Effective Radius Research Articles

ON THE IONIC RADIUS OF METHYLAMMONIUM IN HYBRID ORGANIC-INORGANIC PEROVSKITE PHASES

Hybrid organic-inorganic perovskites ABX3 usually contain an organic cation A and an inorganic matrix formed from coordination octahedra [BX6], where B is a metal and X is a halogen. Predicting the formation of hybrid perovskite phases and modeling their structural parameters requires basic knowledge of the effective sizes (ionic radii) of the constituent components; however, the previously proposed approach to estimate the effective ionic radius of a particular organic cation A based on its molecular geometry apparently does not correspond to the hard spheres model, within the framework of which the vast majority of ionic radii systems and the main criteria for assessing the stability of perovskite structures were developed. To independently estimate the effective ionic radius of methylammonium CH3NH3+, which is a component of a number of perovskite structures, a scheme for modeling the lattice parameter of halide cubic perovskites ABX3 was developed by using multiple linear regression analysis based on the effective ionic radii of inorganic components with the corresponding coordination numbers intrinsic for perovskites. Using the found direct and inverse correlations between the effective ionic radius of the cation A and the cubic lattice parameter of perovskite, as well as numerical data of the lattice parameters of the known cubic hybrid perovskite phases (CH3NH3)PbCl3 and (CH3NH3)PbBr3, the value of the effective ionic radius of methylammonium CH3NH3+ was first estimated as ~1.9 Å, which is significantly different from the value of 2.17 Å obtained within the framework of the approach based on the molecular geometry.

Effective radius of a contact diffusion-controlled reaction between small solutes and a polymer chain.

The aim of this study was to develop a formula for estimating the effective radius of a diffusion-controlled irreversible contact reaction between diffusing solutes and a nonlinear immobile polymer molecule. Analytical expressions for the reaction radius were obtained that took into account averaging over conformations for chains with arbitrary segment-to-segment angles and distributions of dihedral angles. A comparison of the analytical results with the results of computer stochastic modeling of the reaction showed good agreement over a wide range of parameters. Based on an analysis of these expressions, parameter ranges were established in which it was possible to use either the linear chain or Gaussian coil approximation to describe the reaction kinetics. A comparison of several distributions over chain lengths showed that, as a first approximation, the radius of reaction can be estimated as that for a chain corresponding to the number-averaged molecular weight. Results of earlier experimental studies on charge scavenging by polymer molecules have been explained.

The Small Sizes and High Implied Densities of “Little Red Dots” with Balmer Breaks Could Explain Their Broad Emission Lines without an Active Galactic Nucleus

Abstract Early JWST studies found an apparent population of massive, compact galaxies at redshifts z ≳ 7. Recently three of these galaxies were shown to have prominent Balmer breaks, demonstrating that their light at λ rest ∼ 3500 Å is dominated by a stellar population that is relatively old (∼200 Myr). All three also have broad Hβ emission with σ > 1000 km s−1, a common feature of such “little red dots.” From Sérsic profile fits to the Near Infrared Camera images in F200W we find that the stellar light of galaxies is extremely compact: the galaxies have half-light radii of r e ∼ 100 pc, in the regime of ultracompact dwarfs in the nearby Universe. Their masses are uncertain, as they depend on the contribution of possible light from an active galactic nucleus (AGN) to the flux at λ rest > 5000 Å. If the AGN contribution is low beyond the Balmer break region, the masses are M * ∼ 1010–1011 M ☉, and the central densities are higher than those of any other known galaxy population by 1 order of magnitude. Interestingly, the implied velocity dispersions of ∼1500 km s−1 are in very good agreement with the measured Hβ line widths. We suggest that some of the broad lines in “little red dots” are not due to AGNs, but simply reflect the kinematics of the galaxies, and speculate that the galaxies are observed in a short-lived phase where the central densities are much higher than at later times. We stress, however, that the canonical interpretation of AGNs causing the broad Hβ lines also remains viable.

Thermo-hydraulic performance inside convergent rectangle channel with large-deformed dimples

The cooling technology of convergent rectangle channel is widely applied in heat exchangers, electronic devices and aerospace, especially in the field of turbine blade internal cooling.A numerical study was conducted to research the thermo-hydraulic performance inside a convergent rectangle channel with large-deformed dimples. The heat transfer and flow characteristics were presented to demonstrate the heat transfer enhancement mechanism. The effect of dimple configuration, dimple depth, and dimple radius on thermo-hydraulic performance were discussed at Reynolds numbers ranging from 15,000 to 65,000. The numerical results revealed that the large-deformed dimple structure disrupts the boundary layer flow, resulting in better mixing between the boundary layer flow and the core fluid. The dimple configuration of diminishing dimples showed better heat transfer performance and lower pressure loss. The Nusselt number ratio, friction factor ratio, and performance evaluation criteria (PEC) increase with rising dimple depth and dimple radius. Within the scope of the present work, the maximum PEC was 1.62 when the dimple configuration was diminishing, the dimple depth was 5mm, and the dimple radius was 10mm.

Field shaper-based solutions to the bulging problem in magnetic pulse spot welding of dissimilar metal plates

Magnetic pulse spot welding based on a field shaper can effectively achieve spot welding of dissimilar metal plates by using the multi-turn flat coil and magnetic gathering through the field shaper. Through existing experimental research, it has been found that when using this method for welding, there will be a serious bulging problem in the center of the welding area, which will affect the flatness and aesthetics of the welding area, thereby affecting its application range. To solve this problem, this work proposes two different welding methods for welding dissimilar AA1060 aluminum and SS304 steel plates with a thickness of 1 mm: one based on the center opening of the flying plate and the other based on the pre-deformation of the flying plate. The causes of bulging and the effects of discharge voltage, welding gap, and inner hole radius of the field shaper on bulging size were studied. The cross-sectional morphology and mechanical properties of welded joints obtained by two welding methods were studied through numerical simulation, cross-sectional analysis, and tensile testing. The results indicated that both welding methods can successfully eliminate the bulging problem, and the point welding method based on the center opening of the aluminum plate can also reduce the minimum welding energy required for effective welding and improve welding efficiency. In addition, microscopic analysis results showed that a waveform composite interface was formed at the welding interface of the joint, and the connection performance of the welded joint was good. These two welding methods can also be extended to the welding of other dissimilar metal plates, which is of great significance for the industrial application of magnetic pulse spot welding technology based on field shaper.

Comprehensive analysis of gas slippage and Non-Darcy flow in carbonate rock samples under stress conditions

This study examines the influence of stress on gas slippage and non-Darcy flow behavior in carbonate porous media, using core samples from two large carbonate reservoirs in the Middle East. Permeability measurements under varying stress conditions revealed significant increases in both the gas slippage factor and the non-Darcy coefficient with rising stress, indicating a related decrease in permeability. A new mathematical model, incorporating effective tortuosity and slippage radius into the Kozeny-Carman equation, was developed to accurately describe the stress-dependent nature of gas flow. Analysis of key pore attributes—such as porosity, pore size, shape, and tortuosity—underscored the critical role of pore structure, especially pore size and connectivity, in governing fluid flow under stress. These findings highlight the need to account for stress effects in reservoir engineering for improved modeling and management of carbonate reservoirs.

Eridanus III and DELVE 1: Carbon-rich Primordial Star Clusters or the Smallest Dwarf Galaxies?* *This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

We present spectroscopy of the ultra-faint Milky Way satellites Eridanus III (Eri III) and DELVE 1. We identify eight member stars in each satellite and place nonconstraining upper limits on their velocity and metallicity dispersions. The brightest star in each object is very metal poor, at [Fe/H] = −3.1 for Eri III and [Fe/H] = −2.8 for DELVE 1. Both of these stars exhibit large overabundances of carbon and very low abundances of the neutron-capture elements Ba and Sr, and we classify them as CEMP-no stars. Because their metallicities are well below those of the Milky Way globular cluster population, and because no CEMP-no stars have been identified in globular clusters, these chemical abundances could suggest that Eri III and DELVE 1 are dwarf galaxies. On the other hand, the two systems have half-light radii of 8 pc and 6 pc, respectively, which are more compact than any known ultra-faint dwarfs. We conclude that Eri III and DELVE 1 are either the smallest dwarf galaxies yet discovered, or they are representatives of a new class of star clusters that underwent chemical evolution distinct from that of ordinary globular clusters. In the latter scenario, such objects are likely the most primordial star clusters surviving today. These possibilities can be distinguished by future measurements of carbon and/or iron abundances for larger samples of stars or improved stellar kinematics for the two systems.

Cosmological Prediction of the Void and Galaxy Clustering Measurements in the CSST Spectroscopic Survey

The void power spectrum is related to the clustering of low-density regions in the large-scale structure (LSS) of the Universe and can be used as an effective cosmological probe to extract information on the LSS. We generate galaxy mock catalogs from a Jiutian simulation and identify voids using the watershed algorithm for studying the cosmological constraint strength of the China Space Station Telescope spectroscopic survey. The galaxy and void autopower spectra and void−galaxy cross-power spectra at z = 0.3, 0.6, and 0.9 are derived from the mock catalogs. To fit the full power spectra, we propose to use the void average effective radius at a given redshift to simplify the theoretical model, and we adopt the Markov Chain Monte Carlo technique to implement the constraints on the cosmological and void parameters. The systematic parameters, such as galaxy and void biases and noise terms in the power spectra, are also included in the fitting process. We find that our theoretical model can correctly extract the cosmological information from the galaxy and void power spectra, which demonstrates its feasibility and effectivity. The joint constraint accuracy of the cosmological parameters can be improved by ∼20% compared to that of the galaxy power spectrum only. The fitting results of the void density profile and systematic parameters are also well constrained and consistent with the expectation. This indicates that the void-clustering measurement can be an effective complement to the galaxy-clustering probe, especially for the next-generation galaxy surveys.

Advancing effective radius parameterizations in climate models: insights from fundamental theoretical studies and CMIP6 model

Advancing effective radius parameterizations in climate models: insights from fundamental theoretical studies and CMIP6 model

LDOS of electron pair and the role of the Pauli exclusion principle

The local density of states (LDOS) for a pair of non-relativistic electrons, influenced by repulsive Coulomb forces, is expressed in term of one-dimensional integrals over Whittaker functions. The computation of the electron pair's LDOS relies on a two-particle Green's function (GF), a generalization of the one-particle GF applicable to a charged particle in an attractive Coulomb potential. By incorporating electron spins and considering the Pauli exclusion principle, the resulting LDOS consists of two components: one originating from an exchange-even two-particle GF and the other from an exchange-odd two-particle GF. The calculated LDOS reveals its dependence on both inter-electron distance and energy. The pseudo-LDOS, derived from the two-body contribution to the LDOS, is examined. This term ensures complete LDOS suppression atr = 0, exhibiting a limited spatial extent, and the reasons for its emergence are elucidated. It is shown that for energies exceeding the effective Hartree energy and inter-electron distances beyond the effective Bohr radius, the impact of many-body contributions to the LDOS can be disregarded. The induced LDOS for an electron pair subjected to an attractive contact potential in two dimensions is evaluated. At small distancesafrom the potential center, a predicted relative difference in LDOS between even and odd state pair reaches approximately 8%. The calculated LDOS is compared with available experimental findings from a two-dimensional electron gas (2DEG). Both exhibit similar oscillation periods; however, the LDOS of the electron pair decays as1/a3, significantly faster than the1/adecay observed for free electrons in a 2DEG.

Triboplasma assisted chemical conversion in granular systems: a semi-analytic model

Abstract We present a semi-analytic model for a novel plasma-assisted chemical conversion pathway using triboplasmas generated in granular flows. Triboelectric charge relaxation is a well known phenomena where the potential generated from contact charging of particles exceeds the breakdown voltage of the background gas. In this work, we extend the triboelectric charge relaxation theory to include non equilibrium plasma energy and particle balance equations to predict the formation of dissociated and excited species that act as precursors to chemical conversion, for example in plasma-assisted ammonia synthesis. 
Our example case study with nitrogen background gas and Teflon/aluminum tribomaterial system yielded high excited nitrogen species densities per collision that are comparable to current plasma-assisted conversion pathways. We also present a regime diagram for various gases where Paschen breakdown parameters are used to determine whether triboplasmas can be formed for a given effective work-function difference between two materials. Our sensitivity studies indicate particle velocity, particle radius, solids fraction and space charge effects play a critical role in overall plasma densities and excited species production.

The Disk Reverberation Mapping of the Lensed Quasar Q0957+561

The measurement of continuum time lags in lensed quasars can effectively probe the accretion physics of quasars. This is because microlensing observations of lensed quasars can provide constraints on the half-light radii of quasar accretion disks. By combining the microlensing results with time lag measurements, one can, for the first time, estimate the propagation velocity of the physical process that drives interband time lags and cross correlations among disk emission (i.e., in UV/optical bands). In this study, we perform the disk reverberation mapping study for the well-studied lensed quasar, Q0957+561. The cross correlation between the Zwicky Transient Facility g and r bands was measured; the g variations lead the r ones by 6.4 ± 2.6 days in the rest frame. In combination with the half-light radius from the existing literature, we find that the propagation velocity of the variability mechanism should be 1.7−0.7+1.5 times the speed of light. We discuss the possible outcomes of this result. Similar studies can be applied to other lensed quasars by utilizing the Legacy Survey of Space and Time observations.

Modal analysis of PE pipeline under seabed dynamic pressure

This paper presents a modal analysis conducted under seabed dynamic pressure conditions. The polyethylene (PE) pipeline was approximated as a thin-walled long cylindrical shell. The impact of pressure on the pipeline structure was considered, the study investigated the circumferential dynamic characteristics. The natural characteristics of the structure were solved using the energy method. To validate the model, an experimental testing system was established to measure the natural frequencies of the polyethylene (PE) pipeline, capturing the first three natural frequencies and mode shapes of the structure. Additionally, we conduct a simulation analysis in COMSOL. The results showed that the discrepancies among the experimental, theoretical, and simulation results were within 6%, confirming the accuracy of the model. Building on this foundation, the simulation considered the impact of fluid-structure interaction on the natural frequencies of the cylindrical shell. Subsequently, the effects of pipe radius, pipe thickness, pipe length, variations in external load, and dimensionless parameters on the modal characteristics of the structure were further investigated. The comparison of simulation and theoretical results showed errors within 5%, further validating the reliability of the simulation outcomes.

Using shared-bike orders to investigate the dynamicity of park service radii: Evidence from Shenzhen

This study offers a novel approach for examining the variations of effective park service radius (PSR) in parks with different sizes (small, medium, and large parks) and temporal conditions (weekday morning–noon (M–N), weekday afternoon–evening (A–E), weekend M–N, and weekend A–E). Using Shenzhen as an example and employing shared-bike order data, a detection tool was developed to identify the effective PSRs of 228 sample parks under different spatiotemporal conditions. Analysis of variance (ANOVA) was used to investigate the variations in PSRs in parks of different sizes and periods and multiple linear regression models were built to investigate the influential mechanisms of PSRs for different sized parks. We found that: 1) the differences in the PSRs between medium and large parks were not statistically significant (p < 0.05), proving that the PSR did not increase stably with an increase in park size, and the gaps in PSRs between parks of different sizes were smaller than those of the values predefined in most planning codes; 2) the PSRs of different sized parks in all temporal conditions displayed statistically significant differences while only the PSRs of small parks demonstrated significant differences across different periods; 3) restaurants, water features, and attractions showed significant and positive effects on the PSR while sports fields and parking lots showed significant and negative effects on the PSR, and the influence of these factors differed significantly as park size varied. These findings can inform future decision-making and park planning in Shenzhen and other bike-friendly cities.

Cosmography from accurate mass modeling of the lens group SDSS J0100+1818: Five sources at three different redshifts

Systems where multiple sources at different redshifts are strongly lensed by the same deflector allow one to directly investigate the evolution of the angular diameter distances as a function of redshift, and thus to learn about the geometry of the Universe. We present measurements of the values of the total matter density, $ m $, and of the dark energy equation of state parameter, $w$, through a detailed strong lensing analysis of SDSS J0100+1818, a group-scale system at $z=0.581$ with five lensed sources, from $z=1.698$ to $4.95$. We take advantage of new spectroscopic data from the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope to securely measure the redshift of 65 sources, including the 5 multiply imaged background sources (lensed into a total of 18 multiple images) and 19 galaxies on the deflector plane, all employed to build robust strong lensing models with the software GLEE . The total mass distribution of the deflector is described in a relatively simple way, and includes an extended halo, the brightest group galaxy (BGG) with a measured stellar velocity dispersion of ($380.5 km.s^ $, and fainter members. We measure $ m $ in a flat Lambda cold dark matter (CDM) model, and $ m $ and $w = -1.27_ $ in a flat $w$CDM model. Given the presence of different sources angularly close in projection, we quantify through a multiplane approach their impact on the inferred values of the cosmological parameters. We obtain consistent median values, with uncertainties for only $ m $ increasing by approximately a factor of 1.5. Thanks to the remarkably wide radial interval where the multiple images are observed, ranging from 15 to 77 kpc from the BGG, we accurately measure the total mass profile and infer the stellar over total mass profile of the deflector. They result in a total mass of $(1.55 $ M$_ within 50 kpc and a stellar over total mass profile decreasing from &lt;!PCT!&gt;$ at the BGG effective radius to $(6.6 1.1) &lt;!PCT!&gt;$ at $R 77$ kpc. Our results confirm that SDSS J0100+1818 is one of the most massive (lens) galaxies known at intermediate redshift and one of the most distant candidate fossil systems. We also show that group-scale systems that act as lenses for $ 3$ background sources at different redshifts enable one to estimate the values of the cosmological parameters $ m $ and $w$ with an accuracy that is competitive with that obtained from lens galaxy clusters.

Modeling analysis and experiments of dual-FOV multiple scattering Raman lidar for detecting water cloud microphysical properties

Clouds are the primary regulators of the Earth’s climate, but the mechanisms through which they influence climate are poorly understood. Probing the microphysical properties of liquid water clouds is an urgent need for research on the Earth’s atmospheric system and atmospheric physics. In this paper, an iterative inversion of water cloud microphysical properties for a multiple scattering Raman lidar is presented, which can enable continuous, vertical measurements of the extinction coefficient of water clouds, the liquid water content (LWC), the effective radius of the cloud droplets, and cloud droplet number concentration (CDNC). The technique based on a constructed dual-field-of-view (dual-FOV) device combined with a quasi-small-angle (QSA) approximation model was investigated. The determination method of the optimal field of view (FOV) for lidar detection was discussed to enhance the sensitivity of the measured signals to the observed cloud microphysical parameters. Field observations with a co-located microwave radiometer (MWR) were carried out to verify the effectiveness of the lidar system, also an error analysis of the measurement examples was performed. The dual FOV Raman lidar experimental LWC measurement has an average deviation of 0.034 g/m3 and the relative error is 27.2% relative to the MWR measurement. The system has important potential applications in aerosol-cloud interactions and provides new ideas and methods for studying water cloud microphysical properties, further studying aerosol indirect effects.

Investigating the Correlations between Physical Parameters of Elliptical and Lenticular Galaxies

This study aims to investigate the features of stellar-gaseous kinematics and dynamics mass using scaling coefficient relationships (such as the Faber–Jackson relation (FJR)) of two samples of elliptical and lenticular galaxies. These two samples of 80 ellipticals and 97 lenticulars were selected from previous literature works. The Statistical Package for Social Sciences )SPSS( and Matrix Laboratory (MATLAB) program were used to find out the associations of multiple factors under investigation such as main kinematic properties of the gaseous-stellar (effective radius Re, surface density within the effective radius (Ʃeff) , stellar mass in the blue band (Mstar (B)), gas mass ( Mgas), dynamic (Mdyn) and baryonic (Mbar), supermassive black holes masses (MBH) in the elliptical and S0 galaxies. We concluded that the experimental relations between (Log Mbar (B) - Log Mdyn (B), Log Mbar (B) - Log MBH) have a robust correlation of ~1, and the slope appears to be more linearly (Slope ≥1) for both types of galaxies (Ellipticals and Lenticulars). This paper also noted that the empirical convergences between Log Σeff (B) and Log Mdyn have a strong high regression relationship of ~1. The slope appears to be approximately linear ~1 in the lenticular galaxies, but there is no relationship between Log Σeff (B) and Log Mdyn in the elliptical galaxies. Due to the strong impact of dynamical rotation on elliptical galaxies, it is interestingly believed that they are objects under turbulence and originate from interactions and mergers with galaxies in a spiral shape.

Simulation study on magneto-acoustic concentration tomography of magnetic nanoparticles based on vectorial acoustic source and BICGSTAB method

Abstract To overcome the vulnerability to noise of the reconstructed image and simplify the cumbersome iteration process of algorithm in the magneto-acoustic concentration tomography with magnetic induction (MACT-MI) for magnetic nanoparticles (MNPs), we established the matrix relationship between the concentration of MNPs and the first-order derivative of sound pressure based on the reconstruction method of vectorial acoustic source, and proposed the application of BICGSTAB method in solving the concentration distribution. Firstly, a simulation model was established in COMSOL Multiphysics. Secondly, the obtained data were substituted into the derived formula for imaging reconstruction. Finally, the quality of the reconstructed image was analyzed. The effects of MNP radius, shape, asymptotic concentration, and SNR on the reconstruction results were studied. Simulation results show that under the same noise condition, compared with the reconstruction method based on the LSQR-trapezoidal method, the average correlation coefficient increased by 32.9%, the average relative error decreased by 48.5%, the average structural similarity increased by 48.2%, and the average iterations decreased by 58.5%. The proposed method shows superior imaging quality and noise immunity. The research provides a theoretical basis for subsequent experimental research.&amp;#xD;

In Situ Aerosol Size Spectra Measurements in the Austral Polar Vortex Before and After the Hunga Tonga‐Hunga Ha'apai Volcanic Eruption

AbstractAerosol from the Hunga Tonga‐Hunga Ha'apai (HT‐HH) volcanic eruption (20.6°S) in January 2022 were not incorporated into the austral polar vortex until the following year, March 2023. Within the polar vortex in situ profiles of aerosol size spectra were completed in the austral autumns of 2019 and 2023, from McMurdo Station, Antarctica (78˚S), 30 months prior to and 15 months after the HT‐HH eruption. The measurements indicate that the HT‐HH impact on aerosol size was primarily confined to particles with diameters &gt;0.5 μm leading to differences in aerosol mass, surface area, and extinction from factors of 2–4 at the volcanic layer's peak below 20 km, increasing to ratios of 5–10 above 20 km. Effective radius, with radiative and microphysical implications, increased from ∼0.2 to ∼0.3 μm. An Earth system model with a modal aerosol package compares favorably with the in situ measurements of the HT‐HH aerosol impact.

Balloon Baseline Stratospheric Aerosol Profiles (B2SAP)—Perturbations in the Southern Hemisphere, 2019–2022

AbstractVolcanic and pyrocumulonimbus (pyroCB) injections into the stratosphere perturb the aerosol layer and can have important radiative and chemical impacts on timescales spanning from months to several years. Repeated in situ balloon‐borne measurements of aerosol size and number concentration (&gt;140 nm in diameter), ozone, water vapor, and atmospheric state variables made at midlatitudes in the southern hemisphere (SH) since 2019 enable us to better characterize such events. We use this record and coincident lidar extinction profiles to study several moderate to large stratospheric perturbations in the SH between 2019 and 2022 in detail, including the Australian New Year Super Outbreak (ANYSO) pyroCB in 2020. Median vertical profiles of aerosol number concentration, effective radius, and surface area in SH midlatitudes are also compared with those recorded in Northern Hemisphere midlatitudes under baseline conditions using an identical payload. These data depict the variability in stratospheric aerosol properties in the SH midlatitudes during this period and provide a benchmark for global sectional aerosol models. They reveal that sulfate particle size distributions under baseline conditions and in volcanic plumes are relatively well represented in the Community Earth System Model—Community Aerosol Radiation Model for Atmospheres (CESM‐CARMA), but more observations of biomass burning plumes are needed to improve model skill in simulating pyroCB. Comparisons between in situ and lidar observations also highlight a need for more observations of aerosol composition and refractive index in both fresh and aging biomass burning plumes.