Miracle-dz/UniFAR-FTUs huggingface dataset:
An intrinsic tensor technique in Minkowski space with applications to boundary value problems

This article describes an intrinsic tensor technique for solving boundary value problems in electrodynamics of moving media, which entails considerable notational simplification and calculational advantages. On the basis of generalized impedance and characteristic matrix methods, the reflection and transmission operators of a multilayer structure consisting of anisotropic media uniformly moving with different velocities are found. A general solution to the problem of reflection and transmission at the interface between two moving isotropic media is obtained, and explicit expressions for Doppler shifts, Snell’s laws, critical and Brewster angles, reflection and transmission coefficients, and the radiation pressure force are found. The material tensor of a uniformly moving linear medium is expressed through its reflection and transmission operators.
Hole drift velocity in silicon

Drift velocities for holes in high-purity Si were measured for fields between approximately 3 and 5 x 10/sup 4/ V/cm and temperatures between 6 and 300/sup 0/K for the crystallographic directions (100), (110), and (111). The ohmic mobility is theoretically interpreted on the basis of a 2-band model consisting of a spherical parabolic and a spherical nonparabolic band, and the relaxation-time approximation. The low-temperature ohmic mobility is strongly influenced by the nonparabolicity of the heavy-hole band. The high-field region (E greater than or equal to 10/sup 3/ V/cm) was analyzed by using a single warped heavy-hole band model and a Monte Carlo technique. Anisotropy of hot-hole drift velocity is associated with warping of the valence band. Optical- and acoustic-scattering mechanisms are found to be of comparable strength. (WDM)
Exponential stability of Hopfield neural networks with time‐varying delays via impulsive control

In this paper, by utilizing the Lyapunov functionals, the analysis method and the impulsive control, we analyze the exponential stability of Hopfield neural networks with time‐varying delays. A new criterion on the exponential stabilization by impulses and the exponential stabilization by periodic impulses is gained. We can see that impulses do contribution to the system's exponential stability. Two examples are given to illustrate the effectiveness of our result. Copyright © 2010 John Wiley & Sons, Ltd.
Film bulk acoustic resonator (FBAR) device

Disclosed are a film bulk acoustic resonator (FBAR) device and a method for fabricating the film bulk acoustic resonator (FBAR) device. The film bulk acoustic resonator (FBAR) device comprises a membrane layer having a plurality of active regions and provides different resonant frequencies by providing different thicknesses of the active regions of series resonators and shunt resonators, and by controlling the thicknesses, respectively. A plurality of the film bulk acoustic resonator (FBAR) devices having different resonant frequencies are manufactured on a substrate, thereby simultaneously manufacturing a transmission filter and a reception filter on the same substrate. Further, the film bulk acoustic resonator (FBAR) device has a stable structure and excellent characteristics.
Publications of the Astronomical Society of the Pacific 98:1014-1017, October 1986 XV. COSMOLOGICAL H n REGIONS AND THE PHOTOIONIZATION OF THE INTERGALACTIC MEDIUM*

The generalization of the classical H II region problem to the case of a point source of ionizing radiation in a cosmologically expanding gas in a Friedmann-Robertson-Walker universe is summarized. An application of this work is described in which is tested the hypothesis that quasars photoionize the IGM to the degree implied by the well-known absence of a Gunn-Peterson effect. Recent studies of faint quasars at high redshift, which suggest a decline in the number density of quasars for % > 3, imply that the H II regions of high-redshift quasars cannot overlap early enough to satisfy the Gunn-Peterson test. This suggests that either the observations are failing to detect the true number density of high-redshift quasars or else something else must ionize the IGM at high redshift.
A MULTIOBJECTIVE INTERACTIVE SEQUENTIAL HYBRID OPTIMIZATION TECHNIQUE FOR DESIGN DECISION MAKING

The paper proposes an interactive method for obtaining a solution to a multiple objective design decision making problem. The focus is on generating Pareto solutions including those that are in the non-convex region, and are desirable to obtain in an engineering design context. After the generation of a small subset of the Pareto solutions, the designer's feedback is elicited in order to eliminate part of the subset. The process is repeated until il iteratively narrows down the Pareto solution set to a size small enough so that the designer is able to easily select a final solution. The advantage of this approach is that the designer can view a few sample points from the Pareto set before zooming into the region preferred and without expending computation time in generating a complete Pareto set. The process has been demonstrated with the help of an example, the design of a fleet of ships, that has mixed-discrete variables and hence a genetic algorithm is used as the optimizer.
OPTICAL CONFINEMENT AND THRESHOLD CURRENTS IN III-V NITRIDE HETEROSTRUCTURES: SIMULATION

Waveguiding properties of InGaN/GaN/AlGaN double heterostructures were modeled. A comparison between double heterostructures (DHs) and separate confinement heterostructures (SCHs) has been made. This is an attempt to consider influence of material absorption in passive layers of nitride laser structures on a threshold current. This absorption significantly increases the threshold current, and is especially important in the case of quantum well SCHs. The threshold current density in nitride-based lasers has been estimated to be about 10 kA/cm2. Due to high absorption of light in passive layers, no decrease in the threshold current of single quantum well SCH lasers in comparison with DH lasers is expected. The threshold current density can be decreased in multiquantum well lasers. In these lasers, the threshold current density is expected to be about several kA/cm2. The optimal thickness of active and adjacent layers as well as alloy compositions in cladding layers have been estimated, and as our simulation has shown, no more than 8%–10% of AlN in claddings are needed.
The Evolution of AmFm Stars, Abundance Anomalies, and Turbulent Transport

Stellar evolution models of stars of 1.45-3.0 M☉ have been calculated, including the atomic diffusion of metals and radiative accelerations for all species in the OPAL opacities. As the abundances change, the opacities and radiative accelerations are continuously recalculated during evolution. These models develop iron-peak convection zones centered at a temperature of approximately 200,000 K. If one then assumes that there is sufficient overshoot to homogenize the surface regions between the hydrogen, helium, and iron-peak convection zones, it is shown here that the surface abundance variations that are produced, without any arbitrary parameter, closely resemble the abundance anomalies of AmFm stars, except that they are larger by a factor of about 3. Detailed evolutionary model calculations have been carried out, varying the turbulence in the outer stellar regions in order to improve the agreement with the observed anomalies in AmFm stars. The outer mass mixed by turbulence has been varied, as well as the density dependence of the turbulent diffusion coefficient. It is shown that the anomalies depend on only one parameter characterizing turbulence, namely, the depth of the zone mixed by turbulence. The calculated surface abundances are compared to observations of a number of recently observed AmFm stars. For Sirius A, 16 abundances (including four upper limits) are available for comparison. Of these, 12 are well reproduced by the model, while three are not so well reproduced, and one is a very uncertain observation. In cluster AmFm stars, the age and initial abundances are known. There is then less arbitrariness in the calculations, but fewer chemical species have been observed than in Sirius. The available observations (Hyades, Pleiades, and Praesepe stars are compared) agree reasonably well with the calculated models for the five stars that are compared. The zone mixed by turbulence is deeper than the iron convection zone, reducing the abundance anomalies to values that are too small for iron-peak convection zones to develop in many of the models. The origin of the mixing process then remains uncertain. There is considerable scatter in the observations between different observers, so it is premature to conclude that hydrodynamical processes other than turbulence are needed to explain the observations. We do not rule out the possibility that this might be the case, but the observations do not appear to us to be good enough to establish it.
Interpretation of electrical and galvanomagnetic properties of diamond monocrystals

An exponential type description of the temperature dependence of hole mobility and the experimentally observed mobility maxima reveal that activation energies obtained from the temperature dependence of the resistivity and that of the hole concentration differ from each other in a range from 0.03 to 0.08 eV for diamond monocrystals. This difference is too high to be simply neglected. On the other hand, the existence of a mobility maximum and of a steep high temperature slope on the temperature dependence of mobility is explained here solely by the dominance of the ionized impurity scattering.
Gauge theory and quasidiabatic states in molecular physics

Following previous works [Moody et al., Phys. Rev. Lett. 56, 893 (1986) and Zygelman, Phys. Lett. A 125, 476 (1987)], we review in some detail the gauge theoretical form of the Born–Oppenheimer description of molecules. The derivative couplings which describe nonadiabatic effects play the role of gauge potentials. Applying the gauge theoretical formalism (well known in particle physics), we rederive a theorem concerning the nonexistence of strictly diabatic states. Further we propose the Lorentz gauge condition to define quasidiabatic states. We show that the recently proposed block diagonalization method to obtain quasidiabatic states leads automatically to the Lorentz gauge locally.Following previous works [Moody et al., Phys. Rev. Lett. 56, 893 (1986) and Zygelman, Phys. Lett. A 125, 476 (1987)], we review in some detail the gauge theoretical form of the Born–Oppenheimer description of molecules. The derivative couplings which describe nonadiabatic effects play the role of gauge potentials. Applying the gauge theoretical formalism (well known in particle physics), we rederive a theorem concerning the nonexistence of strictly diabatic states. Further we propose the Lorentz gauge condition to define quasidiabatic states. We show that the recently proposed block diagonalization method to obtain quasidiabatic states leads automatically to the Lorentz gauge locally.
Applying Real-Valued Genetic Algorithm on Curve Fitting Problem

Curve fitting refers to the process of finding an appropriate function that fits a finite set of data points. Representing a set of data points by a function is quite beneficial in data analysis and reapplication, and this technique is often used in engineering and technical problems. Fitting accuracy and computational time are usually the most crucial factors to be taken care of in curve fitting problems. Previous researchers have demonstrated that genetic algorithms can effectively solve curve fitting problems, but the difficulty of parameter coding is also widely encountered in computational processes. Hence, this study addresses on applying real-valued genetic algorithm to deal with curve fitting problems. Detailed discussion is made on the optimization efficiency among various data, and finally, some key parameters to curve fitting results are found and presented.
Analytic Treatment of the Coulomb Potential in the Path Integral Formalism by Exact Summation of a Perturbation Expansion

A straightforward analytical calculation of the s‐like energy spectrum of the hydrogen atom is performed entirely within Feynman's path integral formalism. For this purpose the integral transform W = ∫d3rβK(rβ,0), where K(rβ,0) is the density matrix of the hydrogen atom written as a path integral, is calculated by means of the exact summation of a ``modified'' perturbation expansion (W is expanded as a power series in β with β = 1/kT). Performing this summation is equivalent to solving a problem of moments with infinite moments. For a wide class of potentials the perturbation expansion for W converges faster than the power‐series expansion for the exponential function (for the Coulomb potential the convergence rate of both expansions is the same). It is shown how the complete energy spectrum can be obtained by this method. It is also illustrated how the wavefunctions might be obtained by transforming W.
Self-organization, ergodicity breaking, phase transition and synchronization in two-dimensional traffic-flow model

Analytical investigation is made on the two-dimensional traffic-flow model with alternative movement and exclude-volume effect between right and up arrows [Phys. Rev. {\bf A} 46 R6124 (1992)]. Several exact results are obtained, including the upper critical density above which there are only jamming configurations, and the lower critical density below which there are only moving configurations. The observed jamming transition takes place at another critical density $p_{c}(N)$, which is in the intermidiate region between the lower and upper critical densities. It is derived that $p_{c}(N)\,=\,CN^{\alpha}$, where $C$ and $\alpha$ are determined to be respectively $0.76$ and $-0.14$ from previous numerical simulation. This transition is suggested to be a second-order phase transition, the order parameter is found. The nature of self-organization, ergodicity breaking and synchronization are discussed, Comparison with the sandpile model is made.
Structural and electrical characterization of CoTiN metal gates

As the gate size continues to decrease in nanoscale transistors, having metal gates with amorphous or near amorphous structures can potentially reduce grain-induced work function variation. Furthermore, amorphous materials are known to have superior diffusion barrier properties, which can help prevent work function change due to the diffusion of metals in contact with the gate. In this work we show that with the addition of cobalt, thin films of polycrystalline TiN become more amorphous with a smaller grain size. Cox(TiN)1-x films, where x = 60–80%, appear to consist of nanocrystals embedded in an amorphous matrix, and are thermally stable with no significant crystallization up to an annealing temperature of at least 600 °C. Reducing the nitrogen gas flow ratio during sputter deposition from 9% to 2.5% further decreases the films' crystallinity, which is apparent by more sparse and even smaller nanocrystals. In addition to being partially amorphous, these CoTiN films also exhibit good thermal stability, l.
Set Partitioning: A survey

This paper discusses the set partitioning or equality-constrained set covering problem. It is a survey of theoretical results and solution methods for this problem, and while we have tried not to omit anything important, we have no claim to completeness. Critical comments pointing out possible omissions or misstatements will be welcome.Part 1 gives some background material. It starts by discussing the uses of the set partitioning model; then it introduces the concepts to be used throughout the paper, and connects our problem to its close and distant relatives which play or may play a role in dealing with it: set packing and set covering, edge matching and edge covering, node packing and node covering, clique covering. The crucial equivalence between set packing/partitioning and node packing problems is introduced.Part 2 deals with structural properties of the set packing and set partitioning polytopes. We discuss necessary and sufficient conditions for all vertices of the set packing polytope to be intege.
Stratospheric tracer spectra

Abstract The combined effects of advection and diffusion on the equilibrium spatial structure of a tracer whose spatial variation is maintained by a large-scale forcing are considered. Motivated by the lower stratosphere, the flow is taken to be large-scale, time-dependent, and purely horizontal but varying in the vertical, with the vertical shear much larger than horizontal velocity gradients. As a result, the ratio α between horizontal and vertical tracer scales is large. (For the lower stratospheric surf zone α has been shown to be about 250.) The diffusion parameterizes the mixing effects of small-scale processes. The three space dimensions and the large range between the forcing scale and the diffusive scale mean that direct numerical simulation would be prohibitively expensive for this problem. Instead, an ensemble approach is used that takes advantage of the separation between the large scale of the flow and the small scale of the tracer distribution. This approach, which has previously been used i.
Upscaling of permeability of anisotropic heterogeneous formations: 1. The general framework

In numerical simulations of flow through heterogeneous formations, the domain is partitioned into numerical elements. The solution requires assigning physical properties to each numerical block. The process of transferring information from the scale of actual heterogeneity to that of the numerical elements is known as upscaling. We consider steady, one-phase flow and the only property of interest is the permeability, which is regarded as a random space function, and the same is true for the upscaled conductivity. In this paper we establish the necessary and sufficient conditions to be satisfied by upscaling. The necessary conditions are expressed with the aid of the global response of the formation, e.g., the total flux caused by a constant pressure head drop applied on the boundaries. The requirement is that the expected value and the variance of the total flux are the same in the actual and upscaled domains. These are supplemented by local conditions which stipulate that space averages of flow variables over the numerical blocks in the upscaled domain tend to those in the actual formation when the elements size tends to 0. The result of this analysis is that the upscaled permeability must be such as to ensure the equality, in a statistical sense, between the space averaged dissipation in the two media. By assuming an unbounded domain, average uniform flow and stationarity, simplified relationships between the moments of the dissipation in the upscaled and actual media are derived. It is shown that the effective permeability of the two media is the same. The approach is illustrated for stratified formations for which exact composition rules are possible. Even in this simple case the upscaled permeability is a tensor, characterized at second order by two mean components and three covariance functions.
MODELING OF THE INITIAL MASS FUNCTION USING THE METROPOLIS–HASTINGS ALGORITHM

A stochastic model has been developed for the hierarchical fragmentation of a molecular cloud. Here, the number of fragments, time between successive fragmentation steps, and mass of a fragment are considered as random variables, and fragment masses are generated using the Metropolis–Hastings algorithm. The resulting mass spectra, computed at different projected distances and taking opacity into consideration, show a signature of mass segregation. The critical mass, mass spectrum, and mass segregation are consistent with the observations of young massive clusters in our Galaxy as well as in external galaxies.
Differential Equations With Fuzzy Parameters

This paper is concerned with systems of ordinary differential equations with fuzzy parameters. Applying the Zadeh extension principle to the equations, we introduce the notions of fuzzy solutions and of componentwise fuzzy solutions. The fuzzy extension of the solution operator is shown to provide the unique fuzzy solution as well as the maximal componentwise fuzzy solution. A numerical algorithm based on monotonicity properties of membership functions is presented, together with a proof of convergence. In an interplay of interval analysis and possibility theory, these methods allow to process subjective information on the possible fluctuations of parameters in models involving ordinary differential equations. This is demonstrated in two engineering applications: a queueing model for earthwork and a model of oscillations of bell-towers.
Wavelet analysis of the multifractal character of the galaxy distribution

We have determined generalized dimensions of the observed distribution of galaxies. Their different values indicate that this distribution may be described as a multifractal. In order to analyse this distribution further, we have applied local wavelet transforms. Wavelets provide us with an interesting tool to analyse the large-scale structure which can be mathematically quantified and intuitively visualized. Comparing the results of these transforms at different dilation factors helps to visualize more clearly the nearly singular nature of the distribution. This method also allows us to determine the range of the local density power laws
DEPOSITION-AND-SUBSTRATE TUNABLE PHOTONIC BANDGAP IN OPTICAL RESPONSES OF HYDROGENATED AMORPHOUS SILICON CARBIDE THIN FILMS

Amorphous hydrogenated silicon carbide (a-SiC:H) thin films have been prepared by the RF reactive magnetron sputtering technique. The optical properties of the films have been studied by optical spectroscopy with an incoherent light source. The material is commonly regarded as a dielectric. We have discovered however that some films that were prepared under certain deposition conditions and on certain substrates may respond to external light as a metallic thin film, i.e. there are strongly enhanced reflection peaks in the optical spectrum. We have further discovered that some films may have a strong and broadened absorption peak at about 590 nm, which is an apparent photonic bandgap in the visible spectrum. The appearance of the photonic bandgap is very sensitive to two parameters: the substrate and the deposition gas. By changing the two parameters, one shifts the status of the film from with and without the photonic bandgap.
Filtering Methods for Mixture Models

We consider Bayesian inference for mixture distributions of known number of components via a set of filtering recursions. We extend a method—proposed in an earlier article—of direct simulation for discrete mixture distributions in order to analyze continuous mixture models. Furthermore, we introduce resampling steps similar to those in particle filters within the steps of the filtering recursions, which make calculations efficient and enable us to analyze larger datasets. The proposed algorithm for “resampled direct simulation” is a generalization of the particle filter which allows for merging identical/similar particles prior to resampling. We compare the proposed algorithm with this particle filter and with the Gibbs sampler using simulated data and real datasets.
Optical response of an ultrathin film and a large-angle grain-boundary in superconducting YBa2Cu3O7-δ

We have investigated the optical response of epitaxial ultrathin (3 nm) YBa2Cu3O7−δ film on NdGaO3 substrate and thin (50 nm) film of YBa2Cu3O7−δ on a bicrystal SrTiO3 substrate. While the current‐voltage characteristics of the ultrathin film indicate a Kosterlitz–Thouless transition (associated with vortex–antivortex unbinding) at a temperature TKT, we do not observe any optical response at or below TKT. An enhanced optical response with nonbolometric characteristics was observed from the grain‐boundary as compared to the bolometric optical response of the epitaxial film at the resistive transition. These results indicate that the grain‐boundary weak links play a significant role in the enhanced optical response near Tc.