Miracle-dz/UniFAR-FTUs huggingface dataset:
On the permeability of unidirectional fibrous media: A parallel computational approach

The problems of viscous and inertial flows through unidirectional fibrous porous media are addressed using an entirely parallel computational approach. The pertinent partial differential equations, derived from homogenization theory, are solved by a parallel finite element method in conjunction with Monte Carlo techniques to predict the statistical permeability coefficient. A nip‐element method, which mitigates the frequent geometry‐induced numerical difficulties, while providing both accurate approximations for the permeability coefficient, and rigorous error estimates, is also presented. The seepage permeability coefficient is determined for a wide range of fiber concentration. It is shown to deviate markedly at low porosities from the behavior predicted by earlier cell models, while exhibiting generally good agreement at high, and moderate porosities with the cell models, and with the limited available experimental and analytical results. Limited but illustrative inertial flow results at moderate Reyno.
On the first Betti number of a constant negatively curved manifold

constant negatively curved n-dimensional manifolds with arbitrarily large first Betti number. In fact we show that any constant negatively curved manifold whose fundamental group is an arithmetic group commensurable with the group of units of a quadratic form admits a finite covering with first Betti number not equal to zero; in particular, the examples given by Borel at the end of [4] all admit such coverings. Previous to this a few examples were known in low dimensions (cf. Vinberg [14]) with examples up to dimension 5 in the compact case. However, his construction uses hyperbolic Coxeter groups which exist only in low dimensions. Rather than attack the problem algebraically by computing the abelianized fundamental group by group theory an approach that appears hopeless except for the above low dimensional examples, we take a geometric approach and construct explicit nonbounding codimension 1 cycles and then appeal to Poincare duality. Although these examples are of obvious geometric interest their main significance is group theoretic. The vanishing theorem of Kajdan [6] has as a consequence that the first Betti number of all compact locally irreducible, locally symmetric spaces of rank greater than 2 vanishes. This was extended by S. P. Wang [15] and Kostant [8] who show that Kajdan's criterion applies to all compact locally irreducible locally symmetric spaces except those associated with SO(n, 1) and SU(n, 1). The results of this paper show that the vanishing theorem does not hold for SO(n, 1). Whether or not it holds for SU(n, 1) remains unsolved. Our results are of interest in connection with the congruence subgroup problem. Bass, Milnor, Serre [1] show that if an arithmetic group F satisfies the congruence subgroup property that every subgroup of finite index contains a congruence subgroup, then:
Characterization of Silicon-On-Diamond chip with ionizing radiation

In this work we report on the characterization with ionizing radiation sources of a CMOS active pixel radiation sensor (RAPS03) thinned down to 40um and bonded to a slice of diamond to form a rugged Silicon-On-Diamond structure. The bonding process is based on an innovative laser technique which scans the silicon-diamond interface with a 20 ps pulsed 355 nm laser beam. The goal of the work is to demonstrate that the bonding procedure does not damage the CMOS devices, paving the way for a possible alternative to bump bonding procedures between diamond substrates and readout chips. To this purpose, the Silicon-On-Diamond device and a standard (e.g. un-thinned) RAPS03 sensor have been tested in parallel with and without ionizing radiation sources (photons, electrons) to compare their characteristics and to study their differences. The Silicon-On-Diamond device has shown to be fully functional and no differences have been found between the responses of the two sensors, within the statistical variations due to the CMOS fabrication process.
Pseudo Maximum Likelihood Estimation: Theory and Applications

Abstract : Pseudo maximum likelihood estimation easily extends to k parameter models, and is of interest in problems in which the likelihood surface is ill-behaved in higher dimensions but well-behaved in lower dimensions. Several signal plus noise or convolution models are examined which exhibit such behavior and satisfy the regularity conditions of the asymptotic theory. For specific models, a numerical comparison of asymptotic variances suggests that a psuedo maximum likelihood estimate of the signal parameter is uniformly more efficient than estimators that have been advanced by previous authors. A number of other potential applications are noted.
A Consistent Extension of Condorcet’s Election Principle

Condorcet’s principle of choosing the majority alternative whenever one exists is violated not only by Borda’s rule but by any scoring method; nevertheless the essential property of scoring functions—“consistency” of the outcome under aggregation of subgroups—is shown to be compatible with Condorcet’s principle. Moreover these two properties, suitably interpreted, together with neutrality, determine a unique rule known as Kemeny’s rule.
A shear - velocity model of the mantle

We present a new model of shear velocity structure in the mantle which is designed to fit data-sets of absolute and differential body-wave travel times, surface-wave phase velocities over a broad range of frequencies, and structure coefficients of modes of free oscillation. The model is parametrized laterally by spherical harmonics (truncated at degree 16) and by 30 natural cubic B-splines in radius. Our best model features large-amplitude structure (up to ±6% anomalies in shear velocity) in the topmost 400 km of the mantle and in the lowermost 500 km (up to ±2.5%) with most of the power in the low harmonics (l < 6). The middle of the mantle is characterized by low-amplitude anomalies with a much whiter spectrum. Our models generally show no distinctive changes in structure (in either shape or amplitude) at the 660 km discontinuity supporting the idea that an endothermic phase transition is not a barrier to large-scale flow in the mantle.
La salinidad y la irradiancia modulan el crecimiento de lacianobacteria Synechocystis minuscula en cultivos discontinuos

El crecimiento, produccion de pigmentos y de proteinas en la cianobacteria Synechocystis minuscula fue evaluado en relacion a la irradiancia (78, 156 y 238 μmol quanta m-2 s-1) y a la salinidad (0, 15, 35, 70 y 100‰) en cultivos discontinuos. Todos los experimentos por triplicado se realizaron a una concentracion de nutrientes equivalente a 8 mM NaNO3 y mantenidos en aireacion constante a 28 ± 2°C, iluminacion unilateral y fotoperiodo 12:12h. Los cultivos a 238 μmol quanta m-2 s-1 alcanzaron la mayor densidad celular y tasa de crecimiento con 271,94 ± 20,44 ×106 cel mL-1 y 0,67 ± 0,01 d-1 con diferencia significativa (P 0,05); aunque, el de carotenoides no vario con la irradiancia (P
Modeling of the Eros gravity field as an ellipsoidal harmonic expansion from the NEAR Doppler tracking data

The gravity field for asteroid 433 Eros has been determined in terms of ellipsoidal harmonic functions by processing the Doppler tracking data of the NEAR spacecraft while it was in orbit about the asteroid. Using the same set of NEAR spacecraft Doppler tracking data, comparative descriptions of the Eros gravity field are provided for both the ellipsoidal and the traditional spherical harmonic models. It is shown that for elongated bodies, like the asteroid Eros, the ellipsoidal harmonics model permits a better representation of the gravity signature than does the spherical harmonics model. Eros has a nearly uniform density but there are negative gravity anomalies near the ends of Eros and positive gravity anomalies near the Psyche crater and the Himeros depression.
Underreporting of purchases of port wine

In this paper, we develop a new approach for modelling underreported Poisson counts. The parameters of the model are estimated by Markov chain Monte Carlo simulation. An application to a real data set from a Portuguese marketing survey illustrates the fruitfulness of the approach. We find that purchases of bottles of port wine increase significantly with income class and the size of the household.
Economic design of x -control charts under Weibull shock models

In this article, a moditied version of Duncan's (1956) model for the economic design of -control charts is extended to deal with situations involving the Weibull shock model. In the traditional Duncan approach to Markovian shock models, the length of sampling intervals is kept constant. When the process-failure mechanism follows a Weibull model or some other model having an increasing hazard rate. however, it may be desirable to have the frequency of sampling increased with the age of the system. This study proposes a cost model that uses variable sampling intervals as opposed to sampling intervals of fixed length. The computational results indicate that the proposed model under variable sampling intervals provides a lower cost than those obtained by using the existing model developed by Hu (1984) for a Welbull shock model having sampling intervals of fixed length.
Approximation of the stokes Dirichlet problem in domains with cylindrical outlets

Let $\Omega \subset \RR^3$ be a domain with J cylindrical outlets to infinity and u=(v,p) be a solution of the Dirichlet problem for the Stokes system with prescibed flux Hj through the jth outlet. Let $\{\Omega_R\}$ be the set of bounded domains defined by cutting each cylindrical outlet at the distance R from its origin. The problem investigated is how u can be approximated by solutions uR of boundary problems which are defined on the bounded subdomain $\Omega_R$. On the artificial boundary $\po_R \backslash \po $ a boundary condition BuR=h has to be added. By a method similar to the Schwartz' alternating method, the asymptotic behavior (as R tends to infinity) for u-uR is investigated for different types of boundary conditions on the cut cross sections. The existence of solutions uR that are regular up to the edges is shown while using a boundary operator usually related to free boundary problems. For exponentially decaying data asymptotically precise estimates are derived for the difference u-uR; thes.
Polarized resonance Raman spectroscopy of single-wall carbon nanotubes within a polymer under strain

The ${D}^{*}$ Raman band of single-wall carbon nanotubes aligned by shear flow in a polymer matrix has been measured as a function of tensile strain. The Raman intensity varies with the optical polarization direction, an effect which is used here to assess the degree of tube alignment. The strain dependence of the Raman shift depends strongly on the nanotube orientation and the polarization direction. We show that, using polarized light, unoriented nanotubes can be used as strain sensors so that no tube alignment is necessary and the strain can be measured in all directions in a single sample.
Empirical Bayes Confidence Intervals for Selected Parameters in High-Dimensional Data

Modern statistical problems often involve a large number of populations and hence a large number of parameters that characterize these populations. It is common for scientists to use data to select the most significant populations, such as those with the largest t statistics. The scientific interest often lies in studying and making inferences regarding these parameters, called the selected parameters, corresponding to the selected populations. The current statistical practices either apply a traditional procedure assuming there were no selection—a practice that is not valid—or they use the Bonferroni-type procedure that is valid but very conservative and often noninformative. In this article, we propose valid and sharp confidence intervals that allow scientists to select parameters and to make inferences for the selected parameters based on the same data. This type of confidence interval allows the users to zero in on the most interesting selected parameters without collecting more data. The validity of confidence intervals is defined as the controlling of Bayes coverage probability so that it is no less than a nominal level uniformly over a class of prior distributions for the parameter. When a mixed model is assumed and the random effects are the key parameters, this validity criterion is exactly the frequentist criterion, since the Bayes coverage probability is identical to the frequentist coverage probability. Assuming that the observations are normally distributed with unequal and unknown variances, we select parameters with the largest t statistics. We then construct sharp empirical Bayes confidence intervals for these selected parameters, which have either a large Bayes coverage probability or a small Bayes false coverage rate uniformly for a class of priors. Our intervals, applicable to any high-dimensional data, are applied to microarray data and are shown to be better than all the alternatives. It is also anticipated that the same intervals would be valid for any selection rule. Supplementary materials for this article are available online.
Van der Pol behavior of virtual anode oscillations in the sheath around a grid in a double plasma device

Experiments are reported on oscillations that arise in a double plasma device when plasma production is restricted to the source chamber and the separating grid between the two chambers is biased negatively. The free oscillating system shows periodic pulling which is a typical behavior of driven van der Pol type oscillators. The second interacting frequency is identified to be half the ion plasma frequency at the sheath edge on the source side. With the help of particle in cell simulations the concept of virtual anode oscillations (VAO’s) as the underlying oscillation mechanism is investigated and the van der Pol character of these is revealed. When applied to the experimental conditions, the VAO-model predicts correct oscillation frequencies. It gives a new interpretation of the scaling of these with plasma density and grid bias, and is compatible with earlier findings.
Intermittency Based Unsteady Boundary Layer Transition Modeling: Implementation Into Navier-Stokes Equations

This paper presents recent advances in boundary layer research that deal with an intermittency based unsteady boundary layer transition model and its implementation into the Reynolds averaged Navier-Stokes equations (RANS). RANS equations are conditioned to include the ensemble averaged unsteady intermittency function. The unsteady boundary layer transition model is based on a universal unsteady intermittency function developed earlier. It accounts for the effects of periodic unsteady wake flow on the boundary layer transition. The transition model is the result of an inductive approach analyzing the unsteady data obtained by experiments on a curved plate at zero-streamwise pressure gradient under periodic unsteady wake flow. To validate this model, systematic experimental investigations were conducted on the suction and pressure surfaces of turbine blades that were integrated into a turbine cascade test facility, which was designed for unsteady boundary layer investigations. This model is implemented into the above mentioned conditioned RANS-equations and calculation results are presented. © 2005 ASME
Microchannel flows with superhydrophobic surfaces: Effects of Reynolds number and pattern width to channel height ratio

Superhydrophobic surfaces are widely adopted for reducing the flow resistance in microfluidic channels. The structures on the superhydrophobic surfaces may consist of longitudinal grooves, transverse grooves, posts, holes, etc. In this paper their effective slip performances are systematically studied and compared in detail through numerical simulations. The numerical results show that channel wall confinement effects have a positive influence on the effective slip length for square posts and longitudinal grooves, and a negative influence for square holes and transverse grooves. Square posts, holes, and transverse grooves all exhibit deteriorating effective slip performances at higher Reynolds numbers, while the effective slip performance of longitudinal grooves remains independent of the Reynolds number. For small pattern width to channel height ratios and at low Reynolds numbers, for low shear-free fractions, the effective slip length of square posts is equivalent of that of transverse grooves, and both.
Millimeter-Wave Observations of Saturn, Uranus, and Neptune: CO and HCN on Neptune

Saturn, Uranus, and Neptune were observed at millimeter wavelengths with the IRAM 30 m telescope. The major result is the detection of CO and HCN in Neptune's stratosphere, with respective mixing ratios of (6.5 +/- 3.5) x 10 exp -7 and (3 +/- 1.5) x 10 exp -10. CO seems to be present in Neptune's troposphere as well and to slowly decrease with altitude (scale height about 200 km). HCN is probably formed from reactions between CH3 and N, which can be supplied in sufficient amounts by escape from Triton's atmosphere. The origin of CO, however, is more problematic, because: (1) thermochemical models fail to reproduce the observed abundance by a factor of about 1000; and (2) an external source would require a very large flux of oxygen. CO appears to be at least 15 times less abundant on Uranus than on Neptune. Finally, an upper limit of 10 exp -7 for CO in Saturn's stratosphere suggests an internal origin for Saturnian CO.
Contribution of defects to electronic, structural, and thermodynamic properties of amorphous silicon

The structure of pure, nonhydrogenated amorphous silicon (a‐Si) was modified by means of ion implantation, furnace annealing, and pulsed laser annealing. Defects in a‐Si were probed by measuring the photocarrier lifetime τ at low carrier densities (1018/cm3) with subpicosecond resolution using pump‐probe reflectivity measurements. The average cross section of defect‐related midgap states for free‐carrier capture is found to be 6×10−16 cm2. In addition, the average bond‐angle distortion Δθ in a‐Si was derived from Raman spectroscopy. Annealing as‐implanted a‐Si for 1 h at T≤500 °C induces defect annihilation as well as network relaxation. In contrast, 32 ns pulsed laser heating of a‐Si just below the melting threshold leads to relaxation of Δθ without significant defect annihilation. This annealing behavior can be understood on the basis of defect diffusion kinetics. Implanting fully relaxed a‐Si with 1 MeV B+, Si+, and Xe+ up to damage levels of 0.004 displacements per atom raises the defect density witho.
Robust control of uncertain singular stochastic systems with Markovian switching via proportional–derivative state feedback

This study focuses on the problem of robust control for a class of uncertain singular stochastic Markovian jump systems via proportional-derivative state feedback controllers (PDSFCs). The uncertainties are not only in system matrices, such as state, input and derivative matrices, but also in mode transition rate matrix. New sufficient conditions for the existence of mode-dependent PDSFC are derived as linear matrix inequalities (LMIs) such that the closed-loop singular stochastic system is quadratically normal and quadratically stochastically stable (QNQSS). Especially, another PDSFC referred to be partially mode dependent is also given by a mode-dependent Lyapunov function. Numerical examples are used to show the effectiveness of the proposed methods.
Landau damping of auroral hiss

Auroral hiss is observed to propagate over distances comparable to an Earth radius from its source in the auroral oval. The role of Landau damping is investigated for upward propagating auroral hiss. By using a ray tracing code and a simplified model of the distribution function, the effect of Landau damping is calculated for auroral hiss propagation through the environment around the auroral oval. Landau damping is found to be the likely mechanism for explaining some of the one-sided auroral hiss funnels observed by Dynamics Explorer 1. It is also found that Landau damping puts a lower limit on the wavelength of auroral hiss. Poleward of the auroral oval, Landau damping is found in a typical case to limit {omega}/k{parallel} to values of 3.4 x 10{sup 4} km/s or greater, corresponding to resonance energies of 3.2 keV or greater and wavelengths of 2 km or greater. For equatorward propagation, {omega}/k{parallel} is limited to values greater than 6.8 x 10{sup 4} km/s, corresponding to resonance energies greater than 13 keV and wavelengths greater than 3 km. Independent estimates based on measured ratios of the magnetic to electric field intensity also show that {omega}/k{parallel} corresponds to resonance energies greater than 1 keV more » and wavelengths greater than 1 km. These results lead to the difficulty that upgoing electron beams sufficiently energetic to directly generate auroral hiss of the inferred wavelength are not usually observed. A partial transmission mechanism utilizing density discontinuities oblique to the magnetic field is proposed for converting auroral hiss to wavelengths long enough to avoid damping of the wave over long distances. Numerous reflections of the wave in an upwardly flared density cavity could convert waves to significantly increased wavelengths and resonance velocities. 36 refs., 12 figs., 4 tabs. « less
Runaway Fragmentation of Sungrazing Comets Observed with the Solar and Heliospheric Observatory

The observed clustering of the Solar and Heliospheric Observatory (SOHO) sungrazing comets is a product of runaway fragmentation that occurs throughout their orbits about the Sun. Since the sungrazers in tight pairs occasionally appear simultaneously in the field of view of the SOHO coronagraphs, their offsets can be used to determine their separation parameters, including the time of their parent's breakup, by applying the author's standard model for split comets. The fragmentation mode of seven sungrazer pairs is shown to differ fundamentally from that of a SOHO non-Kreutz double comet. Further support for runaway fragmentation is provided by a statistically significant argument that employs an orbit-based search for pairs among the sungrazers.
Nomogram for estimating noise propagation in urban areas

A nomogram, generated numerically, is presented for estimating sound levels generated by point noise sources in urban street complexes. The nomogram accounts for street width, distance of the receiver from the source, reflection coefficient of the building walls, and includes cases where the receiver is across one or more street intersections or is around a street corner from the source. The effect of ground reflection is included.Subject Classification: 50.80; 20.20; 28.40.