Miracle-dz/UniFAR-FTUs huggingface dataset:
Electronic band structures and optical gain spectra of strained wurtzite GaN-Al/sub x/Ga/sub 1-x/N quantum-well lasers

The electronic band structures, density-of-states, and optical gain spectra for wurtzite GaN-Al/sub x/Ga/sub 1-x/N quantum wells are studied theoretically based on the Hamiltonian derived using the k.p method. We investigate the dependence of the optical gain and transparent current density on the well width, barrier height, and strain using a numerical approach with high accuracy. The mole fraction of Al in the barrier material is progressively increased to study the effects of quantum confinement and compressive strain. A higher Al mole fraction in the barrier leads to improvement of the TE optical gain and suppression of the TM optical gain. Furthermore, we demonstrate that a reduction of the well width offers improved modal gain over all radiative current densities. We also predict a transparent current density of 250 A/cm/sup 2/ for the GaN-Al/sub x/Ga/sub 1-x/N single quantum-well (QW) structure. Our results suggest that a suitable combination of thin well width and large barrier height should be selected in improving the TE optical gain in wurtzite GaN-Al/sub x/Ga/sub 1-x/N single QW.
On the length of level sets of real functions

Abstract In this paper, we obtain some results in the spirit of Gamma-lines theory (complex analysis) for large classes of real functions f(x,y). In Section 3 our main result describe the length of solutions of f(x,y)=Aν, for arbitrary finite sets of values Aν. This leads to some consequences for real algebraic polynomials P(x,y) in Section 1 and modules |p(z)| of complex polynomials p(z) in Section 2.
Polar P63cm phase as a marginally stable ground-state structure of InMnO3: First-principles study

To resolve a dispute associated with the ferroelectricity in hexagonal InMnO3 (h-IMO), we have examined the ground-state structure by exploiting density-functional theory calculations. It is shown that the ferroelectric phase is marginally stable over the nonpolar phase for a wide range of the external pressure. However, the computed Kohn-Sham energy predicts an interesting crossover from the polar state to the nonpolar state beginning at a compressive strain of ∼1%. The partial density of states (PDOS) supports our previous finding that the In 4d-O 2p hybridization is the main bonding mechanism directly related to the manifestation of ferroelectricity in h-IMO. In addition, the computed PDOS does not show any evidence of the In 5s-O 2p orbital overlapping which had been asserted to be the main bonding interaction in the nonpolar phase.
Digraph Coloring Games and Game-Perfectness

In this thesis the game chromatic number of a digraph is introduced as a game-theoretic variant of the dichromatic number. This notion generalizes the well-known game chromatic number of a graph. An extended model also takes into account relaxed colorings and asymmetric move sequences. Game-perfectness is defined as a game-theoretic variant of perfectness of a graph, and is generalized to digraphs. We examine upper and lower bounds for the game chromatic number of several classes of digraphs. In the last part of the thesis, we characterize game-perfect digraphs with small clique number, and prove general results concerning game-perfectness. Some results are verified with the help of a computer program that is discussed in the appendix.
Photosensitive Schottky-type heterojunctions prepared by the drawing of graphite films

Graphite/n-CdTe Schottky-type heterojunctions were prepared by means of a very simple and low-cost method: the drawing of graphite films on the rough surface of mechanically polished n-CdTe single crystal substrates. The unoptimized heterojunctions showed promising, rectifying, and photoelectrical parameters. The obtained results represent a good starting point for the further development of the simple and low-cost heterojunction photodiodes and gas sensors.
Third-order leader-following consensus with circumstance noise under impulsive and switching control

This research is aimed at investigating the leader–follower problem of third-order multi-agent with noise perturbation over fixed network under impulsive and switching control. Based on stochastic differential equation theory and hybrid control theory, effective impulsive and switching controllers are proposed, and the sufficient conditions for reaching multi-agent leader-following consensus are acquired. Numerical simulations verify the validity of the theoretical research results.
Theory of Multipolar Excitations in CeB6

A theory for the multipolar excitations in the antiferro-quadrupolar (AFQ) phase of CeB 6 is developed. It is based on a pseudo-spin model for the Γ 8 ground state of Ce used previously to explain the B - T phase diagram. An equation of motion method for the multipolar operators is employed and the solutions for the O 2 0 and O x y phases are given. It is shown that the excitation branches are classified as being of mixed quadrupolar-dipolar, quadrupolar-octupolar and octupolar-dipolar character. The former two have strong and the latter only weak dispersion respectively. The transition from the O 2 0 to the O x y phase in the symmetric model is accompanied by the reappearance of a quadrupolar Goldstone mode. In the O x y phase of the asymmetric model some modes are gapped already at zero field and for finite field no Goldstone mode remains. In addition we give a derivation for the dynamical structure function based on the mixing scheme of multipolar excitations and discuss the result for the zero-field case.
Combining speckle reduction and data compression for synthetic aperture radar (SAR) images in wavelet domain

The wavelet transform is widely used in both speckle reduction and dat compression of SAR image. Thus, it is very efficient to integrate these two procedures in a single process. IN this research, an input image is first subject to a logarithmic operation. The image is then transformed by using multi level wavelet decomposition. The variance of noise is estimated from the data to determine the threshold, which is used for soft-thresholding the wavelet coefficients. For each subband, the obtained wavelet coefficients are quantized and finally entropy encoded to produce the output bit stream of the image. The advantage of this method is that both speckle reduction and image compression are performed in wavelet domain. Experimental results on JERS-1/SAR images are also given.
The bound-free photodetachment cross section of H-

The bound-free photodetachment cross section of H- is calculated in the length formulation. The bound-state and free-state wavefunctions are calculated to high accuracy using a close-coupling pseudostate expansion with the addition of Hylleraas-type correlation terms. At lower energies the results agree with those of Stewart (1978), to better than 1%, while at ejected electron energies just below the n=2 excitation threshold the results are within 1% of those of Broad and Reinhardt (1976). The shape resonance just above the n=2 excitation threshold is studied, and the partial photodetachment cross sections are compared with those of Hyman, Jacobs and Burke (1972).
On Existence and Stability of Solutions to Elliptic Systems with Generalised Growth

We are concerned with existence and stability of solutions for system of equations with generalised p(x) and m(x)—Laplace operators and where the nonlinearity satisfies some local growth conditions. We provide a variational approach that is based on investigation of the primal and the dual action functionals. As a consequence we consider the dependence of the the system on functional parameters.
Direct Computation of a Hole-Tone Feedback System at Very Low Mach Numbers

This study is concerned with an investigation into the sound produced when a jet, issued from a circular nozzle or hole in a plate, goes through a similar hole in a second plate. The sound, known as a hole-tone, is encountered in many practical engineering situation. Direct computations and experiments of a hole-tone feedback system are conducted. The mean velocities of the air-jet are 8 and 10 m/s in the computations, and 6-13 m/s in the experiments. The diameters of the nozzle and the end plate hole are both 50 mm, and the impingement length between the nozzle and the end plate is 50 mm. The computational results agree well with the experimental data in terms of the qualitative vortical structures and the relationship between the most dominant hole-tone peak frequency and the jet speed. Based on the computational results of the air-jet speed of 10 m/s, the shear-layer impingement on the hole edge, the resultant propagation of pressure waves, the associated vortical structures and a newly proposed feedback mechanism is discussed. As far as the authors know this is the first direct computation of the hole-tone feedback system that predicts its dominant frequency successfully. Non-axisymmetry observed in the present computation is also shown.
Maximum a posteriori estimation of image boundaries by dynamic programming

Summary. We seek a computationally fast method for solving a difficult image segmentation problem: the positioning of boundaries on medical scanner images to delineate tissues of interest. We formulate a Bayesian model for image boundaries such that the maximum a posterioriestimator is obtainable very efficiently by dynamic programming. The prior model for the boundary is a biased random walk and the likelihood is based on a border appearance model, with parameter values obtained from training images. The method is applied successfully to the segmentation of ultrasound images and X‐ray computed tomographs of sheep, for application in sheep breeding programmes.
A Stochastic Compartmental Model with Long Lasting Infusion

Most of the compartmental models in current use to model pharmacokinetic systems are deterministic. Stochastic formulations of pharmacokinetic compartmental models introduce stochasticity through either a probabilistic transfer mechanism or the randomization of the transfer rate constants. In this paper we consider a linear stochastic differential equation (LSDE) which represents a stochastic version of a one‐compartment linear model when input function undergoes random fluctuations. The solution of the LSDE, its mean value and covariance structure are derived. An explicit likelihood function is obtained either when the process is observed continuously over a period of time or when sampled data are available, as it is generally feasible. We discuss some asymptotic properties of the maximum likelihood estimators for the model parameters. Furthermore we develop expressions for two random variables of interest in pharmacokinetics: the area under the time‐concentration curve, M0(T), and the plateau concentration, xss. Finally the estimation procedure is illustrated by an application to real data.
Can expensive research equipment boost research and development performances?

Research equipment is as essential for researchers as modes of transportation are for travelers. Thus, to ascertain the extent to which research equipment affects research performance, this study employed project and performance information to examine the relationships between the quality and quantity of papers and patents and the presence and prices of research equipment for research and development (R&D) projects supported by the Korean government from 2011 to 2014 using the Heckman selection model. We discovered that (1) when the equipment was directly constructed using the R&D budget of a project, it had a positive influence on both papers and patents. Further, (2) equipment prices had negative impacts on papers and patents. At the individual R&D project level, understanding of input and output processes ensures project accountability and improvement. This study presents a new perspective on allocation of public R&D resources and promotes improvement in R&D project results using research equipment.
Use Of Ukrainian Semiconductor Dosimeters In A CERN Particle Accelerator Field

The results of the application of p-i-n and MOS dosimeters in the PS-ACOL Irradiation Facility (PSAIF) at CERN for separate measurements of gamma dose and fast neutron fluences are presented. The mixed gamma-neutron field was due to 26 GeV protons hitting an iridium target, yielding an instantaneous dose rate of approximately 3.10/sup 5/ Gy/s. Good agreement with calibration curves is found for MOS in a /sup 60/Co gamma source as well as for p-i-n sensors in a neutron reactor spectrum with mean energy of 1 MeV. Experimental results from PSAIF are presented and pulse current injection annealing of p-i-n diodes is considered. Such sensors are very convenient for on-line separated total dose measurements in mixed gamma-neutron radiation fields, as well as for radiation hardness testing of electronics. Components on irradiation facilities, and could be installed near the detector area of the LHC. >
A novel friction law

Frictional force is a vitally important factor in the application of engineering either in macroscopic contacts or in micro/nanoscale contacts. Understanding of the influencing factors about frictional force is essential for the design of miniaturized devices and the use of minimal friction force. In the paper, dimensional analysis is used to analysis factors relative to frictional force. We show that the frictional force scales with where A is the contact area and N is the normal contact force. An experiment is carried out to verify the new friction law.
Optimal Power Flow Solution Using the Harmony Search Algorithm

Inthis paper, the nonlinear optimal control problem is formulated as amulti-objective mathematical optimization problem. Harmony search (HS)algorithm is one of the new heuristic algorithms. The harmony search(HS) optimization algorithm is introduced forthe first time in solving the optimal power flow(OPF) solution. A case onoptimal power flow problem in the IEEE 30 bus system is presented to show themethodology’s feasibility and efficiency, compared with the existing optimalpower flow problem in power system methods, the search time of the HSoptimization algorithm is shorter and the result is close to the idealsolution, simultaneously.
Hard x-ray contact microscopy with 250 nm spatial resolution using a LiF film detector and a tabletop microsource

An innovative route for deep-submicrometer spatial resolution hard x-ray microscopy with tabletop x-ray source is proposed. A film of lithium fluoride (LiF) was used as imaging detector in contact mode. We present here the x-ray images recorded on LiF films of a Fresnel zone plate with submicrometer gold structures and of an onion cataphyll. The images were read with an optical confocal microscope in fluorescence mode. The measured spatial resolution was about 250nm, i.e., close to the resolution limit of the confocal microscope. The advantages and drawbacks, and the possible improvements, of this route are discussed.
Directional Error Rates of Closed Testing Procedures

Closed multiple testing procedures are common in biopharmaceutical protocols. Whether their directional error rates are controlled is largely an open problem. In this article, directional error rates are investigated using analytical, numerical, and Monte Carlo methods. This article presents a Monte Carlo variance-reduction method amenable to this purpose. A factorial design is used to identify possible problem areas, and directional error rates are simulated. No cases of excess directional error are found for typical applications involving noncentral multivariate T distributions. However, directional error rates in excess of the nominal are found when using regression function tests with nearly collinear linear combinations, both for one-sided and two-sided tests.
Investigation of single and double electron capture in Ar7+ – He, H2 collisions at 105 keV by photon spectroscopy

A thorough analysis of photon spectra in the 2000-6000 A wavelength range for the 105 keV Ar7+ - He, H2 collision systems is presented. Numerous lines due to single and double electron capture processes were observed. They have been interpreted with the help of experimental data and ab initio calculations. For the single electron capture process, transitions with Δn = 0 for n = 4 and n = 5 states of Ar VII have been identified. Fine structure splittings of the 3s5p 3P and 3s5d 3D terms have been determined. Strong lines due to the double electron capture process were observed and identified as Rydberg transitions 3s2nl-3s2n'l' or 3s3p(3P, 1P)nl-3s3p(3P, 1P)n'l' in Ar VI. Photon emission cross sections for individual lines are given.
Cool Gas in the Virgo Cluster?

Galaxy clusters often contain hot intergalactic gas that emits x-rays. In his Perspective, Fabian discusses recent results by Lieu et al. [Astrophys. J. 458, L5 (1996)] showing an unusually high amount of x-radiation at lower energies. This could be the signature of a cooler component to the intergalactic gas, which may require reexamination of current cluster models.
Time reversal selection rules and gauge invariance in nonlinear optics

Selection rules in nonlinear optics which are associated with time reversal (T) symmetry are reviewed, corrected and extended. For example, we find that both in fluids and in the nonresonant limit all nonlinear optical transitions between T-conjugate states are forbidden in Kramers systems. We show that further restrictions exist in the nonresonant limit with regard to the group symmetries of the associated effective transition operator. These and other rules generalize results found in Rayleigh and Raman scattering to nonlinear optical processes of arbitrary order. As in Judd - Ofelt theory, a careful treatment is required to obtain gauge-invariant conclusions since the relevant electronic operators in velocity and position gauges have opposite HT signatures.
A COTS high-performance real-time control system for adaptive optics

The advent of high performance multi-core processors in desktop computers has opened the door for high performance, yet easy to maintain and upgrade, adaptive optics control systems. We describe the Durham Adaptive Optics Real-time Controller, and give details of performance, including latency and jitter, and maximum frame rates as well as scalability with adaptive optics system size. This system is to be used as a laboratory test bench in Durham with low and high order (up to 32×32 actuators) systems, and also on-sky as a control system for a WHT MOAO demonstrator instrument.
A vortex filament moving without change of form

The motion of a very thin vortex filament is investigated using the localized induction equation. A family of vortex filaments which move without change of form are obtained. They are expressed in terms of elliptic integrals of the first, second and third kinds. In general they do not close and have infinite lengths. In some particular cases they take the form of closed coils which wind a doughnut. There exist a family of closed vortex filaments which do not travel in space but only rotate around a fixed axis. Our solutions include various well-known shapes such as the circular vortex ring, the helicoidal filament, the plane sinusoidal filament, Euler's elastica and the solitary-wave-type filament. It is shown that they correspond to the travelling wave solution of a nonlinear Schrödinger equation.
Objective measures for quality assessment of automatic skin enhancement algorithms

Automatic portrait enhancement by attenuating skin flaws (pimples, blemishes, wrinkles, etc.) has received considerable attention from digital camera manufacturers thanks to its impact on the public. Subsequently, a number of algorithms have been developed to meet this need. One central aspect to developing such an algorithm is quality assessment: having a few numbers that precisely indicate the amount of beautification brought by an algorithm (as perceived by human observers) is of great help, as it works on circumvent time-costly human evaluation. In this paper, we propose a method to numerically evaluate the quality of a skin beautification algorithm. The most important aspects we take into account and quantize to numbers are the quality of the skin detector, the amount of smoothing performed by the method, the preservation of intrinsic skin texture, and the preservation of facial features. We combine these measures into two numbers that assess the quality of skin detection and beautification. The derived measures are highly correlated with human perception, therefore they constitute a helpful tool for tuning and comparing algorithms.
Solar Pressure Variable Structure Model Reference Adaptive Spacecraft Attitude Control in Elliptic Orbits

[Abstract] Based on the variable structure model reference adaptive control (VS-MRAC) theory, a new adaptive control system for the attitude control of satellites in elliptic orbits with uncertain dynamics, using solar radiation pressure (SRP), is derived. The nonaffine-incontrol nonlinear spacecraft model includes the gravity gradient torque, the control torque produced by two solar flaps, and external time-varying disturbance torque. The objective here is to derive a control law for the pitch attitude control using the pitch angle and pitch rate feedback. For the trajectory tracking of the pitch angle, a variable structure model reference adaptive attitude control system, including two relays and linear filters, is designed. Although, the modulation functions of the relays are functions of certain auxiliary signals, for simplicity in implementation, these functions are assigned constant values. Simulation results are presented which show that the simplified VS-MRAC law accomplishes precise attitude control of the spacecraft, despite unmodelled (unstructured) nonlinearities, parameter uncertainty and external disturbance torque in the model.
On geometric phases and dynamical invariants

A formalism is developed for calculating Berry phases for nonadiabatic time-periodic quantum systems when a dynamical invariant is known. It is found that, when the invariant is periodic and has a nondegenerate spectrum, this method allows a convenient way to obtain generalized Berry phases and the proper cyclic initial states. The method is applied to the generalized harmonic oscillator and the two-level system, where the invariant operators are explicitly constructed. Formulae for the conventional Berry's phases are readily obtained by taking the adiabatic limit of the exact results.
Experimental study of the dependence of the damping rate of n = 1 TAEs on the on-axis safety factor and toroidal rotation shear

The dependence of the measured damping rate (γ/ω) on the value of the safety factor on axis (q0) and of the toroidal rotation shear has been experimentally determined for n = 1 toroidal Alfvén eigenmodes (TAEs) in JET limiter plasmas with a monotonic safety factor profile and low edge magnetic shear. For q0 < 1, the n = 1 TAE damping rate can reach values up to γ/ω > 8%, whereas for q0 > 1.1, γ/ω < 2% for similar experimental conditions. The existence of these two separate regimes is suggestive of a possible role of the sawteeth on the damping of low-n TAEs, for example, via a redistribution of the core plasma current, which would, in turn, affect the magnetic shear profile. The value of the toroidal rotation shear affects the n = 1 TAE damping rate only at high neutral beam injection power (PNBI): for PNBI > 6.5 MW we find that γ/ω > 2% in plasmas with a higher rotation shear, whereas for lower PNBI we do not observe any appreciable effect of the rotation shear on the damping rate. These observations indicate that different damping mechanisms for low-n TAEs may be active at low and high performance.