rydberg exciton resonances in a thin ${\mathrm{Cu}}_{2}\mathrm{O}$ crystal via broad-band phonon-assisted absorption spectra between 4 K and 100 K. At 4 K, we can identify the principal quantum number $n=11$ yellow and $n=4$ green Rydberg exciton states, beyond which we are limited by the spectral resolution of standard absorption techniques. Above liquid nitrogen boiling temperature ($\ensuremath{\sim}80\phantom{\rule{0.16em}{0ex}}\mathrm{K}$), the $n=6$ yellow and $n=4$ green Rydberg exciton states are readily captured and higher-temperature yellow Rydberg exciton optical properties still exhibit the standard scaling laws seen at low temperatures. This promising result lays the groundwork for a new route to build a high-temperature Rydberg quantum information processing architecture with solid-state ${\mathrm{Cu}}_{2}\mathrm{O}$.

Transport Characteristics of the Electrification and Lightning of the Gas Mixture Representing the Atmospheres of the Solar System Planets

Electrification represents a fundamental process in planetary atmospheres, widespread in the Solar System. The atmospheres of the terrestrial planets (Venus, Earth, and Mars) range from thin to thick are rich in heavier gases and gaseous compounds, such as carbon dioxide, nitrogen, oxygen, argon, sodium, sulfur dioxide, and carbon monoxide. The Jovian planets (Jupiter, Saturn, Uranus, and Neptune) have thick atmospheres mainly composed of hydrogen and helium involving. The electrical discharge processes occur in the planetary atmospheres leading to potential hazards due to arcing on landers and rovers. Lightning does not only affect the atmospheric chemical composition but also has been involved in the origin of life in the terrestrial atmosphere. This paper is dealing with the transport parameters and the breakdown voltage curves of the gas compositions representing atmospheres of the planets of the Solar System. Ionization coefficients, electron energy distribution functions, and the mean energy of the atmospheric gas mixtures have been calculated by BOLSIG+. Transport parameters of the carbon dioxide rich atmospheric compositions are similar but differ from those of the Earth’s atmosphere. Small differences between parameters of the Solar System’s outer planets can be explained by a small abundance of their constituent gases as compared to the abundance of hydrogen. Based on the fit of the reduced effective ionization coefficient, the breakdown voltage curves for atmospheric mixtures have been plotted. It was found that the breakdown voltage curves corresponding to the atmospheres of Solar System planets follow the standard scaling law. Results of calculations satisfactorily agree with the available data from the literature. The minimal and the maximal value of the voltage required to trigger electric breakdown is obtained for the Martian and Jupiter atmospheres, respectively.

Critical properties of symmetric nuclear matter in low-density regime using effective-relativistic mean field formalism

The effective field theory motivated relativistic mean-field (E-RMF) formalism is employed to study the equation of state (EoS) for the infinite symmetric nuclear matter (SNM) at finite temperature using the recently developed forces FSUGarnet, IOPB-I, G3, and the well known NL3 force parameter. The EoS is then used to estimate the critical temperature T c, pressure P c and density ρ c of the SNM for the liquid–gas phase transition. As T c is not a constrained parameter in both experiments and theoretical calculations, there is a large uncertainty around its value. Although, the critical parameters are correlated among themselves. It is revealed that vector self-coupling ζ 0 of used forces play determining role in EoS in finite temperature limit. Keeping the incompressibility in acceptable limit i.e. 240 ± 20 MeV, the lower value of ζ 0 gives a better result of T c when compared to the several experimental data. The critical parameters however show weak correlation with the properties at saturation density at zero temperature. The compressibility factors calculated with these parameters are in agreement with the universal value of liquid–gas systems. Stability conditions are examined along with binodal and spinodal regions. Besides this, the thermodynamic properties like specific heat and latent heat are also worked out. We have carried out detailed consistency check of our calculations using critical exponents and standard scaling laws. All the exponents are well within the theoretical mean-field results.

Fluctuating Elasticity Fails to Capture Anomalous Sound Scattering in Amorphous Solids.

The fluctuating elasticity (FE) model, introduced phenomenologically and developed by Schirmacher [J. Non-Cryst. Solids 357, 518 (2011)JNCSBJ0022-309310.1016/j.jnoncrysol.2010.07.052], is today the only theoretical framework available to analyze low-temperature elastic acoustic scattering in glasses. Its existing formulations, which neglect the tensorial nature of elasticity and exclude long-range disorder correlations, predict that the acoustic damping coefficients obey the standard Rayleigh scaling law: Γ∼k^{d+1}, with k the acoustic wave vector, in dimension d. However, recent numerical data, supported by the analysis of existing experimental results, show that Γ does not obey this scaling law but Γ∼-k^{d+1}lnk. Here we analyze in detail how a fully tensorial FE model can be constructed as a long wavelength approximation of the elastic response of the discrete, atomistic, problem. We show that, although it incorporates all long-range correlations, it fails to capture the observed damping in two respects: (i)it misses the anomalous scaling, and predicts the standard Rayleigh law; (ii)it grossly underestimates the amplitude of scattering by about 2 orders of magnitude. This brings clear evidence that the small scale nonaffine displacement fields, although not simply reducible to local defects, play a crucial role in acoustic wave scattering and hence cannot be ignored.

Scaling of heated plane jets with moderate radiative heat transfer in coupled DNS

The effects of thermal radiation in a heated jet of water vapor are studied with a direct numerical simulation coupled to a Monte-Carlo solver. The adequacy of the numerical setup is first demonstrated in the uncoupled isothermal and heated turbulent plane jets with comparisons to experimental and numerical data. Radiative energy transfer is then accounted for with spectral dependency of the radiative properties described by the Correlated-k (ck) method. Between the direct impact through modification of the temperature field by the additional radiative transfer and the indirect one where the varied flow density changes the turbulent mixing, the present study is able to clearly identify the second one in the jet developed region by considering conditions where effects of thermal radiation are moderate.When using standard jet scaling laws, the different studied cases without radiation and with small-to-moderate radiative heat transfer yield different profiles even when thermal radiation becomes locally negligible. By deriving another scaling law for the decay of the temperature profile, self-similarity is obtained for the different turbulent jets. The results of the study allow for distinguishing whether thermal radiation modifies the nature of heat transfer mechanisms in the jet developed region or not while removing the indirect effects of modified density.

Sequence Effects on Size, Shape, and Structural Heterogeneity in Intrinsically Disordered Proteins.

Intrinsically disordered proteins (IDPs) lack well-defined three-dimensional structures, thus challenging the archetypal notion of structure-function relationships. Determining the ensemble of conformations that IDPs explore under physiological conditions is the first step toward understanding their diverse cellular functions. Here, we quantitatively characterize the structural features of IDPs as a function of sequence and length using coarse-grained simulations. For diverse IDP sequences, with the number of residues ( NT) ranging from 20 to 441, our simulations not only reproduce the radii of gyration ( Rg) obtained from experiments, but also predict the full scattering intensity profiles in excellent agreement with small-angle X-ray scattering experiments. The Rg values are well-described by the standard Flory scaling law, Rg = Rg0 NTν, with ν ≈ 0.588, making it tempting to assert that IDPs behave as polymers in a good solvent. However, clustering analysis reveals that the menagerie of structures explored by IDPs is diverse, with the extent of heterogeneity being highly sequence-dependent, even though ensemble-averaged properties, such as the dependence of Rg on chain length, may suggest synthetic polymer-like behavior in a good solvent. For example, we show that for the highly charged Prothymosin-α, a substantial fraction of conformations is highly compact. Even if the sequence compositions are similar, as is the case for α-Synuclein and a truncated construct from the Tau protein, there are substantial differences in the conformational heterogeneity. Taken together, these observations imply that metrics based on net charge or related quantities alone cannot be used to anticipate the phases of IDPs, either in isolation or in complex with partner IDPs or RNA. Our work sets the stage for probing the interactions of IDPs with each other, with folded protein domains, or with partner RNAs, which are critical for describing the structures of stress granules and biomolecular condensates with important cellular functions.

Genuinely Ferroelectric Sub-1-Volt-Switchable Nanodomains in Hf xZr(1- x)O2 Ultrathin Capacitors.

The new class of fully silicon-compatible hafnia-based ferroelectrics with high switchable polarization and good endurance and thickness scalability shows a strong promise for new generations of logic and memory devices. Among other factors, their competitiveness depends on the power efficiency that requires reliable low-voltage operation. Here, we show genuine ferroelectric switching in Hf xZr(1- x)O2 (HZO) layers in the application-relevant capacitor geometry, for driving signals as low as 800 mV and coercive voltage below 500 mV. Enhanced piezoresponse force microscopy with sub-picometer sensitivity allowed for probing individual polarization domains under the top electrode and performing a detailed analysis of hysteretic switching. The authentic local piezoelectric loops and domain wall movement under bias attest to the true ferroelectric nature of the detected nanodomains. The systematic analysis of local piezoresponse loop arrays reveals a totally unexpected thickness dependence of the coercive fields in HZO capacitors. The thickness decrease from 10 to 7 nm is associated with a remarkably strong decrease of the coercive field, with about 50% of the capacitor area switched at coercive voltages ≤0.5 V. Our explanation consistent with the experimental data involves a change of mechanism of nuclei-assisted switching when the thickness decreases below 10 nm. The practical implication of this effect is a robust ferroelectric switching under the millivolt-range driving signal, which is not expected for the standard coercive voltage scaling law. These results demonstrate a strong potential for further aggressive thickness reduction of HZO layers for low-power electronics.

Interaction of a Supernova with a Circumstellar Disk

Abstract Interaction between a supernova (SN) ejecta and a dense circumstellar medium (CSM) can power a luminous light curve and create narrow emission lines in the spectra. While theoretical studies of interaction often assume a spherically symmetric CSM, there are observational indications that the gas surrounding some SNe has a disk-like geometry. Here, we use moving-mesh hydrodynamics simulations to study the interaction of an SN with a disk and determine how the dynamics and observable signatures may depend on the disk mass, thickness, and radial extent. We find that simple modifications to standard spherically-symmetric scaling laws can be used to describe the propagation and heating rate of the interaction shock. We use the resulting shock heating rates to derive approximate bolometric light curves, and provide analytic formulas that can be used to generate simple synthetic light curves for general supernova-disk interactions. For certain disk parameters and explosion energies, we are able to produce luminosities akin to those seen in super-luminous SNe. Because the SN ejecta can flow around and engulf the CSM disk, the interaction region may become embedded and, from certain viewing angles, the narrow emission lines indicative of interaction may be hidden.

The Taurus Boundary of Stellar/Substellar (TBOSS) Survey. II. Disk Masses from ALMA Continuum Observations

Abstract We report 885 μm ALMA continuum flux densities for 24 Taurus members spanning the stellar/substellar boundary with spectral types from M4 to M7.75. Of the 24 systems, 22 are detected at levels ranging from 1.0 to 55.7 mJy. The two nondetections are transition disks, though other transition disks in the sample are detected. Converting ALMA continuum measurements to masses using standard scaling laws and radiative transfer modeling yields dust mass estimates ranging from ∼0.3 to 20 M ⊕. The dust mass shows a declining trend with central object mass when combined with results from submillimeter surveys of more massive Taurus members. The substellar disks appear as part of a continuous sequence and not a distinct population. Compared to older Upper Sco members with similar masses across the substellar limit, the Taurus disks are brighter and more massive. Both Taurus and Upper Sco populations are consistent with an approximately linear relationship in M dust to M star, although derived power-law slopes depend strongly upon choices of stellar evolutionary model and dust temperature relation. The median disk around early-M stars in Taurus contains a comparable amount of mass in small solids as the average amount of heavy elements in Kepler planetary systems on short-period orbits around M-dwarf stars, with an order of magnitude spread in disk dust mass about the median value. Assuming a gas-to-dust ratio of 100:1, only a small number of low-mass stars and brown dwarfs have a total disk mass amenable to giant planet formation, consistent with the low frequency of giant planets orbiting M dwarfs.

Field-emission enhanced breakdown in oxygen microdischarges from direct-current to radio-frequencies

This paper reports on experimental studies of the breakdown mechanism in oxygen microdischarges generated in static and time-varying electric fields, up to radio-frequencies. Measurements were performed by using electrodes with round edges separated by a distance ranging between and , with the gas pressure from 7.5 Torr to 700 Torr. It is shown that the breakdown voltage does not obey standard scaling law for gaps of the order of a few microns for both direct current and alternating fields. A high electric field obtained in small gaps may enhance the secondary electron emission leading to the lowering of the breakdown voltage and departure from the standard scaling law. With increasing the gap size, the breakdown voltage increases since the contribution of field emission progressively reduces. Based on the breakdown voltage curves, the yields corresponding to the secondary electron production have been estimated. The threshold for field emission determined from our experimental data agree well with the value from the literature.

Investigation of Offshore Fault Modeling for a Source Region Related to the Shakotan-Oki Earthquake

The purpose of this study is to verify fault modeling in the source region of the 1940 Shakotan-Oki earthquake using active faults offshore of Japan. Tsunami heights simulated in previous studies are found to be lower than observed levels, which makes it difficult to explain historical tsunami records of this earthquake. However, the application of appropriate slip magnitudes in the fault models may explain these differences. In the “Project for the Comprehensive Analysis and Evaluation of Offshore Fault Informatics (the Project),” a new fault model is constructed using marine seismic data and geological and geophysical data compiled by the Offshore Fault Evaluation Group, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) as part of the Project for Fault Evaluation in the Seas around Japan (Ministry of Education, Culture, Sports, Science and Technology, MEXT). Single-channel and multichannel reflection seismic data were used that includes information from a new fault identified in previous surveys. We investigated fault geometries and their parameters using the above data. Here, we show that the geometric continuity of these faults is adjusted by increasing the magnitude of fault slip. Standard scaling laws are applied on the basis of strong ground motion of the fault parameters, and the validity of the fault model is examined by comparing tsunami heights along the Japanese coastline from historically observed records with tsunami height from simulation analysis. This verification quantitatively uses Aida’s K and κ scale and variance parameters. We determine that the simulated tsunami height determined using the new model approach the heights observed historically, which indicates that the model is valid and accurate for the source region.

Creep and thermal rounding close to the elastic depinning threshold.

We study the slow stochastic dynamics near the depinning threshold of an elastic interface in a random medium by solving a particularly suited model of hopping interacting particles that belongs to the quenched-Edwards-Wilkinson depinning universality class. The model allows us to compare the cases of uniformly activated and Arrhenius activated hops. In the former case, the velocity accurately follows a standard scaling law of the force and noise intensity with the analog of the thermal rounding exponent satisfying a modified "hyperscaling" relation. For the Arrhenius activation, we find, both numerically and analytically, that the standard scaling form fails for any value of the thermal rounding exponent. We propose an alternative scaling incorporating logarithmic corrections that appropriately fits the numerical results. We argue that this anomalous scaling is related to the strong correlation between activated hops that, alternated with deterministic depinning-like avalanches, occur below the depinning threshold. We rationalize the spatiotemporal patterns by making an analogy of the present model in the near-threshold creep regime with some well-known models with extremal dynamics, particularly the Bak-Sneppen model.

Fundamental Properties of the High Pressure Hydrogen Microdischarges in Static and Time-Varying Electric Fields

In this paper, the results of measurements of the characteristics of the hydrogen microdischarges from direct current to radio frequencies are presented and discussed. Two types of the electrode configurations are used: electrodes with Bruce profile and glass melting electrodes separated between 2.5 and ${\mathrm{ 100~\mu m}}$ . The breakdown voltage values for low frequencies are similar to the direct current breakdown voltage data, while the high-frequency breakdown voltages are systematically lower. As the frequency increases, the breakdown voltage decreases in the case of glass melting electrodes and increases in the case of electrodes with Bruce profile. It is observed that the breakdown voltages that correspond to the melting glass electrodes are lower due to edge issues and inability to achieve a homogenous field. The effective yields estimated from the measured breakdown voltage curves are similar for both electrode configurations. In addition to the breakdown voltage curves and current–voltage waveforms, the images demonstrating the discharge development and propagation are also recorded. Presented results reveal that secondary electrons play an essential role in sustaining the discharge in microgaps, where the relationship between breakdown voltage and gap spacing is far away from the standard scaling law at atmospheric pressure.

Bidirectional air turbines for oscillating water column systems: Fast selection applying turbomachinery scaling laws

The collector of an oscillating water column system (OWC) for wave energy utilization requires a bidirectional turbine that copes with pneumatic power while providing specified impedance or, in terms of an OWC designer, “damping”. Damping is realized by keeping to a specific flow rate through the turbine at a given pressure head due to the individual performance characteristic of the turbine. With the number of turbine designs increasing designers of OWC systems are facing more options to select and dimension a bidirectional turbine. Energy yield, size and hence cost of the turbine and electric generator, operational behaviour, envisaged control strategy and noise emitted by the turbine are possible criteria for selection.The primary objective of this paper is to describe a simple procedure for making a first choice of a turbine for a particular OWC application. Here we confine ourselves to a family of reaction type of turbines (axial-flow Wells and mixed-flow turbines by Moisel) with their approximately linear pressure head/volume flow rate characteristics. Starting point is the set of non-dimensional steady-state characteristics of each turbine in the family. Utilizing standard scaling laws and a very simple time domain model for the cyclic turbine operation (i.e. based one single sea state and turbine operation assumed to be fixed rotational speed), first estimates of turbine size and rotor speed, number for stages or flows, and performance curves can be determined. The resulting turbine may also serve as a starting configuration for a refined analysis, e.g. the optimization of the turbine and the complete OWC system, utilizing more complex stochastic models. Three case studies illustrate the application of the method: selection and scaling of turbines, effect of collector parameters, turbines in series and parallel.

Breakdown and dc discharge in low-pressure water vapour

In this paper we report studies of basic properties of breakdown, low-current Townsend discharge and high-current discharge regimes in water vapour. Paschen curves and the corresponding distributions of emission intensities at low current were recorded in the range of pd (pressure x electrode gap) from 0.1 to 10 Torrcm covering the region of Paschen minimum. From the experimental profiles we obtained effective ionization coefficient of water vapour for the E/N range 650 Td–7 kTd and fitted the results by using the extended Townsend analytical formula. Using the obtained ionization coefficient, we calculated the effective yield of secondary electrons from the copper cathode. Results of the measurements of Volt-Ampere characteristics in water vapour were presented together with the images of the axial structure of the discharge in a wide range of discharge currents for two pd values. Recorded profiles showed development of the spatial structure of the discharge in different operating regimes. We were able to identify conditions where processes induced by heavy particles, probably fast hydrogen atoms, are dominant in inducing emission from the discharge. Finally, standard scaling laws were tested for low current and glow discharges in water vapour.

Power Laws Variance Scaling of Boolean Random Varieties

Long fibers or stratifed media show very long range correlations. These media can be simulated by models of Boolean random varieties and their iteration. They show non standard scaling laws with respect to the volume of domains K for the variance of the local volume fraction: on a large scale, the variance of the local volume fraction decreases according to power laws of the volume of K. The exponent is equal to (n-k)/ n for Boolean varieties with dimension k in the space Rn : 2/3 for Boolean fibers in 3D, and 1/3 for Boolean strata in 3D. When working in 2D, the scaling exponent of Boolean fibers is equal to 1/2. From the results of numerical simulations, these scaling laws are expected to hold for the prediction of the effective properties of such random media.