Search results for "Mathematical physics"
showing 10 items of 2687 documents
Molecular dynamics investigation of the premelting effects of Lennard-Jones (111) surfaces
1987
Molecular dynamics simulations have been performed to study the premelting effects of noble-gas surfaces (argon) close to but below the bulk melting temperature. In particular, the increase of disorder as a function of temperature at (111) surface has been considered. The truncated Lennard-Jones (6-12) potential is used to describe the interactions between particles. Surface premelting has been analyzed by means of total energies, trajectory plots, mean sequare displacement functions, diffusion coefficients, vacancy concentrations and two-dimensional order parameters. The (111) surface starts to disorder by vacancy formation, which leads to the premelting of the surface layer far below the …
High Voltage Insulation and Gas Absorption of Polymers in High Pressure Argon and Xenon Gases
2018
High pressure gas time projection chambers (HPGTPCs) are made with a variety of materials, many of which have not been well characterized in high pressure noble gas environments. As HPGTPCs are scaled up in size toward ton-scale detectors, assemblies become larger and more complex, creating a need for detailed understanding of how structural supports and high voltage insulators behave. This includes the identification of materials with predictable mechanical properties and without surface charge accumulation that may lead to field deformation or sparking. This paper explores the mechanical and electrical effects of high pressure gas environments on insulating polymers PTFE, HDPE, PEEK, POM …
Sensing properties of assembled Bi2S3nanowire arrays
2015
Bismuth sulfide (Bi2S3) nanowires were grown in porous aluminium oxide template and a selective chemical etching was applied to transfer the nanowires to a solution. Well aligned nanowire arrays were assembled on pre-patterned silicon substrates employing dielectrophoresis. Electron beam lithography was used to connect aligned individual nanowires to the common macroelectrode. In order to evaluate the conductometric sensing performance of the Bi2S3 nanowires, current–voltage characteristics were measured at different relative humidity (RH) levels (5–80%) / argon medium. The response of the Bi2S3 nanowires depending of RH is found to be considerably different from those reported for other ty…
Angular dependence of recombination luminescence-detected EPR in a ZnO crystal
2015
Angular dependency of electron paramagnetic resonance, optically detected by UV-excited recombination luminescence (RL-EPR), was measured for nominally pure ZnO single crystals. Observed magnetic resonances belong to the broad yellow RL band with slow decay centred at 610 nm, which is characteristic of untreated ZnO crystals. In the sample, irradiated with the 266 nm UV laser, an additional RL band centred at 740 nm appears, which has considerably faster decay time than the yellow one. This RL band is characteristic of the luminescence of Fe3+ ions in the ZnO crystals. It could be observed only after the UV laser treatment. No RL-EPR signal was detected for this RL band. Our spectral simula…
Capillary condensation in the two-dimensional lattice gas: A Monte Carlo test of fluctuation corrections to the Kelvin equation
1997
A two-dimensional lattice gas model with nearest-neighbour attractive interaction confined in a strip of width L between two parallel boundaries at which an attractive short-range force acts is studied by Monte Carlo simulations, for cases where the system is in the wet phase near the critical wetting transition line for . We study the shift of the chemical potential of the transition in the strip as a function of L by thermodynamic integration methods, , and also obtain the thickness of the wetting film at the chemical potential at which capillary condensation occurs. In the range the data are consistent with a variation according to the Kelvin equation, , as well as with a shifted Kelvin …
Electronic cooling and hot electron effects in heavily doped silicon-on-insulator film
2004
The influence of carrier concentration in silicon-on-insulator film on the thermal characteristics of semiconductor and performance of the superconductor-semiconductor-superconductor micro-coolers have been investigated at sub kelvin temperatures. The overheating of the lattice in heavily doped silicon film must be taken into account in the analysis of electron-phonon coupling experiment and operation of the cooler device. The heat flow between electrons and phonons in heavily doped silicon films is found to be proportional to T6, which is in accordance with theoretical prediction for dirty limit. Increasing the doping level in the semiconductor considerably increases both the efficiency of…
EPR Study of Gd3+local structure in ScF3crystal with negative thermal expansion coefficient
2015
Zero field splitting (ZFS) of Gd3+ impurity in ScF3 is studied by electron paramagnetic resonance at 77 and 295 K. ZFS parameter b4 values obtained from angular dependence simulations show that regardless of negative thermal expansion in ScF3 temperature dependence of |b4| is similar to other cubic fluoroperovskites. Our analysis of ZFS parameters indicates that the local structure of Gd3+ centres expands positively with temperature.
Precision mass measurements using a penning trap and highly charged ions produced in an electron beam ion source
1997
A method for precision mass measurements in a Penning trap using highly charged ions produced in an electron beam ion source (CRYSIS) has been developed. The cyclotron frequencies for O8+, 7+, 6+, 5+ and Ar18+, 17+, 16+, 15+, 14+, 13+ ions have been determined by the excitation of the sum frequency v+ + v−. In addition to CRYSIS ions, H+, H2+ and He+ ions were produced by electron bombardment of the H2 rest gas or helium gas introduced through an UHV leak valve into an auxiliary ion trap (or a pre-trap). A technique for fast (seconds) interchanging of the ion species in the precision trap has been implemented to reduce the long term magnetic field drift.
Photocatalytic activity of non-stoichiometric ZnFe2O4under visible light irradiation
2014
Nanostructured zinc ferrites with different excess iron contents (ZnFe2+zO4, where z = 0.00, 0.05, 0.10 and 0.15) have been synthesized using the sol–gel auto-combustion method. The effect of excess iron on the structural, optical and visible light photocatalytic activity of zinc ferrite samples has been investigated. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), x-ray magnetic circular dichroism (XMCD), Brunauer–Emmett–Teller theory, scanning electron microscopy (SEM), diffuse reflectance spectroscopy (UV–Vis) and photoluminescence spectroscopy were used to characterize the synthesized non-stoichiometric ZnFe2O4 powders. The XRD patterns demonstrated that the samples con…
Recently published line strengths for the transition array 3s–3p in C I, N II and O III: a critical review
2014
Recently calculated atomic structure data for C I, N II and O III are reviewed and analyzed by performing J-file sum rule tests. The line strengths of the 3s–3p transition array are analyzed. In the case of neutral carbon and ionized nitrogen data, the LS-forbidden transitions are included in the analysis.