Decoupling Parameter Research Articles

Concerning the Parameterization of Geometric and Criticality Effects on Detonation Amplification

This study investigates the role of geometric effects and detonation criticality on the behavior of a detonation transition through an area expansion of finite length. Three reinitiation behaviors that result in an amplified pressure impulse were observed and are referred to as steady, spike, and endwall amplification. Steady amplification was characterized by an amplification event with a peak pressure impulse 2 times that of the inlet detonation, followed by a near-linear attenuation toward Chapman–Jouguet conditions. Spike amplification displayed a larger peak pressure amplification that was 3 to 5 times greater than the inlet detonation, followed by a rapid and nonlinear attenuation. Endwall behavior represents a Craven–Grieg deflagration to detonation transition scenario. These behaviors are shown to be factors of area expansion ratio and the degree to which the incoming detonation is subcrtical. A decoupling parameter, Ψd, was devised to combine these effects into a single correlation metric. The finite length of the expansion chamber also plays a role in the reinitiation behavior as observed by the endwall reinitiation behavior. A critical chamber length parameter was devised to explain this behavior and then theorized to have a relationship to Ψd with this being explored theoretically and with the limited data set available.

Multivariate analysis of nanoparticle translocation through a nanopore to improve the accuracy of resistive pulse sensing.

The advent of nanopore-based sensors based on resistive pulse sensing gave rise to a remarkable breakthrough in the detection and characterization of nanoscale species. Some strong correlations have been reported between the resistive pulse characteristics and the particle's geometrical and physical properties. These correlations are commonly used to obtain information about the particles in commercial devices and research setups. The correlations, however, do not consider the simultaneous effect of influential factors such as particle shape and off-axis translocation, which complicates the extraction of accurate information from the resistive pulses. In this paper, we numerically studied the impact of the shape and position of particles on pulse characteristics in order to estimate the errors that arise from neglecting the influence of multiple factors on resistive pulses. We considered the sphere, oblate, and prolate particles to investigate the nanoparticle shape effect. Moreover, the trajectory dependency was examined by considering the translocation of nanoparticles away from the nanopore axis. Meanwhile, the shape effect was studied for different trajectories. We observed that the simultaneous effects of influential parameters could lead to significant errors in estimating particle properties if the coupled effects are neglected. Based on the results, we introduce the "pulse waveshape" as a novel characteristic of the resistive pulse that can be utilized as a decoupling parameter in the analysis of resistive pulses.

Elucidating the Magnetoelastic Coupling, Pressure-Dependent Magnetic Behavior, and Anomalous Hall Effect in FexTi2S4 Intercalation Sulfides.

Transition-metal chalcogenides with intercalated layered structures are interesting systems in material physics due to their attractive electronic and magnetic properties, with applications in the fields of magnetic refrigerators, catalysts, and thermoelectrics, among others. In this work, we studied in detail the structural, electronic, and magnetic properties of (Fe,Ti)-based sulfides with formula FexTi2S4 (x = 0.24, 0.32, and 0.42), prepared as polycrystalline materials under high-pressure conditions. They present a layered Heideite-type crystal structure, as assessed by synchrotron X-ray diffraction. A local structure analysis using Fe K-edge extended X-ray-absorption fine structure (EXAFS) data unveiled a conspicuous contraction of the main Fe-S bond in Fe0.24Ti2S4 at the vicinity of the magnetic transition 60-80 K. We suggest that this anomaly is related to magnetoelastic coupling effects. The EXAFS analysis allowed extraction of the Einstein temperatures (θE), i.e., the phonon contribution to the specific heat, for the two bond pairs Fe-S(1) [θE ≈318 K; 290 K (C/T)] and Fe-Ti(1) [θE ≈218 K; 190 K (C/T)]. In addition to the structural and local vibrational measurements, we probed the magnetic properties using magneto-calorimetry, magnetometry under applied pressure, magnetoresistance (MR), and Hall effect measurements. We observed the appearance of a broad peak in the specific heat around 120 K in the x = 0.42 compound that we associated with an antiferromagnetic ordering electronic transition. We found that the antiferromagnetic transition temperature is pressure and composition sensitive and reduces at 1.2 GPa by ∼12 and ∼3 K, for the members with x = 0.24 and x = 0.42, respectively. Similarly, the saturation magnetization in the ordered phase depends on both pressure and iron content, reducing its value by 50, 90, and 30% for x = 0.24, 0.32, and 0.42, respectively. We observed clear jumps in the magnetic hysteresis loops, MR, and anomalous Hall effect (AHE) below 2 K at fields around 2-4 T. We associated this observation with the metamagnetic transitions; from the Berry-curvature a decoupling parameter of SH = 0.12 V-1 is determined. Comparison of the results on the temperature-dependent magnetization, MR, and AHE elucidates a strong inelastic scattering contribution to the AHE at higher temperatures due to the cluster spin-glass phase.

Effects of charge and gravitational decoupling on complexity and isotropization of anisotropic models

This paper constructs two immediate extensions of the existing anisotropic solutions in the context of Einstein–Maxwell framework by employing minimal geometric deformation. To achieve this, we assume a static spherical interior initially filled with anisotropic fluid and call it a seed source. We extend this matter configuration by including a new source whose impact on the self-gravitating system is governed by a decoupling parameter. The charged field equations analogous to the total fluid source are formulated. We then implement a transformation on the radial metric potential that divides the field equations into two new under-determined systems, corresponding to the initial and new sources. The first of them is addressed by taking two well-known metric ansatz so that the number of unknowns can be tackled. Further, the vanishing of total anisotropy and complexity-free constraints are used to solve the second set. The estimated radius and mass of a compact star 4U1820−30 is utilized to interpret the resulting solutions graphically for different values of the charge and decoupling parameter ω. We conclude that our both developed models are physically acceptable for all parametric values except ω=1.

Complexity‐Free Anisotropic Solution of Buchdahl's Model and Energy Exchange Between Relativistic Fluids by Extended Gravitational Decoupling

AbstractIn this work, we present an anisotropic generalization of the Buchdahl static stellar model by implementing the method of extended gravitational decoupling and further requirement of vanishing complexity (Herrera, Phys Rev D 97:044010,2018). Starting off with a general spherically symmetric static metric with two unknown gravitational potentials, we impose the condition of vanishing complexity which then reduces the problem to a single‐generating metric function [Contreras and Stuchlik, Eur. Phys. J. C (2022) 82:706]. The Buchdahl ansatz is then employed to obtain the complete gravitational behavior of the isotropic seed solution. The method of extended gravitational decoupling is thereafter utilized to obtain an anisotropic counterpart of the Buchdahl perfect gravitating sphere. We subject our solution to rigorous physical tests to ensure that it serves as a viable candidate for compact objects such as neutron stars as well as pulsars. We show that the decoupling parameter plays a crucial role in determining the stability and regularity of several key physical features of the entire stellar model. A novel finding of our investigation is the energy exchange between the seed solution and the secondary source which we show is sensitive to the decoupling parameter. In addition, it has also been shown that the direction of energy flow depends on the radial distance of the shell from the center of the stellar configuration.

Gravitational decoupling, hairy black holes and conformal anomalies

Hairy black holes in the gravitational decoupling setup are studied from the perspective of conformal anomalies. Fluctuations of decoupled sources can be computed by measuring the way the trace anomaly-to-holographic Weyl anomaly ratio differs from the unit. Therefore the gravitational decoupling parameter governing three hairy black hole metrics is then bounded to a range wherein one can reliably emulate AdS/CFT with gravitational decoupled solutions, in the tensor vacuum regime.

Revisiting Daily MODIS Evapotranspiration Algorithm Using Flux Tower Measurements in China

AbstractEvapotranspiration (ET) is the major component of the hydrology cycle. Satellites provide a convenient way for gathering information to estimate regional ET. The most widely applied method for converting the instantaneous satellite measurement to daily scale assumes that evaporative fraction (EF), defined as the ratio of ET to the available energy, is constant during the daytime. However, this method was proved to underestimate the daily ET. This study implemented a theoretically improved EF algorithm to calculate daily ET with the decoupling factor method based on the Penman‐Monteith and McNaughton‐Jarvis equations. Seven improved algorithms were developed by assuming that various parameters remain constant during the day. The satellite‐based ET estimates were compared with seven local flux tower measurements in China. The results showed that: (a) The original ET method calculated the daily evaporation more accurately than the other algorithms. However, the good fit was based on two compensating inaccuracies. Compared to the flux tower measurement, the original ET method underestimated the daily EF by 26% and overestimated the daily net radiation by 30%. (b) Six of the seven proposed algorithms underpredicted the daily ET by 30%–60%, mainly due to the inaccurate daily net radiation. (c) The algorithm that assumed that the instantaneous decoupling parameter was equal to its daily value method calculated EF and ET with relative errors of 8% and 10% separately when the inaccurate estimated daily net radiation was replaced by the observed flux tower data.

Gravitational decoupling and superfluid stars

The gravitational decoupling is applied to studying minimal geometric deformed (MGD) compact superfluid stars, in covariant logarithmic scalar gravity on fluid branes. The brane finite tension is shown to provide more realistic values for the asymptotic value of the mass function of MGD superfluid stars, besides constraining the range of the self-interacting scalar field, minimally coupled to gravity. Several other physical features of MGD superfluid stars, regulated by the finite brane tension and a decoupling parameter, are derived and discussed, with important corrections to the general-relativistic limit that corroborate to current observational data.

A Dynamic Bayesian Network Control Strategy for Modeling Grid-Connected Inverter Stability

The dynamic performance of a grid-connected inverter in a distributed generation system brings new challenges by affecting the power quality and dynamic stability. The traditional linear control method for the inverter requires complex processes including decoupling and control parameter tuning and relies on a pulsewidth modulation module. The nonlinear control method, e.g., the model predictive control (MPC), can address some of the aforementioned challenges but is incapable of dealing with system parameter changes. A data-driven method using the dynamic Bayesian network-based model predictive control (DBN-MPC) is proposed, which takes advantage of the predictive ability of the DBNs to implement the MPC strategy. A predictive model is built, and the prediction signals are generated based on the DBNs. Then, by constructing the cost function and optimization criteria, the controller generates the optimal switching state combination. Using the proposed DBN-MPC method, the predictive model implements parameter learning online, providing more accurate prediction signals for further optimization and the feedback correction. In addition, the control law of the proposed controller can update over time, which enables the grid-connected inverter system to achieve the optimal control. The case studies using the grid-connected inverter system and IEEE 39-bus benchmark power system integrated with the battery energy storage system demonstrate and verify the superiority of the proposed DBN-MPC method.

Magnetic properties of K = 1/2 states in deformed odd-mass nuclei

A method for calculation of the ground-state magnetic moment, effective spin gyromagnetic factors and rotational decoupling parameter of the K=1/2 states in deformed odd-mass nuclei has been described by using the concept of the Quasiparticle Phonon Nuclear Model (QPNM). The model includes a Woods-Saxon potential as a mean field with pairing correlations and the residual separable spin-spin force in both isovector and isoscalar channels. The method has been employed to investigate K=1/2 ground-state magnetic properties of 169Er, 167,169Tm, and 171Yb nuclei, as an example. It has been shown that two different quenched spin gyromagnetic factors, i.e., gsz(eff.) and gs+(eff.) have a significant effect on the magnetic properties of K=1/2 states in odd-mass nuclei. Whereas the first one is occurred due to the interaction between the valence nucleon and IπK=1+0 excitations of the core, second one is associated with the coupling of the valence nucleon to IπK=1+1 excitations of the core. The observed magnetic moments and the phenomenological value of gsz(eff.) for considered odd-mass nuclei have been reproduced very well by the calculations. The role of the isoscalar and isovector interactions on the magnetic properties of K=1/2 states in these nuclei has been also discussed.

Isolating the Effects of Moisture Entrainment on Convectively Coupled Equatorial Waves in an Aquaplanet GCM

Abstract The rate of humidity entrainment in the convective parameterization scheme in a general circulation model affects the simulation of convectively coupled waves. However, it is unclear whether this is caused directly by the effects of entrainment on waves or indirectly through associated impacts such as on the basic state. Therefore, using an aquaplanet model, we employ a novel framework in which we entrain a weighted average of the resolved humidity field and a prescribed zonally symmetric field, with the weighting controlled by a decoupling parameter. Hence, we can vary the entrainment rate of basic-state humidity independently of the entrainment of humidity perturbations, simultaneously minimizing changes in the basic state. Thus, we isolate the effect of moisture entrainment on the waves. Enhancing the entrainment rate increases spectral power over all zonal wavenumbers and frequencies, with an increase in the ratio of eastward-to-westward power. The Kelvin wave speed decreases as entrainment increases, which can be partially accounted for by an associated change in basic-state humidity. Increasing the decoupling parameter reduces spectral power in Kelvin waves relative to the background, with only long waves still prominent when entrainment is almost fully decoupled from the resolved moisture field, suggesting the wave structure in humidity is required for convection to organize into short-wave structures. For long waves, the increase in the ratio of eastward-to-westward power as entrainment rate increases cannot be explained by the changes in the coupling with the wave structure in humidity but is consistent with the changes in the basic state.

Biophysical Factors and Canopy Coupling Control Ecosystem Water and Carbon Fluxes of Semiarid Sagebrush Ecosystems

The sagebrush-steppe ecosystem covers much of western North America, and its productivity is sensitive to warming and increasingly variable precipitation. Interannual variation in precipitation has been shown to be the most significant factor controlling biogeochemical cycling while both soil and atmospheric drought are dominant factors of ecosystem fluxes. We show that plant canopies can also act to limit water losses through stomatal and aerodynamic control. We use 4 data-yr from 2 sites (2 069 and 2 469 m above sea level elevation, respectively) to evaluate control of carbon and water fluxes and to calculate the degree to which the ecosystem canopy and atmosphere are decoupled. Environmental conditions were similar between the two sites, although the lower elevation site was slightly warmer (1.8°C higher temperature) and drier (0.2 kPa higher vapor pressure deficit). Ecosystem responses of net ecosystem exchange (NEE) and evapotranspiration (ET) to environmental drivers were similar between sites and years, with the wet site-yr 2009 having the largest ET and NEE fluxes. Canopy leaf area led to divergent behavior of the canopy-atmosphere decoupling parameter under high (> 11% by volume) soil moisture conditions. During low (< 11%) soil moisture periods, both sites had tight ecosystem stomatal control on ET with little NEE activity. This study highlights how semiarid ecosystems can alter their canopy leaf area in order to control how decoupled semi-arid canopies are to the atmosphere, potentially moderating impacts of climate change.

Crystal growth and viscous flow in barium disilicate glass

Decoupling between the diffusion coefficients that control crystal growth (DU) and viscous flow (Dη) in deeply supercooled glass-forming liquids is one of the most celebrated, still unsolved, phenomena in glass science because it strongly impacts the analysis and prediction of crystallization kinetics. To further understand the decoupling phenomenon, we measured viscosity and crystal growth rates (of the crystalline surface layer growth and internally nucleated crystals) of a supercooled liquid with barium disilicate composition. We performed all measurements using glass samples from the same batch, a rare case that we call a “clean” experiment. This type of analysis is uncommon, and its aim is to minimize the uncertainty due to the composition variation that is inherent in laboratory glass production. The decoupling temperature (Td), the glass transition temperature (Tg), the melting point (Tm), and the liquid fragility index were obtained and successfully used to test a recently derived relationship which allows one to estimate Td by knowing only Tm and the viscosity curve. We also show, for the first time, that the reduced decoupling parameter, which gauges the degree of deviation between DU and Dη, does not depend on the crystal growth mechanism for the cases of Normal or Screw Dislocation growth.

On the aerodynamic redistribution of chondrite components in protoplanetary disks

Despite being all roughly of solar composition, primitive meteorites (chondrites) present a diversity in their chemical, isotopic and petrographic properties, and in particular a first-order dichotomy between carbonaceous and non-carbonaceous chondrites. We investigate here analytically the dynamics of their components (chondrules, refractory inclusions, metal/sulfide and matrix grains) in protoplanetary disks prior to their incorporation in chondrite parent bodies. We find the dynamics of the solids, subject to gas drag, to be essentially controlled by the “gas–solid decoupling parameter”S≡St/α, the ratio of the dimensionless stopping time to the turbulence parameter. The decoupling of the solid particles relative to the gas is significant when S exceeds unity. S is expected to increase with time and heliocentric distance. On the basis of (i) abundance of refractory inclusions, (ii) proportion of matrix, (iii) lithophile element abundances, and (iv) oxygen isotopic composition of chondrules, we propose that non-matrix chondritic components had S<1 when carbonaceous chondrites accreted and S>1 when the other chondrites accreted. This suggests that accretion of carbonaceous chondrites predated on average that of the other chondrites and that refractory inclusions are genetically related to their host carbonaceous chondrites.

Approximate analysis and design of rectangular-lattice photonic crystals.

We present a theoretical analysis of wave propagation in rectangular- and square-lattice photonic crystals by approximating the arbitrary refractive-index function with a staircase profile. This profile has a number of tunable parameters that allow one to fit the band structures of the staircase and the desired structure over a large frequency range. The staircase profile is such that its corresponding two-dimensional wave equation decomposes into two one-dimensional equations by means of a constant decoupling parameter. We show that basic features of the band structure and Bloch waves in photonic crystals can be analyzed theoretically through this simple approximation.

Surface resistance of grain-aligned YBa2Cu3Ox bulk: Evidence for two kinds of weak link.

We have measured the magnetic-field and temperature dependence of the surface resistance ${\mathit{R}}_{\mathit{s}}$ of grain-aligned ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$. Experiments were conducted on ab-plane- and ac-plane-oriented samples, with the dc magnetic field parallel and perpendicular to the sample surface. We explain the nonlinear behavior of ${\mathit{R}}_{\mathit{s}}$ at low field using a model with an array of Josephson weak links and the linear dependence on magnetic field at high field using an oscillatory-vortex-motion-loss model. The model allows a quantitative fit to the experimental data using the lower critical field of the grain, the entry field ${\mathit{H}}_{\mathit{c}1\mathit{J}}$ of weak links, the junction decoupling parameter ${\mathit{H}}_{\mathit{d}}$, and the vortex viscosity as fitting parameters. Two different sets of parameters ${\mathit{H}}_{\mathit{d}}$ and ${\mathit{H}}_{\mathit{c}1\mathit{J}}$ were used to fit the data, suggesting that in grain-aligned ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$ bulk material at least two kinds of weak link are responsible for low-field losses. An estimation of the Josephson-junction area was obtained from field-modulated microwave absorption. In addition, thermal-excitation and radiation-activation mechanisms for rf losses are compared.

The alpha decay study of223Th (T 1/2=0.6 s)

The219Ra levels, fed by the α-decay of223Th, have been studied by anα−γ coincidence experiment. AK=1/2+ band, based on the 7/2+ ground state, with a large decoupling parameter a=−5.5 is proposed. Three levels with spins 5/2, 9/2, 7/2 and lowα-hindrance factors around 140 keV, can be considered as members of aK=5/2+ band, perturbed by the Coriolis coupling of configurations arising from theg9/2 shell. TheseK =1/2+ and 5/2+ orbitals are expected forN=131 in the reflection asymmetry model with ɛ2≃ɛ3−0.1. How-ever no evidence was found for the corresponding negative parity bands in this transitional nucleus.

Local decoupling of a bunch of resonances and associated trapping effect

The model or effective Hamiltonian theory is used in order to find the conditions for which a clump of quasi-degenerate levels indirectly coupled to external states via continua can be treated as a decoupled degenerate band. The usual measure of the overlap Γ/Δ E is not sufficient and a decoupling parameter α related to the off-diagonal elements of the width matrix Γ is introduced. When the approximation is valid, the coupling of N D exactly degenerate discrete states to K decay channels is known to provide a trapping effect: N D - K states remain bound states even though thier energy is above the dissociation threshold. It is demonstrated that this result is independent of the indirect coupling with external states. However, the degeneracy breaking inside the clump slightly distorts the trapping leading to N D - K slow decay modes. When the decoupling is not valid, the two perturbations (external coupling and degeneracy breaking inside the band) act in an opposite manner on the fluctuations of the widths. The external coupling increases the dispersion of the widtsh while the splitting of the levels decreases it.

The nuclear magnetic moments of184,185Ir and the quadrupole moment of185Ir

Nuclear magnetic resonance measurements have been performed for 184IrFe and 185IrNi at low temperatures of 7 and 16 mK. The quadrupole splitting could be resolved for the 185IrNi sample but not for the 184IrFe sample. The analysis of the 184IrFe data was done using the known quadrupole moment. With the hyperfine field of BIIF(IrFe)=-1373(7) kG and BIIF(IrNi)=-454.7(23) kG and the electric field gradient of eq(IrFe)=-0.283(6)*1017 V cm-2 and eq(IrNr)=-0.151(4)*1017 V cm-2, the magnetic moment of 184,185Ir and the quadrupole moment of 185Ir were deduced: mod mu (184Ir, 5) mod =0.696(5) mu N, mod mu (185Ir, 5/2-) mod =2.605(13) mu N and Q(185Ir, 5/2-)=-2.06(14) b. The properties of 185Ir could be explained in terms of an effective decoupling parameter and the (5/2-)(1/2)(541) Nilsson configuration.

Decay of 145Cs to levels of 145Ba.

An investigation of the ..beta../sup -/ decay of 0.59 s /sup 145/Cs into levels of /sup 145/Ba was undertaken to search for evidence of intrinsic reflection asymmetry in light rare-earth nuclei. E-italic/sub ..gamma../, I-italic/sub ..gamma../, ..gamma..-..gamma.. coincidence, angular correlation coefficients, and internal conversion coefficients were measured. The level scheme for /sup 145/Ba up to 1.3 MeV has been constructed. The proposed spin and parity assignments are based upon the measured transition multipolarities and the ..gamma..X(h-italicy-italic..gamma.. angular correlation coefficients. The levels at 112, 175, 277, and 416 keV may be members of a decoupled K-italic = 1/2/sup -/ band with a decoupling parameter of -2 and a rotational parameter of 20 keV. The octupole deformed rotational structure which is observed in the light odd-A-italic actinides is not readily identified in /sup 145/Ba.