Mean free path

About: Mean free path is a research topic. Over the lifetime, 4412 publications have been published within this topic receiving 114418 citations.

Nonlinear guiding center theory of perpendicular diffusion: General properties and comparison with observation

Abstract: [1] A nonlinear guiding center (NLGC) theory for diffusion of charged particles perpendicular to the mean magnetic field was recently proposed. Here, we draw attention to a number of attractive features of this theory: (1) The theory provides a natural mechanism to connect the perpendicular mean free path with the parallel mean free path. In fact, the parallel mean free path is the only particle property required to determine uniquely the perpendicular mean free path. (2) Under a broad range of conditions, the theory predicts that the perpendicular mean free path will be of order one percent or a few percent of the parallel mean free path, in agreement with numerical simulations of particle transport. (3) For conditions representative of the inner heliosphere, the theory predicts values of the perpendicular mean free path in agreement with observational determinations from Jovian electrons and from modeling Ulysses observations of Galactic protons.

Effect Bi2O3 on the physical, structural and radiation shielding properties of Er3+ ions doped bismuth sodiumfluoroborate glasses

Abstract: Er3+ ions doped Bismuth sodiumfluoroborate glasses with varying Bi2O3 content (0−50 in wt%) have been prepared following the melt quenching technique. The density, molar volume, FTIR and UV–Visible studies have been used to determine physical and structural properties of the prepared glasses. The FTIR studies explores that, addition of Bi2O3 helps the progressive conversion of [BO4] units into [BO3] units thus lead to the creation of non-bridging oxygens (NBOs). The boron‑boron separation( ), oxygen packing density(OPD), bond density(nb) and calculated Poisson's ratio (μcal) values are found to decrease with the addition of Bi2O3thus reveal the fact that the network connectivity decreases due to the formation of non-bridging oxygen sites and the glass network becomes less tightly packed. Further, ionic nature of the Er3+ − metal ligand bond was identified from the measured optical basicity (Λth), covalent and ionic characteristic factors, and bonding parameter (δ) values.The observed variations in the optical electronegativity, basicity, metallization criterion and optical band gap energy (Eg) values have been discussed in terms of the structural changes that takes place due to the addition of Bi2O3 into the B2O3 network. Additionally, radiation shielding properties of the prepared glasses have been studied in the energy range 0.015–15 MeV. The mass attenuation coefficient has been calculated using MCNP5 code and XCOM software. The MCNP5 results match most of the XCOM data very well. Further, the effective atomic number, mean free path and half value layer (HVL) for the titled glasses were computed. The mass attenuation coefficient and the effective atomic number were found to progressively increase with the increase in the Bi2O3 content. The addition of Bi2O3 led to decrease the half value layer which means that more Bi2O3 content enhances the radiation shielding performance for the prepared glasses.

Size Effect on the Thermal Conductivity of High-Tc Thin-Film Superconductors

Abstract: Using the kinetic theory approximation and reported data, this study shows that at low temperatures, the phonon mean free path in polycrystalline ceramic YBa{sub 2}Cu{sub 3}O{sub 7} can be of the order of the thickness of thin-film superconductors. In this case, boundary scattering reduces the thermal conductivity with decreasing film thickness. A simple method accounts for the size effect on conduction in thin films. This analysis rests solely on geometric arguments and does not consider the effect of grain boundaries. For conduction along the film, this model approximates well an analytical solution of Boltzmann transport equation, and is in good agreement with experimental data for thin lead films. The model is also employed to analyze the size effect on conduction across the film and the influence of anisotropy.

Photon parameters for gamma-rays sensing properties of some oxide of lanthanides

Abstract: In the present research work, the mass attenuation coefficients (μm) representing the interaction of gamma photons with some oxide of lanthanides (Lu2O3Yb2O3, Er2O3, Sm2O3, Dy2O3, Eu2O3, Nd2O3, Pr6O11, La2O3 and Ce2O3) were investigated using WinXCom software in the wide energy range of 1 keV–100 GeV. The calculated values of μm afterwards were used to evaluate some gamma rays sensing properties as effective atomic effective atomic numbers (Zeff), effective electron densities (Nel), half value layer (HVL) and mean free path (MFP). The computed data observes that, the Lu2O3 shown excellent γ-rays sensing response in the broad energy range. At the absorption edges of the high elements present in the lanthanide compounds, more than a single value of Zeff were found due to the non-uniform variation of µm. Comparisons with experiments wherever possible have been achieved for the calculated µm and Zeff values. The calculated properties are beneficial expanded use of designing in radiation shielding, gas sensors, glass coloring agent and in electronic sensing devices.

Visible mie scattering in nonabsorbing hollow sphere powders.

Abstract: Hollow silica nanoparticles (HSNP) with diameters comparable to visible wavelengths and with thin shells (<15 nm) feature an unexpected color effect. Single particle and powder spectroscopy, as well as calculations based on Mie theory were used to investigate this phenomenon. The use of HSNPs increases the transport mean free path of light significantly, which reduces multiple scattering, and thus the Mie resonances become visible to the bare eye.