Miracle-dz/UniFAR-FTUs huggingface dataset:
Lightning Sferics: Analysis of the Instantaneous Phase and Frequency Inferred From Complex Waveforms

Analysis of very low frequency lightning waveforms, or radio sferics, can contribute to research into lower ionosphere perturbations and the corresponding atmospheric chemistry. Lightning waveforms can also be characterized on the basis of their propagation distance from receivers in order to study radio wave propagation. A bank of average waveforms, that is, the waveform bank, <1,000 km with a spatial resolution of 10 km has been produced, based on the lightning waveforms recorded in Europe on 8 August 2014. These average lightning waveforms at different distances exhibit a sequence of consecutive maxima resulting from ionospheric reflections, named sky waves. The spectral waveform bank shows a sequence of consecutive modal maxima at different frequencies depending on distance. The Hilbert transform is applied to produce complex lightning waveforms, which provide additional information to the original real waveforms alone, that is, the instantaneous phase and frequency. The time differences calculated from the instantaneous phases of complex lightning waveforms give the minimum arrival time difference error when compared to other analyzed signal processing methods. The derivative of the instantaneous phase, that is, the instantaneous frequency, represents the amplitude‐weighted average of frequency components at maximum amplitude according to theory and numerical simulation. In real experiments, the instantaneous frequency can be understood as the median value of the real frequency distribution calculated at maximum amplitude. It is found that the instantaneous frequencies at maximum amplitudes are distance dependent. This finding might enable the development of a novel method to determine lightning distances in the future.
Unsteady Performance of Finite-Span Pitching Propulsors in Side-by-Side Arrangements

Experimental measurements are presented on the performance of two finite-span pitching wings with an aspect ratio of AR = 2 interacting in a side-by-side arrangement. Experiments are conducted for various synchronies and cross-stream spacings. The thrust, power and lift coefficients as well as the efficiency are reported for both the individual wings and the collective. The collective thrust and power consumption are found to increasewhile the efficiency decreases during out-of-phase oscillations (φ = π) for close spacings of Y∗ ≤ 0.75. Similarly, the collective thrust and power consumption are found to decrease while the efficiency increases during inphase oscillations (φ = 0) for spacings of Y∗ ≤ 1.125. In contrast to this trade-off between improved thrust or efficiency, there are conditions such as at Y∗ = 1 and φ ≈ π/2 and 3π/2 that give a 20% increase in collective thrust and 17% increase in collective efficiency at the same time. It is further demonstrated that the direction of the collective lift shows a dependence on both the synchrony and the spacing.
Searching for new TeV blazars in the 3rd Fermi-LAT catalogue of hard gamma-ray sources

The 3rd Fermi catalogue of Hard Fermi-LAT Sources (3FHL), which detected 1556 sources above 10 GeV, provides an important resource for finding new candidate TeV sources for follow-up observations with the H.E. S.S. telescopes. To search for potential TeV emitting extragalactic sources, we observed a sample of five 3FHL sources classified as Blazars of unknown type (BCU) and two 3FHL sources without associations at other wavelengths with the SAAO 1.9-m telescope. The observations were performed during February 2017, with the SpUpNIC spectrograph on the 1.9-m telescope. Possible counterparts for the unassociated sources were determined by cross-matching objects using archival multi-wavelength data from Radio, Infrared and X-ray catalogues. Classifications were obtained for all the observed BCUs and redshifts were determined for two of them. Redshift measurements were obtained for the optical candidates of both the unassociated sources observed. Further analysis is necessary to confirm their association to the 3FHL γ-ray sources.
Aggregation of time series predictors, optimality in a locally stationary context

This thesis regroups our results on dependent time series prediction. The work is divided into three main chapters where we tackle different problems. The first one is the aggregation of predictors of Causal Bernoulli Shifts using a Bayesian approach. The second one is the aggregation of predictors of what we define as sub-linear processes. Locally stationary time varying autoregressive processes receive a particular attention; we investigate an adaptive prediction scheme for them. In the last main chapter we study the linear regression problem for a general class of locally stationary processes.
Nearly-Linear Time Packing and Covering LP Solver with Faster Convergence Rate Than $O(1/\varepsilon^2)$

Packing and covering linear programs (LP) are an important class of problems that bridges computer science, operation research, and optimization. Efficient algorithms for solving such LPs have received significant attention in the past 20 years [LN93, PST95, BBR97, You01, Nem04, BI04, BBR04, Nes05, AK08, AHK12, KY13, You14, AO15]. Unfortunately, all known nearly-linear time algorithms for producing $(1+\varepsilon)$-approximate solutions to packing and covering LPs have a running time dependence that is at least proportional to $\varepsilon^{-2}$. This is also known as an $O(1/\sqrt{T})$ convergence rate and is particularly poor in many applications. In this paper, we leverage insights from optimization theory to break this longstanding barrier. Our algorithms solve the packing LP in time $\tilde{O}(N \varepsilon^{-1})$ and the covering LP in time $\tilde{O}(N \varepsilon^{-1.5})$. At high level, they can be described as linear couplings of several first-order descent steps. This is the first application of our linear coupling technique (see [AO14]) to problems that are not amenable to blackbox applications known iterative algorithms in convex optimization. Our work also introduces a sequence of new techniques, including the stochastic and the non-symmetric execution of gradient truncation operations, which may be of independent interest.
Fractal Model for Acoustic Absorbing of Porous Fibrous Metal Materials

To investigate the changing rules between sound absorbing performance and geometrical parameters of porous fibrous metal materials (PFMMs), this paper presents a fractal acoustic model by incorporating the static flow resistivity based on Biot-Allard model. Static flow resistivity is essential for an accurate assessment of the acoustic performance of the PFMM. However, it is quite difficult to evaluate the static flow resistivity from the microstructure of the PFMM because of a large number of disordered pores. In order to overcome this difficulty, we firstly established a static flow resistivity formula for the PFMM based on fractal theory. Secondly, a fractal acoustic model was derived on the basis of the static flow resistivity formula. The sound absorption coefficients calculated by the presented acoustic model were validated by the values of Biot-Allard model and experimental data. Finally, the variation of the surface acoustic impedance, the complex wave number, and the sound absorption coefficient with the fractal dimensions were discussed. The research results can reveal the relationship between sound absorption and geometrical parameters and provide a basis for improving the sound absorption capability of the PFMMs.
Global finite‐time output stabilization of nonlinear systems with unknown measurement sensitivity

This paper focuses on the output stabilization problem for a class of strict‐feedback systems with unknown nonlinear dynamics and unknown measurement sensitivity. The imprecise sensor measurements render the existing robust control approaches such as neuro or fuzzy control infeasible. A solution is provided in this paper by a feat of the concept of tuning functions and barrier Lyapunov functions (BLFs). Utilizing the modification capability of tuning functions, global stability is preserved. Exploiting the potential robustness of BLFs, the effect of unmodeled dynamics is counteracted under sensitivity errors. The combination of tuning functions with BLFs further leads to a distinct property that the real system output converges to an adjustable region in finite time. Compared with the existing results, the need for prior knowledge of system nonlinearities and measurement sensitivity is removed in this paper. Finally, simulation results illustrate the established theoretical findings.
An Analysis of the Prevalence of Heat Waves in the United States between 1948 and 2015

Unusually hot weather is a major concern to public health as well as other systems (e.g., ecological, economical, energy). This study utilized spatially continuous and homogenized observational surface climate data to examine changes in the regularity of heat waves in the continental United States. This included the examination of heat waves according only to daytime temperatures, nighttime temperatures, and both daytime and nighttime temperatures. Results confirmed a strong increase in the prevalence of heat waves between the mid-1970s and the dataset end (2015), and that increase was preceded by a mild decrease since the dataset beginning (1948). Results were unclear whether the prevalence of nighttime or simultaneous daytime–nighttime heat waves increased the most, but it was clear that increases were largest in the summer. The largest gains occurred in the West and Southwest, and a “warming hole” was most conspicuous in the northern Great plains. The changes in heat wave prevalence were similar to changes in the mean temperatures, and more so in the daytime heat waves. Daytime and nighttime heat waves coincided with one another more frequently in recent years than they did in the 1970s. Some parts of the United States (West Coast) were more likely than other parts to experience daytime and nighttime heat waves simultaneously. While linear trends were not sensitive to the climate dataset, trend estimation method, or heat wave definition, they were mildly sensitive to the start and end dates and extremely sensitive to the climate base period method (fixed in time or directly preceding any given heat wave).
Minimization of total energy consumption in an m-machine flow shop with an exponential time-dependent learning effect

This study investigates an energy-aware ﬂ ow shop scheduling problem with a time-dependent learning effect. The relationship between the traditional and the proposed scheduling problem is shown and objective is to determine a job sequence in which the total energy consumption is minimized. To provide an ef ﬁ cient solution framework, composite lower bounds are proposed to be used in a solution approach with the name of Bounds-based Nested Partition (BBNP). A worst-case analysis on shortest process time heuristic is conducted for theoretical measurement. Computational experiments are performed on randomly generated test instances to evaluate the proposed algorithms. Results show that BBNP has better performance than conventional heuristics and provides considerable computational advantage.
LINE-DEPTH RATIOS IN H-BAND SPECTRA TO DETERMINE EFFECTIVE TEMPERATURES OF G- AND K-TYPE GIANTS AND SUPERGIANTS

The stellar effective temperature is the fundamental parameter of stellar atmospheres. It characterizes the spectra and plays an essential role in chemical abundance analysis. Previous optical studies have shown that line-depth ratios (LDRs) are good indicators of the effective temperature. Essentially, the ratios of absorption lines with different excitation potentials can be used as temperature scales. The most important advantage of LDRs is their robustness against interstellar reddening and extinction. Furthermore, the scales are constructed and calibrated empirically by observables. Although this method is well-established for optical spectra, we require infrared high-resolution spectroscopy to access the most obscured stars in the Galactic disk and thereby understand the Milky Way’s structure and evolution in the innermost region. This study newly derives the temperature scales from the LDRs in infrared spectra. We explored LDRs in the high-resolution H-band spectra (1.4–1.8 μm) of well-known stars in the solar neighborhood obtained with Subaru/infrared camera and spectrograph. We found nine pairs of absorption lines whose LDRs allow us to determine the temperatures of G- and K-type giants/supergiants to an accuracy of ∼60 K. Checking the dependency of our scales on stellar parameters, we found that our developed temperature scales may slightly bias the estimates for low-metal stars, [Fe/H] < − 0.3 ? > dex.
The role of tidal stirring in controlling the seasonal heat cycle in shelf seas

Description d'un modele de rechauffement local qui permet a la t de surface marine de controler le flux de chaleur a travers la surface marine. La solution indique que le niveau de brassage du a la maree exerce un effet important sur le cycle annuel de chaleur. L'amplitude de ce cycle, dans une eau bien melangee, peut s'elever jusqu'a deux fois celle dans une eau stratifiee de meme profondeur
A UAV–RTK Lidar System for Wave and Tide Measurements in Coastal Zones

A lightweight and low-cost unmanned aerial vehicle (UAV) system for coastal wave and tide measurements is developed. This system is based on an assembly of a multirotor UAV, a robotic lidar, an altitude and heading reference system (AHRS), and a real-time kinematic (RTK) Global Navigation Satellite System (GNSS). A great advantage of the system is that it can be operated at low altitude in a few meters; the accuracy and spatial resolution can therefore be increased. When the system was moved up and down in 2–12 m, the root-mean-square error (RMSE) was approximately 5 cm compared to the ground truth value measured by a manual RTK GNSS. The system was operated in a hover mode to measure the tide and waves in the field. The results of using the UAV–RTK lidar system were consistent with those of in situ measurements using a pressure sensor. The root-mean-square errors between the two techniques for measurements of tidal elevation, significant wave height, and wave period were 4.9 cm, 4.8 cm, and 0.028 s, respectively. This finding suggests the system could be applied to measure instantaneous sea surface displacement. The system provides the potential for using a low-cost, extremely portable, and efficient tool for monitoring wave properties, topographic changes, and water-level gradients in coastal zones.
Extraction of quark distributions on transverse spin of the nucleon at the HERMES experiment

This thesis describes extraction of the Collins and Sivers asymmetries for charged and neutral pions via measurement of the single-spin asymmetries with a transversely polarized hydrogen target at HERMES. Especially, this thesis stresses the Sivers function extracted from the observed Sivers asymmetries. The Sivers function is a parton distribution which depends on the intrinsic transverse momentum of the parton. This has never been measured before. The Sivers function has a nature of naive time reversal odd. Also the function provides information of the quark orbital angular momentum. EMC experiment reputed in 1988 that the quark spin contribution to the nucleon spin is small. In a series of experiments following EMC, the quark spin contribution to the nucleon spin measured to be 20 30%. Quark angular momentum obtained attention as it is one of the candidates to fill the missing fraction of the nucleon spin. It had been thought that all transverse spin effects does not influence interaction of high energy particles, because the transverse spin is no longer eigenstate of transverse spin operator when it is boosted to infinite momentum frame. However from 70’s to 90’s, several experiments have been carried out to measure the “single-spin asymmetries AN” (left-right asymmetry) with inclusive pion measurement using transversely polarized (unpolarized) proton beam and unpolarized (polarized) proton target. Large asymmetries have been observed depending on transverse momentum of final state hadron, whereas the theoretical expectation based on the naive parton model lead to AN = 0. To describe the single-spin asymmetries, two theoretical models are available at the moment, Collins [1] and Sivers [2] effects. Those were motivated by completely different mechanisms to generate the single-spin asymmetry. The Collins mechanism generates the single-spin asymmetries in hadronization processes, so this mechanism requires spin dependent fragmentation function, so-called Collins function. In contrast, Sivers effect originates from quark intrinsic transverse momentum. This mechanism is described with a parton distribution function, so-called Sivers function. Especially the Sivers function provides information on the quark orbital motion. If the Sivers function is found to be non-zero, it suggests non-zero quark orbital angular momentum which can contribute to spin structure of the nucleon. It was not possible to separate these two mechanisms in inclusive measurement of pion production in hadron-hadron collisions. Up to now there are no experimental information on Collins and Sivers function, separately.
Forecasting Using Random Subspace Methods

Random subspace methods are a new approach to obtain accurate forecasts in high-dimensional regression settings. Forecasts are constructed by averaging over forecasts from many submodels generated by random selection or random Gaussian weighting of predictors. This paper derives upper bounds on the asymptotic mean squared forecast error of these strategies, which show that the methods are particularly suitable for macroeconomic forecasting. An empirical application to the FRED-MD data confirms the theoretical findings, and shows random subspace methods to outperform competing methods on key macroeconomic indicators.
Infinite versions of minesweeper are Turing complete

The starting point for this paper is my article [5] showing that the wellknown Minesweeper game is NP-complete. The proof was by making suitable minesweeper configurations simulate digital computers, with logic gates such as and and not gates. This is reminiscent of John Conway’s game of life [2] which was proved to be Turing complete by similar means [1]. (For background information on Turing machines and computability please see just about any text book on these. I found the account by Wang [7] particularly enjoyable and can recommend it as it presents just about the right about of material needed here in a straightforward and not too technical manner.) It is reasonable to ask whether or not there is an version of Minesweeper analogous to Life that is also Turing complete. In this paper I show that there is. Before I start, we should consider what this question asks for. Games like Life and Minesweeper are played on a grid, with each space on the grid labelled with at most one of only finitely many symbols. Such games played on a finite grid will typically be computable—by laboriously checking all possible combinations—so we are interested in versions of Minesweeper played on an infinite grid. Both Minesweeper and Life are normally played on square grids in the plane with an adjacency relation between two neighbouring squares that
On the existence of solutions for quadratic integral equations in Orlicz spaces

Abstract We study quadratic integral equations in Orlicz spaces on the interval [a, b]. We relate growth conditions with appropriate spaces of solutions and then we investigate different cases. Our approach allows to consider discontinuous solutions as well as to unify the results for both quadratic and classical integral equations. Many different types of growth conditions for investigated functions are considered.
Automatic Generation of Water Masks from RapidEye Images

Water is a very important natural resource and it supports all life forms on earth. It is used by humans in various ways including drinking, agriculture and for scientific research. The aim of this research was to develop a routine to automatically extract water masks from RapidEye images, which could be used for further investigation such as water quality monitoring and change detection. A Python-based algorithm was therefore developed for this particular purpose. The developed routine combines three spectral indices namely Simple Ratios (SRs), Normalized Green Index (NGI) and Normalized Difference Water Index (NDWI). The two SRs are calculated between the NIR and green band, and between the NIR and red band. The NGI is calculated by rationing the green band to the sum of all bands in each image. The NDWI is calculated by differencing the green to the NIR and dividing by the sum of the green and NIR bands. The routine generates five intermediate water masks, which are spatially intersected to create a single intermediate water mask. In order to remove very small waterbodies and any remaining gaps in the intermediate water mask, morphological opening and closing were performed to generate the final water mask. This proposed algorithm was used to extract water masks from some RapidEye images. It yielded an Overall Accuracy of 95% and a mean Kappa Statistic of 0.889 using the confusion matrix approach.
On the Role of Transient Eddies in the Tropical Troposphere

We studied the contributions of eddies with various time scale to the covariances of the zonal wind component, temperature and geopotential height with the meridional wind component in the tropical troposphere by the spectral analysis of time series data of Pacific stations for April-July 1962. In the equatorial region disturbances with periods near 4 days play an important role in the covariances. On the other hand, disturbances with period near 6 days and those with periods longer than 10 days mostly contribute to the covariances in sub-tropical latitudes (near 20*N). Average horizontal transports of zonal momentum, sensible heat and potential energy due to transient eddies and partial contributions of disturbances with periods near 4 days to the transports are examined as functions of latitude and altitude. Strong energy fluxes due to disturbances with periods longer than 6 days enter into the tropics from higher latitudes. This results agreeswith that obtained theoretically by Mak (1969). Equatorward heat fluxes exist in the lower and the middle troposphere. Large poleward heat fluxes are observed in the upper troposphere. In higher latitudes, contributions of disturbances with periods near 4 days to the horizontal transports are small, but in the equatorial region these become large. A partial estimate of the energy transformation process of eddies contained between the equator and 15*N. Large energy fluxes (pressure work) from higher latitudes converge in the equatorial region. The eddy kinetic energy is transformed to the zonal kinetic energy and the eddy available potential energy is transformed to the zonal potential energy. The convergence of energy flux from higher latitudes is one order of magnitude larger than both energy conversions from eddy to zonal energy and from eddy to zonal available potential energy.