Design of optical components for a light emitting diode zoom illumination system

In this article, we report an optical design for a light emitting diode that can achieve high illumination quality using two hyperbolic reflectors. The relative movements of the reflectors and the light source produce a zoom function that can change the illumination beam from convergence to divergence. This study uses optical software ZEMAX for system simulation, and optimization was performed to select reflector parameters with the objectives of both improving floodlight uniformity and spotlight efficiency. Finally, experiments were conducted to verify the validity of the design, and the results corresponded well to the zoom illumination simulations.     

A wide-range Parallel Radial Mirror Analyzer for scanning electron/ion microscopes

This paper presents the design of a wide-range Parallel Radial Mirror Analyzer (RMA) for use as an attachment inside the specimen chambers of scanning electron/ion microscopes. The range of energies for the PRMA typically varies by a factor of 50, and it is predicted to have second-order focusing properties for all electrons/ions that are detected. For a polar angular spread of ±3°, the simulated energy resolution at an energy of 100 eV is around 0.65%, and it drops to less than 0.2% for energies between 300 eV and 5000 eV. The PRMA is predicted to have a transmittance of over an order magnitude better than previous wide-range parallel energy analyzer designs.     

Influence of emitter-ledge thickness on the surface- recombination mechanism of InGaP/GaAs heterojunction bipolar transistor

In this work, the characteristics of InGaP/GaAs heterojunction bipolar transistors (HBTs) with various emitter-ledge thicknesses are comprehensively studied and demonstrated. Based on the two-dimensional analysis, some important parameters such as the recombination rate and DC characteristics are studied. The simulated analyses are in good agreement with experimental results. It is known that better HBT performance, including lower recombination rate in the surface channel, and higher DC current gain are obtained in the studied devices with the emitter ledge thickness between 100 and 200 Å.     

Sliding Abrikosov lattice in a superconductor with a regular array of artificial pinning centers: AC conductivity and criticality at small frequencies

Dynamics of the flux lattice in the mixed state of strongly type-II superconductor near the upper critical field subjected to AC field and interacting with a periodic array of short range pinning centers is considered. The superconductor in a magnetic field in the absence of thermal fluctuations on is described by the time-dependent Ginzburg–Landau equations. For a special case of the δ-function shaped pinning centers and for pinning array commensurate with the Abrikosov lattice (so that vortices outnumber pinning centers) an analytic expression or the AC conductivity is obtained. It is found that below a certain critical pinning strength and for sufficiently low frequencies there exists a sliding Abrikosov lattice, which vibrates nearly uniformly despite interactions with the pinning centers. At very small frequencies the conductivity diverges at the critical pinning strength.     

Avoidance of Majorana resonances in periodic topological superconductor-nanowire structures

Semiconducting nanowires in proximity to superconductors are promising experimental systems for Majorana fermions which may ultimately be used as building blocks for topological quantum computers. A serious challenge in the experimental realization of the Majorana fermion in these semiconductor-superconductor-nanowire structures is tuning the semiconductor chemical potential in close proximity to the metallic superconductor. We show that presently realizable structures in experiments with tunable chemical potential lead to Majorana resonances, which are interesting in their own right, but do not manifest non-Abelian statistics. To resolve this crucial barrier to the solid state realization of Majorana fermions, we propose a new topological superconducting array structure where introducing the superconducting proximity effect from adjacent nanowires generates Majorana fermions with non-Abelian statistics.     

New model for tracer-diffusion in amorphous solid

The tracer-diffusion and structure of polymorphic states of amorphous solid is studied by mean of the statistic relaxation technique and simplex analysis. Several different metastable states of amorphous iron have been constructed based on the model containing 2 × 10⁵ atoms. All models have almost the same pair radial distribution functions, but they differ in the potential energy per atom and the density. We found a large number of vacancy-simplexes which varies according to the relaxation and serves as a diffusion vehicle. New diffusion mechanism for tracer-diffusion is found of which the elementary diffusion process likes a collapse of “microscopic bubble” in amorphous matrix. This includes a jump of diffusing atom and the collective movement of a large number of neighboring atoms. The diffusion constant D determined in accordance with considered diffusion mechanism is in reasonable agreement with experimental data. The decrease in diffusion constant D upon thermal annealing is explained by the reducing vacancy-simplex concentration which is caused by both the local atomic rearrangement and the elimination of excess free volume.     

Electromigration Studies of Carrier-Free 239Np(V) in Aqueos Solutions

Ion mobilities of carrier-free ²³⁹Np(V) have been measured in aqueous solutions, T = 298.1 (1) K. Ion mobilities of ²³⁹NpO₂ ⁺ and its dependencies on pH of acidic inert electrolytes have been measured. In alkaline solutions the stoichimetric hydrolysis constants of NpO₂(OH) as well as NpO₂(OH)₂ ^? have been obtained. Complex formations of ²³⁹Np(V) with oxalate, tartrate, sulphate, acetate and citrate ligands have been studied in neutral solutions.     

Estimating the parametric component of nonlinear partial spline model

Consider a nonlinear partial spline model . This article studies the estimation problem of when g₀ is approximated by some graduating function. Some asymptotic results for are derived. In particular, it is shown that can be estimated with the usual parametric convergence rate without undersmoothing g₀.     

Maximal operators and singular integral operators along submanifolds

In this paper we prove, for certain values of p, the L^p boundedness of the maximal operator

     

Some mathematical tools for linguistic probabilities

We propose and develop, in this paper, some concepts and techniques useful for the theory of linguistic probabilisies introduced by L.A. Zadeh. These probabilities are expressed in linguistic rather than numerical terms. The mathematical framework for this study is based upon the possibility theory.We formulate first the problem of optimization under elastic constraints which is not only important for mathematical programming but will be served to justify the extension of possibility measure to linguistic variables. Next, in connection with translation rules in natural languages we study some transformations of fuzzy sets using a relation between random sets and fuzzy sets. Finally, we point out some differences between random variables and fuzzy variables, and present the mathematical notion of possibility, in the setting of set-functions, as a special case of Choquet capacities.