Miracle-dz/UniFAR-FTUs huggingface dataset:
Equivalent-Circuit Analysis for the Electroluminescence-Efficiency Problem of InGaN/GaN Light-Emitting Diodes

Electroluminescence (EL) efficiency of the InGaN-based light-emitting diode (LED) is the present subject of discussion. An equivalent circuit model was introduced to treat explicitly four independent current components: leakage, radiative, nonradiative, and carrier overflow. This model was used to explain the internal quantum efficiency (IQE) as a function of current, temperature, and material quality. In the low-current range, efficiency became strongly dependent on temperature as leakage and nonradiative recombination currents related to material quality shared a large part of the total current. In the high-current range, the reduced efficiency was explained by electron-overflow current. Electron-overflow current was increased by reducing temperature via freeze-out of holes. When leakage current and carrier overflow were suppressed effectively in the intermediate current range on high-quality devices, hole freeze-out was observed experimentally in electroluminescence intensity as temperature was varied.
Computation of Turbulent Flow through Constrictions

The turbulent flow through an axisymmetric constriction in a tube is studied using the k‐e. turbulence model where k is the turbulence kinetic energy and e is its dissipation rate. A new algorithm is used to solve the difference equations obtained from k and e transport equations simultaneously, leading to faster convergence of the numerical scheme. The results are compared with the experimental data obtained using a laser Doppler anemometer. The turbulence model predicts mean velocity reasonably well upstream of the constriction but falls short in its ability downstream of the constriction. The model does not predict the turbulence kinetic energy accurately. The model correctly predicts the presence of a recirculating region. However, this region is found to be thinner and shorter than the one measured experimentally.
Accreting white dwarf models for type 1 supernovae. II - Off-center detonation supernovae

Supernova models based on accreting carbon-oxygen white dwarfs are presented. In these models, the explosion is triggered by the strong helium shell flash which occurs when the accretion forms a helium layer of substantial mass. The hydrodynamical behavior of the helium shell flash is computed through the explosion for three cases with different accretion rates.
Scanning microdeformation microscopy: experimental investigations on non-linear contact spectroscopy

In ac contact force microscopy, different kinds of set-ups derived for the most part from atomic force microscopes have been developed in the last ten years in spectroscopy mode, in order to investigate the local elastic properties of materials in the nanometre range. In most cases, quantitative results are delicate to obtain due to local forces such as atomic, capillary or adhesion, which are dominant on this scale between the tip and the sample. Generally the non-linear dependence of these forces on the distance is linearized in a small region of the interaction force response. We propose in this study the investigation of the non-linear regime of the tip–sample interaction with our mesoscopic scanning probe microscope, called scanning microdeformation microscope. Due to the operating range, only the Hertzian contact has been considered. This non-linear regime is observed in the case of high static loads on the sample or by increasing the excitation amplitude of the tip. More particularly, we have quantitatively measured with a high heterodyne interferometer the response directly on the sample in the vicinity of the vibrating tip. The detection of the spectra clearly shows the generation of higher harmonics in this situation. Different harmonic signatures have been measured depending on the elastic properties of the materials.
The nature of field emission from microparticles and the ensuing voltage breakdown

In recent years there has been much progress in furthering our understanding of the sources of field emission as well as in tracing the stages from field emission to voltage breakdown. These advances come from microscopic studies (scanning electron microscopy, energy dispersive x-ray analysis, Auger spectroscopy) of field emitters located by DC high voltage scans as well as from field emitters found in microwave cavities. Craters, residues and starbursts found at breakdown sites reveal much about the physics of voltage breakdown. Both experiments and computer simulations show the important role played by gases generated by field emission induced heating.
Multispectral image classification using a mixture density model

This paper describes a multispectral image classification technique. This technique involves two steps. First, we describe the underlying distribution of the pixel intensity vectors for the entire scene as a mixture of multivariate Gaussian distributions. We then use this mixture decomposition and a small number of labeled pixels to estimate the proportion of a mixture component that is comprised of a certain class, which enables us to use a Bayes-type decision rule to classify each pixel in the scene. Results of applying this technique to three-band SPOT data are presented. Comparisons with results obtained from a maximum likelihood classifier are also presented.
Charm at HERA I and HERA II with the ZEUS experiment

Inclusive jet cross sections in photoproduction for events containing a D* meson have been measured with the ZEUS detector at HERA using an integrated luminosity of 78.6 pb_1. The events were required to have a virtuality of the incoming photon, Q2, of less than 1 GeV2, and a photon-proton centre-of-mass energy in the range 130 < Wlp < 280 GeV. The measurements are compared with next-to-leading-order (NLO) QCD calculations. Good agreement is found with the NLO calculations over most of the measured kinematic region. Requiring a second jet in the event allowed a more detailed comparison with QCD calculations. The measured dijet cross sections are also compared to Monte Carlo (MC) predictions which incorporate leading-order matrix elements, followed by parton showers and hadronisation. The NLO QCD predictions are in general agreement with the data although differences have been isolated to regions where extra parton radiation is present. The MC models give a better description of the shape of the measured cross sections. This thesis ends with a look at the first HERA II data. The decay of D mesons were studied and for the first time the newly installed micro vertex detector (MVD) was used to tag charm mesons using secondary vertices arising from the decay of (c * D or b * c * D). This shows that the MVD will be a powerful tool in the future analyses of heavy quark production at ZEUS.
Thermal conductivity of graphene nanoribbons

We have investigated the thermal conductivity of graphene nanoribbons (GNRs) with different edge shapes as a function of length, width, and strain using nonequilibrium molecular dynamics method. The initial GNR for the functional variations has dimensions of 2×11 nm2. Strong length dependence of thermal conductivity is obtained, indicating high thermal conductivities of GNRs, which is consistent with the experimental results for graphene. A tensile/compressive uniaxial strain can remarkably decrease the thermal conductivity of GNR.
Active control of a turbulent boundary layer based on local surface perturbation

Abstract Active control of a turbulent boundary layer has been experimentally investigated with a view to reducing the skin-friction drag and gaining some insight into the mechanism that leads to drag reduction. A spanwise-aligned array of piezo-ceramic actuators was employed to generate a transverse travelling wave along the wall surface, with a specified phase shift between adjacent actuators. Local skin-friction drag exhibits a strong dependence on control parameters, including the wavelength, amplitude and frequency of the oscillation. A maximum drag reduction of 50 % has been achieved at 17 wall units downstream of the actuators. The near-wall flow structure under control, measured using smoke–wire flow visualization, hot-wire and particle image velocimetry techniques, is compared with that without control. The data have been carefully analysed using techniques such as streak detection, power spectra and conditional averaging based on the variable-interval time-average detection. All the results point to a pronounced change in the organization of the perturbed boundary layer. It is proposed that the actuation-induced wave generates a layer of highly regularized streamwise vortices, which acts as a barrier between the large-scale coherent structures and the wall, thus interfering with the turbulence production cycle and contributing partially to the drag reduction. Associated with the generation of regularized vortices is a significant increase, in the near-wall region, of the mean energy dissipation rate, as inferred from a substantial decrease in the Taylor microscale. This increase also contributes to the drag reduction. The scaling of the drag reduction is also examined empirically, providing valuable insight into the active control of drag reduction.
Rigid Plastic Beam Model for Pipe Whip Analysis

A method is developed for the analysis of a rigid-plastic propped cantilever beam with a gap at the support for use in the study of pipe whip. The blowdown thrust is assumed to be a suddenly applied constant force and the restraint is assumed to act as a rigid-plastic spring. The type of response is shown to depend on the lengths of the cantilever and the segment overhanging the restraint as well as the ratio of the blowdown thrust to the restraint reaction. In long cantilevers, the first hinge to form moves to the support after contact is made with the restraint. A second hinge will form at the restraint if the reaction is large enough. It is shown that if the cantilever is long enough and the restraint reaction above a certain critical value, the displacements at the tip and the restraint are independent of length. It is shown that neglecting the fact the hinge moves introduces large errors.
UV-250 patterning of sub-micron tapered active layers

This paper reports the first results on Fabry-Perot 1.3 /spl mu/m lasers with sub-micron tapered active layers defined using a UV-250 patterning technology in combination with conventional RIE processing of InP. Its implementation to the full 2 inch wafer process flow is of interest in low cost module fabrication. Short lasers (500 /spl mu/m) with low coupling loss (3.4 dB with end cleaved fiber) and high quantum efficiency (0.26 W/A at 85/spl deg/C) are demonstrated.
RADIATIVE CORRECTIONS TO HIGGS MASSES IN THE SUPERSYMMETRIC MODEL WITH AN EXTRA FAMILY AND ANTI-FAMILY

Radiative corrections to Higgs masses are calculated in a supersymmetric standard model with an extra family and its mirror partners. These corrections, in general, depend on the mass spectrum of fermions, bosons and the strength of Yukawa couplings of the extra families. If we assume that the Yukawa couplings do not blow up below the GUT scale, the upper bound of the lightest Higgs mass increases about 12 GeV. We also notice that, in some cases, the charged Higgs mass becomes lighter than that of the tree level prediction.
Fast and slow magnetosonic waves in two-dimensional spin-1/2 quantum plasma

Using the spin-1/2 resistive quantum magnetohydrodynamics model, linear and nonlinear relations for slow and fast magnetosonic modes are derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The plasma resistivity is shown to play a role of dissipation in the system. With the aid of tanh method the traveling wave solution of Kadomstev–Petviashvili–Burgers is obtained. The solution shows a general shock wave profile superposed by a perturbative solitary-wave contribution. The dynamics of fast and slow magnetosonic shock and soliton, respectively, in the presence and absence of dissipation is investigated with respect to electron spin magnetization, quantum diffraction, and plasma statistic. It is found that results obtained from the spin quantum plasmas differ significantly from the nonspin quantum plasmas. The relevance of the present work to dense astrophysical plasmas such as pulsar magnetosphere is pointed out.
Supernovae. Part I: The events

Since the heroic era of Baade and Zwicky, our understanding of supernovae has advanced in hops and skips rather than steadily. The most recent jump has been into fairly general agreement that observations of Type I's can be interpreted as the manifestation of the decay of about 1M of Ni56 and observations of Type II's as the manifestation of 1051 ergs deposited at the bottom of a supergiant envelope by core bounce as a central neutron star forms. This paper explores the history of these and other ideas of what is going on in supernovae, the presupernova evolution of the parent stars and binary systems, observed properties of the events, and models for them. A later paper (Part II: the aftermath) will address the results of supernovae-their remnants, production of cosmic rays and gamma rays, nucleosynthesis, and galactic evolution-and the future of supernova research. © 1982 The American Physical Society.
Bayesian Theory of Games: A Statistical Decision Theoretic Based Analysis of Strategic Interactions

Bayesian rational prior equilibrium requires agent to make rational statistical predictions and decisions, starting with first order non informative prior and keeps updating with statistical decision theoretic and game theoretic reasoning until a convergence of conjectures is achieved. The main difference between the Bayesian theory of games and the current games theory are: I. It analyzes a larger set of games, including noisy games, games with unstable equilibrium and games with double or multiple sided incomplete information games which are not analyzed or hardly analyzed under the current games theory. II. For the set of games analyzed by the current games theory, it generates far fewer equilibria and normally generates only a unique equilibrium and therefore functions as an equilibrium selection and deletion criterion and, selects the most common sensible and statistically sound equilibrium among equilibria and eliminates insensible and statistically unsound equilibria. III. It differentiates between simultaneous move and imperfect information. The Bayesian theory of games treats sequential move with imperfect information as a special case of sequential move with observational noise term. When the variance of the noise term approaches its maximum such that the observation contains no informational value, there is imperfect information (with sequential move). IV. It treats games with complete and perfect information as special cases of games with incomplete information and noisy observation whereby the variance of the prior distribution function on type and the variance of the observation noise term tend to zero. Consequently, there is the issue of indeterminacy in statistical inference and decision making in these games as the equilibrium solution depends on which variances tends to zero first. It therefore identifies equilibriums in these games that have so far eluded the classical theory of games.
Sequential image coding based on multiresolution tree architecture

A new image sequence coding scheme based on the multiresolution tree structure is proposed. It not only guarantees reliable and homogeneous motion field, but also reduces the amount of computation necessary in the motion vector search. With nearly the same decoded image quality, 25–30% bit rate reduction can be obtained compared with the MPEG–I algorithm.
Reading the patterns in living cells —the physics of ca2+ signaling

Ca2+ is one of the most important messengers. It transmits signals inside living cells and takes part in intercellular coordination. The dynamics of the Ca2+ concentration shows a transition from elemental, stochastic events to global events like waves and oscillations. This transition renders it an ideal tool for studying basic concepts of pattern formation, especially since access to the most important experimental parameters is given. Ca2+ dynamics in living cells has been a major topic of biophysical modelling in the last 15 years. Modelling has reached the level of predictive power. The theoretical analysis of waves provided new insight into the mechanisms of Ca2+ signaling and led to new concepts of analysis of wave equations with concentration dependent diffusion and novel wave bifurcations. Modelling of oscillations provided understanding especially of complex oscillations and allowed to extract information about the underlying cellular parameters and mechanisms. The investigation of the stochastic aspects of intracellular Ca2+ dynamics demonstrated the fundamental role of fluctuations arising from the control of the release channel by Ca2+ and IP3. This review presents an overview of current theoretical research on Ca2+ dynamics in living cells driven by the inositol 1,4,5-trisphosphate receptor channel.
Composite kernels conditional random fields for remote-sensing image classification

The problem of classifying a remote-sensing image by specifically labelling each pixel in the image is addressed. A novel method, named composite kernels conditional random field (CKCRF), which embeds multiple kernels into a classical CRFs model is proposed. Rather than manually selecting kernel-like KCRF, CKCRFs chooses the appropriate kernel by training. Moreover, a genetic programming-based decision-level fusion framework is proposed to tackle the problem of feature selection. It can select the appropriate features suitable to each category. Evaluations show that CKCRFs outperform CRFs and KCRFs, and CKCRFs with the fusion scheme is better than that without the fusion step.
The multiple-input minimal time regulator problem (General theory)

This work considers a two-input linear time-invariant discrete system whose state transition equation is given by X_{k+1} = AX_{k} + Du_{k+1} where A = n \times n constant nonsingular matrix; x k is an n -rowed state vector of the system at t=kT ; D is an n \times 2 constant control matrix with columns d 1 and d 2 ; and u_{k+1} is a 2-rowed control vector with components u^{1}_{k+1} and u^{2}_{k+1} . The control vector u_{k+1} is restricted to be an admissible control, i.e., |u^{i}_{k+1}| \leq 1 for i=1, 2 and k=0, 1, . The two-input minimal time regulator problem may be stated as follows 1) Given any arbitrary initial state of the system, find admissible control vectors u_{1}, u_{2}, . which will bring the system to equilibrium (i.e., the state x=0 ) in the minimum number of sampling periods. 2) Determine an optimal strategy, i.e., determine a vector valued function u^{0}(x) of the state x such that if the system is in state x at a sampling instant, u^{0}(x) is an admissible optimal control for the next sampling period. First, the general necessary and sufficient conditions for the system to be controllable with admissible controls are established. For a controllable system it is shown that the optimal strategy at each sampling instant requires the following: For each component u^{i}_{k+1} , i=1, 2, there exists a unique (n-1) -dimensional hypersurface \varepsilon^{i} , i=1, 2 . The optimal strategy u^{0}(x_{k+1}) is then a simple nonlinear function of each of the λ i 's where λ i is the distance of x 0 from \zeta^{i} along a direction parallel to A^{-1}d_{i} , for i=1, 2 . This optimal strategy therefore satisfies the operations of the feedback computer in order that the system returns to equilibrium in minimum time after any arbitrary disturbances. The results of this work are applicable to all discrete systems of the above form which are controllable by admissible controls irrespective of whether the eigenvalues of A are distinct or multiple, real or occur in complex conjugate pairs. Furthermore, the theory is directly extendable to the case where D=n \times m constant matrix and u_{k+1} is an m -rowed control vector; m > 2 , subject to the admissibility constraint |u^{i}_{k+1}| \leq 1, i=1, 2, . , m .
Identification of inhomogenous optical absorptive response by chaotic photonic signals in Au nanoparticles

A chaotic circuit allows us to identify with a high sensitivity the optical absorption associated with a highly transparent sample with Au nanoparticles embedded in a TiO2 thin film prepared by a sol–gel method. The measurements are based on a comparison of the correlation between a controlled optical irradiance that propagates through different zones of the sample. Nanosecond nonlinear optical measurements were obtained by monitoring the transmittance and the amplitude modification for the vectorial components of the electric fields in a two-wave mixing interaction. In addition, we theoretically study chaotic physical behavior exhibited by optical signals under nonlinear optical absorption. Our numerical results point out that small intensity fluctuations related to excitations of the absorptive nonlinearity can be described using a simple fractal model. Potential applications for developing sensors and instrumentation of the optical response of advanced materials are contemplated.
Threshold of Hearing and Equal‐Loudness Relations for Pure Tones, and the Loudness Function

During recent years a program of work has been in progress at the National Physical Laboratory with the objective of providing improved data on several aspects of subjective acoustics. In connection with standards for audiometry, measurements have been made of the threshold of hearing for pure tones by earphone listening, and these have since been extended to the case of listening in free field. Latterly a redetermination of the equal‐loudness relations for pure tones has been completed aimed at resolving discrepancies between former determinations and providing an improved basis for the establishment of a standard set of contours. These results apply to a large team of otologically normal observers, and cover the range from 25–15 000 cps and up to 130 db in sound pressure level. The results of this investigation enable the equivalent loudness of any pure tone to be expressed by simple formulas with coefficients varying smoothly with frequency. Considerable attention has also been devoted to the determination of the loudness scale, i.e., the function relating loudness level in phons to the magnitude of the loudness sensation expressed on the sone scale. An assessment of the experimental evidence has led to the formulation of a simple relation which appears adequate for practical purposes in noise measurement. Investigations are continuing on the determination of loudness levels of complex sounds from their objective spectra.
Simulation of circuits of functional elements by the universal Turing machine

We study the time of simulation of Boolean circuits by three-tape Turing machine which uses one of the tapes to store the control program. We find that for any circuit S there exists a program P such that the simulation time T(P) for the circuit S satisfies the relation T(P) = O(L(S) log2 L(S)), where L(S) is the complexity of the circuit S. We demonstrate that this estimate is sharp.
Magneto‐Optical Effects

The general theory of magneto‐optical effects is reviewed and it is shown that one can describe these phenomena in terms of a macroscopic dielectric tensor by setting μ=1. This is true even when the microscopic origins of the dielectric constant are magnetic‐dipole transitions. For the case of electric‐dipole transitions, the dispersive magneto‐optical effects (i.e., Faraday or Voigt effects) can be interpreted in terms of an effective Hamiltonian which is related to the macroscopic dielectric tensor in a very simple manner. The form of this effective Hamiltonian follows from symmetry considerations. From the measurements of the magneto‐optical effects, one determines the constants of the effective Hamiltonian and from these one can predict the cross section for Raman scattering of light by spin excitations.