Miracle-dz/UniFAR-FTUs huggingface dataset:
Data assimilation into nonlinear stochastic models

With very few exceptions, data assimilation methods which have been used or proposed foruse with ocean models have been based on some assumption of linearity or near-linearity. Thegreat majority of these schemes have at their root some least-squares assumption. While onecan always perform least-squares analysis on any problem, direct application of least squaresmay not yield satisfactory results in cases in which the underlying distributions are significantlynon-Gaussian. In many cases in which the behavior of the system is governed by intrinsicallynonlinear dynamics, distributions of solutions which are initially Gaussian will not remain soas the system evolves. The presence of noise is an additional and inevitable complicating factor.Besides the imperfections in our models which result from physical or computational simplifyingassumptions, there is uncertainty in forcing fields such as wind stress and heat flux which willremain with us for the foreseeable future. The real world is a noisy place, and the effects ofnoise upon highly nonlinear systems can be complex. We therefore consider the problem ofdata assimilation into systems modeled as nonlinear stochastic differential equations. When themodels are described in this way, the general assimilation problem becomes that of estimatingthe probability density function of the system conditioned on the observations. The quantitywe choose as the solution to the problem can be a mean, a median, a mode, or some otherstatistic. In the fully general formulation, no assumptions about moments or near-linearity arerequired. We present a series of simulation experiments in which we demonstrate assimilationof data into simple nonlinear models in which least-squares methods such as the (Extended)Kalman filter or the weak-constraint variational methods will not perform well. We illustratethe basic method with three examples: a simple one-dimensional nonlinear stochastic differentialequation, the well known three-dimensional Lorenz model and a nonlinear quasigeostrophicchannel model. Comparisons to the extended Kalman filter and an extension to the extendedKalman filter are presented. DOI: 10.1034/j.1600-0870.1999. t01-2-00002.x
Photoluminescence and photoconductive characteristics of hydrothermally synthesized ZnO nanoparticles

In the present paper, ZnO nanoparticles (NPs) with particle size of 20–50 nm have been synthesized by hydrothermal method. UV-visible absorption spectra of ZnO nanoparticles show absorption edge at 372 nm, which is blue-shifted as compared to bulk ZnO. Photoluminescence (PL) and photoconductive device characteristics, including field response, light intensity response, rise and decay time response, and spectral response have been studied systematically. The photoluminescence spectra of these ZnO nanoparticles exhibited different emission peaks at 396 nm, 416 nm, 445 nm, 481 nm, and 524 nm. The photoconductivity spectra of ZnO nanoparticles are studied in the UV-visible spectral region (366–691 nm). In spectral response curve of ZnO NPs, the wavelength dependence of the photocurrent is very close to the absorption and photoluminescence spectra. The photo generated current, Ipc = (Itotal - Idark) and dark current Idc varies according to the power law with the applied field IpcαVr and with the intensity of illumination IpcαILr, due to the defect related mechanism including both recombination centers and traps. The ZnO NPs is found to have deep trap of 0.96 eV, very close to green band emission. The photo and dark conductivities of ZnO NPs have been measured using thick film of powder without any binder.
Achieving large macroscopic compressive plastic deformation and work-hardening-like behavior in a monolithic bulk metallic glass by tailoring stress distribution

The limited plastic deformation and lack of work hardening seriously restrict the applications of bulk metallic glasses (BMGs). Here, large macroscopic compressive plastic deformation (over 15%) and work-hardening-like behavior were achieved in a monolithic BMG through tailoring loading stress distribution experimentally. Numerical analysis was also carried out to investigate the stress distribution under the same mechanical condition. It is shown that loading induced stress gradient is responsible for the achievement mentioned above.
Newly Added Construction Land Information Extraction Method for High-Resolution Remote Sensing Images Based on Weakening of the Negative Sample Weight

Information regarding newly added construction land can be extracted from high-resolution remote sensing images. The retrieval accuracy of land cover changes across the country has improved, and the illegal use of land is actively monitored. To address the imbalance between positive and negative training samples in extracting information regarding newly added construction land, a method for identifying newly added construction land by weakening the weight of negative samples was proposed. A focal loss function was used to weaken the negative samples’ weights and improve the overfitting U-net. Since the two parameters of the focal loss function are not independent of each other, they need to be selected at the same time. Therefore, this paper developed a formula for selecting the balance factor α based on a large number of experimental results. First, the GF-2 image was combined with the historical land change survey data and monitoring vector results to construct a dataset, and then the training dataset was input into a fully convolutional neural network (CNN) integrated with feature fusion and a focal loss function. Finally, the accuracy of the trained network model was verified. To demonstrate the applicability of the method of determining the parameters of the focal loss function, the validation set was divided into four subsets for accuracy verification. The experimental results showed that the F1-score of newly added construction land information extracted by this method reached 0.913, which is 0.078 and 0.033 higher than those of the U-net and the improved U-net. The parameters obtained by the method proposed in this study achieved the best results on the four verification sets, which shows that the method for extracting newly added construction land information and that for selecting parameters have strong applicability.
An intuitionistic fuzzy DEMATEL methodology for prioritising the components of SWOT matrix in the Iranian insurance industry

Strengths, weaknesses, opportunities and threats (SWOT) analysis is one of the most significant analytic tools for defining corporate strategies. In spite of its popularity and common use, it has many drawbacks such as lack of quantitative basis for identifying the most important internal and external factors. In this paper, we propose a methodology based on decision-making trial and evaluation laboratory (DEMATEL) technique which can deal with the causal relationships among factors to overcome this problem. Also, in order to embrace the vagueness of human's subjective judgments we take advantage of intuitionistic fuzzy sets (IFS) theory. Finally, we applied our methodology in one of the Iranian insurance company to determine the most important components of SWOT matrix. The results determined 15 prioritised components of SWOT matrix out of 23 elements which were previously identified by our expert team. The resulting components can be utilised for defining effective strategies of the case company.
New strategies to improve the luminescence efficiency of Eu ions embedded in Si-based matrices

The comparison of the performances of SiO2 and SiOC layers as host matrices for optically active Eu ions is presented. A SiO2 matrix allows to observe light emission from both Eu2+ and Eu3+ ions, owing to a proper tuning of the thermal annealing process used for the optical activation of the rare earth. However, the photoluminescence efficiency of both ions remains relatively low and quite far from the requirements for technological applications, mainly due to the extensive formation of Eu-containing precipitates. A detailed study by transmission electron microscopy allowed us to analyze and elucidate the clustering process and to find suitable strategies for minimizing it. We found that the substitution of SiO2 matrix with a SiOC film allows to obtain a very bright light emission centered at about 440 nm from Eu2+ ions. In fact, SiOC is able to efficiently promote the Eu3+ → Eu2+ reduction; furthermore, Eu ions are characterized by an enhanced mobility and solubility in this matrix, and as a consequence,.
Efficient Fourier image analysis algorithm for aligned rectangular and trapezoidal wafer structures

We present an efficient algorithm to compute the critical dimensions of aligned rectangular and trapezoidal wafer structures using images generated by a Fourier imaging system. We show that the Fourier images of aligned rectangular and trapezoidal structures are separable functions. This allows us to project them onto x and y coordinates and simplifies the computation process. We compute the critical dimensions of rectangular structures by estimating the distance between either peaks or zeros, or by estimating the distance between zeros for trapezoidal structures. For each projected 1-dimensional signal, we apply a zero- crossing technique to find the peaks or zeros, and then compute the critical dimensions at sub- pixel resolution.
IGR J17497-2821 : a new X-ray nova

Context. A new hard X-ray transient has been discovered by INTEGRAL on 2006 Sep. 17 at 1 degree from the Galactic Centre. Aims. INTEGRAL , Swift /XRT and optical photometric observations are used to characterize IGR J17497–2821 and to unveil its nature. Methods. The X-ray position has been refined to arcsec level through a study of the optical variability of the possible counterparts. Hard X-ray variability and spectroscopy are used to determine the nature of the source outburst. Results. IGR J17497–2821 is a new X-ray Nova in low-hard state, probably a new Black-Hole Candidate.
An adaptive control procedure for a fuzzy quality characteristic

A new adaptive economic control scheme for a fuzzy quality characteristic is introduced in this paper. The control scheme includes a sampling interval, a sample size, and an action that are all variable. It minimises the total cost of a multistage process over a short production run. The state of the process is described via a membership function and the aggregate fuzzy membership function of the sample is used instead of commonly used measures of centrality. This scheme, originally designed for an actual industrial case, can be applied to a variety of manufacturing processes where the quality characteristic of interest is fuzzy or where the sampling outcome is expressed via linguistic variables. Extensive computational results show that it brings about sizeable savings. In particular, it is less costly than schemes where the static control limits are based on the fuzzy mean deviation and two-way classification economic adaptive control schemes.
Tip-geometry enhanced cooling of field emission from the n-type semiconductor

The cooling effect of field emission from an n-type semiconductor was theoretically investigated in quest for a solid state cooler. The vacuum potential was exactly expressed in terms of the semiconductor cathode geometry. This leaded to the more accurate configuration-dependent calculations of the energy exchange and the cooling power. It has been shown that a sharper tip of semiconductor can yield either a larger field emission current density or a larger energy exchange, according to the applied bias. For an atomic size tip, the n-Si cathode yielded the cooling power density Γ = 2.0, 75, and 713 W/cm2 at temperature T = 300, 600, and 900 K, respectively. This implies that an optimized configuration of an n-Si cathode produces a significant electron emission cooling, especially at high temperatures.
Bandgap bowing in BGaN thin films

We report on the bandgap variation in thin films of BxGa1−xN grown on AlN/sapphire substrates using metal-organic vapor phase epitaxy. Optical transmission, photoluminescence, and x-ray diffraction were utilized to characterize the materials’ properties of the BxGa1−xN films. In contrast to the common expectation for the bandgap variation, which is based on the linear interpolation between the corresponding GaN and BN values, a significant bowing (C=9.2±0.5 eV) of the bandgap was observed. A decrease in the optical bandgap by 150 meV with respect to that of GaN was measured for the increase in the boron composition from 0% to 1.8%.
DC-link capacitors voltage balancing in multilevel four-leg diode-clamped converters

Multilevel four-leg four-wire converters are creating increasing interest nowadays in applications as active filters. They present several advantages compared to the three-leg converter topologies. Recently the control complexity has been reduced thanks to the use of new and powerful microprocessor systems, hence the balance of the DC-link voltage is the major drawback of this kind of topologies. In this paper, the first control strategy to carry out the balance of the DC-link voltage in the multilevel four-leg four-wire diode-clamped converter is presented. This strategy uses the known technique based on choosing the most suitable redundant vector in the space vector modulation algorithm in order to reduce the unbalance. It is important to notice that the proposed method is independent of the load and independent of the number of levels of the converter. Some simulation results show the obtained balance using the proposed technique.
A simplified method of calculating axial force for a permanent magnetic bearing

Abstract Axial magnetic force is an important parameter for permanent magnetic bearing (PMB). Current mathematical models for modelling the magnetic force are too complicated on the basis of some assumptions. This article presents a simplified calculating model of the axial force for axially magnetized PMB using the typical method of magnetic conductance. In this method, the magnetic-reluctance coefficient needed is investigated with the parameter identification method. It shows that changing the structure parameters and magnet materials only affects the magnetic-reluctance coefficient in a comparatively small range. A test device for measuring the axial magnetic force of PMB is developed to verify the effectiveness of the simplified calculating method. The results show that the proposed method can clearly express the relation between the axial magnetic force and structure parameters of PMB and requires less computation cost when compared with previous conventional methods. In conclusion, the proposed method is simple and effective in computing the axial force for PMB.
Exponential regression for censored data with outliers

We propose a penalized likelihood method to detect the possible outliers in the exponential regression model while it is utilized to fit the censored survival data. It features that the proposed method can simultaneously cope with outlier detection and estimation for the regression coefficient. We recast the outlier detection issue into a high-dimensional regularization regression and employ the coordinate descent algorithm to facilitate the computation. From both extensive simulation studies and an illustrative real example, it is shown that the proposed method works quite well in outlier detection as well as parameter estimation for the exponential regression model.
Ion and electron velocity distributions within flux transfer events

The detailed nature of the thermal and suprathermal ion and electron distributions within magnetic flux transfer events (FTEs) is examined. Examples of both magnetosheath FTEs and magnetospheric FTEs are discussed. The detailed distributions confirm that FTEs contain a mixture of magnetosheath and magnetospheric plasmas. To lowest order, the distributions are consistent with a simple superposition of the two interpenetrating populations, with no strong interactions between them. To first order, some interesting differences appear, especially in the electron distributions, suggesting that considerable pitch angle scattering and some electron energy diffusion are also occurring. These observations should provide a useful test of analytical and numerical studies of interpenetrating plasmas.
Equivalence of the Complementarity Problem to a System of Nonlinear Equations

It is shown that the complementarily problem of finding a z in $R^n $ satisfying $zF( z ) = 0$, $F( z )\geqq 0$, $z\geqq 0$, where $F:R^n \to R^n $, is completely equivalent to solving the system of n nonlinear equations in n unknowns \[ \theta \left( {\left| {F_i ( z ) - z_i } \right|} \right) - \theta \left( {F_i ( z )} \right) - \theta \left( {z_i } \right) = 0,\qquad i = 1, \cdots ,n, \] where $F_i ( z )$ and $z_i $ denote the components of $F( z )$ and z, respectively, and $\theta $ is any strictly increasing function from R into R such that $\theta ( 0 ) = 0$. If in addition, F is differentiable on $R^n $, $\theta $ is differentiable on R and $\theta '( 0 ) = 0$, then the above equations are globally differentiable, and at any solution z which satisfies the nondegeneracy condition $F( z ) + z > 0$, the system of equations has a nonsingular Jacobian if F has a nonsingular Jacobian with nonsingular principal minors.
Experimental Study of Reynolds Number Effects on Three-Dimensional Offset Jets

The effect of Reynolds number on three-dimensional offset jets was investigated in this study. An acoustic Doppler velocimeter simultaneously measured all three components of velocity, U, V and W, and turbulence intensity, urms, vrms, and wrms, and all three Reynolds shear stresses, uv, uw, and vw. Turbulent kinetic energy, k, was calculated with all three values of turbulence intensities. Flow measurements were performed at Reynolds numbers of 34,000, 53,000 and 86,000.Results of this experimental study indicate the wall-normal location of maximum mean velocity and jet spread to be independent of Reynolds number. The effects on maximum mean velocity decay are reduced with increasing Reynolds number. Profiles of mean velocities, U, V and W, turbulence intensities, urms, vrms, and wrms, and turbulent kinetic energy, k, show independence of Reynolds number. Reynolds shear stress uv was independent of Reynolds number while the magnitude of uw was reduced at higher Reynolds number.Copyright © 2014 by ASME
Analytical expression for thermal conductivity of superlattices

The increasing interest in manufacturing nanoscale low thermal conductivity devices has made important to obtain simple expressions that can predict their transport properties. This is more necessary for superlattice structures, where size effects and interface resistance effects can make the models very cumbersome. In this work we propose a simple analytical expression that can predict in-plane and cross-plane values of thermal conductivity of superlattices from an approximate analytical expression that joins a model expansion of the Boltzmann equation with a combination of the acoustic mismatch model and diffuse mismatch model for thermal boundary resistance. The obtained values are compared to experimental data from AlAs/GaAs, Si/Ge, and Si/Si0.7Ge0. 3 and a reasonable fit is obtained. Special attention is paid to the low thermal conductivity predicted in the Si/Ge large period range, which current microscale models fail to predict but which are approximately described in the present model.
Magnetising-field saturation and dynamic behaviour of induction machines. Part 1: Improved calculation method for induction-machine dynamics

It is shown that the classical induction-machine model does not correctly take into account the actual saturation effects of the magnetising field in situations different from sinusoidal supply/steady state conditions. An improved set of stationary equations is derived, making more accurate allowances for the magnetising-field saturation. Owing to saturation, both this modified nonlinear 2-axis model and the modified linearised model (small signal model) derived from it are not symmetrical with respect to the two axes. Indeed, for the calculation of transients or dynamics of a saturated machine, one has to consider two different magnetising inductances for the two axes. This point of view is also confirmed by experiments. The paper is in two parts. Part 1 contains the derivation of the corrected machine model and a concise report on an experimental confirmation of it. In Part 2, some practical applications of the proposed machine model concerning dynamic behaviour are discussed. Such applications constitute further proofs in support of the correctness of the proposed theory.
Li-Induced ferroelectricity and its structural phase transition in ZnO

Abstract Ferroelectricity in semiconducting ZnO by Li-substitution was studied. A ferroelectric phase transition occurs at 470 K in Zn0.91Li0. 09O. The revised Tc – x phase diagram was given. The Rietveld analysis of X-ray powder pattern showed a small displacement of Zn of 0.002 A along the polar c-axis in Zn0.91Li0. 09O.
Image Verification and Emotion Detection using Effective Modelling Techniques

—The feelings expressed on the face reflect the manner of thinking and provide useful insights of happenings inside the brain. Face Detection enables us to identify a face. Recognizing the facial expressions for different emotions is to familiarize the machine with human like capacity to perceive and identify human feelings, which involves classifying the given input images of the face into one of the seven classes which is achieved by building a multi class classifier. The proposed methodology is based on convolutional neural organizations and works on 48x48 pixel-based grayscale images. The proposed model is tested on various images and gives the best accuracy when compared with existing functionalities. It detects faces in images, recognizes them and identifies emotions and shows improved performance because of data augmentation. The model is experimented with varying depths and pooling layers. The best results are obtained sequential model of six layers of Convolutional Neural Network and softmax activation function applied to last layer. The approach works for real time data taken from videos or photos.
Approaching quantitative Zernike phase contrast in full-field transmission hard X-ray microscopy: Origin and reduction of artifacts

Zernike phase contrast in hard X-ray transmission microscopy provides in-line observation of phase enhanced imaging of weak-absorbing objects. However, the inherent artifacts are the major hurdle to acquire quantitative structural analysis, and may even present misleading information. We explore the origin of these artifacts by frequency analysis in Fourier domain. Subsequently, a simple and flexible method for artifacts reduction well-suited for full-field transmission hard X-ray microscopy based on combination of spectra is proposed. It is demonstrated to yield quantitative local phase maps, with the characteristic artifact patterns reduced.