Miracle-dz/UniFAR-FTUs huggingface dataset:
A Method for Estimating the Noise Level of Unstable Combustion Based on the Flame Describing Function

Practical combustion is often coupled by the system acoustics and under some conditions the process may become unstable giving rise to oscillations of finite amplitude and to discrete tone noise radiation. The objective of this investigation is to model the nonlinear features of unstable combustion to predict limit cycle amplitudes and thus get an estimation of the radiated noise level under such regimes of operation. The present study is based on an analysis derived in a companion paper (Noiray et al. (2008)) which contains a complete nonlinear description of the thermo-acoustic coupling encountered in an unconfined reaction zone layout. Theoretical predictions are successfully compared with a set of measurements. It is shown that nonlinear phenomena such as frequency shifts, triggering or hysteresis may be suitably predicted by an analytical model based on the flame describing function (FDF). The objective of the present paper is to make use of this method to investigate nonlinear acoustic-combustion dynamics in a confined geometry comprising an upstream manifold, an injector and a flame tube. The flame is identified as the main nonlinear element in the system and its response to perturbations is characterized in terms of a describing function which assumes that the gain and phase depend on the amplitude level of the input. A frequency domain analysis is then carried out by solving the dispersion relation for a range of amplitudes. This yields growth rates and eigenfrequencies, which depend on the amplitude level of perturbations impinging on the flame. The growth rates and eigenfrequencies are determined for a wide range of upstream manifold lengths while keeping equivalence ratio and mass flow rate constant. For certain values of this parameter one finds a positive growth rate for vanishingly small amplitude levels indicating that the system is linearly unstable. The growth rate then changes as the amplitude is increased and eventually vanishes for a finite amplitude indicating the existence of a limit cycle. For other values of the length, the growth rate is initially negative, becomes positive for a finite amplitude and drops to zero for a higher level. This indicates that the system is linearly stable but nonlinearly unstable. Using calculated growth rates it is effectively possible to predict amplitudes of acoustic pressure oscillations in the system when it operates on a limit cycle and thus determine the noise level generated under such conditions.
On the Nova Rate in the Galaxy

The Galactic nova rate is poorly known, with estimates in the literature ranging from as few as 11 to as many as 260 yr-1. At the lower end of the spectrum (≲50 yr-1), the predictions are based on scalings from extragalactic nova surveys, while estimates based on extrapolations of Galactic nova observations suggest rates that are significantly higher, in the range 50-100 yr-1 or more. In an attempt to reconcile this difference, the nova rate, based on Galactic nova observations, is recomputed. If the stellar mass distribution is axisymmetric about the Galactic center, a new estimate of the Galactic nova rate of ~35 ± 11 yr-1 is deduced. Although this value is marginally consistent with the highest estimates based on extragalactic surveys, the agreement is not entirely satisfactory. It is pointed out that a departure from axial symmetry, such as that caused by the presence of a Galactic bar, can potentially lower the estimated nova rate (perhaps approaching 50%) if the bar is sufficiently large, and has its long axis pointed toward the Sun. Alternatively, or perhaps in addition, it is possible that previous extragalactic surveys may have missed a significant fraction of novae (up to a factor of ~2) because of extinction internal to the galaxies. If this latter possibility can be ruled out, for example, through infrared surveys of nearby galaxies, the Galactic nova observations may provide additional support for the existence of a Galactic bar.
‘Explosive’ resonant wave interactions in a three-layer fluid flow

Cairns (1979) has recently shown how the concept of negative wave energy used in plasma physics can be exploited to obtain insights into the linear and nonlinear instability of certain parallel flows. We here analyse the linear stability and nonlinear three-wave resonance in a three-layer flow with step-wise velocity and density profiles. The results are in complete agreement with Cairns’ qualitative predictions. In particular, the existence is confirmed of an ‘explosive’ instability in which all three waves of a resonant triad grow simultaneously while total wave energy is conserved. Such nonlinear instabilities, previously undetected in fluid flows, may well be important in the ocean and atmosphere.
Source composition of cosmic rays at energies 1-1000 TeV per nucleon

Un modele est developpe pour etablir la composition de la source du rayonnement cosmique a des energies 10 12 -10 15 eV par nucleon. Le modele est base sur la theorie d'acceleration de Volk H.J. et Biermann P.L. (1988, Ap. J. Lett., 333) et sur les processus de nucleosynthese dans les etoiles pre-supernovae, i.e., les supergeantes bleues et rouges et les etoiles Wolf-Rayet.
On the pinch-off of a pendant drop of viscous fluid

The pinch-off of a drop of viscous fluid is observed using high-speed digital imaging. The behavior seen by previous authors is observed here; namely, the filament that attaches the drop to the orifice evolves into a primary thread attached to a much thinner, secondary thread by a slight bulge. Here, we observe that the lengths of the primary and secondary threads are reproducible among experiments to within 3% and 10%. The secondary thread becomes unstable as evidenced by wave-like disturbances. The actual pinch-off does not occur at the point of attachment between the secondary thread and the drop. Instead, it occurs between the disturbances on the secondary thread. After the initial pinch-off, additional breaks occur between the disturbances, resulting in several secondary satellite drops with a broad distribution of sizes. The pinch-off of the thread at the orifice is similar to that at the drop with one main difference: there is no distinct secondary thread. Instead, the primary thread necks down mon.
A Dielectric Loaded Resonator for the Measurement of the Complex Permittivity of Dielectric Substrates

A new configuration of dielectric-loaded resonator (DR), particularly versatile for the complex permittivity measurement of substrates for microwave circuits, even in the presence of back metal plates, is shown here. To test this technique in a wide interval of the values of the complex permittivity, the versatility of 3-D printing is exploited to print samples with different densities, thus artificially changing the effective permittivity in the interval (1.7–3.1) for the real part and (0.02–0.06) for the imaginary part. The designed resonator, tuned at ~12 GHz, is experimentally validated by the comparison of measurements obtained on these samples with a split ring resonator (SRR) and standard transmission/reflection waveguide methods. Then, the versatility of the designed resonator is shown in the characterization of FR4-fiberglass and Kapton polyimide samples.
Blooming plant species diversity patterns in two adjacent Costa Rican highland ecosystems

The Costa Rican Paramo is a unique ecosystem with high levels of endemism that is geographically isolated from the Andean Paramos. Paramo ecosystems occur above Montane Forests, below the permanent snow level, and their vegetation differs notably from that of adjacent Montane Forests. We compared the composition and beta diversity of blooming plant species using phenological data from functional plant groups (i.e., insect-visited, bird-visited and insect + bird-visited plants) between a Paramo and a Montane Forest site in Costa Rica and analyzed seasonal changes in blooming plant diversity between the rainy and dry seasons. Species richness was higher in the Montane Forest for all plant categories, except for insect-visited plants, which was higher in the Paramo. Beta diversity and blooming plant composition differed between both ecosystems and seasons. Differences in species richness and beta diversity between Paramo and the adjacent Montane Forest are likely the result of dispersal events that occurred during the last glacial period and subsequent isolation, as climate turned to tropical conditions after the Pleistocene, and to stressful abiotic conditions in the Paramo ecosystem that limit species establishment. Differences in blooming plant composition between both ecosystems and seasons are likely attributed to differential effects of climatic cues triggering the flowering events in each ecosystem, but phylogenetic conservatism cannot be discarded. Analyses of species composition and richness based on flowering phenology data are useful to evaluate potential floral resources for floral visitors (insects and birds) and how these resources change spatially and temporarily in endangered ecosystems such as the Paramo.
Minimax distance transform correlation filter-based target detection in FLIR imagery

This paper proposes a method to detect objects of arbitrary poses and sizes from a complex forward looking infrared (FLIR) image scene exploiting image correlation technique along with the preprocessing of the scene using a class of morphological operators. This presented automatic target recognition (ATR) algorithm consists of two steps. In the first step, the image is preprocessed, by employing morphological reconstruction operators, to remove the background as well as clutter and to intensify the presence of both low or high contrast targets. This step also involves in finding the possible candidate target regions or region of interests (ROIs) and passing those ROIs to the second step for classification. The second step exploits template-matching technique such as minimax distance transform correlation filter (MDTCF) to identify the true target from the false alarms in the pre-selected ROIs after classification. The MDTCF minimizes the average squared distance from the filtered true-class training images to a filtered reference image while maximizing the mean squared distance of the filtered false-class training images to this filtered reference image. This approach increases the separation between the false-class correlation outputs and the true-class correlation outputs. Classification is performed using the squared distance of a filtered test image to the chosen filtered reference image. The proposed technique has been tested with real life FLIR image sequences supplied by the Army Missile Command (AMCOM). Experimental results, obtained with these real FLIR image sequences, illustrating a wide variety of target and clutter variability, demonstrate the effectiveness and robustness of the proposed method.
Effects of short photoperiod on cashmere growth, hormone concentrations and hair follicle development-related gene expression in cashmere goats

ABSTRACT Shanbei White Cashmere goat is a typical goat species, the growth of cashmere is affected by photoperiod. To further investigate the effects of short photoperiod treatment on cashmere growth, hormone concentrations and hair follicle development-related gene expression in cashmere goats, twenty Shannbei white cashmere goats were selected and randomly divided into long-day photoperiod treatment group and short-day photoperiod treatment group. The results revealed the cashmere on short-day photoperiod treatment began to develop earlier, and its length and growth rate increased dramatically (P < 0.05). The short-day photoperiod treatment increased the concentration of serum Melatonin, reduced the concentration of serum prolactin, decreased the expression of estrogen receptor alpha and raised the expression of hair follicle development-related genes [catenin beta-1, Bone morphogenetic protein 2, Fibroblast growth factor 5 and platelet-derived growth factor subunit A] (P < 0.05), thereby accelerating the reconstruction of the secondary follicle, increasing the density of the secondary follicle (P < 0.05) and triggering the growth of cashmere goats. The present study provides new insights into the dynamic changes in cashmere growth, hormone concentrations and hair follicle development-related gene expression in cashmere goats under short photoperiod, and is expected to be useful for future studies on intensive feeding research.
The general solution of the three‐dimensional acoustic equation and of Maxwell’s equations in the infinite domain in terms of the asymptotic solution in the wave zone

The general solution of the three‐dimensional scalar wave equation (or acoustic equation) and of Maxwell’s equations in the infinite spatial domain is given in terms of the asymptotic forms for large times in the future and in the past, or, equivalently, in terms of the fields in the wave zone. One is therby able to obtain the exact solutions from arbitrary solutions in the wave zone. It is shown that the exact fields computed from an arbitrary wave zone solution always satisfy an initial value problem, and that, therefore, they are always physical. In contrast to earlier derivations of related results which required the use of Radon transforms and the introduction of somewhat sophisticated geometrical concepts, the derivations are simple and use only elementary properties of the Fourier transform.
Two spacecraft observations of a reconnection pulse during an auroral breakup

At 1130 UT on November 28, 1995, two spacecraft, Interball-Tail and Geotail, were in a favorable position to study the plasma sheet activity and an auroral breakup observed on the ground near the spacecraft ionospheric footpoints. Both spacecraft were near the neutral sheet, and they were nearly aligned along the magnetic meridian. During the auroral breakup observed at the equatorward half of the auroral oval (also registered as an AKR burst at Interball) both spacecraft simultaneously detected signatures of a reconnection pulse: The earthward plasma streaming and magnetic field dipolarization were observed at 12 R E at Interball, while the tailward energetic ion beam, then the tailward flow and the passage of a plasmoid were observed at 28 R E at Geotail. This pulse seem to proceed inside of the plasma sheet closed field lines, in the region of small (∼ 1nT) background magnetic field at the neutral sheet. At Interball position the onset of fast earthward ion flow, likely initiated by the reconnection pulse, was followed by other manifestations (dipolarization, enhancements of the magnetic turbulence and the energetic particle flux, the intensification of field-aligned currents). Auroral observations showed initial brightening delayed an approximately 1 min after the commencement of the reconnection pulse. The auroral intensification was not accompanied by a significant magnetic disturbance on the ground, and therefore the event can be classified as the pseudobreakup. We estimate magnetic flux transport characteristics and possible location of the onset region in the plasma sheet. We conclude that observations during this event are consistent with the initiation of an auroral breakup by some disturbance (e.g., Alfven wave) generated by the reconnection pulse that commenced in the neutral sheet at ∼15 R E distance.
The superfluid transition in helium clusters

We address cluster size effects on the λ temperature (Tλ) for the rounded-off transition for the Bose–Einstein condensation and for the onset of superfluidity in (4He)N clusters of radius R0=aN1/3, where a=3.5 A is the constituent radius. The phenomenological Ginsburg–Pitaevskii–Sobaynin theory for the order parameter of the second-order phase transition, in conjunction with the free-surface boundary condition, results in a scaling law for the cluster size dependence of Tλ, which is defined by the maximum of the specific heat and/or from the onset of the finite fraction of the superfluid density. This size scaling law (Tλ0−Tλ)/Tλ0∝R0−1/ν∝N−1/3ν, where ν (=0.67) is the critical exponent for the superfluid fraction and for the correlation length for superfluidity in the infinite bulk system, implies the depression of the finite system Tλ relative to the bulk value of Tλ0. The quantum path integral molecular dynamics simulations of Sindzingre, Ceperley, and Klein [Phys. Rev. Lett. 63, 1601 (1989)] for N=64, .
Electronic structure and magnetic properties of PbMO3 (M = Fe, Co, Ni) magnetic perovskites: An ab initio study

We present the electronic, magnetic and structural properties of the magnetic transition metal oxides PbMO3 (M = Fe, Co, Ni) in cubic perovskite structure. The calculations are based on the density functional theory (DFT) within plane-wave pseudopotential method and local spin density approximation (LSDA) of the exchange-correlation functional. On-site Coulomb interaction is also included in calculations (LSDA+U). The systems are considered in ferromagnetic (FM) and G-type antiferromagnetic (G-AFM) order. FM structures are energetically more favored than G-AFM and than non-magnetic states for all the systems studied. The spin-polarized electronic band structures show that all the structures have metallic property in FM order without Hubbard-U interaction (Ueff = 0). However, the inclusion of on-site Coulomb interaction (Ueff = 7 eV) opens a semiconducting gap for majority spin channel of PbFeO3 and of PbNiO3 resulting in a half-metallic character. PbCoO3 system remains as metallic with LSDA+U scheme. Bonding features of all structures are largely determined by the hybridizations between O–p and d-states of transition metal atoms. The partial magnetic moment of Fe atom in PbFeO3 is enhanced by inclusion of Hubbard-U interaction (2.55 μB ⇒ 3.78 μB). Total magnetic moments of half-metallic PbFeO3 and of PbNiO3 compounds are very close to integer values.
Obstructive Sleep Apnea Patients With Atrial Arrhythmias Suffer From Prolonged Recovery From Desaturations

Objective: We aimed to investigate how acute and long-term effects of atrial arrhythmias affect the desaturation severity and characteristics determined from the oxygen saturation signal in obstructive sleep apnea (OSA) patients. Methods: 520 suspected OSA patients were included in retrospective analyses. Eight desaturation area and slope parameters were calculated from blood oxygen saturation signals recorded during polysomnographic recordings. Patients were grouped based on whether they had previously diagnosed atrial arrhythmia (i.e., atrial fibrillation (AFib) or atrial flutter) or not. Furthermore, patients with a previous atrial arrhythmia diagnosis were sub-grouped based on whether they had continuous AFib or sinus rhythm during the polysomnographic recordings. Empirical cumulative distribution functions and linear mixed models were utilized to investigate the connection between diagnosed atrial arrhythmia and the desaturation characteristics. Results: Patients with previous atrial arrhythmia diagnosis had greater desaturation recovery area when the 100% oxygen saturation baseline reference was considered (β = 0.150--0.127, p ≤ 0.039) and more gradual recovery slopes (β = −0.181 to −0.199, p < 0.004) than patients without a previous atrial arrhythmia diagnosis. Furthermore, patients with AFib had more gradual oxygen saturation fall and recovery slopes than patients with sinus rhythm. Conclusion: Desaturation recovery characteristics in the oxygen saturation signal contains essential information about the cardiovascular response to hypoxemic periods. Significance: More comprehensive consideration of the desaturation recovery section could provide more detailed information about OSA severity, for example when developing new diagnostic parameters.
Plasma turbulence imaging using high-power laser Thomson scattering

The two-dimensional (2D) structure of plasma density turbulence in a magnetically confined plasma can potentially be measured using a Thomson scattering system made from components of the Nova laser of Lawrence Livermore National Laboratory. For a plasma such as the National Spherical Torus Experiment at the Princeton Plasma Physics Laboratory, the laser would form an ≈10-cm-wide plane sheet beam passing vertically through the chamber across the magnetic field. The scattered light would be imaged by a charge coupled device camera viewing along the direction of the magnetic field. The laser energy required to make 2D images of density turbulence is in the range 1–3 kJ, which can potentially be obtained from a set of frequency-doubled Nd:glass amplifiers with diameters in the range of 208–315 mm. A laser pulse width of ⩽100 ns would be short enough to capture the highest frequency components of the expected density fluctuations.
Diachronic Study on the Derivation of There in There-be Construction

In the circle of linguistics, numerous attempts have been made to explore there-be construction in the fields of syntax, semantics, and pragmatics, but there is little touching on the derivation of the word there. In consequence, herein the focus and effort are put on the issues of there, especially the derivation of there. It begins with the exploration of historical sources touching upon there and all the analyses are based on the historical study on there constructions. In the historical study, it is demonstrated that there-be construction derivates from archaic Then-V pattern and PP-V pattern by analogy when the subject is obligatory in the clause.
Characterization and modeling of the serum concentration of osteocalcin in breeding sows and its interaction with biochemical indicators: A review

Adipose, muscle, and bone tissues modulate the metabolic state of mammals. However, the role of bone tissue as a metabolic state modulator in sows has not been studied. During the gestation–lactation transition, sows undergo metabolic adaptations to meet their nutritional requirements. Among these adaptations, bone remodeling is characterized by the synthesis and inhibition of hormones that participate, together with hormones from other tissues, in fetal development and lactogenesis. Osteocalcin is a hormone synthesized by the bone tissue which has been associated in different biological models with the improvement of the metabolic state. However, in sows, published results on the concentration of osteocalcin are scarce, and its concentration throughout the reproductive cycle is unknown. Therefore, with information from published trials on the measurement of serum osteocalcin, a structured review was conducted under the following objectives: (1) to review the promising effect of osteocalcin on energy metabolism in different models and (2) to characterize and model the serum concentrations of osteocalcin during the reproductive cycle of the sow. According to the review, the results obtained for humans and other animal models suggest that osteocalcin regulates energy metabolism, which has been associated with the need for integrated metabolism to cope with the metabolic demand during gestation and lactation in mammals. If these effects are significant in the sow, current recommendations for dietary balance should be reconsidered, particularly during the gestation–lactation transition period. According to mathematical modeling, it was the period in which the lowest concentration of osteocalcin was found.