Miracle-dz/UniFAR-FTUs huggingface dataset:
Constraints on the acceleration of anomalous cosmic rays

The recent determination of an upper limit of 0.2 pc on the distance to the source of the anomalous cosmic rays, and the implied upper limit on their age imposes a significant observational constraint on possible acceleration mechanisms. Adiabatic cooling in the expanding wind makes the constraints significantly more stringent. In the light of these constraints, the rate of second-order Fermi acceleration is much too low to play a significant role. Diffusive shock acceleration, even at the strong termination shock of the solar wind, is sufficient only if one discards the standard expression for the maximum acceleration rate based on the Bohm limit. Only diffusive acceleration at the quasi-perpendicular solar wind termination shock has a high enough acceleration rate to be the source of the anomalous component.
A generalized technique for the synthesis of 2-D state-space digital filters with minimum roundoff noise

A generalized technique has been developed for the synthesis of 2-D state-space filter structures which minimize the roundoff noise under a scaling constraint. This is based on the Fornasini-Marchesini local-state-space (LSS) model. The optimal filter structure is found using a 2-D similarity transformation characterized by a nonsingular matrix which is not block-diagonal, but general. This allows one to synthesize the optimal filter structure by solving only one optimization problem. If some constraints are imposed on the Fornasini-Marchesini LSS model and the 2-D similarity transformation matrix, it is possible to easily arrive at the results based on the Roesser LSS model. The proposed theory is therefore quite general and simple. <<ETX>>
Pollution of Lakes and Rivers

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The Nonparallel Evolution of Nonlinear Short Waves in Buoyant Boundary Layers

Buoyant boundary‐layer flows, typified by the flow over a heated flat plate, have the curious property that they can exhibit regions of “overshoot” in which the streamwise velocity exceeds its free‐stream value. A consequence of this is the streamwise velocity develops a local maximum and is inflectional in nature. It is therefore inviscidly unstable, and the fastest growing wave mode is known to be one whose wavelength is short compared to the boundary‐layer thickness. In this work we consider the nonparallel evolution of these short waves and show that they can be described in terms of the solution of a system of ordinary differential equations. Numerical and asymptotic studies enable us to explain the ultimate fate of the wave and show, depending on a key parameter which is a function of the underlying boundary layer, that two possibilities can arise. Nonparallelism may be sufficiently stabilizing so as to extinguish the linearly unstable waves or, in other cases, the mode may intensify but concentrate itself in a very thin zone surrounding the maximum in the streamwise velocity. These findings enable us to give some indication of the part these modes play in the transition to turbulence in buoyant boundary layers.
The least prime which does not split completely

Let L/K be a finite Galois extension of number fields, with group G. Let H be a subgroup of G. Under the assumption of the Generalized Riemann Hypothesis, we obtain bounds for the least prime ofK which does not split completely in L. This bound is sharper than the earlier result of Lagarias and Odlyzko. Undersome conditions, we also obtain a bound for the least prime p such that the Frobenius automorphism σρ is disjoint from H. We apply this to study effectively torsion on elliptic curves. 1991 Mathematics Subject Classification: 11R44, 11R42, 11G05, 11M41. §
Structure and dynamics of the summertime Pacific–Japan teleconnection pattern

Convective activity over the tropical western Pacific is known to influence the extratropical circulation over East Asia in the boreal summer in the form of teleconnection, called the ‘Pacific–Japan (PJ) pattern’, but its structure and dynamics have not yet been studied in depth. In this study, a composite analysis is performed for 32 monthly events of enhanced convection observed to the east of the Philippines. The composited monthly mean vorticity anomalies associated with the PJ pattern are elongated zonally with a distinct poleward tilt with height. This structure differs fundamentally from a combination of the first baroclinic mode in the tropics and the barotropic structure in midlatitudes, as has widely been accepted as a conceptual model of the PJ pattern. A wave‐activity flux points polewards only in the lower troposphere, indicating that Rossby wave teleconnection occurs primarily through a low‐level south‐westerly jet. Those tilted anomalies over the western Pacific can effectively gain kinetic energy in the exits of the mean jet streams in the upper and lower troposphere and available potential energy (APE) in the presence of the vertically sheared jets. The enhanced convection can generate APE effectively, and the associated low‐level anomalous circulation acts to increase moisture supply into the convective region while enhancing evaporation from the pre‐warmed ocean surface. It is thus hypothesized that the PJ pattern may be regarded as a dynamical mode that can be effectively excited in the zonally asymmetric baroclinic mean flow associated with the Asian summer monsoon with an efficient self‐sustaining mechanism through moist processes. Copyright © 2006 Royal Meteorological Society
The discovery of two new rapidly oscillating Ap stars, HD 92499 and HD 143487

We report the discovery of short periodic radial velocity variations in the stars HD 92499 and HD 143487. Both stars show strong magnetic fields and large overabundances of rare earth elements and belong to the class of cool chemically peculiar stars of the main sequence. They are therefore new rapidly oscillating Ap stars. Pulsations were detected from analysis of high time resolution spectra obtained with the European Southern Observatory Very Large Telescope by using a cross-correlation method for large spectral bands and from combinations of lines belonging to rare earth elements. The amplitudes of the pulsations are small and do not exceed several dozens of m s −1 with periods of around 10 min. The detection of such low amplitudes is important for the determination of which magnetic Ap stars pulsate, and which are constant, a distinction important for the understanding of the pulsation driving mechanism in these stars.
Active cancellation of acoustic pressure and particle velocity in the near field of a source

Abstract In a local active noise control system the pressure signal from a single microphone is usually taken as the error signal and cancelled by the action of a secondary source to create a zone of quiet. In this paper it is shown that the strategy of cancelling the acoustic pressure and a component of the particle velocity at a point in the near field of a secondary source considerably improves the acoustic performance of a local active noise control system with respect to the case in which only the acoustic pressure is cancelled. It is also shown that in the near field of a secondary source the active cancellation of the acoustic pressure and the particle velocity component due to only the secondary source produces similar near field zones of quiet to those obtained when the acoustic pressure and the total particle velocity component are cancelled instead. This suggests that an array of two loudspeakers having a fixed gain and phase relationship could be used as the single secondary source. The acoustic performance of a secondary source array formed by two loudspeakers is theoretically studied when the acoustic pressure and the secondary particle velocity component is cancelled at a point in its near field with and without a diffracting head present. The results show that this sort of secondary source array can produce larger near field zones of quiet than a conventional loudspeaker cancelling the acoustic pressure only. Finally, the acoustic performance of such a secondary source array in a local active noise control system with a virtual microphone arrangement that projects the zone of quiet further away from the secondary source than the position of the physical microphone is also studied. For this sort of arrangement, it will be shown that the cancellation of the pressure and the secondary particle velocity at two different points in the near field of the secondary source gives better performance than the cancellation of both acoustic magnitudes at the same field point.
The Reflection of Magneto-Thermoelastic P and SV Waves at a Solid Half Space Using Dual-Phase-Lag Model

The dual-phase-lag heat transfer model is employed to study the reflection phenomena of P and SV waves from a surface of a semi-infinite magneto-thermoelastic solid. The ratios of reflection coefficients to that of incident coefficients are obtained for P- and SV -wave cases. The results for partition of the energy for various values of the angle of incidence are computed numerically under the stress-free and rigidly fixed thermally insulated boundaries. The reflection coefficients are depending on the angle of incidence, magnetic field, phase lags and other material constants. Results show that the sum of energy ratios is unity at the interface. The results are discussed and depicted graphically.
Molecular Gas Distribution around the Supernova Remnant G40.5 0.5

The distribution of dense molecular gas around the supernova, remnant G40.5-0.5 has been investigated by radio spectroscopic observations in the CO (J = 1 - 0) transition. The molecular gas is found to extend over the entire region of G40.5-0.5. A molecular shell, with a diameter of similar to 26', coincides with the ionized gas as revealed by the cm-radio observations. This coincidence, along with the velocity discontinuity following the shell, provides direct evidence for interaction between the ionized gas and the dense molecular gas. No clear evidence for cosmic-ray acceleration can be identified from this SNR as previously suggested, due to positional uncertainty in relating the SNR shell defined by CO to the EGRET gamma-ray sources, GRO J1904+06, from the gamma-ray observations.
Primitive-Equation-Based Low-Order Models with Seasonal Cycle. Part I: Model Construction

Abstract In a continuation of previous investigations on deterministic reduced atmosphere models with compact state space representation, two main modifications are introduced. First, primitive equation dynamics is used to describe the nonlinear interactions between resolved scales. Second, the seasonal cycle in its main aspects is incorporated. Stability considerations lead to a gridpoint formulation of the basic equations in the dynamical core. A total energy metric consistent with the equations can be derived, provided surface pressure is treated as constant in time. Using this metric, a reduction in the number of degrees of freedom is achieved by a projection onto three-dimensional empirical orthogonal functions (EOFs), each of them encompassing simultaneously all prognostic variables (winds and temperature). The impact of unresolved scales and not explicitly described physical processes is incorporated via an empirical linear parameterization. The basis patterns having been determined from 3 sigma le.
Low-chirp highly linear 1.55 mu m strained-layer MQW DFB lasers for optical analog TV distribution systems

The design and realization of highly linear 1.5- mu m distributed-feedback (DFB) lasers for optical analog TV distribution systems based on dispersive single-mode fibers are reported. A simple and comprehensive model relating grating characteristics to laser chirp was developed and used for optimization of the DFB grating. The model predicts that lasers emitting at wavelengths located in the positive slope sections of the DFB-reflectivity-wavelength characteristic have higher resonance frequencies and reduced chirp. The lasers were realized by using strained-layer multiple quantum wells for high differential gain and low alpha factor, antireflection (AR) coating of one laser facet for reduction of internal photon density, and a special grating design for low spatial hole burning and chirp reduction. >
Quantitative methods for continuous particulate air monitoring

Quantitative methods for the estimation of concentrations and time integrals of concentrations of airborne radioactivity using continuous particulate air monitors are discussed. For fixed-filter and moving-filter monitors, methods based on count rate derivatives and integrals are summarized, with plots of simulation results. An approach for estimating a total-episode activity release, using moving-filter monitors, is described. Also presented is an unusual concentration measurement technique, that of an integrated-count step-advance filter (ICSAF) monitor. The instrument uses an integrated count for the concentration estimate and also advances the collection medium ("filter"), held fixed during the measurement interval, after each measurement is made. The measurement interval can be determined by either a preset count or a countrate-controlled integration time. This instrument's performance is mathematically analyzed in some detail, with graphical simulation results. The ICSAF monitor has excellent transient-following abilities and good sensitivity. Its quantitative approach does not depend on assumptions of constant concentrations of long-lived activity, nor is there a need to wait for the monitor to attain some "equilibrium" countrate, as with moving-filter monitors. This instrument would be an excellent choice for many monitoring applications.
A Generalized Solution for Approximating the Power to Detect Effects of Categorical Moderator Variables Using Multiple Regression

Investigators in numerous organization studies disciplines are concerned about the low statistical power of moderated multiple regression (MMR) to detect effects of categorical moderator variables. The authors provide a theoretical approximation to the power of MMR. The theoretical result confirms, synthesizes, and extends previous Monte Carlo research on factors that affect the power of MMR tests of categorical moderator variables and the low power of MMR in typical research situations. The authors develop and describe a computer program, which is available on the Internet, that allows researchers to approximate the power of MMR to detect the effects of categorical moderator variables given user-input information (e.g., sample size, reliability of measurement). The approximation also allows investigators to determine the effects of violating certain assumptions required for MMR. Given the typically low power of MMR, researchers are encouraged to use the computer program to approximate power while planning their research design and methodology.
MODELING AND STRESS ANALYSIS OF SMART CNTs/FIBER/POLYMER MULTISCALE COMPOSITE PLATES

Modeling and nonlinear stress analysis of piezolaminated CNTs/fiber/polymer composite (CNTFPC) plates under a combined mechanical and electrical loading are investigated in this study. The governing equations of the piezoelectric CNTFPC plates are derived based on first-order shear deformation plate theory (FSDT) and von Karman geometric nonlinearity. Halpin–Tsai equations and fiber micromechanics are used in hierarchy to predict the bulk material properties of the multiscale composite. The CNTs are assumed to be uniformly distributed and randomly oriented through the epoxy resin matrix. An analytical solution is employed to determine the large deflection response and stress analysis of the nanocomposite plates. Finally, by solving some numerical examples for simply supported plates, the effects of the applied constant voltage, plate geometry, volume fraction of fibers and weight percentage of SWCNTs and MWCNTs on the deflection and stress analyses of the piezoelectric CNTs/fiber/polymer multiscale composite plate are studied. It is shown that the deflections significantly decrease with a small percentage of CNTs. Also, it is found that the SWCNTs reinforcement produces more pronounced effect on the bending and stress of the nanocomposite plates in comparison with MWCNTs.
Laboratory studies of the charging of soft hail during ice crystal interactions

A laboratory investigation of electric charge transfer during the impact of vapour-grown ice crystals and supercooled water droplets upon a simulated soft-hailstone target has shown that the magnitude of the charge transferred to the riming surface when crystals separate from it is a function of temperature, crystal dimension, relative velocity, liquid water content, and impurity content of the water droplets and hence the impurity content of the riming target. The sign of the charge transfer depends on temperature, liquid water content and droplet and rime impurity content. In the absence of crystals, no charge transfer was detected during riming. In the absence of supercooled water droplets, crystals impacting at 10ms1 on an evaporating rime target produced a small negative charge on the rime of less than − 0.25fC per separating crystal. When the target surface grew by vapour diffusion it gained a small positive charge during such interactions. Much larger charges and completely different charge transfer behaviour was noted during riming. The target became positively charged at high liquid water contents and temperatures above a critical value, but negatively charged at lower temperatures or with lower liquid water contents. The critical sign reversal temperature at a liquid water content of 1 gm−3 was about − 20°C. At − 10°C with a liquid water content of 2gm−3, a 125 μm crystal impacting at 3ms−1 charged the target by +101C upon separation. The charge transfer increased sharply with impact speed and crystal size. Warming the positively charging rime to cause it to evaporate failed to reverse the sign of the charge transfer. Experiments with impurities showed that the sign reversal temperature increased if the droplets contained contaminants at concentrations found in cloud water. It is suggested that there are two distinct charge transfer processes during crystal interactions with an ice target, the dominant one requiring the presence of supercooled water droplets. Careful control and knowledge of the microphysical properties of the clouds used in these experimental simulations has permitted an examination of charge transfer under many of the conditions used in previous studies. The results provide an understanding of the differences and a reconciliation between some of the previously disparate findings in terms of the two distinct charge transfer regimes.
Detection and classification of indoor objects using acoustic excitations

In this paper, we show that objects of interest, like pipes and cylinders, reminiscent of guns and rifles, can be classified based on their acoustic vibration signatures. That is, if the acoustic returns are measurable, one can indeed classify objects based on the physical principle of resonance. We consider classifiers which are both training independent and those that are training dependent. The statistical classifier belongs to the former category, whereas, the neural network classifier belongs to the latter. Comparisons between the two approaches are shown to render both classifiers as suitable classifiers with small classification errors. We use the probability of correct classification as a measure of performance. We demonstrate experimentally that unique features for classification are the resonant frequencies. The measured data are obtained by exciting mechanical vibrations in pipes of different lengths and of different metals, for example, copper, aluminum, and steel, and the measuring of the acoustic returns, using a simple microphone. Autoregressive modeling is applied to the data to extract the respective object features, namely, the vibration frequencies and damping values. We consider two classification problems, 1) Classifying objects comprised of different metals, and 2) Classifying objects of the same material, but made of different lengths. It is shown that classification performance can be improved by incorporating additional features such as the damping coefficients.
Primary and secondary instabilities of the asymptotic suction boundary layer on a curved plate

The temporal growth of Görtler vortices and the associated secondary instability mechanisms are investigated numerically in the case of an asymptotic suction boundary layer on a curved plate. Highly inflectional velocity profiles are generated in both the spanwise and vertical directions. The inflectional velocity profile develops earlier in the spanwise direction. There exist two distinct modes of instability that eventually lead to the breakdown of Görtler vortices: the sinuous mode and the varicose mode. The temporal secondary instability analysis of the three-dimensional inflectional velocity profile reveals that the sinuous mode becomes unstable earlier than the varicose mode. The sinuous mode is shown to be primarily related to shear in the spanwise direction, ∂U/∂z, and the varicose mode to shear in the vertical direction, ∂U/∂y.
Combined assimilation of screen‐level observations and radar‐derived precipitation for soil moisture analysis

A methodology is proposed in order to combine information from radar precipitation with other observations (e.g. screen‐level temperature and relative humidity) in a soil analysis scheme based on an extended Kalman filter. A preliminary study is performed over the Czech Republic for one month in July 2008 using three‐hour rainfall accumulations derived from two C‐band radars and a land‐surface scheme forced by short‐range forecasts from a limited‐area model. The Jacobian matrix of the observation operator is examined to make optimal choices for the estimation of the Kalman gain matrix. It is shown that the size of the perturbation for computing Jacobian matrix elements with finite differences has to be carefully chosen, since too small values lead to unphysical negative elements whereas too large values reduce the spatial variability considerably. After a log‐transform of the precipitation field, the corresponding errors are more compatible with the Gaussian hypothesis of the Kalman filter. However, at locations where model rainfall is underestimated, positive soil moisture increments are much too low. Finally, two methods for combining the assimilation of screen‐level observations with radar precipitation are compared. A first evaluation shows more accurate soil analyses (leading to reduced screen‐level parameter forecast errors) when both sources of information are considered to correct soil moisture contents. Avenues for improving the specification of observation and model errors of the precipitation field are also discussed. Copyright © 2011 Royal Meteorological Society