Search results for "layer"
showing 10 items of 2667 documents
Stretching of Free Chains Confined in Concave Brush-Coated Nanocylinders
2012
The structure of a free flexible macromolecule confined in a cylindrical nanopore whose wall is coated by a polymer brush is studied by Monte Carlo simulation, varying the grafting density as well as the radius of the cylindrical pore. Because of this confinement, the free chain is stretched in axial direction; while for small grafting densities of the brush the end-to-end distance increases monotonously with decreasing pore radius, a nonmonotonic variation occurs for larger grafting densities. We show that this effect is due to strong interpenetration of the free chain and the brush chains; for very narrow pores a strong layering of cylindrical shells is found, and comparison with self-con…
Impact of Helium Ion Implantation Dose and Annealing on Dense Near-Surface Layers of NV Centers
2022
A. Berzins acknowledges support from Latvian Council of Science project lzp-2021/1-0379, “A novel solution for high magnetic field and high electric current stabilization using color centers in diamond,” and LLC “MikroTik” donation project, administered by the UoL foundation, “Improvement of Magnetic field imaging system” for the opportunity to significantly improve experimental setup as well as “Simulations for stimulation of science” for the opportunity to acquire COMSOL license. I. Fescenko acknowledges support from ERAF project 1.1.1.5/20/A/001, and I.F. and A.B. acknowledge support from LLC “MikroTik” donation project “Annealing furnace for the development of new nanometer-sized sensor…
Ultrafast Carrier Redistribution in Single InAs Quantum Dots Mediated by Wetting-Layer Dynamics
2019
Optical studies of single self-assembled semiconductor quantum dots (QDs) have been a topic of intensive investigation over the past two decades. Due to their solid-state nature, their electronic and optical emission properties are affected by the particular crystal structure as well as many-body-carrier interactions and dynamics. In this work, we use a master equation for microstates (MEM) model to study the carrier capture and escape from single QDs under optical nonresonant excitation and under the influence of a two-dimensional (2D) carrier reservoir (the wetting layer). This model reproduces carrier dynamics from power-dependent and time-resolved microphotoluminescence experiments . Du…
Ordering phenomena and phase transitions in the physisorbed quantum systems H2, HD and D2
1991
Abstract Recent experimental results of H2, HD and D2 films physisorbed on graphite are briefly reviewed. In particular, the monolayer phase diagrams, the order-disorder transition of the commensurate (C) phase and the commensurate-incommensurate (C-IC) transition are discussed. It will be shown that the melting transition of the C phase belongs to the three-state Potts universality class, and that the C-IC transition occurs via a series of novel intermediate phase, which could be identified as density-modulated phases characterized by striped and hexagonal patterns of domain walls. Due to this rich variety of phenomena, the hydrogen isotopes can be considered as model systems for two-dimen…
Structural transformations in amorphous selenium as studied by the differential thermal analysis and exoelectron emission technique
2007
The parameters (temperature, activation energy) of the surface and volume glass transition (retrification process) in amorphous selenium produced by rapid quenching of the liquid phase have been determined using the EEE and DTA techniques. EEE is a surface effect connected with structural transformations in the surface layer whereas the DTA measurements give the information about the transformations occurring in the volume of the sample. It has been found that the surface retrification of selenium occurs with activation energy smaller than the volume retrification, both observed in the first heating run. The value of activation energy for the volume retrification measured in the second DTA …
Spin crossover phenomenon of a semi-fluorinated iron (II) complex organized in a Langmuir–Blodgett film
2000
Abstract A new amphiphilic iron (II) complex bearing semi-fluorinated chains has been organized in Langmuir and Langmuir–Blodgett (LB) films. This molecule forms a perfectly stable monolayer at the gas–water interface. Such a film can be transferred easily onto a solid substrate leading to well-defined multilayers. The spin crossover phenomenon occurring in this material has been studied by infrared spectroscopy and magnetization measurements. In the LB film architecture, the iron complex appears to be quenched in a high spin state. This quenching can be released after a thermal annealing and is therefore associated to the specific organization induced by the LB technique.
Substrate impact on the thickness dependence of vibrational and optical properties of large area $MoS_2$ produced by gold-assisted exfoliation
2021
The gold-assisted exfoliation is a very effective method to produce large-area ($cm^2$-scale) membranes of molybdenum disulfide ($MoS_2$) for electronics. However, the strong $MoS_2/Au$ interaction, beneficial for the exfoliation process, has a strong impact on the vibrational and light emission properties of $MoS_2$. Here, we report an atomic force microscopy (AFM), micro-Raman ($\mu-R$) and micro-Photoluminescence ($\mu-PL$) investigation of $MoS_2$ with variable thickness exfoliated on Au and subsequently transferred on an $Al_2O_3/Si$ substrate. The $E_{2g}$ - $A_{1g}$ vibrational modes separation $\Delta\mu$ (typically used to estimate $MoS_2$ thickness) exhibits an anomalous large val…
Statistical performance of a multiclass bulk production queueing system
2004
Abstract In this paper, we discuss how to statistically analyze a make-to-stock production system the behaviour of which depends on a multiclass bulk queueing system. The performance of the system is evaluated in terms of the different demands of products, processing times and, mainly, through the finished product inventory and other related measures that quantify the queueing effects in the system. A numerical example which illustrates the applicability of the results in an inventory scenario is also discussed.
A NEURAL NETWORK PRIMER
1994
Neural networks are composed of basic units somewhat analogous to neurons. These units are linked to each other by connections whose strength is modifiable as a result of a learning process or algorithm. Each of these units integrates independently (in paral lel) the information provided by its synapses in order to evaluate its state of activation. The unit response is then a linear or nonlinear function of its activation. Linear algebra concepts are used, in general, to analyze linear units, with eigenvectors and eigenvalues being the core concepts involved. This analysis makes clear the strong similarity between linear neural networks and the general linear model developed by statisticia…
Numerical Determination of Intrinsic Diffusion in Fe-Cr-Al Systems
2010
The intrinsic diffusion coefficients in diffusion aluminide coatings based on Fe-30Cr were determined at 1000oC. The diffusion fluxes were given by the Nernst Planck formulae and the Darken method for multicomponent systems was applied. This paper summarizes some numerical results to determine the composition dependent diffusivities in Fe-Cr-Al systems. The method presented in this study to obtain average intrinsic diffusion coefficients is as an alternative to the Dayananda method. Our method based on empirical parameters allowed us to predict the concentration profile during the interdiffusion process.