Miracle-dz/UniFAR-FTUs huggingface dataset:
Ionospheric single‐station TEC short‐term forecast using RBF neural network

In this article a radial basis function (RBF) neural network improved by Gaussian mixture model is developed to be used for forecasting ionospheric 30 min total electron content (TEC) data given the merits of its nonlinear modeling capacity. In order to understand more about the response of developed network model with respect to stations situated at different latitude, estimated TEC overhead of GPS ground stations BJFS (39.61°N, 115.89°E), WUHN (30.53°N, 114.36°E), and KUNM (25.03°N, 102.80°E) for 6 months in 2011 are used for training data set, validating data and test data set of RBF network model. The performance of the trained model is evaluated at a set of criteria. Our results show that the predicted TEC is in good agreement with observations with mean relative error of about 9% and root‐mean‐square error of less than 5 total electron content unit, 1 TECU = 1016 el m−2. Our comparison further indicates that RBF network offers a powerful and reliable tool for the design of ionospheric TEC forecast.
Using a reduced set of Fourier modes in terms of a FFT-based microstructure simulation

Given a heterogeneous material, the mechanical behavior of its microstructure can be investigated by an algorithm that uses the Fourier representation of the Lippmann-Schwinger equation. Incorporating a model order reduction technique based on calculations with a reduced set of Fourier modes, the computational cost of this algorithm can be decreased. It was shown that the accuracy of this model order reduction technique strongly depends on the choice of Fourier modes by considering a geometrically adapted rather than a ﬁxed sampling pattern to deﬁne the reduced set of Fourier modes. Since it is diﬃcult to deﬁne a geometrically adapted sampling pattern for complex microstructures, additionally a strain-based sampling pattern was introduced. The accuracy and adaptability of this strain-based reduced set of Fourier modes is shown by incorporating a polycrystalline microstructure.
Exploitation of the entropy principle: Proof of Liu theorem if the gradients of the governing equations are considered as constraints

The exploitation of the entropy principle in thermodynamics with Lagrange multipliers (the so called Liu procedure) is based on the celebrated Liu theorem. In some recent papers, where either rigid heat conductors or Korteweg fluids have been considered, the Liu procedure has been generalized by using the gradients of the governing equations as additional constraints. Here, a rigorous proof of the validity of the extended procedure to arbitrary first-order nonlocal continua is provided, thus explicitly generalizing the Liu theorem. As an application, heat conducting first-order Korteweg-type fluids with a scalar internal variable are analyzed. The thermodynamic restrictions are determined by the extended Liu procedure. Moreover, a comparison with the thermodynamic analysis obtained by the application of an extended Coleman–Noll procedure is performed.
Angular Distribution of n-p Scattering at 14.1 MeV

The angular distribution for the scattering of neutrons by protons was obtained at 14.1 MeV by observing the recoil protons by the use of a counter-telescope consisting of a polyethylene target, two proportional counters and a CsI scintillator. The data obtained at scattering angles of 165°, 146°, 118° and 89° in C.M. -system were given with statistical errors of about 1%. The ratio of the cross sections at 180° and 90° in the center-of-mass system was found to be 1.080±0.016 from a least square fit to the form A + B cos 2 θ. Therefore it may be concluded that anisotropy of the angular distribution is confirmed quite clearly. The absolute values of differential cross sections at various angles were normalized using the total cross section 689±5 mb measured by transmission. The values are in good agreement with the results predicted from the nuclear potentials with “one-pion-exchange-tail” proposed by members of the Nuclear Force Group in Japan.
Physico-Chemical, Mechanical and Morphological Characterization of Furcraea Selloa K.Koch Plant Leaf Fibers-An Exploratory Investigation

ABSTRACT The interest in developing bio-based composite materials had grown up with the context of maintaining ecological integrity by introducing new eco-friendly materials. The present study investigated the suitability of a novel Furcraea selloa K. Koch leaf fiber (FSLF) for composite reinforcement instead of existing synthetic harmful fiber materials. The identification for exploration of novel natural fibers with significant properties is a great challenge for researchers, due to their accessibility in polymer composites eco-friendliness and sustainability. Indeed, physicochemical, thermal, mechanical, and morphological features were established through this study, low density (810 kg/m3), high crystallinity (56.7%), high thermal stability (350°C), good tensile strength (650 ± 23 MPa) were the notable features of FSLF that facilitate its further use for composite reinforcement. Moreover, good surface roughness with fewer impurities and low microfibril angle also prove its sustainability in composite reinforcement. This study suggests that the potential properties of FSLF would be a suitable alternative to commercially important synthetic fiber, in the highest seeking-fibers as reinforcement.
ANALISIS PENGARUH EXPOSURE TERHADAP PERFORMA ALGORITMA SIFT UNTUK IMAGE MATCHING PADA UNDERWATER IMAGE

"Image matching menjadi peranan penting dalam proses 3D rekonstruksi yaitu untuk menemukan keypoint dalam sebuah gambar. Algoritma SIFT dibutuhkan untuk mencari jumlah keypoint pada gambar. Semakin banyak keypoint yang didapatkan, maka gambar akan semakin halus. Metode image enhancement yang digunakan untuk meningkatkan kualitas suatu citra digital sehingga gambar menjadi bertekstur dan keypoint yang terdapat di dalam gambar akan menjadi mudah untuk diidentifikasi. Pada penelitian ini digunakan teknik image enhancement Exposure guna mengetahui seberapa pengaruhnya terhadap Algoritma SIFT dalam menemukan matching point. Ada 2 Metode yang digunakan dalam penelitian ini. Penelitian A gambar yang diuji tanpa melalui enhancement dan penelitian B gambar yang diuji dengan enhancement dengan menambahkan nilai tertentu pada Exposure. Dan untuk mengetahui seberapa pengaruh enhancement terhadap jumlah matching point yang ditemukan dilakukan pengujian secara statistik menggunakan Paired T Test yang akan membandingkan jumlah matching point pada penelitian A dan B. Dari penelitian yang dilakukan didapatkan hasil statistik yang menunjukkan bahwa pada Exposure (+1) menyatakan H0 ditolak dan H1 diterima. Dengan demikian dinyatakan bahwa yang mempengaruhi perubahan jumlah matching point secara signifikan adalah Exposure (+1). "
DC-link Harmonic Current Mitigation Strategies for Improvement of DC-link Capacitor Lifetime in a Multidrive System

It is now a common practice to connect multiple drives to a common AC supply system at the point of common coupling. In this kind of conventional parallel-connected system, each inverter shares the common AC-link. This means that the total number of rectifiers for each of these inverters needed in the whole system increases with the increasing number of converters connected in parallel [J1]. This causes, an increase in the overall size and reducing the reliability of the overall multidrive system. To overcome this challenge, in this Ph.D. research, a multidrive system having a common DC-link (using a centralized rectifier), is utilized [J2]. Notably, the centralized rectifier is sized according to the total load power demand and is connected to the AC-supply. In such cases, the common DC-bus provides power to the drive modules. Each drive module has its individual inverter, which then converts the DC-power to AC-power and then transfers it to the associated motor. Moreover, in case if the centralized rectifier fails, the common DC-bus can be powered by battery or generation from other renewable sources that can provide sufficient power to continue the load system at the same operating conditions (in the meantime could be possible to correct the rectifier system). However, in such parallel systems, the DC-link current harmonics may increase, causing unstable operation, and possible failure of the fragile components such as DClink capacitors and consequently multiple system downtime and extra maintenance requirement [J1]. Given this background, it can be inferred that in a DC-bus-connected multidrive system, there is a need for research in the analysis of DC-link harmonics mitigation methods, and the design of DC-link capacitors to reduce the overall effect of DC-harmonics and increase the lifespan of DC-link capacitor. The main focus of this Ph.D. project is to mitigate the DC-link harmonics in a multidrive based drivetrain system. Then to also improve the lifetime of DC-link capacitor. First, an analytical model is developed to find the DC-link capacitor-current [J1,J2]. Next, using developed DC-current harmonics mitigation techniques, the DC-link current harmonics will be reduced. This will significantly reduce the DC-link capacitor current,
Implementation and application of advanced density functionals

Density functional theory (DFT) is a method of effectively solving the many-electron Schrodinger equation, enabling the properties of condensed matter systems to be calculated from first principles. With the commonly used local density approximation (LDA), and generalised gradient approximations (GGAs), to the exchange correlation functional, it is currently possible to perform calculations on systems containing several hundred atoms. The accuracy of such calculations depends on the system under study and on which particular properties one wishes to calculate. The use of more advanced functionals has the potential to improve accuracy, at the expense of greater computational demand. In this work we use the LDA to calculate certain properties of GaN, such as geometry, band structure, and surface properties, including the reconstruction of GaN surfaces under the presence of hydrogen. We then describe our computational implementation of advanced density functionals, including screened exchange (sX-LDA), Hartree-Fock (HF), and exact exchange (EXX), within an efficient, fully parallel, plane wave code. The implementation of sX-LDA and HF is used to calculate band structure properties of Si, GaN, and other simple semiconductors, and it is found that sX-LDA can improve results significantly beyond the LDA. We also derive and implement the theory that allows one to calculate directly the contribution to the stress tensor from exchange and correlation when using these functionals, and demonstrate this with some simple test cases. Finally, we introduce some new theoretical ideas that may pave the way for yet more accurate density functionals in the future.
Efficient parameter estimation in a macroscopic traffic flow model by discrete mollification

Our concern is the numerical identification of traffic flow parameters in a macroscopic one-dimensional model whose governing equation is strongly degenerate parabolic. The unknown parameters determine the flux and the diffusion terms. The parameters are estimated by repeatedly solving the corresponding direct problem under variation of the parameter values, starting from an initial guess, with the aim of minimizing the distance between a time-dependent observation and the corresponding numerical solution. The direct problem is solved by a modification of a well-known monotone finite difference scheme obtained by discretizing the nonlinear diffusive term by a formula that involves a discrete mollification operator. The mollified scheme occupies a larger stencil but converges under a less restrictive Courant-Friedrichs-Lewy (CFL) condition, which allows one to employ a larger time step. The ability of the proposed procedure for the identification of traffic flow parameters is illustrated by a numerical experiment.
Turbulent structure in Earth's fluid core inferred from time series of geomagnetic dipole moment

The physical grounds are discussed for assessing turbulent structures hidden inside the Earth's liquid core by using a time series of the geomagnetic dipole moment obtained from historical and paleomagnetic data. We propose the idea that the time‐averaged wavenumber spectra of electric current density at the core‐mantle boundary (CMB) and also velocity near the CMB have relation to the frequency spectrum of the dipole moment. We performed computer simulations of a magnetohydrodynamic spherical dynamo to verify this idea. We show that the frequency spectrum of the dipole moment in the simulation is similar to that inferred by paleomagnetic observations. The simulation results indicate that the underlying kinetic energy spectrum is proportional to m−5/3 in a high wavenumber range, where m is the azimuthal wavenumber. We speculate that a similar turbulent energy spectrum may exist in the Earth's core with a peak near m = 5.
Coupling of spherical‐surfaced LED and spherical‐ended fiber

The coupling of a spherical‐surfaced LED and a spherical‐ended fiber is analyzed using a model in which a light source and an aperture stop are on the anterior and posterior focal planes, respectively. The launching efficiency is defined as the ratio of the power launched into a fiber to the optical power generated in the LED. The efficiencies for step‐ and graded‐index fibers are derived. Maximum efficiency can be obtained when d0=dc, where d0 is the emitting diameter and dc is the critical diameter defined by the focal length and the critical angle of the fiber. When d0? dc, the ratio χ of improvement in the efficiency for a spherical‐surfaced LED to that for a flat LED is approximately proportional to the square of the lateral magnification β, which is the image diameter divided by d0. χ? β2 is confirmed experimentally with couplings using spherical‐surfaced and flat LED’s.
Magnetospheric Accretion Models for the Hydrogen Emission Lines of T Tauri Stars

Using a statistical equilibrium radiative transfer treatment, we examine the behavior of hydrogen emission lines arising from the magnetospheric infall zones of classical T Tauri stars. Having calculated self-consistent line profiles of the Balmer lines, Paβ and Brγ, we explore parameter space, examining the effects of the magnetospheric gas temperature and size on the line fluxes. We compare model and observed line fluxes for the Balmer lines and find a good match using a relatively small range of parameters. We are also able to match the observed Brγ line profile of the embedded object WL 16, which supports the use of the infrared lines in studying magnetospheric infall even in the earliest stages of star formation. Finally, we discuss constraints on the physical parameters and the possibility of using the emission lines as accretion rate indicators.
An effective hybrid PSO-based algorithm for planning UMTS terrestrial access networks

In this article, an effective hybrid algorithm based on Particle Swarm Optimization (PSO) is proposed for planning UMTS (Universal Mobile Telecommunication System) access networks. First, a new encoding scheme based on heuristics is developed, which converts the continuous position values of particles in PSO to multi-constrained and capacitated subnetwork trees with previously dedicated root nodes. Secondly, a local search strategy based on simulated annealing is incorporated in order to prevent premature convergence and concentrate computing effort on promising solutions. The proposed local search uses multi-neighbourhood structure guided by an adaptive meta-Lamarckian learning strategy. In particular, an iteration of the algorithm consists of a standard PSO iteration and a trial of simulated annealing applied to the best solution found so far, where the adaptive meta-Lamarckian learning strategy is employed to decide which neighbourhood is to be used. Simulation results on several networks with random topologies are used to illustrate the effectiveness of the proposed algorithm.
Homogeneous Feedback Control of Nonlinear Systems Based on Control Lyapunov Functions

This paper is concerned with homogeneous feedback control for a class of nonlinear systems. By using control Lyapunov functions, homogeneous controllers of homogeneous and nonhomogeneous systems are respectively constructed, under which the stabilization of the systems under considerations are guaranteed. Then, the design method is extended for uncertain systems by means of homogeneous domination theory. Compared with the traditional design method based on robust control Lyapunov functions, the present design reduces the difficulty of constructing controllers. Finally, several simulation examples are given to illustrate the correctness of the design.
A Novel Functional Electrical Stimulation-Induced Cycling Controller Using Reinforcement Learning to Optimize Online Muscle Activation Pattern

This study introduces a novel controller based on a Reinforcement Learning (RL) algorithm for real-time adaptation of the stimulation pattern during FES-cycling. Core to our approach is the introduction of an RL agent that interacts with the cycling environment and learns through trial and error how to modulate the electrical charge applied to the stimulated muscle groups according to a predefined policy and while tracking a reference cadence. Instead of a static stimulation pattern to be modified by a control law, we hypothesized that a non-stationary baseline set of parameters would better adjust the amount of injected electrical charge to the time-varying characteristics of the musculature. Overground FES-assisted cycling sessions were performed by a subject with spinal cord injury (SCI AIS-A, T8). For tracking a predefined pedaling cadence, two closed-loop control laws were simultaneously used to modulate the pulse intensity of the stimulation channels responsible for evoking the muscle contractions. First, a Proportional-Integral (PI) controller was used to control the current amplitude of the stimulation channels over an initial parameter setting with predefined pulse amplitude, width and fixed frequency parameters. In parallel, an RL algorithm with a decayed-epsilon-greedy strategy was implemented to randomly explore nine different variations of pulse amplitude and width parameters over the same stimulation setting, aiming to adjust the injected electrical charge according to a predefined policy. The performance of this global control strategy was evaluated in two different RL settings and explored in two different cycling scenarios. The participant was able to pedal overground for distances over 3.5 km, and the results evidenced the RL agent learned to modify the stimulation pattern according to the predefined policy and was simultaneously able to track a predefined pedaling cadence. Despite the simplicity of our approach and the existence of more sophisticated RL algorithms, our method can be used to reduce the time needed to define stimulation patterns. Our results suggest interesting research possibilities to be explored in the future to improve cycling performance since more efficient stimulation cost dynamics can be explored and implemented for the agent to learn.
An Energy-Based Approach to Extract the Dynamic Instability Parameters of Dielectric Elastomer Actuators

An energy-based approach is presented to extract the thresholds on the transient dynamic response of step voltage driven dielectric elastomer actuators (DEAs). The proposed approach relies on establishing the energy balance at the point of maximum stretch in an oscillation cycle followed by the application of an instability condition to extract the dynamic instability parameters. Explicit expressions are developed for the critical values of maximum stretch and the corresponding nominal electric field, thus circumventing the need to perform iterative time-integrations of the equation of motion. The underlying principles of the approach are enunciated for the neo-Hookean material model and further extended to analyze relatively complex multiparameter hyperelastic models (Mooney–Rivlin and Ogden) that are employed prevalently for investigating the behavior of DEAs. The dynamic instability parameters predicted using the energy method are validated by examining the time-history response of the actuator in the vicinity of the dynamic instability. The development of dynamic instability parameters is complemented by energy-based extraction of static instability parameters to facilitate a quick comparison between the two. It is inferred quantitatively that the nominal electric field sufficient to cause the dynamic instability and the corresponding thickness stretch is lower than those corresponding to the static instability. A set of representative case studies for multiparameter material models is presented at the end, which can be used as an input for further experimental corroboration. The results of the present investigation can find their potential use in the design of DEAs subjected to transient loading.
Characterization of an argon plasma jet by the imagery method

The imagery method is used to detect the radiation flux emitted by an optically thin argon plasma jet at atmospheric pressure and high temperatures, after assuming conditions of local thermodynamic equilibrium in the continuum field. Quantitative agreement is observed by comparing the results of the imagery method with those from a multichannel optical detector. Abel inversion is programmed to convert the intensity measured by both methods to the volumetric emissivity of the argon plasma jet. The results presented in the form of intensity and volumetric emissivity show that the imagery method remains a good way of characterizing an argon plasma jet.
Maximum Torque and Momentum Envelopes for Reaction Wheel Arrays

Spacecraft reaction-wheel maneuvers are limited by the maximum torque and/or angular momentum that the wheels can provide. The torque or momentum envelope for an n-wheel configuration can be obtained by projecting the n-dimensional hypercube, representing the domain boundary of individual wheel torques or momenta, into three-dimensional space via the 3 x n matrix of wheel axes. This paper elucidates the properties of the projected hypercube and presents algorithms for determining this maximal torque or momentum envelope for general wheel configurations and for distributing a prescribed torque or momentum among the n wheels. We show that these algorithms provide 22, 27, and 33% more capability than the more conventional pseudoinverse algorithm for configurations of four, five, and six wheels, respectively. Analysis of a representative slew using six wheels shows that these algorithms can provide either a 25% reduction in maximum wheel momentum or a 30% reduction in slew time when compared with the pseudoinverse algorithm.