Miracle-dz/UniFAR-FTUs huggingface dataset:
Capillary effects during droplet impact on a solid surface

Impact of water droplets on a flat, solid surface was studied using both experiments and numerical simulation. Liquid–solid contact angle was varied in experiments by adding traces of a surfactant to water. Impacting droplets were photographed and liquid–solid contact diameters and contact angles were measured from photographs. A numerical solution of the Navier–Stokes equation using a modified SOLA‐VOF method was used to modeldroplet deformation. Measured values of dynamic contact angles were used as a boundary condition for the numerical model. Impacting droplets spread on the surface until liquid surface tension and viscosity overcame inertial forces, after which they recoiled off the surface. Adding a surfactant did not affect droplet shape during the initial stages of impact, but did increase maximum spread diameter and reduce recoil height. Comparison of computer generated images of impacting droplets with photographs showed that the numerical model modeled droplet shape evolution correctly. Accurate predictions were obtained for droplet contact diameter during spreading and at equilibrium. The model overpredicted droplet contact diameters during recoil. Assuming that dynamic surface tension of surfactant solutions is constant, equaling that of pure water, gave predicted droplet shapes that best agreed with experimental observations. When the contact angle was assumed constant in the model, equal to the measured equilibrium value, predictions were less accurate. A simple analytical model was developed to predict maximum droplet diameter after impact. Model predictions agreed well with experimental measurements reported in the literature. Capillary effects were shown to be negligible during droplet impact when We≫Re1/2.
Discrete integrable systems from continuous Painlevé equations through limiting procedures

Based on the relation between discrete Painleve equations of difference type and the continuous ones we derive new discrete integrable systems. The method we use is to take adequate limits of the independent variable (of the continuous equation) which appears as a parameter in the discrete system. The resulting systems are integrable and are either new (or already known) discrete Painleve equations or equations which are linearizable. For the explicit integration of some of the latter a new linearization method is introduced.
Size and structure effect on optical transitions of iron oxide nanocrystals

The heterogeneity of electronic states of transition metal oxides produces a variety of properties, which may be discerned by the measurements of their nanocrystals. The structure and optical spectra of chemically synthesized pure Fe(3)O(4), gamma-Fe(2)O(3), and alpha-Fe(2)O(3) nanocrystals of different sizes have been investigated. Three types of electronic transitions: ligand to metal charge-transfer transitions, strong magnetic coupled Fe 3, ligand field transitions, and pair excitations, occur distinctly in the optical spectra of gamma-Fe(2)O(3) and alpha-Fe(2)O(3) nanocrystals except Fe(3)O(4). The quantum size effect (for itinerant carriers) and finite size effect (for local magnetic moments) were observed in our nanocrystals, although their bulks are strong electron correlation systems. The localized to delocalized transformation of electrons occurs with time delay in the fermosecond transient absorption spectra of alpha-Fe(2)O(3) nanocrystal sol, which indicates that heteroresponse times for different transitions agree well with the size-dependent indication of the steady-state absorption bands of these iron oxides nanocrystals. These results are helpful in understanding the relationship among d-d transition, magnetic pairing, and charge-transfer in transition metal oxides.
Polarization Estimates for Abelian Varieties

In an earlier paper we showed that an abelian variety over a number field of fixed degree has a polarization whose degree is bounded by a power of its logarithmic Faltings height, provided there are only trivial endomorphisms. Here we greatly relax the endomorphism hypothesis, and we even eliminate it completely when the dimension is at most seven. Our methods ultimately go back to transcendence theory, with the asymmetric geometry of numbers as a new ingredient, together with what we call the Severi-Neron group, a variant of the Neron-Severi group.
A new technique of physical dissipation and its application to a mesoscale numerical weather prediction model

In terms of statistical physics, a fluid such as the atmosphere is a many-body system which has a vast amount of degree of freedom and thus obeys the second law of thermodynamics.In this paper, a noticeable improvement of the prognostic outputs is made by reconstructing the terms of the horizontal diffusion of MM5 according to the principles of the second law of thermodynamics; besides, the computational noise is effectively and significantly suppressed since the physical dissipative technique for reconstructing suggested in this paper is based on the physical law rather than on the computational method such as the artificial viscosity.
CFD Analysis of Flow and Heat Transfer in a Direct Transfer Preswirl System

The accuracy of computational fluid dynamics (CFD) for the prediction of flow and heat transfer in a direct transfer preswirl system is assessed through a comparison of CFD results with experimental measurements. Axisymmetric and three-dimensional (3D) sector CFD models are considered. In the 3D sector models, the preswirl nozzles or receiver holes are represented as axisymmetric slots so that steady state solutions can be assumed. A number of commonly used turbulence models are tested in three different CFD codes, which were able to capture all of the significant features of the experiments. A reasonable quantitative agreement with experimental data for static pressure, total pressure, and disk heat transfer is found for the different models, but all models gave results that differ from the experimental data in some respect. The more detailed 3D geometry did not significantly improve the comparison with experiment, which suggests deficiencies in the turbulence modeling, particularly in the complex mixing region near the preswirl nozzle jets. The predicted heat transfer near the receiver holes was also shown to be sensitive to near-wall turbulence modeling. Overall, the results are encouraging for the careful use of CFD in preswirl-system design.
Design and manufacturing of a hermetic Stirling engine

In this study, design and manufacturing of a hermetic Stirling engine having rhombic-drive mechanism were presented. In the engine, rhombic-drive mechanism was used for less vibration and piston friction. An alternator was coupled with the rhombic-drive mechanism in the engine block to convert mechanical power directly into electricity. Due to the mechanical problems, engine performance was measured without alternator unit by coupling the rhombic-drive mechanism with a dynamometer. The tests were conducted at 400 ℃ and 500 ℃ hot-end temperatures at atmospheric pressure. The surface temperature of the displacer cylinder hot end was controlled by LPG flow. The maximum torque and power obtained were 1.26 Nm at 264 r/min engine speed and 41.7 W at 350 r/min engine speed, respectively, at 500 ℃ hot-end temperature. The variation of cyclic work obtained by the experimental study was compared with the theoretical results obtained by nodal analysis.
Transient Analysis of Fluid Flow Models via Matrix Decomposition

□ We present a new approach to carry out transient analysis for Markov modulated fluid flows. The system of partial differential equations for the time-dependent distributions is transformed into a system of ordinary differential equations by Laplace transform. This system of ordinary differential equations is solved by means of decomposing its coefficient matrix into two parts, one with eigenvalues with negative real parts and the other with positive real parts. The results we obtained are equivalent, but in simpler form, to those of Ahn and Ramaswami, which are derived by probabilistic arguments.
CHEMICAL AND KINEMATICAL PROPERTIES OF BLUE STRAGGLER STARS AND HORIZONTAL BRANCH STARS IN NGC 6397

We used three sets of high-resolution spectra acquired with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to investigate the chemical and kinematical properties of a sample of 42 horizontal branch (HB) stars, 18 blue straggler stars (BSSs), and 86 main-sequence (MS) turnoff (TO) and sub-giant branch stars in the nearby globular cluster NGC 6397. We measured rotational velocities and Fe, O, and Mg abundances. All of the unevolved stars in our sample have low rotational velocites (vsin i < 10 km s−1), while the HB stars and BSSs show a broad distribution, with values ranging from 0 to ∼70 km s−1. For HB stars with T < 10,500 K there is a clear temperature–oxygen anticorrelation that can be understood if the star position along the HB is mainly determined by the He content. The hottest BSSs and HB stars (with temperatures T > 8200 K and T > 10,500 K, respectively) also show significant deviations in their iron abundance with respect to the cluster metallicity (as traced by the unevolved stars, [Fe/H] = −2.12). While similar chemical patterns have already been observed in other hot HB stars, this is the first evidence ever collected for BSSs. We interpret these abundance anomalies as due to the metal radiative levitation, occurring in stars with shallow or no convective envelopes.
Frictional and Heat Transfer Characteristics of Single-Phase Microchannel Liquid Flows

In this paper, we review the literature on flow frictional and heat transfer characteristics of single-phase liquid flows through microchannels. The work accentuates the existing discord between experimental observations of microscale transport process characteristics and the corresponding theoretical predictions on the basis of the classical paradigms. The role of microscale effects in inducing such disparity between experimental and theoretical frameworks, as indicated by various researchers, is critically discussed. Theoretical models and empirical correlations, proposed in the literature, for comprehending microscale flow and thermal characteristics are also highlighted for ready reference. In closure, aspects of microscale liquid flow and heat transfer requiring further scrutiny are identified, and possible future research directions are prescribed.
Infiltration from Trickle Irrigation Source

The two-dimensional nonlinear partial differential equation that describes the transient movement of water in an unsaturated porous medium is investigated by using the zero-order continuous linear finite element method. The governing equation is transformed logarithmically to smooth the abrupt changes in the soil-water characteristic relations. The Newton-Raphson method is used to iterate toward the “exact” solution of the original nonlinear equations. In addition, a modified implicit finite difference scheme is used to approximate the time derivatives. Predictions of the finite element model are verified with a one-dimensional example. The model is then used to investigate two-dimensional infiltration from a trickle irrigation source. The numerical results compare well with those obtained from laboratory and field experiments. The advantage of the present model is its capability to simulate water movement through very dry soil environments, which causes a steep moisture front, as well as its potential applicability in irregularly shaped flow regions, which are commonly encountered in the field and are difficult to model with finite difference or other numerical methods.
Velocity measurement of both red blood cells and plasma of in vitro blood flow using high-speed micro PIV technique

This paper describes a new high-speed micro PIV technique for measuring both red blood cell velocity and plasma velocity to investigate rheology of blood flow in microcirculation. The measurement system consists of an epi-fluorescent microscope equipped with a high-speed camera with an image intensifier and two sets of colour filters. The technique was applied to in vitro blood flow through a micro round tube of 100 µm diameter. Velocity distributions of dyed red blood cells and plasma seeded with fluorescent particles were obtained separately. The obtained velocity distributions have a high spatial resolution of 9.0 µm × 2.2 µm and high temporal resolution of 6000 Hz.
Examining deep and shallow Adriatic bora events

This note examines two Adriatic bora events recorded in TerraSAR‐X (TS‐X) images taken in the winters of 2011 (Case 1) and 2012 (Case 2). In Case 1, the TS‐X captured an image of a deep anticyclonic bora, whereas in Case 2 a shallow cyclonic bora was sampled. High‐resolution TS‐X images resolved the finer bora spatial structure to a scale of ≈1 km, which has not previously been reported in bora research. In particular, the structures in Case 2 appear to be driven by surface convective heat fluxes caused by substantial temperature differences between the relatively high sea surface temperature (SST) and the overflowing very cold air. The Weather Research and Forecasting (WRF) model simulations used to aid the analyses suggest that the very low upwind 2m temperature in Case 2 reinforced the orographic wave breaking by enhancing the cross‐mountain pressure gradient. The ensuing strong cross‐mountain flow was responsible for the appearance of secondary jets in the lee of Mount Velebit, for which the TS‐X Case 2 scene provides the first satellite‐borne evidence.
Theoretical Study on the Structure and Properties of Helium-Containing Zirconium Hydrides

Abstract The structure and properties of CaF2-type δ structure of helium-containing zirconium hydrides were investigated using density functional theory. The properties of this material vary with hydrogen and helium concentrations. Hydrogen has a significant effect on the behavior of helium. The occupied sites of He atoms strongly depend on the hydrogen concentration. The structures and formation mechanisms of helium clusters vary with hydrogen concentration at a high helium content. The embedding energies of He atoms mainly result from interactions between helium and zirconium atoms. However, H-He interactions significantly contribute to the embedding energies. Variations in lattice volume expansion and bulk modulus were also investigated.
Constant Turning Force Adaptive Control Via Sliding Mode Control Design

On elargit l'idee de la commande a mode glissant a sa forme discrete pour l'associer a l'estimation de parametres ayant un facteur d'oubli variable et pour stabiliser le systeme tournant en regard du gain variable et des regimes dynamiques non modelises tel que perturbations non lineaires, mesures imprecises etc
A statistical approach to the resolution of point sources

The Rayleigh criterion in optics states that two point sources of equal intensity are 'barely resolved' when the maximum of the diffraction pattern of one source overlaps the first minimum of the diffraction pattern of the second source. Although useful for rough comparisons of optical systems, such a criterion does not take into account the randomness in the detection process and does not tell whether sources can actually be distinguished. We present a statistical approach that addressed these issues. From quantum optics, the photon counts in the pixels are independent Poisson random variables with means that depend on the distance 2theta between the sources. Resolving the sources corresponds to testing H0: theta =0 vs Ha: theta >0, under conditions that make the information number zero at theta =0. We define resolution as the (asymptotic) power function of the likelihood ratio test rather than as a single number. The asymptotic distribution of the test statistic is derived under H0 and under contiguous alternatives. The results are illustrated by an application to a sky survey to detect binary stars using the Hubble space telescope.
The ∼150 day quasi‐periodicity in interplanetary and solar phenomena during cycle 23

An intermittent quasi‐periodicity of ∼150 days in various solar and interplanetary phenomena has been reported in earlier solar cycles. We suggest that variations in the occurrence of solar energetic particle events, interplanetary coronal mass ejections, and geomagnetic storm sudden commencements during solar cycle 23 show evidence of this quasi‐periodicity, which is also present in the sunspot number, in particular in the northern solar hemisphere. It is not, however, prominent in the interplanetary magnetic field strength.
Stellar wind during helium nova outburst

The mass ejection process during helium shell flashes on a 1.3 solar masses white dwarf which accretes pure helium matter is examined. Full cycles of helium shell flashes are followed by two different kinds of approaches: one is a time-dependent hydrostatic calculation, and the other is the construction of the sequence consisting of static models and steady state models with wind mass loss. It is found that a stellar wind occurs if the shell flash is strong enough, i.e., the mass accretion rate is lower than 1.7 x 10 to the -6th solar masses/year. The mass accumulation ratio, i.e., the ratio of the processed matter which remains after a shell flash to the initial envelope mass, has been obtained. This ratio depends strongly on the mass accretion rate. If the binary size is small enough, further mass loss occurs due to the outer critical Roche lobe overflow. This mass loss seriously affects the existing scenarios on the neutron star formation induced by the accretion. 31 refs.
Maximum likelihood estimation of bivariate circular hidden Markov models from incomplete data

In this paper, we propose a hidden Markov model for the analysis of the time series of bivariate circular observations, by assuming that the data are sampled from bivariate circular densities, whose parameters are driven by the evolution of a latent Markov chain. The model segments the data by accounting for redundancies due to correlations along time and across variables. A computationally feasible expectation maximization (EM) algorithm is provided for the maximum likelihood estimation of the model from incomplete data, by treating the missing values and the states of the latent chain as two different sources of incomplete information. Importance-sampling methods facilitate the computation of bootstrap standard errors of the estimates. The methodology is illustrated on a bivariate time series of wind and wave directions and compared with popular segmentation models for bivariate circular data, which ignore correlations across variables and/or along time.
The Composition of Nova Ejecta from Multicycle Evolution Models

Following a previous systematic study involving calculations of evolutionary sequences of nova outbursts through several cycles, for combinations of parameters—the accreting white dwarf (WD's) mass, its core temperature, and the mass transfer rate—spanning the entire parameter space, assuming CO WDs (with C and O in equal mass fractions), we now consider the detailed composition of the ejecta for the subset of models which simulated classical nova outburst. We also investigate the effect of the additional input parameter—the WD composition—on nova characteristics by calculating evolutionary sequences with pure-carbon and pure-oxygen WD progenitors. The stellar evolution code used includes an extended nuclear reactions network, OPAL opacities, and diffusion of all elements. Our main conclusions are that CO progenitors reproduce most of the observed abundances and abundance ratios, and that correlations between them, if any, are in very good agreement with observations. The WD composition is generally not reflected in the abundances of the ejecta: whereas a large fraction of the carbon is always turned into nitrogen, oxygen is in some cases unaffected and in others almost completely destroyed. Hence ejecta abundances cannot be used to deduce the WD composition. Ejected masses of pure O WD progenitors exceed those of CO progenitors, sometimes by a factor of 4. The isotopes 13C and 17O are in all cases significantly overabundant, compared to the solar composition:12C/13C varies between 0.97 and 3.8 (by number) and 16O/17O varies between 1.8 and 55;15N, however, is sometimes greatly enhanced and sometimes underabundant,14N/15N varying over a very wide range, from 2.4 to 33,000.
C*-Algebras of inverse semigroups

There are various algebras which may be associated with a discrete group G. In particular we may consider the complex group ring ℂG, the convolution Banach algebra l1(G), the enveloping C*-algebra C*(G) of l1(G), and the reduced C*-algebra determined by the completion of l1(G) under the left regular representation on l2(G). There is a substantial literature on the circle of ideas associated with the embeddings
Mechanism for shear banding in nanolayered composites

Recent studies have shown that two-phase nanocomposite materials with semicoherent interfaces exhibit enhanced strength, deformability, and radiation damage resistance. The remarkable behavior exhibited by these materials has been attributed to the atomistic structure of the bimetal interface that results in interfaces with low shear strength and hence, strong barriers for slip transmission due to dislocation core spreading along the weak interfaces. In this work, the low interfacial shear strength of Cu/Nb nanoscale multilayers dictates a new mechanism for shear banding and strain softening during micropillar compression. Our findings, supported by molecular dynamics simulations, provide insight on the design of nanocomposites with tailored interface structures and geometry to obtain a combination of high strength and deformability. High strength is derived from the ability of the interfaces to trap dislocations through relative ease of interfacial shear, while deformability can be maximized by controlli.
SOME MULTIVARIATE CHEBYSHEV INEQUALITIES WITH EXTENSIONS TO CONTINUOUS PARAMETER PROCESSES

0. Summary. In this paper we obtain some multivariate generalizations of Chebyshev's inequality, two of which are extended to continuous parameter stochastic processes. The extensions are obtained in a natural way by taking into account separability and letting the number of variables approach infinity. Particular attention is paid to the question of sharpness. To show that the bound of the inequality cannot be improved, examples are given in a number of cases that attain equality. 1. Introduction. We begin by discussing a model for the various generalizations of Chebyshev's inequality, and for a standard proof that we shall use. Examination of this proof will enable us to make some general comments concerning the problems of deriving inequalities and of proving sharpness. Let (Q, B, P) be a probability space, and let ($C, (1) be a measurable space. For each i c I, an arbitrary index set, let Bi C (t and let 5i be a class of random