Miracle-dz/UniFAR-FTUs huggingface dataset:
Grid-Orientation Effects and the Use of Orthogonal Curvilinear Coordinates in Reservoir Simulation

Grid orientation effects in reservoir simulation recently have received considerable attention. Several authors have proposed methods to reduce or to eliminate these effects. However, the proposed methods require reprograming of simulators based on standard techniques. The reprograming effort can be considerable if the numerical model is highly complex, such as in steamflood simulation. An orthogonol curvilinear coordinate system was investigated which essentially eliminates the problem of grid orientation. With no reprograming, this computing grid can be used readily in existing simulators. Such grids have been used to study pattern steamfloods and pattern waterfloods. The results are compared in detail with those obtained by using conventional Cartesian grids. Grid orientation is shown to have a more pronounced effect on the saturation fronts than oil recovery, whether in a steamflood or a waterflood. It is concluded that orthogonol curvilinear grids can be easily used to estimate pattern flood performance without program modification. (12 refs.)
Infrared study of charge delocalization induced by pressure in the La 0.75 Ca 0.25 MnO 3 manganite

We measured the pressure dependence of the room-temperature infrared absorption spectrum of the pseudocubic La 0.75 Ca 0.25 MnO 3 manganite. On increasing pressure up to 10 Gpa we observe the increase of a broad band associated with polaronic absorption, which partially screens the high-frequency phonon at high pressures. We also measured absorption spectra of the same sample as a function of temperature, and of the layered Sr 1.5 La 0.5 MnO 4 manganite as a function of pressure. The comparison between different sets of spectra clearly shows that the increase of the broad-band absorption observed in the La 0.75 Ca 0.25 MnO 3 manganite is due to a pressure-induced charge delocalization process. However, the metallic state is not achieved at room temperature, at least in the explored pressure range.
Flow Boiling Heat Transfer in Vertical Tubes Correlated by an Asymptotic Model

In flow boiling, the nucleate and convective components are superimposed by a very complex mechanism, which so far is not well understood. Two models exist in present literature, one by Chen [3] (1963), using addition of the two components with a suppression factor; and one by Shah [8] (1976), using the “greater of” the two components with a Bo-number simplified correlation. Neither model presents a satisfactory solution, as attested by the numerous methods published since then, mostly based only on regression analysis-derived correction factors. In this article a new model, based on asymptotic addition of the two boiling components, is introduced. It follows the established principles of flow boiling and converges correctly to the extremes of all parameters. Tested on the University of Karlsruhe data bank containing over 13,000 data points in vertical flow boiling, results superior to previous correlations are demonstrated.
Pulse propagation in media with frequency‐dependent Q

Recent publications have indicated that a significant dependence of the quality factor Q on frequency may occur in the interior of the earth, and thus an analysis of pulse propagation in media with Q dependent on frequency is appropriate. It is shown that a simple scaling law describes the degradation of an initially sharp pulse as it propagates in a linear viscoelastic medium in which Q has a power-law dependence on frequency. Of particular interest is the variation of the pulse rise time with path, as this parameter may be useful in estimating the Q structure of the earth.
Estimation of electric fields and currents from international magnetospheric study magnetometer data for the CDAW 6 intervals: Implications for substorm dynamics

Using a recently developed numerical scheme combined with International Magnetospheric Study magnetometer data and the Rice University Ionospheric conductivity model as input, the global distribution of the key ionospheric parameters is estimated for the Coordinated Data Analysis Workshop (CDAW) 6 intervals. These outputs include ionospheric electric fields and currents, field-aligned currents and Joule heat production rate at high latitudes, and are compiled in the form of a color movie film, which demonstrates dynamics of substorm changes of the three-dimensional current system as well as of the associated potential pattern. The present paper gives, on the basis of the space-time distribution of the key parameters, the substorm time frame that can be referenced to in terms of the substorm phases when discussing some other magnetospheric and ionospheric records. The distinction between ''substorm expansion'' and ''enhanced convection'' current systems is presented on the basis of the conventional equivalent current and potential patterns and ''true'' ionospheric currents. Although the auroral electrojets flow rather contiguously throughout the dark sector, there are several separate source regions of Joule heating from the electrojet currents. This indicates that the relative importance of the ionospheric conductivity and the electric field in the ionospheric currents varies considerably depending uponmore » latitude and local time. A possible difference in the generation mechanisms of isolated and continuous substorm activity is also discussed to some extent in the light of the two CDAW 6 intervals. « less
Which design is better? Ehrenfest urn versus biased coin

Two features are desired in designing a sequential clinical trial: randomness and balance. The former makes the ground for valid statistical inferences and the latter strengthens efficiency in inference procedures. Unfortunately randomness and balance can be in conflict with one another, and clinicians may be caught between the need for both of them. This paper raises an interesting question: can one design consistently achieve more balance than another when both designs own the same randomness? The Ehrenfest urn design is presented to allocate two treatments under a sequential clinical trial, and its balance and randomness properties are investigated. The design is compared with the biased coin design with imbalance tolerance.
Front propagation for a jump process model arising in spacial ecology

We study the propagation of a front arising as the asymptotic (macroscopic) limit of a model in spatial ecology in which the invasive species propagate by "jumps". The evolution of the order parameter marking the location of the colonized/uncolonized sites is governed by a (mesoscopic) integro-differential equation. This equation has structure similar to the classical Fisher or KPP - equation, i.e., it admits two equilibria, a stable one at $k$ and an unstable one at $0$ describing respectively the colonized and uncolonized sites. We prove that, after rescaling, the solution exhibits a sharp front separating the colonized and uncolonized regions, and we identify its (normal) velocity. In some special cases the front follows a geometric motion. We also consider the same problem in heterogeneous habitats and oscillating habitats. Our methods, which are based on the analysis of a Hamilton-Jacobi equation obtained after a change of variables, follow arguments which were already used in the study of the analogous phenomena for the Fisher/KPP - equation.
Chimneys in the starburst galaxy M82

Accepted 1999 May 27. Received 1999 April 23; in original form 1999 February 17 ABSTRA C T We present MERLIN and VLA observations at 1.4 and 5 GHz of the diffuse radio emission in the centre of M82. We detect a large expanding shell of ionized gas surrounding the brightest supernova remnant 41:95 1 57:5 with a diameter of ,100 pc and an expansion velocity of ,100 km s 21 . We observe a 50-pc-scale ‘blow-out’ from this region, in the form of a ‘cone’ of missing 5-GHz continuum emission, which appears to be an excellent example of a galactic chimney. On larger radio scales, we observe four chimney structures extending out to the north ,100‐200 pc along the minor axis. One of these features is almost certainly related to the 50-pc-scale blow-out from 41:95 1 57:5, although this is not the most prominent feature. The other features have also been traced to expulsion of material from the very centre by using an ‘unsharp masked’ image from 5-GHz VLA B-array observations, with the supernova remnant removed. We interpret these chimney features as the base of the superwind, which implies that the ejection of material into the halo does not occur smoothly over the starburst region. Instead, very localized venting of hot gas is clearly in evidence.
A Comparative Study of Flaring Loops in Active Stars

Dynamo activity in stars of different types is expected to generate magnetic fields with different characteristics. As a result, a differential study of the characteristics of magnetic loops in a broad sample of stars may yield information about dynamo systematics. In the absence of direct imaging, certain physical parameters of a stellar magnetic loop can be extracted if a flare occurs in that loop. In this paper we employ a simple nonhydrodynamic approach introduced by Haisch, to analyze a homogeneous sample of all of the flares we could identify in the EUVE DS database: a total of 134 flares that occurred on 44 stars ranging in spectral type from F to M and in luminosity class from V to III. All of the flare light curves that have been used in the present study were obtained by a single instrument (EUVE DS). For each flare, we have applied Haisch's simplified approach (HSA) in order to determine loop length, temperature, electron density, and magnetic field. For each of our target stars, a literature survey has been performed to determine quantitatively the extent to which our results are consistent with independent studies. The results obtained by HSA are found to be well supported by results obtained by other methods. Our survey suggests that, on the main sequence, short loops (with lengths ≤0.5R*) may be found in stars of all classes, while the largest loops (with lengths up to 2R*) appear to be confined to M dwarfs. Based on EUVE data, the transition from small to large loops on the main sequence appears to occur between spectral types K2 and M0. We discuss the implications of this result for dynamo theories.
Effects of Coincidence on Measurements with a Forward Scattering Spectrometer Probe

Abstract A PMS Forward Scattering Spectrometer Probe (FSSP) may fail to detect a droplet that enters the illuminated volume in coincidence with another droplet, or such a coincident pair may be assigned an erroneous size. This effect is shown to distort the droplet size spectra measured by the FSSP, and the effects can be quite important in clouds having droplet concentrations exceeding 500 cm−3. The most common coincidence error is one that arises when a droplet within the sample volume of the FSSP is rejected or sized incorrectly because of the coincident passage of another droplet outside that sample volume. Droplet spectra are measured to be too broad, and to contain too many large but too few small droplets, as a result of this effect. Some implications for past and future studies using this probe are discussed.
Gas dynamics in the impulsive phase of solar flares. II. The structure of the transition region--a diagnostic of energy transport processes

Optically thin line emissiosn formed in the solar transition region provides sensitive diagnostics of the atmospheric structure at these levels. Observations of such emission lines during the impulsive phase of solar flares show that a good correlation exists between the energy input rate (as evidenced by, for example, the hard X-ray flux) and the intensity I of a given line, and thus also the differential emission measure quantity DEM = n/sup 2/dx/d ln T, where n is the density and dx/d ln T is the temperature scale length. In this paper, we calculate and contrast the predicted temporal behavior of DEM for two models of energy transport in a flaring loop. We find that a model in which the principal mechanism of energy transport is thermal conduction cannot satisfactorily reproduce the basic observational trend noted above. On the other hand, a model in which the energy is transported throughout the flaring loop principally by collisional degradation of a beam of accelerated suprathermal electrons does adequately reproduce observed behavior. We therefore conclude that electron beam heating is a likely candidate for energy transport in the impulsive phase of flares.
Statistical studies of plasma waves and backstreaming electrons in the terrestrial electron foreshock observed by Geotail

We present statistical studies of the direction finding of 2f p radiation and the spatial distribution of plasma waves and energetic particles in the terrestrial electron foreshock observed by Geotail. First, we investigate the geometry of the electron foreshock which is assumed to be the 2f p radio source. The 2f p radio source is likely to be in the leading region of the electron foreshock where the most intense Langmuir waves are observed. The Langmuir wave activities and the population of energetic electrons gradually decrease in the region beyond 10 R E from the contact point. The decreasing rate of Langmuir wave activity is very small, about 10 -0.008 /R E . We also find that in the region around the contact point of the tangential interplanetary magnetic field (IMF) lines and the bow shock, the observed amplitude of the 2f p radiation seems to become weak. We think that it is due to the weak activities of Langmuir waves in the region close to the contact point and/or the directivity of 2f p radiation along the tangential IMF line. Next, we investigate the influence of the solar wind conditions on the activities in the electron foreshock. We confirm a positive correlation of the 2f p radio activity with the solar wind kinetic energy flux and a decrease of 2f p radio activity with decreasing IMF cone angle resulting in IMF lines tangent to the far flank of the bow shock. The 2f p radio activity is more affected by both parameters than the amplitude of Langmuir waves is affected. This suggests that the 2f p radio emissivity is very sensitive to the energy of Langmuir waves as expected from the generation process of 2f p radiation. Such high sensitivity also supports the concentration of the radio emissivity in the leading region of the electron foreshock and the limitation of the radio source extension along the magnetic field line. We also reinvestigate the comparison between the terrestrial and Venusian foreshocks. The differences between them suggest the nonsimilarity of shocks with different sizes.
Kähler metrics on elliptic surfaces

The purpose o this note is to outline a proof o the following Theorem. An elliptic surface admits a Kghler metric if and only if its first Betti number is even. Professor Kodaira raised a problem" Does every compact analytic surface with an even first Betti number admit a Kihler metric ? Our theorem solves this problem in the affirmative except the case in which the surface is a K3 surface. 1. Some cohomology groups on elliptic surfaces. Let be an elliptic surface with a section o" z/-B. We employ the notation o Kodaira [2]. Thus J, G and [ denote, respectively, the functional invariant o B, the homological invariant o B and the normal bundle of o(z/) in B. The ollowing proposition is due to Shioda [5]. Proposition 1. There exist canonical homomorphisms " HI(, G)--]*(H2(B, Z)) cH2(B, )), : HI(I, (())H(B, (), such that () () () Im a is a commensurable subgroup of ]*(H(B, Z)), fl is an isomorphism, the diagram
Eclipse Maps of the Accretion Disk in the Classical Nova V Persei

The surface brightness distribution in the accretion disk of V Per is reconstructed using a maximum entropy technique. The resulting brightness temperature gradient is much less steep than that from a standard steady state, optically thick disk for all reasonable mass accretion rates. A model including a rim which obscures part of the disk does not resolve this discrepancy. However, if the inner disk is disrupted out to R in ∼0.15-0.25R L1 (for example by a magnetic field), the brightness temperature gradient can be very close to a T b ∞R −3/4 [1−b(R in /R 1/2 ] law
Indecomposable modules: Amalgamations

The determination of criteria for amalgamations (pushouts) of indecomposable modules to be indecomposable is a well-known central problem of representation theory upon which not much progress has been made. Here we announce two results on amalgamations, and describe some of their applications to the representation theory of Artin rings. We refer the reader to [3] for the notions of modules with cores and modules with cocores, recalling that such modules are indecomposable. In the cited paper basic modules were also discussed-we mention that a module B of finite length is basic precisely when Z? /rad B is simple. Our first result is valid in any module category.
Simple Initial Value Problems and Mechanisms for Baroclinic Growth

Abstract In this paper a simple 2D linear quasigeostrophic model is used to investigate how the development of local confined cyclonic perturbations is dependent on the perturbation scale, location, and tilt in Eady-type basic states. It is found that the initial growth of the perturbation can be maximized by reducing both the vertical and horizontal scale and using a “midtropospheric” vertical location. “Potential vorticity (PV) thinking” suggests the concept of “PV unshielding” to explain this result. Adding a meridional gradient of basic-state PV lowers the vertical location of perturbations that optimally excite sustained growth. This can be understood by considering the behavior of the upward and downward propagating parts of the initial perturbation. It is found that the importance of the initial perturbation tilt is diminished for confined perturbations. It is shown that diabatic heating in a vertically confined region can lead to a perturbation that exhibits rapid growth. The findings in this pape.
A brief look at the Tsypkin criterion: from analysis to design

Tsypkin was among the first to recognize the importance of the Popov criterion and to extend it to discrete‐time systems in the form now known as the Tsypkin criterion. This paper briefly reviews the evolution of the Tsypkin criterion from its original use in absolute stability analysis to its current application as a design tool. Copyright © 2001 John Wiley & Sons, Ltd.
The Zografos–Balakrishnan-G Family of Distributions: Mathematical Properties and Applications

For any continuous baseline G distribution, Zografos and Balakrishnan (2009) and Ristić and Balakrishnan (2012) proposed novel generalized gamma-generated distributions (denoted here with the prefixes “Zografos–Balakrishnan-G” and “Ristić–Balakrishnan-G”) with an extra positive parameter. They studied some mathematical properties and presented special sub-models. Here, we provide a comprehensive treatment of general mathematical properties of Zografos–Balakrishnan-G distributions. We discuss estimation of the parameters by maximum likelihood and provide an application to a real data set. We also propose bivariate generalizations.
Dense Cores with Multiple Protostars: The Velocity Fields of L1448 IRS 3, NGC 1333 IRAS 2, and NGC 1333 IRAS 4

The embedded cores L1448 IRS 3, NGC 1333 IRAS 2, and NGC 1333 IRAS 4 are mapped in emission from the C18O, H13CO+, and N2H+ J = 1 → 0 transitions. The maps are created by combining BIMA and FCRAO observations and are tuned to resolutions of ~50'', 10'', 5'', and 3''. The higher resolution maps reveal emission structures that are considerably smaller than the characteristic core radius (~0.1 pc) identified in earlier single-dish studies. We focus our study on the kinematics of the envelope material traced by the emission lines. We find that although the FCRAO data show relatively smooth velocity gradients across the cores, the velocity fields seen with higher resolution are more random, with central velocities varying over a range of ~1 km s-1. In general, the distribution of velocities, as well as the complexity of the fields, increases with resolution. To analyze variations in the widths of the emission lines, we employ a method of gridding the datacubes that was initially developed to quantify properties of turbulent cloud models. The cores exhibit a broad range of line widths even at the smallest measurable scales. Pure thermal broadening at the prevailing envelope temperatures (T ≈ 20 K) is insufficient to produce the measured line widths; the narrowest lines must have a turbulent component at least as great as the thermal component, and for nearly all lines, the turbulent component makes the dominant contribution. Our results suggest that turbulent motions persist down to subcore scales of at least 2400 AU.
Circularly Polarized Radio Emission from an X-Ray Protostar

IRS 5, an embedded young stellar object in the nearby Corona Australis molecular cloud, was recently detected as an X-ray source with the ASCA and ROSAT satellites. We report here the detection of circularly polarized continuum emission from IRS 5 at centimeter wavelengths. Already known to be a highly variable radio source, the polarization fraction is seen to range from V/I≃10% to ≃37% on a day timescale. This demonstrates that radio emission from protostars, previously attributed in most cases to ionized thermal outflows, can sometimes arise instead from nonthermal processes, i.e., gyrosynchrotron emission from particles accelerated in situ by magnetic reconnection flares. Together with the X-ray data and indications of MeV particles in the solar nebula obtained from meteoritic materials, it contributes to the growing evidence for high-energy processes during the earliest stages of low-mass star formation.
Electrical activity of chalcogen-hydrogen defects in silicon

The interaction of hydrogen with substitutional chalcogen impurities (S, Se, or Te) is investigated by ab initio modeling. In Se-H n and Te-H n complexes (n = 1,2), protons are located at sites antibonding to nearest-neighbor silicon atoms. For sulfur, two competitive sites for S-H are found, resulting in two nearly degenerate structures. All the singly hydrogenated complexes are predicted to be shallow donors with levels lying above those of the substitutional S, Se, and Te double donors. In contrast, doubly hydrogenated chalcogen impurities are predicted to be electrically inert. A comparison of our results with experimental data suggests that the NL60 and NL61 electron-paramagnetic-resonance centers can be identified with two Se-H defects, where H is antibonded to a Si neighbor of Se.